Status and source analysis of aluminum pollution in Xi''an section of the Weihe River
渭河西安市段铝污染状况及其来源分析

A preliminary study on aluminum pollution in the Xi'an section of the Weihe River was carried out. The results indicated that aluminum salt concentrations in the Weihe River ranged from 0.20 mg·L-1 to 0.66 mg·L-1,all of which exceed the water quality criteria of both the US and Canada and could do harm to human health. Although the flow rate of Weihe River increased from 36.4 m3·s-1 to 81.7 m3·s-1 after flowing through Xi'an,the aluminum concentration still rose to 0.43 mg·L-1 from the initial value of 0.29 mg·L-1; and the total amount of aluminum increased 2.4 times. During May 2008,a total of 66 tons of aluminum flowed into the Weihe River from Xi'an,of which one-fifth came from the Zaohe River. According to this investigation,the major cause of the increase of aluminum concentration in rivers was the flocculants used in wastewater treatment process,a great part of which were from paper mills. Since August 2008,stricter discharge standards for the paper making industry have been put into practice in China,so chemical flocculation plays an increasingly important role in wastewater treatment. All plants investigated use aluminum salts as flocculants,and this is the main reason why the aluminum concentration rose in the surface waters.