某轻武器射击场土壤重金属总量及赋存形态分析

Analysis of the total concentration and the existing speciation of heavy metals in small arms shooting range soils

以中国华北地区某轻武器射击场为研究对象,采用USEPA3050B(HNO3-H2O2)法监测并分析了土壤表层样品中重金属Pb、Cu、Zn、Cr和Ni的总量。结果表明,射击场土壤已出现了明显的Pb、Cu累积,其总量分别为土壤背景值的210.77倍和2.93倍,分析认为重金属污染源为土壤中的残留弹头、弹片、弹壳等。同时采用Tessier连续浸提法分析了土壤中Pb、Cu的赋存形态。结果表明,射击场土壤中Pb形态分布依次为残留态、碳酸盐结合态、铁锰氧化物结合态、有机结合态、可交换态;Cu形态分布依次为残留态、铁锰氧化物结合态、有机结合态、碳酸盐结合态、可交换态。综合分析土壤中Pb和Cu的总量、形态分布及生态毒性,Pb的污染风险相对较高,是该轻武器射击场后期土壤重金属污染治理工作中应优先关注的元素。

In this paper, we have made an investigation and analysis of the total concentrations of Pb, Cu, Zn, Cr and Ni in the surface soil samples from a small arms shooting range in North China by using USEPA3050B （HNO3 -H202） method. The results of our investiga- tion and analysis show that the soil of the small arms shooting range is heavily polluted by the heavy metals Pb and Cu. The total mass ratios of Pb and Cu were found to reach 210.77 and 2.93 times as much as that of the environmental background value of this region, respective- ly. In accordance with GB 15618--1995, 90% of the total area of the range has been polluted by the element of Pb in different degrees, and 45 % of the total area of the range has been polluted by the ele- ment of Cu. We have detected that, the heavy metal pollutants may include the residual bullets, shrapnel, and cartridge cases, which tend to bring ever-lasting pollution of heavy metals to the soil if no measures would be taken to them. We have also done analysis of the concurrent speciation of Pb and Cu in the soil with the sequential ex- traction method of Tessier, discovering that the speciation distribution order stands as follows： Resid - Pb 〉 Carb - Pb 〉 FeMnO - Pb 〉 Org - Pb 〉 Exch - Pb. As to the distribution characteristics of Cu, the or- der can also be listed as follows： Resid - Cu 〉 FeMnO - Cu 〉 Org - Cu 〉 Carb - Cu 〉 Exeh - Cu. Moreoves, the Carb - Pb content is comparatively high in various degrees of chemical speciation. A more serious consequence would be that, once the environmental conditions change, the Carb- Pb can also be easily transformed into a bioavail- ability speciation. At the same time, both the total concentration and ecological toxicity of Pb tend to be much higher than that of Cu. Thus, it can be seen that the environmental contamination risk of heavy metal Pb can be much more serious to the environment. It can thus be concluded that Pb residential speciation should be paid prima- ry attention to the prevention of soil being polluted in the future.