Radiation enhanced uptake of Hg0(g) on iron (oxyhydr)oxide nanoparticlesElectronic supplementary information (ESI) available. See DOI: 10.1039/c7ra07401h

Despite the proposed importance of atmospheric mercury (Hg) cycling, little is known about its heterogeneous chemistry, specifically on ubiquitous dust particle surfaces in the environment. To address this gap in knowledge, we herein report the uptake coefficients for the uptake of Hg 0 (g) on iron (oxyhydr)oxides (γ-Fe 2 O 3 , α-FeOOH, α-Fe 2 O 3 and Fe 3 O 4 ) nanoparticles, employed as proxies for reactive components of mineral dust. Hg 0 (g) -particle interactions were studied in a batch set-up, at ambient pressure (760 ± 5 Torr) and temperatures (295 ± 2 K) with UV and visible irradiation (290 nm ≤ λ ≤ 700 nm). γ-Fe 2 O 3 , α-FeOOH and α-Fe 2 O 3 demonstrated a ca. 40-900-fold increase in uptake kinetics upon irradiation, under our experimental conditions. In contrast, uptake kinetics on Fe 3 O 4 's surface displayed little dependence on irradiation. Relative humidity was shown to inhibit the effect of radiation on the uptake of Hg 0 (g) by α-Fe 2 O 3 . Size distributions, electronic properties, surface area and phase characterization of the iron(oxyhydr)oxide particles were studied to explain the uptake kinetics, and to provide insights into the mechanism of Hg 0 (g) loss. The adsorption capacity of Hg 0 (g) on α-Fe 2 O 3 was determined from the adsorption isotherm fitted with Langmuir, Freundlich and Elovich adsorption models. The implications of the results to atmospheric chemical processes are herein discussed. We herein report kinetic studies on UV-visible radiation (315 ≤ λ ≤ 700 nm) enhanced uptake of Hg 0 (g) by proxies for reactive components of mineral dust (nano γ-Fe 2 O 3 , α-FeOOH, α-Fe 2 O 3 and Fe 3 O 4 ) and propose possible reaction mechanisms.