People hold umbrellas in the sun. Ozone has overtaken PM2.5 as the top pollutant of Beijing's air. (Photo/Chinanews.com)
(ECNS) – Ozone has overtaken PM2.5 as the top pollutant of Beijing's air, according to the municipal environmental monitoring center.
The center said it expected "moderate pollution" influenced by a high density of ozone, which began Monday, to last till Thursday, and the city's air quality may be deemed "good" by Friday.
According to data from the center, ozone density on Tuesday afternoon reached 270 micrograms per cubic meter (mcg/m³) in the city's six urban districts, and hit approximately 300 mcg/m³ in northern parts of the city.
On Monday afternoon, the urban districts' PM2.5 density was 106 mcg/m³, while ozone density reached 294 mcg/m³. The city's overall ozone density was well in excess of 250 mcg/m³ during the same period, and districts where PM2.5 was less of a nuisance all saw their ozone densities exceed 300 mcg/m³.
According to air quality standards, an eight-hour ozone density lower than 160 mcg/m³ signals "excellent" air quality, while 160-200 mcg/m³ means "good", and more than 200 mcg/m³ points to pollution.
Beijing is prone to ozone pollution from May to September, when temperatures are high, the center said.
Nitrogen oxides from car exhaust fumes can turn into ozone under the influence of sunlight, according to experts.
