Hydrogeochemical Characteristics and Quality Assessment of Mine Water in Coalfield Area, Guizhou Province, Southwest China

Study of geochemical features of soils on the territory of an abandoned coal mining area using geoinformation technologies

The article describes the results of a study of the geochemical features of soils on the territory of an abandoned mining area. The Kizel coal basin (Russia) is of particular interest for studying the consequences of technogenic and post-technogenic transformation of the natural environment. The study of the soil as a deposit medium made it possible to identify geochemical indicators of the negative impact. Such a detailed study of the distribution of chemical elements in this area was conducted for the first time. Geoinformation system and maps with interpolation were created to study the spatial distribution of metals and metalloids in soils. Umbric Retisols Abruptic and Haplic Retisols Abruptic soils are common in the territory. Sampling for geochemical testing was carried out from two horizons: humus and podzolic. Sampling from two depths made it possible to identify elements that continue to be contaminated at the time of the study. A total of 103 sample plots were established in the study area. The results obtained were compared with the background of the natural region of the Western Urals to identify the contribution of technogenesis. As a result, the coefficients of concentration and dispersion of chemical elements were calculated. Due to this, elements were identified, the accumulation of which occurs on the territory of the Kizelovsky coal basin. To identify the current and accumulated pollution, the ratio between the humus and podzolic horizons was calculated. As a result, it was found that at the moment in the humus horizon in some areas there is a high accumulation of Co, Mn, Ni and Sr. The geochemical series of the territory for the humus and podzolic horizons was obtained: Fe > Ti > Mn > Sr > Cr > V > Zn > Ni > Co > Pb > As. Data on the geochemical specificity of the territory of the Kizel coal basin have been obtained. The created geoinformation database reflects the physical and chemical properties of soils, metals and metalloids content, dispersion and accumulation coefficients, coefficients of the ratio of the humus and podzolic horizon. Based on it, it is possible to obtain data on the geochemical features of the territory, geoecological characteristics, spatial distribution of metals and metalloids and identification of pollution sources. Co (24 ± 2.8 mg/kg), Mn (1100 ± 155 mg/kg), Ni (69 ± 9.3 mg/kg), As (10 ± 3.5 mg/kg), Cr (178 ± 20 mg/kg), Zn (80 ± 7.8 mg/kg) and Sr (221 ± 26 mg/kg) accumulate in the humus horizon. Co (24 ± 1.8 mg/kg), Mn (1000 ± 103 mg/kg), Ni (60 ± 6.4 mg/kg) and Cr (153 ± 15.2 mg/kg) accumulate in the podzolic horizon.

The non-coevolution of DIC and alkalinity and the CO2 degassing in a karst river affected by acid mine drainage in Southwest China

Dissolved inorganic carbon (DIC) in mine water generated during coal mining is a large and potential source of atmospheric CO2, however its geochemical behaviors under the influence of AMD in relation to CO2 degassing and carbonate buffering are not well known. In this study, water temperature, pH, DO, alkalinity, Ca2+ concentration, and the carbon isotope of DIC were measured monthly from November 2020 to November 2021 and carbonate chemistry and CO2 emission flux were calculated to reveal the processes of DIC evolution and CO2 degassing from the Chetian River draining a karst region, which is materially affected by the input of large quantities of AMD. The results showed that carbonate erosion, the mineralization of terrestrial organic matter, and domestic sewage input are all identified to contribute DIC to different degrees to the river. Throughout the year, the Chetian River undergoes high-intensity CO2 degassing, which is dominated by HCO3--neutralized degassing and proton-enhanced degassing in different reaches. The pCO2 in the river under the influence of AMD is as high as 237,482 μatm, while the F-CO2 approaches 316.9 g C m-2 d-1. Meanwhile, the carbonate system in the downstream karst river buffers an average of 85.2 % of DIC release at the river's outlet. The input of AMD significantly altered the carbon cycle of the surface watershed in the headwaters of tributaries, and greatly enhanced the release of CO2 from surface water to the atmosphere; meanwhile, the buffering of carbonates on acidity in the water of main streams causes pCO2 to rapidly reduce over a short distance. Obviously, the carbon emission effect generated by the interaction between AMD and carbonate mainly occurs in the tributary water system. Considering the huge amount of AMD worldwide, this large potential source of atmospheric CO2 requires a specific and precise quantitative analysis based on actual observations.

Practical application for legacy acid mine drainage (AMD) prevention and treatment technologies in karst-dominated regions: A case study

Acid mine drainage (AMD) from abandoned mines in karst-dominated regions in southwestern China was causing contamination of groundwater and surface streams. To avert the unwise decisions of "pollution first before treatment" during pre-mining, mid-mining and post-mining activities, this paper proposes a contaminant migration prevention technical framework covering 4 comprehensive processes. The formation mechanism of spring pollution, engineering remediation processes and contamination treatment effects were described in Longdong Spring. In 2018, the Longdong Spring water had Fe 33.83 mg/L and Mn 3.60 mg/L, exceeding the Chinese surface water standard (0.3 mg/L and 0.1 mg/L in GB 3838-2002) by 112 and 36 times, respectively. In 2020, after grout blocking, in situ treatment and wetland remediation, the highest Fe was 4.5 mg/L in a short period, and the spring water pollution days in this year were 42 days compared with the previous 320 spring water pollution days in 2018. In 2021, two years of remediation with the implementation of terminal remediation wetlands, the Fe was less than 0.03 mg/L compared with the previous 33.83 mg/L, and the water quality reached water standard (less than 0.3 mg/L). At present, Longdong Spring has become one of the most beautiful natural local landscapes.

Research on Mine Water Dispatching Mode Based on Maximization of Reuse Rate

Coal mining not only produces a large amount of mine water but also may cause water pollution. Therefore, economic treatment and efficient reuse of mine water are the main research directions of the mine area at present, and the realization of optimal dispatching and efficient reuse of mine water is an urgent problem to be solved. Based on the Na Lin mining area as an example, based on maximizing the reuse rate of mine water, summarizes the mine water level fractionation utilization pathway and classification of mine water dispatching mode, build the Na Lin mining area water supply dispatching model, analyzed the Na Lin River No. 2 mining area water supply dispatching model and the space-time change of water dispatching, through comparing with traditional dispatching model, the results showed that: The constructed water dispatching model can significantly improve the mine water recycling rate in Na Lin river mine area, which provides a certain theoretical basis for the study of efficient utilization of mine water.