Heavy metal contamination from historic mining in upland soil and estuarine sediments of Egypt Bay, Maine, USA

Concentrations of Cd, Cu, Pb and Zn in sediments of Egypt Bay in Hancock County, Maine, are elevated above background levels. The source of the contamination is Cu mining that occurred in the uplands adjacent to Egypt Stream between 1877 and 1885. Egypt Stream is a tributary to Egypt Bay. Egypt Bay is part of the Taunton Bay estuary system. The Hagan Mine was one of the mines extracting metals from the sulfide deposits in Downeast Maine north of Penobscot Bay. Metal concentrations were determined using ICP-AES after sample digestion with nitric acid. Soil collected from the coarse textured mine tailings pile contained elevated concentrations of Cd, Cu, Pb and Zn, but the majority of the surface soils at the Hagan Mine site were not contaminated. Estuary sediments from the surface to 100 cm depth were collected in four locations within Egypt Bay. Below 40 cm, metal concentrations in sediments were similar to those in uncontaminated upland soils. Metal concentrations in the estuary sediments between the surface and 26 cm were above background levels. According to 210Pb dating, the sediment at 26–34 cm depth was likely to have been deposited at the time the historic mines were in operation. Concentrations of Cd, Cu, Pb, and Zn in sediment from the 32–34 cm depth interval are similar to concentrations in the upland soil sample from the mine tailings pile. Elevated Pb concentrations in sediments from the surface to 24 cm are from atmospheric Pb deposition from anthropogenic sources. Sediment in the top 10 cm of the estuary has been mixed both by the polychaete worm Nereis virens and by those harvesting the worms for sale as fish bait.