Total gaseous mercury (TGM) was monitored at Wanqingsha, a rural site in the central Pearl River Delta region, south China from 23 November to 22 December, 2008. TGM ranged 0.50–18.67 ng m−3 with an average of 2.94 ng m−3. TGM was found to present a diurnal cycle with the maximum at 7:00–8:00 and the minimum at 14:00–16:00 (local time). The afternoon minimum in TGM were likely related to increased vertical mixing and the TGM oxidation by ozone, which was observed to negative correlation with TGM. A sudden increase in TGM from 6:00–7:00 could be due to activation of local surface emission sources by rising air temperature. Similar variations in TGM and trace gases including CO and SO2 suggested potential anthropogenic sources contribution as well. Wind-rose patterns further indicated that the westerly wind might carry high concentration of TGM from the high mercury emission areas of Southwest China and/or local anthropogenic emission sources.Research highlights► Total gaseous mercury (TGM) was monitored in the Pearl River Delta,China. ► TGM was found to present a diurnal cycle. ► TGM sources were ascribed to the long-range transport and/or local emission.