Wang Fangli, Wang Xuexia, Song Ningning
Qingdao Engineering Research Center for Rural Environment, School of Resources and Environment, Qingdao Agricultural University, Qingdao 266109, PR China.
Institute of plant nutrition and resources, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, PR China.
Sci Total Environ. 2021 Aug 25;784:147133. doi: 10.1016/j.scitotenv.2021.147133. Epub 2021 Apr 16.
Little research has focused on the combined pollution of microplastics (MPs) and heavy metals in soil, especially the mechanism of their interaction. We conducted a 45-day microcosm experiment to test the hypothesis that polyethylene (PE) MPs and cadmium (Cd) had a joint toxicity to lettuce fitness. The effects of MPs at different addition ratios on Cd bioavailability and soil properties were also investigated in the microenvironment of three levels of Cd-contaminated soils. The results showed that the 10% MPs had an adverse impact on the plant biomass and significantly decreased soil pH and cation exchange capacity (CEC), but significantly increased soil dissolved organic carbon (DOC). The presence of MPs increased the soil Cd bioavailability and plant Cd concentrations and accumulations across all three levels of Cd-contaminated soils, which potentially aggregated the combined toxicity. The amounts of the bacterial 16SRNA and the fungal ITSRNA genes displayed a hormesis effect in response to the MP addition ratios while the abundance of Cd resistance genes cadA and czcA increased across all three Cd levels. The regression path analysis indicated that MPs affected shoot Cd concentrations by altering soil properties, which directly and indirectly contributed to the alteration mechanism, while the soil pH, DOC, and Cd bioavailability played core roles. The results suggest that the co-exposure of PE MPs in heavy metal-contaminated soil may therefore increase the toxicity, uptake, accumulation, and bioavailability of heavy metals by altering the properties of the soil microenvironment, which deserves further research.
很少有研究关注土壤中微塑料（MPs）和重金属的复合污染，尤其是它们的相互作用机制。我们进行了一项为期45天的微观实验，以验证聚乙烯（PE）微塑料和镉（Cd）对生菜健康具有联合毒性这一假设。在三种镉污染水平的土壤微环境中，还研究了不同添加比例的微塑料对镉生物有效性和土壤性质的影响。结果表明，10%的微塑料对植物生物量有不利影响，并显著降低了土壤pH值和阳离子交换容量（CEC），但显著增加了土壤溶解有机碳（DOC）。在所有三种镉污染水平的土壤中，微塑料的存在均增加了土壤镉生物有效性以及植物镉浓度和积累量，这可能加剧了联合毒性。细菌16S RNA和真菌ITS RNA基因的数量对微塑料添加比例呈现出 hormesis 效应，而在所有三种镉水平下，镉抗性基因cadA和czcA的丰度均增加。回归路径分析表明，微塑料通过改变土壤性质影响地上部镉浓度，这直接和间接地促成了这种变化机制，而土壤pH值、DOC和镉生物有效性发挥了核心作用。结果表明，在重金属污染土壤中共同暴露PE微塑料可能会通过改变土壤微环境性质增加重金属的毒性、吸收、积累和生物有效性，这值得进一步研究。
