Analysis on change of precipitation pH and chemical characteristics of acid rain in Liaoning province (2007-2018)

Abstract

Acid rain, as one of the outputs of toxic and harmful chemicals from factories, is a serious environmental problem, especially in China, which has harmful ecological consequences and has a direct impact on vegetation and human health. Based on the data of acid rain observation station of Liaoning Meteorological Bureau from 2007 to 2018, the variation of precipitation pH and the distribution of acid rain in Liaoning Province in the past 12 years were analyzed. The result shows: First, the average pH value of annual precipitation in Liaoning Province is 5.55, which belongs to weak acid rain area. The frequency of acid rain is 12.56%, and the ratio of acid rain to total precipitation is 15.48%. More than 1/5 of the stations are located in the acid rain prone area, among which Dalian and Dandong are seriously polluted, being close to the grade of acid rain frequent area. Second, from 2007 to 2018, the precipitation pH in Liaoning Province fluctuated and increased year by year, with an average annual increase of 0.077 pH, and the pollution of acid rain decreased year by year; especially after 2014, Liaoning Province has exited from weak acid rain area, with its precipitation pH tending to be neutral year by year. Third, acid rain pollution in Liaoning Province is most serious in winter, followed by autumn and summer; in the first six years (2007-2012), the pollution in February was the most serious, and in the last six years (2013-2018), the pollution in December was the most serious, which was significantly worse than the previous six years. Fourth, more efforts have been made to control air pollution in all parts of the country, and the annual decrease in acid precursor emissions is the fundamental reason for the variation of precipitation pH and the improvement of acid rain pollution in Liaoning Province, while the precipitation pH and acid rain distribution in Liaoning Province are sensitive to the relevant environmental control measures taken by the state in recent years. However, the change of acid rain pollution reminds us to attach great importance to new pollution components and causes.