微塑料对环境介质中氮循环的影响研究进展

微塑料作为一种新污染物，在全球范围内引发了广泛关注.微塑料在威胁生物体健康的同时，也会通过定殖微生物等途径影响氮素正常的循环过程，但相关研究仍相对匮乏.本文在简述当前微塑料污染现状的基础上，介绍了微塑料对污泥、水、沉积物和土壤4种环境介质中氮循环的影响研究进展，并重点分析了微塑料作用下不同环境介质中氮转化过程的响应及作用机制.结果表明:当前微塑料影响氮循环的研究主要集中于污泥和土壤，对水环境和沉积物中的研究相对较少；环境介质和微塑料的聚合物类型、浓度、粒径等因素都会导致微塑料对氮循环的影响产生明显差异.进一步分析发现，微塑料主要通过影响氮转化相关的微生物、酶活性和功能基因以及改变氧通量等来影响硝化和反硝化等过程，其中，微生物受塑料添加剂释放的影响较大，微塑料自身也可能作为有机底物促进相关功能菌的生长；硝化和反硝化过程中关键酶及功能基因也会对微塑料的影响产生响应，进而影响氮循环过程.此外，微塑料能够通过改变沉积物的孔隙度增加氧通量，增强硝化作用.在后续研究中应重点关注微塑料参与氮循环的环境驱动机制，阐述其在潜流带等地球关键带中的作用路径，为全面评估微塑料对生态环境健康的影响提供支持. 

Influence of Microplastics on Nitrogen Cycle in Different Environments

Microplastic, as an emerging pollutant, has received increasing concerns worldwide. In addition to threatening the health of organisms, microplastics may also affect the nitrogen cycles by altering the colonized biofilms. However, the relevant research is relatively scarce. Based on the microplastic pollution status in different environments, the impact of microplastics on nitrogen transformation in different environmental media (e.g., sludge, water, sediment, and soil) was introduced. Then, the response and transformation mechanism were analyzed in detail. It is found that previous studies mainly focused on the influence impact of microplastics on the nitrogen cycle in sludge and soil, while few of them were conducted in water and sediment. Many influencing factors, including environmental media, polymers, concentration, and size of microplastics, can significantly change the impact of microplastics on the nitrogen cycle. Generally, microplastics can affect the processes of nitrification and denitrification in the environments by affecting the microbial community, enzyme activities, and functional genes related to nitrogen transformation, as well as changing the oxygen flux. The microbial community was mainly affected by the additives released from the microplastics. In addition, microplastics may also promote the growth of the related microbial communities as an organic substrate. Furthermore, microplastics can increase oxygen flux by changing the porosity of the sediment, thereby enhancing nitrification. In the future, more attention should be paid to the impact of microplastics on the nitrogen cycle under different environmental factors or in the critical zones of the earth, such as the hyporheic zone. These results are useful to comprehensively assess the impact of microplastics on ecological and environmental health.