Acid Rain in the Adirondacks
By Mandi Norton-Westbrook (‘07)

Professor Bob Newton from the Geology department has a particular interest in the effect of acid rain in the Adirondack mountain environment. As one of his earlier projects, Professor Newton looked at the effects of acid rain on lakes in the Adirondacks. The project focused on three lakes: one acidic, one neutral, and one intermediate in pH. All three lakes received the same level of acidity from the rain and had the same bedrock, vegetation, and soil. Professor Newton aimed to discover why and how the lakes had different pH levels given that their surrounding environments were so similar. After looking at the glacial geology of the different watersheds he found that the watershed of the neutral lake had a thick layer of unconsolidated thick sediment while the watershed of the acidic lake had a thin layer. It appeared that the neutral lake watershed's thick layer of glacial sediment allowed for the acid rain to infiltrate the soil and enter the groundwater reservoir where the acid rain was neutralized by chemical reactions with minerals in the sediments. Conversely, in the acidic lake watershed, most of the precipitation became runoff and consequently never infiltrated into a groundwater reservoir. Since the acid rainwater of the acidic lake watershed did not have the opportunity to react with the soil, its pH remained low.

The project team members created a computer program to model the effects of acid rain on the lakes, and to evaluate mitigation strategies like lake and watershed liming. Early mitigation strategies involved adding lime directly to acid lakes. However, this produced only a short-term change in pH, usually lasting only a year or so. Furthermore, although game fish like trout could be reintroduced into a limed lake, they could not reproduce there as they depend on upwelling groundwater to protect their eggs from sediment deposited over the winter. Acid lakes are acidic precisely because they have no groundwater inputs.

The research team decided to approach liming differently. Instead of liming the lake directly, they distributed 1,000 tons of lime throughout the watershed. The acid rain was neutralized by this lime as it moved across the forest floor. This type of watershed treatment had the added benefit of neutralizing tributary streams before they enter the lake. Fish were then able to migrate into these streams to spawn. The current in the streams keeps the fish eggs sediment free throughout the winter resulting in successful reproduction. This watershed liming experiment has kept the lake non-acid for 15 years and a small population of trout continues to survive and reproduce. Model predictions suggest the lake will continue to be non-acid for over 50 years.

Following his interest on the effects of acid rain on surface water acidification, Professor Newton became interested in problems associated with mercury contamination in the Adirondacks. A number of lakes in the region contain populations of mercury-contaminated fish, causing the government to post warnings, which hurt local fishing communities. Strangely, mercury concentrations in the water are low. Consequently, Professor Newton, together with a research team, formulated a hypothesis explaining how mercury might become concentrated in the fish.

Atmospheric deposition of trace amounts of mercury is derived, in part, from coal burning power plants and municipal incinerators. This mercury is deposited in the watershed and some is transported by streams and groundwater. Stream-side riparian wetlands act as natural filters and accumulate this mercury. Groundwaters under wetlands lack oxygen; a condition which supports populations of sulfur-reducing bacteria. These bacteria, in turn, convert much of the mercury in the wetland to methyl mercury, a highly biologically active form. Groundwater then moves the methyl mercury to the stream where it is then spread throughout the surface water system and bio-concentrated within the food chain. This leads to high mercury concentrations in fish and other animals, like loons, that feed on fish.

This project recently received another grant from the Environmental Protection Agency which will allow them to test this hypothesis at twelve other lakes and their watersheds.

Aside from this research, Professor Newton is also a member of the Barnes Aquifer Protection Advisory Committee. He and his students have completed a number of projects involving groundwater issues in the Easthampton area, ranging from finding sites for new municipal wells for the City of Easthampton, which relies on groundwater for all its municipal water needs, to examining the migration of trichloroethylene from an illegal dumping ground in Holyoke to wells in Easthampton. Professor Newton cites the overdevelopment of land in recharge areas as the greatest long-term threat to the aquifer.

Professor Newton integrates his research interests into his classes. This Fall, he involved his Groundwater Geology (GEO 309) class with his work on the Barnes Aquifer. Next term, he will teach Geomorphology (GEO 251), a class which focuses on how landscapes are formed and uses the emerging technology of Geographic Information Systems (GIS).

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