太湖水体中悬浮颗粒物的比吸收光谱特性及其参数化分析

通过对太湖水体的野外采样,利用定量滤膜技术测量了水体中浮游植物色素的吸收系数(aph(λ))和非色素颗粒物的吸收系数(aNAP(λ)),进而推算比吸收系数.同时,对浮游植物色素和非色素颗粒物的比吸收系数的时空变化特征进行了分析.结果表明,浮游植物色素的比吸收系数(ap*h)在蓝光440nm的变化范围为0.008～0.268m2·mg-1,在红光670nm的变化范围为0.004～0.098m·2mg-1;;通过K-Mean算法将浮游植物色素的比吸收光谱分成3种具有不同光谱特征的类型,类别1、2和3占总数的百分比分别为61.0%、12.2%和26.8%,表明太湖水体中浮游植物色素的比吸收光谱是以类别1为主;;色素包裹效应因子Qa*(675)在Chla浓度<50mg·m-3时,随Chla浓度的增大迅速减小,而在Chla浓度>50mg·m-3时,其减小的趋势趋于缓慢,Qa*(675)与Chla浓度呈现出较好的幂函数关系.非色素颗粒物的比吸收系数(aN*AP)在蓝光440nm处的变化范围为0.012×10-3～0.143×10-3m2·mg-1,利用此处的比吸收系数建立的非色素颗粒物比吸收光谱的参数化模型,光谱曲线斜率...

Specific absorption characteristics of suspended particles in Lake Taihu and parameter analysis

Four field investigations were carried out in Lake Taihu in 2006 and 2007 to measure absorption coefficients of phytoplankton and non-algal particles. We used quantitative filter technology (QFT), which can further deduce specific absorption coefficients. At the blue light wavelength of 440 nm, a*ph varies from 0.008 m2·mg-1 to 0.268 m2·mg-1, while at the red light wavelength of 670 nm, the variation range is 0.004~0.098 m2·mg-1. Three types of specific absorption spectra with different characteristics were divided by the K-Mean algorithm. Type 1 spectra account for 61.0% of all spectra, while type 2 and 3 account for 12.2% and 26.8%, respectively. This implies that type 1 dominates the specific absorption spectra of phytoplankton in Lake Taihu. The package effect index Q*a(675) decreases sharply when Chla concentration <50 mg·m-3, and slowly decreases when Chla concentration >50 mg·m-3. The variation of Q*a(675) along with Chla can be simulated by a power function. At 440 nm, the specific absorption coefficients of non-algal particles range from 0.012×10-3 to 0.143×10-3 m2·mg-1, and the specific absorption spectra can be modeled with high accuracy, where S changes from 0.0049 to 0.0133 nm-1 with a mean of (0.0091±0.0029) nm-1. An exponential model can be used to simulate the relationship between a*NAP and NAP concentrations with R2=0.502. The spatial and temporal changes of the specific absorption coefficients of phytoplankton and non-algal particles were also analyzed.