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The effect of exposure of bacterial suspensions to UV radiation by means of the dose-response curves was assessed. The D37 and D10 values were used for subsequent statistical analysis of the results. The aim of this article is to evaluate the sensitivity to UV radiation of several microorganisms of different habitats (Rhizobium meliloti, Rhodobacter sphaeroides, Escherichia coli, and Deinococcus radiodurans), two mutants with nonfunctional SOS DNA repair system (R. meliloti recA- and E. coli recA-), and a mutant in the synthesis of carotenoids (R. sphaeroides crtD). The results reveal that D. radiodurans was an extremely resistant bacterium, R. meliloti was more resistant than R. sphaeroides, and E. coli was the most sensitive bacterium tested. The high sensitivity of recA- mutants was also verify. Moreover, it seems that the possession of pigments had no important effect in the sensitivity of R. sphaeroides to UV radiation.

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The disappearance of fenitrothion under real environmental conditions was studied. Fenitrothion was applied in the rice crop field of the Ebre Delta (Tarragona, Spain) during July 1995 by helicopter spray ing at a rate of 148 mL/ha Tionfos 50 LE (50% of pure fenitrothion). For monitoring fenitrothion residues in water, two different analytical techniques were used:  enzyme-linked immunosorbent assay (ELISA) and automated on-line solid-phase extraction (Prospekt) followed by liquid chromatography/diode array detection (LC/DAD). The unequivocal identification of fenitrothion, fenitrooxon, 3-methyl-4-nitrophenol, and s-methyl isomer of fenitrothion was achieved by liquid chromatography/mass spectrometry (LC/MS) using an atmospheric pressure chemical ionization (APCI) interface in the negative ionization (NI) mode. The residue levels of fenitrothion in rice crop field waters varied from 119−178 μg/L down to 3.8−1.5 μg/L after 48 h of helicopter application. The half-lifetimes t 1/2 were calculated by both analytical techniques being 19.3 for ELISA and 11 h for LC/DAD after treatment, with a disappearance rate of 0.036 and 0.063, respectively.