Geochemical Study Of Land Suitability Of Liao River Basin

Land Suitability Evaluation is a model of determining the most appropriated spatial pattern of landuse according to human requirements, wishes or forecast of future activities. It is the basis of the overall landuse planning. Liao River Basin is located in central Liaoning Province, and is a major commodity grain base in Liaoning Province with fertile soil and ample water. For the rapidly developed industry and agriculture, the characteristic of soil element geochemistry of this region has changed in great degree for accepting the wastewater and solid waste produced by the industry, agriculture and human everyday life. The soil quality of the land is reduced greatly and this would be an important factor which restricting the development of the region.This paper explored the distribution rule of elements geochemistry of surface and deep soil, the land condition of the whole Liao River Basin and the factors which impacting the spatial and temporal distribution of the soil element geochemistry on the platform of GIS by the means of factor analysis, geostatistics and fuzzy mathematics, and achieved the following results:1)16main factors of surface and deep soil were got by factor analysis of54elements in the soil of the Liao River Basin. The elements loaded by factor1were most and they represented the results of the natural weathering. The main elements of the soil has the "U-shaped distribution" feature. The distribution characteristic of heavy metal elements loaded by factor2and3were disturbed by human activities obviously. Distribution of element Nitrogen was closely related to other organic matter. Other elements have high content in the coastal saline, aeolian and sandy soil, and the increased potassium content was caused by soil desertification2) The results of geostatistical analysis showed that, there are different degrees of distribution variation of the elements in the surface layer soil of Liao River Basin:there are strong spatial autocorrelations in the distributions of nutritional elements of Ca, Mg, P and essential elements of Fe, Mn, Zn, Cu, B, Si and heavy metal element of Cr and Ni, and the distribution of other nutritional elements, essential elements and heavy metal elements were the combined effect results of random and structural factors. Among them, the spatial variation of heavy metal of As, Cd, Pb and Hg were similar, which were mainly affected by the random factors.3) The Liao River basin was divided into five regions according to the quality of surface soil by the method of SOM neural net and the C-value classification. Region A has fertile soil with sufficient N and P content and balanced content of various trace elements. Region B is the hilly and equalizer geochemical district with a moderate element contents except the elements of Cd, Cl and I. Region C is an extremely barren land with low levels of nutritional elements required by the crop, low content of trace elements and high content of Si and K. Region D is the coastal high halogen element geochemistry District. Region E is the high pollution of heavy metals district with high content of heavy metal elements which was affected by the human activities.4) The results of the overall environmental quality assessment of the Liao River basin showed that, the Liao River basin land was in good condition; the clean and non-polluting soil area was about87.9%which could be used for agricultural production. The soil contaminated areas of Liao River basin were concentrated in two cities of Shenyang and Jinzhou with Cd element as the main pollution factors, followed by Hg, Pb, and Zn.5) The results of comprehensive evaluation on the soil nutritional status showed that, the soil nutrient situation was alarming. The area of "very rich soil" and "rich soil" were only accounted for2.3%; the moderate soil accounted for11.62%; the relative barren soil accounted for45.57%; the barren soil accounted for31.94%; the very barren soil accounted for8.55%. There are less than15%area of the soil is meeting the basic needs of the farming.6) Through factor analysis of element geochemistry of the Liaohe basin backbone river bottom sediments and shallow sediments, the results showed that:The content of heavy metal elements Cr, Cu, Hg and nutrient elements N, P in trunk river bottom sediments were in overall higher levels, and which mainly distributed in the Hun River in Shenyang city, Taizi River in Anshan city and other surrounding water systems. The content of Cd, Hg, Pb and Zn in the marine sediments has the characteristics of high in west and coastal, low in east and deep-sea, and the concentration center was in the belt of Jinzhou bay in Jinzhou city, Lianshan bay in Huludao city. As the same, the average content of Pb, Cu, Mo, As, Sb, S and Ag were higher than the background value of shallow sea sediments of China and showed the enrichment feature. In addition, the results of analysis of element geochemistry feature of the typical mines and urban industrial areas showed that, mining and urban industrialization also changed the elements of the local soil, resulting in the enrichment of heavy metals and pollution, then affected watershed ecological environment.7) Through the factor analysis and the CIA method on the platform of GIS, the results of studies on the elements geochemical characteristics and the weathering degree of surface and deep soil showed that:the weathering degree of the Liao River soil was low, and there was some differences in the spatial distributions, but the degree of surface and deep soil weathering was not much difference. Affected by the weathering degree and human factors, the nutrient element content in the surface soil of the Liao River basin was relatively increased. The distribution features of heavy metal were affected by human factors, with a relatively high content in topsoil of urban areas, industrial area and mining area.