Monitoring And Analysis Of Drinking Water Source Manganese Ion In Dafangyu Reservoir And Study On Its Pollution Mechanism

Recently, reservoirs and lakes have already or gradually been taken as a major source of the urban water supply in most cities of our country. but actively effect on the regulation of the natural environment. However, in summer, as the events of the reservoir, the migration of pore fluid and manganese to up-lap and the redox boundary layer moving up into the reservoir, a amount of manganese in the sediment releases to up lap and the concentration of the dissolved Mn²⁺?manganese?rises obviously. As a result, the concentration of manganese in water that acquired is very big. China's Drinking Water Health Standards?GB5749-2006? clearly defined that the con-centration of manganese in drinking water is no more than 0.1mg/L, different from some foreign countries where the limiting concentration is 0.05mg/L,such as Japan and America.In allusion to the phenomenon that manganese in surface drinking water sources is out of standard in most districts of our country, the subject in March 2015 to March 2016 from 4 sections and 34 sampling sites analyze the water quality and sediment of Dafangying rese-rvoir, on the basis of learning the hydrology,atmosphere and pollution survey of this area. Detecting the water quality parameter spatially and temporally, making a correlation analy-sis of inner pollution and water quality parameter,detecting the chemical and physical pro-perties of sediment, making a morphological analysis of sediment in the laboratory and studying the mechanism about migration and conversion of manganese by the method of experiment, and analyzing the effect of PH, temperature,dissolved oxygen, total phosp-horus, total nitrogen and other factors to the releasing of manganese in the bottom mud.Research indicates:1. The manganese concentration in bottom water reservoir exceeded where can reach 0.9mg / L, as the same in pore fluid where can reach 17.49 mg / L. In the horizontal direction, the reservoir manganese pollution degree changes seasonly,the degree in the wet season above the normal season and the dry season.2. In vertical direction, the temperature difference of the surface and central lake can reach 5?,water temperature stratification as a result. The bottom lake is anaerobic sate and the concentration of manganese and total phosphorus rise up by a large margin. The concentration of manganese from sediment is tens of times more than in the surface of the lake in summer. The Water-soluble mang-anese has a good correlation to dissolved oxygen and total phosphorus, correlation coeff-icient at r =-0.75727, r = 0.917.3.The proportion of the exchangeable, oxidizable and reducible form of manganese from the sediment is relatively large by BCR sequential extraction assay. The sediment exchangeable accounted for about 50% and it is easy to exchange foreign metal ions, after than, the manganese releases, so that the reservoir manganese content exceeded. The 60% of manganese in soil on the shore are in reduced state, When Dafangying reservoir in wet season, the average of accumulation index of manganese is 0.11, belonged to slight pollution, probably because a large amount of rain,pollutants discharged into the reservoir, resulting in runoff pollution and sediment manganese excessive pollution.4.In the experiment, sparing out manganese from mediment with different proportions of lake and deionized water. 100% lake water desorbed the most and fastest manganese in the sediment and the amount of desorption can reached 200 mg / Kg. Not the same as the former,the amount of desorption from 100% of deionized water is just 45 mg / Kg. Acidic and alkaline solutions are conducive to the release of sediment manganese, when pH = 4 is the amount of mang-anese in the sediment desorbed 400 mg / Kg or so, pH = 7.5 the amount of manganese in the sediments desorption 60 mg / Kg or so; pH = 9:00 desorbed manganese sediment in 110 mg / Kg or so. There are many high metal contents in water,such as Na⁺?Ca²⁺?Mg²⁺?and the Ca²⁺ will be more contributed to the releasing of sediment manganese at the same ionic strength.