长江下游湖泊水体中有色可溶性物质的生物光学模式

通过2001年7月至2002年12月对长江下游的太湖、巢湖、龙感湖水体中有色可溶性物质的光吸收及荧光特性的研究发现:在对S值进行测定时,所测得的S值为0·0046nm-1(SD=0·0015,n=284),与文献中的0·014nm-1相差较大,可能是由于高浓度的DOC受到激发后在蓝光波段释放较强荧光的缘故;荧光强度与水体中DOC含量之间的关系较难确定,DOC与350nm光吸收(a(350nm))之间呈现较强的线性关系,其相关值达到0·673(n=284);荧光强度与a(350nm)之间线性关系相对较弱,其相关值为0·497(n=214);从上面的结果可以看出,用荧光的方法直接测定DOC含量的可信度相对较低,而直接利用光吸收测定的可信度较高。

The Bio-Optical Model of Chromatic Dissolved Organic Carbon in Lake Waters at Low Reach of Changjiang River

Dissolved organic carbon is the main component of dissolved carbon in water, and contributes to the control of the chemical states and the residence times of the other elements or materials existing there. Chromatic dissolved organic carbon(CDOC) is the fraction of the dissolved organic carbon(DOC) pool that absorbs light in both the ultra violet and visible ranges. CDOC is of particular interest to remote sensing because it absorbs blue light in the same region of the spectrum as chlorophyll a. The significant absorption of light in the blue wavelengths by CDOC can result in overestimation of chlorophyll a by satellite sensors in open ocean waters. CDOC can also emit fluorescence when being excited by light and fluorescence measurements have been used in oceanography since the early sixties to detect chromophoric constituents of dissolved organic matter. Nowadays these measurements are widely used in water mass analysis as well as for phytoplankton biomass determinations. The absorbance and fluorescence of chromatic organic carbon in Lake Tai, Lake Chao and Lake Longan at the lower reach of Changjiang River were studied for the period from July 2001 to December 2002. The results show as follows. S value was 0.0046nm -1(SD=0.0015,n=284), far less than 0.014nm -1 in the literature, maybe due to intense fluorescence emitted by high concentration of DOC when being excited; the relationship between florescence intensity and DOC content was uncertain; there was a good linear fitness of DOC content and a(350), relativity value reached 0.673(n=284); but there is weak relationship between florescence intensity and a(350), relativity value only at 0.497(n=214); The results showed that it had higher accuracy of DOC value by using absorbance than that of fluorescence.