Kan Junhong, Sima Jingke, Cao Xinde
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Ecotoxicol Environ Saf. 2017 Mar;137:158-164. doi: 10.1016/j.ecoenv.2016.11.025. Epub 2016 Dec 19.
Accidental ingestion of contaminated soil has been recognized as an important pathway of human exposure to lead (Pb), especially for children through hand-to-mouth activities. Intake of food following the soil ingestion may affect the bioaccessibility of Pb in the gastrointestinal tract. In this study, the effect of steamed bread on the transformation and subsequent bioaccessibility of Pb in two soils was determined by the physiologically based extraction test (PBET). Two compounds, Pb(NO) and PbCO, were included in the evaluation for comparison. In the gastric phase, Pb bioaccessibility decreased as the steamed bread increased due to the sorption of Pb on the undissolved steamed bread, especially in PbCO, Pb bioaccessibility decreased from 95.03% to 85.40%. Whereas in the intestinal phase, Pb bioaccessibility increased from 1.85% to 5.66% and from 0.89% to 1.80% for Pb(NO) and PbCO, respectively. The increase was attributed to the transformation of formed Pb carbonates into soluble organic-Pb complexes induced by the dissolved steamed bread at neutral pH as indicated by MINTEQ modeling. For the PbCO-contaminated soil, the change in Pb bioaccessibility in both gastric and intestinal phases behaved like that in the pure PbCO compound, the steamed bread increased the bioaccessibility of Pb in the intestinal phase, but the decreased bioaccessibility of Pb was observed in the gastric phase after the steamed bread was added. However, in the soil contaminated with free Pb or sorbed Pb forms, the steamed bread increased the Pb bioaccessibility in both gastric and intestinal phases. This was probably due to the higher dissolved organic carbon induced transformation of sorbed Pb (Pb sorbed by Fe/Mn oxides) into soluble Pb-organic complex. Results from this study indicated that steamed bread had an influence on the Pb speciation transformation, correspondingly affecting Pb bioaccessibility in the gastrointestinal tract.
意外摄入受污染土壤已被确认为人类接触铅（Pb）的重要途径，尤其是儿童通过手口活动接触铅。摄入土壤后再进食可能会影响胃肠道中铅的生物可及性。在本研究中，通过基于生理学的提取试验（PBET）确定了馒头对两种土壤中铅的转化及后续生物可及性的影响。评估中纳入了两种化合物Pb(NO)和PbCO进行比较。在胃阶段，由于铅吸附在未溶解的馒头上，随着馒头量增加，铅的生物可及性降低，尤其是在PbCO中，铅的生物可及性从95.03%降至85.40%。而在肠道阶段，对于Pb(NO)和PbCO，铅的生物可及性分别从1.85%增至5.66%和从0.89%增至1.80%。如MINTEQ模型所示，这种增加归因于在中性pH条件下，溶解的馒头诱导形成的碳酸铅转化为可溶性有机铅络合物。对于受PbCO污染的土壤，胃和肠道阶段铅生物可及性的变化与纯PbCO化合物中的情况相似，馒头增加了肠道阶段铅的生物可及性，但添加馒头后胃阶段铅的生物可及性降低。然而，在受游离铅或吸附态铅形式污染的土壤中，馒头增加了胃和肠道阶段铅的生物可及性。这可能是由于较高的溶解有机碳诱导吸附态铅（被铁/锰氧化物吸附的铅）转化为可溶性铅有机络合物。本研究结果表明，馒头对铅的形态转化有影响，相应地影响了胃肠道中铅的生物可及性。
