三种模拟消化液对土壤重金属的提取性比较

为了解不同方法的模拟消化液对土壤重金属提取性的差异性,比较了国际上广泛使用的3种代表性体外消化方法的模拟消化液(SBET, Simple Bioaccessibility Extraction Test;PBET, Physiologically-Based Extraction Test;SGET, Simple Gastrointestinal Extraction Test)对土壤中Cu、Zn、Pb和Cd的溶解效果.结果表明,3种方法的模拟消化液对土壤重金属的提取效果存在显著的差异.其中,3种模拟消化液对土壤中Zn和Cd的提取能力顺序为SBET>PBET>SGET;当胃液消化物进入肠液后,土壤中Zn、Cd和Pb在PBET及SGET中的溶解度都显著降低,而对于Cu,由于消化酶(胃蛋白酶、胰液素和胆汁盐)的络合作用,其在肠液中的溶解度不一定低于相应的胃液,因此土壤中Zn、Pb和Cd在胃液中的溶解度代表其在消化道中能被吸收的最大值,即其有可能被人体吸收的最大量.所以出于预防和保护的目的,在土壤重金属污染健康风险评价中可用只含有胃液的模拟消化液(如SBET法)评估土壤Zn、Cd和Pb的生物可接受性,但胃液中的提取量并不一定能代表土壤Cu在消化道中能被吸收的最大值,建议使用由胃液和肠液组成,且添加了相应消化酶的模拟消化液(如PBET法)对其生物可接受性进行评估.

Comparison of soil heavy metals extraction using three in-vitro digestion tests

To compare the extraction efficiency of different in-vitro digestion tests, three representative and universally used in-vitro digestion tests (SBET, Simple Bioaccessibility Extraction Test; PBET, Physiologically-Based Extraction Test; SGET, Simple Gastrointestinal Extraction Test) were chosen to evaluate the bioaccessibility of soil Cu, Zn, Pb and Cd. Significant differences among extraction ability of three in-vitro digestion tests were found, and the extraction ability of three in-vitro digestion tests for soil Zn and Cd in descending order was: SBET>PBET>SGET. Although the bioaccessibility of soil Zn, Pb and Cd in the gastric phase of PBET and SGET were clearly higher than those in the corresponding gastrointestinal phase, the bioaccessibility of soil Cu in the gastric phase could be less than those in the corresponding gastrointestinal phase due to the complexation with digestive enzymes (pepsin, bile salts and pancreatin). Then it is known the solubility of soil Zn, Pb and Cd in the gastric phase can represent their maximum absorbable amounts in digestive tract, while the solubility of soil Cu in the gastric phase can not. Therefore, the bioaccessibility of soil Zn, Pb and Cd can be evaluated only using gastric juice, like SBET, but soil Cu bioaccessiblity should be evaluated by synthetic digestive juice composed of gastrointestinal juice with corresponding digestive enzymes (pepsin, bile salts and pancreatin), like PBET.