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Assessing the Origin of Sulfate Deposition at the Hubbard Brook Experimental Forest
Author(s) -
Alewell C.,
Mitchell M. J.,
Likens G. E.,
Krouse R.
Publication year - 2000
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2000.00472425002900030011x
Subject(s) - precipitation , environmental science , deposition (geology) , atmospheric sciences , sulfate , biogeochemistry , stable isotope ratio , atmosphere (unit) , acid rain , fossil fuel , environmental chemistry , oceanography , geology , ecology , sediment , chemistry , meteorology , quantum mechanics , paleontology , physics , organic chemistry , biology
The geographical and chemical origin of SO 2− 4 deposition has become a concern, because anthropogenic S emissions have influenced the biogeochemistry of forested ecosystems and surface waters. Our aim was to evaluate the origin of SO 2− 4 in bulk precipitation at the Hubbard Brook Experimental Forest (HBEF), New Hampshire. We analyzed 26 years of archived bulk precipitation samples for sulfur stable isotopes. We compared the δ 34 S values with anthropogenic SO 2 emissions, the relative contribution of sea salt aerosols (as the SO − 4 /Na + ratio in precipitation), and temperature and solar radiation effects on the long‐term patterns of δ 34 S values. The long‐term pattern of δ 34 S values in bulk precipitation could be explained partly by the relative contribution of marine SO 2− 4 or solar radiation but not by temperature variation or anthropogenic SO 2 emissions. The high variability of the δ 34 S values of various fossil fuels makes it difficult to use stable S isotopes for identifying whether changing fossil fuel use is affecting the δ 34 S values in bulk precipitation. The seasonal pattern of δ 34 S values in bulk precipitation (significantly higher values in the winter than the summer) may be explained by the temperature dependence of the isotopic shift during SO 2− 4 formation in the atmosphere. A greater relative contribution of marine SO 2− 4 during the winter also may have contributed to the higher δ 34 S values in the winter. Previous investigations may have overestimated the role of biogenic emissions in affecting the δ 34 S pattern.