Concentrations of sulfate and δ-values of sulfate, (δ^34SO_4)_pw, dissolved in pore waters were measured from the sediment cores of the two different marine environments: deep northeast Pacific (ST-1) and coastal Kyunggi Bay of Yellow Sea (ST-2). Sulfate concentration in pore waters decreases with depth at both cores, reflecting sulfate reduction in the sediment columms. However, much higher gradient of pore water sulfate at ST-2 than ST-1 indicates more rapid sulfate reduction at ST-2 because of high sedimentation rate at the coastal area compared to the deep-sea. The measured 6-values, (δ^34SO_4)_pw, follow extremely well the predicted trend of the Rayleigh fractionation equation. The range of 26.7‰ to 61.3‰ at the coastal core ST-2 is not so great as that of 32.4‰ to 97.8‰ at the deep-sea core ST-1. Despite greater gradient of pore water sulfate at ST-2, the δ-values become lower than those of the deepsea core ST-1. This inverse relation between the S-values and the gradients of pore water sulfate could be explained by the combination of the two subsequent factors: the kinetic effect by which the residual pore water sulfate becomes progressively enriched with respect to the heavy isotope of ^34S as sulfate reduction proceeds, and the intrinsic formulation effect of the Rayleigh fractionation equation in which the greater becomes the fractionation factor, the more diminished values of (δ^34SO_4)_pw are predicted.

• Myung Woo Han | 한명우