摘要
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。
Groundwater is an important water source in karst areas and a significant medium for storing atmospheric carbon dioxide.Dams built at the underground river outlets in karst regions benefit agricultural irrigation and the assurance of drinking water,but limited research has analyzed how carbon emission fluxes in the water body change after such human interventions.To investigate the characteristics and controlling factors of water carbon emission fluxes in the context of dam construction at underground river outlets in karst areas across diurnal and spatial scales,a study was conducted on the water continuum of the Longdongtang underground river outlet retention area-reservoir-drainage channel in the Longtan karst valley of the Wuling Mountain region in southwestern China.Water temperature,dissolved oxygen,pH,Ca^(2+),and HCO_(3)^(-) were monitored every 1 hour during the day and night,andδ^(13)C_(DIC) was monitored every 2 hours during the day and night(from October 14 to 15,2023).The CO_(2) flux at the water-air interface(FCO_(2))and net ecosystem productivity(NEP)were calculated and compared.The results show that FCO_(2) exhibits a characteristic of being low during the daytime and high at nighttime.During the day,FCO_(2) accounts for 46.4%-48.8%of the total FCO_(2),while at night,it accounts for 51.2%-53.6%.The diurnal variation reached a maximum of 22.21×103 g C/(d·m^(2)).FCO_(2) displayed significant spatial differences,with specific values of FCO_(2) being lowest at the underground river outlet retention area[0.61 g C/(d·m^(2))],higher in the reservoir karst pool[0.75 g C/(d·m^(2))],and highest at the main drainage channel[0.81 g C/(d·m^(2))].The study found that changes in biological metabolic processes and water flow patterns were the main factors controlling the diurnal and spatial variations in FCO_(2) at the karst underground river dam,with biological metabolism having the most significant impact.The diurnal variation of NEP was opposite to that of FCO_(2),and its spatial variation showed an increasing trend from the dam inlet to the dam outlet:0.34 g C/(d·m^(2))at the underground river outlet retention area,0.31 g C/(d·m^(2))in the reservoir karst pool,and 0.26 g C/(d·m^(2))at the main drainage channel This indicates that spatial differences in biological metabolism may shape the increasing trend of FCO_(2) along the flow path.The results of this study show that dam construction at the underground river outlet altered the hydraulic conditions,creating a favorable environment for aquatic plant growth.This,in turn,promoted the biological carbon pump effect while reducing CO_(2) flux emissions to the atmosphere.This finding provides new insights for future management of carbon emissions in water bodies in karst areas.
作者
唐越尔
曾思博
杨琰
刘旭阳
胡晨鹏
黄信何
TANG Yueer;ZENG Sibo;YANG Yan;LIU Xuyang;HU Chenpeng;HUANG Xinhe(Chongqing Key Laboratory of Karst Environment&School of Geographical Sciences,Southwest University,Chongqing 400715,China;Chongqing Jinfo Mountain Karst Ecosystem National Observation and Research Station,Chongqing 400715,China)
出处
《地球与环境》
北大核心
2025年第6期800-814,共15页
Earth and Environment
基金
国家自然科学基金项目(42277048、U2244216、42307070)
国家重点研发计划子课题(2016YFC050230205)。
关键词
岩溶地下河
筑坝
生物泵
水体碳通量
地表水
karst underground river
dam construction
biological pump
water carbon flux
surface water
