GIS-Based Variability Of Soil Cadmium And Lead In Changdu Plain

According to the survey data of Chengdu Plain, the one-year's variational characteristic of soil heavy metal cadmium and lead together with their influential factors were studied by coupling Geographic information system (GIS) with geostatistics. Meanwhile, the spatial variability of cadmium and lead and the impact of soil organic matter, pH and particle composition on the content of heavy metal were also discussed. By means of field and soil column simulating experiment, the determinacy non-mechanism model of soil heavy metal cadmium and lead was funded. The one-year's leftover content of regional soil heavy metal cadmium and lead was available via the simulation of the model, and in the paper the relativity between leftover content of soil heavy metal cadmium and lead and their influential factors such as fertilizer amount, air dust and irrigation amount were also discussed. The main results were as follows:The content of cadmium in 0²0cm's soil layer in Chengdu Plain was between 0.01 mg kg^-10.33 mg kg^-1 and its average content was 0.21 mg kg^-1 .While its spatial distribution was gobbet, with the high value region (>0.25 mg kg^-1) mainly existed in and around the downtown of Chengdu, which was gradually decreased to the edge of Chengdu Plain. The low value region(<0.13 mg kg^-1) existed in Qionglai district; Meanwhile the content of lead in 0²0cm's soil layer changed from 5.00 mg kg^-1 to 67.37 mg kg^-1 and its average content was 36.96 mg kg^-1. Also its spatial distributing was gobbet. The high value region(>45 mg kg^-1) mainly existed in downtown of Chengdu, and from which gradually decreased towards the edge of Chengdu Plain. The low value region (<30mg kg^-1) existed in Qionglai and Xinjing districts.The results of correlation analysis showed that there were no significant differences between the content of SOM, soil pH, soil particle composition and the content of Cd and Pb, respectively. Furthermore, the comparatively higher regions of the content of Cd and Pb also were more advanced in industry and traffic, which indicated that the industry and traffic had a relatively great influence on the content of soil Cd and Pb, representing in the soil profile of 20⁴0cm.The soil columniation simulation experimentation showed that soil cadmium content was mostly increased in all seasons in addition of fertilization and irrigation, but decreased in thesoil horizon 40⁶0cm. Soil lead content was increased in all seasons and all soil horizons.Soil cadmium and lead content was decreased from surface layer to bottom layer except very few horizons in inspection period. Soil cadmium content from Ocm to 40cm soil horizon was decreased in wheat season, and was increased in paddy season; from 40cm to bottom had no distinct change trend. Soil lead content in soil horizon had same change trend, was declined in wheat season, was increased in paddy season.This paper simulated the remnant content of soil cadmium and lead by non-mechanism ascertain model. The results showed that the average remnant content of soil cadmium and lead were 2.54g (hm2-a)"' and 72.36g (hm2-a)*', separately. The distribution trend of soil cadmium appeared as strip, and the remnant content of soil cadmium had one order decreased trend from east to west. The highest value (>3.2g (hm2-a)']) region was existed in the east of Chengdu, the north of Longquanyi. In addition, the region which had highest probability of remnant content of soil cadmium was 0.2g (hm2-a)"' was existed in the east of Chengdu. The distribution trend of soil lead appeared as strip, and the remnant content was decreased from east to west. The highest value (>81g (hm^a)"1) region was existed in the strip of Longquanyi and Qingbaijiang. The region which had highest probability of remnant content of soil lead was 60g (iW-a)"1 was existed in the east of Chengdu and Qingbaijiang, etc.Many factors had highly significant positive correlation with soil remnant content in transport parameter. According to the influence extent, there were heavy metal in dustfalK corps, flooding, fertilization, etc. But to soil lead remnant content, there were heavy metal in dustfalK leakage, fertilization> corps, etc. It showed that the remnant content of soil cadmium and lead influenced biggest by atmosphere dustfall.