Explore the vast range of titles available.

Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO₂) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO₂ to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.

Population growth and urbanization have led to critical environmental challenges worldwide. Chemical pollutants, especially Potentially Toxic Elements (PTEs) such as Cd (Cadmium), Cu (Copper), Zn (Zinc), Al (Aluminum) and Mn (Manganese), as well as macroelements like P (Phosphorus), affect physicochemical and ecological parameters, posing risks to both human health and biodiversity. This study evaluates the influence of seasonality on the concentration of these PTEs in the waters of the Negro River, Manaus, Amazonas. Sampling was conducted at 60 sites along the river in January 2023, September 2023, and March 2024. Sampling, storage, and analyses followed the procedures established in the Standard Methods for the Examination of Water and Wastewater . Results revealed elevated mean Al and P concentrations (above 1250 µg/L and 250 µg/L, respectively), suggesting significant inputs of organic matter and surface urban pollution. Principal Component Analysis (PCA) revealed distinct patterns in January, higher levels of Na, Mg, Ca, Al, P, Ti, Be, and Cu; in September, predominance of K, Rb, and Ba; and in March, Li and Fe. Contamination by PTEs is multifactorial: although seasonality is a key driver, other factors, such as urbanization, proximity to agricultural areas, and industrial discharges, strongly modulate water quality.

The emissions, deposition, and chemistry of volatile organic compounds (VOCs) are thought to be influenced by underlying landscape heterogeneity at intermediate horizontal scales of several hundred meters across different forest subtypes within a tropical forest. Quantitative observations and scientific understanding at these scales, however, remain lacking, in large part due to a historical absence of canopy access and suitable observational approaches. Herein, horizontal heterogeneity in VOC concentrations in the nearcanopy atmosphere was examined by sampling from an unmanned aerial vehicle (UAV) flown horizontally several hundred meters over the plateau and slope forests in central Amazonia during the morning and early afternoon periods of the wet season of 2018. Unlike terpene concentrations, the isoprene concentrations in the near-canopy atmosphere over the plateau forest were 60% greater than those over the slope forest. A gradient transport model constrained by the data suggests that isoprene emissions differed by 220 to 330%from these forest subtypes, which is in contrast to a 0% difference implemented in most present-day biosphere emissions models (i.e., homogeneous emissions). Quantifying VOC concentrations, emissions, and other processes at intermediate horizontal scales is essential for understanding the ecological and Earth system roles of VOCs and representing them in climate and air quality models.

This work investigates the effect of production scales (laboratory, bench, and pilot) by pyrolysis of Açaí (Euterpe oleracea Mart.) seeds at 450 °C and 1.0 atmosphere, on the yields of reaction products and acid value of bio-oils. The experiments were carried out in batch mode using a laboratory scale reactor of 143 mL, a bench scale reactor of 1.5 L, and a pilot scale reactor of 143 L (≈1:10:1000). The bio-oil was obtained in pilot scale, fractionated by distillation to produce biofuel-like fractions. The distillation of bio-oil was carried out in a laboratory column. The physical-chemistry properties (density, kinematic viscosity, acid value, and refractive index) of bio-oils and distillation fractions were determined. The qualitative analysis was determined by FT-IR and the chemical composition by GC-MS. The pyrolysis showed bio-oil yields from 4.37 to 13.09 (wt.%), decreasing with reactor volume. The acid value of bio-oils varied from 68.31 to 70.26 mg KOH/g. The distillation of bio-oil produced gasoline, light kerosene, and kerosene-like fuel fractions, and the yields were 16.16, 19.56, and 41.89 (wt.%), respectively. The physical-chemistry properties of distillation fractions increase with temperature. The FT-IR analysis of bio-oils and distillation fractions identified the presence of functional groups characteristic of hydrocarbons (alkenes, alkanes, aromatics, and aromatics rings) and oxygenates (carboxylic acids, ketones, esters, ethers, alcohols, phenols). The GC-MS identified 48.24 (area.%) hydrocarbons and 51.76 (area.%) oxygenates in the bio-oil produced in bench scale and 21.52 (area.%) hydrocarbons and 78.48 (area.%) oxygenates in the bio-oil produced in pilot scale. The gasoline-like fraction was composed by 64.0 (area.%) hydrocarbons and 36.0 (area.%) oxygenates, light kerosene-like fraction by 66.67 (area.%) hydrocarbons and 33.33 (area.%) oxygenates, and kerosene-like fraction by 19.87 (area.%) hydrocarbons and 81.13 (area.%) oxygenates.

Biomass-derived products are a promising way to substitute the necessity for petroleum-derived products, since lignocellulosic material is widely available in our atmosphere and contributes to the reduction of greenhouse gases (GHGs), due to zero net emissions of CO2. This study explores the impact of temperature and molarity on the pyrolysis of açaí seeds (Euterpe oleracea, Mart.) activated with KOH and subsequently on the yield of bio-oil, hydrocarbon content of bio-oil, antioxidant activity of bio-oil, and chemical composition of the aqueous phase. The experiments were carried out at 350, 400, and 450 °C and 1.0 atmosphere, with 2.0 M KOH, and at 450 °C and 1.0 atmosphere, with 0.5 M, 1.0 M, and 2.0 M KOH, at laboratory scale. The composition of bio-oils and the aqueous phase were determined by GC-MS, while the acid value, a physicochemical property of fundamental importance in biofuels, was determined by AOCS methods. The antioxidant activity of bio-oils was determined by the TEAC method. The solid phase (biochar) was characterized by X-ray diffraction (XRD). The diffractograms identified the presence of Kalicinite (KHCO3) in biochar, and those higher temperatures favor the formation peaks of Kalicinite (KHCO3). The pyrolysis of açaí seeds activated with KOH show bio-oil yields from 3.19 to 6.79 (wt.%), aqueous phase yields between 20.34 and 25.57 (wt.%), solid phase yields (coke) between 33.40 and 43.37 (wt.%), and gas yields from 31.85 to 34.45 (wt.%). The yield of bio-oil shows a smooth exponential increase with temperature. The acidity of bio-oil varied between 12.3 and 257.6 mg KOH/g, decreasing exponentially with temperature, while that of the aqueous phase varied between 17.9 and 118.9 mg KOH/g, showing an exponential decay behavior with temperature and demonstrating that higher temperatures favor not only the yield of bio-oil but also bio-oils with lower acidity. For the experiments with KOH activation, the GC-MS of bio-oil identified the presence of hydrocarbons (alkanes, alkenes, cycloalkanes, cycloalkenes, and aromatics) and oxygenates (carboxylic acids, phenols, ketones, and esters). The concentration of hydrocarbons varied between 10.19 and 25.71 (area.%), increasing with temperature, while that of oxygenates varied between 52.69 and 72.15 (area.%), decreasing with temperature. For the experiments with constant temperature, the concentrations of hydrocarbons in bio-oil increased exponentially with molarity, while those of oxygenates decreased exponentially, showing that higher molarities favor the formation of hydrocarbons in bio-oil. The antioxidant activity of bio-oils decreases with increasing temperature, as the content of phenolic compounds decreases, and it decreases with increasing KOH molarity, as higher molarities favor the formation of hydrocarbons. Finally, it can be concluded that chemical activation of açaí seeds with KOH favors not only the yield of bio-oil but also the content of hydrocarbons. The study of process variables is of utmost importance in order to clearly assess reaction mechanisms, economic viability, and design goals that could be derived from chemically activated biomass pyrolysis processes. The study of the antioxidant properties of pyrolysis oils provides insight into new products derived from biomass pyrolysis.

The species Trattinnickia rhoifolia Willd, (T. rhoifolia), which belongs to the Burseraceae family, is widely used in ethnopharmacological cultural practices by traditional Amazonian people for anti-inflammatory purposes, sometimes as their only therapeutic resource. Although it is used in teas, infusions, macerations and in food, the species is still unexplored in regard to its pharmacophoric potential and chemical profile. Therefore, the aim of this study was to conduct a phytochemical characterization of the hydroethanolic extract of T. rhoifolia leaves (HELTr) and to evaluate the acute toxicity and anti-inflammatory activity of this species using zebrafish (Danio rerio). The extract was analyzed by gas chromatography–mass spectrometry (GC-MS). The evaluation of the acute toxicity of the HELTr in adult zebrafish was determined using the limit test (2000 mg/kg), with behavioral and histopathological evaluations, in addition to the analysis of the anti-inflammatory potential of HELTr in carrageenan-induced abdominal edema, followed by the use of the computational method of molecular docking. The phytochemical profile of the species is chemically diverse, suggesting the presence of the fatty acids, ester, alcohol and benzoic acid classes, including propanoic acid, ethyl ester and hexadecanoic acid. In the studies of zebrafish performed according to the index of histopathological changes (IHC), the HELTr did not demonstrate toxicity in the behavioral and histopathological assessments, since the vital organs remained unchanged. Carrageenan-induced abdominal edema was significantly reduced at all HELTr doses (100, 200 and 500 mg/kg) in relation to the negative control, dimethyl sulfoxide (DMSO), while the 200 mg/kg dose showed significant anti-inflammatory activity in relation to the positive control (indomethacin). With these activities being confirmed by molecular docking studies, they showed a good profile for the inhibition of the enzyme Cyclooxygenase-2 (COX-2), as the interactions established at the sites of the receptors used in the docking study were similar to the controls (RCX, IMN and CEL). Therefore, the HELTr has an acceptable degree of safety for acute toxicity, defined in the analysis of behavioral changes, mortality and histopathology, with a significant anti-inflammatory action in zebrafish at all doses, which demonstrates the high pharmacophoric potential of the species. These results may direct future applications and drug development but still require further elucidation.

Açaí (Euterpe oleracea Mart.) is a native fruit of the Amazon, and its production chain is centered in the state of Pará. The processing of açaí fruits generates large amounts of solid waste, which can pose serious risks to the environment if not used and managed properly. The novelty of this research lies in the fact that until this moment, no research had been reported in the literature on the pyrolysis of açaí fibers and the chemical composition of the aqueous phase, making possible a broad set of applications including biogas production. The present research proposes a study of the pyrolysis of açaí seeds and fibers and the physicochemical and compositional characterization of the aqueous phase products. In this way, açaí processing residues were collected in the city of Belém, PA. The seeds and fibers were dried and impregnated with NaOH solutions, and subsequently subjected to pyrolysis on a laboratory scale. The liquid products from pyrolysis were characterized through acidity index analysis, FT-IR, and gas chromatography. The increase in the concentration of the impregnating agent led to an increase in bio-oil yield from both the seeds (ranging from 3.3% to 6.6%) and the fibers (ranging from 1.2% to 3.7%). The yield in the aqueous phase showed an inverse behavior, decreasing as the concentration of NaOH increased, both in the seeds (ranging from 41% to 37.5%) and the fibers (ranging from 33.7% to 21.2%). High acidity levels were found in the liquid products studied, which decreased as the concentration of the impregnating agent increased. The increase in the concentration of the impregnating agent (NaOH) influenced the chemical composition of the obtained liquid products, leading to a decrease in oxygenated compounds and an increase in nitrogenous compounds in both experimental matrices, which was also evidenced by the reduction in acidity.

This research explores the depolymerization of waste polymethyl methacrylate (PMMAW) from dental material in fixed bed semi-batch reactors, focusing on three production scales: laboratory, technical and pilot. The study investigates the thermal degradation mechanism and kinetics of PMMAW through thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, revealing a two-step degradation process. The heat flow during PMMAW decomposition is measured by DSC, providing essential parameters for designing pyrolysis processes. The results demonstrate the potential of DSC for energetic analysis and process design, with attention to standardization challenges. Material balance analysis across the production scales reveals a temperature gradient across the fixed bed negatively impacting liquid yield and methyl methacrylate (MMA) concentration. Reactor load and power load variables are introduced, demonstrating decreased temperature with increased process scale. The study identifies the influence of temperature on MMA concentration in the liquid fraction, emphasizing the importance of controlling temperature for efficient depolymerization. Furthermore, the research highlights the formation of aromatic hydrocarbons from the remaining char, indicating a shift in liquid composition during the depolymerization process. The study concludes that lower temperatures below 450 °C favor liquid fractions rich in MMA, suggesting the benefits of lower temperatures and slower heating rates in semi-batch depolymerization. The findings contribute to a novel approach for analyzing pyrolysis processes, emphasizing reactor design and economic considerations for recycling viability. Future research aims to refine and standardize the analysis and design protocols for pyrolysis and similar processes.

Oxygenated compounds such as acids in bio-oils (BO) have been related to the corrosion of metals and their storage instability when applied as fuels. Therefore, upgrading BO by removing acids (deacidification) can be a valuable technique to reduce corrosivity using specific separation processes. Therefore, the objective of this paper was to evaluate the effect of the water content in the solvent (aqueous methanol), the carboxylic acid content in the BO and extraction temperature on the deacidification process by liquid–liquid extraction (LLE), as well as the effect of the same parameters on the quality of the deacidified BO through physical–chemical and GC-MS analyses. The results show that an increase in the water content (5 to 25%) in the solvent and an increase in the carboxylic acids content (24.38 to 51.56 mg KOH/g) in the BO reduce the solvent’s capacity to extract carboxylic acids while increasing the temperature (25 to 35 °C) of the deacidification process promoted an increase in its capacity to remove them. Consequently, the highest deacidification efficiency (72.65%) is achieved with 5% water in methanol at 25 °C for BO1 (TAN = 24.38 mg KOH/g). Therefore, the deacidification process through LLE using aqueous methanol contributed significantly to BO upgrading.

This study aims to systematically investigate the combined effect of chemical activation of açaí seeds (Euterpe oleracea Mart.), with an aqueous sodium hydroxide (NaOH) solution at 2 mol·L−1, and process temperature by pyrolysis of alkaline activated açaí seeds on the yield of reaction products (bio-oil, gas, H2O, and biochar), physicochemical properties (acid value, density, and kinematic viscosity) and chemical composition (hydrocarbons and oxygenates) of bio-oil. Catalytic pyrolysis was carried out in a 143 L reactor at temperatures of 350 °C, 400 °C, and 450 °C, 1.0 atmosphere, operating in batch mode. The NaOH activation played a crucial role in modifying the thermal degradation pathway of the biomass, promoting the formation of specific chemical structures and altering the product yields. NaOH acted as a catalyst, enhancing the deoxygenation of the biomass and stimulating the formation of hydrocarbons. As a result, the yields of bio-oil, water, biochar, and gas varied from 5.77 to 7.20% (by mass), 14.90 to 19.77% (by mass), 41 to 54% (by mass), and 25.33 to 32.03%, respectively, influenced by the increase in temperature. FT-IR analyses indicated the presence of characteristic chemical functions of hydrocarbons (alkanes, alkenes, and aromatics) and oxygenated compounds (phenols, cresols, ketones, esters, carboxylic acids, aldehydes, and furans), with an intensification of hydrocarbon signals at higher temperatures. GC-MS analysis identified hydrocarbons and oxygenated compounds as the main chemical classes in the bio-oil, showing a strong dependence on pyrolysis temperature. It was observed that hydrocarbon concentration in bio-oil increased from 49.7% to 57.88% (area) with increasing temperature, while the concentration of oxygenated compounds decreased from 13.88% to 6.69% (area), demonstrating that NaOH activation, combined with temperature elevation, favors the formation of hydrocarbons and the reduction of oxygenated compounds, thereby improving the quality of the produced bio-oil.