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PROSPECTIVE 180S04 INDICATOR FOR IDENTIFYING ELEVATED ARSENIC RELEASE AREAS IN GROUNDWATER: GOOSE RIVER AND NORTHPORT WATERSHEDS, MAINE
Citation:
Sidle*, W C. PROSPECTIVE 180S04 INDICATOR FOR IDENTIFYING ELEVATED ARSENIC RELEASE AREAS IN GROUNDWATER: GOOSE RIVER AND NORTHPORT WATERSHEDS, MAINE. Presented at WSWRD Peer Review, Cincinnati, OH, September 27 - 29, 2004.
Impact/Purpose:
To inform the public.
Description:
Naturally-occurring arsenic is the most abundant source of As to groundwater in this nation. In Maine the perfect arsenic storm exists for drinking water supplies since over 70% of homeowners depend on groundwater wells. Most of these wells are developed in granites with ubiquitous As-bearing sulfates. Further, fracture flow hydraulics dominate flows throughout the watersheds.
The discovery and development of an indicator to predict elevated As occurrences in Maine's watersheds was realized by examining the As oxidation potential of source areas and As release patterns. Current methodologies are dismissed, as none are consistent, in favor of the isotopic behavior of As-bearing sulfates. Parameters including dissolved oxygen, As3+/As5+,
Fe2+/Fe3+, and SO42- display very poor correlations with the abundances of total As in groundwater. Most importantly, fractionation events during oxidation influence 18OSO4. Testing in two watersheds (Goose River and Northport, Maine) indicates a direct correlation between elevated levels of As and 18OSO4: total As > MCL of 50 g L-1 with 18OSO4. > 10.0 o/oo VCDT and total As > MCL of 50 g L-1 with 18OSO4. > 6.0 o/oo VCDT, respectively.