Measurement of mercury species in the atmosphere and the interactions of ozone and particulate matter with mercury over cropped land
A one year study (July 2006-August 2007) was conducted at Elora, Ontario, Canada to measure gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (HgP) as well as GEM fluxes over cropped land through the four seasons. Ozone (O3) and particulate matter (PM) were also measured to investigate their correlation with mercury. The micrometeorological approach was used for GEM flux determination using a continuous two-level sampling system for GEM concentration gradient measurement above soil surface and crop canopy. The turbulent transfer coefficients were derived from meteorological parameters measured on site. The average GEM flux recorded was 6.49±33.98 ng m-2 hr-1 (mean±SD) while the average GEM, RGM and HgP concentrations were 1.2±0.51 ng m -3, 15.10±10.02 pg m-3 and 16.35±9.54 pg m-3 respectively. The average O3 and PM 2.5 concentrations were 26.15±13.72 ppb and 27.2±30.25 g m-3 respectively. Highest mercury species and PM concentrations were recorded in early spring while highest ozone concentrations were observed in winter. GEM concentrations and fluxes as well as ozone and PM exhibited a diurnal pattern while no pattern was observed for RGM and Hg P. GEM flux showed clear seasonal behaviour with highest volatilization rates recorded in spring and summer. Net radiation, temperature and wind direction were the main factors influencing atmospheric pollutants concentrations.