Shu Wang, Zhang Qiuying, Audet Joachim, Li Zhao, Leng Peifang, Qiao Yunfeng, Tian Chao, Chen Gang, Zhao Jun, Cheng Hefa, Li Fadong
Shandong Yucheng Agro-Ecosystem National Observation and Research Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Sino-Danish College of University of Chinese Academy of Sciences, Beijing 101408, China; Sino-Danish Centre for Education and Research, Beijing 101408, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Water Res. 2024 Mar 1;251:121124. doi: 10.1016/j.watres.2024.121124. Epub 2024 Jan 9.
Rare earth mining causes severe riverine nitrogen pollution, but its effect on nitrous oxide (NO) emissions and the associated nitrogen transformation processes remain unclear. Here, we characterized NO fluxes from China's largest ion-adsorption rare earth mining watershed and elucidated the mechanisms that drove NO production and consumption using advanced isotope mapping and molecular biology techniques. Compared to the undisturbed river, the mining-affected river exhibited higher NO fluxes (7.96 ± 10.18 mmol md vs. 2.88 ± 8.27 mmol md, P = 0.002), confirming that mining-affected rivers are NO emission hotspots. Flux variations scaled with high nitrogen supply (resulting from mining activities), and were mainly attributed to changes in water chemistry (i.e., pH, and metal concentrations), sediment property (i.e., particle size), and hydrogeomorphic factors (e.g., river order and slope). Coupled nitrification-denitrification and NO reduction were the dominant processes controlling the NO dynamics. Of these, the contribution of incomplete denitrification to NO production was greater than that of nitrification, especially in the heavily mining-affected reaches. Co-occurrence network analysis identified Thiomonas and Rhodanobacter as the key genus closely associated with NO production, suggesting their potential roles for denitrification. This is the first study to elucidate NO emission and influential mechanisms in mining-affected rivers using combined isotopic and molecular techniques. The discovery of this study enhances our understanding of the distinctive processes driving NO production and consumption in highly anthropogenically disturbed aquatic systems, and also provides the foundation for accurate assessment of NO emissions from mining-affected rivers on regional and global scales.
稀土开采导致严重的河流氮污染，但其对一氧化二氮（N₂O）排放及相关氮转化过程的影响仍不明确。在此，我们对中国最大的离子吸附型稀土开采流域的N₂O通量进行了表征，并运用先进的同位素图谱和分子生物学技术阐明了驱动N₂O产生和消耗的机制。与未受干扰的河流相比，受开采影响的河流表现出更高的N₂O通量（7.96 ± 10.18 mmol m⁻² d⁻¹ 对比 2.88 ± 8.27 mmol m⁻² d⁻¹，P = 0.002），证实受开采影响的河流是N₂O排放热点。通量变化与高氮供应（由采矿活动导致）相关，主要归因于水化学性质（即pH值和金属浓度）、沉积物性质（即粒径）以及水文地貌因素（如河流等级和坡度）的变化。耦合硝化 - 反硝化作用和N₂O还原是控制N₂O动态的主要过程。其中，不完全反硝化对N₂O产生的贡献大于硝化作用，特别是在受采矿影响严重的河段。共现网络分析确定硫单胞菌属和红杆菌属是与N₂O产生密切相关的关键属，表明它们在反硝化作用中的潜在作用。这是首次使用同位素和分子技术相结合的方法阐明受采矿影响河流中N₂O排放及其影响机制的研究。本研究的发现增进了我们对高度人为干扰的水生系统中驱动N₂O产生和消耗的独特过程的理解，也为在区域和全球尺度上准确评估受采矿影响河流的N₂O排放提供了基础。
