Aerobic nonylphenol degradation and nitro-nonylphenol formation by microbial cultures from sediments

Nonylphenol (NP) is an estrogenic pollutant which is widely present in the aquatic environment. Biodegradation of NP can reduce the toxicological risk. In this study, aerobic biodegradation of NP in river sediment was investigated. The sediment used for the microcosm experiments was aged polluted with NP. The biodegradation of NP in the sediment occurred within 8 days with a lag phase of 2 days at 30°C. During the biodegradation, nitro-nonylphenol metabolites were formed, which were further degraded to unknown compounds. The attached nitro-group originated from the ammonium in the medium. Five subsequent transfers were performed from original sediment and yielded a final stable population. In this NP-degrading culture, the microorganisms possibly involved in the biotransformation of NP to nitro-nonylphenol were related to ammonium-oxidizing bacteria. Besides the degradation of NP via nitro-nonylphenol, bacteria related to phenol-degrading species, which degrade phenol via ring cleavage, are abundantly present

Time integrative sampling properties of Speedisk and silicone rubber passive samplers determined by chemical analysis and in vitro bioassay testing

Compared to grab samples, passive samplers have the advantage that they sample over a longer time period and can detect lower compound concentrations in water quality monitoring campaigns. To allow the determination of time-weighted average concentrations, however, sampler uptake should remain linear in time over the entire sampling period. Therefore, the time integrative or linear uptake properties of adsorption-based Speedisks and partitioning-based silicone rubber samplers were assessed with respect to chemically analyzed single compounds and measured bioactivity in in vitro bioassays. Both sampler types were deployed in consecutive and overlapping time series in a WTTP effluent and in the river Meuse up to 105 days. Extracts were chemically analyzed for PCBs, PAHs and pesticides and tested in the Aliivibrio fischeri and DR-LUC bioassays. Speedisks showed time integrative sampling for the detected pesticides as well as for bioassay responses at both sampling locations for the entire sampling period. The silicone rubber samplers showed poor linear uptake in time for the unknown compounds causing bioassay responses. The bioassay results indicate that conversion of a bioassay response to a passive sampler extract into a time-weighted average bioactivity per liter water seems justified for Speedisks, confirming that concentrations in the samplers correspond to a single volume of sampled water for all compounds. The bioassay results also indicate that a similar conversion for silicone rubber extracts should be interpreted with caution. In principle, it is actually impossible, because the concentration of each compound contributing to the bioassay response corresponds to a different sampled water volume

Time-Integrative Passive sampling combined with TOxicity Profiling (TIPTOP): an effect-based strategy for cost-effective chemical water quality assessment.

This study aimed at demonstrating that effect-based monitoring with passive sampling followed by toxicity profiling is more protective and cost-effective than the current chemical water quality assessment strategy consisting of compound-by-compound chemical analysis of selected substances in grab samples. Passive samplers were deployed in the Dutch river delta and in WWTP effluents. Their extracts were tested in a battery of bioassays and chemically analyzed to obtain toxicity and chemical profiles, respectively. Chemical concentrations in water were retrieved from publicly available databases. Seven different strategies were used to interpret the chemical and toxicity profiles in terms of ecological risk. They all indicated that the river sampling locations were relatively clean. Chemical-based monitoring resulted for many substances in measurements below detection limit and could only explain <20% of the observed in vitro toxicity. Effect-based monitoring yielded more informative conclusions as it allowed for ranking the sampling sites and for estimating a margin-of-exposure towards chronic effect ranges. Effect-based monitoring was also cheaper and more cost-effective (i.e. yielding more information per euro spent). Based on its identified strengths, weaknesses, opportunities, and threats (SWOT), a future strategy for effect-based monitoring has been proposed

Passive sampling and benchmarking to rank HOC levels in the aquatic environment

The identification and prioritisation of water bodies presenting elevated levels of anthropogenic chemicals is a key aspect of environmental monitoring programmes. Albeit this is challenging owing to geographical scales, choice of indicator aquatic species used for chemical monitoring, and inherent need for an understanding of contaminant fate and distribution in the environment. Here, we propose an innovative methodology for identifying and ranking water bodies according to their levels of hydrophobic organic contaminants (HOCs) in water. This is based on a unique passive sampling dataset acquired over a 10-year period with silicone rubber exposures in surface water bodies across Europe. We show with these data that, far from point sources of contamination, levels of hexachlorobenzene (HCB) and pentachlorobenzene (PeCB) in water approach equilibrium with atmospheric concentrations near the air/water surface. This results in a relatively constant ratio of their concentrations in the water phase. This, in turn, allows us to (i) identify sites of contamination with either of the two chemicals when the HCB/PeCB ratio deviates from theory and (ii) define benchmark levels of other HOCs in surface water against those of HCB and/or PeCB. For two polychlorinated biphenyls (congener 28 and 52) used as model chemicals, differences in contamination levels between the more contaminated and pristine sites are wider than differences in HCB and PeCB concentrations endorsing the benchmarking procedure