Studies On Pollutant Distribution In Ice-water System Of Ulansuhai Lake

Ulansuhai Lake is a typical eutrophic lake issituated in Hetao irrigation region of semi-arid area in north part of China.The The water quality type of the lake is [ClJNalll and it’s frozen period is 4-6 months.Recently, heavy metals pollution in the lake has been received wide attention.The heavy metals(Cu、Fe、Mn、Zn、Pb、Cd、Cr、Hg、As),TN,TP,Na+ and Cl" are studied.A combination of method of field monitoring and laboratory simulation test is used to study the distribution and migration of different pollutants in Ice-water mediumt during the ice season and then to calculate bond energy useing first-principle.The results are shown below:The pollutants of Ulansuhai Lake is moved from ice to water under the ice during the process of freezing.Distribution tendency of pollutants is first decreased then increased;Freezing has the effect of cleaning water,different pollutants has different partition coefficient K. For heavy metals,partition coefficient of cadmium is the largest and chromium and arsenic is smaller; K of Total nitrogen is less than the total phosphorus,but both of them are bigger than the K of heavy metals, partition coefficient of Na+ and Cl- is smallest.Laboratory freezing experiments were performed to investigate the migration of pollutant(Cu,Cr,Hg,As,TN,TP,Na+,Cl’)in Ulansuhai Lake water during ice season. Differences among single factors,including initial concentration and freezing temperature were tested.The results showed that concentrations in ice increased with enhancing initial concentration and decreased with enhancing freezing temperature.The concentration in various segments of the ice phase was in the order of:top<middle<bottom.The value of the initial concentration is higher,the lower partition coefficient K of heavy metal,TN and TP,and higher K of Na+ and Cl.When significant level of hypothesis testing(a)is 0.05,the significant effected distribution of pollutant with different initial concentration and freezing temperature are tested.Initial concentration was 10mg/l,different solution(Cu、Fe、Mn、Zn、Pb、Cd、 Cr、Hg、As)freezing respectively at-25℃or-15℃:The concentration in various Material types of the ice phase was in the order of:Fe>Cu>Mn>Zn>As>Cd>Pb>Hg>Cr.The VASP model is used to calculated bond energy between ice and pollutant.Correlation analysis(a=0.05)showed that at-25℃(-15℃),there was significant linear correlation between the Concentration and the bond energy.