engleski

Interactions of copper with atmospherically relevant ligands

Atmosphere is a complex medium composed of several coexisting phases ; gas, aerosol particles, condensed water, liquid, and ice particles, and atmospheric aerosol (i.e. deliquescent particles dispersed in the gas) plays a key role. It influences the amount and the distribution of trace gases, affects cloud formation and lifetime and has an important influence on the Earth’s radiative balance (by scattering and absorbing solar and terrestrial radiation). Volatile but also water-soluble organic pollutants (such as catechol, hydroquinone, and resorcinol) are often emitted into the atmospheric gaseous phase. They can dissolve in clouds and moist aerosols and transform into low volatile secondary products through aqueous-phase chemistry. Organic carbon (OC) fraction contributes significantly to atmospheric particles and has a profound effect on atmospheric chemistry, air quality, and climate forcing. Secondary organic aerosol (SOA) formed in the atmosphere from the oxidation of gaseous and aqueous organic compounds, represents a key uncertainty in determining the impact of aerosol on climate, in part due to its complexity and continually changing composition. Water-soluble organic compounds (WSOC) often interact with trace metals and form organo- metallic complexes in the atmospheric aqueous phase. Of special interest are interactions with copper, due its high complexing affinity for organic and inorganic ligands in aqueous medium. In the atmospheric aqueous phase, copper is mainly present in the oxidation state of +II which is its water-soluble form. Laboratory experiments have shown that organic complexing with copper could significantly affect the sink of HO2/O2- ; change the solubility of both, copper and organic compounds ; alter the availability of copper for biological or catalytic interaction ; enhance the partitioning of organic gases into the aqueous phase. Although diverse experimental efforts have been made to assess the affinity of copper for organic ligands, our understanding of its interactions with organics in the atmospheric aqueous phase is still limited. In this work we present an electrochemical investigation of complex formation between copper and phenolic-like compounds which are often found in atmospheric aerosol. Differential pulse cathodic striping voltammetry was used. Reduction current of a copper-ligand complex adsorbed on the surface of the hanging mercury drop electrode was measured. The reduction peak was obtained only for phenols having two adjacent hydroxyl groups, pointing out that the 1, 2- positioned hydroxyl groups are needed for the formation of such complexes.

Aerosol ; copper ; organic ligands

nije evidentirano