Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei Province, 430070, China.
Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei Province, 430070, China.
Environ Pollut. 2024 Sep 1;356:124315. doi: 10.1016/j.envpol.2024.124315. Epub 2024 Jun 6.
Large pieces of plastic are transformed into microplastic particles through weathering, abrasion, and ultraviolet radiation, significantly impacting the soil ecosystem. However, studies on biodegradable microplastics replacing traditional microplastics as agricultural mulching films to drive the biogeochemical processes influenced by GHG are still in their initial stages, with limited relevant reports available. This study sought to investigate the effects of microplastic and straw addition on CO and NO emissions in different soils. Herein, yellow-brown soil (S1) and fluvo-aquic soil (S2) were utilized, each treated with three different concentrations of PLA (polylactic acid) microplastics (0.25%, 2%, and 7% w/w) at 25 °C for 35 days, with and without straw addition. The results showed that straw (1% w/w) significantly increased soil CO by 4.1-fold and 3.2-fold, respectively, and NO by 1.8-fold and 1.8-fold, respectively, in cumulative emissions in S1 and S2 compared with the control. PLA microplastics significantly increased CO emissions by 71.5% and 99.0% and decreased NO emissions by 30.1% and 24.7% at a high concentration (7% w/w, PLA3) in S1 and S2 compared with the control, respectively. The same trend was observed with the addition of straw and microplastics together. Structural equation modeling and redundancy analysis confirmed that soil physiochemical parameters, enzyme and microbial activities are key factors regulating CO and NO emissions. The addition of microplastics is equivalent to the addition of carbon sources, which can significantly affect DOC, MBC, SOC and the abundance of carbon-associated bacteria (CbbL), thereby increasing soil CO emissions. The addition of microplastics alone inhibited the activity of nitrogen cycling enzymes (urease activity), increasing the abundance of denitrifying microbes. However, adding a high amount of microplastics and straw together released plastic additives, inhibiting microbial abundance and reducing the nitrogen cycle. These effects decreased NH-N and increased NO-N, resulting in decreased NO emissions. This study indicates that biodegradable microplastics could reduce soil plastic residue pollution through degradation. However, their use could also increase CO emissions and decrease NO emissions. Consequently, this research lays the groundwork for further investigation into the implications of utilizing biodegradable microplastics as agricultural mulch, particularly concerning soil geochemistry and GHG emissions.
大块塑料通过风化、磨损和紫外线辐射转化为微塑料颗粒，这对土壤生态系统有重大影响。然而，关于可生物降解微塑料替代传统微塑料作为农业覆盖薄膜来驱动受温室气体影响的生物地球化学过程的研究仍处于起步阶段，相关报告有限。本研究旨在调查微塑料和秸秆添加对不同土壤中 CO 和 NO 排放的影响。本文利用黄棕壤（S1）和潮土（S2），在 25°C 下处理了三种不同浓度的 PLA（聚乳酸）微塑料（0.25%、2%和 7%w/w），并分别添加和不添加秸秆，共 35 天。结果表明，与对照相比，秸秆（1%w/w）分别使 S1 和 S2 的土壤 CO 累积排放增加了 4.1 倍和 3.2 倍，NO 增加了 1.8 倍和 1.8 倍。PLA 微塑料在高浓度（7%w/w，PLA3）下使 S1 和 S2 中的 CO 排放分别增加了 71.5%和 99.0%，使 NO 排放分别减少了 30.1%和 24.7%，而添加秸秆和微塑料的效果相同。结构方程模型和冗余分析证实，土壤理化参数、酶和微生物活性是调节 CO 和 NO 排放的关键因素。微塑料的添加相当于添加了碳源，这可以显著影响 DOC、MBC、SOC 和与碳相关的细菌（CbbL）的丰度，从而增加土壤 CO 排放。单独添加微塑料会抑制氮循环酶（脲酶活性）的活性，增加反硝化微生物的丰度。然而，添加大量微塑料和秸秆会释放塑料添加剂，抑制微生物丰度并减少氮循环。这些影响降低了 NH-N 并增加了 NO-N，导致 NO 排放减少。本研究表明，可生物降解微塑料可以通过降解减少土壤塑料残留污染。然而，它们的使用也可能增加 CO 排放并减少 NO 排放。因此，本研究为进一步研究利用可生物降解微塑料作为农业覆盖物的影响奠定了基础，特别是涉及土壤地球化学和温室气体排放。
