University of Liège, ArGEnCo, Hydrogeology and Environmental Geology, Aquapôle, Liège, Belgium.
Chemical Oceanography Unit, University of Liège, Liège, Belgium.
Sci Total Environ. 2018 Apr 1;619-620:1579-1588. doi: 10.1016/j.scitotenv.2017.10.144. Epub 2017 Nov 8.
This work aims to (1) identify the most conductive conditions for the generation of greenhouses gases (GHGs) in groundwater (e.g., hydrogeological contexts and geochemical processes) and (2) evaluate the indirect emissions of GHGs from groundwater at a regional scale in Wallonia (Belgium). To this end, nitrous oxide (NO), methane (CH) and carbon dioxide (CO) concentrations and the stable isotopes of nitrate (NO) and sulphate were monitored in 12 aquifers of the Walloon Region (Belgium). The concentrations of GHGs range from 0.05μg/L to 1631.2μg/L for NO, 0μg/L to 17.1μg/L for CH, and 1769 to 100,514ppm for the partial pressure of CO (pCO). The highest average concentrations of NO and pCO are found in a chalky aquifer. The coupled use of statistical techniques and stable isotopes is a useful approach to identify the geochemical conditions that control the occurrence of GHGs in the aquifers of the Walloon Region. The accumulation of NO is most likely due to nitrification (high concentrations of dissolved oxygen and NO and null concentrations of ammonium) and, to a lesser extent, initial denitrification in a few sampling locations (medium concentrations of dissolved oxygen and NO). The oxic character found in groundwater is not prone to the accumulation of CH in Walloon aquifers. Nevertheless, groundwater is oversaturated with GHGs with respect to atmospheric equilibrium (especially for NO and pCO); the fluxes of NO (0.32kgNO-NHay) and CO (27kgCOHay) from groundwater are much lower than the direct emissions of NO from agricultural soils and fossil-fuel-related CO emissions. Thus, indirect GHG emissions from the aquifers of the Walloon Region are likely to be a minor contributor to atmospheric GHG emissions, but their quantification would help to better constrain the nitrogen and carbon budgets.
(1) 确定地下水（如水文地质背景和地球化学过程）中温室气体（GHGs）产生的最具导电性条件；(2) 在比利时瓦隆大区（Wallonia）评估地下水的间接 GHG 排放。为此，监测了比利时瓦隆大区 12 个含水层中的一氧化二氮（NO）、甲烷（CH）和二氧化碳（CO）浓度以及硝酸盐（NO）和硫酸盐的稳定同位素。GHGs 的浓度范围为：NO 为 0.05μg/L 至 1631.2μg/L，CH 为 0μg/L 至 17.1μg/L，CO 的分压（pCO）为 1769 至 100,514ppm。NO 和 pCO 的最高平均浓度出现在白垩含水层中。统计技术和稳定同位素的结合使用是一种有用的方法，可以确定控制瓦隆大区含水层中 GHGs 发生的地球化学条件。NO 的积累最可能是由于硝化作用（溶解氧和 NO 浓度高，铵浓度为零），以及在少数采样点发生的初始反硝化作用（溶解氧和 NO 浓度中等）。在瓦隆含水层中发现的好氧特征不易积累 CH。尽管如此，地下水相对于大气平衡而言已经过饱和（特别是对 NO 和 pCO）；从地下水中排出的 NO（0.32kgNO-NHay）和 CO（27kgCOHay）通量远低于农业土壤直接排放的 NO 和与化石燃料相关的 CO 排放。因此，瓦隆大区含水层的间接 GHG 排放可能对大气 GHG 排放的贡献较小，但对其进行量化有助于更好地约束氮和碳预算。
