Why Beijing's Sky Is Always Grey?
Beijing, the capital city of China, suffers from some of the worst air pollution worldwide. Recent years, grey sky appears increasingly frequent, especially in autumn and winter.
The map above cited from berkeleyearth.org shows a real-time air pollution of China. Beijing's air quality was "very unhealthy" at 6:00 (UTC) on Nov. 5th, 2017.
"Combating severe air pollution needs to be made our most important job right now. [However] the air condition this autumn and winter does not allow for any optimism.”
--Ministry of Environmental Protection of China
Here comes the question: What is the source of this air pollution?
How to measure air quality?
Before analyzing the contributors to Beijing’s air pollution, Let's identify the measurements of air quality.
AQI Standard (cited from Wikipedia)
Air pollution is measured by the Air Quality Index (AQI), which scales pollution levels from 0 to 500 and assigns a color to different number levels to measure how hazardous the air quality is on any given day. Levels of 100 or below are known as “Blue Sky Days”, when smog is not easily visible.
Air pollution in Beijing in 2016 measured by AQI (cited from Wikipedia)
What is the source of this air pollution?
The causes of Beijing’s widespread air pollution can be attributed to a number of factors: a surge in the number of motorized vehicles, population growth, unreasonable energy structure, and influence of air pollution in neighboring regions due to topography and weather conditions.
Distribution of Air Pollutant
Among the air pollutants of Beijing, the most primary ones are pollution from surrounding area and vehicle emissions, followed by the coal burning. Industrial emissions and dust pollution rank the fourth, while the rural straw burning takes up 4% of the air pollution in Beijing.
Population growth
Population growth in Beijing is one of the contributors to extensive pollution. Beijing’s resident population has swelled from nearly 18 million to more than 21 million in just 7 years. Among the increment of 5 million, the growth of urban population contributes almost 75%.
More residents mean more resources need to be served to support people's life. For instance, with more immigrants residing in Beijing, private cars, central heating in winter and other demands will certainly increase.
Car ownership growth
With rapid economic growth and amplified wealth, individuals are more capable of affording motor vehicles. The number of private vehicles on Beijing’s roads has surged from less than 3 million to nearly 5 million in 6 years.
The four most dangerous pollutants that cars emit include: sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and particulate matter (e.g. PM10). The increasing number of vehicles year by year results in more these hazardous pollutants that contribute to frequent "grey skies" and do harm to people's health.
Energy structure
Fossil fuel, including coal, petroleum and natural gas, took up more than 70% of energy consumption of Beijing.
From 2011-2015, however,there was an obvious decline of coal and petroleum consumption, while natural gas and electricity consumption steadily increase.
Even though the energy structure is changing over years, the coal that produces large amount of pollutants, is still in a predominant position, no matter in industrial production or household use.
“In northern China, air pollution from the burning of fossil fuels, principal coal, is causing people to die on average 5.5 years sooner than they otherwise might.”
--Tim Flannery, Atmosphere of Hope, 2015.
Surrounding areas
Geographical distribution of air pollutants
Beijing's air pollution is formed from the inside to the outside. We can divide the neighboring regions into three layers.
The inner layer—Beijing itself.
The outer layer—cities in Hebei province that surround Beijing.
The outermost layer—Inner Mongolia and Shanxi province, which are typically burdened with heavy industrial structures with heavy-polluting industries such as coal, electricity, chemicals and non-ferrous metals.
Three layers of circles around Beijing
Take coal-burning factories for an example. The factories are located on the outskirts of Beijing and the nearby cities of Hebei, Shanxi and Inner Mongolia, which rely on outdated and inefficient technologies. With the help of strong wind, the hazardous emissions from these heavily polluted areas can easily diffuse to Beijing.
Epilogue
The heavy air pollution in Beijing is therefore depicted as "initiated by economic growth, mainly from vehicle emissions and coal burning, and intensified by the pollutants from neighboring regions originated from heavily polluted factories."
Hopefully, conditions are changing. Hope that "blue sky" will be a normalcy of Beijing in the near future.
