Study On Temporal-Spatial Distribution Evolution Of Soil Nutrient And Heavy Metals Of Sewage Irrigation Region In Baiyangdian Upstream

In recent years, the shortage of water resources influenced agricultural production, and city sewage contained nutrient elements which was plants needed, therefore, with sewage water irrigation as the important means to save water in conditional area. At the same time because of pollutants input, especially the heavy metal elements, the soil environment problem of irrigation region were prominent increasingly, and through the food chain endangering human health. Therefore, study temporal-spatial variability of soil nutrient and heavy metal elements in irrigation region, assure law of the scientific and reasonable utilization of soil resources in irrigation region, which was theoretical significance and guiding value about maintaining the agriculture productivity of ecological system, ensuring food safety, and realizing agricultural sustainable development. This paper selecting sewage water irrigation region of suburb of BaoDing City in baiyangdian upstream, by adopting a Geostatistic maethod with the GIS software as an aid, basing on variogram theory model, using ordinary kriging interpolation method, studying soil organic matter, total nitrogen and alkal-hydrol nitrogen, total phosphorus and availability phosphorus, pH and heavy metal elements temporal- spatial variation in surface soil layer (0~20cm) in 1994, 2000 and 2008. Puts forward reasonable utilization of soil resources measures in irrigation region. The research results were as follows: the soil was irrigated by contaminated water of Fuhe long-term, average content of total nitrogen, alkal-hydrol nitrogen and phosphorus respectively were 1.18±0.30 g/kg, 86.33±15.09 mg/kg, 47.59±22.29 mg/kg, which were higher than the average content of total nitrogen, alkal-hydrol nitrogen and phosphorus of soil by water irrigation. In 2000 compared with 1994, there had different degree increase of soil organic matter, total nitrogen, alkal-hydrol nitrogen, total phosphorus and availability phosphorus, increase area account for the research area were 89.52%, 89.47%, 64.72% and 98.38% respectively, total phosphorus content was the largest increase area; And total phosphorus content in 63% of research area was decreased. In 2008 compared with 2000, soil organic matter, total nitrogen, alkal-hydrol nitrogen, total phosphorus and availability phosphorus were increased, increase area account for the research area were73.4%, 85.2%, 72.3%, 76.5% and 64.1% respectively. Heavy metal contents in soil were increased more clearly than background values of BaoDing City. Heavy metals were not exceed standard and single contaminate index were less than 1, not contaminated in sampling sites. Sample point at Yucheng village of Wangting Township and Pingling village of ShiQiao Township were reached alarming. The other samples were reached cleaning standard, soil and crop were not contaminated. Cr content in surface layer (0 ~ 20cm) of Baiyangdian upstream were evenly log-normally distribution, whereas Cd, Hg, Pb, Cu and Zn were normal distribution. The decreasing order of variation in different heavy metals in 2008 was: Hg>Cu>Cd>Pb>Zn>Cr, with the coefficient values of 0.81, 0.36, 0.26, 0.25, 0.13, 0.11 respectively, which showed Hg had larger difference in different regions. Zn belonged to the weak variation degree, others belonged to medium variations. All heavy metals were varied spatially with regional features, and their trend effects were obvious. Cd content was distributed in south-north by irregular ribbon, the highest value regions (>0.55 mg/kg) were distributed in northern of research area, which accounting for 8.5% of the research area. Hg content showed high in northwest and low in southwest and southeast of spatial distribution, the low level in total area. The trend of Pb content was decreased from northwest to southeast, the highest value regions (>45.0 mg/kg) were distributed in northeast area accounting for 17.8% of the research area. The trend of Cr content was increasing from southeastern to northwest areas, most areas was in 80.0~85.0 mg/kg range. Cu content were irregular mass distribution about the highest value in northwest and northeast, and the lowest in southeast. Zn content was increasing from south to north. In 2000, compared with 1994, Cd, Hg and Pb content of soil were increased with different degree in total area, increasing area account for the research area were 98.2%, 79.41% and 89.9% respectively. In 2008 compared with 2000, Cd, Hg and Pb content of soil were increased in total area, smaller increase degree.