太湖中颗粒有机碳对水体固有光学特性的影响

利用2011年5期太湖现场测量数据和室内分析数据,通过建立ρ(POC)(POC为颗粒有机碳)与a_p(λ)(颗粒物吸收系数)、b_bp(510)(总颗粒物的后向散射系数)的相关关系,评价了POC对水体固有光学特性的影响. 结果表明,太湖水体ρ(POC)时空变化显著,各期样品平均值在1 558.06~5 281.09 mg/m3之间变化. ρ(POC)与a_p(λ)具有较好的相关关系,特别是在浮游植物色素强烈吸收的波段(605~700 nm),各期数据的相关系数均在0.9以上；但ρ(POC)与b_bp(510)的相关性较差(R2=0.04, P=0.02). 进一步分析ρ(POC)对颗粒物的色素部分和非色素部分的影响发现,ρ(POC)与色素颗粒物吸收系数〔a_ph(665)〕的相关性很好(R2=0.82),而与非色素颗粒物吸收系数相关性较差. ρ(NPOC)(NPOC为非有机碳颗粒物)与b_bp(510)的相关性较好(R2>0.60),说明太湖水体POC对浮游植物色素的吸光特性有重要影响,而NPOC影响了水体的后向散射特性. 

Effects of Particulate Organic Carbon on Inherent Optical Properties of Taihu Lake

Using field and laboratory datasets obtained from five cruises of Taihu Lake in 2011, the relationships between particulate organic carbon (POC) and coefficients of particle absorptions and backscattering were examined to evaluate the impact of POC assemblages on the inherent optical properties in eutrophic inland water. The results showed that concentrations of POC varied greatly in Taihu Lake among the five cruises, ranging from 1558.06 to 5281.09 mg/m3. There was a strong relationship between POC concentrations and particle absorptions, especially in the wavelengths, where absorption was dominated by phytoplankton pigment concentrations (605-700 nm), with Pearson's correlation coefficients higher than 0.9 in all the sampling champions. However, a weak correlation between POC and particulate backscattering coefficient, b_bp (510), was observed (R2=0.04, P=0.02). The influence of POC on the particle absorptions due to phytoplankton pigment and detritus was illustrated, with POC highly correlated with phytoplankton absorptions (R2=0.82) and poorly related to detrital absorptions. Instead, non-POC particles were highly correlated with backscattering coefficients (R2>0.60). In conclusion, POC greatly impacts the phytoplankton pigment absorptions, while non-POC sediments strongly influence the backscattering properties in Taihu Lake.