Research Of The Ecological Geochemistry Characteristics Of Heavy Metals In The Soil Of Qingdao Urban Area

As we all know, contaminants, especially heavy metals, are difficult to be decomposed and transformed, once they are entered into soil. That is because heavy metals have a very long life. Once be accumulated to a certain degree, they will do harm to living beings and enter into human body according to the food chain, and finally bring about harm to human’s body and life safety. Supported by the ecological geochemistry survey of Qingdao urban area, this paper completes the following work. First, this paper investigates the basic values and the space distribution characteristics of heavy metals (i.e., elements As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the soil of Qingdao urban area. Basing on this work, this paper finds the causes of these abnormal values and investigates their effects on the characteristics of biological enrichment. Combined with the distribution characteristics of heavy metals in dust and the relationships between heavy metals in dust and these in soil, this paper also predicts the influence that heavy metals in dust exert on the contents of them in soil.(1) Based on the research about the geochemical characteristics of heavy metals in soil, this paper finds that:The distribution of heavy metals in the soil of Qingdao urban area is related to the formation of lithology and landforms. The contents of As, Cr, Cu, Hg, Ni and Pb are high in the low mountainous distribution area of cretaceous, while the contents of As, Cd, Cr, Cu, Ni, Pb and Zn are high in the denudation and accumulation prospective plain area. In surface soils, elements As, Cr and Ni are in line with normal distribution. Besides, they are relatively even in space distribution. In contrast, elements Cd, Cu, Hg, Pb and Zn deviate from the normal distribution slightly. Moreover, the space of these elements distributed asymmetrically with punctiform, insular or sheet abnormality area. Therefore, it can be concluded that elements Cd, Cu, Hg, Pb and Zn are obviously influenced by human activities, while As, Cr and Ni are weakly influenced. The vertical profiles show that the migration distances of heavy metals in surface exogenous soil different to each other. However, these kinds of heavy metals mainly distributed in the soil of 0.6m below the surface, especially with some deepest cases 0.8m.(2) Based on the research about the influence that heavy metals exert on biological concentration, this paper finds that:The heavy metals enrichment capacity of various vegetables different greatly. The root vegetables have strongest enrichment capability. Followings are leaf vegetables. The fruit vegetables have weakest enrichment ability. There are co-absorbing phenomena among heavy metals in vegetables. Especially, the co-absorbing phenomena are popular in root vegetables. The heavy metals in soil have stimulative or prohibitive effect on the enrichment of other heavy metals in vegetable.Different halobios have different ability in enriching heavy metals distributed in sediment. Fish have low ability in enriching heavy metals, and so have low contents. In contrast, shellfish and algae have strong ability, and so have high contents. Similar to the vegetables, there are co-absorption phenomena among halobios. Algae have the strongest co-absorption ability. The heavy metals in sediment can also stimulate or prohibit halobios absorbing other heavy metals. Especially, they have strongest inhibition function to shellfish.(3) Based on the research of characteristics of heavy metals in dust and prediction about influence of heavy metals in soil, this paper finds that:According to the dust experiment, the migration ability of heavy metals in soil is affected by many factors. And these abilities are different with factors. However, all the migration coefficients of these elements are not exceeding 3.The heavy metals in the dust of Qingdao urban area have great spatial variability and pervasively higher than the contents in corresponding soil samples. The contents of heavy metals in dust and soil different greatly. Among them, element Hg is the highest one, whose value reaches 2097. The High values area of heavy metals in dust often distributed in island shape and near to the coastline.According to the time accumulation model about the influence the heavy metals in dust exert on these in soil, this paper predicate the influence that heavy metals in dust exert on the ones in soil 20 years later. It is found that elements As, Cr, Cu, Ni, Hg and Pb have little influence. That is because there are only some pointlike or island shape high value areas. However, elements Cd and Zn have obvious influence. Therefore, to prevent soil from Cd, Zn pollution, the detection and control about element Cd and Zn in dust should be strengthen.