Heterogeneous arsenic enrichment in meta-sedimentary rocks in central Maine, United States.

Arsenic is enriched up to 28 times the average crustal abundance of 4.8 mg kg(-1) for meta-sedimentary rocks of two adjacent formations in central Maine, USA where groundwater in the bedrock aquifer frequently contains elevated As levels. The Waterville Formation contains higher arsenic concentrations (mean As 32.