Effects of urbanization on mercury deposition and accumulation in New England

• Hg loading was highest at urban sites.
• Elevated Hg loading did not correspond with elevated MeHg in sediment, water or fish.
• Hg loading was most important in regulating accumulation of MeHg in rural areas.
• Ecosystem sensitivity was most important in regulating MeHg in urban areas.
• Urbanization appeared to reduce Hg methylation rates and bioaccumulation.

We compare total mercury (HgT) loading and methylmercury (MeHg) accumulation in streams and lakes from an urbanized area (Boston, Massachusetts) to rural regions of southern New Hampshire and Maine. The maximum HgT loading, as indicated by HgT atmospheric deposition, HgT emissions, and sediment HgT concentrations, did not coincide with maximum MeHg concentrations in fish. Urbanized ecosystems were areas of high HgT loading but had low MeHg concentrations in fish. Controls on MeHg production and accumulation appeared to be related primarily to HgT loading in undeveloped areas, while ecosystem sensitivity to MeHg formation appeared to be more important in regulating accumulation of MeHg in the urban area.