Study On Spatial Characteristics Of Soil Heavy Metals And Its Ecological Risk Riparian Zone In Shandong Province

Under the background of globe climate change, loss of biological diversity and thesustainable development problems, the impact of increasing human activities on riparianzone is concerned by researchers at home and abroad. Especially, the loss of wetlands, thedecline of biodiversity in riparian zone and pollution of agricultural non-point sourcehighlights the importance of riparian zone. In recent years, with the rapid economic andsocial development and the strict control of point source in Shandong Province, non-pointsource pollution has become the most serious threat to the safety of water environment inShandong Province. As a large agricultural province, non-point source pollution fromagriculture accounts for about two thirds in Shandong Province. Rivers, lakes, reservoirsand other surface water source within Shandong Province are increasingly affected by thedeterioration of water quality and pollution of riparian zone.By using methods of data collection, field sampling and laboratory analysis, the waterenvironmental quality in part of rivers and reservoirs in Shandong Province was studied,and the heavy metal pollution as well as its ecological risk in riparian soil was assessed.The results showed that:(1) Heavy metal concentrations in riparian soil of Shandong Province generallypresented normal and skewed normal distribution. The average concentrations of Cr, Co,Ni, Cu, Zn and Pb in riparian soil were lower than the corresponding soil backgroundvalues of Shandong Province, and the average Hg concentration was slightly higher thanthe background value; and only Cd concentration was significantly higher than the soilbackground value, which was about1.4times of the latter. Heavy metal concentrations inpart of the sampling sites were higher than heavy metal limit values of the class Ienvironment quality for soil in China (GB15618-1995), but were all lower than values ofthe class II environmental quality standard for soils. Compared with the other researchresults about the farmland soil in Shandong Province, Cr, Co, Ni, Cu and Hgconcentrations in riparian soil were significantly lower than those in the farmland soil,while Zn and Pb concentrations were in the middle level. Generally, heavy metal concentrations in riparian soil of Shandong Province were in the same order of magnitudeas those reported in other riparian soil.(2) Heavy metal concentrations in riparian soil of Shandong Province were bothsignificantly correlated with total organic carbon (TOC) and mean particle size, whichindicated that TOC and particle size might have great impact on the heavy metalconcentrations in riparian soil; however, pH values of riparian soil had little influence onthe heavy metal concentrations in riparian soil.(3) The assessment results by using the geo-accumulation index method and potentialecological risk index method showed that heavy metal concentrations in riparian soil weregenerally at clean and light pollution level. The potential ecological risk of heavy metalswas generally light and moderate, but Cd and Hg generally presented strong and evenrelatively high potential ecological risk in some riparian soil. Therefore, Cd and Hg werethe main pollution and ecological risk factors. From the spatial distribution characteristicsof heavy metal pollution, a higher degree of heavy metal pollution and a higher ecologicalrisk were found in riparian soil from Zhu Zhaoxin River, Liaohe River, Men Lou Reservoirand Dongping Lake than riparian soil from other water source areas.(4) Pearson correlation analysis and principal component analysis were used toidentify the sources of heavy metals in the riparian soil. The results showed that heavymetal concentrations in riparian soil were significantly correlated with each other, whichsuggested the combined pollution of heavy metals and their similar source. In general, theheavy metal concentrations in riparian soils were determined by both the soil parentmaterials and external sources related to human activities including contaminated surfacerunoff, industry waste gas, domestic solid waste and vehicle emissions etc. According tothe identified source of the heavy metals, countermeasures were put forward to control theheavy metal pollution in riparian soil.