香溪河库湾春季水华期间可溶性碳动力学研究

KINETIC STUDY OF THE DISSOLVED ORGANIC CARBON IN THE XIANGXI BAY,THREE GORGE RESERVOIR REGION DURING THE SPRING BLOOM PERIOD

2005年2月23日—4月28日,对三峡水库香溪河库湾内一样点进行每天采样,监测水体中叶绿素a与可溶性碳(DOC)浓度的变化,研究在春季水华暴发期间DOC的动力学特性。监测结果表明,随着时间的推移,叶绿素a有逐渐升高的趋势。其间共暴发了两次水华,其中第一次历时较短,第二次历时较长。DOC的变化趋势与叶绿素a基本吻合。整个暴发过程中的叶绿素a与DOC的回归分析表明,二者具有较好的相关性(R2=0.62),但第一次暴发过程中的相关性很高(R2=0.72),而第二次暴发过程中的相关性较低(R2=0.30)。根据天然水体中DOC来源的主要途径,推测在第一次暴发过程中DOC的来源主要是水体中藻类的光合作用的代谢产物,而第二次暴发过程中DOC的来源主要是水体中藻类死亡腐烂而产生的有机物质。

Daily monitor for the chlorophyll a and dissolved organic carbon （DOC） was carried during the spring phytoplankton bloom period （22 Feb. ,-28 Apr., 2005）.The aim of this study was to research the kinetic characteristic of DOC during the spring phytoplankton bloom. 300--600mL of water sample was filtered by the mico-fiher （0.8μm） for chlorophyll a determination in the sampling boat using a hand held vacuum pump. And 60mL water sample was passed through a 25-mm diameter pre-ashed GF/F filters （450℃ ,4hr） for DOC determination. The DOC was measured using the NPOC methods using total organic carbon analyzer （Shimadzu, TOC-V） . The data of chlorophyll a showed the concentration of chlorophyll a was increased with the lapse of time, and phytoplankton bloom was observed twice. The first bloom standing a short period, and the second bloom standing a long period. The tendency of the concentration of DOC was similar to the chlorophyll a. Regression analysis showed that the concentration of DOC could explain 62% of the variability in chlorophyll a concentration in the whole monitoring period （R^2 = 0.62） . Considering the rules of the spring bloom, two stages of spring bloom were divided according the dynamics of the concentration of chlorophyll a： the first stage was ranged from Feb., 23 to Mar. , 28., the second stage was ranged from 29 Mar., to Apr., 28. Regression analysis for the relationships between DOC and chlorophyll a at different bloom stages was carfled out individually. The result showed that the DOC could explain 72 % variability in chlorophyll a concentration at the first bloom stage （R2 =0.72）, and it could only explain 30% variability in the chlorophyll a concentration at the second bloom stage, According to the main source of the DOC in the natural water body, it can be deduced that the major contribute of DOC may be produced by the phytoplankton photosynthesis in the first bloom period and the major contribution of DOC may be produced by the decomposing of died algae in the second bloom period.