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

✍ Scribed by Myron J. Mitchell; Scott W. Bailey; James B. Shanley; Bernhard Mayer

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 351 KB
• Volume: 22
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/hyp.7033

✦ Synopsis

Concerns related to climate change have resulted in an increasing interest in the importance of hydrological events such as droughts in affecting biogeochemical responses 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 0Ð015, 0Ð15 and 0Ð000 mm day 1 for Archer Creek, Sleepers River and Cone Pond, respectively). From 15 September to 31 October 2002, there was a substantial increase in precipitation totals (212, 246 and 198 mm, respectively) with increased discharge. Archer Creek was characterized by a large range of SO 4 2 concentrations (152 to 389 µeq L 1 , mean D 273 µeq L 1 ) and also exhibited the greatest range in υ 34 S values of SO 4 2 ( 1Ð4 to 8Ð8 ‰). Sleepers River's SO 4 2 concentrations ranged from 136 to 243 µeq L 1 (mean D 167 µeq L 1 ) and υ 34 S values of SO 4 2 ranged from 4Ð0 to 9Ð0 ‰. Cone Pond's SO 4 2 concentrations (126-187 µeq L 1 , mean D 154 µeq L 1 ) and υ 34 S values (2Ð4 to 4Ð3 ‰) had the smallest ranges of the three watersheds. The range and mean of υ 18 O-SO 4 2 values for Archer Creek and Cone Pond were similar (3Ð0 to 8Ð9 ‰, mean D 4Ð5 ‰; 3Ð9 to 6Ð3 ‰, mean D 4Ð9 ‰; respectively) while υ 18 O-SO 4

2 values for Sleepers River covered a larger range with a lower mean (1Ð2 to 10Ð0 ‰, mean D 2Ð5). The difference in Sleepers River chemical and isotopic responses was attributed to weathering reactions contributing SO 4 2 . For Archer Creek wetland areas containing previously reduced S compounds that were reoxidized to SO 4 2 probably provided a substantial source of S. Cone Pond had limited internal S sources and less chemical 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