Temporal variation of speciated atmospheric Hg and characteristics of size-fractioned HgP at a suburban site in Shijiazhuang City, North China

Abstract

Atmospheric mercury (Hg) species were determined at a suburban site near Shijiazhuang, China from May 2016 to January 2017 to ascertain their seasonal and diurnal patterns, to identify the relationship with other parameters, and furthermore to elucidate their potential sources areas. The gaseous elemental Hg (GEM) concentration (3.66 ± 2.62 ng m−3) was about 2 times higher than the background level in the Northern Hemisphere, and the fine particulate bound Hg (HgP2.5) concentration (92.4 ± 59.6 pg m−3) was comparable to those at urban sites, while the gaseous oxidized Hg (GOM) level was quite low (5.7 ± 5.6 pg m−3). GEM and HgP2.5 concentrations exhibit pronounced seasonal (January > May > October > August) and diurnal (nighttime > daytime) patterns. In contrast, the seasonal and diurnal patterns of GOM were just opposite to those of GEM and HgP2.5. The significant positive relationship among GEM, HgP, CO, SO2, and NO2 reveals that they have similar anthropogenic sources. Interestingly, the size distributions of HgP in PM10 were observed to be unimodal during the four study periods, and peaks were all located in the fine mode (0.7–2.1 μm), and fine HgP contributed ∼70% (38.2–81.5%) of HgP10, indicating that the fine mode was the dominant size. The potential source contribution function (PSCF) result suggests that GEM level at the sampling site was highly impacted by regional sources rather than the long-range transport, and the potential source areas were predominantly located in southern Hebei and western Shandong. The results of wind rose and cluster analyses were consistent with the PSCF results.