Hamel S C, Ellickson K M, Lioy P J
Department of Plant Sciences, Rutgers, State University of New Jersey, New Brunswick 08901-8520, USA.
Sci Total Environ. 1999 Dec 15;243-244:273-83. doi: 10.1016/s0048-9697(99)00402-7.
The possible human health effects resulting from the ingestion of soil bound heavy metals can be poorly estimated if concentration of total metals in soil, rather than bioavailable fraction of metals, are incorporated into dose calculations. Information regarding bioavailability often is obtained from animal studies, which are not easily conducted and still may not represent human conditions. A rapid simulation of the bioaccessible fraction of contaminant in a soil, in which that fraction is mass soluble in gastrointestinal tract fluids, has been employed in an in vitro sequential extraction technique. Using a mass-balance analytical approach to measure bioaccessibility in four soils, the results indicated that each metal had a bioaccessible fraction less than its total metal content. Lead (Pb) in Standard Reference Material, Montana SRM 2710, was found to be 62 +/- 1% bioaccessible; Pb in contaminated soil collected from Bunker Hill, ID, USA was 70 +/- 11%. Lead in Jersey City, NJ, USA slag material was only 39 +/- 14% bioaccessible while Pb in a residential soil was 69%. Arsenic (As) and chromium (Cr) data from select soils also have bioaccessibility less than the corresponding total metal in soil, with 41 +/- 2% As in a residential soil, 66 +/- 8% As in SRM 2710, and 34 +/- 14% Cr in Jersey City slag material. Recovering the soil at the end of the in vitro extraction allowed for the determination of the insoluble fraction of total metal in soil. This recaptured soil metal mass was a valuable measurement since it greatly reduced analysis and therefore labor and time, yet also provided a reasonable estimate of bioaccessibility. It also allowed for calculation of a bioaccessibility value in a soil containing very low metal mass, which would otherwise have resulted in a non-detectable concentration at the dilutions required in the synthetic human biofluid system.
如果在剂量计算中纳入的是土壤中总金属的浓度，而非金属的生物可利用部分，那么因摄入与土壤结合的重金属而可能对人体健康产生的影响就很难准确估算。关于生物可利用性的信息通常来自动物研究，这类研究不易开展，而且可能仍无法代表人类的实际情况。体外连续萃取技术采用了一种快速模拟土壤中污染物生物可及部分的方法，该部分是指在胃肠道液体中可溶解的质量部分。通过质量平衡分析方法来测量四种土壤中的生物可及性，结果表明每种金属的生物可及部分都小于其总金属含量。标准参考物质蒙大拿州标准参考物质2710中的铅（Pb），其生物可及性为62±1%；从美国爱达荷州邦克山采集的受污染土壤中的铅为70±11%。美国新泽西州泽西城矿渣材料中的铅生物可及性仅为39±14%，而住宅土壤中的铅为69%。部分土壤中砷（As）和铬（Cr）的数据显示，其生物可及性也低于土壤中相应的总金属含量，住宅土壤中的砷为41±2%，标准参考物质2710中的砷为66±8%，泽西城矿渣材料中的铬为34±14%。体外萃取结束时回收土壤，有助于测定土壤中总金属的不可溶部分。回收的土壤金属质量是一项有价值的测量结果，因为它大大减少了分析工作，进而减少了劳动力和时间，同时还能对生物可及性做出合理估算。它还能计算出金属质量极低的土壤中的生物可及性值，否则在合成人体生物流体系统所需的稀释度下，该浓度将无法检测到。
