Concentrations and sources of non-methane hydrocarbons (NMHCs) from 2005 to 2013 in Hong Kong: A multi-year real-time data analysis

Long-term O<sub>3</sub>–precursor relationships in Hong Kong: field observation and model simulation

“…In addition, the quality of the real-time data was assured by regular comparison with whole-air canister samples collected and analysed by the University of California at Irvine (UCI). More details can be found in reports of previous studies in Hong Kong (Xue et al, 2014;Ou et al, 2015;Lyu et al, 2016).…”

“…The selection of this site for the trend study was due to its downwind location being a good receptor for urban plume, suffering high O 3 pollution, and having the most comprehensive dataset. More detailed description of the TC site can be found in our previous papers Cheng et al, 2010;Ling et al, 2013;Ou et al, 2015).…”

“…The elevation of TC is 37.5 m above sea level. It is surrounded by a newly developed residential town on the northern Lantau Island, and is downwind of urban Hong Kong and the inland PRD region when easterly and northeasterly winds are prevailing (Ou et al, 2015). At TC, the prevailing wind varies by season, being from the east in spring and autumn, from the southwest in summer, and from the northeast in winter (see Fig.…”

“…Moreover, the long-term trends of individual VOCs, except for BVOC, were different from that of TVOCs (see Fig. S8) because many control measures were taken in the last decade, which altered the composition of VOCs in the atmosphere, such as the reduction of toluene by solvent usage control and the increase in alkanes in liquefied petroleum gas (LPG) in 2005(Ou et al, 2015 and the decrease in LPG alkanes in 2013-2014 (Lyu et al, 2016). Here we defined December-February, March-May, June-August, and September-November as winter, spring, summer, and autumn, respectively.…”

“…Considering the shortest distance between the inland PRD and TC (i.e. from the centre of Shenzhen to the TC site, ∼ 30 km) and the average wind speed in different seasons (Ou et al, 2015), it would take approximately 3.4 ± 0.3, 4.3 ± 0.3, 4.0 ± 0.5, and 3.7 ± 0.4 h in spring, summer, autumn, and winter, respectively, for NO 2 originating in the inland PRD to arrive at TC. Hence, although NO 2 emitted from the inland PRD is slightly more likely to arrive at TC in winter and spring than in summer and autumn, the differences in travel time between the seasons are relatively small and it is difficult to be precise about seasonal average estimates of NO 2 lifetime and travel time.…”