Characteristics and algal source effects of dissolved organic matter in small and medium-sized gate-controlled seagoing rivers in South China
Due to the influence of climate change and human activities,algal blooms frequent occurrences in rivers in South China.Evaluating the concentration,sources and composition of dissolved organic matter(DOM)is of great significance for regional carbon cycle.In this study,we focused on three typical small and medium-sized gate-controlled rivers(Huangjiang River,Dongxi River and Lianjiang River)in South China.From January to December of 2022,the DOM characteristics in these rivers were continuously monitored to investigate the spatial-temporal distribution of DOM concentrations,sources,and the effects of algal blooms.The results show that DOC accounted for 78.6％,81.3％,and 67.2％of the total organic carbon(TOC)in Huangjiang River,Dongxi River,and Lianjiang River,respectively,being the dominant form of organic carbon.The annual average DOC concentrations in these three rivers were 2.6mg/L,4.3mg/L,and 5.1mg/L,respectively,which were lower than the average concentration in all world rivers but higher than those in the large rivers in South China.The DOM in the three rivers exhibited characteristics of both terrestrial and endogenous sources,with a more pronounced contribution from endogenous sources.And the algal-derived DOC concentrations in Huangjiang River,Dongxi River,and Lianjiang River were determined to be 1.2mg/L,1.8mg/L,and 2.2mg/L,or proportionally accounted for 49.6％,42.6％,and 48.0％,respectively,further indicating that algal blooms were the main contributors to DOM in the three rivers.Fluorescence excitation-emission matrix-parallel factor analysis(EEM-PARAFAC)of DOM in the three rivers revealed three types of protein components and two types of humic substances.Among them,the fluorescence intensity of endogenous protein components C1 and C3 in the dry season was significantly higher than that in the wet season under the influence of algal blooms.The fluorescence intensity of humic substance components C2 and C4,originating from terrigenous humus,showed a pattern of Lianjiang River＞Dongxi River＞Huangjiang River.Consequently,the massive proliferation of algal was one of the major reasons why the DOC concentration was higher in these three rivers than in larger rivers in South China,and the protein-like components C1 and C3were significantly higher in the dry season than those in the wet season.Exogenous inputs and river physical and chemical parameters,including rainfall,temperature,salinity,nutrient concentrations,and anthropogenic interference(e.g.,gate control schedules),jointly influenced the concentrations and compositions of DOM in these rivers.
万方数据
维普
