Fig. 1.

Locations of the Piedmont and Valley and Ridge carbonate-rock aquifers and wells sampled in Pennsylvania, 1993–2009. Base from U.S. Bureau of the Census (1990a, 1990b).

 


Fig. 2.

Groundwater samples with one or two, three or four, and five or more pesticide compounds detected in the Piedmont and Valley and Ridge carbonate-rock aquifers in 1993–1995 and 2008–2009. Results are based on analysis of 47 pesticide compounds.

 


Fig. 3.

Paired differences in concentrations 2008–2009 minus 1993–1995 for 30 wells for deethylatrazine, atrazine, metolachlor, prometon, and simazine in the Piedmont and Valley and Ridge carbonate-rock aquifers in Pennsylvania. z-Score, median difference (Turnbull method), and P value indicate results of the paired Prentice-Wilcoxon test (Helsel, 2005).

 


Fig. 4.

(A) Unadjusted and (B) recovery-adjusted concentrations for selected pesticide compounds in 30 wells sampled one time in 1993–1995 and one time again in 2008–2009 in predominantly agricultural areas in the Piedmont and Valley and Ridge carbonate-rock aquifers in Pennsylvania.