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| Publications— Open-File Reports |
In cooperation with the Pennsylvania Department of Health and the Pennsylvania Department of Environmental Protection
U.S. Geological Survey Open-File Report 2006-1376
By Dennis J. Low and Daniel G. Galeone
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View the full report in PDF 7.8 MB
Samples of ground water for analysis of total-arsenic concentrations
were collected in eight counties--Potter, Tioga, Bradford, Susquehanna, Wayne, Pike, Sullivan, and Wyoming--and
from eight bedrock formations (bedrock aquifers) and overlying glacial aquifers in the north-central and northeastern
parts of Pennsylvania in July 2005 and from March through June 2006. The samples were collected from a total of 143
domestic wells, 2 stock wells, 4 non-community wells, 2 community water-system wells, and 3 domestic springs by well or
spring owners using sampling kits provided by the U.S. Geological Survey (USGS). An additional 15 domestic wells were
sampled by the USGS for analysis of total arsenic. These 15 samples were collected using the same methods and sampling
kits provided to the homeowners.
Samples were analyzed for total arsenic by the Pennsylvania Department of Environmental Protection Laboratory using
a minimum reporting level of 4.0 µg/L (micrograms per liter). Arsenic was detected in water from 18 domestic wells in four
counties--Bradford (3 wells), Sullivan (1 well), Tioga (13 wells), and Wayne (1 well). The median concentration of total
arsenic was less than 4.0 µg/L, and the maximum concentration was 188 µg/L. Water from 10 wells had concentrations of total
arsenic greater than the U.S. Environmental Protection Agency Maximum Contaminant Level of 10 µg/L.
Detectable concentrations of total arsenic were measured in water from wells that ranged in depth from 29 to 400 feet, and
that were completed in three aquifers--Lock Haven Formation, Catskill Formation, and unconsolidated glacial sediments; no
springs had detectable concentrations of total arsenic. Water samples representing the Lock Haven Formation were collected
from 60 wells; water from 12 of these wells had detectable concentrations of total arsenic. Water samples representing the
Catskill Formation were collected from 57 wells; water from 4 wells had detectable concentrations of total arsenic. Water samples
representing the unconsolidated glacial sediments were collected from 17 wells; 2 wells had water with detectable concentrations
of total arsenic.
Contingency tables tested for significant differences in total arsenic between aquifers, topographic settings, and well
depths. Concentrations of total arsenic were significantly greater (95-percent confidence level) in the Lock Haven Formation
than in the other bedrock units. Concentrations of total arsenic also varied significantly by topographic setting. Wells
completed in the Lock Haven Formation and located in valleys had significantly greater concentrations of total arsenic than
similar wells located on hilltops or slopes. Concentrations of total arsenic did not vary significantly by topographic setting in
the Catskill Formation. Concentrations of total arsenic did not vary significantly by well depth for any aquifer.
Iron staining, hydrogen-sulfide odor, or both were common complaints of well owners. Iron staining was a complaint
of 44 well owners. Hydrogen-sulfide odor was a complaint of 35 well owners. Fourteen well owners complained of both iron
staining and hydrogen sulfide. No correlation to the presence of arsenic in the wells sampled was found with iron staining,
hydrogen-sulfide odor, or both.
Water from 8 of the 10 wells that contained concentrations of total arsenic greater than 10 µg/L were sampled by USGS
personnel for the determination of concentrations of dissolved arsenic (minimum reporting level 0.3 µg/L) and arsenic species
{arsenite [As (III)], arsenate [As (V)], monomethylarsonate (MMA), and dimethylarsinate (DMA)} at the USGS National
Water Quality Laboratory. Analytical results from these samples showed a median concentration of 38.7 µg/L dissolved
arsenic in water and a maximum of 178 µg/L. As (III) was the most common arsenic species present in the water for seven of
the eight wells and was found in water characteristic of reducing environments [pH 8.2 to 9.1, dissolved oxygen 0.06 to 0.29 milligrams
per liter (mg/L), and oxidation reduction potential -63 to -203 millivolts (mv)]. As (V) was the dominant arsenic species
in water characteristic of an oxidizing environment (pH 4.8, dissolved oxygen 2.15 mg/L, oxidation reduction potential
265 mv). The arsenic species MMA and DMA were detected in the water from two wells. The arsenic species MMA was
detected at an estimated concentration of 0.9 µg/L in water from one well; the concentration was less than 1.2 µg/L in water from
seven wells. The arsenic species DMA was detected at concentrations of 1.0 and 1.5 µg/L in water from two wells; the concentration
was less than 0.6 µg/L in water from six wells. Both wells that contained detectable concentrations of MMA and DMA produced
water that was characteristic of reducing environments.
Abstract
Introduction
Purpose and Scope
Previous Work
Description of Study Area
Geohydrology
Bedrock Aquifers
Unconsolidated Aquifers
Water Use
Methods of Study
Sampling Design
Well and Spring Owner Participation and Sampling
Targeted Sampling
Laboratory Procedures and Quality Control
Arsenic Concentrations in Ground Water
Reconnaissance of Total-Arsenic Concentrations
Relation of Total Arsenic to Geology
Relation of Total Arsenic to Iron Staining and Hydrogen Sulfide
Redox Conditions and Concentrations of Arsenic Species
Summary
Acknowledgments
References Cited
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View the full report in PDF 7.8 MB
For more information about USGS activities in Pennsylvania contact:
Director
USGS Pennsylvania Water Science Center
215 Limekiln Road
New Cumberland, Pennsylvania 17070
Telephone: (717) 730-6960
Fax: (717) 730-6997
or access the USGS Water Resources of Pennsylvania home page at:
http://pa.water.usgs.gov/.
