Microplastics (MPs) enter the global soil ecosystem in significant quantities, and in agricultural lands, interact with soil amendments (e.g, fertilisers, pesticides, biochar), pollutants (e.g., heavy metals and acid rain) and soil fauna (e.g., earthworms and microbial biomass) which impacts carbon (C) and nitrogen (N) cycling in soil in ways that are largely unexplored. Here, we analysed the difference in the responses of soil C and N contents, greenhouse gas emissions and soil enzyme activities in experiments where MPs alone or MPs in combination with other soil amendments or soil fauna had been explored, by conducting a global meta-analysis of 2543 observational data extracted from 84 published studies. The results show that MPs alone are associated with significantly increased soil C storage and altered soil N pool composition, increased soil carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions, reduced soil ammonia (NH₃) emissions, increased activity of one of the five major enzymes related to C cycle, and increased activity of three of the four major enzymes related to N cycling in soil. Experiments that explored the combined effects of MPs combined with fertilisers on soil C and N contents and enzyme activities indicated greater effects than MPs alone. However, the effects of MPs combined with soil fauna, heavy metals, acid rain, glyphosate, and carbon nanotubes on soil C and N cycling differed from findings of studies that considered the effects of MPs alone. The results of this meta-analysis provide a theoretical basis for further study of the effects of MPs on C and N cycling in fertilized agricultural soil, compound-contaminated soil and acidified soil. We also show that, despite the global importance of MPs in soil, the number of studies of their effects on soil C and N cycling is relatively few, and further research on the mechanisms of interactions of MPs with multiple soil amendments in soil systems is urgently needed.

中文翻译：

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在与土壤改良剂或土壤动物相互作用或不相互作用的情况下，微塑料对土壤 C 和 N 循环的影响

微塑料（MP）大量进入全球土壤生态系统，并在农田中与土壤改良剂（例如化肥、杀虫剂、生物炭）、污染物（例如重金属和酸雨）和土壤动物（例如蚯蚓和土壤动物）相互作用。微生物生物量），它以很大程度上尚未探索的方式影响土壤中的碳（C）和氮（N）循环。在这里，我们通过进行全球荟萃分析，分析了单独使用 MP 或与其他土壤改良剂或土壤动物组合探索 MP 的实验中土壤 C 和 N 含量、温室气体排放和土壤酶活性的响应差异。从 84 项已发表的研究中提取的 2543 项观察数据。结果表明，MPs 单独与显着增加的土壤碳储存和改变土壤氮库组成、增加土壤二氧化碳 (CO ₂ ) 和一氧化二氮 (N ₂ O) 排放、减少土壤氨 (NH ₃ ) 排放、增加活性有关。与碳循环相关的五种主要酶之一的活性增加，与土壤中氮循环相关的四种主要酶中的三种的活性增加。探索 MP 与肥料结合对土壤碳、氮含量和酶活性的综合影响的实验表明，MP 的效果比单独使用更大。然而，MPs与土壤动物、重金属、酸雨、草甘膦和碳纳米管结合对土壤碳氮循环的影响与单独考虑MPs影响的研究结果不同。该荟萃分析结果为进一步研究MPs对施肥农业土壤、化合物污染土壤和酸化土壤中C和N循环的影响提供了理论基础。我们还表明，尽管 MPs 在土壤中具有全球重要性，但其对土壤 C 和 N 循环影响的研究相对较少，迫切需要进一步研究 MPs 与土壤系统中多种土壤改良剂相互作用的机制。需要。