Spatial modeling for groundwater arsenic levels in North Carolina

Environmental Science & Technology
By: , and 



To examine environmental and geologic determinants of arsenic in groundwater, detailed geologic data were integrated with well water arsenic concentration data and well construction data for 471 private wells in Orange County, NC, via a geographic information system. For the statistical analysis, the geologic units were simplified into four generalized categories based on rock type and interpreted mode of deposition/emplacement. The geologic transitions from rocks of a primary pyroclastic origin to rocks of volcaniclastic sedimentary origin were designated as polylines. The data were fitted to a left-censored regression model to identify key determinants of arsenic levels in groundwater. A Bayesian spatial random effects model was then developed to capture any spatial patterns in groundwater arsenic residuals into model estimation. Statistical model results indicate (1) wells close to a transition zone or fault are more likely to contain detectible arsenic; (2) welded tuffs and hydrothermal quartz bodies are associated with relatively higher groundwater arsenic concentrations and even higher for those proximal to a pluton; and (3) wells of greater depth are more likely to contain elevated arsenic. This modeling effort informs policy intervention by creating three-dimensional maps of predicted arsenic levels in groundwater for any location and depth in the area.

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Publication type Article
Publication Subtype Journal Article
Title Spatial modeling for groundwater arsenic levels in North Carolina
Series title Environmental Science & Technology
DOI 10.1021/es103336s
Volume 45
Issue 11
Year Published 2011
Language English
Publisher American Chemical Society.
Description 8 p.
First page 4824
Last page 4831
Country United States
State North Carolina
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