Abstract:

Using the acid rain monitoring data of 1316 samples from the national basic meteorological stations in Urumqi from 1992 to 2018, the variation characteristics of the pH and K values in precipitation samples and their relationship with meteorological factors were analyzed.The results showed that in recent 27 years, the average annual pH value is 6.64.The acid rain frequency is only 4.56% and the precipitation in Urumqi is mainly neutral and alkaline.The average annual pH values show a slightly increasing trend and change abruptly in 1998.During the sampling period, the average annual K value is 90.40 μs·cm^-1 and shows a decreasing trend.The mutation occurs in 2001.The sequence of K values from high to low in the four seasons are opposite to the pH value, namely, winter, spring, autumn, and summer.When acid rain occurs in Urumqi, the northerly wind direction on the ground and at the upper layer is dominant.The pH value is positively correlated with wind speed, while the K value is negatively correlated with precipitation.In recent years, the implementation of "replacing coal with gas" in the heating season in Urumqi has greatly reduced the consumption of coal, resulting in a significant reduction of sulfur compounds such as SO₂ in the atmosphere.Besides, the municipal government has intensified its control of environmental pollution in recent years, and the frequency of acid rain has been significantly reduced compared with that before 2007.

Key words: Acid rain, K value, pH value, Meteorological factors