The Research Of Land Ecological Risk Assessment Based On Special Information Technology

In the footsteps of the industrialization and urbanization, agricultural societies have been transformed into urbanized landscapes; land quality has decreased by the advancing soil degradation processes caused by industrial chemicals and agrochemicals; and land ecosystem has been threatened by loss of biodiversity and habitats. Land ecological risk assessment has been gain more and more concern by researchers, managers and publics. To achieve a sustainable development, impacts on land ecosystem of land use changes, chemicals and other stresses must be considered in land ecological risk assessment on regional scales. Many studies on soil risk assessment have been conducted about chemicals such as heavy metals and pesticides but there is as yet not a well-defined universal methodology to characterize land risk and to define a set of clear indicators includes physical, chemical and biological factors.This paper defines land ecological risk stress as physical factors which are land use change and loss of habitats, chemical factors which are heavy metals and soil degradation, and biological factors which are loss of biodiversity etc. This paper, selected Taiyuan city, Shanxi Province as a case study area, focus on a joint analysis of the two definitions of soil quality and land use/cover change, analyzes the distribution characters and spatio-temporal of these factors, leading to comprehensive assessment of land ecological risk that have relevance for sustainable land management.The main contents and results are as follows:Ecological risk assessment is a process that evaluates the likelihood that adverse ecological effects are occurring as a result of exposure to one or more stressors. Based on identification of stressors and reorganization of adverse effects of potential ecological concern in heavy industry city, this chapter developed conceptual model for integrating multi-stressors exposure to land ecosystem in an urbanizing environment on regional level. . Land-used/Cover Change in Taiyuan City is analyzed based on remote sensing images in 1990, 2004. GIS technology, land used dynamic degree model and landscape theory are used to research the spatio-temporal trend and land ecological risk of LUCC. From the study, the following conclusions are drawn: 1)the area of Cultivated land, woodland and grassland were decreased with the time, while, the area of constructed land was increased. 2) The land-use types of this area had changed frequently in the past 14 years, especially those interlaced areas with fragile ecological environment between cultivated land, woodland and grass land. 3)the landscape diversity and fragmentation had increased while the landscape dominance had reduced. The land ecosystem structure risk had increased.Soil samples were collected from the research area and analyzed to determine heavy metals concentrations and nutrients concentration. The spatial distribution of Hg and Cr in soils in this area was explored using the technologies of Geographic Information System and Geostatistic. Results of spatial distribution analyses showed that 1) the spatial self-correlation of heavy metals in soils in this area were low dependent, while nutrients were moderately interdependent. 2) the spatial interpolation map revealed different elements had a different spatial distribution, which are affected by both structural (including topography factor, soil type, soil native matter and soil texture factors) and random (including fertilizer, crop, management and human actions) factors; 3) Various spatial distributions suggested that urban planning and soil pollution control should focus on soil spatial character and local condition.Single Factor index, comprehensive index and Hakanson potential ecological index were used to assess the ecological hazards of heavy metals in urban soils of research field. The results showed that Hg and Cd had a higher risk level and the other heavy metals had a lower risk. Hankanson potential risk assessment showed that most of soil samples in this area had moderately risk, while few samples had extremely risk level. Risk of heavy metals in the north part and central part of research area were higher than that of other parts. Industrial pollution, agricultural pollution and traffic pollution lead to the high risk of these soils.An comprehensive assessment model of land quality was established based on Support Vector Machine (SVM), The model is experimented with indicators which include soil heavy metals data, soil nutrients data, soil pH, sampling locations and land cover type data of research area, The results demonstrate that Support Vector Machine can resolve problems of classification with small sample more effectively and accurately. SVM method can reach an ideal comprehensive evaluation results accurately and objectively for land quality assessment.To integrate the land physical risk and chemical risk, multi-variable array model was developed to put landuse/cover structure risk and soil hankanson risk into together.