Rapid Assessment of Soil Metal Concentrations Along the Animas River

San Juan River Basin Agricultural Irrigation

Arteries that deliver life-giving water

Specialty Horticultural Crops

Animas River Sediment south of Colorado/New Mexico border August 7, 2015

NAPI main canal breech Friday 13, 2016

Field Portable XRF Basics

• Each element has electronic orbitals of characteristic energy

• Following removal of an inner electron by an energetic photon provided by a primary radiation source, an electron from an outer shell drops into its place

• There are a limited number of ways in which this can happen:

• L→K transition is traditionally called Kα• M→K transition is called Kβ• M→L transition is called Lα

• Each of these transitions yields a fluorescent photon with a characteristic energy equal to the difference in energy of the initial and final orbital

• The wavelength of this fluorescent radiation can be calculated from Planck's Law: E= nhv

• n=1,2,3…; h= Planck’s constant; v= frequency

• The fluorescent radiation can be analyzed either by sorting the energies of the photons (energy-dispersive analysis) or by separating the wavelengths of the radiation (wavelength-dispersive analysis)

• Intensity of each characteristic radiation is directly related to the amount of each element in the material

Field Portable XRF Basics• A battery operated, Olympus Delta series PXRF (Rh x‐ray tube

operated at 10-40 kV) • Stainless steel ‘316’ standardization clip is used to standardize

the instrument• 16.13% Cr• 1.78% Mn• 68.76% Fe• 10.42% Ni• 0.20% Cu • 2.10% Mo

• Instrument operated in either soil mode or geochem mode• Uses a scatter normalization algorithm (per EPA Method

6200) for soil, liquids, and powders allowing for sequential analysis of atomic numbers Z=15 (Phosphorus) to Z=92 (Uranium)

• Optimized tube excitation increases performance on lighter elements (Ca, K, S, P, Cl, and I)

• Samples scanned for 30 s per beam through the ~2 cm aperturePrice: ~$45,000

Allows for multiple soil science applications:• Horizonation• Gypsum/calcic/podzol horizons• Soil fertility (CEC)• Soil pH/EC

Field Portable XRF Basics

• Data processing includes reporting of the standard error on an individual element basis

• Limit of detection (LOD) is defined as three times the standard error for each element

• Varies by element, with higher atomic numbered elements generally allowing for lower detection limits

• Logged data exported to MS Excel for further statistical analyses

Reference MethodsUS-EPA Method 6200 USDA NRCS: 7.3.1 X-Ray

Fluorescence, Handheld

Potential Soil Science Applications of PXRF

• Applications:• Textural determination

• pH

• Salinity

• Cation exchange capacity

• Base saturation percentage*

• Plant essential elements

• Mineralogy

• Advantages:• Non-destructive

• Rapid

• Multi-element

• Low limits of detection and wide dynamic range

• Disadvantages:• No H, C, or Na

• Moisture effects

• Soil heterogeneity

Portable X-ray fluorescence (PXRF) spectrometry (Sept 1-3, 2015)

Riverbank sampling

Field sampling

PRXF Results Sept 1-3, 2015

Aluminum (Al)

Iron(Fe)

Copper (Cu)

Zinc (Zn)

Arsenic(As)

Lead(Pb)

Ave Range Ave Range Ave Range Ave Range Ave Range Ave Range

n Location ...................................................................Parts per million (ppm or mg/kg)………………………………………………………….

29 Not Irrigated 64087 25413-83540 28987 9047-50892 33 ND-94 117 25-330 7 ND-13 53 12-230

67 Irrigated 53541 7281-80325 28514 4430-48232 36 11-100 175 39-819 7 ND-13 67 5-271

35 Riverbank 37749 4218-80108 38302 5818-293194 77 ND-220 365 19-1068 11 ND-38 153 10-487

9 RiverbankSludge

21018 8730-38781 48355 38292-75959 137 90-176 474 277-1174 40 ND-54 637 509-859

140

Long Term Monitoring Plan (Proposed)• Element 3.0: Soils and Sediment

• Determine if elevated heavy metal concentrations presently occur in stream and irrigation ditch sediment, and in soil that has been irrigated with water diverted from the Animas River; and

• THREE SAMPLE POINTS DURING GROWING SEASON

• Monitor the migration of contaminated surface water sediment from Colorado (CO) into New Mexico (NM), as it pertains to irrigated agriculture and the river-agricultural land interface.

• ONCE PER YEAR AFTER IRRIGATION SEASON

• Element 10.5: Agricultural Crops• Determine if elevated heavy metal

concentrations occur in agricultural crops that have been irrigated with water diverted from the Animas River;

• MONITOR POTENTIAL AREAS OF CONCERN FROM SOIL AND SEDIMENT DATA

• Extent contingent upon funding

Some additional thoughts….• In the absence of

appreciable humic matter, Pb is strongly adsorbed on clay minerals and Fe oxides

• According to Chaney, Pb from sludge does not give rise to an increase in plant Pb unless the concentration is very high.

• Our soil chemistry may work in our favor (alkaline soils with variable calcium carbonate CaCO3)

pH and Plant Nutrients

Acknowledgements

•NMSU Agricultural Experiment Station

•Natural Resources Conservation Service/United States Department of Agriculture

•NMSU-ASC Farmington staff

• Texas Tech University