鄱阳湖枯水期CDOM光吸收特性与DOC浓度的定量关系研究

摘要

研究了2015年枯水期鄱阳湖水体(包括河口区、鄱阳湖主湖开阔区)有色可溶性有机物(CDOM)的光吸收特性,并讨论了CDOM光吸收特性与溶解性有机碳(DOC)浓度之间的关系.结果表明,整个鄱阳湖水体中CDOM在254、280、350和440 nm波长处的吸收系数分别为7.86~20.24、5.64~14.58、1.46~4.41和0.36~1.06 m-1;表征CDOM相对分子质量大小的M值(CDOM在波长250和365 nm处吸收系数比值)变化范围为5.27~7.66.枯水期湿地对鄱阳湖水体CDOM的影响较大,而5大入湖河流贡献不大.在各项参数中,光谱斜率比值(SR)更能体现枯水期鄱阳湖水体CDOM光吸收特征.枯水期鄱阳湖水体ρ(DOC)在1.61~4.86 mg·L-1之间变化,其平均值为2.31 mg·L-1.枯水期鄱阳湖水体CDOM光吸收系数(a254,x)与DOC浓度(y)呈显著正相关,回归方程为y=-0.53+0.27x(调整决定系数R2=0.76,P<0.01),2016年1月的实测值验证显示利用枯水期鄱阳湖水体CDOM光吸收特性研究DOC浓度具有可行性.这意味着研究枯水期鄱阳湖水体CDOM光吸收特性对研究碳库具有指示作用.%Optical absorption properties of chromophoric dissolvable organic matter ( CDOM) in the waters of the Poyang Lake including estuaries and the main waterbody in the dry season of 2015 were studied and their relationships with dis?solved organic carbon ( DOC) discussed. Results show that CDOM absorption coefficient in the Poyang Lake at 254, 280, 350, and 440 nm ( wave length) varied in the range of 7. 86-20. 24, 5. 64-14. 58, 1. 46-4. 41 and 0. 36-1. 06 m-1 , re?spectively, and M value, an index characterizing relative molecule size, did in the range from 5. 27 to 7. 66. During the dry season, wetlands were a major factor affecting CDOM concentrations in the lake, whereas the five major incoming riv?ers did not have much contribution to CDOM. Among the numerous parameters, SR was the major index reflecting optical absorption properties of CDOM in the lake during the dry season. DOC in the dry season varied in the range from 1. 61 to 4. 86 mg·L-1 , with a mean value of 2. 31 mg·L-1 . CDOM optical absorption coefficient( a254 ,x) was positively related to DOC concentration ( y) . The relationship was fitted with the linear regression equation y=-0. 53+0. 27x and calibrated with the equation Adj. R2=0. 76, P<0. 01. Validation with the field measurements conducted in the Poyang Lake in Janu?ary 2016 demonstrates that it is feasible to use optical absorption properties of CDOM in the waterbody of the Poyang Lake during the dry season to explore DOC concentration in the lake water, which means that CDOM in the Poyang Lake in the dry season can be used as an indicator in the study on carbon pool in the lake.