View Full Table | Close Full ViewTable 1.

Noncensored and censored matched pair information for five frequently detected pesticide compounds in 30 wells sampled once in 1993–1995 and once in 2008–2009 in predominantly agricultural areas in the Piedmont and Valley and Ridge carbonate-rock aquifers in Pennsylvania.

 
Number of sample pairs
Pesticide compound Total Detections in both samples of a sample pair (noncensored data only) Detection in one sample and nondetection in one sample of a sample pair (noncensored and censored data) Nondetections in both samples of a sample pair (censored data only, otherwise known as zero- difference ties)
Deethylatrazine 30 30 0 0
Atrazine 30 30 0 0
Metolachlor 30 6 6 18
Prometon 23† 13 4 6
The presence of prometon was verified but not quantified in one sample analyzed in 1993–1995 and six samples analyzed in 2008–2009; hence, there are 23 sample pairs to assess. All other frequently detected pesticide compounds had 30 sample pairs.



View Full Table | Close Full ViewTable 2.

Water-quality characteristics and major ion concentrations in groundwater from wells sampled in two carbonate-rock aquifers, Pennsylvania.

 
Carbonate-rock aquifer Piedmont (n = 10; sampled 12–28 July 1993) Valley and Ridge (n = 20; sampled 27 July–10 Aug. 1994 and 27 June–19 July 1995)
Characteristics Range of measured values†
 Water temperature, °C 11.5–14.0 10.5–15.0
 Specific conductance, μS cm−1 340–960 438–970
 Dissolved oxygen, mg L−1 0.9–10.6 6.1–10.0
 pH 7.0–7.5 7.1–7.7
Major ions‡ Concentration range, mg L−1
 Calcium 39.0–140 48–110
 Magnesium 5.4–43 7.2–48
 Sodium 3.4–15 1.6–54
 Potassium 0.6–5.1 0.8–5.1
 Bicarbonate 112–316 212–400
 Chloride 10.0–72 6.5–64
 Sulfate 10.0–130 8.2–33
 Silica (as SiO2) 7.0–13 5.1–13
 Nitrate plus nitrite (as N) 2.0–25 5.5–18
Range observed during dates sampled.
Major constituents and nutrients analyzed by U.S. Geological Survey National Water Quality Laboratory in samples filtered through a membrane with 0.45-μm pore size.