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

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• 作者：Qiang Yang ; Hun Bok Jung ; Charles W. Culbertson ; Robert G. Marvinney ; Marc C. Loiselle ; Daniel B. Locke ; Heidi Cheek ; Hilary Thibodeau ; Yan Zheng
• 刊名：Environmental Science & Technology
• 出版年：2009
• 出版时间：April 15, 2009
• 年：2009
• 卷：43
• 期：8
• 页码：2714-2719
• 全文大小：242K
• 年卷期：v.43,no.8(April 15, 2009)
• ISSN：1520-5851

文摘

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, and 31% of the sampled wells have arsenic concentrations >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 four 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.