Evaluation of the effectiveness of air pollution control measures in Hong Kong

From 2005 to 2013, volatile organic compounds (VOCs) and other trace gases were continuously measured at a suburban site in Hong Kong. The measurement data showed that the concentrations of most air pollutants decreased during these years. However, ozone (03) and total non-methane hydrocarbon levels increased with the rate of 0.23 +/- 0.03 and 034 +/- 0.02 ppbv/year, respectively, pointing to the increasing severity of photochemical pollution in Hong Kong. The Hong Kong government has ongoing programs to improve air quality in Hong Kong, including a solvent program implemented during 2007-2011, and a diesel commercial vehicle (DCV) program since 2007. From before to after the solvent program, the sum of toluene, ethylbenzene and xylene isomers decreased continuously with an average rate of -99.1 +/- 6.9 pptv/year, whereas the sum of ethene and propene increased by 48.2 +/- 2.0 pptv/year from before to during the DCV program. Despite this, source apportionment results showed that VOCs emitted from diesel exhaust decreased at a rate of -304.5 +/- 17.7 pptv/year, while solvent related VOCs decreased at a rate of -204.7 +/- 39.7 pptv/year. The gasoline and liquefied petroleum gas vehicle emissions elevated by 1086 +/- 34 pptv/year, and were responsible for the increases of ethene and propene. Overall, the simulated O-3 rate of increase was lowered from 0.39 +/- 0.03 to 0.16 +/- 0.05 ppbv/year by the solvent and DCV programs, because 03 produced by solvent usage and diesel exhaust related VOCs decreased (p < 0.05) by 0.16 +/- 0.01 and 0.05 +/- 0.01 ppbv/year between 2005 and 2013, respectively. However, enhanced VOC emissions from gasoline and LPG vehicles accounted for most of the 03 increment (0.09 +/- 0.01 out of 0.16 +/- 0.05 ppbv/year) in these years. To maintain a zero 03 increment in 2020 relative to 2010, the lowest reduction ratio of VOCs/NOx was similar to 1.5 under the NOx reduction of 20-30% which was based on the emission reduction plan for Pearl River Delta region in 2020. (C) 2016 Elsevier Ltd. All rights reserved.