Evaluating sulfur dynamics during storm events for three watersheds in the northeastern USA: a combined hydrological, chemical and isotopic approach

Concerns related to climate change have resulted in an increasing interest in the importance of hydrological events such as droughts in affecting biogeochemical reponses of watersheds. The effects of an unusually dry summer in 2002 had a marked impact on the biogeochemistry of three watersheds in the north-eastern USA. chemical, isotopic and hydrological responses with particular emphasis on S dynamics were evaluated for Archer Creek (New York), Sleepers River (Vermont) and cone Pond (New Hampshire) watersheds. From 1 August to 14 September 2002 all three watersheds had very low precipitation (48 to 69 mm) resulting in either very low or no discharge (mean 0.015 0.15 and 0.000 mm day(-1) for substantial increase in precipitation totals (212.246 and 198 mm, respectively) with increased discharge. Archer Creek was characterized by a large range of SO42 concentrations (152 to 389 mu(3)q L-1, mean = 273 mu cq L-1) and also exhibited the greatest range in delta S-34 values of SO42- (-1.4 to 8.8%). Sleepers River's SO42- concentrations ranged form 136 to 243 mu eq L-1 (mean = 167 mu eq L-1) and and delta S-34 values of SO42- ranged form 4.0 to 9.0 %. Cone Pond's SO42- concentrations (126-187 mu eq L-1 mean = 154 mu eq L-1) and delta S-34 values (2.4 to 4.3 %). Sleepers River's SO42- concentrations ranged from 136 to 243 mu eq L-1 delta O-18-SO42- values for Archer Creed and cone Pond were similar (3.0 to 8.9% mean = 2.5). The diffference in Sleepers River chemical and isotopic responses was attributed to weathering reactions contributing SO42-. For Archer Creek wetland areas containing previously reduced S compounds that were reoxidized to SO42- probably provided a substantial source of S. Cone Pond had limited internal S sources and less chaemical or isotopic response to storms. Differences among the three watersheds in S biogeochemical responses during these storm events were attributed to differences in S mineral weathering contributions, hydrological pathways and landscape features. Further evaluations of differences and similarities in biogeochemical and hydrological responses among watersheds are needed to predict the impacts of climate change. copyright (C) 2008 john Wiley & Sons. Ltd.