Pollutants

For most micropollutants (MPs) present in surface waters, such as pesticides and pharmaceuticals, the contribution of biotransformation to their overall removal from lake ecosystems is largely unknown. This study aims at empirically determining the biotransformation rate constants for 35 MPs at different periods of the year and depths of a meso-eutrophic lake. We then tested statistically the association of environmental parameters and microbial community composition with the biotransformation rate constants obtained. Biotransformation was observed for 14 out of 35 studied MPs for at least one sampling time. Large variations in biotransformation rate constants were observed over the seasons and between compounds. Overall, the transformation of MPs was mostly influenced by the lake's temperature, phytoplankton density and bacterial diversity. However, some individual MPs were not following the general trend or association with microorganism biomass. The antidepressant mianserin, for instance, was transformed in all experiments and depths, but did not show any relationship with measured environmental parameters, suggesting the importance of specific microorganisms in its transformation. The results presented here contribute to our understanding of the fate of MPs in surface waters and thus support improved risk assessment of contaminants in the environment.

One of the major problems with pesticides is linked to the non-negligible proportion of the sprayed active ingredient that does not reach its intended target and contaminates environmental compartments. Here, we have implemented and provided new insights to the preventive bioremediation process based on the simultaneous application of the pesticide with pesticide-degrading microorganisms to reduce the risk of leaching into the environment. This study pioneers such a practice, in an actual farming context. The 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) and one of its bacterial mineralizing-strains (Cupriavidus necator JMP134) were used as models. The 2,4-D biodegradation was studied in soil microcosms planted with sensitive (mustard) and insensitive (wheat) plants. Simultaneous application of a 2,4-D commercial formulation (DAM®) at agricultural recommended doses with 10⁵ cells.g⁻¹ dw of soil of the JMP134 strain considerably accelerated mineralization of the herbicide since its persistence was reduced threefold for soil supplemented with the mineralizing bacterium without reducing the herbicide efficiency. Furthermore, the inoculation of the Cupriavidus necator strain did not significantly affect the α- and β-diversity of the bacterial community. By tackling the contamination immediately at source, the preventive bioremediation process proves to be an effective and promising way to reduce environmental contamination by agricultural pesticides.

The present study investigates the individual degrading behavior of bacterial strains isolated from glyphosate-degrading stream biofilms. In this aim, biofilms were subjected to enrichment experiments using glyphosate or its metabolite AMPA (aminomethyl phosphonic acid) as the sole phosphorus source. Five bacterial strains were isolated and taxonomically affiliated to Ensifer sp. CNII15, Acidovorax sp. CNI26, Agrobacterium tumefaciens CNI28, Novosphingobium sp. CNI35 and Ochrobactrum pituitosum CNI52. All strains were capable of completely dissipating glyphosate after 125–400 h and AMPA after 30–120 h, except for Ensifer sp. CNII15 that was not able to dissipate glyphosate but entirely dissipated AMPA after 200 h. AMPA dissipation was overall faster than glyphosate dissipation. The five strains degraded AMPA completely since formaldehyde and/or glycine accumulation was observed. During glyphosate degradation, the strain CNI26 used the C-P lyase degradation pathway since sarcosine was quantitatively produced, and C-P lyase gene expression was enhanced 30× compared to the control treatment. However, strains CNI28, CNI35 and CNI52 accumulated both formaldehyde and glycine after glyphosate transformation suggesting that both C-P lyase and/or glyphosate oxidase degradation pathways took place. Our study shows different and complementary glyphosate degradation pathways for bacteria co-existing in stream biofilms.

Fiber fragments are one of the dominant types of microplastics in environmental samples, suggesting that synthetic textiles are a potential source of microplastics to the environment. Whereas the release of microplastics during washing of textiles is already well studied, much less is known about the release during abrasion processes. The abrasion of textiles may induce fibrillation of fibers and therefore result in the formation of much finer fiber fragments. The aim of this study was to investigate the influence of abrasion of synthetic textiles on the formation of microplastic fibers and fibrils. Fleece and interlock textile swatches made of polyester were abraded using abrasion tests with a Martindale tester. The microplastic fibers and fibrils formed during abrasion were extracted from the textiles and characterized in terms of number, length, and diameter. The microplastic fibers demonstrated the same diameter than the fibers found in the textiles (fleece: 12.3 μm; interlock: 12.7 μm), while fibrils with a much smaller diameter (fleece: 2.4 μm; interlock: 4.9 μm) were also found. The number of fibrils formed during abrasion in both textiles was higher than the number of microplastic fibers. The majority of the extracted microplastic fibers had a length between 200 and 800 μm, while most fibrils were between 30 and 150 μm, forming two distinct fiber fragment morphologies. The number of microplastic fibers formed during abrasion was 5 to 30 times higher than the number of microplastic fibers that could be extracted from non-abraded samples. The number of fibrils increased after abrasion by more than a factor of 200 for both fabric types. The fibrils formed during abrasion have diameters that fall within the inhalable size for airborne particles. The potential release of fibrils into air during wear of textiles thus raises questions about the human exposure to these materials. Since the Martindale tester can simulate a daily application scenario of textiles over a prolonged period only in a limited way, future studies are needed to establish the correlation between the test results with a real-world scenario.