natural water chemistry
DESCRIPTION
Natural Water Chemistry. Water Quality Parameters. Temperature - Dissolved Oxygen (DO) - pH Alkalinity - Hardness Nitrates and Phosphates - Turbidity Conductivity -. Temperature. Affects: Water density Gas solubility Chemical reaction rates Organism growth rates - PowerPoint PPT PresentationTRANSCRIPT
Natural Natural WaterWater
Chemistry Chemistry
Water Quality ParametersWater Quality ParametersTemperature - Dissolved Oxygen (DO) - pH
Alkalinity - HardnessNitrates and Phosphates - Turbidity
Conductivity-
TemperatureTemperature
Affects:Water densityGas solubilityChemical reaction ratesOrganism growth ratesConductivitypHDissolved Oxygen
… Changes in seasonal/diurnal air temperature
… Thermal stratification in lakes
… Size and temperature of inflows
… Residence time (lakes)
Temperature – naturally variesTemperature – naturally variesbecause of…because of…
… Heated industrial effluent
… Runoff from asphalt/pavement
… Deforestation
Temperature – artificially variesTemperature – artificially variesbecause of…because of…
Q10 rulecold-blooded aquatic organismspoikilothermic = cold blooded
Predicts that growth rate will double if temperature increases by 10˚C (18˚F) within their "preferred" range.
Dissolved Oxygen (DO)Dissolved Oxygen (DO)
DO is the measurement of oxygen dissolved in water and available for fish and other aquatic life.
Indicates health of an aquatic system.
Can range from 0-18 ppm.
Most natural water systems require 5-6 ppm to support a diverse population.
Varies with time of day, weather, temperature.
Dissolved Oxygen (DO)Dissolved Oxygen (DO)
Increase in organic waste
Increase in algae/plant vegetation
Decrease in DO available to organisms
Leads to changes in ecosystem asorganisms needing lots of DO are replaced by organisms needing little.
Hood Canal, Wash. DOHood Canal, Wash. DO
HoodCanal
Part of Puget sound. Fed by snowmelt from Olympic Mountains.
Used for wildlife habitat, outdoor recreation, fisheries, home to two tribal nations.
Health of water threatened by decrease in DO – work underway by member of Hood Canal DO Project to try to find out why.
Sill
“Sill” reduces flow. Inflow from main entrance salt water, runoff fresh.
The freshwater carries natural stuff: fall leaves, winter run-off, salmon carcasses
Non natural stuff:yard waste, storm-water toxins, herbicide residue, effluents from septic tanks and sewers
Increase in organics leads to decrease in DO – this changes the ecosystem, as anoxia-loving critters take over as the O2-loving animals become choked out.Affects bottom first – bottom feeders will rise to top if they can (eg: rockfish, deep-sea shrimp), but others can’t (sea cucumbers, anemone, starfish)…so they perish.
Potential causesPotential causesNatural
• increased sunlight or other climate factors• increased nutrient availability• Changes in ocean properties• Changes in river input (e.g.: drought)• Changes in weather conditions
Artificial
• human loading of nutrients or organic material• Changes in river input (eg: diversion)
pHpH - - p(otential of) H(ydrogen)
Determines the solubility of nutrients (PO4-3, NO3
-, C) and heavy metals (Fe, Cu, etc)
Determines availability of these chemicals for use by aquatic life.
In natural water systems, determined largely by geology and soils.
pH of natural waterspH of natural waters
Modified from www.waterwatch.orghttp://www.vic.waterwatch.org.au/fortheteacher/manual/sect4f.htm
due to humic acid
Limestone, marble, CO3 richPure rain, snow
Sea water
Factors that affect pHFactors that affect pH• Algal blooms • Bacterial activity • Water turbulence • Chemicals flowing into the water body • Sewage overflows • Pollution
How pH affects aquatic lifeHow pH affects aquatic life
Decreasing pH (e.g.: via acid rain)
▼Liberation of Al, metals
▼Toxic conditions
▼Chronic stress
▼Smaller, weaker fish
AlkalinityAlkalinityAlkalinity refers to the capability of water to neutralize acid.
Buffering capacity – resistance to pH changes.
Common natural buffer: CO3 (carbonates – like limestone).
Protects aquatic life.
Commonly linked to water hardness.
In natural systems: 50 – 150 mg/L as CaCO3.Limestone outcrop
HardnessHardness
Reflects dissolved carbonate minerals.
Mostly of concern for drinking water standards.
Metals precipitate out of solution.
Create scale/hard water deposits
High alkalinity Hard water
From USGShttp://water.usgs.gov/owq/news.html
andand
Nitrate (NO3-)
naturally-occurring form of nitrogen found in soil.
Forms by microbial decomposition of fertilizers, plants, manures or other organic residues
Plants uptake nitrates (Spinach a good source).
Phosphate (PO4-3)
naturally occurs in rocks and minerals.
Plants uptake weathered-outelements and compounds.
Animals ingest plants.
Water soluble.
Redfield Ratio: 106:16:1
NitratesNitrates
The U.S. EPA has set a maximum contaminant level for NO3
- in drinking water of 10 parts per million (ppm)
Artificial sources:• Livestock manure/urine• Failing septic systems• Synthetic fertilizers
Can lead to:eutrophication of natural water systems (overproduction of vegetation)
Blue baby syndromne
Artificial sources:• Sewage• Laundry, cleaning fluids• Synthetic fertilizers
Can also lead to eutrophication of natural water systems (overproduction of vegetation)
PhosphatesPhosphates
Blue green algae
1990 and 1999 comparison 1990 and 1999 comparison of Nitrates in Great Lakesof Nitrates in Great Lakes
From US EPAhttp://www.epa.gov/glnpo/monitoring/limnology/SprNOx.html
Hypoxia in the Gulf of MexicoHypoxia in the Gulf of Mexico
Gulf of Mexico
Mississippi River drainage basin – 41% of US landmass.
Hypoxia – decreased oxygen
Colored areas are Key Farming States = The Corn Belt.
Many have drained 80% of Wetlands
Increased Fertilization flows from Mississippi River to the Gulf
Hypoxia in the Gulf of MexicoHypoxia in the Gulf of Mexico
Hypoxic waters
Image from Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC, January 2003
1.6 million tons Of nitrogen now enter the Gulf from the Mississippi basin
Hypoxia in the Gulf of MexicoHypoxia in the Gulf of Mexico
From NCAT (Nat’l Center for Appropriate Technology)http://www.ncat.org/nutrients/hypoxia/hypoxia.html
Particularly bad for fish because coastal areas is spawning grounds before moving to deeper waters.
Global distribution of oxygen-depleted coastal zones.
The 146 zones shown are associated with either major population concentrations or with watersheds that deliver large quantities of nutrients to coastal waters.
Source: Patrick Heffer, Short Term Prospects for World Agriculture and Fertilizer Demand 2002/03 - 2003/04 (Paris: International Fertilizer Industry Association (IFA), December 2003); IFA Secretariat and IFA Fertilizer Demand Working Group, Fertilizer Consumption Report (Brussels: December 2001); historical data from Worldwatch Institute, Signposts 2002, CD-ROM, compiled from IFA and the U.N. Food and Agriculture Organization, Fertilizer Yearbook (Rome: various years).
Solutions??Solutions??
Wetland restoration Reduce fertilizers
Reduce emissions – WWTP/industryReduce soil erosion
TurbidityTurbidity
Measures how “murky” the water is
Estimates:
Mineral fractionOrganicsInorganicsSoluble organic compoundsPlanktonMicroscopic organisms
MODIS Image from NASAhttp://rapidfire.sci.gsfc.nasa.gov/
Causes of highly waters
• In open waters, phytoplankton• Closer to shore, Mining Resuspended bottom sediments (wind) • Organic debris from stream Increased flow rates• Floods• Too many bottom-feeding fish (such as carp)• Hippos
Effects of highly waters
• Modify light penetration• Increase sedimentation rate• Smother benthic habitats • Settling clay particles can suffocate newly hatched larvae • Fine particulate material also can damage sensitive gill structures • Decrease organism resistance to disease• Prevent proper egg and larval development• Macrophyte growth may be decreased• Reduced photosynthesis can lead to lower daytime release of oxygen
From waterontheweb.orghttp://waterontheweb.org/under/waterquality/turbidity.html
ConductivityConductivity
Ability of a substance to conduct an electrical current.
In water, conductivity determined by types and quantities of dissolvedsolids. (Commonly called Total Dissolved Solids = TDS)
Current carried by ions (negatively or positively charged particles).
Eg: NaCl(aq) = Na + + Cl –
Cl-Na+Na+
Na+
Na+
Na+ Cl-
Cl-
Cl-
Cl-
Na+Cl- Cl- Cl- Cl-
Na+Na+ Na+Na+ Na+Na+ Na+Na+
Cl- Cl- Cl- Cl-
Na+ Na+ Na+Na+
Cl- Cl- Cl- Cl-
Na+ Na+ Na+Na+
Cl- Cl- Cl- Cl-
Na+ Na+ Na+ Na+Na+
Na+Na+
Na+ Na+
Na+ Na+
ConductivityConductivity
Conductivity of natural waters depends upon:
Ion characteristics (mobility, valence, concentration)More ions = more conductive
Water temperatureGeology – soil Size of watershedEvaporation – such as in Salt Lakes
Some artificial factors that can affect conductivity:WastewaterUrban runoff (especially road salt)Agricultural runoff
EC TDS
(μS/cm) (mg/L)
Divide Lake 10 4.6
Lake Superior 97 63
Lake Tahoe 92 64
Grindstone Lake 95 65
Ice Lake 110 79
Lake Independence 316 213
Lake Mead 850 640
Atlantic Ocean 43,000 35,000
Great Salt Lake 158,000 230,000
Dead Sea ? ~330,000
Electrical Conductivity
and
TDS
From wateronthweb.orghttp://www.waterontheweb.org/under/waterquality/conductivity.htmlSalt present in 1L water