Characteristics and influencing factors of mercury exchange flux between soil and air in Guangzhou City

This study aimed to characterize atmospheric mercury (Hg) as well as the Hg exchange flux between soil and air surfaces in the urban area of Guangzhou. Total gaseous Hg (TGM) concentration and Hg exchange flux were measured in situ using a dynamic flux chamber coupled with a Mercury Vapor Analyzer. The TGM averaged 6.3 ± 2.2 ng·m− 3 at five sites, and average Hg exchange flux was 7.8 ± 7.1 ng·m− 2·h− 1. Both Hg content and soil pH were significantly correlated with Hg fluxes, suggesting that soil properties affected Hg exchanges. The Hg exchange fluxes showed significantly positive correlations with solar radiation and soil temperature. Comparisons demonstrated that vegetation significantly interfered with the Hg emission flux. The annual Hg emission from soil in Guangzhou urban area was 51.46 g·km− 2·yr− 1 or 25.73 kg·yr− 1.