I. Abstract

Reductions in acid deposition have the potential to improve the condition of Maryland surface waters, particularly in small streams most susceptible to acidification. To evaluate changes in stream chemistry associated with implementation of the 1990 Clean Air Act Amendments Title IV, Phase I (CAAA), acid deposition patterns determined from a regional deposition model were compared to critical load (the amount of deposition that harms indicator species) estimates and results from the 1995-97 Maryland Biological Stream Survey. Critical loads were estimated from modeled source/receptor relationships at 73 streams in the state using resident fish species as indicator organisms. The results of this analysis suggest that critical loads continue to be exceeded in some areas of the state despite reductions in sulfate deposition. Above-average precipitation amounts in 1996 contributed to acid deposition in excess of critical loads in a number of sensitive areas. Fish communities in affected areas exhibited low species richness and abundance. Although Phase I results are encouraging, it is unlikely that complete implementation of CAAA Title IV will eliminate the acidification problems in all Maryland streams.

Return to main page

Continue to Background