高潜水位平原采煤沉陷区耕地损毁程度评价

中国煤炭与耕地分布复合区面广量大,煤炭开发不可避免地造成耕地减产或绝产。该文针对高潜水位平原型采煤沉陷区,在明确评价单元的目的性和尺度差异性基础上,基于农用地分等理论并兼顾采煤沉陷特点,构建了包括耕地土壤特征、耕地环境变化和耕地配套设施3个准则层、15个指标的评价指标体系;基于最差因子判别法与综合指数法,提出了耕地损毁指数模型。通过案例进行应用与验证,结果表明:沉陷盆地上坡、中坡、下坡及坡底的损毁指数分别为0.081、0.190、0.248和1,耕地损毁程度分别为轻微、轻度、中度和极严重损毁,在全面反映耕地损毁状况的同时,评价结果也能与农用地等级更新有效衔接。

Evaluation on farmland damage by underground coal-mining in plain area with high ground-water level

Abstract: The overlapping areas between arable land and coal resource distribution are over 40% of total farmland in China, which results in the large amount of farmland to be destroyed by coal mining. Evaluating the damage gradation of farmland in coal-mine area is very important not only for land reclamation planning, but also for determination on compensation payable for the farmland damage from coal-company to the farmer. Besides, it can forecast the quantity and quality of farmland grade changes in mining area and can warn this change earlier. Focusing on the eastern plain mining-area with high ground-water level, the authors aimed to find an effective way to evaluate the farmland damage in underground coal-mine area. Taking the 10 mm sinking depth contour as the subsided area boundary, the authors put forward the method to dividing one subsided basin area into 4 evaluation units: upslope, mid-slope, downslope and bottom. Then based on the different analysis of evaluation purpose, area scale, the existing gradation system of agricultural land quality and the character specificity of mining-subsided land, the farmland damage evaluating indicator system is created, which includes 3 kinds of factors: soil physical and chemical property such as effective thickness of soil layer, soil bulk density, total nitrogen, available phosphorus, available potassium, soil organic matter and soil pH value; soil environmental factors such as subsidence depth, additional gradient, fracture density, buried depth of groundwater; cultivated land facilities factors, such as drainage condition, irrigation water and, irrigation reliability and protective forest facilities. By using relative value method to assign points of evaluation index, the index of the pros and cons is calculated the relative score value between 1 and 100. The weight of each evaluation index is obtained by using AHP method (analytic hierarchy process), which is 0.43, 0.44 and 0.13 respectively for soil physical and chemical property, soil environmental factors and cultivated land facilities factors. Thirdly, using the worst factor discriminant method and comprehensive index method integrally, the authors put forward the cultivated land damage index model. In that model, Im the cultivated land damage index, is equal to the ratio of cultivated land quality scores of evaluation unit to that of control field unit. It normally values between 0 and 1, where the bigger the value is, the more serious the damage is. In order to be used easily, the author divides the value of Im into five sets, namely (0, 0.1), [0.1, 0.2), [0.2, 0.4), [0.4, 1) and 1, which is respectively corresponding to the damage degree sets, namely slight, mild, moderate, severe and very severe.Finally, one mining subsided area in north part of Anhui province in China, is taken as a case study area, where the evaluation index system and farmland damage index model are used. The results show that the farmland damage indexes of the upper slope, middle slope, lower slope and the subsided basin bottom are 0.081, 0.190, 0.248 and 1 respectively, which means the damage gradations is slight, mild, moderate and very severe in proper order. The result can be applied to both land reclamation management and the updated work of gradation on agricultural land quality.