The Yellow River is under the double pressure of pollution and disconnection. 66.7% of the rivers monitored were of class Ⅳ water quality. The main pollution indexes are ammonia nitrogen, volatile phenol, permanganate index and biochemical oxygen demand.
summarize
1. Pollution status
According to the Bulletin of China's Environmental conditions, air quality in cities in China was still in a relatively heavy level of pollution in 1997, while cities in the north were heavier than those in the south (see figure 3-1). The annual average concentration of sulfur dioxide is in the range of 3 ~ 248 μ g / m ~ (-3), and the national annual average is 66 μ g / m ~ (-3). More than half of the cities in the north and the top 1/3 cities in the south have an annual average of more than 60 micrograms per meter. The annual average of north city is 72 μ g / m ~ (-3) and that of southern city is 60 μ g / m ~ (3). The pollution of sulfur dioxide in cities of southwest high sulfur coal region represented by Yibin, Guiyang and Chongqing, and the cities of Shanxi, Shandong, Hebei, Liaoning, Inner Mongolia, Henan and Shaanxi provinces with large energy consumption in the north are more serious.
