Thursday, January 22, 2015

APEC blue in China: air pollution data are censored after controversy on PM2.5 data released from US-Embassy in Beijing

The air pollution in Beijing and surrounding areas were supposed to be reduced by one third before the November 2014 APEC meeting, through a series of air pollution control measures.

"China will take action at the highest level to ensure air quality during the APEC meeting," said the vice president of the Chinese Academy of Environmental Sciences."It is expected that the discharge of pollutants in the Beijing-Tianjin-Hebei region will be reduced from 30 to 40 percent, and air quality will hopefully be further improved," he had said.

To prepare this APEC meeting scheduled from 8 to 10 Nov. 2014, Beijing had closed since June 2014  some of its plants, eliminated the old vehicles, used clean energy, and closed more than 300 polluting factories to reduce emissions.The use of car based on an even or odd number depending of the day was also planned to reduced by almost half the number of cars in the meeting.

Vice Premier Zhang Gaoli stated that the guarantee of the quality of the air for the APEC meeting was the "top priority".

Nevertheless the above picture is showing vehicles driving on Beijing's Fourth Ring Road amid heavy smog, on Oct 24, 2014 [Photo/Agencies]. 

The AQI issued on a daily basis by the various AQI data providers on the internet,  including MEP and US Embassy in the run up of APEC meeting were showing that the pollution was not controled and also extremely high. 

Government efforts to control smog ahead of the Nov. 5-11 Asia-Pacific Economic Cooperation events in Beijing had gained so much attention that the clearer skies programme got a nickname, “APEC blue”. 

China government after failing to clean the skies before APEC meeting tried to put the blame on the smog data providers and especially the US Embassy and decided to block all MEP AQI and Air pollution data publications. 

Why censoring the monthly publications of air quality and pollution data of the 190 major Chinese cities released from Jan. 2014?

As a consequence the monthly publications of air quality and pollution data of the 190 major Chinese cities (AQI derived from the concentration of the various pollutants: PM2.5, PM10 etc..) are censored by the China’s Ministry of Environment Pollution (MEP) since November 2014.

No air quality data was provided concerning the last two months of 2014, which will prohibit - if the MEP deadlock is maintained- to assess urban air quality for the 190 cities throughout 2014.

This interruption is very damaging to the complete information of the population on the quality of the air, in order to prevent the risks and prepare the provisions to be taken.

 What was really the situation of Beijing Air Pollution using the available data from MEP and US Embassy?

The air quality index (AQI) and associated pollutants concentration were obtained from the monthly average of the 190 main cities released progressively by MEP since 2013. No detailed data is provided concerning hourly and daily air pollutant apart from the number of days where AQI is above 100 or 50. As the PM2.5 is most of the time the main pollutant AQI is in clause relation with the PM2.5 level with AQI=135 when PM2.5=100 for instance (see my blog dated 11 Dec. 2013).

The air pollution data from US Embassy are obtained from the US Stateair feed 

They include the hourly PM2.5 only on 5 cities Beijing, Shanghai, Guangzhou, Chengdu and Shenyang.  These cities are among the biggest in PRC with Shanghai N°1 (22Mil), Beijing N°2 (19Mil), Guangzhou N°4 (11Mil), Chengdu N°8 (7Mil) and Shenyang N°14 (6Mil).  These cities are being reported by MEP since Nov. 2013 and we have a 12 months past information comparable to the US Embassy data.  

The following figure 1 is showing monthly PM2.5 concentration in Beijing as issued by MEP or US Embassy on the latest 12 months period available ( Nov. 2013 to Oct. 2014) plus an estimation of Nov. 2013 based on US Embassy.

The missing Nov 2014 PM2.5 of Beijing average is estimated from Nov. 2014 PM2.5 at US_Embassy by applying Nov 2013 correlation number (1.26) between both Nov 2013 concentrations.

Beijing monthly average increased by 19% compared to the value in November 2013. However, this situation is a major effort of the municipality to reduce pollution for the duration of the APEC meeting and this results necessarily more pollution than when the situation is normal!

Figure 1: Monthly PM2.5 concentration in Beijing as issued by MEP or US Embassy on Nov. 2013 to Oct. 2014 plus an estimation of Nov. 2013 based on US Embassy

Altogether, both data are extremely comparable because the US Embassy is a specific location in Beijing while the MEP monthly is averaged on the entire Beijing Municipality area which is around 17000km2 with a great variety of density between urban districts (30000 people/km2) - where is located the US Embassy- and suburbs  4000people/km2.

On the other hand the MEP does not provide information on hourly detailed pollution in specific sites where pollutants are measured. And the method used to determine the average value for the entire city is unknown: is-it an arithmetic mean or is it weighted by the density of the urban population?

What is the relationship between hourly, daily and monthly PM2.5 in Beijing?

The figure 2 below compares for PM2.5 concentration daily data issued by US Embassy with monthly MEP data. We see arge number of high daily values even for the month of November 2014 with 2 days with PM2.5 daily value >300µg/m3.

Figure 2:  Comparison of PM2.5 measurements daily  (US Embassy) or monthly values (MEP)

During the measuring period of 13 months or 395 days, there were all together 121 days or 31% of the total days where PM2.5 > 115µg/m3, which is about AQI> 150. We find comparable figures concerning MEP considering it is over a period of 12 months. However, we see that MEP needs  to specify the values of PM2.5 that are greater than 100, because there are lots of very high values