西部某机械加工企业酸洗场地环境调查与污染特征分析

Contamination investigation and characteristics analysis of the pickling site in a mechanical processing factory in the Western Plateau Area,China

以西北高原地区某铁塔厂酸洗车间为重点区,对场地开展系统的环境调查,结果表明：该场地以重金属锌污染为主要污染因子,场地内土壤Zn浓度范围13.68～68 800 mg·kg-1,局部区域土壤p H异常、土壤Fe含量和Cl-浓度升高现象;土壤Zn污染垂向迁移深,多数点位Zn污染（Zn含量超过200～500 mg·kg-1）深度达10 m以上,少数点位污染深度达15 m以下,其中北区酸池5 m以内、南区酸池3 m以内和下水管道及两侧区域3～10 m深度范围内为重污染;场地土壤p H异常范围与锌污染范围一致,土壤Cl-浓度和Fe浓度与Zn浓度具有相关性,可作为判断土壤锌污染程度和范围的辅助因子;现场速测的Zn含量与实验室总量测定结果一致性强,在p H异常区域的现场速测p H值与实验室测定结果的一致性较好,现场速测结果可作为污染表征的基础依据。推测酸池泄漏、含重金属洗液长期下渗和工业废水的直接排放为场地污染主要原因。

This study investigated a contaminated site located at an iron tower factory in the Northwest Plat- eau Area of China, and in particular, sampling was conducted in the vicinity of the pickling workshop. The follow- ing results were obtained. Zn was determined to be the most important pollutant at the site,and concentrations of Zn varied between 13.68 and 68 800 mg ~ kg-1. In some areas,the soil pH levels were abnormally low and the concentrations of C1- and Fe were relatively high. Vertical transportation of Zn in the soil was evident at the depths with abnormal Zn concentrations （ i. e. , greater than 200 to 500 mg · kg-1 ） ; most sampling points extend- ed to 10 m below the surface,but a few points reached as far as 15 m below the surface. Soils above 5 m in the north area acid pools,soils above 3 m in the south area acid pools,and soils between 3 and 10 m depth in the pipeline area were all heavily polluted. The areas with abnormal pH values were consistent with the Zn contami- nated areas, and the concentrations of C1- and Fe were strongly correlated to the concentration of Zn. Thus,these other endpoints may be useful for assessing additional Zn contamination at the site. The X-ray fluorescence （XRF） results for Zn in the field were consistent with the laboratory-based analysis results, and furthermore, the rapid measurements of pH in the abnormal areas showed a good match to the laboratory-based analysis results, which means that rapid measurements may be valid to use for assessing the contamination at the site. It is specu- lated that the main cause of Zn contamination was long-term leaching from solutions and wastewater containing heavy metals, as these materials were discharged directly at the site in the past.