FACTORS AFFECTING STREAMWATER CHEMISTRY IN THE GREAT-SMOKY-MOUNTAINS,USA

The Great Smoky Mountains in the southeastern U.S. receive high total atmospheric deposition of sulphur and nitrogen (N) and contain large a reas of shallow, poorly buffered soils. Results from extensive surveys conducted in October 1993 and March 1994 showed that stream pH values were near or below 5.5 and Acid Neutralizing Capacity (ANC) was below 50 mu eqL(-1) at high elevations. Mechanisms of acidification varies among stream systems in the study. We classified each study catchment into one of five water quality districts based upon within-basin eleva tional gradients of streamwater quality. Geologic factors, cf. the pre sence of calcareous or pyritic bedrock types exhibited a major influen ce on water quality and within-basin elevational gradients. Atmospheri c deposition is an important factor affecting water quality at high el evations in all districts. Nitrate was the dominant strong acid anion in streamwater in many catchments, particularly at high elevation and especially in basins draining old growth forests. Most high elevation catchments appear to be N saturated. Continued high atmospheric loadin gs of N will likely spread N saturation of catchments downslope into a reas where second growth forests are now maturing. Stream sulphate con centrations were lower than expected at higher elevations and may be r elated to the N saturation status of these systems.