Dissipation and adsorption of isoproturon, tebuconazole, chlorpyrifos and their main transformation products under laboratory and field conditions

Assessment of dissipation constitutes an integral part of pesticides risk assessment since it provides an estimate of the level and the duration of exposure of the terrestrial ecosystem to pesticides. Within the frame of an overall assessment of the soil microbial toxicity of pesticides, we investigated the dissipation of a range of dose rates of three model pesticides, isoproturon (IPU), tebuconazole (TCZ), and chlorpyrifos (CHL), and the formation and dissipation of their main transformation products following a tiered lab-to-field approach. The adsorption of pesticides and their transformation products was also determined. IPU was the least persistent pesticide showing a dose-dependent increase in its persistence in both laboratory and field studies. CHL dissipation showed a dose-dependent increase under laboratory conditions and an exact opposite trend in the field. TCZ was the most persistent pesticide under lab conditions showing a dose-dependent decrease in its dissipation, whereas in the field TCZ exhibited a biphasic dissipation pattern with extrapolated DT90s ranging from 198 to 603.4 days in the × 1 and × 2 dose rates, respectively. IPU was demethylated to mono- (MD-IPU) and di-desmethyl-isoproturon (DD-IPU) which dissipated following a similar pattern with the parent compound. CHL was hydrolyzed to 3,5,6-trichloro-2-pyridinol (TCP) which dissipated showing a reverse dose-dependent pattern compared to CHL. Pesticides adsorption affinity increased in the order IPU < TCZ < CHL. IPU transformation products showed low affinity for soil adsorption, whereas TCP was weakly adsorbed compared to its parent compound. The temporal dissipation patterns of the pesticides and their transformation products will be used as exposure inputs for assessment of their soil microbial toxicity. © 201

Identification and characterization of tebuconazole transformation products in soil by combining suspect screening and molecular typology

Pesticides generate transformation products (TPs) when they are released into the environment. These TPs may be of ecotoxicological importance. Past studies have demonstrated how difficult it is to predict the occurrence of pesticide TPs and their environmental risk. The monitoring approaches mostly used in current regulatory frameworks target only known ecotoxicologically relevant TPs. Here, we present a novel combined approach which identifies and categorizes known and unknown pesticide TPs in soil by combining suspect screening time-of-flight mass spectrometry with in silico molecular typology. We used an empirical and theoretical pesticide TP library for compound identification by both non-target and target time-of-flight (tandem) mass spectrometry, followed by structural proposition through a molecular structure correlation program. In silico moleculxar typology was then used to group TPs according to common molecular descriptors and to indirectly elucidate their environmental parameters by analogy to known pesticide compounds with similar molecular descriptors. This approach was evaluated via the identification of TPs of the triazole fungicide tebuconazole occurring in soil during a field dissipation study. Overall, 22 empirical and 12 yet unknown TPs were detected, and categorized into three groups with defined environmental properties. This approach combining suspect screening timeofflight mass spectrometry with molecular typology could be extended to other organic pollutants and used to rationalize the choice of TPs to be investigated towards a more comprehensive environmental risk assessment scheme. © 2015 Elsevier Ltd. All rights reserved

Assessment of the impact of three pesticides on microbial dynamics and functions in a lab-to-field experimental approach

The toxicity of pesticides on soil microorganisms is as an emerging area of concern. Novel and well-standardized tools could be now used to provide a robust assessment of the ecotoxicity of pesticides on soil microorganisms. We followed a tiered lab-to-field approach to assess the toxicity of three pesticides, widely used at EU level, (chlorpyrifos (CHL), isoproturon (IPU) and tebuconazole (TBZ)) on (i) the abundance of 11 microbial taxa and 8 functional microbial groups via q-PCR and (ii) the activity of enzymes involved in biogeochemical cycles via fluorometric analysis. Correlation of microbial measurements with the concentration of pesticides, and their transformation products (TPs) in soil enabled the identification of the compounds driving the effects observed. At lab tests (×1, ×2 and ×10 the recommended dose), CHL and TBZ significantly reduced the relative abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) which recovered by the end of the study, while all pesticides induced a persistent reduction in the relative abundance of sulfur-oxidizing bacteria (SOB). The two demethylated metabolites of IPU (MD-IPU and DD-IPU) adversely affected P-cycling enzymes and leucine aminopeptidase (Leu). At field tests (×1, ×2 and ×5 the recommended dose), a persistent reduction on the relative abundance of AOA was induced by all pesticides, but only CHL and its hydrolysis product 3,5,6 trichloro-2-pyridynol (TCP) soil levels were negatively correlated with AOA relative abundance. Our findings suggest that ammonia-oxidizing microorganisms constitute the most responsive microbial group to pesticides and could be potential candidates for inclusion in pesticide risk assessment. © 2018 Elsevier B.V

The dissipation and microbial ecotoxicity of tebuconazole and its transformation products in soil under standard laboratory and simulated winter conditions

Tebuconazole (TBZ) is a widely used triazole fungicide at EU level on cereals and vines. It is relatively persistent in soil where it is transformed to various transformation products (TPs) which might be environmentally relevant. We assessed the dissipation of TBZ in soil under contrasting incubation conditions (standard vs winter simulated) that are relevant to its application scheme, determined its transformation pathway using advanced analytical tools and 14 C-labeled TBZ and assessed its soil microbial toxicity. Mineralization of 14 C-triazole-ring-labeled TBZ was negligible but up to 11% of 14 C-penyl-ring-labeled TBZ evolved as 14 CO 2 within 150 days of incubation. TBZ persistence increased at higher dose rates (×10 compared to the recommended agronomical dose ×1) and under winter simulated conditions compared to standard incubation conditions (at ×1 dose rate DT 50 of 202 and 88 days, respectively). Non-target suspect screening enabled the detection of 22 TPs of TBZ, among which 17 were unknown. Mass spectrometry analysis led to the identification of 1-(4-chlorophenyl) ethanone, a novel TP of TBZ, the formation of which and decay in soil was determined by gas chromatography mass spectrometry. Three hypothetical transformation pathways of TBZ, all converging to 1H-1,2,4-triazole are proposed based on suspect screening. The ecotoxicological effect of TBZ and of its TPs was assessed by measuring by qPCR the abundance of the total bacteria and the relative abundance of 11 prokaryotic taxa and 4 functional groups. A transient impact of TBZ on the relative abundance of all prokaryotic taxa (except α-proteobacteria and Bacteroidetes) and one functional microbial group (pcaH-carrying microorganisms) was observed. However the direction of the effect (positive or negative) varied, and in certain cases, depended on the incubation conditions. Proteobacteria was the most responsive phylum to TBZ with recovery observed 20 days after treatment. The ecotoxicological effects on the soil microorganisms were not correlated with 1-(4-chlorophenyl) ethanone. © 2018 Elsevier B.V

Lab to field assessment of the ecotoxicological impact of chlorpyrifos, isoproturon, or tebuconazole on the diversity and composition of the soil bacterial community

Pesticides are intentionally applied to agricultural fields for crop protection. They can harm non-target organisms such as soil microorganisms involved in important ecosystem functions with impacts at the global scale. Within the frame of the pesticide registration process, the ecotoxicological impact of pesticides on soil microorganisms is still based on carbon and nitrogen mineralization tests, despite the availability of more extensive approaches analyzing the abundance, activity or diversity of soil microorganisms. In this study, we used a high-density DNA microarray (PhyloChip) and 16S rDNA amplicon next-generation sequencing (NGS) to analyze the impact of the organophosphate insecticide chlorpyrifos (CHL), the phenyl-urea herbicide isoproturon (IPU), or the triazole fungicide tebuconazole (TCZ) on the diversity and composition of the soil bacterial community. To our knowledge, it is the first time that the combination of these approaches are applied to assess the impact of these three pesticides in a lab-to-field experimental design. The PhyloChip analysis revealed that although no significant changes in the composition of the bacterial community were observed in soil microcosms exposed to the pesticides, significant differences in detected operational taxonomic units (OTUs) were observed in the field experiment between pesticide treatments and control for all three tested pesticides after 70 days of exposure. NGS revealed that the bacterial diversity and composition varied over time. This trend was more marked in the microcosm than in the field study. Only slight but significant transient effects of CHL or TCZ were observed in the microcosm and the field study, respectively. IPU was not found to significantly modify the soil bacterial diversity or composition. Our results are in accordance with conclusions of the Environmental Food Safety Authority (EFSA), which concluded that these three pesticides may have a low risk toward soil microorganisms. © 2018 Storck, Nikolaki, Perruchon, Chabanis, Sacchi, Pertile, Baguelin, Karas, Spor, Devers-Lamrani, Papadopoulou, Sibourg, Malandain, Trevisan, Ferrari, Karpouzas, Tsiamis and Martin-Laurent

Tamanho de amostra de caracteres em híbridos de mamoneira Sample size of the characters in castor bean

O objetivo deste trabalho foi estimar o tamanho de amostra para avaliar caracteres de híbridos de mamoneira e verificar a variabilidade do tamanho de amostra entre híbridos e caracteres. Foram avaliadas 41 e 55 plantas dos híbridos Sara e Lyra, respectivamente, quanto aos caracteres de semente, de plântula, de planta adulta e de produção em Santa Maria, Estado do Rio Grande do Sul (latitude 29&deg;42'S, longitude 53&deg;49'W e 95m de altitude), no ano agrícola de 2007/2008. O tamanho de amostra apresenta variabilidade entre os híbridos Sara e Lyra para os seguintes caracteres: largura da semente, comprimento do epicótilo aos 14 dias após a emergência, graus-dia para emissão da primeira folha verdadeira, altura de planta no início do florescimento, altura de inserção do primeiro rácemo, número de inflorescências, número de rácemos por planta e número de cápsulas por rácemo. Há aumento do tamanho de amostra (número de plantas) para estimar caracteres de semente, de plântula, de planta adulta e de produção, nessa ordem.<br>The aim of this research was to determine the sample size of the characters of hybrids in castor bean and to verify its variability among hybrids and characters. It was evaluated 41 plants and 55 hybrids (Sara and Lyra), respectively, regarding to the seed characters, adult plant seedling and production in Santa Maria, Rio Grande do Sul State, Brazil (latitude 29&deg;42'S, longitude 53&deg;49'W e 95m de altitude), in the agriculture years of 2007/2008. It was found variability in the sample size among hybrids (Sara e Lyra) in relation to width of the seed, length of epicotyl 14 days after emergence, degree-days for issuance of the first true leaf, plant height at the beginning of flowering, height of the first bunch and the number of inflorescences, bunch per plant and capsules per bunch. There is an increased sample size (number of plants) to determine the characters of seed, seedling, plant and production, in that order

Tamanho de amostra para estimação do coeficiente de correlação linear de Pearson entre caracteres de milho

O objetivo deste trabalho foi determinar o tamanho de amostra para a estimação do coeficiente de correlação linear de Pearson entre caracteres de três híbridos de milho. Para as análises, foram tomadas aleatoriamente 361, 373 e 416 plantas, respectivamente, de híbridos simples, triplo e duplo. Para cada planta, os seguintes caracteres foram mensurados: diâmetro maior e menor do colmo, altura da planta e altura, peso, comprimento e diâmetro da espiga, número de fileiras por espiga, peso e diâmetro de sabugo, massa de cem grãos, número de grãos por espiga, comprimento e produtividade de grãos. Para cada um dos 91 pares de caracteres e híbridos, foi determinado o tamanho de amostra a partir de "bootstrap", com reposição de 1.000 amostras, de cada tamanho de amostra simulado. Na estimação do coeficiente de correlação linear de Pearson com a mesma precisão, o tamanho de amostra (número de plantas) aumenta na direção de pares de caracteres com menor intensidade de relação linear, independentemente do tipo de híbrido. Para os 91 pares de caracteres estudados, 252 plantas são suficientes para a estimação do coeficiente de correlação linear de Pearson, no intervalo de confiança de "bootstrap" de 95%, igual a 0,3