Considerable carbon dioxide emissions from groundwater over-exploitation in the North China Plain

This study compiled hydrogeochemical data from 6202 groundwater sampling sites across the North China Plain (NCP), being sampled between 2007 and 2010. This dataset comprises 4454 points in shallow aquifer and 1748 points in deep aquifer, which were used for the analysis of the quantitative calculation of CO2 emissions induced by groundwater over-exploitation in the NCP. These datasets revealed elevated HCO3- concentrations in the groundwater within the study area. Coupled with severe local over-exploitation, these have resulted in CO2 emissions from groundwater depletion and groundwater extraction reaching 0.53 Tg/yr and 4.03 Tg/yr, respectively. These values accounted for around 9% and 39% of the total CO2 emissions from terrestrial waters in the NCP, far exceeding the average proportion of groundwater CO2 emissions to total terrestrial water CO2 emission in China (<1%) and globally (∼1%). Additionally, shallow aquifers were found to emit significantly more CO2 than deep aquifers, contributing about 83% of the total emissions.本研究整理了2007年至2010年间采集的华北平原（North China Plain, NCP）6202个地下水采样点的水文地球化学数据。本数据集包含浅层含水层采样点4454个、深层含水层采样点1748个，用于华北平原地下水超采引发的二氧化碳排放量定量计算分析。该数据集揭示了研究区地下水中HCO3-浓度显著升高的特征。结合当地严重的地下水超采现状，上述特征导致地下水疏干与抽水过程产生的二氧化碳排放量分别达到0.53太克每年（Tg/yr）与4.03太克每年（Tg/yr）。上述排放量分别占华北平原陆地水域总二氧化碳排放量的约9%与39%，远高于中国全国陆地水域二氧化碳排放中地下水占比（<1%）以及全球平均占比（约1%）。此外，研究发现浅层含水层的二氧化碳排放量显著高于深层含水层，贡献了总排放量的约83%。