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Abstract: Mesotrione is a new selective herbicide used for maize crops. The responses of microbial communities of a chernozem soil (Limagne basin, France) to pure or formulated (Callisto®) mesotrione, applied at three different doses [one fold field rate (1 × FR), 10 × FR and 100 × FR], were studied using a laboratory microcosm approach. The effects were assessed on the prokaryotic cell abundance, the overall microbial activities (substrate-induced respiration (SIR) and dehydrogenase activity (DHA)) and the genetic structure of the bacterial and fungal communities (temporal temperature/denaturing gradient gel electrophoresis (TT/DGGE)). Mesotrione dissipation was similar whatever the formulation applied and the amounts dissipated were positively correlated to application rates. Several biodegradation products including the metabolites 4-methylsulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4-methylsulfonylbenzoic acid (AMBA) were detected from day 42 post-treatment, in 10 × FR and 100 × FR treated soils. No response of the soil microbial communities was detected in soil spread with both the 1 × FR applications. Overall soil microbial activity was stimulated from day 6 by 10 × FR of Callisto® and more strongly by 100 × FR of pure mesotrione and Callisto®, whereas prokaryote abundance did not increase before day 95 in both the 100 × FR treatments. Genetic structural shifts recorded from day 42 in the bacterial and fungal communities were small and mainly attributable to variations in band intensity. Maximum dissimilarity of the bacterial and fungal genetic structures between control and 100 × FR treated soils did not exceed 12% and 28%, respectively. The general pattern was that more consistent effects occurred with increasing exposure times, especially in both the 100 × FR treated soils. These microbial responses could be due to the stimulation of (i) adapted mesotrione-degrading microorganisms and (ii) the activity of resistant heterotrophic microbial groups promoted by dead biomass from sensitive organisms. In addition, at 100 × FR doses, pure mesotrione seemed to induce stronger microbial responses than Callisto®, formulation which contains adjuvants with potential side-effects on some microbial populations. This experimental approach indicated that pure mesotrione and Callisto® affected soil microbial communities, but the effects were only detected at doses far exceeding the recommended field rates. [Copyright &y& Elsevier]

Dissipation kinetics of mesotrione, a new triketone herbicide, sprayed on soil from Limagne (Puy-de-Dôme, France) showed that the soil microflora were able to biotransform it. Bacteria from this soil were cultured in mineral salt solution supplemented with mesotrione as sole source of carbon for the isolation of mesotrione-degrading bacteria. The bacterial community structure of the enrichment cultures was analyzed by temporal temperature gradient gel electrophoresis (TTGE). The TTGE fingerprints revealed that mesotrione had an impact on bacterial community structure only at its highest concentrations and showed mesotrione-sensitive and mesotrione-adapted strains. Two adapted strains, identified as Bacillus sp. and Arthrobacter sp., were isolated by colony hybridization methods. Biodegradation assays showed that only the Bacillus sp. strain was able to completely and rapidly biotransform mesotrione. Among several metabolites formed, 2-amino-4-methylsulfonylbenzoic acid (AMBA) accumulated in the medium. Although sulcotrione has a chemical structure closely resembling that of mesotrione, the isolates were unable to degrade it. [Copyright &y& Elsevier]

[Display omitted] • Considering the landscape context(s) increases realism of pesticide ERA. • A flexible conceptualization is needed to compare & integrate different approaches. • We propose to build the effect assessment on spatial-explicit exposure frames. • Comparing model outputs with real-life monitoring data is key for regulatory use. • Conducting a set of case studies will help to confirm implementability. While pesticide use is subject to strict regulatory oversight worldwide, it remains a main concern for environmental protection, including biodiversity conservation. This is partly due to the current regulatory approach that relies on separate assessments for each single pesticide, crop use, and non-target organism group at local scales. Such assessments tend to overlook the combined effects of overall pesticide usage at larger spatial scales. Integrative landscape-based approaches are emerging, enabling the consideration of agricultural management, the environmental characteristics, and the combined effects of pesticides applied in a same or in different crops within an area. These developments offer the opportunity to deliver informative risk predictions relevant for different decision contexts including their connection to larger spatial scales and to combine environmental risks of pesticides, with those from other environmental stressors. We discuss the needs, challenges, opportunities and available tools for implementing landscape-based approaches for prospective and retrospective pesticide Environmental Risk Assessments (ERA). A set of "building blocks" that emerged from the discussions have been integrated into a conceptual framework. The framework includes elements to facilitate its implementation, in particular: flexibility to address the needs of relevant users and stakeholders; means to address the inherent complexity of environmental systems; connections to make use of and integrate data derived from monitoring programs; and options for validation and approaches to facilitate future use in a regulatory context. The conceptual model can be applied to existing ERA methodologies, facilitating its comparability, and highlighting interoperability drivers at landscape level. The benefits of landscape-based pesticide ERA extend beyond regulation. Linking and validating risk predictions with relevant environmental impacts under a solid science-based approach will support the setting of protection goals and the formulation of sustainable agricultural strategies. Moreover, landscape ERA offers a communication tool on realistic pesticide impacts in a multistressors environment for stakeholders and citizens. [ABSTRACT FROM AUTHOR]

Recycling organic waste products in agriculture is a potential route for the dispersion of pharmaceutical residues in the environment. In this study, the concentrations of thirteen pharmaceuticals and the personal care product triclosan (PPCPs) were determined in different environmental matrices from long-term experimental fields amended with different organic waste products (OWPs), including sludge, composted sludge with green wastes, livestock effluents and composted urban wastes applied at usual agricultural rates. PPCP concentrations were different in OWPs, varying from a few micrograms to milligrams per kilogram dry matter or per litre for slurry. OWPs from sludge or livestock effluents primarily contained antibiotics, whereas composted urban wastes primarily contained anti-inflammatory compounds. PPCP contents in soils amended for several years were less than a few micrograms per kilogram. The most persistent compounds (fluoroquinolones, carbamazepine) were quantified or detected in soils amended with sludge or composted sludge. In soils amended with composted municipal solid waste, carbamazepine was quantified, and fluoroquinolones, ibuprofen and diclofenac were sometimes detected. The small increases in fluoroquinolones and carbamazepine in soils after individual OWP applications were consistent with the fluxes from the applied OWP. The measured concentrations of pharmaceuticals in soil after several successive OWP applications were lower than the predicted concentrations because of degradation, strong sorption to soil constituents and/or leaching. Dissipation half-lives (DT 50 ) were approximately 750–2500, 900 and < 300 days for fluoroquinolones, carbamazepine and ibuprofen, respectively, in temperate soils and < 350 and < 80 days for fluoroquinolones and doxycycline, respectively, in tropical soils. Detection frequencies in soil leachates were very low (below 7%), and concentrations ranged from the limits of detection (0.002–0.03 μg/L) and exceptionally to 0.27 μg/L. The most frequently detected pharmaceuticals were carbamazepine and ibuprofen. Based on the risk quotient, the estimated ecotoxicological risks for different soil organisms were low. [ABSTRACT FROM AUTHOR]

The stable oxygen isotope composition of atmospheric CO 2 and the mixing ratio of carbonyl sulphide (OCS) are potential tracers of biospheric CO 2 fluxes at large scales. However, the use of these tracers hinges on our ability to understand and better predict the activity of the enzyme carbonic anhydrase (CA) in different soil microbial groups, including phototrophs. Because different classes of the CA family (α, β and γ) may have different affinities to CO 2 and OCS and their expression should also vary between different microbial groups, differences in the community structure could impact the ‘community-integrated’ CA activity differently for CO 2 and OCS. Four soils of different pH were incubated in the dark or with a diurnal cycle for forty days to vary the abundance of native phototrophs. Fluxes of CO 2 , CO 18 O and OCS were measured to estimate CA activity alongside the abundance of bacteria, fungi and phototrophs. The abundance of soil phototrophs increased most at higher soil pH. In the light, the strength of the soil CO 2 sink and the CA-driven CO 2 -H 2 O isotopic exchange rates correlated with phototrophs abundance. OCS uptake rates were attributed to fungi whose abundance was positively enhanced in alkaline soils but only in the presence of increased phototrophs. Our findings demonstrate that soil-atmosphere CO 2 , OCS and CO 18 O fluxes are strongly regulated by the microbial community structure in response to changes in soil pH and light availability and supports the idea that different members of the microbial community express different classes of CA, with different affinities to CO 2 and OCS. [ABSTRACT FROM AUTHOR]

The impact of a crude extract of Microcystis aeruginosa (PCC7820) containing 14 microcystin variants was investigated on seeds germination and radicles development of four agricultural plants: two tomato varieties Solanum lycopersicum (MicroTom and Saint-Pierre), the wheat Triticum aestivum and the lettuce Lactuca sativa . In addition, the effect of 14 d-exposure to irrigation water containing realistic concentrations of microcystins (0–0.1 mg eq. microcystin-LR L − 1 ) on the tomato MicroTom seedling growth was further evaluated on roots and aerial part biomasses. Impacts on soil bacterial parameters, as such extracellular enzymatic activities, nitrification activity and abundances of ammonia-oxidizing microorganisms were also investigated. In germination-test, the cyanobacterial extract inhibited only the germination of the wheat seeds, with an EC 50 of 11 mg eq. microcystin-LR L −1 ; which is 13 times lower than that of the cadmium chloride (EC 50 of 145 mg L −1 ). Moreover, the cyanobacterial extract containing low concentrations of microcystins increased the growth of primary roots; however, high concentrations decreased it for all plants except for the wheat. In the soil–plant approach, only aerial part biomass of the tomato MicroTom was enhanced significantly. In addition, only soil nitrification potential and ammonia-oxidizing bacterial abundances were consistently impacted. A significant positive correlation ( r = 0.56) was found between the increase of nitrification potential and abundances of ammonia-oxidizing bacteria. This work suggested, that exposure to a cyanobacterial extract containing realistic environmental microcystins concentrations could affect seed germination, depending plant species. It was also highlighted, for the first time, disturbances in soil bacteria functioning, evidences on soil nitrification process. [ABSTRACT FROM AUTHOR]