Pesticides in ground water in selected agricultural land-use areas and hydrogeologic settings in Pennsylvania, 2003-07

Loper, Connie A.; Breen, Kevin J.; Zimmerman, Tammy M.; Clune, John W.

doi:10.3133/sir20095139

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“…A study of groundwater quality in agricultural areas of the mid‐Atlantic region, including seven sites in carbonate‐rock aquifers of the Great Valley Potomac River basin in Pennsylvania (south of the area on which this article is based), reported significantly decreasing recovery‐adjusted concentrations of atrazine, DEA, and prometon in 2002 compared with 1993 (Debrewer et al, 2008). A study of nine pairs of pesticide results for groundwater in agricultural areas in the Lower Susquehanna River basin in the Valley and Ridge and Piedmont carbonate‐rock aquifers in Pennsylvania reported significantly decreasing unadjusted atrazine concentrations in 2003 compared with 1993–1995 (Loper et al, 2009). Five of the nine wells analyzed by Loper et al (2009) were used for the analysis herein.…”

Section: Resultsmentioning

confidence: 99%

“…A study of nine pairs of pesticide results for groundwater in agricultural areas in the Lower Susquehanna River basin in the Valley and Ridge and Piedmont carbonate‐rock aquifers in Pennsylvania reported significantly decreasing unadjusted atrazine concentrations in 2003 compared with 1993–1995 (Loper et al, 2009). Five of the nine wells analyzed by Loper et al (2009) were used for the analysis herein.…”

Section: Resultsmentioning

confidence: 99%

“…Pesticide occurrence is not unique to carbonate aquifers; however, these vulnerable settings present a good test case for studies evaluating changes in pesticide concentrations over time. In these settings, detected compounds are numerous, typically have long half‐lives, and are leachable; short half‐life or nonleachable compounds generally are not observed (Loper et al, 2009; Lindsey et al, 2009; Lindsey et al, 2010).…”

Section: Noncensored and Censored Matched Pair Information For Five Fmentioning

confidence: 99%

“…The use of spikes in splits of well‐water samples, or field matrix spiking, offers benefits over reagent‐water spiking because analytical bias is measured in the sample and is more likely to account for matrix interferences (Martin et al, 2009). Previous investigations in Pennsylvania by the USGS, including those by Lietman (1997), Lindsey et al (1998), Hainly et al (2001), Fischer et al (2004), and Loper et al (2009), used unadjusted concentrations and did not use reagent water or matrix water recovery‐adjusted pesticide concentrations when presenting or analyzing pesticide concentration data. Previous investigations outside of Pennsylvania have used matrix‐based, recovery‐adjusted concentrations to assess for changes in concentrations (H.M. Johnson et al, 2011; Saleh et al, 2011; Stackelberg et al, 2012; Sullivan et al, 2009).…”

Section: Noncensored and Censored Matched Pair Information For Five Fmentioning

confidence: 99%

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Evaluating Changes in Matrix-Based, Recovery-Adjusted Concentrations in Paired Data for Pesticides in Groundwater

Zimmerman

Breen

2012

J. Environ. Qual.

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Pesticide concentration data for waters from selected carbonate‐rock aquifers in agricultural areas of Pennsylvania were collected in 1993–2009 for occurrence and distribution assessments. A set of 30 wells was visited once in 1993–1995 and again in 2008–2009 to assess concentration changes. The data include censored matched pairs (nondetections of a compound in one or both samples of a pair). A potentially improved approach for assessing concentration changes is presented where (i) concentrations are adjusted with models of matrix‐spike recovery and (ii) area‐wide temporal change is tested by use of the paired Prentice‐Wilcoxon (PPW) statistical test. The PPW results for atrazine, simazine, metolachlor, prometon, and an atrazine degradate, deethylatrazine (DEA), are compared using recovery‐adjusted and unadjusted concentrations. Results for adjusted compared with unadjusted concentrations in 2008–2009 compared with 1993–1995 were similar for atrazine and simazine (significant decrease; 95% confidence level) and metolachlor (no change) but differed for DEA (adjusted, decrease; unadjusted, increase) and prometon (adjusted, decrease; unadjusted, no change). The PPW results were different on recovery‐adjusted compared with unadjusted concentrations. Not accounting for variability in recovery can mask a true change, misidentify a change when no true change exists, or assign a direction opposite of the true change in concentration that resulted from matrix influences on extraction and laboratory method performance. However, matrix‐based models of recovery derived from a laboratory performance dataset from multiple studies for national assessment, as used herein, rather than time‐ and study‐specific recoveries may introduce uncertainty in recovery adjustments for individual samples that should be considered in assessing change.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Noncensored and Censored Matched Pair Information For Five Fmentioning

confidence: 99%

Section: Noncensored and Censored Matched Pair Information For Five Fmentioning

confidence: 99%

See 2 more Smart Citations

Evaluating Changes in Matrix-Based, Recovery-Adjusted Concentrations in Paired Data for Pesticides in Groundwater

Zimmerman

Breen

2012

J. Environ. Qual.

Self Cite

View full text Add to dashboard Cite

show abstract

Pesticides in ground water in selected agricultural land-use areas and hydrogeologic settings in Pennsylvania, 2003-07

Cited by 1 publication

References 1 publication

Evaluating Changes in Matrix-Based, Recovery-Adjusted Concentrations in Paired Data for Pesticides in Groundwater

Evaluating Changes in Matrix-Based, Recovery-Adjusted Concentrations in Paired Data for Pesticides in Groundwater

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