长江中下游浅水湖泊悬浮颗粒物吸收系数测定方法探讨

Determination of the spectral absorption coefficients of suspended particulate matters in the shallow lakes in the middle and lower reaches of Yangtze River

对两种水体悬浮颗粒物吸收系数测定方法及相关计算进行对比研究.通过长江中下游湖泊典型藻类的实验室培养,利用T方法和T-R方法分别对藻类颗粒物、藻类泥沙混合悬浊液进行吸收系数测定.通过颗粒物光谱吸收系数与叶绿素a之间的相关性关系,对比了两种方法的测量稳定性.通过对不同比例的藻类和无机悬浮颗粒物(ISS)的混合悬浊液进行分析,获得了不同浊度水体悬浮物吸收光谱的变化情况.结果表明,在纯藻或者泥沙含量较少的水体进行颗粒物吸收系数光谱测定时,T方法和T-R方法均可以采用,并且均具有较高的测定精度.然而,在泥沙含量相对较高的浑浊水体,应尽量选取T-R方法进行颗粒物吸收光谱的测定,以提高测定精度.长江中下游浅水湖泊由于底泥易受风浪影响发生再悬浮,因此在颗粒物吸收系数光谱测定中,当水体中ISS含量超过30 mg/L时,应选择T-R方法.

Two methods for measuring absorption coefficients of suspended particulate matters in water were studied and compared. Through the laboratory culturing of typical algae from the shallow lakes in the middle and lower reaches of Yangtze River, the algal particles and the suspension of algae and sediments were determined by Transmittance （ T） and Transmittance-Reflectance （ T-R） methods, respectively. The measuring stability of the two methods was compared according to the relationships between the spectral absorption coefficients and Chlorophyll-a of the suspended matters. To obtain absorption spectral changes of suspended matters at different levels of turbidity water, the suspension composed of algae and inorganic particles in different concentration gradients were analyzed. The results showed that both T and T-R methods could be applied and have high measurement precisions in pure algae or water containing less inorganic suspended particulate matters. However, the T-R method should be selected for the suspended par-ticulate matter absorption spectra determination in turbid water. This can improve the measurement precision. Considering that the sediments in the study area are susceptible to wind and thus re-suspension, when the inorganic suspended particulate matters in wa-ter exceeded 30 mg/L, the T-R method should be selected.