| Huainan, an important city of coal industrial base, provided lots of energy for the development of China's national economy and society. As one of the most important coal producing bases, Huainan coal mine area has been explored for more than 50 years since P. R. C. was founded, which led to some inevitable impacts on the ecological environment of coal mine area. Especially, large amounts of arable land are changed into non-agricultural land use. Ground subsidence not only induce surface deformation, slope steep and serious erosion, which made a damage to land resources, but also lower the soil quality. Land reclamation is an important way to rebuild the ecological environment of coal mine area, so soil fertility quality restoration and security of groundwater of reclamation area are the key for the success of land reclamation. In this dissertation, aimed at the requirement of eco-environment construction of coal mine area of Huainan Coal Group, the reclamation soil and groundwater of Zhangji reclamation mine area were collected as research objects and the field investigation and the indoor tests were introduced to analyze the reclaimed soil. With the application of space and time correlation method, the physical and chemical properties of reclamation soil in Zhangji reclamation area were studied systematically. The reclamation soil fertility quality,the impacts of coal gangue on the accumulation characteristics and the potential ecological risk of heavy metal in the groundwater were also evaluated. The main conclusions are showed as follows:(1)The change characteristics of physical properties of reclamation soilIt shows a descending trend in soil bulk density of different layers with the reclamation time increasing. The layer of 0-20 cm reclaimed soil has a largest degree of decline in soil bulk density, secondly is layer of 20-40 cm reclaimed soil, which is 7.50%, and last is layer of 40-60 cm reclaimed soil. In addition, reclaimed soil bulk density of all layers is higher than control soil. The soil aggregate structure (0.25-2 mm) of layer 0-20 cm is increased by 27.73% after reclamation for 3 years; however, there are no significance change for layers of 20-40cm and 40-60cm. The law of reclaimed soil porosity is the same as the soil bulk density. There is a same place between different layers of reclaimed soil in content of water. That is higher content of water at reclamation time 0.5 a, 1.5 a and 2.5 a than those at 1.0 a, 2.0 a and 3.0 a, in other words, the content of water in reclaimed soil shows a"wave"change.(2) The change characteristics of chemical properties of reclamation soil There is a significance improvement of organic matter of reclaimed soil after reclamation for 3 years. Organic matter of layer 0-20 cm is increased by 148%, and 30.54%, 25.05% for layers of 20-40 cm and 40-60 cm, respectively. Furthermore, the content of organic matter in reclaimed soil is lower than that of in control soil. The pH value of reclaimed soil layer 0-20 cm also improvs after 3 year's reclamation, which is a little different while comparing to control soil. However, the pH values of reclaimed soil layer of 20-40 cm and 40-60 cm are much higher than control soil.The laws of TN, TP and TK of contents in reclaimed soil vary in different lays, there is an enhancement trend in TN, TP and TK contents after reclamation for 3 years for layer 0-20 cm, and the increasing rates are 28.29%,3.07% and 7.63%, respectively. However, the fluctuation scopes of TN, TP and TK contents in reclaimed soil of layer 20-40 cm and 40-60 cm are different. The main reason is that the total N,P and K mainly come from soil parent material, while there are a few impacts by the cultivation measures. The contents of available N, available P and available K in reclaimed soil show an increasing tread along with the reclamation time going up. The results indicate that all available nutrients have the same law, that is, increasing rate become lower with the depth increasing, in other words, the available nutrients in top layer soil improve more than those in subsoil. However, compared to the available nutrients in control soil, contents in reclaimed soil are much lower. As a result, it should be take some measures to improve the reclaimed soil in future.The laws of the trace elements of Cu, Zn, B and Mo in reclaimed soil are different. Overall, the contents of trace elements in layer 0-20 cm have an enhancement trend with the increasing of reclamation time, while there is a fluctuation change during the same period in layers of 20-40 cm and 40-60 cm.(3) Evaluation characteristics of fertility quality of reclaimed soilThe principal component analysis and fuzzy mathematics method were introduced to evaluate the law of fertility quality of reclaimed soil. The results show that: The fertility quality of reclaimed soil decreased with depth, which is the same as control soil. Furthermore, compared with the control soil, the fertility quality of reclaimed soil is lower, which is up to 92.68%, 90.63% and 88.33% of control soil from top layer to subsoil. The fertility quality of reclaimed soil has been up to about 90% of normal farmland's fertility quality level under the impact of cultivation measures and artificial fertilization for 3 years.(4) The evaluation of accumulation characteristics of heavy metal in groundwater of reclamation areaThe contents of heavy metal in groundwater of reclamation area increase to a different extent. Among the selected heavy metals, the Cd, Hg and Pb contents exceed the background values of water from individual well, while the content of As in groundwater of reclamation area is lower than background values of water from individual well. The Nemerow index values are 3.044 for Monitor wellâ… , 3.109 for Monitor wellâ…¡and 2.779 for Monitor wellâ…¢after reclamation for 3.0 years, respectively, which means that the acculumation of heavy metal in groundwater of reclamation areaâ…¡andâ…¢are strongly affected by coal gangue, while moderately affected by coal gangue for reclamation areaâ… .(5) The evaluation of potential ecological risk of heavy metal in groundwater of reclamation areaThe degree of potential ecological risk of heavy metal in groundwater of reclamation areaâ… andâ…¡is so high and it is up to"strong", while the degree of risk of reclamation areaâ…¢is lower, which is"moderate". The reason for the higher potential ecological risk of heavy metal in groundwater of reclamation area is that it is so enrichment for Cd and Hg in coal gangue, which are up to"very high"and"moderate", respectively. And the toxicity coeffifient of them are so big that resulted in a high degree of risk of potential ecological risk.Based on The Quality Standard of Groundwater (GBT14848-93), groundwater in reclamation area is not contaminated and could be of usage as agricultural irrigation and drinkable interests after reclamation for three years.
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