Bioassay-directed chemical characterization of genotoxic agents in the dissolved and particulate water phases of the Besos and Llobregat Rivers (Barcelona, Spain).

Particulate (greater than 0.22 microns) and dissolved phases of water concentrates (600 mL) of Llobregat and Besos Rivers (Barcelona, Spain), were tested in the Salmonella/microsome assay, tester strains TA98 and TA100. Most of them showed significant mutagenic activity. However, independently of the application of exogenous metabolic activation, the dimethylsulfoxide extracts of the particulate matter exhibited a stronger mutagenic activity than the dissolved phase. This indicated that both rivers are chronically polluted by frameshift and base-pair substitution mutagens and promutagens. In order to investigate their identity, a bioassay-directed column chromatography fractionation of the base-neutrals isolated from the dissolved and particulate phases of Besos river water (7 L) was carried out. The mutagenic activity (TA98) was higher in presence of S9 and was recovered in the more polar fractions, where several mutagenic agents were identified by capillary GC-MS in the negative ion chemical ionization mode (NICI). Among them, o-tolidine, nitroquinoline, nitroaniline, dichlorobenzidine and several aromatic quinones were candidates for fraction mutagenicity.