Effects of temperature and relative humidity on the partitioning of atmospheric oxidized mercury at a high-altitude mountain background site in Taiwan

• Published in: Atmospheric environment (1994) Vol. 261; p. 118572
• Main Authors: Nguyen, Ly Sy Phu, Sheu, Guey-Rong, Chang, Shuenn-Chin, Lin, Neng-Huei
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.09.2021
• Subjects: air; altitude; biogeochemical cycles; East Asia; Free troposphere; Gas-particle partitioning; mercury; Mercury speciation; oxidation; relative humidity; stratosphere; summer; Taiwan; temperature; troposphere; Taiwan; Gas-particle partitioning; East Asia; Mercury speciation; Free troposphere
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2021.118572

Gas-particle partitioning of oxidized mercury (Hg) plays an important role in governing the speciation, transport and deposition of atmospheric Hg. Although studies on gas-particle partitioning of oxidized Hg have been conducted at some urban sites, comparable studies at remote mountain sites are still limited. This study analyzes multi-year (2014–2016) data of speciated atmospheric Hg concentrations from Lulin Atmospheric Background Station (LABS, 2862 m above sea level), Taiwan, to explore the factors that influence the gas-particle partitioning of atmospheric oxidized Hg. Mean concentrations (±S.D.) of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM) were 1.54 ± 0.34 ng m−3, 14.5 ± 26.5 pg m−3, and 5.0 ± 12.0 pg m−3, respectively. In addition, our results indicated that the partitioning of Hg(II) toward particles was favored in the upper free troposphere and/or lower stratosphere. Both temperature (T) and relative humidity (RH) were found to strongly affect the gas-particle partitioning of oxidized Hg. Significant negative correlations between the partitioning coefficient (Kp) and T were obtained for all seasons, but peaked in summer. When RH<30%, Kp decreased with increasing RH. However, Kp and RH were positively correlated when RH>30%. Two empirical Kp-T and Kp-T-RH regression equations: log(1/Kp) = 15.0 – 3887.6(1/T) and log(1/Kp) = 17.92 – 4390.0(1/T) – 0.016RH were developed for free tropospheric air downwind of continental East Asia, which could be implemented in a chemical transport model to improve our understanding of the Hg biogeochemical cycle. [Display omitted] •Gas-particle partitioning of Hg(II) was characterized at a mountain site in East Asia.•Partitioning coefficient (Kp) correlated with temperature negatively.•Kp increased with increasing relative humidity (RH) when RH>30%.•However, Kp decreased with increasing RH when RH<30%.•Partitioning of Hg(II) toward particles was favored in the upper free troposphere.