实验室规模模拟含水层条件下的反硝化和同位素分馏效应

IF 4.4 3区环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES

Journal of contaminant hydrology Pub Date : 2025-10-06 DOI:10.1016/j.jconhyd.2025.104749

Qifang Chen , Yuemin Hu , Fan Chen , Junfeng Zhang , Zanfang Jin , Linyun Xiao , Xiang Chen , Yasheng Shi , Feili Li

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引用次数: 0

摘要

反硝化作用在控制地下水中硝酸盐（NO3−）的去向中起着关键作用。反硝化过程中氮同位素富集因子（εN）是量化反硝化对地下水硝酸盐还原作用的重要指标。建立了含地下水和沉积物的实验柱来模拟含水层条件。在溶解氧（DO）浓度分别为1和2 mg·L−1的条件下，以乙醇、乙酸盐、葡萄糖和红糖为电子供体，采用实验柱测量了地下水和沉积物中NO3−的反硝化速率和N、O同位素分馏效应。上覆地下水（εNo和εOo）和沉积物孔隙水（εNp和εOp）的反硝化速率和稳定同位素富集因子随碳源和DO浓度的不同而发生显著变化。在DO =2 mg·L−1时，乙酸（εNo,−9.2‰，εNp,−7.4‰）、葡萄糖（εNo,−7.4‰，εNp,−4.3‰）、红糖（εNo,−2.6‰，εNp,−2.4‰）的负同位素富集因子小于乙醇（εNo,−11.7‰，εNp,−10.0‰）。对于红糖，当DO =1时（εNo,−5.0‰；εNp,−3.5‰），负同位素富集因子多于DO = 2 mg·L−1时。反硝化速率越高，εNo和εNp值越负，反映出氮分馏越强。由于o交换分数和NO3−还原过程，在反硝化柱上εOo和εOp值均为正，εOo值在5.0‰~ 29.2‰之间，εOp值在3.9‰~ 22.8‰之间。NO3−扩散输运导致εNo （εOo）绝对值高于εNp （εOp）绝对值。计算得到的同位素富集因子（εNo和εNp）可用于量化原位条件下碳源的反硝化作用。

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$Denitrification and isotope fractionation effects under simulated aquifer conditions at a laboratory scale$

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Denitrification and isotope fractionation effects under simulated aquifer conditions at a laboratory scale

Denitrification plays a critical role in controlling the fate of nitrate (NO₃⁻) in groundwater. The nitrogen isotope enrichment factor (εN) during denitrification is essential for quantifying the role of denitrification in nitrate reduction in groundwater. Experimental columns containing groundwater and sediment were established to simulate aquifer conditions. Denitrification rates and the N and O isotope fractionation effects of NO₃⁻ in both groundwater and sediment during dentrification were measured in experimental columns using four organic substances as electron donors (ethanol, acetate, glucose and brown sugar) under two different dissolved oxygen (DO) concentrations of 1 and 2 mg·L⁻¹, respectively. Significant variations in denitrification rates and stable isotope enrichment factors were observed in both overlying groundwater (εN_o and εO_o) and sediment pore water (εN_p and εO_p), depending on the carbon source and DO concentration. At DO =2 mg·L⁻¹, acetate (εN_o, −9.2 ‰; εN_p, −7.4 ‰), glucose (εN_o, −7.4 ‰; εN_p, −4.3 ‰), brown sugar (εN_o, −2.6 ‰; εN_p, −2.4 ‰) exhibited less negative isotope enrichment factors compared to ethanol (εN_o, −11.7 ‰; εN_p, −10.0 ‰). For brown sugar, more negative isotope enrichment factors was observed at DO =1 (εN_o, −5.0 ‰; εN_p, −3.5 ‰) than at DO = 2 mg·L⁻¹. Higher denitrification rates correlated with more negative εN_o and εN_p values, reflecting stronger nitrogen fractionation. Due to the O-exchange fraction and NO₃⁻ reduction processes, positive εO_o and εO_p values were observed in the denitrification columns, ranging from 5.0 ‰ to 29.2 ‰ for εO_o and from 3.9 ‰ to 22.8 ‰ for εO_p. Fractionation by diffusive transport of NO₃⁻ resulted in higher absolute values of εN_o (εO_o) compared to those of εN_p (εO_p). The calculated isotope enrichment factors (εN_o and εN_p) may be applied to quantify denitrification linked to C sources application under in situ conditions.

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来源期刊

Journal of contaminant hydrology 环境科学-地球科学综合

CiteScore

6.80

自引率

2.80%

发文量

129

审稿时长

68 days

期刊介绍： The Journal of Contaminant Hydrology is an international journal publishing scientific articles pertaining to the contamination of subsurface water resources. Emphasis is placed on investigations of the physical, chemical, and biological processes influencing the behavior and fate of organic and inorganic contaminants in the unsaturated (vadose) and saturated (groundwater) zones, as well as at groundwater-surface water interfaces. The ecological impacts of contaminants transported both from and to aquifers are of interest. Articles on contamination of surface water only, without a link to groundwater, are out of the scope. Broad latitude is allowed in identifying contaminants of interest, and include legacy and emerging pollutants, nutrients, nanoparticles, pathogenic microorganisms (e.g., bacteria, viruses, protozoa), microplastics, and various constituents associated with energy production (e.g., methane, carbon dioxide, hydrogen sulfide). The journal''s scope embraces a wide range of topics including: experimental investigations of contaminant sorption, diffusion, transformation, volatilization and transport in the surface and subsurface; characterization of soil and aquifer properties only as they influence contaminant behavior; development and testing of mathematical models of contaminant behaviour; innovative techniques for restoration of contaminated sites; development of new tools or techniques for monitoring the extent of soil and groundwater contamination; transformation of contaminants in the hyporheic zone; effects of contaminants traversing the hyporheic zone on surface water and groundwater ecosystems; subsurface carbon sequestration and/or turnover; and migration of fluids associated with energy production into groundwater.