Water Quality Monitoring Analysis Of Main Channel In Hangzhou Reach Of Qiantang River And Experimental Study Of Central Discharge

Qiantang River is the largest river in Zhejiang Province, the water quality condition of which is directly related to sustainable development of economy and society in the region. Due to the input of nutrients such as nitrogen and phosphorus, large area of cyanobacterial bloomed in the Qiantang River Basin in2004, which seriously affected the normal life of the people within the watershed. Therefore, it is particularly necessary for us to monitor and analyze the water quality of Qiantang River, and the result in the investigations would provide a reference to control the water pollution.This paper detected the water quality indicators in Hangzhou reach of Qiantang River by field investigations and indoor experiments in May and September,2011. According to monitoring data, we analyzed the temporal and spatial distribution features of these indicators, include blue-green algae, chlorophyll a and other related physical and chemical indicators. In addition, we studied the distribution law of total phosphorus, total nitrogen and total organic carbon in sediment samples along monitoring cross-sections. The relationships between chlorophyll a and water quality indicators were analyzed, which showed that there were significant positive correlations between chlorophyll a and blue-green algae, total phosphorus, total nitrogen, pH value in May. In September, chlorophyll a only related with blue-green algae, pH value, but the relationships with total phosphorus and total nitrogen were not obvious. Water quality condition of Qiantang River was evaluated under (surface water environment quality standard GB3838-2002), which showed total nitrogen concentrations seriously overweight. Furthermore, we used principal component analysis to analyze water quality indicators, and the results showed that the main pollution of the Qiantang River was biological contamination caused by algae blooming due to input of nutrients. The pollution of Zhakou and Qibao cross-sections in the downstream were more serious than others.With the acceleration of urbanization and the height concentration of urban population and industry, the emissions of sewage are also growing, When the amount of sewage discharged exceed the self-purification capacity of receiving water, the receiving water would be heavily polluted. Pollutants further expand their sphere of influence by migration, proliferation and transformation in receiving water. Reasonable control of pollutant emissions, and taking full advantage of blending dilution effect between the emission process and rivers, oceans, other water bodies and water self-purification ability, not only can reduce the cost of sewage treatment, but also not cause serious damage to our environment. Therefore, the study in flow field of pollutant discharge in hydrodynamic environment has a certain value of engineering application. In this paper, the Acoustic Doppler Velocimeter(ADV) was used to measure the three-dimensional velocity of central discharge under stationary and crossflow environments, and we compared flow field and velocity distribution in three directions under two environments. Moreover, we analyzed effect of mixing between central discharge and environmental water produced by the sink crossflow.