Biodegradation of UV-filters in marine sediments

The degradation of two of the most frequently used UV-filters was investigated through microcosm studies. Marine
sediments sampled fromtwo sites in Italy (La Spezia harbour and Sarno river estuary, S1 and S2 respectively)
were used to set up aerobic and anaerobic sets of reactors. The sediments were spiked with a methanol solution
of 3-(4-methylbenzylidene)camphor (4-MBC) and 2-ethylhexyl 4-(dimethylamino)benzoate (EH-DPAB), at
concentrations of either 25 or 50 mg kg-1 each. Methanol (6.3 g/L) also served as an organic amendment and
growth substrate for improving microbial activity.Monitoring of the biotic and abiotic degradation of the selected
contaminants over 16 months revealed that 4-MBC biodegradationwas very slow and incomplete,whereas over
90% of EH-DPAB was degraded both in the aerobic and the anaerobic reactors by the natural microbial communities
of both sediments. Repeated spikes of EH-DPAB were followed by complete decay, characterised by firstorder
kinetics. The calculated kinetic rate constants under aerobic and anaerobic conditions were similar. In reactors
inoculated with the S1 sediment the degradation rate constants progressively increased after each spike,
up to the value of 0.039 d-1. For the S2 sediment the rate constant was around 0.020 d-1 throughout the duration
of the experiment. Mass spectrometry analysis of sediment extracts allowed detection of potential transformation
products of EH-DPAB and 4-MBC. Moreover, the natural microbial community of the sediments was
studied using the CAtalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) both in the initial
sediments and after degradation under aerobic and anaerobic conditions.