SREL Reprint #2112





Relationships between precipitation and surface water chemistry in three Carolina Bays

Robin Monegue Pickens and Charles H. Jagoe
University of Georgia, Savannah River Ecology Laboratory

Abstract: Samples of surface water and bulk precipitation were collected bi-weekly for more than 21/2 years at three Carolina bays along a 25 km transect located on the Savannah River Site, South Carolina, U.S.A. Carolina bays are freshwater wetlands, the most abundant lentic systems of natural origin on the southeastern US coastal plain. Precipitation chemistry was similar at all sites; mean pH was 4.56, and the major ions were H+, 34.7% of total cations, and SO4, 47.1% of total anions. H+ was positively correlated with SO4-- in precipitation, implying anthropogenic acids influence precipitation chemistry in this region. All three bays, Rainbow Bay (RB), Thunder Bay (TB), and Ellenton Bay (EB), contained soft (specific conductivity 5-9O µS/cm), acidic water (pH 4.0-5.9) with dissolved organic matter (DOM) from 4-60 mg/L. The major cations for RB, TB, and EB, respectively, were: Mg++ (31.6 % of total); Na+ (26 % of total); and Ca++ (30.8 % of total). DOM was the major anion for all bays, and SO4-- represented 14 to 28 % of all anions. H+ was not correlated with DOM or SO4-- in any of the three bays. In each bay, ionic concentrations varied over time. SO4-- concentrations were significantly higher in Rainbow Bay than Thunder Bay or Ellenton Bay, and H+ concentrations were significantly higher in Thunder Bay than in the other two bays. This suggests that different biogeochemical processes may influence pH and other chemical variables in each bay. Precipitation and shallow groundwater are dominant water sources for these bays, but for all three bays changes in surface water H+ were not directly correlated with precipitation loading of H+, NO3- or SO4-- . However, ratios of SO4-- :Cl- in all three bays and in precipitation were higher than would be expected if marine aerosols were the major SO4-- source, suggesting that atmospheric inputs of anthropogenic acids may influence bay chemistry.

SREL Reprint #2112

Pickens, R.M. and C.H. Jagoe. 1996. Relationships between precipitation and surface water chemistry in three Carolina bays. Archiv fur Hydrobiologie 137:187-209.

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