The release of nutrients into water during debris decomposition is a serious concern, leading to severe environmental pollution. To understand the effects of extensively present emerging contaminants (such as perfluoroalkyl acids (PFAAs)) on the nitrogen (N) release and transformation, the concentration dynamics of different N species in surrounding water and changes in microbial communities on biofilm during the 70-days decomposition of two typical submerged macrophyte (Alisma orientale and Iris pseudacorus) debris were studied. The results showed that large amounts of N species (especially organic and ammonium N) were released during decomposition. PFAAs with a low concentration (1 μg/L) could stimulate total N (TN) release, whereas PFAAs with a high concentration (≥ 10 μg/L) might have inhibited TN release. Higher intensities of ammonification, nitrosification, and denitrification, but lower intensities of nitrification were observed in water in the presence of PFAAs. Microbiota associated with organic matter hydrolysis, nitrification and denitrification, as well as PFAA degrading/tolerant bacteria, were beneficial and might have occupied dominant states. Redundancy analysis showed that PFAAs were positively associated with the amounts of nitrate, denitrifiers, and azotobacteria but negatively correlated with the TN, ammonia, nitrite, organic N, and nitrosobacteria amounts (p = 0.0002). The complete N metabolism pathway was identified using PICRUSt and KEGG. Functional genes related to ammonification (0.76‰–2.16‰), N reduction (3.43‰–5.05‰), and assimilation (0.81‰–2.16‰) were more abundant than others in all treatments. This study provides a more comprehensive understanding of N cycling during debris decomposition under the increasingly intractable threat of emerging contaminants in aquatic ecosystems.

中文翻译：

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全氟烷基酸对东方菖蒲和黄鸢尾碎片分解过程中氮释放、转化和微生物群落的影响


碎屑分解过程中营养物质释放到水中是一个严重的问题，导致严重的环境污染。为了解广泛存在的新兴污染物（如全氟烷基酸 （PFAA））对氮 （N） 释放和转化的影响，研究了两种典型的淹没大植物（Alisma orientale 和 Iris pseudacorus）碎片在 70 d 分解过程中周围水中不同 N 物种的浓度动态和生物膜上微生物群落的变化。结果表明，在分解过程中释放了大量的 N 物种（尤其是有机氮和铵态氮）。低浓度 （1 μg/L） 的 PFAA 可刺激总 N （TN） 的释放，而高浓度 （≥ 10 μg/L） 的 PFAA 可能抑制 TN 的释放。在 PFAA 存在的情况下，在水中观察到较高的氨化、亚硝化和反硝化强度，但硝化强度较低。与有机物水解、硝化和反氮化相关的微生物群，以及 PFAA 降解/耐受细菌，是有益的，并且可能占据了主导地位。冗余分析表明，PFAA 与硝酸盐、反氮化剂和固氮菌的含量呈正相关，但与 TN、氨、亚硝酸盐、有机氮和亚硝化细菌的含量呈负相关 （p = 0.0002）。使用 PICRUSt 和 KEGG 鉴定完整的 N 代谢途径。在所有处理中，与氨化 （0.76‰–2.16‰）、氮还原 （3.43‰–5.05‰） 和同化 （0.81‰–2.16‰） 相关的功能基因都比其他基因更丰富。 本研究为在水生生态系统中日益棘手的新兴污染物威胁下碎片分解过程中的氮循环提供了更全面的理解。