Estimation of non-point source pollution loading on Tongguan section of the Yellow River

According to the characteristics of rainfall and runoff in China's northern districts,the process of rainfall and runoff is divided into two stages in a annual:flood season and non-flood season based on the principle of the mean concentration method; meanwhile the pollution load in hyperconcentration of sediment flow will be divided into two parts:the dissolved pollution load in water and adsorbed pollution load in sediment; and the estimation model of non-point source pollution in sandy river is put forward.According to the measured water and sediment of Tongguan hydrological station in 1950-2005,combining the experiment determination water body with the sediment pollution concentration,three kinds different representatives of non-point source pollution load and the pollution load in 2006 are calculated in the Tongguan cross section.So they represent wet year(P=25%),normal year(P=50%) and dry year(P=75%) of Tongguan section.Results show that in Tongguan section the annal pollution load mostly occurs in flood season in the Yellow River,with the non-point source pollution as the main part in flood season.In the non-point source pollution load,the dissolved pollution load is taken as the main part in nitrate nitrogen and ammonia nitrogen,and the adsorbed pollution load as the main part in total nitrogen and total phos-phorus.The non-point source pollution of Tongguan section takes the proportion of the total as follows in wet year,nitrate nitrogen accounts for 63.09%,ammonia nitrogen 61.32%,total nitrogen 87.17% and total phosphorus 89.83%; in dry year,nitrate nitrogen accounts for 26.92%,ammonia nitrogen 24.62%,total nitrogen 67.60% and total phosphorus 71.73%.In 2006,the non-point source pollution load of the nitrate nitrogen,the ammonia nitrogen,the total nitrogen and the total phosphorus occupy 17%,14%,15% and 41% of the whole annual year proportion respectively.