城镇化影响东江流域活性氮周转演变的同位素证据

温婧; 黄邦杰; 房怀阳; 谭秀琴; 吴称龙; 黄志伟; 张宗尧; 林澍; 杜宏伟

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中国环境科学 ›› 2025, Vol. 45 ›› Issue (5) : 2757-2766.

环境生态

城镇化影响东江流域活性氮周转演变的同位素证据

温婧, 黄邦杰, 房怀阳, 谭秀琴, 吴称龙, 黄志伟, 张宗尧, 林澍, 杜宏伟

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Isotopic evidence for impacts of urbanization on active nitrogen turnover in the Dongjiang River Basin

WEN Jing, HUANG Bang-jie, FANG Huai-yang, TAN Xiu-qin, WU Chen-long, HUANG Zhi-wei, ZHANG Zong-yao, LIN Shu, DU Hong-wei

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摘要

选择东江流域为研究区,对比不同下垫面影响下河流不同形态氮浓度和氮同位素,探究城镇化发展对流域氮周转的影响并提供实测证据.结果发现,相比其他下垫面影响下的河流,东江流域城镇化河流氮浓度和同位素值呈现不同特征.首先,城镇河流氮浓度高,并且氮以硝酸盐氮为主;其次,同位素分馏效应和瑞利分馏模型估算表明,城镇化发展增强了河道内硝化能力,并且平均约25.8%的硝酸盐氮来自河道内硝化周转;此外城镇河流记录了ln (NO₃^--N)与δ¹⁵N-NO₃^-之间的正相关关系,且枯、丰水期Δδ¹⁵N与Δδ¹⁸O的比值为-2和-6,表明城镇化河流反硝化能力弱,这为抵抗反硝化作用造成硝酸盐积累的现象提供了同位素证据;同时城镇化河流中δ¹⁵N-PN与δ¹⁵N-NH₄⁺的相关性较弱,以及硝酸盐氮同化作用中¹⁵N富集因子与理论值存在差异,证明同化吸收氨氮和硝酸盐氮的作用也不显著.最后,城镇化造成河流活性氮输入途径增多、氮汇过程减少,成为东江流域下游氮浓度升高的关键机制.

Abstract

The Dongjiang River Basin was chosen as the study area to compare the nitrogen concentrations and isotopes in the river with different land uses, so as to provide a better understanding and evidence for impacts of urbanization on active nitrogen turnover. In this study, the distinct characteristics of nitrogen concentrations and isotopes were found in urbanized rivers compared to rivers with other land uses. Firstly, the nitrogen concentrations in urbanized rivers were gradually increased due to urbanization and nitrate has become a main nitrogen speciation. Secondly, based on the isotope Rayleigh fractionation model, it was found that the nitrification potential in urbanized river channels was enhanced and about 25.8% of nitrate nitrogen came from nitrification in situ. In addition, a positive correlation between ln(NO₃^--N) and δ¹⁵N-NO₃^- was recorded in urbanized rivers. Moreover, Δδ¹⁵N/Δδ¹⁸O in the dry and wet seasons were –2 and -6, respectively, indicating that the denitrification potential was weakened to provide evidence for nitrate accumulation in urbanized river channels. Likewise, a weak correlation between δ¹⁵N-PN and δ¹⁵N-NH⁴⁺ was also recorded in urbanized rivers, and the ¹⁵N enrichment factor of nitrate assimilation also differed from the theoretical value, indicating a weak assimilation of ammonia and nitrate nitrogen. Finally, more input pathways and less sink processes of nitrogen in urbanized rivers have become a key mechanism for elevated riverine nitrogen concentrations in the lower reaches of Dongjiang river.

导出引用

温婧, 黄邦杰, 房怀阳, 谭秀琴, 吴称龙, 黄志伟, 张宗尧, 林澍, 杜宏伟. 城镇化影响东江流域活性氮周转演变的同位素证据[J]. 中国环境科学. 2025, 45(5): 2757-2766

WEN Jing, HUANG Bang-jie, FANG Huai-yang, TAN Xiu-qin, WU Chen-long, HUANG Zhi-wei, ZHANG Zong-yao, LIN Shu, DU Hong-wei. Isotopic evidence for impacts of urbanization on active nitrogen turnover in the Dongjiang River Basin[J]. China Environmental Science. 2025, 45(5): 2757-2766

中图分类号： X522

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