| Lead and zinc smelting is an important industry in our national economy.China is also the world's largest country of lead zinc production and consumption.However,in the modernization of our country,smelting lead and zinc ore dressing process produces a large amount of tailings particles and the environmental pollution of the surrounding soil,water and plants is getting worse and worse by the slag after smelting.Research of the release of smelting slag dumping and presence of toxicity to surrounding environment using bio-toxicity methods are believed to reflect the quantitative impact of heavy metal stack on environment and creatures.This article focus on a lead-zinc smelting mining area changing the pH of the extraction agent to investigate the slag surrounded.For further comprehensive evaluation of the regional pollution,a pH model of acid rain precipitation was constructed and the toxicity was assayed using biological diagnosis.The results showed as followings:(1)Analysis of the pollution characteristics of slag and soil reflected that the heavy mental content of the surrounding soil exceeded the national regulations of soil standard class three and the local background value several times.It suggests that the accumulation of heavy metal,which is far beyond the minimum level,probably due to mining,selection,and smelting.Hence,the level of heavy metal content is a potential threat to the ecological environment.(2)Comparison of the leaching results:though these two kinds of leaching manner showed a similar leaching outcome,the horizontal vibration method was used because the roll over leaching procedure would consume much more samples and test materials.(3)The leaching of the heavy metals by the reversed oscillation and the horizontal vibration under different pH conditions,the leaching of slag and soil was very obvious when the leaching of slag and soil was and pH was 2 and 4,while in the range of 4.0?9.0,the leaching effect showed a stable tendency and the leaching amount is not high.The stability of Ni,Mn,Cd,Co,Pb and Zn raised with the increasing of pH,The most leaching capacity in the slag is Zn,The overall soil leaching results is not good,when pH>2,the leaching of heavy metals was not obvious.In addition,we choose the conditions of the leaching agent of pH4 leaching agent near the local acid rain precipitation,in accordance with the integrated standard for Wastewater,the leaching of slag Zn in M-1 produced a certain leaching toxicity and stockpiling of the new factory village slag has reached the degree of hazardous wastes,while leaching toxicity of other heavy metal elements is relatively small,and only in the local acid rain pH lower than will be leaching.(4)Two different dynamic extraction methods both showed a high amount of Zn leaching and leaching rate,the rest is relatively low.In a continuous time level oscillation process,the leaching amount of all these elements showed an increased trend dependent on the time.The result informed that in a certain period of time,the leaching amount of heavy metals in the slag and the leaching rate is increasing with time.In a continuous time dynamic sequential extraction process,the leaching amount would drop until reached a plateau with the gradual increase of the leaching amount,which suggested that with the increase of time and extraction times,the exchange capacity of heavy metal elements is becoming less.After then,by supplement of a certain of H+,the amount of iron and manganese in exchangeable form or organic form is fixed.This is a appropriate explanation why the result tends to be stable in later period time.However,with the increase of leaching times and leaching times,the total amount of heavy metal accumulation leaching gradually increased,and the increase of the speed of the slag accumulation decreased gradually.So under the condition of long-term acid rain erosion,surface water handling and other adverse conditions in the region,with increasing time and number of contacts,the leaching of the heavy metals,especially the leaching of Zn,will cause more and more pollution to the surrounding ecological environment.(5)In the Vibrio fischeri test,M-1 slag showed the max inhibitory effect on Vibrio fischeri.Through diluting M-1 slag leaching liquid,luminescent bacteria photoinhibition degree and the toxicity gradually increased with the increase of water volume fraction.According to the toxicity criteria,we can found that M-1 slag leaching solution is seriously poisonous;Hei Ni Zhai slag leaching liquid is non-toxic;the new factory village soil and Hei Ni Zhai soil leaching liquid has no toxic effect.It suggested that M-1 slag leaching solution has already produced a certain toxicity to the surrounding organisms,and the leaching solution of M-2,S-1 and S-2 has not yet been toxic.In earthworm test,On the third day,heavy metal element enrichment amount greater than the background value is mainly reflected in Zn,Cd,Pb,however,others showed no significant difference between them.The accumulation of Zn content in the whole research reached the maximum,which indicated that earthworms are selective in heavy metal enrichment to a certain extent.With various culture time and increased concentration of heavy metals,the accumulation in soil was obviously changed.If the content of heavy metal that the earthworms up-taked exceeded its tolerable allowance,earthworms can be dead because of the toxicity from excessive heavy metals.At the same time,the growth and normal activities will be inhibited.As a whole,among all these heavy metal elements in soil,the higher content of elements,the more amount of earthworms enriched.If the content of heavy metal that the earthworms uptaked exceeded its tolerable allowance,excessive heavy metals can directly poison earthworms,and have a fatal influence on their life activity as well as inhibit growth.In this experiment,earthworms in both the soils have certain enrichment of heavy metals.However,the concentration of Zn,Pb and Cd in the soil has not yet reached the resulting in earthworm lethal concentration.Therefore,mine smelting of the surrounding soil in the regional produced certain heavy metal accumulation,but had not yet reached the extent of death.(6)In this paper,the contents of heavy metals in the region were determined by the content of heavy metals in the slag and soil.Results showed that it caused a certain potential pollution to the surrounding environment,The leaching of slag and soil indicates that the area M-1 slag has reached the level of hazardous waste by different pH,oscillation mode,extraction time and extraction times.M-1 slag heap are close to the local acid rain pH conditions,which will produce certain Zn pollution.Besides,the environmental pollution of the slag storage will be more heavier with increasing contact time of local acid rain and rainfall times.The leaching solution of M-1 slag has certain toxicity to the organism by the biological toxicity test of slag and soil.The contents of the elements in the earthworms have a certain accumulation of heavy metals and have not reached the degree of death.As the whole research area,the heavy metal pollution of the slags and soil were not so serious,except the slag leachate M-1 produced toxicity of Zn.The soil produced an enrichment of heavy metal but not deadly.Thus it is necessary to strengthen the prevention and supervision of the slag and soil,meanwhile the slag and soil around the smelting mine should be cleared and harmless treatment urgently. |
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