| With the development of social economy in our country, soil heavy metals, pesticide residues, fertilizer pollution and sewage irrigation, which affect the quality of agricultural products, show a spreading trend. Especially after our entering WTO, several developed countries carried out"green barrier"to the agricultural products export of our country, causing huge economical loss to the state, enterprises and farmers, which is not conducive to agricultural efficiency, farmers'income increase, and rural economic development. At present, the environmental background of most land quality in our country is still unknown, so there lacks basic foundations for regional land use planning and industry planning. Therefore, it is urgent to realize scientific agriculture planning, adjust agricultural economic structure, develop agricultural economy, and find out the environmental quality of agro-geology.Based on theory of environment geochemistry, soil geochemistry, agro-geology geochemistry and ecology geochemistry, this thesis carried out geochemical field survey in the study area combining with the its practical complexion. According to the geological background, terrain, and soil types, field samples were collected for test. Then the data from sample test were used, by mathematical statistics and GIS technology, to synthetically study the distribution of heavy metals in different types of soil and other media in Dakang Town, Jiangyou City. The soil heavy metals were evaluated by means of actual heavy metals content evaluation, potential ecological risk index assessment and fuzzy mathematics comprehensive appraisement, and the results of which, together with soil fertility assessment and ecological effect, were used to gradate land quality on geochemistry. On the foundation of gradation, this thesis adjusted land use structure and industry structure, in order to provide scientific support for new rural construction and land's social-economical benefit increase.Through systematic study, this thesis got main results as follows: (1) Analyzing the data of 296 surface soil samples in the study area by mathematical statistics, the background content values of heavy metals in soil of Dakang Town, Jiangyou City are 10.67μg/g for As, 0.31μg/g for Cd, 84.34μg/g for Cr, 30.17μg/g for Cu, 0.08μg/g for Hg, 35.04μg/g for Ni, 33.68μg/g for Pb, 90.36μg/g for Zn.(2) Study on elements distribution feature in soil, water, air dust near ground and creatures. By analyzing,the elements content in soil is mainly affected by mother rock; heavy metals content in air dust near ground are generally over standard, the main source of which are probably the third sub-plant of Great Wall Steal Factory nearby and Steal Alloy Manufactory interior.(3) The soil quality in view of heavy metals was evaluated by means of actual heavy metals content evaluation, potential ecological danger index assessment and fuzzy math comprehensive appraisement. The results indicated: the soil quality in the study area was good in general, but some regions had the potential pollution of Cd.(4) Evaluation on soil fertility indicates that the study area can be divided into region with low fertility soil and region with common fertility soil. Acreage of the former is 610.88hm2, accounting for 32.14% of the whole area, scattering at the valley of the three villages; acreage of the latter is 1290.10 hm2, taking up for 67.86%, centralizing at Xinghuo Village and Hongguang Village.(5) Combining factors like soil, water, air and ecological effect to gradate land quality, the result is that lands in the area is mainly belong to 311-grade and 411-grade, accounting for 28.49% and 24.79% respectively, mainly distribute in the foothill, using for woodland and dry land. Next, the 511-grade and 521-grade lands, accounting for 11.49% and 12.03% respectively, locating in the valley, using for irrigating paddy field.(6) Evaluation on ecological effect of agricultural products by biological enrichment coefficient and health risk evaluation model indicated: the enrichment coefficients of wheat on Cd, Cu, Hg, Pb were higher than those of rate; the enrichment coefficients on As were similar; the enrichment coefficients of the other elements of wheat were lower than those of rate. Evaluation on health risk of wheat in the study area showed: heavy metals As and Cd had light degree to harm health through diet, but the potential danger of Cd could not be disparaging; for rate, even the whole Cd of seed went into edible oil, risk from As and Cd was below the recommendatory standard, whose potential danger degree could almost be neglected.(7) Based on land quality evaluation on geochemistry and ecological effect assessment, this thesis carried out agricultural production distribution in the study area, into a region characterized by cultivating economical crop, two regions characterized by agricultural plantation, and a region for tourism,Layout for the local government to provide agricultural information.
|
PDF Full Text Request