Residues in groundwater

Polynitroaromatic compounds are used as explosives. They are toxic and might cause liver damage, methemoglobinemia and uncoupling of the oxidative phosphorylation process. Trace analyses of polynitroaromatic residues in groundwater, surface water, rainwater... 

Saturated Zone Models. Results from unsaturated zone simulations can be used as inputs to saturated zone models to predict concentrations of aldicarb residues in groundwater. The saturated zone model used by the author takes the pesticide inputs into groundwater, as predicted by PRZM, and calculates the concentration and movement of aldicarb residues in the upper portion of the saturated zone. The core of the saturated zone model is a finite element solute transport calculation procedure developed at the University of Wisconsin (25). The accuracy of this model in estimating pesticide movement in groundwater is (as with other... 

Clearly, the persistence and resultant distribution of aldicarb residues in groundwater are far from uniform, even under uniformly treated, uniformly irrigated fields. Residues seem to dissipate to levels of <10 yg/L or disappeared entirely by the time they reach depths of 3-4 m below the water table, but were more persistent in some areas than others. 

Wisconsin has had a number of experiences in dealing with traces of pesticide residues in groundwater the most notable is the presence of aldicarb residues in shallow aquifers in the Central Sands region of the State (Table I). 

Value of Good Agricultural Practices for Avoidance of Detectable Pesticide Residues in Groundwater", National Agricultural Chemical Association, 1984. 

The ELISA (enzyme-linked immunosorbent assay) test kit for sulfentrazone and SCA residues in groundwater is developed with limit of quantitation (LOQ)... 

The muiti-residue method for aiachior, acetochior, and metoiachior determines the concentrations of these anaiytes in groundwater and surface water. This method in-voives the addition of a deuterated intemai standard to the water sampie, concentration of the anaiytes on an SPE coiumn, eiution of anaiytes, concentration of the eiuate to a set voiume, and anaiysis by GC/MS. The use of internai standards compensates for recovery tosses, but separate experiments were conducted to ensure that recoveries were within 70-i20%. The method was vaiidated over the range of 0.05-20 xgL for aii components and is presented in Section 6. 

As more sensitive analytical methods for pesticides are developed, greater care must be taken to avoid sample contamination and misidentification of residues. For example, in pesticide leaching or field dissipation studies, small amounts of surface soil coming in contact with soil core or soil pore water samples taken from further below the ground surface can sometimes lead to wildly inaccurate analytical results. This is probably the cause of isolated, high-level detections of pesticides in the lower part of the vadose zone or in groundwater in samples taken soon after application when other data (weather, soil permeability determinations and other pesticide or tracer analytical results) imply that such results are highly improbable. 

Best practices in the analysis of residues in environmental samples groundwater and soil-water monitoring procedures... 

MPE provides several advantages when compared with the use of SVE or pump-and-treat alone. MPE provides for an increase in groundwater recovery rates, an increase in ROI in individual ground-water recovery wells, and recovery of shallow free product. By depressing the groundwater table in the vicinity of the extraction wells, MPE provides for remediation of the capillary fringe and smear zone, and remediation of volatile, residual contaminants located above and below the water table.46... 

Deep-well injection of the gas may force briny water to the surface, potentially polluting streams and aquifers. Earthquakes have also been reported in places where deep-well injection has occurred and carbon dioxide can convert to an acid in groundwater. Carbon storage provides a unique advantage, buried in an oil field, the gas boosts oil production by forcing residual deposits to the surface. At Weyburn, oil production is up 50% since carbon dioxide injection began four years ago. 

Free-phase NAPL refers to NAPL that exists as an independent phase, not as a dissolved component in the pore water or pore atmosphere. The environmental concerns associated with sites affected with free-phase NAPLs revolve around hydrocarbon-impacted soil (residual hydrocarbon), the NAPL itself (which can serve as a continued source for groundwater contamination), dissolved hydrocarbon constituents in groundwater, and hydrocarbon vapors. The detection of free-phase NAPLs in the subsurface presents many challenges. Two questions frequently arise at sites impacted by NAPLs how much is there and how long will it take to clean up. Before one can address these two questions, assessments of the type and subsurface distri-... 

---