Fig. 1.
Locations of the Hong Kong Observatory, Air Quality Monitoring Station (Central/Western) and Waglan Island.
Fig. 2.
Time series of RV occurrence, concentrations of SO2 and O3. (Bars, symbols, solid lines and dotted lines show monthly mean, annual mean, 12-month running mean and overall linear regression trend, respectively.)
Table 1. Overall and seasonal annual trends of RV, SO2, NO2, NOx, O3, and PM10 (winter: December, January, and February; spring: March, April, and May; summer: June, July, and August; autumn: September, October, and November)
[i] a‘No Trend’ indicates that the trend is statistically insignificant at the significance level of 0.10.
Fig. 3.
Seasonal Patterns of (a) precipitation and RV, (b) concentrations of PM10, NO2, NOx, (c) SO2, and O3.
Fig. 4.
(a, b, c) Wind roses, (d, e, f) number of moderately hazy days (light blue) and hazy days (blue) and (g, h, i) RV vs. wind direction sectors during 2001–2004.
Fig. 5.
120-h backward air trajectories on hazy days (a: summer; b: winter) and moderately hazy days (c: summer; d: winter) at Hong Kong during 2001–2004.
Fig. 6.
Annual total emissions and ship emissions of SO2, NOx and PM10 (Data source: http://www.epd.gov.hk/epd/english/environmentinhk/air/data/emission_inve.html).
Table 2a. Summary of equations calculated by multiple linear regression method
[i] aUnits of RV are % and those of all air pollutants are µg m−3.
Table 2b. Summary of regression coefficients and partial correlation coefficients calculated by the multiple linear regression method
[i] aSignificance level p<0.05.
[ii] bSignificance level p<0.001.
[iii] cSignificance level p<0.01.
Fig. 7.
Ratios of sulphate concentrations in PM2.5 to the concentrations of sulphate plus SO2 (upper panel). PM2.5 and sulphate concentration data (lower panel) were adopted from Chow et al. (2010).
Fig. 8.
Chemical coupling among trace gases leading to impacts on visibility degradation in the Hong Kong region – see text for details. Percentage values indicate the light extinction contributions of various species given by Wang (2003).
