Analysis of air quality in Shenyang

Analysis of air quality in Shenyang

邹欣怡 Zou Xinyi

南京信息工程大学 The NUIST Reading Academy The University of Information, Science & Technology

Abstract

This article mainly analyzed the air quality index in Shenyang from 2018 to 2020. Additionally, the index of various pollutants (PM2.5, PM10, O3, NO2, SO2 and CO) had some huge changes in different seasons because of natural and human factors. Meanwhile, the local sources and causes of the main pollutants were introduced in Shenyang. Lastly, Shenyang's geographical location and human history also had negative effects on its air quality. For example, Shenyang developed heavy industry would lead to more air pollutants.

According to the data from the website about AQI_[1], the daily index of the major pollutants in Shenyang was monitored, which included PM2.5, PM10, O3, NO2, SO2 and CO. Based on the data of the past three years, the main pollutants in Shenyang were PM2.5, PM10 and O3. NO2, CO and SO2 had little effect on AQI.

The air quality of Shenyang Environment in 2020 was analyzed in detail. The excellent and good days were 311 days, and the not excellent days were 54 days.

The number of days with PM2.5 as the primary pollutant concentrated in winter and spring. It reached the peak from January to February. The highest value was 316 in January. The seasonal influence on PM2.5 index of Shenyang was obvious. During the summer sampling period, the atmospheric diffusion conditions were good, the mass concentrations of EC and OC decreased, so the PM2.5 index was low. In the contrast, during the winter sampling period, the PM2.5 index was high. Because Shenyang's winter was cold, people needed coal-fired heating，which would produce a lot of air pollutants. What’s the worse, there would be frequent static and stable weather situation in winter, adverse atmospheric diffusion conditions. Meteorological factors and air pollutant emission resulted in more days of PM2.5 as the primary pollutant.

The number of days with PM10 as the primary pollutant were in all seasons except summer, especially in January and April. It peaked at 280 in January. The mass concentrations of organic carbon and elemental carbon in PM10 in autumn and winter were higher than those in spring and summer. In addition, there were 16 kinds of Polycyclic aromatic hydrocarbons (PAHs) in PM10 of Shenyang. The proportion of PAHs with different number of rings to the total concentration was 4 rings > 5 rings > 6 rings > 3 rings > 2 rings. The results showed that the combustion of coal and wood and a small amount of petroleum volatilization were the main sources of PAHs in PM10 in Shenyang._[2]

The main pollutants in Shenyang

Volatile organic compounds (VOCs-- alkanes, aromatics, etc.) and particulate matter (PM2.5, PM10, etc.) are the main pollutants in Shenyang that cause the decline of air quality and do harm to human health.

There are 61 kinds of volatile organic compounds (VOCs) in the air of Shenyang, which are mainly alkanes, olefins, aromatics, halogenated hydrocarbons and alkynes, accounting for 37.7%, 14.8%, 26.2%, 19.7% and 1.6% respectively, among which alkanes are the highest. Alkanes and aromatics account for 63.9% of the total volatile organic compounds (VOCs) in Shenyang._[3] As the experimental data showed, the peak concentration of alkanes and alkenes has a strong correlation with human activities and transportation. The concentration of toluene in the morning and evening is similar except that of benzene in the daytime. The concentration of xylene and o-xylene in the evening is higher than that in the morning. This situation may be caused by pollutants from factories that work overtime at night in Shenyang. Thus, the pollutants produced by human transportation and industrial production can reduce the air quality.

PM2.5 and PM10 also have great influence on air quality. Compared with different seasons, the concentration of two kinds of particle size is the highest in spring and the lowest in summer.

The mass concentration of PM2.5 and its chemical components (water-soluble ions, inorganic elements and carbonaceous group) are determined. Water soluble ions in PM2.5 mainly come from soil and construction dust, biomass and fossil fuel combustion and industrial production emissions. Inorganic elements mainly come from the crust surface and soil rock weathering, industrial production, transportation and coal combustion emissions. Carbon components mainly come from gasoline vehicle exhaust and coal combustion emissions. The Positive Matrix Factor(PMF)model shows that the contribution ratios of coal combustion, secondary aerosol, industrial emissions, fugitive dust and traffic emissions in PM2.5 were 33.37%、27.27%、16.68%、11.49% and 11.19%._[4] Moreover, there are obvious seasonal variation characteristics of PM10 concentration in Shenyang. There is a certain relationship with the meteorological factors such as precipitation, wind force and wind direction, especially in winter and spring._[5] With the development of Shenyang, the daily PM10 mass concentration is affected by the increase of urban population, number of motor vehicles and urban temperature.

Motor vehicle exhaust results in higher concentration of fine particles. Coal burning and road dust lead to high concentration of coarse particles. The concentration of particles is positively correlated with temperature, while the concentration of particles is negative correlation with humidity. The correlation with wind speed is not obvious.

Geographical features

Shenyang is in the south of Northeast China and the middle of Liaoning Province. (Coordinates 41.19769,122.41674,43.04030,123.80854) Connecting Liaodong Peninsula in the South and Changbai Mountain in the north, it is an important junction between Bohai rim and Northeast China. Shenyang is the largest central city in Northeast China because of its unique geographical location. It is one of the bases of heavy industry in China. Therefore, the air pollution caused by industrialization has a bad impact on air quality.

Conclusion

In recent three years, the air quality index of Shenyang has decreased slightly. However, the highest value of PM2.5 is increasing year by year. With the urbanization process of Shenyang and the increase of population, human activities aggravate the air pollution, especially PM2.5. Additionally, the main pollutants are particulate matter (PM) and volatile organic compounds (VOCs) in Shenyang. Finally, due to the unique geographical advantages and cultural history of Shenyang, the air pollution caused by heavy industrialization has a bad impact on air quality.

Reference

1. The AQI data online, http://aqicn.org/data-platform/register/

2. Li Jing, Qu Jian, Li Zhe, Wang Shuai, Zhu Linlin, Pollution Characteristics and Sources Analysis of Polycyclic Aromatic Hydrocarbons(PAHs)in PM 10 in Shenyang City, 12.2019, Vol.44 No. 2,128-132