Bromochloromethoxybenzenes in the marine troposphere of the Atlantic Ocean: A group of organohalogens with mixed biogenic and anthropogenic origin

Halogenated methoxybenzenes (anisoles) are ubiquitous organics in the environment, although they are not produced in technical quantities. To elucidate the sources of the various halogented anisoles in the marine troposphere, their concentrations were measured in air from the Eastern Atlantic Ocean between 40 degrees N and 57 degrees S during the north-south transect ANT XI/1 of the German RV Polarstern. A typical pattern of eight congeners was observed. it consisted of 2,4,6-trichloro-, 2,3,4,6-tetrachloro-, pentacbloro-, 2,4-dibromo-, 2,6-dibromo-, 2,4,6-tribromo-, and two unidentified dibromochloroanisoles. The meridional concentration profiles, the comparison of the patterns of the relative concentrations of bromo- and chloroanisoles, as well as principal component analysis of the concentrations of the halogenated anisoles indicate an anthropogenic origin for the chloroanisoles and a biogenic origin for the bromoanisoles. The pattern of the chloroanisoles differs for the two hemispheres. It seems to reflect the global pollution with chlorophenols which have a maximum of anthropogenic input in the Northern Hemisphere. The pattern of the bromoanisoles is characterized by regional biogenic sources, which leads to high concentrations of bromoanisoles south of 20 degrees N in contrast to low concentrations of chloroanisoles in this part of the Atlantic Ocean.