Some insight into the influence of urban ground surface properties on the air-surface exchange of total gaseous mercury

Experiments utilizing meteorologically normalized sampling conditions were used to illustrate the role and function of urban pavement, bare soil and turf grass surface properties with respect to the air-surface exchange of total gaseous Hg (TGM). After ensuring uniform meteorological effects to each surface, resultant TGM fluxes from turf grass, bare soil and pavement were specifically representative of their diverse physical and biogeochemical properties. Results spanning the entire sampling year show distinct TGM flux signatures for each surface (5.69 ± 5.79 (ng/m² h) for bare soil, 0.53 ± 1.25 for turf grass, 0.26 ± 0.41 for pavement). Based on medians, the surface limitations of pavement decreased TGM flux by a factor of 22 compared to bare soil and by a factor of 2 compared to turf grass. Turf surface limitations decreased TGM flux by a factor of 11 compared to bare soil. By comparing these results to a parallel study, meteorological effects were found to develop 24% of the TGM flux signature for pavement, 53% for turf and 60% for bare soil. The remaining percentage contributions to each TGM flux signature were from the cumulative surface property effects of each surface. These results suggest that the greater the TGM flux magnitude for a particular surface, the more measurements are needed under a wide variety of meteorological conditions to develop a broad understanding of its TGM flux characteristics. Seasonal observation allowed closer investigation of a large shift to TGM deposition for the turf surface during the fall season. The large shift toward deposition was suspected to be linked to the formation of a thatch layer on the unexposed soil surface just beneath the turf layer.