atlanta geological society newsletteratlantageologicalsociety.org/wp-content/uploads/... · algal...

Atlanta Geological Society Newsletter

ODDS AND ENDS Dear AGS members, BOOM! And like that winter is over and I have a yard full of daffodils. Checking today and it was almost 80˚, 20˚ above average. In today’s news is the report that at least 24 cities recorded their hottest February temperature on record on Wednesday. And I saw that the Artic recently has been some 45˚ above average, above freezing in some places. Given who I work for, I’ll say that it is my personal observation that climate is changing. I know better than to say that one event makes a trend, but this is starting to add up that only the most skeptical among us can deny something isn’t changing the weather. Geology moves so slowly but what could these changes mean? Would you get more weathering from more times through the freeze/thaw cycle? Would the elevated temperature overall increase the overall thermodynamics of soil formation? One would assume that permafrost would be affected in coverage but none of us are involved in research in that world. It does make me appreciate the work of Dr. Kim Cobb at GT who spoke to us in 2016. Speaking of speakers, I enjoyed Dr. Tony Martin’s talk last month on trace fossils, specifically trace fossils. By definition, Ichnology. Which reminds me of a podcast I found all about ‘Ologies’. The first episode was about a vulcanologist. Give a listen. https://www.alieward.com/ologies/ Hope to see you Tuesday! Ben Bentkowski, President

February Meeting

Join us Tuesday, February 27, 2018 at the Fernbank Museum of Natural History, 760

Clifton Road NE, Atlanta GA. The meeting/dinner starts at 6:30 pm and the

meeting starts approximately 7 p.m. This month’s presentation is: “Hydrologic

Drivers of Harmful Algal Blooms in two Piedmont Reservoirs” presented by

Ms. Abigail Knapp. Please find more information about Abigail’s bio on Page 2

of the newsletter.

Please come out, enjoy a bite to eat, the camaraderie, an interesting presentation and perhaps some discussion on the importance of accurate mineral characterization. Also,

the differences that can exist between mineralogical, industrial and regulatory

definitions for minerals.

www.atlantageologicalsociety.org

facebook.com/Atlanta-Geological-Society

AGS February 2018

This Month’s Atlanta Geological Society Speaker

Hydrologic Drivers of Harmful Algal Blooms in two Piedmont Reservoirs

Ms. Abigail Knapp is a 2nd year graduate student in her last semester at the University of Georgia. She is researching in the Water Resources and Remote Sensing Lab in the Geology Department. After graduation, Abigail will seek work in the limnological and water resources science within a state agency. Other than hydrology, she enjoys ignimbrite petrography and collecting feldspars.

Abstract: Reservoirs are central to freshwater resource management in the Southeast, but are often at risk of eutrophication and recurring harmful algal blooms. While the extreme hydrologic events such as flooding and drought are though to control the onset and success of these blooms, the spatiotemporal dynamics are yet to be fully understood. This study looked at the systems of blooms, storms, and drought in Lake Allatoona and Lake Lanier using historical datasets and satellite remote sensing, and modeled the relationships in time and space. Knapp, Abigail S., Milewski, Adam M., and Rotz, Rachel R., 2017. Temporal Relationship between

Drought-Precipitation Patterns and the Onset, Duration, and Severity of Freshwater Harmful Algal Blooms in Lake Allatoona, GA. Geological Society of America Southeastern Section, accepted.

Saenger, Abigail, 2013. Melt Inclusion Study of the East Fork Rhyolite Member of the Valles Caldera,

New Mexico. Center for Undergraduate Research Opportunities Abstracts with Program, p. 92. Saenger, Abigail L., and Swanson, Samuel E., 2012. Mineralogy of Primary Phosphate Minerals in Li

Pegmatites of the Kings Mountain District, North Carolina. Geological Society of America Southeastern Section Abstracts with Program v 44.

Hogan, Davison L., Tabor, Beth M., Harper, John. R., North, Brandon K., Vanhazebroeck, Ethan, Lawler, Jesse D., Saenger, Abigail L., Taylor, Nicholas J., Fleisher, Christopher J., and Swanson, Samuel E., 2012. Comparison of mineralogy of Li Pegmatites in the Kings Mountain District, North Carolina. Geological Society of America Southeastern Section Abstracts with Program v 44.

AGS February 2018

Global Patterns of Nitrate Storage in The Unsaturated Zone

The unsaturated (vadose) zone between the base of soils and the water table can be an important store of nitrate. Water moves slowly downward through the unsaturated zone and so a large store of nitrate can accumulate if this water contains nitrate derived from surface sources such as fertilizer. Release of this store can affect ground- and surface water quality for decades and it can continue for a long time after changes in farming practice that reduce nitrate leaching.

To better understand the extent of the problem, the British Geological Survey has made the first global-scale quantification of nitrate stored in the vadose zone between 1900 and 2000.

Increases in nitrate storage in the unsaturated zone though space and time To estimate nitrate stored in the unsaturated zone, we linked mathematical models of nitrate leaching from the base of the soil zone with estimates of groundwater recharge, unsaturated-zone porosity and the depth to groundwater.

Our modelling showed a substantial continuous increase in nitrate stored in the unsaturated zone over the last century. The peak nitrate storage in 2000 was estimated to be up to 1814 teragrams (Tg) of nitrogen (N). This is equivalent to up to 200 per cent of the inorganic N stored in soils. Spatially, the unsaturated-zone nitrate storage is greatest in North America, China and central and eastern Europe, where the depth to water table is large and there is an extensive history of agricultural fertilizer use.

Nitrate storage patterns To better understand trends in nitrate storage, we grouped the nitrate storage responses for river catchments across the globe. The groups show clear differences and trends, with a distinct split between developed (USA, Europe) and developing (Africa, East Asia) countries. In the developed group, current nitrate leaching into the unsaturated zone is decreasing, as a result of improved regulation and farming practice. In contrast, in the developing countries nitrate leaching shows continuous increases associated with rapid, early development and growing intensification of fertilized agriculture.

Conceptual model of nitrate stored in the unsaturated zone.

AGS February 2018

Global Patterns of Nitrate Storage in The Unsaturated Zone (Continued)

Implications for environmental policy The large store of nitrate in the unsaturated zone means that the use of soil-nitrate leaching estimates alone as an indicator of nitrate pollution is likely to be inappropriate. The distribution of unsaturated-zone nitrate storage can give policy makers and decision makers a first global indication of where this store may be significant and where delays in improvements in groundwater and surface water quality can be expected. This is important for assessing the effectiveness of nitrate management measures and timescales for achieving environmental objectives.

The different nitrate storage characteristics observed highlight the need for different management strategies to tackle nitrate pollution across developing and developed countries. However, in both cases, it is essential that catchment retention processes, such as unsaturated-zone storage, are considered. Other temporary stores of nitrate such as storage in soil organic matter and in riparian zones also need to be quantified if fully integrated pollution-management strategies are to be developed.

Read more about this article at: http://www.bgs.ac.uk/research/groundwater/quality/nitrate/global‐unsaturated‐zone.html

Vast Bioenergy Plantations Could Suck up Carbon and Stave Off Climate Change. They Would Also Radically Reshape the Planet.

On a sunny day this past October, three dozen people file into a modest, mint-green classroom at Montana State University (MSU) in Bozeman to glimpse a vision of the future. Some are scientists, but most are people with some connection to the land: extension agents who work with farmers, and environmentalists representing organizations such as The Nature Conservancy. They all know that climate change will reshape the region in the coming decades, but that's not what they've come to discuss. They are here to talk about the equally profound impacts of trying to stop it.

Paul Stoy, an ecologist at MSU, paces in front of whiteboards in a powder blue shirt and jeans as he describes how a landscape already dominated by agriculture could be transformed yet again by a different green revolution: vast plantations of crops, sown to sop up carbon dioxide (CO2) from the sky. “We have this new energy economy that's necessary to avoid dangerous climate change, but how is that going to look on the

Global increase in nitrate stored in the unsaturated zone. Spatial distribution of nitrate in the unsaturated zone.

AGS February 2018


(Continued)

ground?” he asks.

In 2015, the Paris climate agreement established a goal of limiting global warming to “well below” 2°C. In the most recent report of the Intergovernmental Panel on Climate Change, researchers surveyed possible road maps for reaching that goal and found something unsettling. In most model scenarios, simply cutting emissions isn't enough. To limit warming, humanity also needs negative emissions technologies (NETs) that, by the end of the century, would remove more CO2 from the atmosphere than humans emit. The technologies would buy time for society to rein in carbon emissions, says Naomi Vaughan, a climate change scientist at the University of East Anglia in Norwich, U.K. “They allow you to emit more CO2 and take it back at a later date.”

Whether that's doable is another question. Some NETs amount to giant air-purifying machines, and many remain more fiction than fact. Few operate at commercial scales today, and some researchers fear they offer policymakers a dangerous excuse to drag their feet on climate action in the hopes that future inventions will clean up the mess. “In many ways, we're saying we expect a bit of magic to occur,” says Chris Field, a climate scientist at Stanford University in Palo Alto, California, who instead favors drastic emissions reductions. Others say we no longer have a choice—that we have dallied too long to meet the Paris targets solely by tightening our belts. “We probably need aggressive and immediate mitigation, plus some negative emissions,” says Pete Smith, a soil scientist and bioenergy expert at the University of Aberdeen in the United Kingdom.

One particular technology has quietly risen to prominence—thanks to global models—and it is the one on tap in Bozeman. The idea is to cultivate fast-growing grasses and trees to suck CO2 out of the atmosphere and then burn them at power plants to generate energy. But instead of being released back into the atmosphere in the exhaust, the crops' carbon would be captured and pumped underground. The technique is known as bioenergy

AGS February 2018


(Continued)

with carbon capture and storage, or—among climate wonks—simply as BECCS.

Few at the Bozeman meeting have heard of BECCS, and most are suspicious; it sounds like a far-fetched scheme that might disrupt the world as they know it. During a break, Martha Kauffman, a regional director for the World Wildlife Fund in Bozeman, wonders whether BECCS might encroach on lands used to graze cattle. In grasslands like this, she says, “It's the primary way people make a livelihood while keeping habitat.”

She's not the only one who's wary. Although BECCS is relatively cheap and theoretically feasible, the sheer scale at which it operates in the models alarms many researchers. In some future scenarios, BECCS would remove up to a trillion tons of CO2 from the air by the end of the century—about half of what humans have emitted since the start of the Industrial Revolution—and it would supply a third of the globe's energy needs. Such a feat would require growing bioenergy crops over an area at least as large as India and possibly as big as Australia—half as much land as humans already farm. “It is easy to say, ‘Hey, globally, how about we just do this, guys?’” Stoy says to the room. “But what is actually going to happen?”

Stoy and a team of researchers hope to provide answers gleaned from the Upper Missouri River Basin, which includes parts of Montana, Wyoming, and the Dakotas. They have just launched a $6 million effort to study the impacts of BECCS on such things as local food production, water use, and biodiversity. In other words, what happens when you pluck BECCS from the idealized realm of global carbon accounting and plop it into a real place, with patchwork lands, messy politics, and interconnected ecological, physical, and economic systems? “Nobody's evaluated what these assumptions mean at the regional scale,” says Ben Poulter, a carbon cycle modeler at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a leader of the project. “It's really important that we try to figure that out.” After all, the future of climate policy—and possibly the planet—hangs on the answer.

IN EARLY FALL, Montana's Gallatin Valley is a study in gold. Flame-leafed cottonwoods burn like candles along the narrow country lanes, and the hills wear a mantle of thick, honey-colored grass. Dale Flikkema, a third-generation farmer, almost blends into the landscape. With sandy hair and a sun-bronzed face, he surveys his field on the outskirts of Bozeman. Beneath the yellow canola stubble at his feet, stray seeds have sprouted into tiny sprigs of green. “These spilled from my combine,” he says, kneeling to inspect them. Today, this food-grade canola—which can also be used to make biodiesel—is the closest thing to a bioenergy crop being grown in Montana. But under the models' BECCS scenarios, farmers like Flikkema would see big changes.

As BECCS is usually conceived, bioenergy crops would be grown on unused agricultural land. In the Upper Missouri River Basin, that could mean conscripting fields set aside as part of the U.S. Department of Agriculture's Conservation Reserve Program (CRP), which pays farmers to leave fields fallow for environmental benefits. Given the right incentives, farmers could pull these lands back into production—something that has already happened in the region as demand for corn and soy have grown. “Farmers are no different than anyone else. We are profit-driven,” Flikkema says.

Here in Montana, farmers' bioenergy crop options are limited for now. Only a few adventurous growers like Flikkema are experimenting with canola and other oilseeds. As the climate warms, however, the entire region is projected to become more hospitable to plants such as switchgrass, a towering grass called Miscanthus, and vigorous poplar trees. These “second-generation” bioenergy crops are often seen as the future of bioenergy

AGS February 2018


(Continued)

because, as perennials, they are far better at storing carbon in the soil and in their biomass than traditional fuel crops like corn and canola. They can also grow on marginal lands with less fertilizer and water, making it less likely they will compete with food production.

Once harvested, these crops would get ferried by truck or train to power plants and other industrial facilities where, along with waste from food crops and timber harvests, they would be burned for heat or electricity, or converted to ethanol and other liquid biofuels. The CO2 given off by either process would be siphoned off and compressed into a fluid. That concentrated CO2 would be piped away and pumped underground into porous rock formations, which abound in the Upper Missouri River Basin. Because of its long history of oil and gas production, the area is perforated with wells. Lee Spangler, an MSU chemist involved with the project, is studying whether any of the 11,000 wells near the Colstrip Power Plant in eastern Montana, for instance, would be good conduits for injecting carbon underground. The final result? Carbon is transferred from the atmosphere back to the geologic reservoirs from which it came.

BECCS isn't the only route to negative emissions. But alternative approaches, like capturing CO2 directly from the air using chemical reactions or absorbing it with ground-up minerals added to soils, are just beginning to see their first real-world tests (see graphic, p. 734). These techniques could one day surpass BECCS, but for now, they cost more, Vaughan says. “BECCS will pay for itself to some extent because it generates energy.”

BECCS isn't a total technological reach, either; its two components—bioenergy and CCS—are already happening to some degree today. Power plants around the world are burning biomass for energy, either alone or together with fossil fuels. CCS has been slow to take off, but dozens of projects are underway, including numerous pilots in the Great Plains, many of which pump CO2 from fossil fuel power plants into dwindling wells to drive out residual oil. One of the longest-running operations is in the North Sea, where the Norwegian oil company Statoil has been separating CO2 from natural gas and sequestering it underground for more than 2 decades.

To put the brakes on climate change, however, these tools would have to be deployed on an entirely unproven scale.

A bioenergy field trial in Wisconsin is evaluating how switchgrass, Miscanthus, corn stover, poplar trees, and native prairie grasses stack up against each other.

AGS February 2018


(Continued)

AS FLIKKEMA DRIVES BACK from his canola field, his blue pickup rumbles across a narrow irrigation canal. “Our lifeblood,” he remarks. Water is a scarce commodity in Montana, and irrigated crops are by far the biggest consumer of it, although lately, there is growing demand from the oil and gas industry. Poulter says BECCS could divert precious water that would otherwise support crops or native ecosystems. “Water already defines land use in the West and is bound to be an issue,” Poulter says. According to one global assessment, using switchgrass to sequester 3.7 billion tons of CO2 would use almost as much water as is in Lake Michigan, and many scenarios require that much carbon or more to be removed each year. (The same study concluded that BECCS would eat up the equivalent of a quarter of the world's annual nitrogen fertilizer production, too.)

Critics are also concerned about BECCS's big footprint. “It worries me that the landscape already has to produce food, and now we will rely on it to produce energy, too,” says Meghann Jarchow, an ecologist at the University of South Dakota in Vermillion. The prairies of the Upper Missouri River Basin are home to iconic species such as the prairie dog and provide critical habitat for many grassland birds, but they are losing ground to food production and, increasingly, to bioenergy crops. BECCS could make the problem worse.

Some BECCS advocates disagree, saying that if it were done right, it could be a boon for the environment. Today, much of the abandoned farmland where second-generation bioenergy crops could grow is degraded and dominated by invasive plants, says Phil Robertson, an ecologist at Michigan State University's W. K. Kellogg Biological Station in Hickory Corners. “Generally, it doesn't have high conservation value,” he says. But field studies in the Midwest suggest that planting native switchgrass, with a few other plant species thrown in for good measure, could actually help restore the grassland ecosystems that once covered the middle of the continent. With smart policies in place, Robertson envisions a world in which farmers could turn the profits from bioenergy harvests back into restoring more land. “I think it could underwrite conservation,” he says.

Worldwide, there is no shortage of farmland that's been abandoned because of low productivity or fickle markets. A conservative estimate by Field and his colleagues suggests an area at least the size of India is available globally, and others suggest there is several times that—plenty to support a robust BECCS industry. But more farmland may also be needed to feed a global population that could peak between 8 billion and 12 billion people sometime this century. Most model scenarios make a big assumption: that rising agricultural productivity and vegetable-based diets will limit the need for new farmland. But the real world, where demand is growing for meat and dairy products that require lots of land, could be a different story.

Researchers like Vaughan worry that without strong regulations, surging demand for bioenergy could displace food crops—causing prices to rise—or push farmers into uncultivated lands. Past experiments with biofuels also brought new land into cultivation, which not only threatened biodiversity, but also undermined some of the climate benefits of bioenergy in the first place. That's because cutting down trees to make new farmland, for example, releases far more carbon into the atmosphere than bioenergy crops can sequester. “That can wipe out any future benefit for years to come,” Robertson says. Even planting crops on abandoned fields, like CRP land, can create a sizable carbon debt if soil is tilled, which releases CO2.

Then there are the economics. Getting farmers to grow specialized crops will require proper incentives. “The markets will have to come for guys to change,” Flikkema says. Farmers here didn't start growing soy until a local elevator started buying it, he says. To establish BECCS in the Upper Missouri River Basin and worldwide, governments will have to set a price on carbon—through something like a tax or a cap-and-trade program—and

AGS February 2018


(Continued)

use the proceeds to incentivize individual farmers to grow bioenergy crops on their land.

These headwinds lead many researchers to conclude that the amount of BECCS in models is unrealistic. “Nobody is actually saying it's coherent,” says David Keith, an engineer and climate policy expert at Harvard University who wrote some of the early papers on BECCS. Keith, who has since helped launch a direct air capture company, says the modelers seized on BECCS because it was one of the few ways to simulate negative emissions—and negative emissions were one of the few ways to try to keep warming below 2°C.

Modelers stress that scenarios are not projections of the future, and shouldn't be treated as such. “They're what-if pathways,” says Katherine Calvin of the Pacific Northwest National Laboratory in College Park, Maryland. But Keith says that hasn't stopped BECCS from attracting undue attention. The result, he says, is a perilous mismatch between models and reality that presents a “moral hazard” by committing future generations to technological solutions that may not work in the end.

It's an accusation that has often been lobbed at Keith's main area of study: geoengineering Earth's climate to counteract warming by, for instance, injecting particles into the sky to reflect sunlight. Keith is miffed that many policymakers see geoengineering as a “completely crazy, risky, way-out-there thing we shouldn't talk about” while remaining sanguine about massive reliance on negative emissions. “If moral hazard is sweeping the problem under the rug, and pushing more of it to future generations, and making it look like you are meeting the targets when you are not,” he says, “that is for sure what's happening with BECCS now.”

BY THE END OF THE DAYLONG MEETING in Bozeman, Stoy and Poulter have made progress on their first goal: spreading the word about this arcane acronym, BECCS. But most of the work, and the loftier questions, lie ahead. Stoy raised one earlier that day: “How can we not just run roughshod over the entire northern Great Plains?” Or, by extension, the world?

To that end, the team will use detailed physical models to construct a handful of scenarios for the region. At one end of the spectrum is a world that goes long on BECCS, with farmers using CRP land, and maybe even existing cropland or virgin prairie, for bioenergy. At the other end is a future that sacrifices some amount of carbon storage for the benefit of conservation, food production, and other local values. In this future, there would be only a small amount of BECCS. Instead, most carbon would be stored by protecting forests, adopting no-till farming practices, and taking other climate-friendly approaches to land stewardship. A recent study found that such actions, carried out on a global scale, could provide a cheap and easy way to accomplish a third of the CO2 mitigation needed in the next decade to be on track to meet the Paris goals.

The team doesn't know which of its scenarios will come to pass. But it does know that, as atmospheric CO2 continues to rise and the world warms apace, time is running out for countries to decide whether to count on negative emissions. If we are going to rely on technologies like BECCS in the future, we need to start ramping them up now, says Sabine Fuss, an economist at the Mercator Research Institute on Global Commons and Climate Change in Berlin. “It's a little bit dangerous if it's conceived as something that you just switch on.” So far, only one commercial plant is doing anything close to BECCS—a bioethanol refinery in Decatur, Illinois, that each year sequesters 1 million tons of CO2 released from fermenting corn.

The researchers repeatedly try to impress this upon the audience in Bozeman—that despite its many risks and

AGS February 2018


(Continued)

drawbacks, they should take BECCS seriously. Some amount of BECCS, or some other carbon-eating technology, is probably coming. “Even though it's very fantastical at this point to think it could happen,” Poulter says, “it's one of only a few remaining options we have to deal with this problem.”

BECCS would bring sweeping changes to the region, but then again, so will climate change. Indeed, among all the options the team will consider in its study, there is one it won't include: allowing the Upper Missouri River Basin to stay the same.

Read more about this article at: http://science.sciencemag.org/content/359/6377/733.full

15 Volcanoes. 6 Scientists. 1 Mission.

This is the Trail by Fire.

The atmosphere that allows our planet to sustain life formed from gases emitted by volcanoes early in Earth's history. These volatile elements are constantly recycled back into the deep Earth at subduction zones, where tectonic plates sink into the mantle. During this process the sinking plate is subjected to increasing heat and pressure, and releases volatiles. These volatiles, once added to the mantle, induce melting and fuel volcanic

explosions, completing the cycle. While this depiction of the earth’s giant recycling factory is well established conceptually, we do not know how efficient it is. We can estimate how much goes in, but have little idea what proportion is released back to the atmosphere, and what proportion remains trapped at depth. This question is crucial if we want to understand how our atmosphere formed and our planet became able to sustain life. In the

present-day context, characterizing how much gas comes out of the giant recycling factory is also key to understanding volcanic effects on climate, volcanic emissions being significant - but poorly constrained -

parameters in current climate models.

Our team of early career volcanologists is conducting expeditions to the South American Andes. Our objective is to provide the first accurate and large-scale estimate of the flux of volatile species (H2O, H2, CO2, CO, SO2, H2S, HCl, HF, and more) emitted by volcanoes of the Nazca subduction zone. The journey is taking us across half a continent, from the giant volcanoes of Ecuador through the altiplanoes of Peru and to the Southern tip of

Chile, traveling on some of the Earth’s highest roads, and climbing some of the Earth's tallest volcanoes.

NEWS TEAM GEAR

Read more about this article at: http://www.trailbyfire.org/

AGS February 2018

Fluorescent Dyes: A New Weapon for Conquering DNAPL Characterization

Introduction It is common knowledge that dense nonaqueous phase liquid (DNAPL) source zones represent one of the most significant challenges in the remediation industry. Where they are present, they create contaminant plumes in groundwater that can persist for hundreds of years unless they are effectively removed or controlled. Unfortunately, the nature and extent of DNAPL distribution is often extremely complicated and difficult to accurately characterize.

Failure to accurately characterize a DNAPL source can lead to incomplete/unsuccessful treatment, or in some cases treatment designs that target a significantly larger volume than might otherwise be needed. Neither of these outcomes are ideal, and they are always tied to an insufficient understanding of the complex distribution of contaminant mass in the subsurface. We know that the geology and three-dimensional (3D) aquifer permeability architecture influences the distribution of DNAPL, resulting in a highly variable distribution of DNAPL, including “fingers” of DNAPL migration along preferential pathways. In addition, the maturity of the source zone affects the distribution of contaminant mass relative to subsurface hydrostratigraphic compartments, namely low-permeability storage zones, moderate permeability slow advection zones, and higher permeability transport zones. A long-term DNAPL source can have significant contaminant mass stored in low-permeability zones. By classifying the source zone maturity, practitioners can better anticipate the nature of source zone and contaminant mass distribution.

While it is generally recognized that DNAPL source zones can have complex distributions of mass, many sites unfortunately lack a DNAPL conceptual site model that is high enough in resolution to optimally inform remediation decisions. Often, the conceptual site model is based on historic data collected from monitoring wells and coring completed during well installation, or other borings installed for delineation. These methods have been part of the conventional practice, but can easily mischaracterize the distribution of DNAPL. DNAPL can be missed based on the drilling locations and installation intervals or over-estimated based on the resolution of the techniques used. Whole core saturated-soil sampling (WCSS) and dye tests can interrogate larger intervals than where the DNAPL is actually present. More discrete screening techniques like the membrane interface probe (MIP) can point to the presence of DNAPL but fail to distinguish between actual DNAPL and high dissolved-phase concentrations. Finally, the accumulation of DNAPL in a monitoring well often reflects the mobility of the NAPL rather than the thickness of the interval where it is present.

With this in mind, in this column we will explore background on the role that conventional tools can play in DNAPL source zone characterization and their potential pitfalls. We will then introduce a new class of characterization tools that can provide high-resolution simultaneous characterization of DNAPL presence and aquifer permeability. These tools build on established optical screening and contaminant fluorescence technology that has proven ideal for real-time, high-resolution mapping of petroleum hydrocarbons, creosotes, and coal tar-based NAPLs—adapting it to nonfluorescent organic NAPLs. These optical screening tools are dramatically improving our ability to characterize these challenging source zones. To illustrate we explore an example where the application of this technology refined the conceptual model for a highly complicated and mature DNAPL source zone. This in turn sheds light on details that will help future remedial action avoid failure due to conditions that might not have otherwise been well understood. Conventional DNAPL Source Zone Characterization Tools When approaching DNAPL source zone characterization, a number of high-resolution characterization methods

AGS February 2018

Fluorescent Dyes: A New Weapon for Conquering DNAPL Characterization (Continued)

that have been commercially available for many years have become the standard tools that many practitioners embrace. More specifically, the Geoprobe® MIP and WCSS are often the go-to methods.

The MIP consists of a heated semipermeable membrane on a downhole direct-push probe; if volatile organic compounds (VOCs) are present they can diffuse across the membrane into a nitrogen carrier gas which transports them to uphole sensors. The uphole sensors consist of a photoionization detector (PID), flame ionization detector, and a detector targeted at chlorinated compounds (typically an electron capture device on older equipment, or halogen-specific detector on newer equipment).

The MIP has been a useful tool for rapidly screening large areas, and generating high-resolution data on the presence of VOC contamination. This technique effectively provides qualitative to semi-quantitative screening

of the magnitude of total VOC impacts in the subsurface, but is not designed for quantitative mapping of DNAPL or LNAPL (light nonaqueous phase liquid). Various authors have suggested modifications to MIP operating procedures and data interpretation to improve on the ability to screen for DNAPL or resolve high-concentration zones. However, the MIP is still best suited as a tool that can be used to rapidly and cost-effectively screen large areas to determine the relative distribution of contaminant mass.

Depending on the site-specific objectives and economics, a compliment or alternative to MIP is WCSS with above-ground dye tests. WCSS involves collecting soil samples at densely spaced vertical intervals. Samples collected through WCSS can be analyzed in a traditional laboratory, but are best suited for a specialized high-capacity mobile lab, allowing the investigation to be adaptive based on the real-time analytical results. Because the WCSS samples are analyzed by a laboratory, they provide quantitative, compound-specific results to better inform the conceptual site model relative to screening approaches. In addition, WCSS programs can be adjusted if DNAPL is anticipated by using hydrophobic dyes (e.g., above-ground dye tests) that can reveal the presence

Figure 1 The complex distribution of DNAPL in the subsurface can be difficult to detect. (A) 2-feet section of soil core from a DNAPL source zone. DNAPL zones are shown in red. (B) Measurements from the PID are at a maximum value due to the high concentrations in the core. (C) Hydrophobic dye shake tests conducted at 1-feet intervals are all negative for the presence of DNAPL. (D) Hydrophobic dye shake tests conducted at a denser spacing, 0.1-feet intervals, are able to identify the zones of the core with DNAPL present.

AGS February 2018


of the DNAPL. However, DNAPL can be difficult to identify visually in a core, and darker-colored DNAPLs may provide a color change that is too subtle to be consistently identified with dye tests. Plus, depending on the spacing between soil samples, it is possible to miss changes in DNAPL presence/absence, which often occur at centimeter scale.

Consider the data presented in Figure 1, which illustrates the difficulties of correctly identifying DNAPL in a soil core. Moving from left to right across the figure, there are four steps (A to D) that are explored. On the left side of Figure 1 (Step A) is the collection of a 2-foot soil core with two thin DNAPL zones. Step B involves screening with a PID, which is hampered by the fact that the high-concentration across the soil core is maxing out the PID within the DNAPL interval as well as above and below it. Step C involves hydrophobic dye shake tests, which are a more reliable method for identifying the presence or absence of DNAPL. However, depending on the intervals between each shake test, the results can be misleading and suggest that no DNAPL is present. Only by conducting even denser dye test spacing, as shown in Step D, would the DNAPL be identified.

A New Tool for Non-Fluorescent DNAPL Source Zone Characterization: DyeLIF Commercially available fluorescence screening tools include: (1) the Dakota Technologies Ultra-Violet Optical Screening Tool (UVOST®) and the Tar-Specific Green Optical Screening Tool (TarGOST®); (2) the Rapid Optical Screening Tool (ROST™) operated by Fugro; and (3) the ultraviolet-based optical image profiler by Geoprobe. All of these tools rely on detection of the inherent fluorescence of NAPLs when they are exposed to excitation light, commonly referred to as induced fluorescence. The UVOST and TarGOST tools rely on laser energy to deliver the excitation light (and are therefore classified as “laser-induced fluorescence,” or LIF), and have a decades long history of providing real-time, high-resolution mapping of petroleum hydrocarbons, creosotes, and coal tar-based DNAPLs due to their inherently fluorescent nature.

Unfortunately, traditional LIF does not work for non-petroleum DNAPLs that are not inherently fluorescent. However, the application of indicator dyes that can partition into the DNAPL and impart the ability to fluoresce is helping address this challenge. This new technique is called DyeLIF™, and provides high resolution and simultaneous characterization of non-fluorescent DNAPLs and aquifer permeability.

Before we consider the benefits of this type of real-time high-resolution technology along with an example field application, the following sections provide an introduction to the principles behind both LIF and how the DyeLIF technique works.

Laser-Induced Fluorescence Principles and Fluorescent Dyes Optical screening tools (OSTs) such as UVOST and TarGOST are delivered using direct push tools such as cone penetrometer test (CPT) and percussion-enhanced systems such as Geoprobe. OSTs consist of an excitation laser light source at the surface, fiber optics strung through the rod string, and optical detection and processing equipment at the surface. As the probe rods are advanced into the subsurface at a steady pace, the laser pulses exit the fiber and are directed out a sapphire window present near the probe’s tip (or above the tip and sleeve sensors in the case of CPT). The laser light is both absorbed and/or reflected (scattered) by the soil matrix outside the sapphire window. Any polycyclic aromatic hydrocarbons (PAHs) found in petroleum hydrocarbon, coal tar, or creosote NAPLs will absorb some portion of the laser pulse. The complex mixtures of excited state PAHs search for ways to return to their ground state and many do so almost immediately by releasing a portion of that absorbed laser energy as light (fluorescence), thus the term “laser-induced

AGS February 2018


fluorescence.” A portion of the resulting fluorescence is captured and transmitted back up to the ground surface equipment through optical fiber, where it is captured, analyzed, recorded, and displayed in real time.

DyeLIF System Overview Figure 2 is an illustration detailing the downhole detection process of DyeLIF. Solvation of the dye from the “snail’s trail” of indicator fluid into DNAPL is very fast (milliseconds), allowing for continuous delivery of the DyeLIF probe and thus continuous data acquisition vs. depth. Relatively slow penetration rates of approximately 0.4 cm/s are used to maximize the chance of successfully logging even very small ganglia.

The dye is injected at a relatively low flow rate of 1 mL/s to avoid any risk of displacing DNAPL ganglia away from the probe rod’s immediate exterior in highly permeable soils and thus out of reach of detection by the LIF. Flow and pressure sensors in the uphole fluid delivery system, combined with an additional downhole pressure sensor at the injection port, constantly monitor the dye’s flow rate and both the uphole and downhole

injection pressure. This provides high-resolution information on the relative hydraulic conductivity (K) of the soil, in a manner similar to other hydraulic profiling tools including the Geoprobe HPT™ (Hydraulic Profiling Tool) and Waterloo APS™ (Advanced Profiling System). The resulting DyeLIF logs depict corresponding depth profiles of fluorescence response (DNAPL indicator) as well as the Venom dye fluid flow rate, back-pressure, and estimated K (foot/day, if calibrated with nearby wells or downhole dissipation tests were conducted).

As with any sensing tool, proper calibration is required to ensure that the results can be effectively and accurately interpreted. For DyeLIF this accounts for drift in the intensity of the delivered laser pulse, the collection optics, and efficiency of the detector. It can also support the identification and isolation of fluorescence resulting from non-DNAPL-related sources, to avoid false positives and provide an understanding

Figure 2 Schematic of DyeLIF probe. Dye is injected through a screen at Location (A). Laser light pulses travel through fiber-optic lines (Location B), and exit through the sapphire window (Location C). If DNAPL is present, the dye solvates into the DNAPL and imparts a fluorescence response (D) in response to the laser energy, which is recorded uphole by the optical detection equipment (Location B).

AGS February 2018


of all the different fluorescence observed. For example, at three of the sites the authors worked on, there were individual fluorescence logs for the “raw” DyeLIF response, the target chlorinated DNAPL response, a peat response, and a response related to naturally fluorescent fill.

DyeLIF Benefits The preceding sections provide an introduction to the DyeLIF tool and method; readers interested in greater technical detail and the results of the first study are directed to Einarson et al. (2016; Einarson, Fure, St. -Germain, Chapman, and Parker, in preparation). For the balance of this column, we will focus on the lessons learned and benefits observed from multiple subsequent field applications of DyeLIF that the authors have been involved in.

As high-resolution characterization methods gain more traction, there are immediate benefits to consider in three key areas, described here as they relate to DyeLIF:

Improved data quality. A DNAPL investigation using monitoring wells or WCSS can miss discrete intervals of DNAPL due to well screen placement or selected sample intervals. An investigation using MIP does not directly detect DNAPL. By comparison, DyeLIF provides continuous data and discrete detection of DNAPL that can then be used to select intervals for confirmatory sampling, as appropriate. This combination can provide greater confidence in the outcome of the overall characterization effort.

Increased productivity. DyeLIF relies on direct push drilling techniques, so productivity in the field is similar to what can be achieved with other direct-push reliant real-time characterization methods such as MIP. The productivity, however, is dramatically improved over a traditional investigation that requires longer drilling, sample collection, and analysis times. The real-time data generated via the DyeLIF method can also be used to adapt the original investigation plan. This can drive more complete characterization in the same mobilization, helping to compress the overall time and effort required for complete characterization.

Improved health, safety, and sustainability. Because the DyeLIF method itself does not involve bringing contaminated media to the surface, it is inherently safer and more sustainable than methods that do. Safer due to the reduced opportunity for direct contact with the contaminants and sustainable due to the reduced quantity of investigation derive waste. Furthermore, the decreased amount of overall field time required to complete a characterization also contributes to the improved safety and sustainability profile of the method.

These are all important considerations where DNAPL is involved, and collectively lead to a fourth significant benefit. That is the high resolution of understanding that is generated to guide and optimize remediation decision-making. The following is an example of a DyeLIF field application that highlights this.

DyeLIF Application Example: Helping Avoid Potential Remedy Pitfalls The authors recently employed DyeLIF on a project to refine the conceptual site model prior to consideration of a source zone remedy. The project site is a former specialty chemicals manufacturing facility located along the

AGS February 2018


U.S. gulf coast. The underlying geology is of fluviodeltaic origin, consisting of alternating layers of sand and clay, with interbedding prevalent at the interfaces of each. There are significant amounts of organic matter (wood fragments, roots, and even intact logs) incorporated into the lower permeability zones. Historical operations at the site dating back to the 1950s resulted in releases of a host of NAPL phase constituents, primarily 1,2-dichloroethane; 1,2,3-trichloropropane; bis(2-chloroethyl)ether; bis(2-chloroethoxy)methane, and ethylene chlorohydrin.

Characterization of subsurface impacts began in the early 1980s, and a pump and treat (P&T) system was installed in the mid-1980s. In the decades since, many more borings have been advanced, monitoring wells installed and extraction wells added to the P&T system. Though a significant amount of mass has been removed to date by the P&T system, the trends are asymptotic with concentrations in the source zone monitoring wells remaining very high, pointing to the presence of a persistent NAPL source. In 2012, a DNAPL delineation effort was undertaken, relying on visual observations in soil cores and temporary monitoring wells, both methods that were typical for the time. An interpretation of the DNAPL body was assembled from the results, which implied that it was sitting at the bottom of the upper aquifer, where the monitoring wells were screened. The underlying interbedded zone and clay were not believed to have DNAPL present.

More recently, upon reflecting on the importance of a reliable conceptual model to both the scope and success of a potential remediation solution for such a DNAPL source zone, it was recognized that more information was needed to build on the results of the historic characterization effort. The first goal included confirming the true horizontal and vertical extent of DNAPL in the upper aquifer system at greater resolution, as the monitoring wells likely were only presenting the extent of mobile DNAPL. The second goal involved understanding the concurrent permeability distribution in equally high resolution, as this will also influence the DNAPL distribution as well as relevant remediation technologies.

DyeLIF was selected to meet the goals of the expanded characterization. As discussed earlier, a robust program of both bench testing before the field event and soil borings with specialized confirmation procedures during the field event is critical to ensure the reliability of the data. In this case, samples of DNAPL with different compositions were collected and tested in the lab using the DyeLIF equipment. This confirmed the compatibility of the DyeLIF method with the site DNAPL. The DNAPL from both wells invoked a strong fluorescence response under the DyeLIF tool, confirming the site was well suited for application of the method.

The DyeLIF field work took place over a period of 5 weeks, and collected over 250,000 data points. The real-time DyeLIF information was used to implement an adaptive field investigation in a single mobilization, rather than multiple staged investigations—compressing the cycle of data acquisition to decision-making. The initial planned network of DyeLIF borings consisted of 38 locations, and the field investigation was adaptively expanded to a total of 73 locations, as the extent of DNAPL was determined to be larger than mapped with conventional tools. At a subset of the DyeLIF borings, the validation program included multiple confirmation borings which employed high-resolution subcore analytical sampling, PID screening, two hydrophobic dyes, and core photography.

The simplest illustration of the DyeLIF results is through an integrated evaluation of the datasets from one of the confirmation borings (Figure 3). We recommend use of a dashboard-style visualization, which allows the

AGS February 2018


practitioner to combine all the lines of evidence available to evaluate the extent of DNAPL and confirm the DyeLIF response. Figure 3 displays nine separate lines of evidence broken out into individual columns, as -follows:

Column 1: Selected photographs from the confirmation soil boring to visually illustrate the soil types, any false positives, and visually identifiable DNAPL impact

Column 2: Interpreted stratigraphic log of soil types from the overall boring. Thicker segments represent coarser, more permeable soil types, while skinnier segments represent finer-grained, lower permeability soil types. This style of graphic log is grounded in classical geologic evaluation, and promotes stratigraphic interpretation of soil types, leading to a better understanding of the aquifer structure.

Column 3: Interpreted site-specific hydrostratigraphic units based on the soil types in Column 2 and permeability log (in Column 4).

Column 4: Estimated permeability log collected during DyeLIF boring. Increasing permeability is to the right on the graph.

Column 5: Results from co-located dye shake tests. The left column, labeled “Venom,” represents shake tests conducted using the “Venom” dye used in the DyeLIF tool. The right column, labeled “S-IV,” represents shake tests conducted using Sudan IV dye. In both columns a gray symbol pointing to the left represents a negative dye test, and a purple (Venom) or red (S-IV) symbol pointing to the right represents a positive dye test.

Column 6: Graph of high-resolution PID screening from the confirmation boring. Often the PID will be at a maximum value for some distance above and below a DNAPL zone, but in this case the low volatility of the DNAPL has made the PID measurements more sensitive to the target DNAPL zone.

Column 7: DyeLIF fluorescence results. Two curves are shown, one increasing to the left and colored red, and one increasing to the right and colored green-blue. The green-blue curve represents the total fluorescence response recorded by the DyeLIF probe. The red curve represents only the fluorescence response consistent with the DNAPL at the site. If the red and green-blue curves mirror each other, then it means the recorded total fluorescence is consistent with DNAPL; however, if the green-blue curve increases but the red curve does not, it indicates a source of fluorescence not consistent with the site DNAPL.

Column 8: Minicluster plots showing the DyeLIF fluorescence response across key intervals of the boring. Each cluster plot displays the fluorescence response of every data point with wavelength plotted on the x-axis, and fluorescence lifetime plotted on the y-axis. The cluster plots allow fluorescence analytics to further understand whether the fluorescence is not related to the DNAPL (and plots at the bottom right), or is consistent with the DNAPL (and plots in the upper center).

Column 9: Soil analytical results for total VOCs and semi-volatile organic compounds (SVOCs) at the confirmation boring.

AGS February 2018


The “DNAPL dashboard” (Figure 3) allows us to immediately identify zones with DNAPL with a high level of confidence. The DyeLIF fluorescence response was elevated between 15 and 20 feet bgs, and 30 and 40 feet bgs. In Column 7, the total fluorescence and DNAPL-specific fluorescence are mirror images, indicating the total fluorescence response is consistent with DNAPL. Both of these intervals correlate with positive dye tests using both dyes, elevated PID measurements, and peak soil concentrations (up to 20,000 mg/kg total VOCs and total SVOCs.

Because of the volume of data collected by high-resolution tools like DyeLIF, it is critical to visualize the results in 3D rather than as 2D maps and cross sections. 3D visualization facilitates comparison of the DNAPL indications with the stratigraphy, enhancing source zone interpretations. The interpreted 3D extent of DNAPL is shown on Figure 4, which shows the DyeLIF borings as blue tubes where no DNAPL was indicated, a yellow 3D volume which represents where DyeLIF indicated DNAPL, and an interactive cross section that can be placed at any orientation to illustrate how the geology is controlling DNAPL migration.

A number of significant revisions to the CSM resulted from the high-resolution investigation. Not surprisingly, the extent of DNAPL concluded from prior investigations using monitoring wells was not accurately representing the true extent of DNAPL: in some areas there was less DNAPL than indicated by prior investigations, and in other areas the prior investigations were under-estimating the overall DNAPL footprint.

In addition, the high-resolution characterization demonstrated that the distribution of DNAPL is highly variable,

Figure 3 DNAPL dashboard, combining multiple lines of evidence, including photographs, hydrostratigraphy, hydrophobic dye tests, DyeLIF, and analytical data.

AGS February 2018


with DNAPL seams as narrow as 0.2 feet thick located within a zone of sand-clay interbeds, in contrast with the idea of a DNAPL body resembling a contiguous pool atop a low-permeability zone. This improved understanding of the distribution and fine-scale changes in DNAPL, which will help reduce the list of potential remediation technologies and more effectively focus their application where the DNAPL is actually located in the subsurface. For example, consider the hypothetical application of thermal remediation to such a site, a technology often considered for treatment/removal of DNAPL source zones. Prior to the additional investigation, approaches like steam-enhanced extraction might have been considered effective for reducing source mass given their ability to target the more permeable zones atop the clays; however, as the investigation found significant mass deeper in low-permeability interbedded zones (consistent with what one might expect based on the age/maturity of this particular source zone), this method would have failed to sufficiently remediate the NAPL at depth within the low-permeability material. The same would have been true for other remedial methods. Alternatively, a containment or stabilization approach based on the DNAPL footprint interpreted from the conventional investigation could have left a significant amount of DNAPL unaddressed depending on the approach.

Striving for Continuous Improvement The DyeLIF technology is an example of a new class of data-rich real-time characterization and monitoring techniques that are supporting the implementation of more accurate, efficient, and timely remediation efforts. Not only are techniques like this easy to implement, but they gather thousands of data points in a single mobilization, and allow adaptive decision-making to drive further toward completion of the entire effort in a single mobilization of several weeks to months, vs. the many years and multiple mobilizations that conventional approaches often take. They also provide a much more accurate and representative understanding of the situation in the subsurface, relying far less on approximation. While DyeLIF creates a data-rich environment for decision-

Figure 4 Three-dimensional model output showing DyeLIF borings, stratigraphy, and interpreted extent of DNAPL.

AGS February 2018


making, the validation program is just as important as the DyeLIF data—the proper context for the fluorescence responses allows use of a DNAPL dashboard which drives better data interpretations and more accurate DNAPL CSMs. Additional DyeLIF data should never be collected at the cost of sacrificing the validation program.

Because of the density of the data generated, such techniques also require the ability to bring digital analytical and visualization tools to bear to ensure that the maximum benefit is extracted, with the end result a digital CSM that makes a complex situation easier for key stakeholders to understand.

Moving forward, we see a trend of innovation related to real-time characterization and monitoring of environmental contamination continuing, making higher and higher resolution possible. This will continue to shed more light on what is happening in the subsurface to support faster, more focused, and more successful restoration—even for sites that have conventionally been regarded as complex!

Read more about this article at: http://onlinelibrary.wiley.com/doi/10.1111/gwmr.12261/full

Soil Gas Sampling for 1,4-Dioxane during Heated Soil Vapor Extraction

Introduction 1,4-Dioxane is an emerging contaminant and evidence to date indicates that its use has led to extensive groundwater contamination. Being totally miscible in water, 1,4-dioxane is found in pore water in vadose zone soils as well as groundwater. Some 1,4-dioxane soil remediation technologies involve increasing temperature (e.g., heated SVE or electrical resistive heating). However, at elevated temperatures, analysis of 1,4-dioxane in soil gas may be problematic. Soil gas at elevated temperatures can have substantial water content, and condensation can occur when using sampling equipment and gas sampling canisters (e.g., Summa) which are at cooler temperatures. This water condensation does not present a sampling problem for common volatile organic compounds (VOCs) such as chlorinated solvents or petroleum hydrocarbons since they are not sufficiently water soluble and have a preference for the vapor phase. However, 1,4-dioxane, with a Henry's constant of 0.00014, partitions readily into the water phase (e.g., condensate), and failure to account for contaminant losses in the condensate phase has the potential to cause low gas sample analytical bias.

Little information on potential bias for 1,4-dioxane concentrations in soil gas collected at elevated temperatures is available in the literature, although, Oberle et al. indicated that during in-situ groundwater remediation of 1,4-dioxane using electrical resistance heating, 5% of the extracted 1,4-dioxane mass was found in the condensate. Assuming soil gas is at or near 100% humidity, greater temperature differentials between soil gas and the sampling canister would lead to greater 1,4-dioxane mass in the condensate and less in the measured vapor.

This paper describes a sampling device (vapor/condensate sampling apparatus) for collecting both vapor and water condensate from a heated soil gas stream so 1,4-dioxane mass in both the vapor and condensate phase could be assessed, enabling the accurate determination of concentrations at elevated soil gas temperatures. Laboratory experiments were conducted where aqueous 1,4-dioxane solutions were sparged at different temperatures and condensate and gas samples were collected using the vapor/condensate sampling apparatus to examine the potential for low analytical bias. Soil gas results were obtained during a pilot-scale demonstration at

AGS February 2018

Soil Gas Sampling for 1,4-Dioxane during Heated Soil Vapor Extraction (Continuous)

former McClellan AFB, CA of heated soil vapor extraction (SVE) for vadose zone remediation of 1,4-dioxane using the vapor/condensate apparatus. Field vapor/condensate apparatus sampling results are compared with those obtained by direct vapor canister sampling.

Methods A schematic of the vapor/condensate sampling apparatus is shown in Figure 1. A vacuum pump (Gast vacuum/pressure diaphragm pump, single head, 1 ft3/min) established flow for two flow paths: a by-pass purge line and a condensate and gas sample collection line. Nylon tubing (Nylaflow [Nazareth, Pennsylvania], 0.25 in. OD) was used for both flow streams. During field sample collection, flow was continuously maintained in the by-pass purge line, even during condensate collection, to minimize condensation within the well casing. A water trap in the by-pass purge line minimized condensate entering the vacuum pump. The condensate collection line consisted of a 0.25 in. OD stainless steel tubing coil and a 40 mL VOA vial at its base to capture condensate, all of which was immersed in an ice bath. Air flow proceeded through the coil and into the 40 mL VOA collection bottle to collect condensate. From the condensate collection unit, the flow was then directed to a similar stainless steel tubing coil immersed in ambient temperature water. Flow was controlled by a downstream, vacuum configured mass flow controller (Alicat Scientific [Tucson, Arizona], Model MC-10SLPM-D/5 V) and vacuum pump. The condensate coil air flow was tested at both 1 and 7 L/min for laboratory experiments and typically in the 7 to 8 L/min range for the field; the higher flow rates shorten field sampling times. The ice bath contained a perforated 4 in. diameter PVC pipe to allow insertion and withdrawal of the condensate coil with VOA vial in the ice bath without obstruction by ice. For both lab and field tests, a second condensate collection unit installed after the first unit was initially used to confirm that the first unit was sufficient (i.e., no breakthrough to the second unit).

In laboratory experiments, approximately 2 L of 18.5 mg/L 1,4-dioxane in water was sparged to generate the vapor stream sampled by the vapor/condensate sampling apparatus. A water bath was used to control the temperature of the sparged liquid. Temperatures of 30, 50 and 70 °C were examined to simulate expected soil temperatures during heated SVE. A stainless steel screen was used near the water surface within the sparge vessel to ensure no liquid phase droplets were entrained in the gas stream. Using the same sampling configuration as shown in Figure 1, except without the bypass, 1 L/min (using 0.0625 in. OD instead of 0.25 in. OD tubing mentioned above; 0.0625 in. OD is sufficient for lower flow) was pulled through the vapor/condensate sampling apparatus for separation and subsequent determination of condensate and vapor phase 1,4-dioxane concentrations.

For field sample collection, there were three steps: (1) purge; (2) condensate collection; and (3) vapor sampling. During the purge mode, valve #2 was open, valve #3 was closed, and the mass flow controller was powered off to prevent flow through the condensate collection and sampling system. During condensate collection, the mass flow controller was turned on and valve #3 was opened, allowing flow though both lines. During vapor sampling, 2-way valve #1 was switched to allow an attached evacuated vapor canister to pull a vapor sample. Vapor volume was calculated using the condensate collection mode sampling time. Volume of condensate was determined gravimetrically with pre-tared VOAs.

For both lab and field, 1,4-dioxane was determined in condensate samples by EPA Method 8270 (ALS Environmental, Kelso, Washington) and in vapor samples by EPA Method TO-15 (ALS Environmental, Simi Valley, California).

AGS February 2018


1,4-Dioxane mass in the condensate and vapor phases were calculated using Equations 1 and 2, respectively. (1)

(2)

where M cond is the 1,4-dioxane mass in the condensate, M vap is the 1,4-dioxane mass in vapor (after ice bath), C cond is the 1,4-dioxane concentration in condensate, C vap is the 1,4-dioxane concentration in vapor, V cond is the volume of condensate, and V vap is the volume of vapor sampled to obtain the condensate sample. The effective 1,4-dioxane vapor concentration (i.e., soil vapor concentration) was calculated using the combined 1,4-dioxane mass (vapor and condensate) and the volume of vapor used to collect the condensate.

(3)

The soil vapor field results presented were from a demonstration of enhanced SVE (heated air injection and focused extraction) for remediation of 1,4-dioxane in the unsaturated zone conducted at former McClellan AFB. Briefly, four heated air injection wells surrounded a central SVE well. Treatment zone soil temperatures reached as high as approximately 90 °C. Vapor results presented here are for samples with detections in both vapor and condensate phases. Soil vapor samples were obtained from vapor sampling probes within the treatment zone and from the SVE well (from wellhead, unless as stated from after air-water separator).

Results and Discussion Laboratory experimental results of sparged aqueous 1,4-dioxane solutions sampled with the vapor/condensate sampling apparatus are shown in Figure2. Results show that a significant fraction of 1,4-dioxane mass was present in the collected condensate (even at 30 °C) and the fraction increased with increasing temperature. Those results indicated that there was potential for low sampling bias if the vapor stream condensate was not accounted for. Since the vapor/condensate sampling apparatus used an ice bath to collect condensate, the results are expected to represent the maximum extent of low sampling bias (i.e., less condensation would occur at ambient temperature).

Figure 1 Schematic of vapor/condensate sampling apparatus.

Figure 2 Lab based vapor/condensate sampler results (A: 1,4-dioxane mass in condensate; B: 1,4-dioxane Henry's Law constant) for sparged aqueous 1,4-dioxane solution at different temperatures. Solid line in B are temperature-dependent 1,4-dioxane Henry's Law constants from Ondo and Dohnal.

AGS February 2018


Also shown in Figure 2 are the 1,4-dioxane Henry's Law constants obtain from the experimental system results along with those of Ondo and Dohnal. The experimental system was not designed to determine Henry's Constants, but assuming that the vapor and condensate phases are in equilibrium Henry's constants can be calculated from the data obtained. The experimentally determined Henry's Law constants from this study are in reasonable agreement with those of Ondo and Dohnal.

Soil gas sampling results (from soil gas probes and SVE well) with detections in both vapor and condensate phases collected using the vapor/condensate sampling apparatus during the heated SVE field treatment are shown in Figure 3. These results are plotted as 1,4-dioxane vapor concentrations with and without the 1,4-dioxane mass from the ice bath condensate. Incorporation of the 1,4-dioxane mass in the condensate resulted in significantly higher vapor concentrations. These field soil gas results are also presented as the 1,4-dioxane mass fraction in condensate vs. the total 1,4-dioxane concentration in Figure 4. This figure illustrates more clearly that a substantial portion of the 1,4-dioxane mass (generally in the 30 to 50% range of total 1,4-dioxane mass) was found in the condensate when collected by the vapor/condensate sampling apparatus. The mass fraction of 1,4-dioxane in the condensate as a function of soil gas temperature is shown in Figure 5; temperatures were estimated using measured temperatures adjacent to the soil vapor probes, or within the SVE well gas stream as appropriate. Also shown in Figure 5 are the laboratory results (Figure 2 data) to allow comparison of the field results with the idealized laboratory system. There was reasonable agreement between the field and lab results up to approximately 40 °C, above which a significantly lower percentage of 1,4-dioxane mass was present in the field sample condensate. This is likely a result of soil moisture losses and low RH in soils above 40 °C (due to the heated air injection), a condition which was not a factor in the laboratory testing. In other words, by the time the soils reach higher temperatures most of the soil moisture has been lost and some of the zones in the soil were likely completely clean, thus yielding lower values than the simple lab system.

Soil gas sampling using the vapor/condensate apparatus is more costly than the more traditional method of direct vapor canister sampling due to additional labor, equipment, and analytical costs. To examine whether direct vapor canister sampling was comparable for this field demonstration of heated air injection SVE, two additional sampling methodologies were used: (1) direct canister sampling of vapor after the air water separator (AWS) and condensate from the AWS; and (2) direct canister sampling at the SVE wellhead. Direct vapor canister sampling was performed during sampling events when the vapor/condensate sampling apparatus was used to allow comparison. The AWS is essentially an inefficient, high-volume version of the ice bath condenser in the vapor/condensate sampling apparatus (i.e., less condensate is collected since an ice bath was not used in AWS). By analyzing both the AWS condensate and vapor downstream of the AWS, as well as knowing the AWS condensate collection rate, the total sample gas concentrations (C eff vap) could be calculated in the same fashion as for the vapor/condensate sampling apparatus.

Results of the three sampling methods are shown in Table 1. Sampling for 1,4-dioxane at the AWS (AWS condensate and vapor after AWS) provided comparable results to those obtained using the vapor/condensate apparatus. However, the AWS samples indicated that only a small amount of 1,4-dioxane mass was contributed by the AWS condensate. The direct vapor canister samples collected downstream of the AWS without the condensate (C vap) compared well with the vapor/condensate apparatus results (Figure 6; Note: SVE well was sampled at slightly different times for each method thus slightly different air streams may have been sampled).

AGS February 2018


In contrast, results of direct gas sampling using vapor canisters at the SVE wellhead provided erratic results. Two of the four direct gas sampling events were reasonably comparable (within 35% of other sampling methods), whereas, the other two events showed sample results that were at least a factor of five less than those obtained using the vapor/condensate apparatus or the AWS vapor/condensate method. The reason for this erratic behavior is not known, however it is unlikely the SVE well air stream would have changed by a factor of five or more between the three sampling methods. These results suggest that the direct gas sampling was a less reliable methodology.

Soil gas sampling during injected heat SVE using the vapor/condensate sampling methodology indicated that substantial 1,4-dioxane mass was present in the condensate phase. The vapor/condensate sampling methodology was a reliable gas sampling procedure for 1,4-dioxane, minimizing potential low sampling bias due to condensation. Direct sampling of soil gas at the SVE wellhead generated erratic and biased low results compared to those obtained using the vapor/condensate apparatus, however direct vapor sampling after the air-water separator did produce results reasonably comparable to the vapor/condensate methodology.

Figure 3

Field based 1,4-dioxane soil vapor concentrations (mg/m3) obtained using vapor/condensate sampling apparatus during heated SVE operation (Cvap: vapor after ice bath; Ceff vap: reconstituted from vapor and condensate). Dashed line is for a 1:1 agreement between the two concentrations.

Figure 4 1,4-Dioxane mass fraction in condensate vs. total 1,4-dioxane concentration (mg/m3) obtained using vapor/condensate sampling apparatus during heated SVE operation.

AGS February 2018


Read more about this article at: http://onlinelibrary.wiley.com/doi/10.1111/gwmr.12255/full

Figure 6 Comparison of 1,4-dioxane concentrations obtained using: 1) vapor/condensate sampling apparatus at well head and 2) canister (without ice bath) after air-water separator (i.e., Cvap for AWS method in Table 1). Dashed line is for a 1:1 agreement between the two concentrations.

Figure 5 1,4-Dioxane mass fraction in condensate at different temperatures for laboratory (open circles; dashed line) and field (solid circles) samples collected during heated SVE operation. Field samples above 40 °C had lower RH which largely accounts for lower 1,4-dioxane mass in the condensate.

Atlanta Science Festival Geology Walk

March 18 and 22, 2018 Tag along with two geologist-educators to see the beautiful building stones and folded natural rock layers of Midtown Atlanta, on a tour from Symphony Hall to Rhodes Hall. Dr. Bill Witherspoon, co-author of Roadside Geology of Georgia, teams up with highly sought guest speaker from Georgia Mineral Society and Atlanta Geological Society, Bill Waggener, to interpret the stories that rocks tell. Tickets required in advance, at $5 plus processing fee. Admission includes a Georgia Mineral Society grab bag. https://www.freshtix.com/events/roadside-geology-walk

2018 Tellus Mineral Symposium March 24, 2018 – 9am to 5pm

Join experts in the field to learn about the geology and minerals found at some of the outstanding mineral localities within the Southeast. Prepaid reservations are required by March 16, 2018. Cost includes all presentations, breakfast and lunch, as well as Museum admission. http://tellusmuseum.org/our-events/mineral-symposium-2018/

AGS February 2018

National Groundwater Awareness Week March 11-17, 2018 The National Ground Water Association today announced this year’s National Groundwater Awareness Week will take place March 11-17, 2018. An annual observance established to highlight the responsible development, management, and use of groundwater, the event is also a platform to encourage yearly water well testing and well maintenance to prevent waterborne illnesses. Established in 1999, National Groundwater Awareness Week provides an opportunity for people to learn about the importance of the resource and how it impacts lives. “Approximately 132 million Americans rely on groundwater for drinking water, so, simply put, it makes life possible,” said Aaron Martin, public relations and awareness manager of NGWA. “Additionally, groundwater is used for irrigation, livestock, manufacturing, mining, thermoelectric power, and several additional purposes, making it one of the most widely used and valuable natural resources we have.” From manmade contaminants such as PFAS (per- and polyfluoroalkyl substances) and naturally occurring ones like arsenic affecting its quality to potential depletion of the resource in India, South Africa, Australia, and the American West, groundwater was an important topic in 2017. NGWA expects much of this narrative to continue throughout 2018, emphasizing the need for increased awareness regarding one this critical natural resource. Consider the following:

· Americans use 79.6 billion gallons of groundwater each day. · Groundwater is 20 to 30 times larger than all U.S. lakes, streams, and rivers combined. · 44 percent of the U.S. population depends on groundwater for its drinking water supply. · More than 13.2 million households have their own well, representing 34 million people.

The 2018 theme of “Tend. Test. Treat.” was established to encourage a more holistic approach to sustain an adequate supply of quality groundwater. Testing your water might prompt well inspection and maintenance, and water treatment can mitigate naturally occurring contamination revealed by the test. So, test your water, tend to your well system, then treat the water if necessary. NGWA encourages every person to be a “groundwater advocate” both during National Groundwater Awareness Week and beyond by protecting and conserving groundwater. Businesses, individuals, educators, students, federal agencies, cities, associations, and everyone in between can share their story through our website or on social media. For downloadable information on the event, including:

· A social media toolkit · Facts about groundwater · Event FAQs · Logos and graphics · Videos

Please visit GroundwaterAwarenessWeek.com or WellOwner.org.

The National Ground Water Association is a not-for-profit professional society and trade association for the global groundwater industry. Our members around the world include leading public and private sector groundwater scientists, engineers, water well system professionals, manufacturers, and suppliers of groundwater-related products and services. The Association’s vision is to be the leading groundwater association advocating for responsible development, management, and use of water. Aaron Martin | Public Relations and Awareness Manager National Ground Water Association 800.551.7379 ext. 1564 / 614.898.7791 ext. 1564 773.505.4325 (mobile) www.ngwa.org

AGS February 2018

February 2018 Atlanta Geological Society PG Candidate Workshop

Date: Saturday, February 24, 2018 Time: 10:00 am to 12:00 pm Venue: Fernbank Science Center (check with the receptionist for the specific classroom) 156 Heaton Park Drive, N.E. Atlanta, GA 30307 678-874-7102 Speaker: Dr. Jim Kennedy, PhD, PG Subject: Aspects of Groundwater Hydrology Contaminant Hydrogeological Behavior Dr. Kennedy will cover different aspects of groundwater hydrology, definitions, and applications of principles to define a hydrological system. He will also discuss various aspects of chemicals and their behavior in groundwater flow systems. Jim is the State Geologist of Georgia and holds B.S. and M.S. degrees in physics and geophysical sciences from Georgia Tech and a Ph.D. in geology from Texas A&M where he did research on reclaimed lignite mines. As State Geologist, he has worked on the Coastal Sound Science Initiative to manage salt-water intrusion into the Upper Floridan aquifer, permitting of coastal groundwater supply wells, and the State Water Plan. He also has provided expert testimony at the Office of State Administrative Hearings in support of landfill, quarry, and water withdrawal permits issued by the Georgia Environmental Protection Division. Prior to joining the EPD, Dr. Kennedy worked as a consultant and conducted engineering geology, groundwater supply, and environmental remediation projects in various areas of the United States and Europe. Please join us and forward this message to anyone who might be interested in the topic. Two Professional Development Hours are available for attendees of the class. The classes are open to all, membership in the AGS is not required, but encouraged. Please consider joining (an application is attached), the AGS is one of the most active geological organizations in the Southeast. For more information on the workshop and/or becoming a member, please visit www.atlantageologicalsociety.org or contact us at the addresses below. Atlanta Geological Society Professional Registration Committee Ken Simonton, P.G. [email protected] Ginny Mauldin-Kinney [email protected]

AGS February 2018

Fernbank Events & Activities

AstronomyDaySaturday, February 24, 2018 Discover space, astronomy and how scientists learn about our universe through hands-on activities. Learn more

BreathwalkCourseSeriesTuesday, March 13, 2018 New program! Learn the theory, science and benefits of Breathwalk during this six course series. Learn more

FernbankAfterDark:Microbes&MicrobrewsFriday, March 9, 2018 Discover how your biology influences your relationships during this 21+ event. Learn more

TadpolesSaturday, February 24, 2018 Preschoolers will enjoy an out-of-this-world story and a special activity with a Fernbank educator.

Learn more

AGS February 2018

Wildwoods and Fernbank Forest Wildwoods features 75 acres of lush woodlands,

highlighted by hands‐on exhibits for all ages, tree

pods suspended in the canopy, a nature gallery,

immersive adventures, and meandering trails

emphasizing dramatic slopes and stunning

views. This interpretive nature experience serves as

the new entrance into Fernbank Forest.

Learn more

The Secret World Inside You On view February 10 – May 6, 2018 It’s What’s Inside that Counts Meet your microbiome, the community of microbes

that keep your immune system, digestive system and

brain working properly. Using larger‐than‐life models,

videos, interactive experiences, unique games, and

immersive displays, discover what and where these

microbes are, how they help us, how we sometimes

disrupt them, and how we can work with them to

make our lives better than ever.

Learn more

AGS February 2018

Now showing in the Fernbank IMAX movie theater:

Museum Alive 3D February 9 – June 21, 2018 The fantasy that drives sleepovers and fires the imagination of every museum visitor is at the very heart of Museum Alive 3D—What if the exhibits could come to life? Follow one lucky visitor who stays in the museum after dark, when the most fascinating extinct prehistoric creatures rise again. Dinosaurs, a sabre-tooth tiger, giant birds and monster reptiles escape their display cases, shake off the dust and explore the museum, by means of stunning special effects. And far from being just fantasy, everything in Museum Alive 3D is firmly rooted in the latest science, through a unique collaboration between leading paleontologists and award-winning CGI artists. Audiences will be treated to a thrilling, spectacular film that both educates and entertains—because as the lights go down, the past comes roaring back to life!

Incredible Predators 3D September 30 – March 22, 2018 Life at the top of the food chain isn’t easy. Even the most ferocious predators must overcome great odds to feed their families and survive. Incredible Predators 3D takes viewers on a globe-spanning journey to meet unique creatures, from the minuscule mantis to the massive blue whale. Experience the thrill of the chase, the great escapes, and the remarkable strategies and determination of nature’s predators in Fernbank’s state-of-the-art Giant Screen Theater.

Fernbank Museum of Natural History

(All programs require reservations, including free programs)

AGS February 2018

AGS Committees

AGS Publications: Open

Career Networking/Advertising: Todd Roach

Phone (770) 242‐9040, Fax (770) 242‐8388

[email protected]

Continuing Education: Open

Fernbank Liaison: Kaden Borseth

Phone (404) 929‐6342

[email protected]

Field Trips: Open

Georgia PG Registration: Ken Simonton

Phone: 404‐825‐3439

[email protected] Ginny Mauldin‐Kenney,

ginny.mauldin@gmailcom

Teacher Grants: Bill Waggener

Phone (404)354‐8752

[email protected]

Hospitality: John Salvino, P.G.

[email protected]

Membership: Burton Dixon

[email protected]

Social Media Coordinator: Carina O’Bara

[email protected]

Newsletter Editor: James Ferreira

Phone (508) 878‐0980

[email protected]

Web Master: Ken Simonton

[email protected] www.atlantageologicalsociety.org

AGS 2018 Meeting Dates

Listed below are the planned meeting

dates for 2018. Please mark your calendar

and make plans to attend.

2018 Meeting Schedule March 27

April 24

May 29

June 26

July 31

PG Study Group meetings Contact Ken Simonton for the details.

March 31

April 28

May 26

June 30

July 28

AGS Officers

President: Ben Bentkowski

[email protected]

Phone (770) 296‐2529

Vice‐President: Steven Stokowski

[email protected]

Secretary: Rob White

Phone (770) 891‐0519

[email protected]

Treasurer: John Salvino, P.G.

Phone: 678‐237‐7329

[email protected]

Past President

Shannon Star George

AGS February 2018

ATLANTA GEOLOGICAL SOCIETY

www.atlantageologicalsociety.org ANNUAL MEMBERSHIP FORM

Please print the required details and check the appropriate membership box. DATE:_____________________________________________ NAME:____________________________________________

ORGANIZATION:____________________________________________________________

TELEPHONE (1): TELEPHONE (2): EMAIL (1): EMAIL (2):

STUDENT $10 PROFESSIONAL MEMBERSHIP $25 CORPORATE MEMBERSHIP $100 (Includes 4 professional members, please list names and emails below) NAME: EMAIL:

NAME: EMAIL:

NAME: EMAIL:

NAME: EMAIL:

For further details, contact the AGS Treasurer: John Salvino [email protected]

Please make checks payable to the “Atlanta Geological Society” and bring them to the next meeting or remit with the completed form to:

Atlanta Geological Society, Attn: John Salvino 3073 Lexington Avenue

Woodstock, Georgia 30189

To pay electronically; click

https://squareup.com/store/atlanta‐geological‐society CASH CHECK (CHECK NUMBER:___________)

atlanta geological society newsletteratlantageologicalsociety.org/wp-content/uploads/... · algal...

Documents