河口区溶解性有机质特征及其对温室气体排放的影响:以灌河、淮河入海水道为例OA北大核心CSCDCSTPCD

As a key interface of carbon exchange between land and sea,the composition of dissolved organic matter(DOM)in estuaries significantly influences the generation and emission of greenhouse gases(GHGs).In this study,the Guanhe River and Huaihe River estuaries in Jiangsu Province were investigated using three-dimensional excita-tion-emission matrix fluorescence spectroscopy,parallel factor analysis,and in situ flux monitoring to examine the land-sea co-migration patterns of DOM and their driving mechanisms for CO2,CH4,and N2O emissions.The re-sults indicated several key findings.(1)DOM in both estuaries consisted of humic-like components(C1 and C3)and protein-like components(C2),with spatial differentiation primarily controlled by land-based inputs(industrial and agricultural wastewater).DOM in the Guanhe River was dominated by industrial protein(C2,45.6%),whereas DOM in the Huaihe River was dominated by agricultural humic matter(C1+C3,57.8%).(2)Greenhouse gas flux-es decreased from the river channel to the nearshore.During the normal water period,the fluxes of CO2,CH4,and N2O were 14.15±27.32,45.71±92.33,and 11.46±36.91 μmol·m‒2·d‒1,respectively,which were significantly higher than those in the wet season(P<0.05).(3)DOM molecular properties regulated GHG emissions through microbial metabolism and photochemical pathways.Humic-like substances(C1 and C3)promoted CO2 and N2O production(R2=0.67),whereas protein-like substances(C2)indirectly drove CH4 release through co-metabolism.(4)The distribution of GHG fluxes and DOM in riverine areas was mainly controlled by phytoplankton activity(Chlorophyll a)and nitrogen and phosphorus inputs,whereas in coastal waters it was dominated by salinity gradi-ents and nitrogen transformation processes(nitrification/denitrification).This study reveals the mechanisms gov-erning the carbon fate of estuarine DOM under high-intensity human activities and provides theoretical support for enhancing"blue carbon"sinks and advancing low-carbon management in estuarine areas.