Gas-Phase Formation of Environmentally Persistent Free Radicals from Thermal Degradation of Catechol, Hydroquinone, Phenols and Tobacco

Catechol, hydroquinone and Phenol are major constituents of the mainstream tobacco smoke. The toxicity of tobacco has been attributed to the ability of catechol and hydroquinone to undergo endogenous or exogenous redox cycling to form semiquinone type radicals responsible of Reactive Oxygen Species (ROS) formation. ROS such as hydroxyl radicals can cause severe oxidative stress on biological tissues and can provoke severe signaling pathways leading to cardiovascular and pulmonary dysfunctions and carcinogenesis. Given that semiquinone type radicals are organic radicals, characterized by their high instability and reactivity; it is somewhat surprising that they can live long enough mostly when associated with atmospheric fine particles to induce the biological damages reported in the literature. Thus identification of the exact nature of the free radicals, their origin, the reason for their stability and persistency, and their health impacts appear to be an increasing environmental issue. Consequently, we have performed studies of the thermal degradation of catechol, hydroquinone and phenol and structurally similar derivatives that have been proposed as progenitors of semiquinone type radicals. Tobacco pyrolysis has also been investigated. We have employed in conjunction with the Electron Paramagnetic Resonance (EPR), the technique of Low Temperature Matrix Isolation in which catechol, hydroquinone, phenols and Tobacco were pyrolyzed in both low and atmospheric pressures reactor that was directly connected to a liquid nitrogen-cooled cold finger located in the EPR cavity of a Bruker EPR spectrometer. Comprehensive potentially persistent free radicals identification associating additional experimental and mathematical tools has led to the acquisition of the EPR spectra of p- Semiquinone, o-Semiquinone, cyclopentadienyl and phenoxy radicals. The hydroxycyclohexadienyl radical, one of the unexpected radicals according to the decomposition mechanism developed earlier, was found during the atmospheric pyrolysis of phenol. The supposedly very labile radical identified was the hydroxycyclopentadienyl. The methylperoxide type radicals were found when trace of oxygen was used during the pyrolysis experiments. The precursors pyrolysis product analysis employing GC-MS revealed the formation of naphthalene, indenol, indene, benzofuran-2-methyl, indenone, fluorene, and acenaphthylene, thus giving additional evidence of the formation of both labile and potentially persistent free radicals

Direct Mercury Analyzer (DMA) determination of mercury distribution in the sediments of lake Nokoué in Benin Republic-West Africa

Mercury pollution of water bodies constitutes a hazard to both the aquatic life and the populations consuming fishery products. To anticipate the probable eco-toxicological risks that may arise from the largest lake in southern Benin, the present work aims at assessing the mercury status of the sediments of Lake Nokoué, while identifying the areas exposed to anthropogenic mercury contamination. 45 sites were sampled according to a grid plan covering the entire ecosystem of the lake. Employing a Van Veen grab, surface sediments are collected at a depth from 0 to 5 cm in three catches at each site. The composite samples formed at equal mass on the three portions were frozen, lyophilized at - 40 °C, crushed, sieved and homogenized. Fraction less than 63 µm was collected for the mercury content determination by Direct Mercury Analyzer (DMA) operating by atomic absorption according to the US EPA 7473 method. The mercury concentration varies from 1.56 µg/kg to 164.88 µg/kg with an average value of 35.18 µg per kg of sediment. The south-eastern zone of the lake is more concentrated in mercury with a summation of the mercury content of 530.3 µg/kg of sediment. However, the lake has moderate contamination overall (1 ≤ FC ≤ 3). Keywords: Pollution, contamination, mercury, sediment, Lake Nokoué

L’embouteillage dans Les Grandes Villes de L’Afrique de L’ouest et ses Problemes : Cas de Cotonou au Benin

La présente étude axée sur le thème « L’embouteillage dans les grandes villes de l’Afrique de l’Ouest et ses problèmes: cas de Cotonou au Bénin » a pour objectif d’étudier les causes et les conséquences économiques et socio-environnementales de la congestion au niveau des grandes artères de la capitale administrative du Bénin surtout aux heures de pointe. Et pour y parvenir, la collecte des données a été effectuée à travers la recherche documentaire, l’observation directe et participative, l’entretien et l’enquête de terrain. Après le traitement des données, l’analyse des résultats est réalisée suivant le modèle PEIR (Pression, Etat, Impacts, Réponse). En effet, de ces différents résultats, il résulte que la concentration des services administratifs dans la ville de Cotonou, l’exode rural, la défection du réseau routier et la prolifération des engins à deux roues dans ce milieu d’étude constituent les principales causes de l’embouteillage communément appelé « Go Slow » avec pour pôle principal, le carrefour d’Akossombo. Cette situation occasionne de graves préjudices non seulement à l’environnement mais également aux populations du Bénin. Au nombre de ces nuisances, figurent entre autres, la perte de temps et par ricochet d’importantes recettes financières sans oublier la baisse du Produit Intérieur Brut (PIB) pour l’Etat béninois ainsi que pour les entreprises et les sociétés. A toute cette vague de conséquences, s’ajoutent la pollution atmosphérique et sonore, le développement persistant de certaines pathologies comme les céphalées, les infections respiratoires aiguës, le cancer des poumons, le stress, etc. Enfin, pour réduire un tant soit peu les différents problèmes relatifs à ce phénomène dans la ville de Cotonou au sud du Bénin, il importe que les autorités à divers niveaux pensent à la construction de nouvelles infrastructures routières, la délocalisation des services administratifs, des entreprises et sociétés vers des villes secondaires, la subvention des véhicules neufs, la création et l’encouragement du transport en commun, etc.Mots-clés: Cotonou-Embouteillage- Economie-Environnement-Santé-SolutionsEnglish AbstractThis study focused on “”The congestion in the major cities of West Africa and its problems: Case Cotonou in Benin”aims to study the causes and socio-economic and environmental consequences of the congestion at the major arteries of the administrative capital of Benin especially during peak hours. And to achieve this, the data collection was conducted through desk research, direct and participatory observation, interview and field survey. After data processing, analysis of results is carried out following the PEIR model (Pressure, State, Impact, Response). Indeed, these different results, it follows that the concentration of administrative services in the city of Cotonou, the rural exodus, the defection of the road network and the proliferation of two wheeled vehicles in this study environment are the main causes bottling commonly called “Go Slow” with the main pole, the crossroads Akossombo. This situation causes serious harm not only the environment but also to the people of Benin. Among these nuisances, include among others the loss of time and in turn significant financial revenue not to mention the decline in Gross Domestic Product (GDP) for the State of Benin and for companies and societies. A whole wave of consequences, add air and noise pollution, the continuing development of certain diseases such as headaches, acute respiratory infections, lung cancer, stress, etc. Finally, to reduce a little bit different problems related to this phenomenon in the city of Cotonou in southern Benin, it is important that the authorities at various levels think about the construction of new road infrastructure, outsourcing of administrative services, businesses and companies to secondary cities, the grant of new vehicles, the creation and promotion of public transportation, etc.Keywords: Cotonou Embouteillage--Economy-Environment-Health-So

Imputation of Missing Streamflow Data at Multiple Gauging Stations in Benin Republic

Streamflow observation data is vital for flood monitoring, agricultural, and settlement planning. However, such streamflow data are commonly plagued with missing observations due to various causes such as harsh environmental conditions and constrained operational resources. This problem is often more pervasive in under-resourced areas such as Sub-Saharan Africa. In this work, we reconstruct streamflow time series data through bias correction of the GEOGloWS ECMWF streamflow service (GESS) forecasts at ten river gauging stations in Benin Republic. We perform bias correction by fitting Quantile Mapping, Gaussian Process, and Elastic Net regression in a constrained training period. We show by simulating missingness in a testing period that GESS forecasts have a significant bias that results in low predictive skill over the ten Beninese stations. Our findings suggest that overall bias correction by Elastic Net and Gaussian Process regression achieves superior skill relative to traditional imputation by Random Forest, k-Nearest Neighbour, and GESS lookup. The findings of this work provide a basis for integrating global GESS streamflow data into operational early-warning decision-making systems (e.g., flood alert) in countries vulnerable to drought and flooding due to extreme weather events.Comment: AAAI 2022 Fall Symposium: The Role of AI in Responding to Climate Challenges, Nov 17-19, 202

Formation and Stabilization of Persistent Free Radicals

We demonstrate that stable and relatively unreactive “environmentally persistent free radicals (PFRs)” can be readily formed in the post-flame and cool-zone regions of combustion systems and other thermal processes. These resonance-stabilized radicals, including semiquinones, phenoxyls, and cyclopentadienyls, can be formed by the thermal decomposition of molecular precursors including catechols, hydroquinones and phenols. Association with the surfaces of fine particles imparts additional stabilization to these radicals such that they can persist almost indefinitely in the environment. A mechanism of chemisorption and electron transfer from the molecular adsorbate to a redox-active transition metal or other receptor is shown through experiment, and supported by molecular orbital calculations, to result in PFR formation. Both oxygen-centered and carbon-centered PFRs are possible that can significantly affect their environmental and biological reactivity

Assessment of Spatio-Temporal Changes of Land Use and Land Cover over South-Western African Basins and Their Relations with Variations of Discharges

West African basins play a vital role in the socio-economic development of the region. They are mostly trans-boundary and sources of different land use practices. This work attempts to assess the spatio-temporal land use and land cover changes over three South Western African basins (Volta, Mono and Sassandra basins) and their influence on discharge. The land use and land cover maps of each basin were developed for 1988, 2002 and 2016. The results show that all the studied basins present an increase in water bodies, built-up, agricultural land and a decline in vegetative areas. These increases in water bodies and land use are as a result of an increase in small reservoirs, of dugouts and of dam constructions. However, the decline in some vegetative clusters could be attributed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. The basic statistical analysis of precipitation and discharge data reveals that the mean annual discharge varies much more than the total annual precipitation at the three basins. For instance, in the entire Volta basin, the annual precipitation coefficient of variation (CV) is 10% while the annual discharge CV of Nawuni, Saboba and Bui are 43.6%, 36.51% and 47.43%, respectively. In Mono basin, the annual precipitation CV is 11.5% while the Nangbeto and Athieme annual discharge CV are 37.15% and 46.60%, respectively. The annual precipitation CV in Sassandra basin is 7.64% while the annual discharge CV of Soubre and Dakpadou are 29.41% and 37%, respectively. The discharge varies at least three times much more than the precipitation in the studied basins. The same conclusion was found for all months except the driest months (December and January). We showed that this great variation in discharge is mainly due to land use and land cover changes. Beside the hydrological modification of the land use and land cover changes, the climate of the region as well as the water quality and availability and the hydropower generation may be impacted by these changes in land surfaces conditions. Therefore, these impacts should be further assessed to implement appropriate climate services and measures for a sustainable land use and water management

Formation of phenoxy and cyclopentadienyl radicals from the gas-phase pyrolysis of phenol

The formation of radicals from the gas-phase pyrolysis of phenol over a temperature range of 400-1000 degrees C was studied using the technique of low temperature matrix isolation electron paramagnetic resonance (LTMI EPR). Cooling the reactor effluent in a CO2 carrier gas to 77 K produces a cryogenic matrix that exhibits complex EPR spectra. However, annealing by slowly raising the matrix temperature yielded well-resolved, identifiable spectra. All annealed spectra over the temperature range of 700-1000 degrees C resulted in the generation of EPR spectra with six lines, hyperfine splitting constant approximately 6.0 G, g = 2.00430, and peak-to-peak width approximately 3 G that was readily assignable, based on comparison with the literature and theoretical calculations, as that of cyclopentadienyl radical. Annihilation procedures along with microwave power saturation experiments helped to clearly identify phenoxy radicals in the same temperature region. Conclusive identifications of cyclopentadienyl and phenoxy radicals were based on pure spectra of these radicals under the same experimental conditions generated from suitable precursors. Cyclopentadienyl is clearly the dominant radical at temperatures above 700 degrees C and is observed at temperatures as low as 400 degrees C. The low-temperature formation is attributed to heterogeneous initiation of phenol decomposition under very low pressure conditions. The high cyclopentadienyl to phenoxy ratio was consistent with the results of reaction kinetic modeling calculations using the CHEMKIN kinetic package and a phenol pyrolysis model adapted from the literature

Formation of cyclopentadienyl radical from the gas-phase pyrolysis of hydroquinone, catechol, and phenol

The formation of radicals from the gas-phase pyrolysis of hydroquinone, catechol, and phenol over a temperature range of 400-750 degrees C was studied using the technique of low-temperature matrix isolation electron paramagnetic resonance (LTMI EPR). Cooling the reactor effluent from pyrolysis in a nitrogen carrier gas to 77 K produces a cryogenic matrix that exhibits poorly resolved EPR spectra. However, using carbon dioxide as a carrier gas formed a matrix that, upon annealing by slowly raising the matrix temperature followed by rapid recooling to 77 K, yielded more resolved, identifiable spectra. Annealed spectra of all three samples resulted in the generation of EPR spectra above 700 degrees C with 6 lines, hyperfine splitting constant approximately 6.0 G, and peak to peak width approximately 3 G that was readily assignable, based on comparison to the literature and theoretical calculations, as that of cyclopentadienyl radical. Pyrolysis at temperatures below 700 degrees C generated a carbon dioxide matrix isolation spectrum with a high g-value (\u3e2.0040) that is attributed to oxygen-containing radicals such as semiquinone or phenoxyl. Conclusive identification of anticipated semiquinone, phenoxyl, and hydroxycyclopentadienyl radicals was complicated by the ability of these radicals to exist in carbon-centered and oxygen-centered resonance structures that can give different EPR spectra