Summertime elemental mercury exchange of temperate grasslands on an ecosystem-scale

[摘要] In order to estimate the air-surface mercury exchange of grasslands in temperate climateregions, fluxes of gaseous elemental mercury (GEM) were measured at two sites inSwitzerland and one in Austria during summer 2006. Two classic micrometeorologicalmethods (aerodynamic and modified Bowen ratio) have been applied to estimate netGEM exchange rates and to determine the response of the GEM flux to changes inenvironmental conditions (e.g. heavy rain, summer ozone) on an ecosystem-scale.Both methods proved to be appropriate to estimate fluxes on time scales of afew hours and longer. Average dry deposition rates up to 4.3 ng m⁻² h⁻¹and mean deposition velocities up to 0.10 cm s⁻¹ were measured, which indicatesthat during the active vegetation period temperate grasslands are a small net sinkfor atmospheric mercury. With increasing ozone concentrations depletion of GEMwas observed, but could not be quantified from the flux signal. Night-timedeposition fluxes of GEM were measured and seem to be the result of mercury co-depositionwith condensing water. Effects of grass cuts could also be observed,but were of minor magnitude.

[学科分类] 大气科学