The Longling Mengxing Zn Mining Area Hydrogeological Conditions And Groundwater Quality Analysis

MengXing Lead-Zinc Mine in Yunnan province is a large-scale metal sulphide deposits, founded in June 1958. After several expansion and renovation, there is a select field, a smelter and a tailings pond, meanwhile, mined-out area and the roadway inclined also been formed which made hydrogeological conditions become more complicated, water quality deteriorated, and finally the normal production and daily life has been affected. Therefore, we studied the hydro-geological conditions and water quality status of mining area.During the research, we evaluated groundwater quality on the mine area at the basic of collecting historical data, carrying out field survey in wet and dry seasons, and collecting ground water samples from the mine area, at last we obtained cognitions and research results as follow:1. The mine area is the eroded and denuded syncline landform to medium and low mountains. There less Izuis exposed on the surface, occurrence of stratigraphic is of the steep, the structure is medium to complex, fault fracture is developed. Hydrogeological units of the mine area is pertained to a complete karst groundwater equilibrium zone. Groundwater recharged mainly accept atmospheric precipitation, flowing into the river from south to, north west, the runoff is from the slow into a middle. Subprime hydrogeological units can be divided into the karst watershed and fissure watershed, with Devonian limestones and Silurian phyllite as boundary, the West is karst water zone and the east is fracture water zone. Mining activities Locates in fissure watershed zone of watershed area west of the surface slope, the aquifers involved of which are Silurian in the unified upper (S22) and the Silurian Commission under the previous paragraph (S12).2. Sorted 42 water samples collected, we classify analysis to water samples and water quality objectives with R and Q type factor methods, from which we find out that elements associated with poor in wet season, cation is negative correlation, water samples and elements in some water clustered less because groundwater and surface water wered mixed; in dry season, elements associated with good, cation is positive correlation and anion is negative correlation, water samples and elements in some water clustered more.3. We evaluate chemical data of the water sample by using the single factor method, the composite index method and the fuzzy mathematical method, from which we find out that in the mine area, pore groundwater be classified for water quality of poorer to poorest and and grade V, karst groundwater be classified for water quality of good to poorer and gradeⅢ～ V, and fissure water be classified for water quality of good to poorer to poorest and gradeⅡ-Ⅲ-Ⅴ. The overall water quality in the area is too poorer, that is Inappropriate to life and drinking for humanity, instead of farmland irrigation.4. According to the out of the dew point of surface and ground water, underground mine water chemistry characteristics of the tunnel, hydro-geological conditions of the mine area and hydro-geological of the tunnel, we analyzed factors effected groundwater quality in mine area, such as aquifer lithology, sampling date, runoff path and circulating cycle of the groundwater, they are with degree of difference.5. Through the analysis of water quality assessment results, harmful elements and the surrounding geology, production and living conditions, we find out that pore water is polluted more seriously due to human life and livestock Activities, especially nitrogen element overweight and PH value is grossly lower than normal. Fissure groundwater have been impacte seriously by producing in mining area, especially tailings water sulfate concentrations is below part exceeds bid badly.6. Mining is the lowest elevation of 580 meters the middle, future Roadway will reach 200 m elevation, and large water inflow of Roadway years to come. We do the trend analysis to the water quality, finding that overall quality is good, could satisfy the quality standards of farmland irrigation and drinking after the physical chemical treatment, and generating economic and ecological benefits.