TRACKING MERCURY

Without knowing where mercury emitted from power plants and other facilities ends up, it is hard to know how best to minimize such pollution. To rectify this problem, Sen. Susan Collins last week introduced legislation to create a mercury monitoring system. The information collected by the system will allow lawmakers, in the absence of action from the Environmental Protection Agency, to write rules that will lower mercury emissions while also addressing “hot spots,” localized areas with high levels of mercury in the soil and water.

When the Environmental Protection Agency adopted a rule in 2005 that aimed to reduce mercury pollution through a cap and trade system, the agency downplayed the idea that the toxic metal is often deposited – in high concentrations – near its source. It relied instead on a computer model that was not vetted by outside experts.

According to the EPA, less than half of all mercury deposition within the United States comes from domestic sources. However, the agency adds, there are regional differences and U.S. sources represent a greater fraction of the total deposition in parts of the Northeast because of the direction of the prevailing winds.

Eleven scientists, including several from the BioDiversity Research Institute in Gorham, took a closer look and found that this was misleading. Their study, published earlier this year in the journal BioScience, found as many as 14 mercury “hot spots” in the Northeast, one with mercury levels five times higher than previously estimated by the EPA. This research adds to evidence that the EPA rule is inadequate and should be replaced with strict limits on how much mercury can be emitted.

It also shows that the monitoring program proposed by Sen. Collins is needed so that real data, not computer modeling as the EPA used for the Clean Air Mercury Rule, is the basis for pollution reduction measures.

The study, which was organized by the Hubbard Brook Research Foundation in New Hampshire, examined 7,300 samples from fish, loons and other wildlife from lakes and reservoirs from New York to Nova Scotia. Samples from 14 locations had unusually high mercury levels. One hot spot was in central Maine, at the headwaters of the Androscoggin and Kennebec rivers. Scientists believe the drawdown of water from reservoirs along the rivers concentrated the mercury that was deposited there, raising the level in some locations to four times higher than the EPA deems acceptable.

The scientists closely examined a hot spot along the Merrimack River in southern New Hampshire and northern Massachusetts near four coal-fired power plants. They found mercury depositions in some locations nearly five times what the EPA predicted for the area. They estimate that up to two-thirds of the mercury was from local sources.

A mercury monitoring system will help clarify the contradictions between the EPA and BioScience studies. By clarifying where mercury comes from and where it ends up, regulators and lawmakers can make better decisions about how and where to require reductions.