| With the rapid economic growth, increasing exploitation and utilization of coal resources in China, the environment has been polluted seriously. Coal gangue is the primary source of pollution in mining. In general, the coal gangue was piled up to form the gangue dump around the mining area. Coal gangue dump not only coverages a large area of land, but also contaminates the underlying soil, water, and also atmosphere. Therefore, numerous researches have been conducted on solving problems of ecological environment derived from coal gangue. Furthermore, increasing awareness of issues such as food security, phytoremediation of heavy metals in soil has been attracted more attention and widely used. Due to the advantage of low cost, quick, phytoremediation has became a primary method used to remediate the heavy metal pollution in coal gangue dump. Different measures of vegetation restoration have different effects on remediating soil heavy metal pollution. As a result, scientific evaluating application of different phytoremediation methods to soil heavy metal coal gangue dump remediation can provide a theoretical basis and practical guidance for soil ecological restoration in coal gangue dump.In this paper, soils from five modes including 10 years’human afforestation Robinia pseudoacacia L, Rhus typhina Nutt, Ulmus pumila L., Hippophae rhamnoides Linn, and natural restoration land(CK)in coal gangue of Fushun, China have been studied. To analyze the content of heavy metals in soil and plant, and evaluate the contamination of soil and plants useing the Nemerow pollution index method, and the potential ecological risk index to understand remediation of different planting patterns on waste dump soil heavy metal pollution in Fushun. The main results are listed as follows:1. The heavy metal contents of soils from different afforestation modes are different, and some shows the significant difference.The pollution indices showed that Cd is belong to heavy pollution levels in the soil of gangue dump; Cu and Pb are belong to the clean leve; Cr and Ni are belong to the clean level in Robinia pseudoacacia L mode, Cr and Ni are belong to the slightly polluted level. The Nemerow Pollution Index showed that compared with CK mode the soil heavy metal pollution levels of 4 kinds of afforestation mode all had been reduced. The decreased degree order was Robinia pseudoacacia L mode(37.7%)>Rhus typhina Nutt mode (7.9%)> Hippophae rhamnoidesLinn mode(4.1%)>Ulmus pumila mode(1.6%). Robinia pseudoacacia L mode was the best mode for soil heavy metal pollution remediation in coal gangue of Fushun, comprehensive pollution index of it was 2.28, the soil heavy metal under it was belong to the moderate pollution level.Potential ecological risk assessment indicated that Cd has a very strong potential ecological risk in the soil of gangue dump. Cr, Cu, Ni, and Pb are slightly potential ecological risk. The potential ecological risk indice showed that compared with CK mode4 kinds of afforestation mode could reduce the potential ecological risk of soil heavy metals in coal gangue.The decreased degree order was Robinia pseudoacacia L mode (37.3%)>Rhus typhina Nutt mode(7.4%)> Hippophae rhamnoides Linn mode (3.8%)> Ulmus pumila mode (1.4%).The Robinia pseudoacacia mode is belong to the highly potential ecological risk, Remaining 4 modes were estimated as very high potential ecological risk. These results from the two different evaluations were demonstrated to be same.2. Under 4 afforestation modes, compared to the CK, residual was found to be the primary form in 5 heavy metals morphological distribution. Fe-Mn oxide combination and organic combination state were the second, and the exchangeable state and carbonate combination state were the last.. The residuum proportions of heavy metals in 4 afforestation modes are greater than CK. The exchangeable, carbonate combination and Fe-Mn oxide combination proportion are lower than CK, This suggests that these different planting patterns have the capacity of immobiling soil heavy metals.3. The contents of Cd, Cr, Cu, Pb, and Ni of different plants were different. The heavy metal contents of different organs in a same plant are also different. The coefficients of heavy metal enrichment of 4 plants shown that they can’t be matched as hyperaccumulation plants. The enrichment capability is greater in roots than the parts above soil. Robinia pseudoacacia has a stronger enrichment capability for Cd, Cr, and Pb. Rhus typhina Nutt has a stronger enrichment capability for Cu and Ni. Ulmus pumila has a stronger enrichment capability for Pb and Ni. Hippophae rhamnoides Linn has a stronger enrichment capability for Cu, Pb, and Ni. Robinia pseudoacacia has a stronger transfermation ability for 5 heavy metals. Rhus typhina Nutt has a stronger transfermation ability for Pb. Ulmus pumila has a stronger transformation ability for Cu and Pb. In the studied area, all vegetations can not reach the edible standard. The heavy metal pollution index of plants showed that the polluted order of plants was Robinia pseudoacacia L mode> Ulmus pumila mode>Rhus typhina Nutt mode= Hippophae rhamnoides Linn modeIt followed that the order of the remediation ability of afforestation mode for soil heavy metal pollution was Robinia pseudoacacia L mode> Rhus typhina Nutt mode> Ulmus pumila mode> Hippophae rhamnoides Linn mode.The Robinia pseudoacacia mode can be a good method for the soil heavy metal pollution remediation. The rest of the 3 kinds of mode also had a certain remediation ability. According to the purpose of economy and ecology,we can choosed different afforestation mode. |
PDF Full Text Request