Ning YANG,Degang JI,Shuangjin LI

1.Department of Mathematics,College of Science,Agricultural University of Hebei,Baoding 071001,China;2.Department of Modern Science&Technology,Agricultural University of Hebei,Baoding 071001,China

Air quality problem has already become a hot social issue,related research work has been conducted by many researchers.Zhou Zhaoyuanet al.studied the correlation[1]between air quality and meteorological factors using rank correlation analysis and principal component analysis;Xia Yaronget al.researched the current situation of urban air quality[2]using grey variable weight cluster analysis method;in these studies,most researchers concerned the relationship between air quality and meteorological factors,but few people studied the correlation of air quality itself in Beijing-Tianjin-Hebei Region.In this paper,by analyzing real-time monitoring data of most monitoring points in Beijing-Tianjin-Hebei Region,and using Pearson correlation coefficient method[3],the correlation of air quality in Beijing-Tianjin-Hebei Region was determined to provide theoretical basis and technical support for the cooperative governance of air pollution in Beijing-Tianjin-Hebei Region.

Data Sources

The data for the study were from the monitoring data of China National Environmental Monitoring Centre[4],such six pollution indexes as SO2,NO2,CO,O3,PM10and PM2.5were selected,the details were according to the data of China National Environmental Monitoring Centre.

Data Pre-processing

To determine the relevancy among each pollutant of these cities,the comprehensive matrix of each monitoring point of the corresponding city must be got,the steps were as follows:

(1)Because of the missing value of each pollutant in the table,the substitution handling of linear interpolation method for the missing value should be carried out firstly.

(2)To eliminate the influence of dimension,respectively standardizing original data matrix using zscore()function in matlab must be done.

(3)Calling corrcoef()function in matlab,correlation coefficient matrix of standardized matrix must be obtained.

(4)Eigenvalue and eigenvector of correlation matrix should be determined.

(5)The maximum eigenvalue of each eigenvalue must be found,then the value should be normalized(that is,dividing each eigenvalue by their sum),the results were weighting coefficient of the data.

(6)The matrix after weighting coefficient step(1)was the comprehensive assessment matrix of the urban air quality.

Analysis on the Relevancy among Each Pollution Index of Beijing and Its Surrounding Cities

Bivariate correlation analysis was carried out for 53 monitoring points in such seven cities as Beijing,Baoding,Chengde,Zhangjiakou,Tianjin,Tangshan and Langfang using spss software,the results were as Table 1:

From Table 1,there was a strong and positive correlation in PM10and PM2.5indexes between Beijing and Baoding,and in SO2and PM10indexes between Beijing and Chengde.The correlation indexes of such four indexes as SO2,O3,PM10and PM2.5in Beijing and Tianjin were 0.541,0.540,0.557 and 0.560,respectively,indicating that air quality of Beijing and Tianjin had strong dependency.The correlation indexes of such three indexes as SO2,PM10and PM2.5in Beijing and Tangshanwere0.562,0.531and 0.541,respectively,indicating that at the significance level of 0.01,the two cities had strong correlation.The correlation indexes of such three indexes as SO2,PM10and PM2.5in Beijing and Langfang were 0.710,0.707 and 0.727,respectively,which indicated that the correlation of air quality of the two cities was very strong.

Based on the above data,it was not difficult to find that such three leading indexes as SO2,PM10and PM2.5had strong correlation in Beijing,Tianjin and main cities of Hebei.The main causes were as follows:

Firstly,Hebeihas long been known as"Yan Zhao Coal Bunker",it’s a big resourceful province in China.The data showed that,in 2012,coal consumption of Hebei accounted for 88.8%of its total energy consumption,and that of Beijing and Tianjin were 25.4%and 59.6%,respectively.Beijing,Tianjin and Hebei burn 23×106,70×106,27×107t standard coal each year,respectively.All these indicated that the dependence of Hebei Province to coal resources not only caused air pollution of Hebei,but also had certain influence on air quality of Beijing and Tianjin[5].

Secondly,by the end of 2013,Tianjin,Beijing and Hebei had 20×105,52×105and 50×105registered vehicles,respectively;Beijing had the most private cars,and exhaust gas emission was increasing day by day,in which nitric oxide and fine particulate matter in automobile exhaust aggravated air pollution,moreover,it had certain influence on air quality of Hebei and Tianjin.

In addition,Tianjin has well-developed industries,such energy-extensive consumption and top discharge industrial enterprises as steel,petrochemical enterprises,metallurgy and cement plants,etc.brought about rapid development of Chinese economy,but it also generated serious air pollution.By investigating,a large amount of pollutant discharge is one of the main reasons influencing air quality of Tianjin.Hebei Province is also a large steel province,in 2011,crude steel,pig iron and steel production were 1.65×108,1.54×108and 1.92×108t,respectively,which respectively accountedfor24.08%,24.52% and 21.82%of national production.Steelmain business income of the whole Hebei Province was 11 321.27×108Yuan in 2011,which occupied 27.80%of total industry revenue of the whole province;industrial added value was 2 444.73×108Yuan,which accounted for 23.26%of industrial added value of the whole province.Currently,iron and steel industry is the most important leading industry and the largest pillar industry in Hebei Province,most iron and steel enterprises of Hebei Province have high energy consumption and material consumption,and generate a large amount of pollutant discharge,moreover,the pollution is relatively serious,this is also one of the important reasons for the deterioration of Hebei air quality.

Table 1 Relevancy among each pollution index of Beijing and its surrounding cities

Conclusion

From the above analysis,air quality of Beijing-Tianjin-Hebei Region affects and restricts each other,so only the combination of the three can the air be cleaned,for this,the following suggestions were put forward:

(1)Beijing-Tianjin-Hebei Region should strive to explore green energy resources,increase the proportion of such renewable resources as wind energy,hydroenergy and solar energy,etc.in energy supply,and decrease the dependence on such high polluted energies as coal and petroleum,etc.

(2)We should advocate the development of public transport,reduce traffic flow,and call on people to save energy and reduce emission.We also can improve the discharge standard of vehicle pollutant,and reduce emission using technological means,for example,filter unit should be installed for automobile.

(3)The above measures were on the basis of science and technology,so it was hoped that Beijing and Tianjin can provide technical and staff support for Hebei,Beijing-Tianjin-Hebei Regionshouldenhancescienceand technology communication,and talent exchange,to lay a solid scientific basis for air pollution of Beijing-Tianjin-Hebei Region.

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