太湖北部湖区COD浓度空间分布及与其它要素的相关性研究

利用2004年夏季在太湖北部湖区的采样数据,分析了化学需氧量(COD)浓度的空间分布,建立了COD浓度与有色可溶性有机物(CDOM)吸收、荧光、溶解性有机碳(DOC)浓度之间的定量关系.并以2004-01、2005-01、2007-06的数据探讨了COD的来源.结果表明,夏季COD浓度的变化范围为3.77～7.96 mg·L-1,均值为(5.90±1.54)mg·L-1. COD浓度从梅梁湾内往湾口再往大太湖呈现逐渐降低趋势,梅梁湾和大太湖的均值分别为(6.93±0.89)ms·L-1、(4.21±0.49)mg·L-1,梅梁湾的值显著要高于大太湖开阔水域. COD浓度与CDOM吸收、荧光、DOC浓度存在显著的正相关.通过对光学活性物质CDOM浓度的反演,可以外推水体有机物污染程度,为日后利用遥感影像反演和评估太湖水体有机物污染状况奠定基础.夏季COD浓度与叶绿素a浓度存在极显著正相关,而冬季没有相关或这种相关性很弱,并且夏季的值明显要高于冬季的值,反映了除入湖河流带来外源COD的输入外,夏季浮游植物大量生长死亡腐烂后的降解产物也是水体中COD的重要来源.

Spatial Distribution of COD and the Correlations with Other Parameters in the Northern Region of Lake Taihu

Spatial variation of chemical oxygen demand (COD) concentration was documented and significant correlations between COD concentration and chromophoric dissolved organic matter (CDOM) absorption, fluorescence, DOC concentration were found based on a cruise sampling in the northern region of Lake Taihu in summer including 42 samplings. The possible source of COD was also discussed using every two cruise samplings in summer and winter, respectively. The COD concentration ranged from 3.77 to 7.96 mg·L^-1 with a mean value of (5.90±1.54) mg·L^-1. The mean COD concentrations in Meiliang Bay and the central lake basin were (6.93±0.89) mg·L^-1 and (4.21±0.49) mg·L^-1 respectively. A significant spatial difference was found between Meiliang Bay and the central lake basin in COD concentration, CDOM absorption coefficient, fluorescence, DOC and phytoplankton pigment concentrations, decreasing from the river mouth to inner bay, outer bay and the central lake basin. Significant correlations between COD concentration and CDOM absorption, fluorescence, DOC concentration, suggested that COD concentration could be estimated and organic pollution could be assessed using CDOM absorption retrieved from remote sensing images. Significant and positive correlation was found between COD concentration and chlorophyll a concentration in summer. However, the correlation was weak or no correlation was found in winter. Furthermore, a significant higher COD concentration was found in summer than in winter (p<0.001). Our results indicated that degradation of phytoplankton blooms was the main source of COD in summer, except for river terrestrial input.