Investigation of eutrophication of Taiyuan section of Fenhe river in dry season

Objective To know eutrophic conditon of Taiyuan section of Fenhe river.Methods Five sampling sections were chosen.They were the exit of Fenhe reservoir,Zhaishang hydrologic station,Shengli bridge,the second dam of Qingxu.The eutrophic level was evaluated through measuring water temperature,pH,chromaticity,total nitrogen(TN)concentration,total phosphorus(TP)concentration,chlorophyll-a level(Chla),total amount of the algal cells and water tropic state index (TSI).Results TP concentration of the exit of Fenhe river and Shengli bridge(0.028,0.041mg/L)was lower than Ⅲ TP standard of GB3838-2002《Surface Water Environment Quality Standard》(0.2 mg/L).TP concentration of Zhaishang hydrologic station,Xiaodian bridge and the second dam of Qingxu(1.236,2.552,0.748 mg/L)and TN concentration of all five sections(5.017,15.177,5.262,20.842,20.484 mg/L)were obviously exceeding the Vstandard of GB3838-2002.Chla level of all sections(mean 1.174μg/L)did not exceed the Ⅲ standard of GHZB I-1999《Surface Water Environment Quality Standard》(10μg/L).Total amount of algal cells was more than 1×106/L in the dry season,TSI mean value of Taiyuan section of Fenhe river in the dry season was 57.68.Conclusion Taiyuan section of Fenhe river was in mesotropher transition to light eutropher.