Abstract |
Temporal trends in acid-base chemistry are reported for surface waters in 6 regions of the United States. The lakes and streams are low acid neutralizing capacity (ANC), dilute systems, selected to represent acid-sensitive aquatic resources in the 6 regions. The predominant trends observed were decreases in lake and stream SO4(2-) concentrations in sites east of the Mississippi River, and increases in NO3(-) in the Adirondack lake and Catskill stream sites (both located in eastern New York State). Correlations of trend results from all sites with other factors indicated that trends in precipitation volume were highly correlated with the observed trend patterns. From the surface water trend results, three distinct clusters were identified that corresponded to three trend patterns: 'dilution', recovery', and 'acidification', which were distributed across the Long-Term Monitoring (LTM) regions with no particular geographic patterns. (Copyright (c) 1993 Kluwer Academic Publishers.) |