Spatial Pattern of Groundwater Arsenic Occurrence and Association with Bedrock Geology in Greater Augusta, Maine

Abstract

In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (100-101 km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed. 31% of the sampled wells have arsenic >10 μg/L. The probability of [As] exceeding 10 μg/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (~40%). This probability differs significantly (p<0.001) from those in the Silurian-Ordovician sandstone (24%), the Devonian granite (15%) and the Ordovician-Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium and high arsenic occurrences in 4 cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (~1135 km2) are at risk of exposure to >10 μg/L arsenic in groundwater.

Influences on domestic well water testing behavior in a Central Maine area with frequent groundwater arsenic occurrence

“…Our other survey study that followed up with 256 households who had all received test results of As >10 μg/L between 2006–2010 (Flanagan et al, this issue) found similar rates of forgetting; 31% did not remember their As test results and 14% recalled incorrectly, more often underestimating their As level. In addition to As (Yang et al, 2009; Nielsen et al, 2010), state lab testing and Columbia University testing have shown that the greater-Augusta area of Central Maine has high Rn occurrence along with other natural contaminants in the groundwater. (Yang et al, 2014), so it is concerning to find that 22% of households in this area may have never tested their well water for anything.…”

Dissemination of well water arsenic results to homeowners in Central Maine: Influences on mitigation behavior and continued risks for exposure

“…Between 2006 and 2011 the Columbia University Superfund Research Program (SRP) and the Maine Geological Survey (MGS) tested 1,428 domestic well water samples in 17 towns encompassing over 1500 km 2 (Yang et al, 2009; Yang, 2010). Over 95% of these samples were collected from drilled wells, which are at higher risk for As (Ayotte et al, 2003).…”

Bioavailability and risk assessment of arsenic in surface sediments of the Yangtze River estuary

“…Arsenic has acute and chronic toxic and carcinogenic effects on aquatic organisms and humans (Oremland and Stolz, 2003). Elevated levels of arsenic present in the environment have caused public concern (Yang et al, 2009). Arsenic is ubiquitous in groundwater, soil and sediments as a result of natural processes including mineral weathering, dissolution and geothermal activities (Manning et al, 1998;Yamamura et al, 2013).…”