Pearl River Delta air quality improves but ozone levels rise, report shows
While pollutant counts fall in Pearl River Delta, concentration of harmful gas increases: report
Air quality over the Pearl River Delta region improved last year as levels of three major pollutants dipped - but one worrying pattern was a worsening of the harmful ozone pollutant, an official report showed.
The average annual concentration of sulphur dioxide, nitrogen dioxide and breathable suspended particulates recorded in 16 monitoring stations in the region over Hong Kong and Guangdong declined by 11 per cent, 8 per cent and 11 per cent respectively when compared with 2013.
While this was good news, the report noted that the increase of ozone gas showed that photochemical smog pollution in the region had yet to improve.
A green group and an expert on air pollution said while the report showed "positive signs", air quality in the region was still below the World Health Organisation's standard.
The average concentration of ozone, formed by photochemical reaction of oxygen, nitrogen oxides and volatile organic compounds in the air under sunlight, was 57 micrograms per cubic metre last year, up 5.6 per cent from 2013. The level stayed unchanged in 2012 and 2013.
"The ozone could have come from somewhere farther, and got blown to the Pearl River Delta region," said Professor Lau Kai-hon, of the University of Science and Technology's environment division. He added that weather conditions, such as light intensity, would also affect the ozone concentration.