青藏高原典型湖库光学吸收特性与光合有效辐射衰减系数初步研究

青藏高原地区分布的湖泊数量众多、面积较大、分布范围广泛.受制于恶劣的自然条件,对该地区湖泊的光学吸收特性以及光合有效辐射衰减系数(Kd(PAR))的研究鲜有成果.本文依据2014和2015年间采集的13个典型高海拔、湖泊面积较大的湖库的现场实测数据和实验室测定数据,分析了采样湖库各个采样点的Kd(PAR)特征以及有色可溶性有机物(CDOM)、藻类颗粒物吸收及非色素颗粒物吸收特性,计算并分析了Kd(PAR)与透明度以及光学活性物质的关系.研究结果表明:青藏高原地区各湖库平均各项颗粒物吸收系数均较低,总颗粒物吸收系数在400~700 nm波段内不超过0.14 m~(-1)、CDOM吸收系数在355 nm波长处最高,为1.23 m~(-1)、最低接近于0、藻类颗粒物吸收特性不明显;实验数据完整的巴木错、格仁错和班公错的主导吸收组分各异,其中巴木错为CDOM吸收主导,格仁错与班公错为非色素颗粒物吸收主导;青藏高原采样湖泊总体Kd(PAR)平均值较小,仅为0.26 m~(-1),样点最大值出现在可鲁克湖(1.17 m~(-1)),最小值出现在普莫雍错(0.10 m~(-1));在采样湖泊中Kd(PAR)与透明度呈显著相关;Kd(PAR)与CDOM的相关性最强,叶绿素a浓度次之,与总悬浮颗粒物浓度的相关性最不显著.

Optical absorption properties and diffuse attenuation of photosynthetic active radiation for inland waters across the Tibetan Plateau

Numerous large lakes and reservoirs are distributed in the Tibetan Plateau. Because of the adverse environment, studies for optical absorption property in lakes and especially the diffuse attenuation of photosynthetic active radiation (K_d(PAR)) are quite limited. Here we present multiple absorption characteristics of optically active constituents and K_d(PAR) collected from 13 alpine lakes in 2014 and 2015, and analyze the relationship between K_d(PAR) and various optically active constituents. The results revealed that the absorption coefficient of total suspended matter (TSM) was less than 0.14 m^-1 which was low within 400-700 nm. The absorption coefficients of chromophoric dissolved organic matter (CDOM) in 355 nm reached a peak of 1.23 m^-1 and achieved 0 approximately in the bottom. Algal absorption was not obvious in Tibetan lakes and reservoirs, and the dominant absorption constituent varied among Bam Co, Gering Co and Pangong Co. The absorption of CDOM was dominated for the total absorption in Bam Co, while the total absorption of Gering Co and Pangong Co was dominated by the absorption of non-algal particles. Mean value of K_d(PAR) was 0.26 m^-1 which was low in all sites compared to the existed research results of K_d(PAR) in several lakes and reservoirs, and the maximum and minimum of K_d(PAR) were observed in Lake Keluke (1.17 m^-1) and Lake Puma Yumco (0.10 m^-1), respectively. Significant correlation existed between K_d(PAR) and secchi disk depth, and it was also found between K_d(PAR) and CDOM dramatically. Correlation between K_d(PAR) and chlorophyll-a was not so conspicuous, and K_d(PAR) was not in good agreement with TSM.