我国污染地块土壤砷生物可给性关键影响因素研究

Study on Key Factors Affecting Arsenic Bioaccessbility in Contaminated Sites in China

土壤砷生物可给性是砷污染地块风险评估的关键影响因素,与土壤理化性质、相关金属含量、砷生物可给性测试方法密切相关。本研究对污染地块土壤砷生物可给性相关研究进行系统的文献调研,收集土壤砷生物可给性、土壤理化性质(pH、有机质、黏粒含量等)、土壤中金属(As、Fe、Al及Mn)含量和可给性测试方法,采用相关性分析、主成分分析及生存分析方法研究污染地块土壤砷生物可给性关键影响因素和主要机制。结果表明:土壤砷生物可给性与土壤pH及粉粒含量均呈显著正相关(P<0.001),与砂粒含量均呈显著负相关(P<0.001)。主成分分析表明,土壤pH、粉粒含量对胃、肠阶段砷生物可给性具有重要的正向贡献,说明低土壤pH、细土壤粒径能够降低砷生物可给性。生存分析表明,土壤pH对胃阶段砷生物可给性影响显著(P<0.001),对肠阶段砷生物可给性影响不显著;高黏粒含量会降低胃、肠阶段砷生物可给性。蒙特卡罗模拟表明,我国污染地块土壤砷生物可给性随机抽样的95%分位值最高为64.8%,低反应pH与高固液比可能使测得的砷生物可给性偏高。研究显示,胃阶段、肠阶段砷生物可给性的主要影响因素较为一致,包括土壤pH、粒径、As含量;pH<6.5的土壤相较pH>6.5的土壤胃阶段砷生物可给性显著差异较低,肠阶段差异不明显;我国污染地块砷生物可给性超过65%的概率低于5%,推荐使用65%作为我国污染地块土壤砷生物可给性的默认参数。

Soil arsenic bioaccessibility is a key influencing factor in the environmental risk assessment of arsenic-contaminated sites and is closely related to soil physicochemical properties,metal content,and bioaccessibility in vitro testing methods.This study conducted a systematic literature review on the bioaccessibility of arsenic in contaminated sites,and compiled the arsenic bioaccessibility in the gastric stage and intestinal stage,soil physicochemical properties(pH,organic matter,clay content,etc.),soil metal(As,Fe,Al and Mn)content,and in vitro bioaccessibility test methods.Correlation analysis,principal component analysis and survival analysis were used to study the key factors and mechanisms affecting soil arsenic bioaccessibility.The results showed that soil arsenic bioaccessibility was positively correlated with soil pH and powder content(P<0.001),and negatively correlated with sand content(P<0.001).Principal component analysis showed that soil pH and silts content had significant positive contributions to the bioaccessibility of the gastric and intestinal stages,indicating that low soil pH and high silts content could reduce arsenic bioaccessibility.Survival analysis showed that soil pH had a significant effect on arsenic bioaccessibility at the gastric stage(P<0.001),but not at the intestinal stage,and high clay particle content reduced arsenic bioaccessibility in the gastric and intestinal stages.Monte Carlo simulation showed that the highest 95% quantile value of arsenic bioaccessibility in randomly sampled soil from contaminated sites in China was 64.8%,and low reaction pH and high solid-to-liquid ratio may cause the measured arsenic bioaccessibility to be higher.The study showed that the main influencing factors of arsenic bioaccessibility in the stomach and intestinal phases were relatively consistent,including soil pH,particle size,and arsenic content.A noteworthy difference was observed in arsenic bioaccessibility in soils with a pH below 6.5 compared with soils with a pH above 6.5 during the gastric phase,while the difference in the intestinal phase was less significant.The probability of arsenic bioaccessibility exceeding 65% in contaminated sites across China was less than 5%.Based on this finding,we recommend using 65% as the default parameter for soil arsenic bioaccessibility in contaminated sites in China.The results of this study provide a scientific basis for predicting soil arsenic bioaccessibility and calculating the actual human health risks of contaminated sites.