| As the source for all producing and exsiting, soil is the material basis of human’s living and development.With the quickening of the urbanization and the acceleration of the industrialization,the size of available soil resource has decreased while the population is increasing which made the contradiction between land supply and human need be more serious.This thesis carried out soil survey in Bazhou county, Nanjiang county,Pingchang county and Tongjiang county by the methods of geochemistry and we got 344 pieces surface soil samples,39 pieces profile soil samples, 49 pieces crop samples.This paper identifies the element contents in different soil types, different land utilization types, different soil tillage types and different counties of the region and finally select the crops that are high in Selenium, Iodine and Zinc.We evaluate the soil quality of this region by using the comparison and the contrast index method, the single factor evaluation method, the Nemero comprehensive evaluation method,the geological accumulation pollution index method, and ultimately divide the growing area.The main evaluation results are as follow.(1)The content of elements varies between different soil types, land utilization types, soil tillage types and different counties of the region.The Selenium and Iodine content of yellow brown soil is the greatest, the Selenium content of loess soil is less than that in paddy soil but more than that in purple soil.The Sulfur content of paddy soil is the greatest, the Sulfur content of yellow brown soi is less than that in purple soil but more than that in loess soil.The Zinc content of purple soil is the greatest, the Zinc content of yellow brown soil is less than that in paddy soil but more than that in loess soil.The Lead content of purple soil is the greatest, the Lead content of loess soil is less than that in yellow brown soil but more than that in paddy soil.The Cadmium content of yellow brown soil is the greatest,the Cadmium content of loess soil is less than that in purple soil but more than that in paddy soil.The Selenium content of the tea plantation land is the greatest, followed by other-garden land and vegetative land,the fourth is forest land,the fifth is farmland,and the content of orchard land is the smallest.The Iodine content of the tea plantation land is the greatest, followed by forest land and other-garden land, the fourth is orchard land, the fifth is vegetative land, and the content of farmland is the smallest.The Sulfur content of the vegetative land is the greatest, followed by forest land and other-garden land, the fourth is farmland, the fifth is tea plantation land,and the content of orchard land is the smallest.The Zinc content of the orchard land is the greatest, followed by vegetative land and forest land, the fourth is tea plantation land, the fifth is farmland, and the content of other-garden land is the smallest.The Lead content of the orchard land is the greatest, followed by othergarden land and tea plantation land, the fourth is vegetative land, the fifth is forest land, and the content of farmland is the smallest.The Cadmium content of the othergarden land is the greatest, followed by vegetative land and tea plantation land,the content of farmland equals the tea plantation land,the fifth is forest land,and the content of orchard land is the smallest.The Selenium and Iodine content of dry farming land is less than that in water irrigation land but more than that in dry-wet land.The Sulfur content of dry-wet land is less than that in water irrigation land but more than that in dry farming land.The Zinc content of water irrigation land is less than that in dry farming land but more than that in dry-wet land.The Lead and Cadmium content of dry farming land is less than that in dry-wet land but more than that in water irrigation land.The Selenium content in Nanjiang county is the greatest, the content in Bazhou county is less than that in Tongjiang county but more than that in Pingchang county.The Iodine, Sulfur and Zinc content in Nanjiang county is the greatest,the content in Tonggjiang county is less than that in Bazhou county but more than that in Pingchang.The Lead content in Nanjiang county is the greatest,the content in Bazhou county is less than that in Pingchang county but more than that in Tonjiang county.The Cadmium content in Bazhou,Tongjiang county is the greatest,the content in Pingchang equals that in Nanjiang county but less than that in Tongjiang county.(2)The corn and rice picked in Enyang town of Bazhou county,the tea picked in Xialiang town of Nanjiang county,the rice picked in Changchi town of Nanjiang county,the rice and the corn picked in Shuanglu town of Pingchang county are high in Selenium.The corn picked in Enyang town of Bazhou county is high in Iodine. The corn picked in Enyang town and the Shuanglu town is high in Zinc.(3)The relative abundance ratio value of Selenium, Iodine and Sulfur in the evaluation area is lower than that in the national soil horizon.Xialiang town,Ganchang town, Liuba town of Nanjiang county and Kongshan town of Tongjiang county are four selenium-rich area.The samples which content of Iodine are higher than the national horizon are in Xialiang town,Liuba town of Nanjiang county and Lianghekou town of Tongjiang county.The minimum value of Sulfur is 63.2μg/g,so the surface soil are full of Sulfur in Bazhong.There are 25 samples which content of Zinc are higher than the national horizon.They are distributed in Shuiningsi town,Chaba town, Yutang town of Bazhou county,Yuantan town,Dongyu town,Xialiang town,Changchi town,Zhaipo town,Shangliang town,Guanba town,Shitan town,Liuba town of Nanjiang county,Lancao town,Liumen town of Pingchang county,Nuojiang town and Sanhe town of Tongjiang.(4)The relative abundance ratio value of Lead and Cadmium and the national soil horizon are at the same level. Heavy metal Lead in the surface soil is all in accord with the first class, second class and the third class Standard of soil environment quality.Heavy metal Cadmium in the surface soil of the study areas is in accord with the second class but surpasses the first class.Heavy metal Cadmium in the profile soil of the study areas in accord with the First class.The Nemerow comprehensive pollution index of Lead is 1.24 which means the pollution level is the third level(light pollution). The Nemerow comprehensive pollution index of Cadmium is 2.99,which means the pollution level is the fourth level(middle pollution).The Geological accumulation pollution index of Lead is 0.625 which means it is light pollution,the index of Cadmium is 1.869 which means it is middle pollution. The artifical environmental concentration index shows the human activities influence to Cadmium is greater than that to the Lead.(5)The Selenium-rich,Iodine-rich,Sulfur-rich potato belt in Kongshan town of Tongjiang county,the Selenium-rich,Iodine-rich, Zinc-rich tea belt in Xialiang town of Nanjiang county,the Selenium-rich,Iodine-rich,Sulfur-rich,Zinc–rich vegetable belt in Liuba town of Nanjiang county and the Iodine-rich, Zinc-rich cereals belt in Changchi of Nanjiang county are four belts in Bazhong. |
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