| Soil is one of the main sources that human depends on for living and arable land which is based on soil is the basic of agricultural production. Arable land soil impacts the production and quality of agricultural products. As China is a country with 1.3 billion population, agriculture influences national safety. With the rapid development of industry, agriculture and urbanization,the heavy metal pollution of arable land is becoming more and more serious as a hidden danger for the quality of agricultural products and national health. To proven spatial distribution of heavy metals in arable land and mastering heavy metal pollution degree in arable land can lay a foundation of arable land pollution prevention and arable land quality protection, in turn to protect arable land resources and guarantee nation grain safety.Heilongjiang Province is a great agricultural province in China which has an increasing food production for years but also an arable land pollution. A lot use of pesticide, fertilizer and plastic sheeting in agricultural production brings a large number of heavy metal enrichment and then causes the pollution in in arable land soil. As the large-scale adjustment of agricultural grain product structure and comprehensive modern agricultural reform experiment in “Two Great Plains“ changing to national strategy, Heilongjiang Province started to build “Big Ecological Granary“ and “Large Green Kitchen“ project roundly.To positively respond the “Green Development“ suggestion from the Third Plenary Session of the 18 th Central Committee of the Communist Party of China and the “13th Five-Year“ national plan, Heilongjiang Province also developed green organic agriculture vigorously, kept developing safely and efficiently green and provided the basis for the food security, ecological environment security and national health security. Nehe County attaches to Qiqihar City in Heilongjiang Province with favorable natural conditions which have advantages of developing green agriculture.Through the analysis of spatial distribution characteristics and environmental quality evaluation of heavy metals in arable land of Nehe County, we can acquire the situation of environmental quality in arable land of Nehe County which has a guiding significance to ensure the safety of arable land quality, prevent soil pollution and develop green agriculture.It also has a reference value and function to the protection work of arable land quality safe of other areas in Heilongjiang Province.Based on the sample point data of 8 kinds of heavy metal elements(Cd, Cr, Pb, Cu, Zn, Ni, Hgand As) in arable land and land-use data of Nehe County, this research using the method of spatial interpolation and spatial analysis, analyzed the statistical and spatial distribution characteristic of 8kinds of heavy metal and evaluated the single heavy metal and integrated arable land environmental quality of Nehe County using methods of single factor index and Nemerow index,finally obtained the arable land polluted situation of Nehe County. The main conclusions are as follows:(1) Spatial simulation of heavy metal in arable land of Nehe County.This research used semi-variance function analysis of GS+ to get the optimal Kriging interpolation models of 8 kinds of heavy metals: Cd-Gaussian,Cr-Gaussian,Pb-Exponential,Cu-Exponential,Zn- Spherical,Pb-Gaussian, Hg-Gaussian and As-Circular. Comparing the numerical value of Nugget coefficient and range, it showed that Hg and As were affected by random factors, Pb and Ni were affected by structural factors and random factors, while other heavy metals were affected by structural factors. Pb had a better uniformity, while Cd, C, Cu and As had a stronger variation in small area.(2) Analysis of spatial distribution characteristics of heavy metal in arable land of Nehe County. There were content overproof of Cd and Cu in research area by analyzing sample points statistically. Through analyzing the results of Kriging interpolate and spatial overlay by using Arc GIS, the overall spatial distribution trend of 8 kinds of heavy metal in arable land of Nehe County was as following: the distribution of Cd had a gradually diminishing effect from north to southeast and overproof content area is located in the northern region; the distribution of Cr had a gradually diminishing effect from southeast(eastern part) to other directions; the distribution of Pb is uniform and smooth with medium content; the distribution of Cu was irregular, there were a number of overproof content area mainly distributed in central and southern region; compared with the other seven elements, distribution rule of Zn was the most irregular one, high content area appears as multiple scattered point distribution, mainly in the southern and eastern region;distribution of Ni was gradually diminishing from north to south, with medium content;distribution of Hg had a gentle decline trend from southeast to north; distribution of As was decreasing from northeast and south to northwest. Through the correlation analysis, it showed that there were a certain extent correlation among all heavy metals but not strong. It was a likely existence of homology of Cu-Zn and Cr-Zn. There might be no combined pollution of Cd and Cu in study area.(3) Environmental quality evaluation of heavy metals in arable land of Nehe County. Single factor pollution degrees of heavy metal in Nehe County were relatively less as no pollution. The pollution level of Cd and Cu was higher and Hg was lower. There was light pollution of Cd in Laolai Town, Nehe Poison and Xuetian Town and Cu in Changfa Town, Tongyi Town and Nehe Town and no pollution in the other towns. The distribution of heavy metal polluted land plots was sporadic in Nehe Poison, Xuetian Town, Laolai Town, Nehe Town, Liuhe Town and Erkeqian Town but mass in Hesheng Village, Xingwangewenke Village and Tongnan Town. The multiplepollution level of arable land in Nehe County was low grade. The pollution levels of arable land in Nehe County were Still-Clean(waning line) and Mild Contamination. No towns or villages reached the level of Clean(safe), Xingwange-wenke Village and Tongnan Town were Still-Clean(waning line), while the other towns were Mild Contamination. |
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