EFFECT AND MECHANISM OF WASTE ROCK STACKING DURING SULFIDE METAL DEPOSIT MINING ON WATER ENVIRONMENT AND IMPLICATION FOR TREATMENT MEASURES

The metal sulfide oxidation in the waste rock results in a serious exceeding standard of acidity, SO₄^2- and heavy metals in surface water and groundwater. Previous studies on the oxidation mechanism of metal sulfide mostly focus on the laboratory experiment of a single mineral. However, the field situation is complex and inconsistent with the experiment. This paper analyzes the composition of rock samples(ore and waste rock) and hydrochemistry, trace elements, and ⁸⁷Sr/⁸⁶Sr in water samples from river, groundwater, and leachate of abandoned tailings pond. The paper discusses the influence and mechanisms of a lead-zinc mine waste rock on the actual water environment. The results show that the oxidation of metal sulfide caused serious pollution to the water environment. The river water is acidified, where the pH is as low as 2.38, the concentration of SO₄^2- and Zn, Pb, Ni, Mn, and Cd exceed the drinking water limit most seriously. The concentration is negatively correlated with pH. The main cause of river acidification is the oxidation of pyrite and pyrrhotite. They contribute most of SO₄^2- to the river. The sphalerite not only contributes a part of SO₄^2- to the river, but also is the main source of heavy metals. The ion concentrations in groundwater are lower than that of river water, and the pH is neutral. The pH of groundwater is higher than that of river water, which is mainly due to the dilution of groundwater in lateral mountains. The neutralization effect of silicate and carbonate on acid in the process of river water flow has great enlightenment value for the treatment of acid water. The understanding of the mechanism is of great significance for the prevention and control of waste rock pollution to water and soil environment. This study is of great significance for the prevention and control of waste rock on water pollution.