Distribution of Arsenic in Presque Isle State Park Pond Sediments

A study of arsenic in pond sediments on the Presque Isle peninsula, Erie, PA, was conducted in 2000 and 2001 by Murnoch (2002) due to concerns expressed by citizens and various local officials. Samples of pond and lagoon sediments were collected at thirteen primary sites and additional reference sites for analysis of arsenic content during the fall, 2000, and again in spring, 2001. The probable effect concentration (PEC) for arsenic of 33.0 mg/kg-DW, an indication of the concentration above which adverse impacts on benthic organisms are expected to occur, was exceeded in the surface sediments at all 13 primary sites during fall sampling and in all but one site during spring sampling, with concentrations as high as 393 mg/kg-DW measured. For deeper sediments, the PEC was exceeded in the fall at nine sites and in the spring at six sites. Surface sediments contained more arsenic than did deeper sediments. These differences were more pronounced in the spring samples than in the fall samples. There was a general trend, with numerous exceptions, for sites closer to Gull Point (the geologically ‘new’ end of the peninsula) to have lower arsenic levels. While the source of the arsenic in the sediments of Presque Isle is unknown, these high levels are likely due to natural processes that, over time, have resulted in an enrichment of arsenic in surface sediments. A possible mechanism for this enrichment is proposed. This study has not attempted to document the risk to the ecosystem associated with elevated arsenic concentrations, but it is reasonable to speculate that there could be an adverse impact on some organisms.