| Grain security is matter to national economy and people’s livelihood. With the rapid development of urbanization in China, many problems such as rural labor transfer, agricultural land converted into non-agricultural land, pollution of agricultural production has appeared. If these problems cannot be effectively solved, grain security will continue to face great pressure. At the same time, the increased grain rigid demand caused by population growth and people’s high requirements for grain security in modern society also make grain security attract extensive attention. Based on Zhangjiagang City as the research area, Landuse map of Zhangjiagang City is drawn by interpreting TM remote sensing image, then the landscape pattern is analysed with the support of GIS analysis software; Land use/cover change of Zhangjiagang City is simulated and forecasted by using CA-Markov Model; Agricultural land sample points are chosen in2010and2011to study the characteristics of heavy metals accumulation and transformation, then comprehensive evaluation is made on the soil and rice pollution in study area; According to the grain security, green and health development, considering the ecological, social and economic benefits, selecting and analysing the indices to build a scientific grain security, green and health comprehensive evaluation system and discussing the function of application in Zhangjiagang City. Research progress made by3years research is as follows:1) With the development of urbanization, urban construction land will continue to increase, while agricultural land will be reduce. Agricultural land change to non-agricultural land in the process of urbanization is an inevitable trend. Compare the landscape indices between agricultural land and construction land, the value of PLAND in agricultural land is23.17%, the value of PLAND in construction land is28.28%, the former is lower than the latter; the value of PD is only6.04%in agricultural land, which means agricultural land is easy to be interference. Overall, as opposed to construction land, agricultural land is in a relatively weak position in the distribution of landscape pattern in Zhangjiagang City.2) It is predicting that from2010to2020, the urbanization process of Zhangjiagang City will continue to expand from urban to rural, agricultural land will decreasing73.2hectares on average per year, While construction land will increase143hectares on average per year. The trend of the decreasing of agricultural land and the increasing of construction land will not change in Zhangjiagang in the short term. The absolute value of simulated landuse change dynamic degree show a decreasing trend year by year, which indicating that the urban expansion speed may slow down gradually in Zhangjiagang City.3) Different rice organ has different enrichment capability to heavy metals, the research in study area shows:roof> leaf> grain; The value of soil comprehensive pollution indices in the two years research are both lower than0.7, agricultural land soil has not been polluted by heavy metals. The average value of single factor indices in Cr, Cu and Zn of rice grain are0.131,0.450and0.321, the average value of the comprehensive index is0.407, rice grain has not been polluted in general, But in the sample point of Heping village, the value of single factor indices in Cr, Cu and Zn are obviously higher than in the other sample points, and Cr is slightly over the standard.4) The grain security, green and health comprehensive evaluation system covers the whole process of grain production and sales, and could be used to reflect ecological, economic and social benefits. By considering constructing principle of index system and functional requirements, the evaluation for grain security, green and health could be more comprehensive. Using grain security, green and health comprehensive evaluation system to evaluate grain security and the development of green grain industry, can systematically reflect the present situation of grain security in Zhangjiagang City, and help to find existing problems then take targeted measures.There are two innovation points in the research:One is to research agricultural land and grain security from two aspects:quantity and quality. Through the research of agricultural landscape pattern change and model simulation and prediction for the future development trend to reflect the effect on grain quantity security; Through the research of heavy metals accumulation and transfer situation in agricultural land soil-rice system, and analysis and evaluation heavy metals pollution situation to reflect the relationship between agricultural land quality and grain quality security. The other innovation point is that:a variety of methods are used to analysis heavy metals accumulation and transfer situation in soil-rice system. Spatial interpolation method is adopted to simulate the spatial distribution of heavy metals; Analysis on the rice roots, leaves and grain enrichment capacity of heavy metals from soil; Using Nemerow comprehensive pollution index for pollution evaluation.Overall, the research helps to understand the urbanization process, the present situation and change trend of agricultural land and the effect on grain security in study area. The work on the exploration and build of the grain security, green and health comprehensive evaluation system could provide reference for grain security evaluation in the new period. |
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