长江三峡库区部分元素土壤环境背景值研究

长江三峡库区土壤环境背景值研究,是长江三峡大型水利枢纽工程兴建土壤环境影响研究的一个部分。它不仅为库区土壤环境质量评价提供标准,并直接参与水库水质和底泥的质量组成,为预测库区土壤及水体环境质量演变趋势、制定库区环境保护对策和管理措施提供依据。库区环境特点是,开发历史悠久,绝大部分地区是已受到不同程度开发的农、林用地,未开发区少见。但大型现代工矿企业不多,点源污染较少。因此三峡库区土壤环境背景值,不同于单纯反映原始处女地及自然保护区特征的土壤本底值,或反

Background Values of Some Trace Elements of Soils in the Reservpir Area of the Yangtse Gorges

This paper reports on background values of some elements in soils of the reservoir area around the Yangtse Gorges. The sampling design was made like this: the said area was divided into eleven environmental units in accordance with environmental differences and in each unit, a certain amount-of sampling points were arranged according io intensity of impacts of natural and social environments upon soil system, resulting in 118 sampling points all told.Data processing was done like this: hypothesis testing of difference of mean values of two normal populations, or rather t-testing with pairing comparison was used to "analyse the data from surface layer and sub-surface layer of soil, and the result showed the difference between these two layers was insignificant, so the background values of soil were calculated with the surface layer data, and abnormal values were rejected by using the method of plus of minus three times of standard error with arithmetic mean value. In addition, the classification of concentration distribution was tested by Pilson X² method, Shapro-Wilk W method, Kolmogrov method, Skewness and Kurtosis method. In soil of the whole area, Pb, Zn and As were subjected to normal distribution, Cu logarithmic normal, and Ni skew normal, Variables subjected to normal distribution were represented by arithmetic mean plus or minus standard error. Variable subjected to logrithmic normal distribution was represented by geometric mean multipling or dividing standard error. Variables subjected to skew normal distribution were processed by normalization. The result of conputation gave the background values of soils in the reservoir area: Pb was 20.15±6.47ppm, Cu 13,76±2.06ppm, Ni 22.64±7.57ppm, Zn 78.27±20.42ppm, and As 9.09±4.45 ppm. Then, the variance analysis and Duncan method of multi-comparison were used to testing the differences of background values of soil environment between different soil groups and that between different parent materials respectively. Besides, analysis for the causes of the differences was processed. The conclusion is that difference between different soil groups was caused by different conditions of water, heat, biology and parent materials, and the function of irrigation-plowing cultivating as well, while the differences between different parent materials had relations with the palaeogeographic environment in which the parent materials of soils were transformed into rocks.