矿区污染场地土壤重金属元素分析标准样品的研制

摘要

In China, the mining district and surrounding areas have been high risk areas for soil pollution by heavy metals.These are also the main areas for environmental monitoring of soil.Unfortunately, soil certified reference materials (CRMs) in which matrix and levels of heavy metals consistent with the actual soil in thse aeras are not available.In this study, based on the pollution characteristics of the heavily polluted soil area and high-risk area, and requirements of practical environmental monitoring, agricultural soil surrounding the mining district of red soil area in southern China was collected and prepared to soil certified reference materials according to GB/T 15000 series rules.The collected material was dried at low temperature, ground, sieved, homogenized and radiation-sterilized.Twenty bottles of samples were randomly chosen in order to test the homogeneity.Results show that standard uncertainty due to between-bottle homogeneity ranges from 0.27% to 2.1% (in Table 2), indicating a good homogeneity.The minimum sampling weight was 0.2 g.X-ray Fluorescence Spectrometry method was used for long-term stability study.Stability was assessed by trend analysis, under the preservation conditions of room temperature without direct sunlight.No instability was observed during 12-month monitoring periods, and standard uncertainty due to long-term stability ranged from 0.06% to 2.1% (in Table 3).Elemental contents were determined by 13 laboratories using two different methods.The elements include Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Ti, Tl, V and Zn.Total uncertainty results from uncertainties in certificated values (uchar), between-bottle homogeneity (ubb) and long-term stability (ults).The expanded relative uncertainty of most elements is smaller than 7%, with the exception of Se.The reference material was approved as the national reference material (GSB 07-3272-2015).The presented CRMs were expected to be useful for method validation or quality control of heavy metal analysis in mining districts and surrounding areas by routine testing laboratories.%我国工矿开采区及周边地区已出现土壤重污染区和高风险区,这些区域是土壤环境监测的重要区域,但在实际环境监测中缺乏基体和污染特征相一致的污染场地土壤重金属元素分析标准样品.本文针对土壤重污染区和高风险区污染特征及实际环境监测需求,采集我国南方红壤区采矿企业周边的典型农田土壤,按照GB/T 15000导则和相关标准研制了污染场地土壤重金属元素分析标准样品.采集的土壤样品经低温烘干、研磨、筛分、混匀和辐照灭菌等加工处理,分层随机抽取20瓶子样进行均匀性研究,结果表明由均匀性引起的相对不确定度在0.27%~2.1%之间,样品均匀性良好,最小取样量为0.20 g.稳定性研究采用X射线荧光光谱法,数据评价采用趋势分析法,室温避光保存条件下,在12个月稳定性跟踪考察期间样品未观察到不稳定变化趋势,由稳定性性引起的相对不确定度在0.06%~2.1%之间.经13家有资质的实验室选用两种以上不同原理的高准确度方法对标准样品中21种元素(Ag、Al、As、Ba、Be、Cd、Co、Cr、Cu、Fe、Hg、Mn、Mo、Ni、Pb、Sb、Se、Ti、Tl、V、Zn)联合定值,总不确定度由定值不确定度(uchar)、瓶间均匀性不确定度(ubb)和长期稳定性不确定度(ults)合成,除Se外,其余元素的相对扩展不确定度均小于8%,表明标准样品定值准确,不确定度水平满足日常环境检测对土壤标准样品的要求.该标准样品被批准为国家实物标准样品(GSB 07-3272-2015),可用于分析方法验证或南方红壤区采矿及洗选企业周边土壤样品中重金属监测的质量控制.