Direct assessment of groundwater vulnerability from single observations of multiple contaminants

Abstract

Groundwater vulnerability is a central concept in pollution risk assessment, yet its estimation has been largely a matter of expert judgment. This work applies a method for the direct calculation of vulnerability from monitoring well observations of pesticide concentrations. The method has two major advantages: it is independent of the compounds being examined, and it has a direct probabilistic interpretation making it ideal for risk assessment. The methodology was applied to data from a groundwater monitoring program in the midwestern United States. The distribution of the vulnerabilities was skewed toward zero. Spatial distribution of the vulnerabilities shows them to be controlled by both regional and local factors. Methods are presented for estimating the necessary sample sizes for vulnerability studies. The further application of the approach developed in this study to understanding groundwater pollution is discussed.

Aquifer vulnerability to pesticide pollution—combining soil, land-use and aquifer properties with molecular descriptors

“…The plot does not show any particular trends in the residual suggesting that the model fits equally well across the all the soil types and land-use settings throughout the area of the 12 states covered in the survey and that errors are due to local, catchment specific effects. Worrall and Kolpin (Worrall and Kolpin, 2004) have measured groundwater vulnerability directly for these sites using the method of (Worrall, 2002) and shown an east -west trend which is not apparent here, suggesting that Model 1 fits equally well for low as well as high vulnerability sites.…”

Groundwater Risk Assessment Model (GRAM): Groundwater Risk Assessment Model for Wellfield Protection

“…Such an approach requires modeling of pollutant transport and fate. Similarly, statistical methods based on the concepts of uncertainty have been developed [20][21][22]. Both methods require an extensive data base, including monitoring and actual measurements of contaminant concentrations to calibrate and validate the models.…”

The vulnerability of groundwater to pesticide contamination estimated directly from observations of presence or absence in wells

“…The method of combining pesticide data to give a measure of vulnerability has been detailed in Worrall (2002) and Worrall and Kolpin (2003). An outline description of the method follows.…”

“…This method has been developed for regional surveys, where there are multiple observations of a single compound in each well in the survey (Worrall, 2002) and for where there are single observations of a range of compounds in each well (Worrall and Kolpin, 2003), this paper uses the latter method. Both approaches use an established Bayesian method for comparing two proportions (Berry, 1996), where one is the proportion of detections of a contaminant at a monitoring point and the other is the proportion of detections for that contaminant in the region as a whole.…”