Study On The Migration Of Typical Pollutants During Freezing And Melting

Surface water is one of the important freshwater resources and plays an important role in social development.In recent years,due to the development of society and the influence of human activities,surface water pollution has become more and more serious.It has aroused widespread concern and carried out a lot of research.However,most of these studies have been carried out in the non-glacial period of surface water,and a small amount of research on the ice period of surface water has also focused on outdoor.This paper takes typical pollutants as the research object.Through outdoor sampling analysis and indoor simulation experiments,the migration laws of pollutants in the process of water icing and melting were analyzed,and the ice body thickness,ice temperature and pollutant concentration to ammonia nitrogen,nitrate,phosphate,and iron were studied.The following conclusions are drawn:1.A set of instruments suitable for indoor experiments are developed to simulate the freezing process,including ice simulator,resistance wire thickness meter and self-made ice thawing device,which can be used as reference for indoor simulation ice forming experiment.2.Phosphate,nitrate,ammonia nitrogen,total nitrogen,iron,sulfate,manganese and other pollutants migrate from ice body to water during natural freezing process.The mobility of pollutants was in the order of nitrate nitrogen > ammonia nitrogen > total nitrogen > phosphate > manganese > sulfate > iron,among which nitrogen,phosphate and other nutrient elements were greatly affected by freezing concentration,iron,manganese,manganese,etc.The melting experiment of natural ice body shows that the release of pollutants from ice body is basically the same,that is,a large number of pollutants are released rapidly in the early stage of ice melting.Then the amount released was small and stable.3.With the increase of ice thickness in the indoor frozen natural water body,the concentration of various pollutants in the water is constantly increasing.The transport of pollutants in the ice body is higher than that in the natural condition during the indoor simulation of ice formation.The release of pollutants from the ice phase is basically consistent between the indoor frozen natural water body and the outdoor frozen natural water body when the ice body melts.And the frozen ice body in the early stage of melting ice is more conducive to the release of pollutants.4.The water samples containing ammonia nitrogen,nitrate,phosphate,iron,and manganese were simulated under the conditions of different ice thickness,initial concentration and ambient temperature.With the increase of ice thickness,the concentration of ammonia nitrogen,nitrate,phosphate,iron and manganese in the ice body decreases continuously;the concentration of ammonia nitrogen,nitrate,phosphate,iron and manganese in the water before freezing increases when the thickness and temperature are constant.The concentration of pollutants in each ice layer increased after freezing,so the worse the water quality of raw water,the higher the content of ice body after freezing;at a certain thickness and concentration,with the decrease of freezing temperature,The transport of ammonia,nitrate,phosphate,iron and manganese decreased during freezing concentration.At a certain freezing temperature,the thicker the ice body,the higher the amount of ammonia nitrogen,nitrate,phosphate,iron and manganese released during the initial melting of the ice body;when the thickness of the ice body is constant,the lower the freezing temperature,the discharge of ammonia nitrogen at the initial melting stage of the ice body.The concentrations of nitrate,phosphate,iron and manganese decreased,but the ice thickness and freezing temperature had no effect on the overall trend of pollutant release curve.