Collaborative Innovation Center for Modern Crop Production co-sponsored by Province and Ministry, College of Agriculture, Nanjing Agricultural University, Nanjing 210095, China.
Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Sci Total Environ. 2024 Dec 1;954:176273. doi: 10.1016/j.scitotenv.2024.176273. Epub 2024 Sep 14.
The priming effect, i.e., the changes in soil organic matter (SOM) decomposition following fresh organic carbon (C) inputs is known to influence C storage in terrestrial ecosystems. Microplastics (particle size <5 mm) are ubiquitous in soils due to the increasing use and often inadequate end-of-life management of plastics. Conventional polyethylene and bio-degradable (PHBV) plastics contain large amounts of C within their molecular structure, which can be assimilated by microorganisms. However, the extent and direction of the potential priming effect induced by microplastics is unclear. As such, we added C-labeled glucose to investigate how background polyethylene and PHBV microplastics (1 %, w/w) affect SOM decomposition and its potential microbial mechanisms in a short-term. The cumulative CO emission in soil contaminated with PHBV was 42-53 % higher than under Polyethylene contaminated soil after 60-day incubation. Addition of glucose increased SOM decomposition and induced a positive priming effect, as a consequence, caused a negative net soil C balance (-59 to -132 μg C g soil) regardless of microplastic types. K-strategists dominated in the PHBV-contaminated soils and induced 72 % higher positive priming effects as compared to Polyethylene-contaminated soils (160 vs. 92 μg C g soil). This was attributed to the enhanced decomposition of recalcitrant SOM to acquire nitrogen. The stronger priming effect associated in PHBVs can be attributed to cooperative decomposition among fungi and bacteria, which metabolize more recalcitrant C in PHBV. Moreover, comparatively higher calorespirometric ratios, lower substrate use efficiency, and larger enzyme activity but shorter turnover time of enzymes indicated that soil contaminated with PHBV release more energy, and have a more efficient microbial catabolism and are more efficient in SOM decomposition and nutrient resource uptake. Overall, microplastics, (especially bio-degradable microplastics) can alter biogeochemical cycles with significant negative consequences for C sequestration via increasing SOM decomposition in agricultural soils and for regional and global C budgets.
引发效应，即新鲜有机碳（C）输入后土壤有机质（SOM）分解的变化，已知会影响陆地生态系统的 C 储存。由于塑料的使用不断增加且通常在使用寿命结束时管理不善，因此微塑料（粒径<5mm）在土壤中无处不在。传统的聚乙烯和可生物降解（PHBV）塑料在其分子结构中含有大量的 C，可以被微生物同化。然而，微塑料引发的潜在引发效应的程度和方向尚不清楚。因此，我们添加了 C 标记的葡萄糖，以研究背景聚乙烯和 PHBV 微塑料（1%，w/w）在短期内在多大程度上影响 SOM 分解及其潜在的微生物机制。在 60 天的培养后，污染 PHBV 的土壤中累积的 CO 排放量比污染聚乙烯的土壤高 42-53%。添加葡萄糖增加了 SOM 的分解，并引发了正引发效应，从而导致了负的净土壤 C 平衡（-59 至-132μg C g 土壤），而与微塑料类型无关。在 PHBV 污染的土壤中，K 策略者占主导地位，与聚乙烯污染的土壤相比，正引发效应高 72%（160 对 92μg C g 土壤）。这归因于为获取氮而增强了对难分解 SOM 的分解。与聚乙烯相比，PHBV 中更强的引发效应可归因于真菌和细菌之间的协同分解，它们代谢 PHBV 中更多的难分解 C。此外，相对较高的热呼吸比、较低的底物利用效率、较大的酶活性和较短的酶周转时间表明，污染 PHBV 的土壤释放出更多的能量，具有更高效率的微生物分解代谢，并且在 SOM 分解和养分资源吸收方面效率更高。总体而言，微塑料（尤其是可生物降解的微塑料）可以通过增加农业土壤中 SOM 的分解来改变生物地球化学循环，从而对 C 封存产生重大的负面影响，并且对区域和全球的 C 预算产生重大的负面影响。
