太湖梅梁湾水体悬浮颗粒物吸收系数的分离

Partitioning spectral absorption of particulate matter in Meiliang Bay of Lake Taihu

针对2004年7月17日梅梁湾16个采样点悬浮颗粒物的吸收系数,利用基于光谱标准的方法,将悬浮颗粒物的吸收系数分离成藻类和非藻类颗粒物两种,并将其中藻类颗粒物的吸收系数与通过甲醇浸泡法所得的结果进行分析对比．结果表明:利用甲醇浸泡提取法对藻类、非藻类吸收系数的分离,当非藻类颗粒物浓度较高时,所得的藻类吸收系数呈现出较明显的非藻类颗粒物的特征,造成藻类颗粒物吸收系数有所放大,且在短波段处体现的尤为明显;而基于光谱标准的模拟法能较好地将藻类颗粒物的吸收系数从总悬浮颗粒物吸收系数中分离出来,与甲醇浸泡法相比,藻类颗粒物在440、675 nm吸收峰处的吸收系数与叶绿素a的浓度相关性(R3)得到了较为明显的提高,分别由原来的0．66、0．75提高到了0．8964和0．8401;就甲醇浸泡法而言,总悬浮物吸收系数的谱形状对藻类吸收系数的放大程度有较大的影响,当其越接近藻类颗粒物的吸收特征时,则色素提取法造成的误差越小,相反,当其越接近非藻类颗粒物的吸收特征时,则甲醇浸泡法造成的误差越大．

Based on the absorption coefficients at 16 sampling sites in Meiliang Bay on July 17 2004, the absorption coefficients of algal particles were discriminated from those of nonalgal particles by the method of spectral criteria, and compared with those by methanol-extractions. The results were as follows. Discriminated from absorption coefficient of nonalgal particles by methanol-extractions, the absorption coefficient of alga particles shows the absorption characters of nonalgal particles when the concentration of nonalgal particles is high. The absorption coefficients of algal particles are overestimated especially in short wave band. By the method of spectral criteria, the absorption coefficients of nonalgal and algal particulates can be successfully separated. Compared with the partition by methanol-extractions, the limear correlation coefficients between absorption coefficient of algal particles at 440 nm and 675 nm and the concentration of chlorophyll a significantly increase. The limear correlation coefficients increase to 0.8901 and 0.8401 from 0.66 and 0.75 at 440 and 675 nm, respectively. As far as the method of methanol-extractions is coneerned, the spectral shape of absorption coefficient of particles matter significantly affects the degree of over-estimating the absorption coefficient of algal particles. When the spectral shape of absorption coefficient of particles matter is much more similar to that of alga particles, the error is lower; on the contrary, the error is bigger.