| 其他摘要 | Heavy metals are the metals which density is above or equal to 5.0. With the rapid development of urbanization and the increase of urban population on the world, we need to know more about the city ecological environment and research the relationship between urban ecological environment and the health of human being.
Atmospheric deposition includes dry and wet deposition. Atmospheric dry and wet deposition is a crucial content of atmospheric chemisty, environmental chemistry and biological geochemistry, and they play a significant role in the circulation of heavy metals. Atmospheric deposition has a vital influence on the geochemistry of heavy metals in the soil. In order to control the heavy metals pollution effectively and provide scientific data, it is very important to know the source, behavior and fate of heavy metals in the environment. Urban soil is an important component of the city ecological environment and it has momentous significance to the urban sustainable development. In the urban environment, large numbers of heavy metals are schlepped to the urban soil through all kinds of human activities. So these heavy metals are accumulated in the soil and they are directly or indirectly threatening the health and even life of human being by the atmosphere, water body or food chain.
We took Guiyang City as an example, and studied the heavy metals in the environment. We researched the concentration and speciation of heavy metals in the total suspended particles (TSP) of Guiyang systematically, analyzed the concentration and seasonal variation in the rain water and researched the concentration and speciation of heavy metals in the soil. The main conclusions of this study have been presented as follows:
1. Atmospheric dry and wet deposition in Guiyang City has close relation with weather factors. With the increase of temperature, the concentration of TSP descends. The relative humidity has negative relation with TSP. The influence of wind speed on TSP is diffusion and dilution, with the increase of wind speed, the concentration of TSP decreases. Rain water has obvious function of elimination to TSP. With the increase of wind speed, the concentration of heavy metals decreases. The precipitation has negative relation with Cd, Cr, Cu, Pb and Zn. The general trend is that when the precipitation is higher, the concentration of heavy metals in rain water is lower.
2. There is obvious seasonal variation rule of heavy metals in TSP of Guiyang City. The concentration of Cd, Cr, Pb and Zn is obvious higher in winter than other seasons and it is lower spring and summer. The concentration of heavy metals in winter is 1.8-4.6 times of that in summer season. The same, the highest concentration of Cr, Cu and Zn is in winter which is in accordance with the abundant coal combustion in winter.
3. The pollution of heavy metals in TSP of Guiyang is serious in comparison with other cities. The concentration of Cd、Cu、Pb and Zn in most rain water samples is beyond the the national standard value. The average content of Cd、Cu、Pb and Zn in rain water is 2.7、2.2、6.0 and 1.3 times, respectively. The surfacial soil of Guiyang City has been polluted by heavy metals to different extent. The average concentration of Cd, Co, Cr, Cu, Ni, Pb and Zn is 0.66mg/kg, 17.31mg/kg, 82.91mg/kg, 52.20mg/kg, 38.76mg/kg, 71.03 mg/kg and 216.05mg/kg, respectively. The concentration of Cd, Co, Cr, Cu, Ni, Pb and Zn is 6.80, 1.36, 1.36, 2.31, 1.44, 2.73 and 2.98 times in comparison with the background value of the element in our country. And the accumulation of Cd and Zn are especially obvious.
4. We analyzed the speciation of heavy metals in TSP and soil in Guiyang City. And the results showed that: Cd is mainly in the form of easily soluble in the TSP and the ratio is 61.4%. Cr and Cu are restricted to the fraction bound to silicate and organic matter in TSP and they have little impact on the environment. The fraction bound to carbonate and oxide of Pb is the most. Zn has the most proportion of environmentally mobile fractions in the three stages. The ratio of easily soluble fraction to total concentration of Co、Cr、Cu、Ni、Pb and Zn is lower except for Cd, and each easily soluble ration of Co、Cr、Cu、Ni、Pb and Zn is less than 3.0% in the soil. While the ratio of easily soluble fraction of Cd to total concentration is 23.3%. On the contrary, the ration of the residual fraction to total concentration of Zn，Cr，Cu，Co，Ni and Pb and Zn is higher except Cd, and the residual fraction ratio of Zn，Cr，Cu，Co，Ni and Pb is 96.8%, 92.2%, 83.4%, 69.2%，57.4%, 41.9%, respectively.
5. The concentration of heavy metals in the profile of Guiyang urban soil is disordered and has no rule. The concentration of in the bottom is even high. Guiyang urban soil is influenced by human factors (construction, repairing road, industrial waste, garbage, transportation exhaust) and so on. Urban soil is greatly changed. There are different material sources in urban soil, the profile is constantly disturbed by human and the natural soil is damaged. All the reasons mentioned above have led to that there is no relationship between the upper and bottom soil. |
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