Trends and Patterns in Lake Acidification in the State of Vermont: Evidence fromthe Long-Term Monitoring Project

摘要

Twenty-four low acid neutralizing capacity (ANC) lakes in Vermont have beenmonitored since 1980 to characterize their chemical variability and to determine if they exhibit temporal trends in acid/base chemistry. Many of the lakes exhibit significant decreasing trends in SO4(2-) and base cation (C(sub B)) concentrations, but few exhibit significant changes in pH or ANC. An examination of all trend results suggests a tendency for ANC and pH values in these lakes to be increasing, but either the changes are too small, or the number of observations too small, for these trends to be significant. Data from these lakes suggest that the primary responses of surface waters in this region to declining rates of SO4(2-) deposition are decreases in SO4(2-) concentrations and rates of cation leaching from watershed soils. Decreasing rates of C(sub B) deposition may combine with lower rates of cation leaching to produce declines in C(sub B) that are very similar to measured declines in SO4(2-) concentration. Vermont lakes exhibit their lowest ANC values in spring, attributable, for the most part, to dilution of C(sub B) concentrations during spring snow melt. (Copyright (c) 1993 Kluwer Academic Publishers.)