基于体外提取方法对土壤重金属生物可给性的研究与评价

发布时间：2018-01-25 05:09

本文关键词： 体外提取方法土壤重金属生物可给性风险评价　出处：《扬州大学》2015年硕士论文　论文类型：学位论文

【摘要】：重金属是一类在环境中广泛存在的污染物,具有较强的“三致”作用,土壤重金属常常经“手-口”途径进入人体,危害健康。生物可给性是人体健康风险评估中的重要评估因子,体外提取方法在评估重金属生物可给性时比动物试验简单、快捷且可避免伦理问题,因此显得尤为重要。本文运用国际上普遍采用的四种体外提取方法(UBM、PBET、SBET和IVG)针对土壤中重金属Zn、Ni、Cd和Pb的生物可给性进行了比较；利用PBET法分析了不同消化液(胃液和胃肠液)以及土壤性质对其产生的影响；探讨了内容物(面粉和茶多酚)的存在以及消化条件(胃液pH、土液比、停留时间)的改变对重金属生物可给性的影响；评价了扬州市城区土壤和灰尘中重金属的生物可给性及潜在健康风险；为合理评估土壤重金属对人体的健康风险提供科学依据。本研究主要得到以下结果：(1)4种体外消化方法对于酸性或碱性土壤中重金属Zn、Ni、 Cd和Pb的生物可给性大多存在显著性差异。IVG法对偏酸性土壤中Zn.Ni和Cd的提取量最大,分别为9.75、6.84和0.41 mg·kg-1,而SBET法对偏碱性土壤中Zn、Ni和Pb的提取量最大,分别为8.26、4.01和15.0 mg·kg-1。对于重金属Zn、Ni和Cd,采用IVG和PBET分析时,酸性土壤比碱性土壤的生物可给性高；用SBET和UBM分析时,则是碱性土壤高于酸性土壤。说明体外消化方法、重金属的种类以及土壤性质对重金属的生物可给性均有明显影响,评价时应予综合考虑。(2)基于PBET法分析时发现：Pb、Ni和Zn在胃相中的生物可给性高于胃肠相,Cu没有统一规律。Pb、Cu、Ni和Zn在胃相、胃肠相中的提取量与其相应全量呈正相关；除Pb外,Cu、Ni和Zn还与土壤有机质呈正相关、与土壤pH值呈负相关。为此,可用胃液消化过程替代胃肠液消化以简化体外消化试验,实现快速测定。(3)分别运用SBET和PBET法分析胃液中存在内容物(面粉或茶多酚)对重金属生物可给性的影响时发现：随面粉质量增加,Pb、Cu、 Ni和Zn的生物可给性均减小,两者有线性关系(R2均大于0.78)；随茶多酚质量增加,Pb、Cu和Zn的生物可给性亦减少,但Ni则呈增加趋势。(4)土壤重金属生物可给性受诸多因素影响：消化液pH值降低、土液比值减小、停留时间延长都可能使重金属生物可给性增加；所以评价重金属生物可给性时,要选择合适的胃液pH值、土液比和停留时间等试验条件。(5)用SBET和PBET法分析,运用美国EPA模型评价扬州市各功能区土壤中重金属Pb、Cu、Ni和Zn对人体的健康风险,结果发现：就各功能区而言,工业区土壤风险指数最大,商业区灰尘的风险指数最大；扬州市区土壤和灰尘中Pb对人体潜在危害最大、Zn最小；四种金属对人体的综合风险指数HI均小于1,说明小孩通过“手-口”途径意外摄入本地土壤和灰尘时,Pb、Cu、Ni和Zn没有非致癌风险。
[Abstract]:Heavy metals are a kind of pollutants widely existing in the environment, which have strong "three causes" effect. Soil heavy metals often enter the human body through the "hand-mouth" pathway. Bioavailability is an important assessment factor in human health risk assessment. In vitro extraction method is simpler than animal test in evaluating bioavailability of heavy metals and can avoid ethical problems. So it is very important. In this paper, four methods of in vitro extraction, UBMN PBETT SBET and IVG, were used to deal with the heavy metal Zn ~ (2 +) Ni in soil. The bioavailability of CD and Pb was compared. The effects of different digestive fluids (gastric juice and gastrointestinal fluid) and soil properties on their production were analyzed by PBET method. The effects of contents (flour and tea polyphenols) and digestion conditions (pH of gastric juice, ratio of soil to liquid, residence time) on bioavailability of heavy metals were discussed. The bioavailability and potential health risk of heavy metals in soil and dust of Yangzhou city were evaluated. In order to provide a scientific basis for evaluating the health risk of heavy metals in soil, the following results were obtained in this study: 1) in vitro digestion of Zn ~ (2 +) Ni in acidic or alkaline soils. There was significant difference in biodegradability between CD and Pb. Zn.Ni and CD extracted by IVG method were the largest, 9.75, respectively. 6.84 mg 路kg -1 and 0.41 mg 路kg -1, while the extraction amount of Zn Ni and Pb from alkaline soil by SBET method was 8.26 mg 路kg -1, respectively. 4.01 mg 路kg -1 and 15.0 mg 路kg -1. For heavy metals, IVG and PBET, the bioavailability of acidic soils was higher than that of alkaline soils. When SBET and UBM were used, alkaline soil was higher than acid soil, indicating that in vitro digestion method, heavy metal species and soil properties had a significant impact on the bioavailability of heavy metals. The biodegradability of Ni and Zn in stomach phase was higher than that in stomach phase. The extraction amount of Ni and Zn in gastric and gastrointestinal phase was positively correlated with the corresponding total amount. In addition to Pb, Cu Ni and Zn were positively correlated with soil organic matter and negatively correlated with soil pH. Therefore, gastric juice digestion could be used instead of gastrointestinal fluid digestion to simplify in vitro digestion test. SBET and PBET methods were used to analyze the effect of contents (flour or tea polyphenols) on the bioavailability of heavy metals in gastric juice. The biodegradability of Cu, Ni and Zn decreased, and the linear relationship between Cu, Ni and Zn was higher than 0.78. With the increase of tea polyphenols, the bioavailability of Cu and Zn also decreased, but Ni showed an increasing trend. 4) the bioavailability of heavy metals in soil was affected by many factors: the pH value of digestible solution decreased. The decrease of soil liquid ratio and the prolongation of residence time may increase the bioavailability of heavy metals. Therefore, when evaluating the bioavailability of heavy metals, we should choose the appropriate pH value of gastric juice, soil-liquid ratio and residence time. The EPA model was used to evaluate the health risk of heavy metals (Pb, Cu, Ni and Zn) in the soils of various functional areas in Yangzhou City. The results showed that the soil risk index of industrial area was the largest in terms of each functional area. The risk index of dust in commercial district is the largest; The potential harm of Pb to human body in soil and dust of Yangzhou urban area is the greatest and the least. The comprehensive risk index (HI) of the four metals to human body was less than 1, which indicated that there was no non-carcinogenic risk when children accidentally ingested local soil and dust by hand mouth route.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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