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Outline
To investigate the impact of underground paste backfill on the groundwater environment in a lead-zinc mine, the variation laws of pH and electrical conductivity of soaking solution and leaching solution affected by backfill mass concentration and cement-sand ratio were systematically examined by carried out backfill soaking and leaching tests. The results show that the electrical conductivity of the soaking solution and leaching solution exhibits a trend of first increasing and then decreasing over time. When the cement-sand ratios are 1∶4, 1∶10 and 1∶20, the maximum electrical conductivity values of the soaking solution are 2 050 μS/cm, 1 910 μS/cm and 1 220 μS/cm respectively. Meanwhile, the decreasing rates of pH of the leaching solution are 0.11 d-1, 0.12 d-1 and 0.18 d-1 in the first 14 days, and 0.08 d-1, 0.06 d-1 and 0.03 d-1 in the subsequent 14 days. This indicates that the higher the cement-sand ratio, the smaller the pH decrease range of the soaking solution, the higher the maximum electrical conductivity value, the slower the pH decreasing rate of the leaching solution in the early stage, and the faster the decreasing rate in the later stage. The mass concentration has a relatively minor effect on the variation of pH and electrical conductivity of the soaking solution and leaching solution over time. The leaching behavior of toxic ions is jointly determined by the adsorption of hydration products and the effect of pore structure, and the early stage is dominated by hydration reactions while carbonation reactions exert a more prominent influence in the later stage. The research results show that the concentration of heavy metal ions released by the backfill is far lower than the allowable values of relevant national standard, indicating that this paste backfill scheme has favorable environmental protection performance.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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