With vehicles top source of smog-causing pollutant, study suggests halving Pearl River Delta traffic

PUBLISHED : Monday, 14 July, 2014, 4:25am
UPDATED : Monday, 14 July, 2014, 8:13am

Reducing traffic in the Pearl River Delta by half could be one of the most effective means of combatting regional smog, according to a cross-border air pollution study.

The study highlighted traffic as the major source of a smoginducing pollutant, volatile organic compounds (VOCs), which can react with nitrogen oxides (NOx) generated from other combustion sources to form ozone.

It concluded traffic-related emissions accounted for 50 per cent of the ambient VOC levels in the region, with petrol exhausts being the biggest single contributor. This conclusion was based on modelling results.

The summary of the HK$10 million study on the formation of photochemical smog in the region did not elaborate on how traffic could be halved. It was funded by Hong Kong's Environmental Protection Department.

The summary also reported that the share of industrial emissions was about 25 per cent.

Ozone is a major component of smog that not only reduces visibility but also threatens human health when exposure is prolonged and high.

Since 2005, ozone levels have been measured along with three other pollutants by a network of 16 monitoring stations, including three in Hong Kong.

Between 2006 and 2013, the ozone reading rose by up to 38 per cent. It was the only pollutant to record an increase.

The latest study showed that while reducing traffic in the region by half would be the most effective means of curbing ozone, cutting VOC emissions from traffic by half could achieve the same result.

The study also found that controlling ozone required careful advance planning, as it was not a straightforward exercise to reduce VOC or NOx emissions.

It found that sometimes controls at one place could backfire by significantly increasing ozone in other areas.

The report also proposed strengthening the monitoring network and setting up photochemical monitoring stations.