Spatial Modeling for Groundwater Arsenic Levels in North Carolina

Abstract

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.

Arsenic in North Carolina: Public Health Implications

“…The geocoding methods developed in this study data enabled a comprehensive report of over 4,000 yearly arsenic measurements with geographical coordinates from 1998-2007 and over 10,000 from 2008 to present, a substantial increase relative to the USGS and EPA ambient monitoring systems. Specifically, the number of records analyzed represents a 600-fold increase from samples collected by the USGS (USGS 2010) and more than three times the number of records analyzed in other studies North Carolina wells (Pippin 2005; Kim et al in press ). The substantial increase in recent well sampling is likely due to state legislation adopted in 2008 that requires every newly constructed well be tested.…”

“…We increased the knowledgebase using available locational information to assign geographic coordinates of domestic wells based on four spatial classes: GPS, street address, zip code, and county. As an example, we tripled the number of successfully geocoded points used in previous analyses over comparable geographic areas and timeframes (Pippin 2005; Kim et al in press ). Additionally, while others have shown that multi-stage geocoding methods improved the match rate compared to single-step methods (Lovasi et al 2007), to our knowledge, the present study is one of the first to use GPS locations to systematically quantify and account for geocoding location error.…”

“…An initial study by Pippin et al, (2005), characterized arsenic occurrence in North Carolina groundwater between 1996-2004 and employed classic kriging techniques to map arsenic probabilities in the state. More recently, Kim et al ( in press ), characterized geologic determinants of arsenic in Orange County, North Carolina. Our work builds upon earlier characterization of arsenic in North Carolina wells by developing methods to map historical contamination for the purposes of protecting public health.…”

Flow and sorption controls of groundwater arsenic in individual boreholes from bedrock aquifers in central Maine, USA

“…High arsenic (As) concentrations in domestic bedrock wells have emerged as a public health concern in Africa (Kortatsi, 2007; Smedley, 1996; Smedley et al, 2007), Asia (Ahn, 2012; Shukla et al, 2010), Europe (Aloupi et al, 2009; Heinrichs and Udluft, 1999), and Central and North America (Armienta et al, 2001; Ayotte et al, 2003; Boyle et al, 1998; Colman, 2011; Kim et al, 2011; Lipfert et al, 2006; Peters and Blum, 2003; Peters and Burkert, 2008; Pippin et al, 2006; Ryan et al, 2011; Yang et al, 2009), especially in rural areas without public water supply. These bedrock wells typically have low yields and supply small communities or individual households (Drew et al, 2001).…”

The Analysis of Spatial Distribution of Gifted Education Units in Seoul

“…이러한 GIS의 특징은 다양한 도 형자료와 속성자료를 가지고 있는 수많은 데이터 파일에서 필요한 도형이나 속성정보를 추 출하고 결합하여 복잡하고 종합적인 각종 정보를 분석⋅처리 할 수 있다는 것이다 (박노욱, 권병두, 2000). (김묘정, 최아현, 2008; 김호용, 김지숙, 이성호, 2012; 정건섭, 김성우, 이양원, 2012; 조성호, 박순호, 1996), 최적경로분석(양광식, 2011), 수배송관리 (김시곤, 김황배, 2002; 이희연, 임은선, 2001), 관광 루트분석 (오규식, 박경호, 1997), 응급의료 (김흥순, 정다운, 2010;이태식, 구지희, 1996;Kim et al, 2011;Kim, Galeano, Hull, & Miranda, 2008;Kim, Lauria, & Whittington, 2012), 재해 관리 (김지숙, 김호용, 이성호, 2014; 이사로, 김윤종, 민경덕, 2000), 정치 (박기호, 2000;Auchincloss et al, 2007;Hernández-Murillo, 2003;Sui & Hugill, 2002;Voss, Long, Hammer, & Friedman, 2006 …”