近年来，温室气体排放增加导致全球气候变化已经成为全球的研究热点。二氧化碳（CO₂）和一氧化二氮（N₂O）是导致全球变暖的两种主要的温室气体。IPCC第四次报告中指出，农业是最重要的温室气体排放源之一。为了缓解全球气候变暖，施加土壤改良剂影响土壤中的碳氮循环而抑制土壤排放温室气体非常必要。生物炭是一种富碳材料，具有丰富的孔隙结构和官能团，理化性质稳定，且生物炭已被广泛地应用于土壤中，用于改善土壤肥力，增加土壤有机碳，减少温室气体排放，调节土壤酸性和提高土壤持水能力等。塑料是人类生活中必不可少的一部分，迄今为止全球每年的塑料产量超过3亿吨，且有＞30%的塑料因不当处理最终积累在陆地生态系统中。并且随着农业地膜覆盖的广泛应用，微塑料作为一种新兴污染物在土壤中广泛存在。所以微塑料和生物炭在土壤中共存将在未来变得更加普遍，然而，关于微塑料（MPs）和生物炭（BC）对土壤微生物群落和N₂O/CO₂排放联合影响的研究很少。
因此本研究将采集自田间的新鲜生物炭（1个月）和老化生物炭（14年）土壤与两种浓度（1%、5%，w/w）的PE微塑料混合后在40%持水率20℃的黑暗环境中进行为期91天的温室培育实验，测定期间温室气体的排放量，表明新鲜/老化生物炭和微塑料处理对土壤温室气体排放的影响，并通过测定土壤理化性质和微生物群落变化，结合冗余分析、主坐标分析和相关性分析探究其影响机理。本研究的主要结果和主要结论如下：
（1）新鲜BC、老化BC、PE单独或共同存在下对土壤pH值无显著影响。BC特别是老化BC抑制了土壤中大团聚体的形成，而促进了微团聚体的形成。老化BC土壤中大团聚体（＞2 mm）占比减少81%，小团聚体（0.25~2 mm）的比例减少32%，而微团聚体（＜0.25 mm）的比例增加了986%。PE微塑料促进对照组和新鲜BC土壤中大团聚体的形成。而引起老化BC土壤中的小团聚体增加和微团聚体减少。新鲜BC使土壤中溶解性有机碳（DOC）含量下降，并增强了溶解性有机质（DOM）的芳香性。PE微塑料使对照组和新鲜BC土壤的DOM芳香性降低，使老化BC土壤中DOM芳香性增强。
（2）新鲜BC促进了土壤β-葡萄糖苷酶（BG）活性，而老化BC则抑制了BG活性。新鲜BC和老化BC均抑制了土壤N-乙酰-β-D-葡萄糖苷酶（NAG）活性。PE对BG酶无显著作用，抑制了北京对照和新鲜BC土壤中的NAG酶活性，促进了老化BC土壤中的NAG酶活性。新鲜/老化BC和PE的添加均使土壤微生物群落发生了显著变化。
（3）与新鲜BC相比，老化BC抑制土壤CO₂和N₂O排放的效果更好。PE的添加抑制了对照组和新鲜生物炭土壤的CO₂和N₂O排放，但增加了老化生物炭土壤的CO₂和N₂O排放。新鲜BC和PE对CO₂和N₂O排放的总体抑制作用是由于降低了土壤聚集性，增强了DOM芳香性，从而抑制了微生物种群数量、酶活性和C、N代谢相关功能基因的表达。而PE在老化生物炭土壤中的促进作用则相反。新鲜BC通过抑制微生物体内周转和体外修饰来抑制微生物残体碳（MNC）的积累，而老化BC通过降低土壤聚集来实现MNC的净积累，从而更好地保护MNC，降低分解微MNC的酶活性，并提高MNC产生的碳利用效率。在新鲜生物炭土壤中，PE的添加通过降低土壤聚集性和酶活性促进了MNC的积累，而在老化生物炭土壤中则相反。MNC的积累驱动DOM的多样化，影响土壤微生物的资源有效性，从而影响土壤碳氮动态。这些研究结果加深了我们对生物炭土壤系统对微塑料干扰的恢复能力的理解，并有助于调整生物炭施用策略以更好地管理土壤碳。
 

In recent years, global climate change caused by the increase of greenhouse gas emissions has attracted great attention. Carbon dioxide (CO₂) and Nitrous oxide (N₂O) is the two main greenhouse gases that contribute to global warming. The IPCC has reported that agriculture is one of the most important sources of greenhouse gas emissions. In order to mitigate global warming, it is necessary to apply soil amendments to affect carbon and nitrogen cycling in soil and reduce greenhouse gas emissions from soil. Biochar is a kind of carbon-rich material with abundant pore structure, functional groups and stable physico-chemical properties. Biochar (BC) has been widely used in soil to improve soil fertility, increase soil organic carbon, reduce greenhouse gas emissions, regulate soil acidity and improve soil water holding capacity. Plastic is an essential part of human life. There are more than 300 million tons of plastics produced annually around the world and > 30% of plastic ends up in terrestrial ecosystems due to improper disposal. With the widespread application of agricultural plastic mulching, microplastics has existed widely in soil as an emerging pollutant. So the co-existence of microplastics and biochar in soil will become more common in the future. However, there are few studies on the combined effects of microplastics and biochar on soil microbial communities and N₂O/CO₂ emissions.
    In this study fresh BC (1 month) and aged BC (14 years) was combined with two concentrations of polyethylene (PE) microplastics (MPs) (1%, 5%, w/w) separately to conduct an incubation experiment in a dark environment with a 40% water holding capacity and 20℃. The incubation experiment lasted 91 days. The analysis methods including redundancy analysis, principal coordinate analysis and correlation analysis were used to reveal the effect of co-existence of PE MPs and BC on soil greenhouse gas emissions. The main results and conclusions of this study are as follows:
(1) Fresh BC, aged BC and PE MPs had no significant effect on soil pH alone or together. BC, especially aged BC decreased the formation of large macroaggregates and promoted the formation of microaggregates. The proportion of large macroaggregates (> 2 mm) decreased by 81%, that of small macroaggregates (0.25-2 mm) decreased by 32%, and that of microaggregates (< 0.25 mm) increased by 986% in aged BC soils. PE MPs promoted the formation of large macroaggregates in control and fresh BC soils. PE MPs increased the proportion of small macroaggregates and decreased the proportion of microaggregates in age BC soils. Fresh BC reduced the content of soil dissolved organic carbon (DOC) and enhanced the aromaticity of dissolved organic matter (DOM). PE MPs reduced the aromaticity of DOM in control and fresh BC soils, but increased the aromaticity of DOM in aged BC soils.
(2) Fresh BC promoted soil β-glucosidase (BC) activity, while aging BC inhibited BG activity. Both fresh and aged BC inhibited the activity of N-acetyl-β-D-glucosidase (NAG) in soil. PE MPs had no significant effect on BG enzyme activity and inhibited NAG enzyme activity in Beijing control and fresh BC soil, but promoted NAG enzyme activity in aged BC soil. The addition of fresh/aged BC and PE MPs significantly changed the soil microbial community.
(3) The results showed that aged BC was more effective in suppressing soil CO₂ and N₂O emissions than fresh BC. PE addition suppressed CO₂ and N₂O emissions in the control and fresh BC soils, but enhanced them in aged BC soil. The overall inhibition effects on CO₂ and N₂O emissions by biochar and polyethylene were due to the decreased soil aggregation, enhanced DOM aromaticity, which inhibited microbial population, enzyme activity and expression of functional genes related to C and N metabolism. However, the opposite was observed for the promotion effects by polyethylene in aged BC soil. Fresh BC inhibited microbial necromass carbon (MNC) accumulation by suppressing in vivo turnover and ex vivo modification, while aged BC resulted in net MNC accumulation by lowering soil aggregation for better MNC protection, decreasing enzyme activity responsible for MNC decomposition, and enhancing the carbon use efficiency for MNC production. PE addition enhanced MNC accumulation in fresh BC soil by decreasing soil aggregation and enzyme activity, while the opposite was observed for aged BC soil. The accumulation of MNC drove the microbial diversification of DOM and affected the resource availability for soil microbes, thereby influencing soil C and N dynamics. These findings advanced our understanding of the ecosystem resilience of BC soil system to microplastic disturbance and aid in adjusting BC application strategies for better soil C management.