Is Beijing the most polluted city within China?

Despite presumptions being made due to its capital city status and location of this year’s Olympics, Beijing is in fact not the most polluted city within China. Regardless of its high level of air pollutants, mean annual TSP in Baldasano et al 2003 paper in The science of the total environment, indicate that Lanzhou in North-west china is actually the city with the highest air pollution of 732 µg/m3, 355 µg/m3 higher than Beijing. Xia et al 2008 in Atmospheric environment, states that as with Beijing and other cities within China, air pollution is a result of rapid industrialisation and urban growth, with factories producing petroleum, undergoing chemical combination and machine building.


A graph of the mean annual TSP in the world’s highest polluted cities (Baldasano et al 2003).


So how come if the processes in which pollutants are added to the atmosphere are the same, Lanzhou has higher air pollution? Is it due to the population size? No, as Lanzhou has a population below 2 million compared to Beijing’s population of over 10 million. Is it due to the fuel burned within the factories? In some ways it is as a different type of coal is used which contains high levels of sulphur which adds to environmental impacts, but this is not the main contributor to the high levels of air pollution. So what is the main contributor?

The main contributor to the high air pollution is its geographic location. Numerous scientists including Chu et al 2008 in Environment international, Chu et al 2008 in Environment international and Xia et al 2008 in Atmospheric environment attribute the high levels of air pollution to Lanzhou’s geographic location. Xia et al 2008 attributes the high levels to Lanzhou’s trough shaped topography and Chu et al 2008 in Environment international develop this idea by stating that the topographic characteristics blocks the air streams which due to large frictional forces encourage weak winds which inhibit the diffusion and dispersion of the pollutants. Additionally its location gives rise to large variations in temperature diurnally and seasonally, which adds to the air pollution problem.

As the geographic location of Lanzhou cannot be altered, it appears that little can be done to alter the increased impacts of the areas urban lifestyle apart from stopping or significantly decreasing the industrial activities. This assumption is just that, as Chu et al 2008 in Environment international states how the local government has encouraged afforestation which generates downward mountain winds in winter or at night which weakens the mountain valley circulation and destabilises the atmosphere leading to enhancing the diffusion rate of pollutants.

It can therefore be seen that the industrial activity and population size is a small contributing factor when compared to geographic location, and in some respect China is lucky that its capital city is not situated in a geographic location like Lanzhou, otherwise air pollution would be an even bigger environmental problem.

References:
Baldasano. J. M., Valera. E., and Jimenez. P.(2003) Air quality data from large cities. The science of the Total Environment. 307.141-165.

Chu. P. C., Chen. Y., and Shihua. L. (2008) Afforestation for reduction of NOx concentrations in Lanzhou, China. Environment International. doi:10.1016/j.envint.2007.12.014

Chu. P. C., Chen. Y., Shihua. L., Zhenchao. L., and Yaqiong. L. (2008) Particulate air pollution in Lanzhou, China. Environment International. doi:10.1016/j.envint.2007.12.013.

Xia. D. S., Chen. F. H., Bloemendal. J., Liu. X.M., Yu. Y., and Yang. L. P. (2008) Magnetic properties of urban dustfall in Lanzhou, China, and its environmental implications. Atmospheric environment. 42. 2198-2207.