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Paper No. 3-6
Presentation Time: 8:00 AM-5:30 PM
GEOCHEMICAL FINGERPRINTING WITH HANDHELD X-RAY FLUORESCENCE (XRF) OF POTENTIAL LOW FLUX LANDFILL LEACHATES
Using a handheld XRF it is possible to evaluate the nature and composition of local leachate seeps that have low and intermittent discharge. The purpose of this study is to use a repeatable test to determine if two local iron-rich seeps from the Austin Chalk bedrock and soil horizons in the Dallas-Fort Worth (DFW) Metroplex are indeed landfill leachates from nearby Municipal Solid Waste (MSW) and landfill transfer facilities. At one site the seepage occurs over a 300 m2 area, with average seep rates of 0.55 cm3/sec and total dissolved solid (TDS) 800-1100 ppm. Low levels of As, Cr, Cd, Pb and Se were found, with values ranging between 0.0002-0.012 ppm. These would classify as juvenile or diluted leachates, exhibiting relatively low concentrations of Cl (400 ppm inferred from TDS and alkalinity+hardness by test strip) and Ca (60-120 ppm by test strip) . Mg/Ca ratio is 18.81 ppm, Cl/Br ratio is 4.5 and NH3-N were 0.50 ppm by spectrophotometry, which also suggest that the potential leachate is still young. The amount of Fe present in the water was high with clear visible iron staining of Austin Chalk fractures that carry the potential leachate. Fe concentrations by XRF were 27.665 ppm. With water chemistry data and XRF analysis, it becomes possible to quantify local low flux seeps and determine the nature of leachate present. Our preliminary data suggests these are juvenile or diluted leachates, consistent with anaerobic conditions in the vicinity of municipal waste storage and processing facilities.