| Nong'an County, as the key basic County of the State, not only produces agricultural products for local residents, but also supplies and processes the mainly agricultural production for its capital city, Changchun, and it also supplies millions of tons of marketable grains for our Country. In recent years, with the increasing of population and developing of economy, the heavy metal pollution problem in farmland soils in Nong'an County has been increasingly serious. Researching on heavy metal contamination in farmland soils will play a very important role in protecting more effectively and utilizing rationally the existing land resources, speeding up agricultural restructuring, developing pollution-free agricultural production to achieve standardization of agricultural production, and guaranteeing food and grocery security.Based on the environmental science principles, geography principles, and SPSS technology, geographic information system (GIS), taking farmland soils in Nong'an County as study area, the author evaluated roundly the heavy metal contamination in farmland soils, and disscussed deeply the spatial variation of heavy metals and impact mechanism. The following conclusions were drawn from the analysis.â… .The quality of the most soil environment was good in Nong'an County. In the 162 soil samples, the single pollution indexes, single-factor composite indexes and multi-factor integrated indexes of Pb, As, Cd, Cr all reached NY/P391-2000 standard. As for Hg, the single index is that 107 samples met NY/P391-2000 standard, 157 samples met GB/T18407-2001 standard and 5 samples failed; the multi-factor integrated index is that 103 samples met NY/P391-2000, in the safe and clean level, 157 samples met GB/T18407-2001, in the safe and clean level, and 5 samples failed, in the alert level but still clean; the single-factor composite index is that 7 townships met NY/P391-2000 standard, 15 townships only met GB/T18407-2001 standard.â…¡.The spatial variation trend of five heavy metals in farmland soils, Nong'an County, was that the index values of five heavy metals were mainly high in northwest and southeast. The high value of As concentrated in the central, northwest and southeast; Cd focued on the edge of north, northwest and southwest area; the distribution trend of Cr was interphase from the northeast to southwest; the distribution trend of Pb was interphase from west to east with low and high value; the distribution of Hg was similar to the multi-factor integrated pollution ratings map, which generally concentrated on the west, northwest and southeast.â…¢.The regional differentiation rules of heavy metal contamination in Nong'an County farmland soils related natural factors (the soil attribute, hydrological distribution) and human factors (rural townships, transportation, agricultural production, land use types), which were mainly affected by hydrological distribution and the livestock and poultry breeding in the agricultural production. The influence order of all influencing factors was: hydrological distribution>livestock and poultry industry>urban, transportation>plastic sheeting>soil attributes>land use types>fertilizer>pesticide. |
