长江口及邻近海域春夏季有色溶解有机物时空分布特征及主要影响因素

利用三维荧光光谱(EEMs)-平行因子(PARAFAC)分析技术对长江口及邻近海域春季(2015年3月)和夏季(2015年7月)有色溶解有机物(CDOM)的荧光组成及分布特征进行分析.共识别出2类4个荧光组分,即类腐殖质组分C1(370/495nm)、C2(330/405 nm)、C3(365/440 nm)及类蛋白质组分C4(295/345 nm).春夏季各层4个荧光组分分布模式基本一致,从长江口到邻近海域逐渐降低.春季类腐殖质组分的高值区分布在长江口内,而类蛋白组分高值区位于南槽附近区域,表层的CDOM主要来源于陆源输入和人类活动;中层荧光强度值比表层低,受陆源影响减弱;底层荧光强度值比中层略高,是由沉积物再悬浮造成的.各荧光组分在岱山县附近海域均有一个较高值,这与岛上的居民活动有关.夏季荧光组分高值区与春季相似,各层荧光组分值接近,说明夏季研究区域水体混合较均匀.春夏季腐殖化指数(HIX)在长江口较高,而生物指数(BIX)在邻近海域较高.将4个荧光组分(C1~C4)、吸收系数(a355)与盐度(S)、溶解有机碳(DOC)、总氮(TN)、总磷(TP)、叶绿素a(Chl-a)、溶解氧(DO)做冗余分析.结果表明,4个荧光组分(C1~C4)与总氮(TN)、总磷(TP)主要受陆源输入、人类活动的影响,溶解有机碳(DOC)受陆源与海源的共同影响.本文利用三维荧光光谱-平行因子分析(EEMs-PARAFAC)技术结合多元统计方法解析了CDOM组成,清晰揭示了长江口及邻近海域CDOM的来源及主要影响因子,可为河口海域生源要素海洋生物地球化学研究提供有益的补充.

Assessment of the Spatial-temporal Distribution Characteristics and Main Affecting Factors of Chromophoric Dissolved Organic Matter in Spring and Summer at the Changjiang Estuary and Adjacent Areas

The composition and distribution characteristics of chromophoric dissolved organic matter(CDOM) of Changjiang Estuary and its adjacent waters in spring (March 2015) and summer (July 2015) were evaluated by excitation-emission matrix spectroscopy (EEMs) in combination with parallel factor(PARAFAC) analysis. Three humic-like components[C1(370/495 nm),C2(330/405 nm),C3(365/440 nm)] and one protein-like component[C4(295/345 nm)] were identified. The distribution patterns of the four components in spring and summer were almost the same, showing a decreasing trend from Changjiang Estuary to adjacent waters. In spring, the high value areas of three humic-like components were located inside of Changjiang Estuary, and the high value areas of the protein-like component were located in the South Passage of Changjiang Estuary. In the surface layer, the CDOM was mainly from terrestrial input and human activities; the influence of terrestrial weakened in the middle layer because of the lower fluorescence intensity values; and in the bottom layer the fluorescence values were higher than those in the middle layer, which was caused by sediment resuspension. There were high value areas in the Daishan Island, which were related to human activities. In summer, the high value areas of CDOM were almost the same as those in spring, and all layers had similar fluorescence intensity values, which indicated that they were mixed evenly. CDOM in spring and summer had high humification index (HIX) values in the Changjiang Estuary, whereas for biological index (BIX), its high values appeared in the adjacent waters. Four components (C1-C4), a₃₅₅ and DOC, TN, TP, DO, Chl-a, Salinity were evaluated by redundancy analysis (RDA), which indicated that C1-C4 and TN, TP were mainly affected by terrestrial input and human activities, and DOC was affected by terrestrial and marine source together. The use of EEMs-PARAFAC in combination with multivariate analysis to parse the composition of CDOM revealed the source of CDOM and main influencing factors in Changjiang Estuary and adjacent waters, and plays an important role in the biogeochemical research of biogenic elements in estuarine waters.