Summary: John Lee, Antonio Da Roza

Originally: Alexis Lau, Andrew Lo, Joe Gray, Zibing Yuan, Christine Loh (published by Civic Exchange) Img001

Date: 8/8/10

Originally: March 2007

No matter what method of measurement is used, air quality in Hong Kong and the Pearl River Delta has deteriorated over the past 20 years, resulting in an increase in the number of hazy days in Hong Kong. This leads to questions about where the air pollution is coming from and what can be done about it.

Two traditional approaches – based on total emissions in terms of tonnage and receptor source apportionment in terms of mass concentration, are first summarized, before a new approach, giving a time-based perspective, is introduced.

Data from 2006 shows that regional sources are the primary influence on Hong Kong’s air only 36% of the time. By contrast, local sources are the crucial factor 53% of the time – meaning that much more can be done locally to improve air quality and therefore public health.

Scientific approaches to emissions measurement (total emission method and source apportionment method)

A total emission method is useful on a regional scale to depict volumes in terms of tonnage emitted from different sources. Based on 1997 data, analysis results showed that the Pearl River Delta Economic Zone contributed 88% of volatile organic compounds, 95% of respirable suspended particles (PM10), 80% of nitrogen oxides (NOx) and 87% of sulphur dioxide (SO2) to the entire region in the base year of 1997. It is difficult, however, to give a quantitative estimate on the region’s contribution to pollution levels in the HKSAR, though one may interpret from these large proportions that regional impact may be greater than local contributions of the four pollutants in the HKSAR.

The source apportionment method relies on data that shows the chemical composition of particulates measured at monitoring stations. Based on a study of data collected from 1998 to 2002, it was concluded that in respect of mass concentration, the PRDEZ accounted for approximately 60% of the pollution level in annual average terms, but this proportion rises to 70% in the wintertime.

Time-based apportionment method (number of days)

Earlier studies have shown the average concentrations for most pollutants in Hong Kong are higher in winter. The time-based apportionment method identified for each day in 2006 the likely source or region that influenced the HKSAR’s air quality. One drawback of this method is that some of Hong Kong’s local pollution sources such as the power stations may have their emissions transported into the greater Pearl River Delta area, mixed in the regional land-sea breeze and circulated with regional pollutants into Hong Kong’s air shed, which would then be counted as a day where regional sources were identified as the influence on air quality.

This method shows that not only do regional sources affect Hong Kong’s air pollution in winter, but local sources play the biggest role in summer. Regional sources are the primary influence on Hong Kong’s air quality on 132 days of the year, whilst local sources are the crucial factor on 192 days of the year. The conclusion that can be drawn is that Hong Kong can control the source of its air pollution problem more often than not. However, it is also clear that air quality is worse when influenced by the Pearl River Delta, and thus Hong Kong and its neighbors must continue to work together to reduce overall regional pollution.

General policy recommendations

At the highest level of government, there must urgently be well-coordinated, concurrent action. These actions should target the major emission sources, including power generation, land transportation, marine transportation and logistics sectors.

Essential policy tools include the adoption and enforcement of World Health Organisation Air Quality Guidelines and the devising of a comprehensive energy policy. A cross-cutting energy policy should include achievement of energy efficiency by recalibrating the Schemes of Control to reward efficiency, lowering emissions from power generation by changing fuel mix (by using a higher proportion of natural gas) and considering what energy security risks there are for Hong Kong and how they may be dealt with in the medium and longer-term future.

Traffic management policies should include the phasing out of vehicles with environmentally unfriendly engines, making biodiesel available, lowering first registration charges for low-emission vehicles and charging higher annual licence fees for high emissions vehicles. It will also be important to expand the rail infrastructure and coordinate rail and bus feeder services more efficiently. Management of traffic density and flow to reduce the street canyon effect will also be crucial.

Marine emission controls should include voluntary schemes for reduction, the reduction of land-based emissions at port, use of cleaner gasoil, retrofitting engines of local seacraft, and higher levels of collaboration with Shenzhen and Guangdong in respect of ‘green port’ policies.


Views put forward in this article are disputed in another article.

  1. Cross-border pollution

See Also

  1. Total emissions calculation
  2. Source-based calculation
  3. Time-based analysis


  1. - last accessed 8/8/10

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