engleski

Oxidation state of organic matter in bulk atmospheric precipitation and aerosols

Organic matter in the environment play a crucial role in complex biogeochemical processes in aquatic systems and atmosphere. Organic matter in atmosphere is a result of primary anthropogenic and biogenic emissions and/or of transformation processes of different precursors. The interactions between the atmosphere and aquatic systems are of considerable importance for the fate, transport and cycling of organic matter and other microconstituents in the environment, having thus a decisive role in global changes and in environmental protection. Traces of organics in the atmosphere are efficently removed by wet precipitations, specially the soluble ones, polar and partially volatile compounds, while washing out of volatile compounds is very low. In global sense precipitations can weaken oxidation potential of the atmosphere, i.e. they can decrease the posibility of trace species oxidation since the water droplets decrease the concentration of soluble trace gas species, e.g. of formaldehide which is the source of hydroperoxyl radical (HO2) in gas fraction. Droplets can also reduce concentrations of other gas fraction species due to specific reactions. Ozon which is very important oxidant in the atmosphere, although is not well soluble, can react in droplets with O2- radical and thus can be removed from the atmosphere. Moreover a change in ozon concentration in the atmosphere can significantly influence the chemical processes there. The oxidation state of the organic carbon present in the atmosphere is an efficient tool for additional qualitative and quantitative characterization of organic matter in atmospheric precipitations and aerosols what is of special interest for understanding the pertaining physico-chemical processes. Oxidation state of organic matter in the samples of natural waters and atmospheric precipitations and aerosols can be estimated from the measured values for total organic carbon (TOC) or dissolved organic carbon (DOC) and chemical oxygen demand (COD) measurements. TOC, DOC and COD are collective parameters important for characterization of organic matter. COD gives the quantity of oxygen needed for chemical degradation of organic matter and represents the measure of reduction capacity of organic matter. Concentrations and oxidation state of organic matter have been investigated in the daily bulk precipitation samples, collected in the city of Zagreb in the period from 2009. till 2011. and in aerosol samples in the period of aproximatelly one year (2010 – 2011).

aerosols ; oxidation state ; organic matter

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