An Empirical Mode Decomposition for Establishing Spatiotemporal Air Quality Trends in Shandong Province, China

Huisheng Wu,Yaping Zhang,Maogui Hu,Yuan Han

doi:10.3390/su132212901

Abstract

Air pollution is a serious problem in China, and the government has taken a series of steps to solve it. However, it is still u2nclear how the situation has improved after years of atmospheric pollution control. Shandong Province, which has the second largest population and the highest coal consumption in China, was chosen to analyze the spatiotemporal air quality trends. We obtained daily air quality index (AQI) values from 91 stations in the province from 1 January 2014, to 31 December 2019, based on an adaptive data analysis method, empirical mode decomposition (EMD). The distribution of AQI in Shandong Province was heterogeneous at both spatial and temporal scales. All the stations could be divided into four clusters whose AQI trends decreased from 75 to 53, 95 to 68, 128 to 82, and 148 to 82, respectively. The overall trend of pollution became more serious from east to west in the province. The AQI is the largest in winter, followed by spring and autumn, and the smallest index occurs in summer. There are four types of annual trends of the AQI of each city. The overall downward trend indicates that the air quality of each city was improving annually.

Highlights

Frequent air pollution episodes have attracted the attention of the whole of China in recent years
The main pollutants involved in air quality assessment include fine particles (PM2.5 ), coarse particulate matter (PM10 ), sulfur dioxide (SO2 ), nitrogen dioxide (NO2 ), ozone (O3 ), and carbon monoxide (CO)
Comparison of the median and mean air quality index (AQI) values showed that the data were slightly rightskewed for the 312 weeks

Summary

Introduction

Frequent air pollution episodes have attracted the attention of the whole of China in recent years. Problems related to air pollution are increasing in many developing countries due to urbanization, industrial development, increasing use of cars, etc. Several studies analyzed the change in separate pollutants in China in recent years [8,9]. After years of air pollution control, concern remains regarding how much the general air pollution situation has improved in the country. Air quality can be evaluated both by using air quality models [10,11] and by ground-based monitoring data at different scales. The air quality index (AQI) is an important comprehensive indicator used to measure air quality. By discovering the spatial and temporal distributions of AQI values, effective measures can be implemented to reduce air pollution

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Discussion

Conclusion