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首页> 外文期刊>Reviews of environmental contamination and toxicology >Bioavailability of xenobiotics in the soil environment.
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Bioavailability of xenobiotics in the soil environment.

机译：异种生物在土壤环境中的生物利用度。

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It is often presumed that all chemicals in soil are available to microorganisms, plant roots, and soil fauna via dermal exposure. Subsequent bioaccumulation through the food chain may then result in exposure to higher organisms. Using the presumption of total availability, national governments reduce environmental threshold levels of regulated chemicals by increasing guideline safety margins. However, evidence shows that chemical residues in the soil environment are not always bioavailable. Hence, actual chemical exposure levels of biota are much less than concentrations present in soil would suggest. Because "bioavailability" conveys meaning that combines implications of chemical sol persistency, efficacy, and toxicity, insights on the magnitude of a chemicals soil bioavailability is valuable. however, soil bioavailability of chemicals is a complex topic, and is affected by chemical properties, soil properties, species exposed, climate, and interaction processes. In this review, the state-of-art scientific basis for bioavailability is addressed. Key points covered include: definition, factors affecting bioavailability, equations governing key transport and distributive kinetics, and primary methods for estimating bioavailability. Primary transport mechanisms in living organisms, critical to an understanding of bioavailability, also presage the review. Transport of lipophilic chemicals occurs mainly by passive diffusion for all microorganisms, plants, and soil fauna. Therefore, the distribution of a chemical between organisms and soil (bioavailable proportion) follows partition equilibrium theory. However, a chemical's bioavailability does not always follow partition equilibrium theory because of other interactions with soil, such as soil sorption, hysteretic desorption, effects of surfactants in pore water, formation of "bound residue", etc. Bioassays for estimating chemical bioavailability have been introduced with several targeted endpoints: microbial degradation, uptake by higher plants and soil fauna, and toxicity to organisms. However, there bioassays are often time consuming and laborious. Thus, mild extraction methods have been employed to estimate bioavailability of chemicals. Mild methods include sequential extraction using alcohols, hexane/water, supercritical fluids (carbon dioxide), aqueous hydroxypropyl-beta-cyclodextrin extraction, polymeric TENAX beads extraction, and poly(dimethylsiloxane)-coated solid-phase microextraction. It should be noted that mild extraction methods may predict bioavailability at the moment when measurements are carried out, but not the changes in bioavailability that may occur over time. Simulation models are needed to estimate better bioavailability as a function of exposure time.
机译：通常认为，土壤中的所有化学物质都可以通过皮肤暴露给微生物，植物的根和土壤动物。随后通过食物链进行的生物蓄积可能导致接触高等生物。各国政府使用总可用量的假设，通过增加准则的安全余量来降低受管制化学品的环境阈值水平。但是，有证据表明，土壤环境中的化学残留物并非总是可生物利用的。因此，生物群的实际化学暴露水平远低于土壤中所暗示的浓度。由于“生物利用度”传达的含义结合了化学溶胶的持久性，功效和毒性，因此对化学土壤生物利用度的认识是有价值的。然而，化学物质在土壤中的生物利用度是一个复杂的话题，并受化学性质，土壤性质，暴露的物种，气候和相互作用过程的影响。在这篇综述中，讨论了生物利用度的最新科学基础。涵盖的关键点包括：定义，影响生物利用度的因素，控制关键运输和分布动力学的方程式以及估算生物利用度的主要方法。对于理解生物利用度至关重要的活生物体中的主要转运机制，也预示了此次审查。亲脂性化学物质的运输主要通过所有微生物，植物和土壤动物的被动扩散发生。因此，化学物质在生物和土壤之间的分布（生物可利用比例）遵循分配平衡理论。但是，由于与土壤的其他相互作用，例如土壤吸附，滞后解吸，表面活性剂在孔隙水中的作用，“结合残留物”的形成等，化学物质的生物利用度并不总是遵循分配平衡理论。引入了几个目标指标：微生物降解，高等植物和土壤动物的吸收以及对生物的毒性。然而，那里的生物测定通常是费时且费力的。因此，已经采用温和的提取方法来估计化学品的生物利用度。温和的方法包括使用酒精，己烷/水，超临界流体（二氧化碳），羟丙基-β-环糊精水溶液的萃取，聚合的TENAX珠粒萃取和涂有聚（二甲基硅氧烷）的固相微萃取进行顺序萃取。应该注意的是，温和的提取方法可以预测进行测量时的生物利用度，但不能预测生物利用度随时间的变化。需要模拟模型来估计更好的生物利用度，作为暴露时间的函数。

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