| 摘 要： |
Pyrite oxidation and sedimentary sulfate dissolution are the primary components of riverine sulfate (SO42-) and are predominant in global SO42- flux into the ocean. However, the proportions of anthropogenic SO42- inputs have been unclear, and their tempo-spatial variations due to human activities have been unknown. Thus, field work was conducted in a spatially heterogeneous human-affected area of the Yihe River Basin (YRB) during a wet year (2010) and drought years (2017/2018). Dual sulfate isotopes (delta S-34-SO42- and delta O-18-SO42-) and Bayesian isotope mixing models were used to calculate the variable anthropogenic SO42- inputs and elucidate their temporal impacts on riverine SO42- flux. The results of the mixing models indicated acid mine drainage (AMD) contributions increased from 56.1% to 83.1% of upstream sulfate and slightly decreased from 46.3% to 44.0% of midstream sulfate in 2010 and 2017/2018, respectively, in the Yihe River Basin. The higher upstream contribution was due to extensive metal-sulfide-bearing mine drainage. Sewage-derived SO42- and fertilizer-derived SO42- inputs in the lower reaches had dramatically altered SO42- concentrations and delta S-34-SO42- and delta O-18-SO42- values. Due to climate change, the water flow discharge decreased by about 70% between 2010 and 2017/2018, but the riverine sulfate flux was reduced by only about 58%. The non-proportional increases in anthropogenic sulfate inputs led to decreases in the flow-weighted average values of delta S-34-SO42- and delta O-18-SO42- from 10.3 parts per thousand to 9.9 parts per thousand and from 6.1 parts per thousand to 4.4 parts per thousand, respectively. These outcomes confirm that anthropogenic SO42- inputs from acid mine drainage (AMD) have increased, but sewage effluents SO42- inputs have decreased. |
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