Occurrence,Transport And Risk Assessment Of Nitrogen And Phosphorus In Baiyangdian Sediment

Baiyangdian,known as "The Kidney of North China",is the largest freshwater lake in North China.The nitrogen phosphorus in the water body comes from the release of the external input and the endogenous sediment,the white ocean is more shallow lake,and the release of nitrogen phosphorus in the bottom mud has a greater influence on the water body.The release of nitrogen phosphorus in Baiyangdian sediments can provide a reliable basis for the treatment of Baiyangdian water environment and the treatment of sediment.This topic mainly through indoor simulation test,simulation of different areas of Baiyangdian,including free water surface,rice fields,reed ponds and lotus ponds in the upper water body with nutrient salt content,temperature value,disturbance degree of the size,to explore the release process of nitrogen and phosphorus nutrients in baiyang sediment and the change of nitrogen and phosphorus concentration in the upper water body.And the rice fields,lud san,lotus pond,free water surface of different areas of the comparison,is conducive to the targeted management of Baiyangdian.The TN concentration in the overlying water of Baiyangdian was high between October and december,the concentration was about 1.3～2.6 mg/L,and the TP concentration varied between 0.4 and 0.8 mg/L.The TP concentration was higherbetween June and August,and the composition of sediment particles in lotus pond was smaller than that in other regions.The contents of organic matter,moisture content,total nitrogen,total phosphorus,alkali-hydrolyzed nitrogen and available phosphorus in lotus pond are much higher than those in other regions.Comprehensive pollution index method was used to evaluate the pollution degree of nutrient salt in Baiyangdian sediments.The nitrogen and phosphorus release in sediment is positively correlated with temperature and disturbance,inversely proportional to the nutrient content.The effects of temperature on phosphorus release were as follows: lotus pond > free water surface > reed pond > paddy field,The ratio is about 1.8:1.4:1.3:1.The influence of temperature TN various regions: lotus pond > free water surface > paddy field,Reed pond,The ratio is about 2.4:1.9:1.4:1.The effect of disturbance on phosphorus in various regions: lotus pond > free water surface > Reed pond > paddy field,The ratio is about 1.7:1.4:1.2:1;The Influence of Disturbance on Nitrogen Release > Free Water > Paddy > Reed Pond The ratio is about 1.5:1.2:1.1:1;Nutrient salt content has little effect on nitrogen release.About 1:1.07:1.13 in different overlying water,A large proportion of phosphorus release in different overlying water was about V:IV:III=1:1.27:1.31.The Pb concentration in paddy sediments of Baiyangdian Lake was 138 mg/Kg、As 36.3 mg/Kg,and the Cd concentration in lotus pond sediments was 0.545 mg/Kg which far exceeded the background concentration.The Cd of Baiyangdian is the main pollution element,the rice field Pb cause moderate pollution,the Ni element is not polluted except in the lotus pond,and the Cr、Zn element is not polluted in all regions.Temperature and disturbance degree have no obvious rule on the proportion of heavy metals in different functional areas,and the change of Cu concentration is obviously affected by temperature.Degree of disturbance Cu、A s release has a greater impact.