| Weathered coal and steel slag are typical industrial solid wastes in our country. Many scholars have done a lot of researches and obtained some practical results on resource utilization of weathered coal and steel slag. But people do little research on the potential environmental risk of weathered coal and steel slag.Our aim was to study environmental effects of poisonous and harmful material in weathered coal and steel slag. The study focuses on their own harmful material, analysis the distribution and occurrence of the harmful trace elements and PAHs in Weathered coal, discuss the distribution and occurrence mechanism of the harmful trace elements in steel slag and steel slag's effect to soil physical and chemical properties. Find the transport and transformation of harmful substance in weathered coal and stainless steel tail slag on soil system.The major results were summarized as follows:1. After adding weathered coal, compare with the control treatment, the concentration of mercury, cadmium and lead in soils significantly increased, but the concentration of arsenic, chromium in soils significantly decreased; with the increased weathered coal doses, the concentration of mercury increased significantly, but the concentration of arsenic decreased significantly.2. After adding two kinds of weathered coal, the amount of PAHs in soil gradually increased with the increased weathered coal doses, but here has some differences on the increasing trend:the total content of PAHs in soils increased significantly after adding Shanxi weathered coal when the weathered coal doses were 80% and above; the total content of PAHs in soils increased significantly after adding Inner Mongolia weathered coal when the weathered coal doses were 60% and above. Here has some differences on the effects of two kinds of weathered coal to the component of PAHs:with the increased weathered coal doses, the content of phenanthrene, fluoranthene, benzo(a)anthracene, chrysene, benzo(b) fluoranthene, benzo(k)fluoranthene in soils increased significantly; but the content of acenaphthylene, anthracene in soil did not increase significantly. In the treatments, phenanthrene in soil has the largest amount, acenaphthylene in soil has the smallest amount.3. After adding stainless steel slag, the concentration of chromium, hexavalent chromium, cadmium, lead and nickel in soils significantly increased; but the concentration of zinc in soils significantly decreased. The concentration of hexavalent chromium and lead of soils in acid rain mode were significantly higher than no-acid rain mode; the concentration of cadmium and nickel of soils in the no-acid rain mode are significantly higher than the acid rain mode; the concentration of chrome and zinc of soils did not significantly change in two kinds of leaching mode. Study shows that:stainless steel slag can significantly improve the concentration of chromium, cadmium, nickel, lead in soils, and acid rain can increase environmental risks of hexavalent chromium and lead in soils.4. Adding stainless steel tail slag can significantly improve the pH value of soil and leaching solution, organic matter and soil aggregates; but soil CEC did not increase significantly. The pH value of leaching solution in acid rain mode were significantly lower than the no-acid rain mode, so did the soil organic matter.5. The technical regulations of national soil pollution evaluation evaluates the effects of weathered coal processing on heavy metals in soil and the result shows:after the two weathered coal processing, chromium, cadmium, lead, arsenic and mercury content in soil are not more than standard values. The soil environmental quality standards (revised draft) industrial land standard evaluates the influence of weathered coal PAHs on soil and the results showed:the treatment soil PAHs are not more than standard content. But the Netherlands soil quality standards which reference to 10 kinds of PAHs goals of found 7 kinds of PAHs named naphthalene, phenanthrene, fluoranthene, benzo(a)anthracene, chrysene and benzo(k)fluoranthene and benzo(g,h,i)perylene above the target. According to 16 PAHs classification method of pollution degree in agricultural soil suggested by Maliszewska-Kordybach(1996),after Shanxi weathered coal processing,∑PAHs concentration in soil are pollution levels of light when weathered coal content reaches 60% or more; after Inner Mongolia weathered coal processing,∑PAHs concentration in soil are pollution levels of light when weathered coal content reaches 10%～90%,∑PAHs concentration in soil are pollution levels when weathered coal content reaches 100%.6. The technical regulations of national soil pollution evaluation, evaluates the stainless steel tail slag processing effects of heavy metals in soil and the results show:chromium, cadmium, lead, zinc, nickel content in soil are not more than standard values after stainless steel tail slag processing. The groundwater quality standards (GB/T14848-93), evaluates stainless steel tail slag processing effects of heavy metals in soil leaching liquor and the results show:hexavalent chromium, cadmium, lead, zinc, nickel content in leaching liquor were not reached groundwater water quality standard (Ⅲ).In summary,1. The heavy metals in weathered coal have some effect on soil and the surrounding groundwater around the area, but not yet on the environment to cause safety risks. Weathered coal processing can significantly increase the content of PAHs in the soil. According to the foreign relative standards, when the two weathered coal usage reached a certain amount (Shanxi weathered coal usage 80%, Inner Mongolia weathered coal usage 60%), the content of∑PAHs in soil will overrun the environmental safety risk standard, and it will cause safety risk. So, in the processing of weathered coal in soil, it's needed that the PAHs in soil should carry on a long-term monitoring.2. The heavy metals in stainless steel tail slag can bring some effects on soil and the surrounding groundwater, but not yet cause safety risks to the environment.Stainless steel tail slag can significantly improve the physical and chemical properties of soil. It is suggested that the stainless steel tail slag can be used in the restoration works of mining degenerate soil. |
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