太湖水质时空分布特征及内源释放规律研究

Analysis to the characteristics of temporal and spatial distribution of the pollutant and the law of release from sediment in Taihu Lake

将太湖 2 0 0 1～ 2 0 0 2年的水质监测数据与空间数据相结合 ,采用基于因子分析的主成分分析方法将太湖的水质参数概括为 5个主成分 ,提取并反证了湖泊水质各个主成分的科学内涵 ,分别为 :水体营养指数 (F1)、富营养化指数 (F2 )、水体溶解氧指数 (F3 )、水体色度指数 (F4)和水体酸碱指数 (F5 ) ;研究了各主成分的空间分布特征和随时间的变化规律 .在室内环形水槽内模拟了水动力条件下太湖底泥的起动规律 ,得到了太湖底泥在 3种不同起动标准 (个别动、少量动、普遍动 )下的起动流速 ,并利用泥沙起动的理论模型给予了验证 ,最后得出太湖底泥在 3种不同起动标准下的起动流速分别为 :3 7.9cm·s- 1 ,46 7cm·s- 1 ,5 9 8cm·s- 1 .通过考察上覆水中TN、TP浓度的变化 ,建立了底泥中TN、TP释放率与水体流速的定量化关系 .并将太湖水量水质的同步监测资料应用在数学模型中 ,解决了以往模型中底泥释放率取为常数的不足 。

The principal constituent analysis method was used, and five principal constituents of Taihu Lake were generalized by uniting the water quality monitoring data with the spatial data of Taihu Lake from the year 2001 to 2002. The science connotations of these five principal constituents are nutritive index (F1), eutrophication index (F2), dissolved oxygen index (F3), color index (F4) and pH index (F5), respectively. The characteristics of the spatial distribution and the variation law of the monthly averaged value with time for every principal constituent were studied. A conclusion could be attained that F1, F3 were the primary driving factors. The theoretical model of sediment starting to move was also used to calculate the incipient velocity and the incipient shear stress of Taihu Lake at three different starting standards. The calculated values were 37.9cm·s^(-1), 46.7cm·s^(-1), 59.8cm·s^(-1) and 0.428N·m^(-2), 0.636 N·m^(-2),1.042N·m^(-2), respectively. Then, the starting law of sediment in Taihu Lake was simulated indoors in an annular tank, the different stages of sediment movement were analyzed, and the changes of TN (Total Nitrogen) and TP (Total Phosphorus) in upper wing covert water with velocity were studied. The experimental results showed that the incipient velocities of sediment in Taihu Lake at three different starting standards which were gained from lab experiments were 35cm·s^(-1), 45cm·s^(-1) and 60cm·s^(-1), respectively, which were accorded with those calculated values. The relationship between TN and TP in upping wing covert water and velocity showed that when the velocity was relatively slow, the release rate of TN,TP from sediment were small; while the velocity was rapid, the release rate of TN and TP from sediment were very high. And the concentration of TN and TP was jumped significantly at the three different incipient velocities, which could prove the good fitness of the calculated and experimental values further. The relational expression between the release rate of TN, TP and water velocity were calculated on the basis of the relationship between the concentration of TN, TP and water velocity. Furthmore, these results were applied in water flow and water quality numerical model. The applying results were satisfactory by using this model.