地下水是岩溶区重要的水源,也是存储大气二氧化碳的重要介质,在岩溶区地下河出口筑坝可以有效保证农业灌溉和居民生活用水,但目前对于这种人为干预后水体碳排放通量变化的研究仍然匮乏。为探究岩溶地下河出口筑坝环境下水体碳排放通量...地下水是岩溶区重要的水源,也是存储大气二氧化碳的重要介质,在岩溶区地下河出口筑坝可以有效保证农业灌溉和居民生活用水,但目前对于这种人为干预后水体碳排放通量变化的研究仍然匮乏。为探究岩溶地下河出口筑坝环境下水体碳排放通量的昼夜时空特征及其控制因素,以我国西南武陵山区龙潭岩溶槽谷龙洞塘地下河出口的拦水区-蓄水池-排水渠道连续体为研究对象,于2023年10月14日至15日,对水温、溶解氧、pH、Ca^(2+)和HCO_(3)^(-)进行了1 h/次的昼夜连续监测,同时对δ^(13)C_(DIC)进行了2 h/次的昼夜监测。计算了水文连续体水-气界面CO_(2)交换通量(FCO_(2))和净生态系统生产力(NEP)并进行了对比。结果表明:在昼夜上,FCO_(2)呈现白天低夜晚高的特征,白天FCO_(2)占总FCO_(2)的46.4%~48.8%,夜晚FCO_(2)占总FCO_(2)的51.2%~53.6%,昼夜变幅最大达22.21×10^(-3) g C/(d·m^(2))。FCO_(2)表现出了显著的空间差异,FCO_(2)具体表现为地下河出口拦水区<蓄水溶潭池<排水主渠道,分别为0.61、0.75和0.81 g C/(d·m^(2))。研究发现生物代谢过程和水体流动方式的改变是控制岩溶地下河筑坝水体FCO_(2)昼夜及空间变化的主要因素,其中生物代谢的影响最为显著。NEP的昼夜变化与FCO_(2)相反,空间变化表现为地下河出口拦水区>蓄水溶潭池>排水主渠道,分别为0.34、0.31和0.26 g C/(d·m^(2)),这说明生物代谢的空间差异可能塑造了FCO_(2)沿流程增加的特征。本研究结果表明,地下河出口筑坝工程改变了水力条件,为水生植物的生长提供有利环境,在促进了生物碳泵效应的同时削减了排放至大气的CO_(2)通量。该发现将为未来岩溶区水体碳排放的干预管理提供新思路。展开更多
The stability of coal pillar dams is crucial for the long-term service of underground reservoirs storing water or heat.Chemi-cal damage of coal dams induced by ions-atttacking in coal is one of the main reasons for th...The stability of coal pillar dams is crucial for the long-term service of underground reservoirs storing water or heat.Chemi-cal damage of coal dams induced by ions-atttacking in coal is one of the main reasons for the premature failure of coal dams.However,the diffusion process of harmful ions in coal is far from clear,limiting the reliability and durability of coal dam designs.This paper investigates sulfate diffusion in coal pillar through experimental and analytical methods.Coal specimens are prepared and exposed to sulfate solutions with different concentrations.The sulfate concentrations at different locations and time are measured.Based on experimental data and Fick's law,the time-dependent surface concentration of sulfate and diffusion coefficient are determined and formulated.Further,an analytical model for predicting sulfate diffusion in coal pillar is developed by considering dual time-dependent characteristics and Laplace transformations.Through comparisons with experimental data,the accuracy of the analytical model for predicting sulfate diffusion is verified.Further,sulfate diffusions in coal dams for different concentrations of sulfate in mine water are investigated.It has been found that the sulfate concen-tration of exposure surface and diffusion coefficient in coal are both time-dependent and increase with time.Conventional Fick's law is not able to predict the sulfate diffusion in coal pillar due to the dual time-dependent characteristics.The sulfate attacking makes the coal dam a typical heterogeneous gradient structure.For sulfate concentrations 0.01-0.20 mol/L in mine water,it takes almost 1.5 and 4 years for sulfate ions to diffuse 9.46 and 18.92 m,respectively.The experimental data and developed model provide a practical method for predicting sulfate diffusion in coal pillar,which helps the service life design of coal dams.展开更多
文摘地下水是岩溶区重要的水源,也是存储大气二氧化碳的重要介质,在岩溶区地下河出口筑坝可以有效保证农业灌溉和居民生活用水,但目前对于这种人为干预后水体碳排放通量变化的研究仍然匮乏。为探究岩溶地下河出口筑坝环境下水体碳排放通量的昼夜时空特征及其控制因素,以我国西南武陵山区龙潭岩溶槽谷龙洞塘地下河出口的拦水区-蓄水池-排水渠道连续体为研究对象,于2023年10月14日至15日,对水温、溶解氧、pH、Ca^(2+)和HCO_(3)^(-)进行了1 h/次的昼夜连续监测,同时对δ^(13)C_(DIC)进行了2 h/次的昼夜监测。计算了水文连续体水-气界面CO_(2)交换通量(FCO_(2))和净生态系统生产力(NEP)并进行了对比。结果表明:在昼夜上,FCO_(2)呈现白天低夜晚高的特征,白天FCO_(2)占总FCO_(2)的46.4%~48.8%,夜晚FCO_(2)占总FCO_(2)的51.2%~53.6%,昼夜变幅最大达22.21×10^(-3) g C/(d·m^(2))。FCO_(2)表现出了显著的空间差异,FCO_(2)具体表现为地下河出口拦水区<蓄水溶潭池<排水主渠道,分别为0.61、0.75和0.81 g C/(d·m^(2))。研究发现生物代谢过程和水体流动方式的改变是控制岩溶地下河筑坝水体FCO_(2)昼夜及空间变化的主要因素,其中生物代谢的影响最为显著。NEP的昼夜变化与FCO_(2)相反,空间变化表现为地下河出口拦水区>蓄水溶潭池>排水主渠道,分别为0.34、0.31和0.26 g C/(d·m^(2)),这说明生物代谢的空间差异可能塑造了FCO_(2)沿流程增加的特征。本研究结果表明,地下河出口筑坝工程改变了水力条件,为水生植物的生长提供有利环境,在促进了生物碳泵效应的同时削减了排放至大气的CO_(2)通量。该发现将为未来岩溶区水体碳排放的干预管理提供新思路。
基金supported by Hunan Provincial Education Department Funded Research Projects (Grant No.22C0221)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining (Grant No.GJNY-18-73.11).
文摘The stability of coal pillar dams is crucial for the long-term service of underground reservoirs storing water or heat.Chemi-cal damage of coal dams induced by ions-atttacking in coal is one of the main reasons for the premature failure of coal dams.However,the diffusion process of harmful ions in coal is far from clear,limiting the reliability and durability of coal dam designs.This paper investigates sulfate diffusion in coal pillar through experimental and analytical methods.Coal specimens are prepared and exposed to sulfate solutions with different concentrations.The sulfate concentrations at different locations and time are measured.Based on experimental data and Fick's law,the time-dependent surface concentration of sulfate and diffusion coefficient are determined and formulated.Further,an analytical model for predicting sulfate diffusion in coal pillar is developed by considering dual time-dependent characteristics and Laplace transformations.Through comparisons with experimental data,the accuracy of the analytical model for predicting sulfate diffusion is verified.Further,sulfate diffusions in coal dams for different concentrations of sulfate in mine water are investigated.It has been found that the sulfate concen-tration of exposure surface and diffusion coefficient in coal are both time-dependent and increase with time.Conventional Fick's law is not able to predict the sulfate diffusion in coal pillar due to the dual time-dependent characteristics.The sulfate attacking makes the coal dam a typical heterogeneous gradient structure.For sulfate concentrations 0.01-0.20 mol/L in mine water,it takes almost 1.5 and 4 years for sulfate ions to diffuse 9.46 and 18.92 m,respectively.The experimental data and developed model provide a practical method for predicting sulfate diffusion in coal pillar,which helps the service life design of coal dams.
