千岛湖水体悬浮颗粒物吸收特性及其典型季节差异

利用千岛湖2012年12月~2013年2月冬季及2013年6~8月夏季的采样数据,分析了千岛湖水体的营养水平和悬浮颗粒物的吸收特性季节变化及空间分布规律.结果表明千岛湖营养水平夏高冬低,整体处于中营养水平.冬季和夏季总悬浮颗粒物吸收系数在440 nm的均值分别为:(0.20±0.07)m-1和(0.24±0.17)m-1;675 nm的均值为(0.07±0.02)m-1和(0.10±0.07)m-1;夏季显著高于冬季(t-test,P<0.05).冬季总悬浮颗粒物的吸收光谱可分为两种情况:西北湖区与浮游植物吸收类似,其它站点与非藻类颗粒物的吸收相似;而夏季,在可见光范围,50%以上总悬浮颗粒物的吸收是由藻类颗粒物贡献,因此,总悬浮颗粒物的吸收光谱曲线与浮游植物光谱曲线类似.冬夏季浮游植物吸收系数差异显著(P<0.05),440 nm均值分别为(0.10±0.03)m-1和(0.17±0.14)m-1;相应地675 nm的均值为(0.05±0.02)m-1和(0.08±0.07)m-1.冬季和夏季440 nm浮游植物比吸收系数(以Chla计)的均值分别为:(0.045±0.010)m2·mg-1和(0.039±0.013)m2·mg-1;675 nm处为:(0.022±0.004)m2·mg-1和(0.019±0.005)m2·mg-1.440 nm和675 nm浮游植物吸收系数随Chla浓度及综合营养状态指数的增加线性增大;比吸收系数和Chla浓度呈幂函数关系,随Chla浓度增大而减小.冬季非藻类颗粒物吸收与无机颗粒物的相关性最好;夏季440 nm非藻类颗粒物吸收与总悬浮颗粒物和有机颗粒物呈线性关系,随着总悬浮颗粒物和有机颗粒物含量增加非藻类颗粒物吸收增加.

Characteristics of Optical Absorption Coefficients and Their Differences in Typical Seasons in Lake Qiandaohu

Absorption characteristics of total suspended particulate, phytoplankton and tripton in Lake Qiandaohu are presented based on the in situ data collected in winter (from December 2012 to February 2013) and summer (from July to August 2013). The mean values of total suspended particle absorption coefficients at 440 nm a_p(440)]in winter and summer are (0.20±0.07) m^-1 and (0.24±0.17) m^-1. Correspondingly, the mean values of a_p(675) are (0.07±0.02) m^-1 and (0.10±0.07) m^-1. In winter the absorption spectra of total suspended particulate matters can be divided into two cases: the absorption spectra are similar to those of phytoplankton in the northwest lake and to those of tripton in other lake regions. In summer, the absorption spectra of total suspended particles are similar to those of phytoplankton from 400 nm to 700 nm. The mean values of phytoplankton absorption coefficients at 440 nm a_ph(440)] are (0.10±0.03) m^-1 in winter, and (0.17±0.14) m^-1 in summer. Accordingly, the mean values of a_ph(675) are (0.05±0.02) m^-1 and (0.08±0.07) m^-1. The mean values of Chlorophyll-specific absorption coefficients (by the concentration of Chla) at 440 nma_ph^*(440) are (0.045±0.010) m²·mg^-1 in winter and (0.039±0.013) m²·mg^-1 in summer. At the same time, the mean values of a_ph^*(675) are (0.022±0.004) m²·mg^-1 and (0.019±0.005) m²·mg^-1. Significantly linear correlations are found between phytoplankton absorption coefficients and chlorophyll a concentration, trophic level index (TLI). Chlorophyll-specific absorption coefficients vary with the chlorophyll a concentrations following a power function. The tripton absorption coefficients exponentially decrease from 400 nm to 700 nm. The correlation between tripton absorption coefficients and inorganic particles is significant in winter, whereas, the correlation between tripton absorption coefficients and the concentrations of total suspended particles and organic particles are significant in summer.