Study On Characteristics Of Nitrogen Forms Of The Jialing River Backwater Area And Nitrate Reductase Activity

After the completion of the Three Gorges water control project, it forms a reservoirdrawdown belt with a vertical drop of up to30m in a year. The water level changes byhuman controlled from January to April each year, that is bound to make the naturalstate of the river water conservancy hydrology changes, and thus have an impact on thewater environment of the Three Gorges Reservoir. Through the research of diatomsproliferated indoor, the scholars found nitrogen, phosphorus and silicon concentrationsof the nutrient solution were decreased, with the growth of algae, but the rangeability ofphosphorus was not great, and after supplementation nitrogen when the content ofnitrogen reduced to the lowest point, found that the almost stopped growth of diatomcells started again to continue to grow, so nitrogen may also be induced factor ofeutrophication of water bodies. In previous studies, the study of the Three GorgesReservoir tributary Jialing River water quality is not much, and the system study of thenitrogen in the Jialing River water is much less, and there is almost no research of thenitrate reductase activity of the Jialing River water. Therefore, this article makes theJialing River as the research object. Through the continuous water sampling andmonitoring of the nitrogen of the Jialing River backwater area as well as the detection ofwater nitrate reductase activity, and analyzed respectively from the chemical speciationof nitrogen characteristics, nitrate reductase activity and the correlation among the basicwater quality indicators. In order to provide basic data for the early warning andemergency management of the Three Gorges Reservoir Area tributaries backwatereutrophication, to provide reference for the correlation research between the deep-waterlakes eutrophication and nitrate reductase activity. The research comes from theNational Natural Science Foundation Project: Mechanism of action of extracellularenzymes when confluence of river reservoir tributaries in the Riparian period "algalblooms". The main results obtained are as follows:①The variation of the total phosphorus content of the Jialing River backwaterarea is similar to the one of the Yangtze River water, and the total phosphorus content inthe wet period is significantly larger than other water period, which indicates thatphosphorus pollution along the Jialing River backwater area mainly is non-point sourcepollution; The total phosphorus content of the Jialing River backwater area is muchsmaller than the one of the intersection of two rivers along the Yangtze River Estuary, only38.4%of the Yangtze River.②The each form of nitrogen content of each sampling point of the Jialing Riverbackwater area showed no significant difference in water depths of0.2m and3.0m,indicating that the water tend to be evenly mixed from0.2m to3.0m. Along the way, thepercentage of ammonia decreased gradually, and the percentage of nitrate had almost nochange, and the percentage of total organic nitrogen gradually increased. The seasonalvariation of the total nitrogen content of the Jialing River backwater area was notsignificant, inferred that nitrogen nutrient level of the Jialing River backwater area wasinfluenced by agricultural non-point source pollution and point source pollutionconsiderably. The total nitrogen content of the Jialing River backwater area slightlylarger than the one of the Yangtze River water.③Through ANOVA of each sampling point of the Jialing River backwater area,found nitrate reductase activity of each sample point had no significant difference alongthe way, indicating that the nitrate reductase activity of the Jialing River backwater areahad small heterogeneity on the spatial distribution. The nitrate reductase activity had asignificant positive correlation with the total number of algae, indicating that when thenumber of algae increased, the nitrate reductase activity would increase too, which wasconsistent with the nitrate reductase activity of microcystis aeruginosa cultured in thelaboratory.④The total number of algae in water was significantly negatively correlated withflow velocity, indicating that low flow velocity was conducive to the growth of algae.NO2-N was significantly positively correlated with NO3-N, indicating that NO2-N andNO3-N had a similar variation rule. The total number of algae was significantlypositively correlated with the total nitrogen, and a significant negative correlation withNO3-N, and a significant negative correlation with the soluble orthophosphate, and asignificant positive correlation with dissolved oxygen, indicating that the increase of thetotal nitrogen content in water, would induce increasing the number of algae in thewater, and due to the algae’s own life activities, some portion of NO3-N would beabsorbed by the algae, leaving the lower content of NO3-N, on the other hand the algaewould release oxygen through photosynthesis, so that the dissolved oxygen in water hadan increase, and converted some part of NO3-N into organic nitrogen, so that the NO3-Ncontent decreased, and the total organic nitrogen increased, suggesting that the nitrogenform of the algae use mainly in water was NO3-N,and the phosphorus form of the algaeuse mainly in water was the soluble orthophosphate.