Air pollution as well as climate change and their possible effects on the environment,ecosystems and human health,are pressing challenges.Nowadays,it is clear that sustainable societal development cannot remain solely wealth-oriented,but must take into account the present and future environmental issues.However,this approach is possible only if scientifically sound knowledge in all environmental areas becomes available to our societies and decision makers,which requires a firm scientific basis to our understanding of the processes guiding the atmospheric compositions.