Evaluating the effect of the Clean Air Act on lake and stream chemistry in the northeastern US

Project Summary

Objectives - The proposed research is part of the University of Maine’s program to address scientific uncertainty relating to surface water and watershed acidification.  Our goals and methods are hierarchical, ranging from site-specific data to regional statistical surveys.  The objectives are to:

1. determine the changes and trends in aquatic chemistry for defined sub-populations and sites that are known to be susceptible to acidification or recovery,
2. evaluate the relationships between surface water and precipitation chemistry using site specific deposition data, and regional NADP data, and
3. characterize the effectiveness of the Clean Air Act (and amendments) in meeting its goals of reducing acidification of surface waters and improving biologically-relevant chemistry in the northeastern US.

Approach - The schedule of tasks ranges from weekly to annual. We will evaluate chemistry on a weekly basis year-round at the small watershed-scale at BBWM, weekly during the spring melt period at RLTM lakes outlets, quarterly in LTM and RLTM lakes, and during an annual index period for the HELM and TIME lakes. The specific tasks are to:

1. examine the patterns of acidification and recovery in the experimental watershed project at the Bear Brook Watershed in Maine (BBWM), originally part of the EPA Watershed Manipulation Project,
2. continue the 17 year chemistry record for selected lakes in Maine which were part of the original EPA Long Term Monitoring Program (LTM),
3. expand the scope of LTM using the EPA Regionalized Long Term Monitoring Lakes which have a broader distribution of chemistry to match the regional chemical characteristics,
4. provide an estimate of seasonal chemical extremes that occur in these RLTM lakes,
5. re-sample a subset of the high elevation lakes, surveys of which in 1986-88 revealed the most acidified lakes in Maine, and
6. provide a statistical regional estimate of chemical changes using lakes in the EPA Temporally Integrated Monitoring of Ecosystems (TIME) program in New England and the Adirondack region.

The annual schedule and scope of work is summarized below:

These project components provide a statistical framework for inferring regional chemical patterns using TIME and RLTM. The long term records of LTM, RLTM, HELM and BBWM provide seasonal and annual variability data that defines long term response.

Expected Results - This information is fundamental for federal agencies to meet the Congressional mandate in the Clean Air Act Amendments (CAAA) to ascertain trends in ecological response, and to determine the effectiveness of the CAAA in influencing these trends. The highly appropriate combination of site-specific data within the regional context will provide for the recognition and under­standing of declining SO₄, base cation depletion, and changes in N-saturation or DOC contributions to acid-base status.