In 2011, the city's urban ambient air quality maintained a good condition. There were 336 days with the urban ambient air pollution index less than 100, 2 days more than last year and accounting for 92.1% of the total number of full-year days. And the precipitation PH value has been greatly improved. The frequency of acid rain last year fell down 15 percentage points over the previous year. In addition, the quality of urban water environment was essentially flat with last year, and water quality compliance rate of urban drinking water source was 100%.