基于水淘选分级的长江口最大浑浊带附近颗粒有机碳的来源、分布和保存  

Sources,distribution and preservation of size-fractionated particulate organic carbon in the turbidity maximum zone of the Changjiang Estuary based on water elutriation

作　　者：潘慧慧[1,2] 姚鹏[1,3,4] 赵彬[1,2] 孟佳[1,2] 李栋[1,2] 王金鹏[1,2] 

机构地区：[1]中国海洋大学海洋化学理论与工程技术教育部重点实验室,山东青岛266100 [2]中国海洋大学化学化工学院,山东青岛266100 [3]海洋科学与技术青岛协同创新中心,山东青岛266100 [4]中国海洋大学海洋有机地球化学研究所,山东青岛266100

出　　处：《海洋学报》2015年第4期1-15,共15页

基　　金：国家自然科学基金面上项目"不同来源有机碳在长江口-东海内陆架的水动力分选研究"(41176063);国家自然科学基金创新研究群体项目"海洋有机生物地球化学"(41221004);国家自然科学基金重大国际(地区)合作研究项目"长江口及邻近海域底边界层生物地球化学过程研究"(40920164004)

摘　　要：从分粒级的角度研究大河河口颗粒有机碳的输送特征是深刻理解河口淡咸水混合过程中有机碳的生物地球化学过程的关键。于2011年6月采集了长江口最大浑浊带附近盐度梯度下的表层悬浮颗粒物,采用水淘选方法对其按照水动力直径大小进行了分级分离,分析了这些颗粒物的有机碳含量、稳定碳同位素组成及颗粒物比表面积等参数,讨论了不同粒级颗粒物上有机碳的来源、分布和保存随盐度的变化特点及其影响因素。结果表明,随着盐度的增加和粒径的增大,长江口最大浑浊带附近分级颗粒有机碳逐渐降低,颗粒有机碳含量主要集中在小于32μm的粒级。相对于长江干流,长江口颗粒有机碳含量偏低,可能归因于河口最大浑浊带附近特殊的生物地球化学作用,如细颗粒物絮凝——沉降、微生物分解等。基于蒙特卡洛模拟的三端元混合模型的计算表明长江口分级颗粒有机碳主要来源于河流和三角洲输入,海洋来源贡献较小,三者的平均贡献比例分别为40%、35%和25%。在河口盐度梯度的淡水端,不同粒级颗粒物上三角洲来源的有机碳比例均随着盐度升高而增加,而在咸水端,海源有机碳的贡献比例升高,尤其是在16-32μm粒级,最高达39%。32-63μm粒级的颗粒物单位比表面积有机碳含量均大于1.0mg/m^2,小于32μm的颗粒物单位比表面积有机碳含量均在0.4-1.0mg/m^2的范围之内,符合河流颗粒物的一般特点,同时也说明细颗粒物上的有机碳可能已经发生了一定程度的分解,不过相对于长江口表层沉积物,颗粒物单位比表面积有机碳含量普遍较高,表明这些颗粒有机碳在沉降过程中或沉积之后还要经历进一步的再矿化分解,初步的估算表明,长江所输送的陆源有机碳约71%会在沉积过程中损失掉。本研究有助于深入了解大河河口不同粒级颗粒物在有机碳迁移转化过程中的作用,深化对高浊�Knowledge of the transport of particulate organic carbon in large-river estuaries from the perspective of sizefractionation is key to better understand the biogeochemical processes of organic carbon during the mixing of freshwater and seawater.Suspended particulate matters（SPM） in surface water were collected along a salinity gradient in the turbidity maximum zone of the Changjiang Estuary in June 2011,and then were separated into different size fractions using the water elutriation method,Organic carbon（OC） and nitrogen,stable carbon isotopic composition and specific surface area（SSA） of these size-fractionated particles were analyzed to discuss the variation of sources,distribution and preservation of OC with the increasing salinity and their impact factors.The results showed that with the increase of salinity and particle size,the size-fractionated particulate OC（POC） gradually reduced and mainly concentrated in less than 32μm fractions.The POC in the estuary was lower than those in the main stream,perhaps due to the special biogeochemical processes around the maximum turbidity zone,such as flocculating and settling of fine particles,microbial decomposition,etc.The results of the three end-member mixing model based on Monte-Carlo simulation indicated that the POC was mainly from riverine and deltaic sources,whereas the contribution from marine end-member was relatively small,and the average fractions of these three end-members were 40%,35%and 25%,respectively.In the freshwater end,deltaic OC of the size fractions increased with the increase of salinity,but in the seawater end,the contribution of marine OC increased,especially in the 16-32μm fractions,with the maximum value of 39%.The SSA normalized OC contents of the 32-63μm fractions were all larger than 1.0 mg/m^2,while the OC/SSA ratios of less than 32μm fractions were in the range of 0.4 to 1.0 mg/m^2,consistent with the typical characteristics of river suspended particulates.Furthermore,the OC/SSA ratios also indicated that OC in fine

关 键 词：长江口 悬浮颗粒物 水淘选法 粒径分级 有机碳 稳定碳同位素 

分 类 号：P734.2[天文地球—海洋化学]