Responses of streams in central Appalachian Mountain region to reduced acidic deposition—Comparisons with other regions in North America and Europe

Data from 5 wet deposition stations and 21 streams during 1980–2006 were analyzed to investigate chemical responses of streams to reduced acidic deposition in the central Appalachian Mountain region of West Virginia, USA. Wet deposition of acidic anions (i.e., sulfate, nitrate, and chloride) and hydrogen ions decreased significantly during the studied time period. Stream sulfate showed a delayed response to the reduced acidic deposition, and showed a decrease in the 2000s (− 5.54 µeq L− 1 yr− 1) and the whole period (− 0.49 µeq L− 1 yr− 1). No significant trend of stream nitrate + nitrite and chloride was observed. Stream alkalinity increased in the 1990s (+ 23.33 µeq L− 1 yr− 1) and the whole period (+ 7.26 µeq L− 1 yr− 1). Stream hydrogen ions decreased in the 1990s (− 0.002 µeq L− 1 yr− 1), 2000s (− 0.001 µeq L− 1 yr− 1), and the whole period (− 0.001 µeq L− 1 yr− 1). Compared with most acidic streams and lakes in the United States and Europe, a lower decreasing rate of hydrogen ions and higher increasing rate of alkalinity were observed in the alkaline West Virginian streams in the 1990s. However, due to their initial negative or zero alkalinity values, those acidic streams showed a higher percent increase in alkalinity than that in the alkaline West Virginian streams (from 800 µeq L− 1 yr− 1 to 1200 µeq L− 1 yr− 1). Total aluminum in the West Virginian streams decreased in the 1990s (− 0.67 µmol L− 1 yr− 1) and the whole period (− 0.22 µmol L− 1 yr− 1). The current study advanced our understanding of streams' responses to the reduced acidic deposition in the Mid-Appalachians since the passage of the 1970 and 1990 Amendments to the United States Clean Air Act (US CAAA).