Pennsylvania Water Science Center



CONTACT FOR MORE INFORMATION

Tammy Zimmerman
(tmzimmer@usgs.gov)

 

In cooperation with Pennsylvania Department of Agriculture


Application of pre-emergent herbicides in Cumberland County; photo by Bruce D. Lindsey, USGS

Pesticides in Pennsylvania Groundwaters

This project is part of a collaboration that began between the U.S. Geological Survey (USGS) and the Pennsylvania Department of Agriculture in the 1980s. The work continues presently with active cooperation and funding support from Pennsylvania Department of Agriculture and the USGS Cooperative Water Program.

Current projects
2015 to 2020—Sampling to determine changes in pesticide concentrations in hydrogeologic settings

  • Sampling to determine changes in pesticide concentrations in carbonate settings

Selected wells in four carbonate settings that had been previously sampled twice (once in the 1990’s and once in the 2000’s) are being resampled in 2015-2018 to determine if concentrations of pesticides in groundwater have changed or stayed the same. Contact Eliza Gross (egross@usgs.gov; 717-730-6973) for more information on this study.

  • Sampling to determine changes in pesticide concentrations in non-carbonate settings

Selected wells in two non-carbonate settings that had been previously sampled are being resampled in 2019-2020 to determine if concentrations of pesticides in groundwater have changed or stayed the same. Contact Eliza Gross (egross@usgs.gov; 717-730-6973) for more information on this study. 

Past projects

Before 1993—Earliest work
Assessments by USGS in various physiographic regions and aquifers of Pennsylvania led the way in understanding pesticide occurrence in groundwater and illustrated that limestone (carbonate-rock) areas are vulnerable to contamination by pesticides.

  • Pioneering research on pesticide occurrence in the Piedmont Physiographic Province, Lancaster County
    This USGS study established the importance of aquifer material type in explaining the occurrence of pesticides in groundwater.  Carbonate aquifers were more vulnerable to contamination than noncarbonate aquifers.
    See USGS Report WSP 2493.
  • Regional reconnaissance assessment of pesticide occurrence in the Valley and Ridge Physiographic Province
    One of the earliest regional reconnaissance assessments of pesticide occurrence was done by USGS in 1980-85 across Bedford, Blair, Centre, Clinton, Huntingdon, and Mifflin Counties.  The carbonate aquifers of Cambrian and Ordovician age were assessed by sampling 20 wells and springs.  This assessment discovered exceptionally large concentrations of herbicides in water from well BA 437 and identified this well as a hot-spot location in a limestone area. 
    See USGS Report OFR 90-109.
  • Pesticide occurrence in the Pequea and Mill Creek watersheds, Lancaster County
    A groundwater assessment of 167 wells conducted by USGS in 1991 discovered exceptionally large concentrations of herbicides in water from well LN 1842 and identified this well as a hot-spot location in a limestone area. 
    See USGS Report AWDR 1992, volume 2, p279 to access data from the assessment.

1993 to 2001—First cycle of USGS National Water-Quality Assessment studies and statewide study design for assessing pesticide occurrence
Regional assessments by USGS included parts of four major watersheds in Pennsylvania. One assessment component was the occurrence and distribution of pesticides in groundwater.

  • Lower Susquehanna River Basin
    Pesticide occurrence and distribution was based on results for 169 wells sampled in 1993-95.  
    See USGS Report WRIR 01-4012.
  • Allegheny and Monongahela River Basins 
    Pesticide occurrence and distribution in groundwater was based on results for 58 wells sampled in 1996-98. 
    See USGS Report C-1202.
  • Delaware River Basin
    Pesticide occurrence and distribution in groundwater was based on results for 76 wells sampled in 1999-2001. 
    See USGS Report C-1227.
  • Potomac River Basin
    Pesticide occurrence and distribution was based on results for 105 wells sampled in 1993-95.  
    See USGS Report OFR 97-666.

A hydrogeologic framework was created to be used as a basis for sampling for pesticides in Pennsylvania, and a prioritized plan for sampling groundwater in areas of the state that had not been adequately characterized for the occurrence of pesticides was presented.

  • Study design for statewide assessment of pesticide occurrence

Initially, the USGS National Water-Quality Assessment (NAWQA) program design laid the foundation for regional assessments of pesticides in Pennsylvania groundwaters. An example of NAWQA design is found in USGS Report OFR 97-583.


The statewide design for Pennsylvania is documented in USGS Report 99-4076 and establishes settings for assessment based on physiography and major aquifer material types documented by the Pennsylvania Department of Conservation and Natural Resources and glacial data documented in USGS Data Series 38. Carbonate aquifers are made up of limestone and dolomite. Crystalline aquifers are typically schists or other metamorphic or igneous rocks. Siliciclastic aquifers are commonly sandstones, siltstones, and shale. Surficial aquifers are often comprised of unconsolidated sands and gravels. (Click the image below for a larger version of the map of hydrogeologic settings.)
  Map of Pennsylvania Hydrogeology
This study also used a map of major aquifer types based on major aquifer material types to illustrate vulnerable settings. In the simplest terms, the four aquifer material types are distributed across Pennsylvania as shown in the map below. Carbonate aquifers are made up of limestone and dolomite and, when at or near the land surface, are the most vulnerable to contamination. The noncarbonate aquifers are: crystalline aquifers typically comprised of schists or other metamorphic or igneous rocks; siliciclastic aquifers commonly comprised of sandstones, siltstones, and shale; and surficial aquifers often comprised of unconsolidated sands and gravels. (Click the image below for a larger version of the map of major aquifer material types.)
Map of Pennsylvania Major Aquifer Material Types

  • Quality-assurance design for statewide assessment of pesticide occurrence

An assessment of pesticides in groundwater from carbonate aquifers in the Delaware River Basin illustrated how quality-control samples are used to assure quality of pesticide results. 
See
 USGS Report WRIR 00-4104.
2002 to 2014—Sampling to complete a statewide assessment and determine changes in pesticide concentrations in hydrogeologic settings

  • Sampling to complete a statewide assessment

To fill gaps in the statewide assessment, USGS sampled five hydrogeologic settings in 2003-2007 to characterize pesticide occurrence. See USGS Report Sir 2009-5139.

  • Sampling to determine changes in pesticide concentrations in carbonate settings

Selected wells in carbonate settings that had been sampled in 1993-1995 were resampled in 2008-2009 to determine if concentrations of pesticides in groundwater had changed or stayed the same. See Journal of Environmental Quality article by Zimmerman and Breen, 2012

  • Sampling to determine changes in pesticide concentrations in non-carbonate settings

To determine if concentrations of pesticides in groundwater had changed or stayed the same, USGS resampled three non-carbonate hydrogeologic settings in 2010 and 2012-2013. Also, to continue filling in gaps in the statewide assessment, a non-carbonate setting was sampled for the first time in 2014. A Scientific Investigations Report documenting these sampling results is currently being written. Contact Eliza Gross (egross@usgs.gov; 717-730-6973) for more information on this study.  
Other sources of pesticide data in Pennsylvania

  • Statewide compilation of groundwater quality data 

USGS Data Series 314 contains data in spreadsheet file format for selected pesticide compounds from the following sources--Pennsylvania Drinking Water Information System, Pennsylvania Department of Agriculture, Pennsylvania Department of Environmental Protection–Bureau of Water Supply Management, and U.S. Geological Survey.  Data are included for 4,868 samples collected and analyzed for fungicides, herbicides, insecticides, and pesticides.

  • Pesticide data for surface waters in Pennsylvania

Occurrence of pesticide residues in four streams draining different land-use areas in Pennsylvania

Herbicide concentrations in and loads transported by the Conestoga River and Pequea Creek, Lancaster County, Pennsylvania, 1992-95

  • Delaware River basin sampling by USGS for the National Water-Quality Assessment

Jordan Creek at Schnecksville, Pa. (station no. 01451800). See pages 6-7 of the 1999 data report.
Synoptic survey of organochlorine pesticides in streambed sediment: Streambed sediment samples were collected during low-flow conditions in the Delaware River Basin during July and August 1998, and June-August 1999 to determine concentrations of trace elements and hydrophobic organic compounds in stream bed sediments. Sites were located throughout the Delaware River Basin in New Jersey, New York, and Pennsylvania. Bed sediment samples at each site were composites of the top 1 to 2 centimeters of material from at least 5 different depositional areas within the stream reach.
See pages 6-27 of the data report
Synoptic survey of organochlorine pesticides in fish tissue: The purpose of this survey was to assess the occurrence and distribution of trace metals and organochlorine compounds in fish tissue. Samples were collected from sites throughout the Delaware River Basin in New Jersey, New York, and Pennsylvania. The following species were collected: white sucker (Catostomus commersoni), common carp (Cyprinus carpio), and smallmouth bass (Micropterus dolomieui). 
See pages 28-41 of the data report
.

Synoptic survey of stream-water quality: The data were collected as part of two basin-wide synoptic surveys of nutrients, pesticides, major ions, and organic carbon; the first survey was May 3-18, 1999, and the second was August 30-September 15, 1999. Data were collected at 24 sites as part of this synoptic. Selected samples were analyzed for pesticides on schedule 2001 (listed with minimum reporting levels on page 2); only pesticides identified by the analyses in one or more samples are listed in the water-quality tables. 
See pages 45-56 of the data report

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