HK researchers to study ozone formation, PM2.5 in Greater Bay Area to check air pollution

26-May-2020 Intellasia | South China Morning Post | 6:02 AM Print This Post

Hong Kong’s researchers are planning to study two of the most persistent cross-boundary air pollutants in the Greater Bay Area.

The Environmental Protection Department is embarking on a three-year project to study ozone pollution in the Greater Bay Area, while an academic at Chinese University is tracking PM2.5 particulates that affect people with lung and heart problems.

Medical experts blame air pollution for causing up to 1,000 premature deaths every year in Hong Kong among vulnerable groups, such as the elderly. Increased tracking of pollutants will allow policymakers to identify ways to reduce air pollution to safe levels suggested by the World Health Organization.

Although several policies in recent years have succeeded in cutting down on most air pollutants in Hong Kong, ozone levels have nearly doubled over the past two decades.

The air-quality guidelines of WHO set the daily maximum eight-hour mean for ozone at 100 microgrammes per cubic metre, but Hong Kong’s own air-quality objectives, which set the concentration limits for pollutants and the number of times the levels can be exceeded in a year, uses WHO’s interim limit of 160 microgrammes per cubic metre, with nine exceedances allowed.

“Ozone is not just a Hong Kong problem, it is also becoming a challenge in Guangdong province,” a source at EPD said. “Since much of the ozone pollution we get here comes from the Pearl River Delta, we have been discussing various joint projects with the mainland authorities over the past few years.”

One of them is a three-year study to understand how ozone forms and spreads across the Greater Bay Area including Hong Kong, Macau and Guangdong.

Starting next month, air samples will be collected simultaneously from the air by helicopter, at ground level and over the sea, the source said. In the first year, samples will be collected within Hong Kong, but EPD hopes to expand this to the entire Pearl River Delta over the next two years.

Ozone is formed when nitrogen oxides emitted by vehicles mix with elements known as volatile organic compounds (VOCs), which can come from a variety of sources including paint, solvents and cosmetics. Sunlight and oxygen speed up the reaction, resulting in smog that can cause eye irritation and serious respiratory illness.

Once formed, ozone can be carried by wind from the Pearl River Delta to Hong Kong, particularly before a typhoon.

But the chemicals that contribute to the formation of ozone such as the VOCs and nitrogen oxides are also carried over, and can create a thick layer over up to 1 kilometre area in the air in Hong Kong and its surroundings.

“This is why we need to collect samples from the air, land and sea to better understand exactly what chemicals are included as the precursors to ozone,” the source said.

A related project aims to identify specific VOC sources that help create ozone, as this will allow the government to target reduction measures at the sources that contribute most to ozone formation and control air pollution more effectively.

A network of monitoring stations will be set up next year at 30 locations across Guangdong and eight in Hong Kong to collect air samples for analysis.

“We hope this study will help us target the exact sources of VOCs to cut down emissions,” the source said. “The point of all this is to have a scientific basis to formulate an emission control policy.”

Meanwhile, Professor Steve Yim Hung-lam, from Chinese University’s Department of Geography and Resource Management and the Stanley Ho Big Data Decision Analytics Research Centre, is tackling the PM2.5 problem.

He has already tested the efficacy of measuring PM2.5 using his new system in Hong Kong, and is planning to extend his research to the wider Pearl River Delta region.

Although the levels of the fine particulate have decreased due to policies such as upgrade of diesel engines to cleaner euro-VI versions, the average PM2.5 levels at street-level monitoring stations in Hong Kong last year far exceeded WHO’s limit of 10 microgrammes per cubic metre.

Yim said while ground-level pollution was well documented, PM2.5 pollution at high altitudes, which were more likely to come from regional sources, could not be effectively monitored with existing methods.

His system uses a laser beam to detect the density of PM2.5 and measure wind speed in areas up to 2 kilometres high.

It was installed in 2016 on the Chinese University campus in Sha Tin and the Hong Kong Observatory in Tsim Sha Tsui, and at Hung Shui Kiu in the western New Territories last month.

“The wind data showed a time lag from when the system first detects high pollution episodes in the outskirts of Hong Kong and when it reaches urban areas,” Yim said. “That means we can develop an early warning system so residents can plan their outdoor activities, while Hong Kong itself can lower its emissions to mitigate the effects of transboundary pollution.”

He began working with universities in the Greater Bay Area to expand the system across the region, but the progress was delayed by the Covid-19 pandemic this year.

“I hope air quality monitoring data from the system will help in planning public health policy in the region,” he said.


Category: Hong Kong

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