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Inner Mongolia University (2022)

Study on Carbon Emissions and the Influencing Factors in An Eutrophic Saline Lake of Semi-arid Region

李向伟

Titre : Study on Carbon Emissions and the Influencing Factors in An Eutrophic Saline Lake of Semi-arid Region

Auteur : 李向伟

Grade : Master 2022

Université : Inner Mongolia University

Résumé
Lakes are important sites for greenhouse gas production and emission,and play an important role in the global carbon cycle.In this paper,the eutrophic saline lake Daihai Lake in the semi-arid region was selected as the study area,and the sampling was conducted in January,April,July and October of 2020.We selected the floating chamber method,headspace equilibrium method and Fick’s first law to measure the carbon emission dynamics at the water-air interface,sediment-water interface and the changes of greenhouse gas concentrations in the water column and porewater.Then we also elucidated the effects of environmental factors and water quality factors on carbon emissions,the main results are as follows :(1)The mean values of CO2 partial pressure and CH4 partial pressure at the water-air interface(pW-ACO2 ;pW-ACH4)in Daihai Lake were 558.23±117.16μatm and 18.60±14.95μatm,respectively.The temporal variation trend of pW-ACO2 and pW-ACH4 were:July>October>May>January.On the spatial scale,pW-ACO2 and pW-ACH4fluctuated was not significant.The main influencing factors of pW-ACO2 were WT(R 2=0.30,P<0.01),WS(R 2=0.38,P<0.01),NO2—N(R 2=0.45,P<0.01)and TN(R 2=0.25,P<0.01) ;the main influencing factors of pW-ACH4 were WT(R 2=0.60,P<0.01)and TN(R 2=0.12,P<0.01).(2)The mean values of CO2 flux and CH4 flux at the water-air interface(FW-ACO2 ;FW-ACH4)in Daihai Lake were 16.77±13.77 mmol m-2 d-1 and 0.57±0.87 mmol m-2 d-1,respectively.and the lake was generally the source of CO2 and CH4.On the temporal scale,FW-ACO2 was significantly higher in July and October and the mean FW-ACH4 was highest in July ;on the spatial scale,the variation of FW-ACO2 and FW-ACH4 was not significant.The main influencing factor for FW-ACO2 was NO2—N(R 2=0.29,P<0.01)and for FW-ACH4 was DOC(R 2=0.20,P<0.05).(3)The mean values of CO2 concentration in porewater and water column were144.98±117.99μmol L-1 and 7.46±1.42μmol L-1,respectively,and the CH4concentrations in porewater and water column were 124.36±97.00μmol L-1 and0.22±0.16μmol L-1,respectively.The temporal variation trend of CO2 concentration in porewater was:July>October>May>January,and the CH4 concentration in porewater was the lowest in January.Overall the spatial variation of both CO2 and CH4 concentrations in porewater was not significant.The main influencing factor for CO2 concentration in porewater were Sal(R 2=0.17,P<0.01)and TN(R 2=0.06,P<0.01)and for CH4 concentration in poterwater was Sal(R 2=0.08,P<0.01).(4)The mean values of CO2 flux and CH4 flux at the sediment-water interface(FS-WCO2 ;FS-WCH4)in Daihai Lake were 9.24±13.84μmol m-2 d-1 and 3.53±4.36μmol m-2 d-1,respectively.On the time scale,the mean FS-WCO2 in July and October was higher than that in January and May,and FS-WCH4 was significantly higher in July than in the other sampling periods ;on the spatial scale,the variation of FS-WCO2and FS-WCH4was not significant.The main influencing factors of FS-WCO2 were sediment porosity(R 2=0.29,P<0.01)and CO2 concentration in porewater(R 2=0.57,P<0.01) ;the main influencing factors of FS-WCH4 were sediment porosity(R 2=0.07,P<0.05)and CH4 concentration in porewater(R 2=0.58,P<0.01)

Mots clés : carbon partial pressure ;carbon flux ;water-air interface ;sediment-water interface ;eutrophication;saline lake ;

Présentation (CNKI)

Page publiée le 21 octobre 2022