长江口CDOM的光谱吸收特征以及DOC物源示踪意义

Optical absorption properties of CDOM and tracing implication of DOC in the Changjiang Estuary

通过测定2009年冬季长江口芦潮港至嵊泗海域表层水中有色可溶性有机物(CDOM)的光谱吸收和溶解有机碳(DOC)的浓度,分析CDOM的吸收系数α(355)和光谱斜率s值的空间分布特征,并探讨其来源及其与DOC的关系。结果表明:CDOM光学属性随盐度逐渐降低,18.96～28.00的盐度范围内,α(355)为0.268 9～1.183 1 m-1,均值为0.824 9 m-1,低于丰水期,与国内外研究相比偏低,表明长江口CDOM受控于陆源径流输入,CDOM浓度可能和长江流域植被覆盖率和以及径流量有关。光谱斜率s值的范围为0.011 3～0.017 4 nm-1,均值为0.015 3 nm-1,略低于丰水期。DOC浓度与盐度的负相关关系(R2=0.882)表明该研究区域的溶解有机质(DOM)输入主要来自陆源,CDOM与DOC的相关关系为CDOMα(355)=0.371DOC+1.012(R2=0.48),表明研究区域内CDOM对DOC具有一定的物源指示意义。

The spectral absorption properties of chromophoric dissolved organic matter （CDOM） and the concentration of dissolved or- ganic carbon （ DOC ） in the Changjiang Estuary from Luchaogang Dock to Shengsi Islands was studied during winter of 2009. The dis- tribution of absorption coefficient α （355） and spectral slope of CDOM were analyzed and the source character and relationship be- tween CDOM and DOC were discussed. Over a salinity range of 18.96- 28.00, α （355） ranged from 0. 2689 - 1.183 1 m^-1 , while the average value was 0. 824 9 m^-1 , lower than values in the wet season, also the other estuaries of China and abroad, which may be attributed to the low degree of vegetative cover in the Changjiang drainage basin and low river flow in winter. The river discharge has significantly influenced on the CDOM distribution in the estuary. The spectral slopes varied from 0. 011 3 to 0. 017 4 nm-1 , and the average value was 0. 015 3 nma ,a little lower comparing with that in the wet season. The inverse relationship between DOC and salin- ity （R2 = 0. 882） showed the dissolved organic matter （DOM） were primarily terrestrial. And the relationship between CDOM and DOC （ CDOM,α（355） =0. 371DOC ＋ 1. 012 （R2 =0.48） ） showed that CDOM was a promising tracer for the land source DOC, but the stable inverse model need further study.