Séminaire de Ivan Cernusak, professeur à l'Université Comenius de Bratislava (Slovaquie)

Mercury is a neurotoxin that accumulates in fish to levels that can be hazardous to wildlife and humans that consume fish. The atmosphere can transport mercury, mostly in the form of elemental Hg(0), far from the location of emissions to sites where mercury concentrations are low. As a result, the atmospheric transport of mercury strongly influences its global biogeochemical cycling. In this talk we describe the structures and thermodynamic properties of some monohydrates of mercury compounds and discuss the implications of this hydration process to mercury chemistry in the atmosphere. Finally, we will present some results on oxidation of BrHg by ozone.
    The properties, interactions and reactivity of molecules related to anthropogenic activities during the last decades represent hot topic in atmospheric chemistry. Volatile organic compounds (VOC) - pesticides/herbicides have impact on climate, environment and quality of life.
    Pesticides/herbicides belong to partially VOCs that can emitted to atmosphere during the application. Contamination by VOCs leads to health problems but can also cause disturbance of the balance in nature due to their volatility. The basic mechanism during abiotic degradation of VOCs in the atmosphere is photolysis; and subsequent series of radical reactions involving the emerging fragments. Products of these reactions can be again radicals with potential health risks.
    The predictions of thermo-chemical properties of short lived molecular species based on VOCs and their interactions/reactivity with oxidative agents using ab initio calculations is challenging task, due to: a) the size of molecules involved; b) the potential multireference character of some intermediates/transition states.