Sources and mixing of sulfate contamination in the water environment of a typical coal mining city, China: evidence from stable isotope characteristics.

To explore the sources and distribution characteristics of SO₄²⁻ in the surface waters of the Linhuan mining area in Huaibei, river and surface water samples in subsidence and mine drainage locations in the study area were collected at different times. The conventional hydrochemical indexes and the eigenvalues of sulfur and oxygen isotopes were tested and analyzed. The results suggested the following: (1) The SO₄²⁻ content showed seasonal changes: low-flow seasons > mid-flow seasons > high-flow seasons. (2) Based on δ³⁴S_SO4 and δ¹⁸O_SO4 isotope analyses, the main source of SO₄²⁻ was the dissolution of evaporite salt rocks in the stratum of the upstream area. The SO₄²⁻ in the subsidence area was mainly from the river water supply, mine drainage and coal gangue leaching. The high concentration of SO₄²⁻ in the mine drainage was mainly from the dissolution of evaporative salt rocks. (3) The calculation results of the ternary mixing model showed that the SO₄²⁻ in the subsidence area water was affected by mine drainage and gangue leaching to different degrees. The results showed that the sulfate contribution proportion of the river water source to the subsidence area water was 35.8–65.9%; the sulfate contribution proportion of the mine drainage source to the subsidence area water was 2.0–26.6%; and the sulfate contribution proportion of the gangue leaching end source ranged from 16.3% to 56.9%. Coal mining activities had an important impact on the sulfate in the subsidence area water. [ABSTRACT FROM AUTHOR]