太湖梅梁湾有色可溶性有机物对光的吸收

Absorption of light by chromophoric dissolved organic matter (CDOM) in Meiliang Bay of Taihu Lake

探讨了太湖梅梁湾不同湖区有色可溶性有机物(CDOM)对光的吸收、光衰减系数的变化及与DOC浓度的关系、CDOM吸收对光衰减系数的贡献率以及指数函数曲线斜率S值.结果表明,不同类型湖区CDOM吸收系数差异明显,ad(440)、ad(320)的变化范围分别为1.22～2.58m-1,6.24～10.69m-1;DOC浓度最高值出现在梁溪河口,为12.74mg/L,最低值出现梅梁湾口,为6.87mg/L,大致呈由湾内向湾口逐渐递减的趋势;DOC与CDOM吸收系数在波长320nm以下存在显著性相关,波长320～700nm CDOM吸收对光衰减系数的贡献率在0.69%～60.9%间变化,400nm以下紫外短光部分贡献率均大于20%,空间上短波部分贡献率在河口区、五里湖比梅梁湾内及沿岸带要大;CDOM吸收的指数函数曲线斜率S在13.9～18.1μm-1间.

In different lake regions in Meiliang Bay of Taihu Lake, absorption of light by CDOM, change of light attenuation coefficients and relationship with DOC concentration, contribution rate of absorption of CDOM to light attenuation coefficient and exponential slope coefficients were explored. The CDOM coefficient differed obviously in different lake regions; the change range of ad(440) and ad(320) was 1.22~2.58m-1 and 6.24~10.69m-1, respectively. The highest and lowest DOC concentrations were in mouth of Liangxi River and mouth of Meiliang Bay with a maximum value 12.74mg/L and a minimum value 7.87mg/L, respectively, tending to decrease gradually from inside to mouth of the bay; and a significant linear relationship was found between DOC concentrations and CDOM absorption coefficients under 320nm. The contribution rate of CDOM absorption to light attenuation coefficient changed in 0.69%~60.9% at 320~700nm. The contribution rates were more than 20% during the ultraviolet range at 280~440nm, and the values were higher in Wuli Lake and river mouth area than those in inside of Meiliang Bay and littoral belt. The exponential slope coefficient S of CDOM was 13.9 to 18.1m-1 at 280~440nm.