Bioaccessibility of polychlorinated biphenyls in different foods using an in vitro digestion method

Bioaccessibility of organic pollutants in food is important for exposure estimation and risk assessment. An in vitro enzyme digestion experiment was carried out to analyze the bioaccessibility of PCBs in different foods including freshwater fish (bighead carp and oriental weather fish) and vegetables (spinach and cabbage). The results indicated that the bioaccessibility of PCBs in freshwater fish (3%) was much lower than that in leafy vegetables (25%). Based on field survey, the daily exposure TEQ value from these two types of food was 17.9 pg/kg bw/day. However, when bioaccessibility was taken into consideration, the value decreased to 0.61 pg/kg bw/day. Therefore, the forms of PCBs existing in food strongly influenced the bioavailability for humans, which may have important implications on dietary exposure. To our knowledge, this is the first paper to illustrate the bioaccessibility of PCBs in different foods using an in vitro digestion method.     

城市化对河流着生硅藻物种和功能多样性的影响——以深圳市河流为例

着生藻类是河流生态系统的主要初级生产者,了解城市化对着生藻类多样性的影响对于城市河流管理具有重要意义.本研究以深圳市河流为例,研究了河流着生硅藻性状及物种、功能多样性对城市干扰的响应.研究发现城区和郊区的水质状况差异显著.城区样点的NH₄⁺-N、NO₂-N、TN、TP和DOC浓度是郊区的3～20倍不等.水环境的巨大变化也导致了河流着生藻类生物多样性的变化.城区组物种丰富度、Pielou指数和Simpson指数均显著高于郊区组,而功能均匀度则显著低于郊区组.并且在21个硅藻性状中,有15个性状在城区和郊区组间存在显著差异.进一步用随机森林模型拟合着生藻类生物多样性与水质指标的关系,结果发现硅藻性状对城市化反应较其他指标更为敏感.特别是小型、可动、低共位群和运动群这4个性状指标,构建的随机森林模型解释率能达到40%～60%,而生物多样性指数构建的模型解释率只有15%～25%左右.总体来说,TP和TN是影响城市河流着生硅藻多样性的主要水质指标.在营养水平高的城市样点.个体较大、能够移动的硅藻占有主导地位;而在营养水平较低的郊区...