| 其他摘要 | Antimony is a typical toxic heavy metal. However, the studies on supergene geochemistry and pollution control for antimony are still insufficient, with respect to the fact that China is the major antimony producer in the world. Guizhou Province, in which large antimony deposits are distributed, is located in the Southwest China’s epithermal mineralized zone with high geochemical background baseline of Sb, and it is also located in the Southwest China’s karst zone, in which the karst landform develop intensively, thus, its entironment is fragile. As a result of extensive mining for antimony in Guizhou, the soil and water were suffered from serious Sb pollution. Therefore, it is significant to study the supergene geochemistry of Sb so as to understand its environmental effect and to seek for remediation approaches.
This dissertation, taking the Banpo Antimony Mine in Guizhou as a case study, has aimed at the distribution, transfer, and enrichment of Sb in rocks, solid mine wastes, soils, waters, and plants in the antimony mine area, and at understanding the supergene geochemical processes of Sb，and evaluating acid rock drainage generation potential, and screening out new hyperaccumulators. The following findings were obtained:
1. The Banpo Antimony Mine area is a typical high Sb geochemical background region owing to Sb mineralization. Sb contents are high not only in ore minerals, but also in wall-rocks, which are far higher than the average content of Sb in upper crust. Stibnite is the main carrier and potential release source of antimony to the environment.
2. In solid wastes, the content of Sb is the highest in smelting residues, followed by waste rocks and tailings. The elements characteristic of waste rocks is similar with that of the wall-rocks, which suggests that the waste rocks have inherited the elements characteristic of wall-rocks. However, the elements characteristic of tailings is different from that of the wall-rocks, owing to the alteration during crashing and floating. The concentration mode of Sb is in the sequence middle layer> bottom layer> surface layer in tailings, which is similar to those of Fe and Al. The distribution mode is mainly controlled by redox condition, the effect of rainwater dripping and filtration, and adsorption mechanism of minerals containing Fe/Al. The distribution of Sb in the tailings showed the following order: residue fraction > carbonate fraction > organic/sulfide fraction > exchangeable fraction > Fe/Mn oxides fraction. The distribution of easily bioavailable Sb is the same with that of total Sb.
3. All mining waste rocks have potential to generate acid such that effective measures are expected to prevent acid rock drainage. The tailings have no potential to produce acid drainage, owing to soda lime mixed during smelting process and low S contents. However, the alkaline condition is helpful for activation and mobility of Sb in supergene environment.
4. The soils have been polluted seriously, the contents of Sb in soils are up to 51~7369 mg/kg in study area， and decrease gradually with depth in study area, and the Sb contents in bottom soils is similar with that in soils of control area. High geochemical background concentrations in outcropped rocks and in soils indicate that both the natural erosion or leaching of outcropped host rocks and soils associated with Sb mineralized area and the human activities contribute to the high antimony accumulations in surface soils. The distribution of Sb in the soils showed the following order: residue fraction > Fe/Mn oxides fraction> carbonate fraction> organic/sulfides fraction > exchangeable fraction. The transfer of Sb is correlated with As in soils.
5. The water type is SO4/HCO3-Ca in study area. Sb exists in the aquatic system as the dissolved fraction, the suspended fraction, and the sediment. The transfer process is controlled by absorption-desorption mechanism and stream process. There are different diffusion mechanisms between high water period and low water period. The aquatic pollution during high water period is more serious than that during low water period. The contents of Sb in sediments vary in the following sequence: residue fraction > carbonate fraction, Fe/Mn oxides fraction> exchageable fraction, organic/sulfides fraction. The behavior of Sb is strongly influenced by the mining and smelting activities. The sulphur isotopic tracing study found that 59% S in downstream water of Chahe River were contributed by mine, and illustrated that the water quality of downstream had been seriously affected by mining activities.
6. The uptake of Sb in soils is species-dependant and tissues-dependant. Generally, Sb contents in underground tissues of plants are higher than those of ground tissues, and decrease with the following order: root>leaf>stem. Antimony contents in crops decrease in the following sequence: Chinese cabbage > green cabbage > chilli and rice. The species of Chenopodium ambrosioides Linn. is identified as an Sb hyperaccumulator. The species of Bidens pilosa Linn., Erigeron annuus (Linn.) Pers., Sedum lineare Thun, Sedum emarginatum Migo, Chenopodium album Linn., and Gnaphalium affine D. Don are identified to accumulate Sb, and present strong tolerance to Sb, and they may be used as alternative plants for remediation on Sb-polluted soils.
7. This special high Sb contents in the local specific geoenvironment iampcted with human activities lead to Sb transfer and accumulation in the supergene environment, especially in crops and water, which would impact the local population health. |
修改评论