Fractionation of halogenated organic matter present in rain and snow

Organic matter in samples of rain and snow from Sweden, Poland, Germany and the Republic of Ireland was fractionated by employing a series of filtration, purging, evaporation and extraction steps. Determinations of the group parameter AOX (adsorbable organic halogens) in aqueous phases and EOX (extractable organic halogens) in organic phases showed that halogenated organic matter present in bulk precipitation is composed of several different groups of compounds. The largest amounts of organically bound halogens were found in fractions of relatively polar and non-volatile to semivolatile compounds. In particular, a significant part of the AOX could be attributed to alkaline-labile organic bases. Gas chromatographic analysis of different organic extracts in the chlorine channel of an atomic emission detector (AED) resulted in chromatograms with few distinct peaks, and analysis in the bromine channel did not produce any distinct peaks. Chlorinated acetic acids were the most abundant halogenated organic acids, and chlorinated alkyl phosphates were normally responsible for the largest peaks in the chlorine chromatogram of neutral, hexane-extractable compounds. When analysing volatiles, 1,4-dichlorobenzene and a thus far unidentified chloroorganic compound often caused the largest response in the chlorine channel of the AED system.     

Determination of group parameters for organically bound chlorine, bromine and iodine in precipitation

The presence of organically bound halogens in precipitation was studied by first adsorbing organics on activated carbon and then analysing the chloride, bromide and iodide formed during combustion of the carbon. A standard instrument for the group parameter AOX (adsorbable organic halogens) was used for the combustion. The halides formed were trapped in an alkaline solution and analysed by capillary zone electrophoresis. The method described enabled determination of sub-ppb concentrations of the group parameters AOCl, AOBr and AOI (adsorbable organic chlorine, bromine and iodine, respectively). Analysis of rain and snow collected at different sites in Europe showed that organochlorines were responsible for the major part of the AOX content in all samples collected. Organically bound bromine was found in sub-ppb concentrations in all of the samples, whereas organic iodine was detected in only two of the samples.