类固醇雌激素在土壤-植物体系中的迁移转化及其毒理效应

类固醇雌激素(steroidal estrogens, SEs)作为典型的内分泌干扰物,在环境介质中被广泛检出,其进入生物体后可模拟细胞内源性激素作用对生物体生长、发育、生殖等产生不利影响,因此越来越引起关注。目前关于SEs的研究报道多集中于粪便、土壤、水体等介质中的检出及环境行为,以及SEs在水生生物体内的迁移和转化,其累积效应及其机制研究较为系统和全面。相较而言,SEs在土壤-植物体系中的迁移累积报道较少,但是对于掌握农田系统中SEs迁移转化的需求更为迫切。结合现有的国内外相关研究,总结了SEs在土壤-植物体系中的吸收累积和迁移转化行为特征,概述了植物吸收代谢SEs的影响因素以及SEs对植物生长发育的毒理效应。目前针对SEs的植物体吸收大多数仍基于室内模拟实验,对于其在土壤-植物多相态体系中迁移转化机理尚不清楚。因此,对今后的研究方向提出以下几点建议:(1)除室内模拟实验外,对实际土壤-植物系统中的研究更具价值,特别是SEs土壤-土壤水-植物多相态体系中的迁移转化等过程;(2)应结合SEs的来源,探究畜禽粪便、城市污泥及污水等不同源SEs对植物吸收、累积污染物的影响及污染风险;(3)加强对农作物体内SEs残留的监测和风险评估,制定SEs农作物检出及人体摄入的相关标准。

Transport and transformation of steroid estrogens in soil-plant systems and their toxicological effects on plant

Steroid estrogens (SEs) are widespread in the environment as endocrine disrupting chemicals. After entering the body of an organism, SEs simulate the action of endogenous hormones or modulate their activity, which adversely affects the growth, development, and reproduction of the organism; thus, SEs have gained increasing attention recently. Currently, most studies on SEs focus on their detection and environmental behavior, as well as on the transport and transformation of SEs in aquatic organisms. However, some studies have reported on the transport and accumulation of SEs in soil-plant systems, which is more important to understand the potential risks of SEs in human health. In this study, the uptake, accumulation, transport, transformation, and metabolism of SEs in soil-plant systems and the factors that influence them have been reviewed based on the current related researches. The uptake of SEs by plants exhibits a dose-dependent effect. After being absorbed by plant roots, SEs can further migrate to the aboveground parts, but due to their strong hydrophobicity, they will tend to accumulate in the roots. The transformation and metabolism of SEs may mainly result from catalytic degradation of plant enzymes and/or symbiotic microorganisms by plants. Unlike a relatively simple medium in hydroponic experiments, soil-plant-microbial systems are more complex, and SEs may exhibit a series of multiphase distribution and transformation behaviors, which are determined by the combination of properties of SEs, soils, and plants. In addition, we have summarized the influences of SEs on plant growth, development, and antioxidant activities. Treatment of plants with SEs can affect root and shoot development, which may be related to plant species, culture conditions (e.g. culture time, temperature or humidity) and the treated concentration of target SEs. Moreover, when SEs coexist with heavy metals, they can ameliorate the toxic effects of heavy metals on plants. For better understanding the mechanisms of SEs described above, we have suggested the following research strategies: 1) to investigate the environmental behaviors of SEs in the actual soil-plant systems, especially the transport and transformation processes of SEs among soil-water-plant multiphase systems, which is more relevant than the simulation experiments in laboratory; 2) to examine the pollution risks from different SEs sources and their impacts on the plant uptake and accumulation of contaminants, which usually coexist and interact with SEs; 3) to set a threshold level for uptake of SEs that pose no detrimental effects to human health via enriching the available monitoring data and enhancing risk assessment of SE residues in crops.