Annual concentrations of certain major air pollutants have been slashed since a regional air quality monitoring partnership between Hong Kong and Guangdong began tracking levels in 2005, new results show.
But the yearly trend of improvement in regional air pollution was halted by a sharp rise in pollutants last year, prompting concern from green groups as to whether regional emissions targets set for 2015 would be met by the two sides.
Annual average concentrations of sulphur dioxide, nitrogen dioxide and respirable suspended particles of 10 microns or less (PM10) in the region fell a respective 62, 13 and 15 per cent from 2006 to 2012. However, ozone levels increased 12 per cent during that time, the report found.
The monitoring results were announced by the environmental protection departments of both Hong Kong and Guangdong yesterday as part of the Pearl River Delta Regional Air Quality Monitoring Network, which was established in 2005.
The network operates 16 ambient monitoring stations in Hong Kong and Guangdong.
Despite the drop in pollutants over the first eight years of the network, the results showed a deterioration of air quality late last year as nitrogen dioxide and PM10 concentrations rose 5 and 13 per cent respectively from 2012.
The report blamed "stronger solar radiation and lower wind speeds" in late 2013, which contributed to photochemical smog that was harder to disperse.
Kwong Sum-yin, chief executive of the Clean Air Network green group, said: "We are concerned that if this trend continues, both governments may not be able to reach the emission targets set out for 2015."
A pact was signed between the two sides in 2012 requiring Hong Kong to achieve reductions of 5 to 25 per cent for sulphur dioxide, small particles and volatile organic compounds by next year and to reduce nitrogen oxide emissions by 10 per cent.
She dismissed the meteorological explanations as an "excuse for worsening air quality" and called for the Hong Kong government to "be more progressive". Kwong said marine pollution emission was a major issue that needed to be tackled immediately.
Simon Ng Ka-wing, head of transport and sustainability research at the Civic Exchange, said a regional emissions control area to curb shipping pollution was the ideal solution.
The Environmental Protection Department said the two sides would continue to collaborate on the prevention and control of regional air pollution.