珠江口虎门淡水端溶解有机碳变化的机制——基于三端元混合模型的结果

The mechanism of the variation of DOC concentration in the freshwater end-member in Humen outlet of Pearl River Estuary——based on a three-component model analysis

采用高温燃烧法测定了夏季珠江口的溶解有机碳(dissolved organic carbon,DOC)浓度,结果表明,DOC浓度在夏季珠江口虎门上游不同来源的淡水水体间存在较大差异,广州段水体DOC浓度高达479μmol/L,在广州—虎门约70 km干流中DOC浓度呈快速降低趋势。东江三条支流在广州—虎门汇入干流中,东江各支流平均DOC浓度约为227μmol/L,东江DOC浓度相对较低水体的汇入稀释了干流中的DOC,再加上DOC的去除效应,至虎门时干流中DOC浓度只有139μmol/L,即干流中DOC下降的浓度为340μmol/L。建立三端元混合模型定量讨论去除效应和稀释效应各自的贡献,结果表明去除效应和稀释效应的贡献分别为228μmol/L(占比约67%)和112μmol/L(占比约33%),DOC浓度在珠江广州—虎门快速下降主要由去除效应造成,但东江对干流的稀释效应也不可忽略。

Dissolved organic carbon (DOC) concentrationin the Pearl River Estuary in summer was observed by high temperature combustion method ,the result showed that a great difference of the DOC concentration among the different sources freshwater bodies in the upper reaches of Humen outlet. While the highest DOC (479 μmol/L) was observed in Guangzhou section,it decreased drastically in a 70 km voyage from Guangzhou to Humen outlet. Three tributaries of the Dongjiang River flow into the main stream,bringing an average 227 μmol/L DOC concentration freshwater,the remittance of the relatively low DOC in Dongjiang River and the removal effect of DOC reduced the DOC in the main stream,DOC was only 139 μmol/L in Humen outlet,i.e.,the concentration of DOC decreased totally 340 μmol/ L in the main stream from Guangzhou to Humen outlet. A three-component model was used to discuss the respective contribution of removal and dilution effects,the running results showed that the removal and dilution effects were 228 μmol/L (accounting for 67%) and 112 μmol/L (accounting for 33%),respectively,the removal effect was the dominant process while the dilution effect can not be neglected.