Presence Of Sunlight Research Articles

New routes for the synthesis of unsymmetrical diarylselenides: Effect of heat, light and ultrasound

Herein, we report the photochemical coupling of diphenyldiselenides with substituted phenylhydrazine hydrochloride without catalyst. The protocol was developed not only in presence of sunlight and UV light but also under thermal condition for comparison study. Moreover, ultrasound assisted new catalytic protocol was developed using Ni(II)/L-proline system in DMSO with the advantage of shorter reaction time compared to earlier reports. We have also developed a new C-Se cross coupling reaction where phenylselenyl chloride and arylhydrazine hydrochlorides were effectively coupled using developed catalytic system.

Visible Light Assisted Enhanced Photocatalytic Performance of ZnO/NiO Nanocomposites Prepared by Chemical Co-Precipitation Method

A series of Ni1-xZnxO (x═0.1 to 0.4) nanocomposites is synthesized by facile chemical coprecipitation method. The structural analysis is carried out using X-ray diffraction (XRD) graph which reveals both cubic (NiO) and hexagonal (ZnO) phases. Chemical bonding, morphology, elemental composition and optical properties of prepared nanocomposites are investigated by Fourier Transform Infrared (FTIR) Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), and UV-Vis spectroscopy respectively. FESEM micrographs show the formation of nanorods at higher concentration of zinc content. Introducing higher amount of Zn, optical band gap of composites is considerably reduced. Furthermore, solutions of Rose Bengal (RB) and Methylene Blue (MB) dyes are used to investigate the photocatalytic ability of synthesized samples in the presence of sunlight. It was found that the percentage degradation of dye concentration increases with irradiation time and also with the increase in concentration of zinc in prepared samples.

Green synthesis, cytotoxicity, antioxidant and photocatalytic activity of CeO2 nanoparticles mediated via orange peel extract (OPE)

The advancement of metal oxide nanomaterials via green synthesis protocol proved leading tools for nanotechnology applications especially as drug deliver carriers, biosensors and clinical pharmaceutical. The aim of the current study was to synthesize cerium dioxide nanoparticles (CeO2 NPs) using orange peel extract (OPE) and evaluate its enactment for the antioxidant, anticancer and photocatalytic activities. Structural and morphological investigations of green synthesized CeO2 NPs was examined by using x-ray diffraction (XRD), transmission electron Microscopy (TEM), Fourier transform infrared (FTIR) spectra, Raman spectroscopy and ultraviolet-visible spectroscopy (UV–vis). Further, cytotoxicity and ROS activity of green synthesized CeO2 NPs exposed against cervical cancerous cells (HeLa). Green synthesized CeO2 NPs revealed the considerable antioxidant activity and hold effective methylene blue (MB) dye degradation in the presence of sunlight.

Photocatalytic degradation of Irgalite violet dye using nickel ferrite nanoparticles

Abstract Nanotechnologies have prominent applications in the field of science and technology owing to their size-tunable properties providing a promising approach for degradation of various pollutants. In this scenario, the present work aims to study the effect of nickel ferrite nanoparticles on the degradation of Irgalite violet dye by Fenton's reaction using oxalic acid as an oxidizing agent in the presence of sunlight. The effect of pH and adsorbent dosage on the rate of dye degradation was monitored. Based on these studies it was observed that 99% dye degradation was achieved for catalyst dosage of 0.2 g, 400 ppm dye concentration and 2.0 mM oxalic acid at pH 3.0 within 60 min. The studies reveal that the degradation follows pseudo-first-order kinetics and the catalyst reusability remained constant almost for five cycles. Further, nickel ferrite nanoparticles are proven to be an efficient alternative for the removal of dyes from coloured solutions.

CHARACTERIZATION-PERFORMANCE OF ZnO AND ZnO/ZnFe2O4 CATALYST USING ARTIFICIAL AND SOLAR LIGHT FOR MERCURY (II) REDUCTION

This study describes the application of ZnO commercial oxide and ZnO/ZnFe2O4 mixed oxides to reduce the mercury ion (Hg2+) in the aqueous phase. The catalysts synthesized were characterized by thermogravimetric analysis, adsorption and desorption of N2, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, photoacoustic spectroscopy and Mössbauer spectroscopy. The heterogeneous photocatalysis process was studied in synthetic effluent treatment containing mercury chloride (HgCl2) in a batch and solar reactor. The results indicated that commercial ZnO catalyst totally reduced the Hg (II), in all conditions and reaction systems studied. On the other hand, for the mixed oxides (ZnO/ZnFe2O4), there was a decrease in the reduction efficiency in the batch reactor, indicating no ability to reduce Hg(II) in the presence of sunlight.

Visible light photocatalysis of methylene blue using cobalt substituted cubic NiO nanoparticles

This study reports the facile co-precipitation synthesis of pure and cobalt substituted NiO nanoparticles. The cubic crystalline structure of the synthesized NiO nanoparticles was confirmed through X-ray diffraction. Structural behaviour, morphological, elemental composition and optical properties of the prepared nanoparticles are investigated by Fourier transform infrared spectroscopy, scanning electron microscopy-energy dispersive spectrum, transmission electron microscopy and UV–Vis spectroscopy. The optical band gap is determined using UV spectra and is observed to decrease with an increase in cobalt ion concentration. Furthermore, methylene blue dye solution has been used to investigate the photocatalytic ability of the synthesized nanoparticles in the presence of sunlight. It is found that percentage degradation in dye concentration increases with irradiation time and also with the increase in the concentration of doping of cobalt in NiO. The dye solution is found to degrade to 94% within 50 min in the presence of solar radiation and the $$\hbox {Ni}_{0.6}\hbox {Co}_{0.4}\hbox {O}$$ sample.

Concentration dependent effect of humic acid on the transformations of silver nanoparticles

Influence of humic acid (HA) concentration on the colloidal stability and dissolution of silver nanoparticles (AgNPs) was evaluated in a series of long-term experiments. The stability of freshly synthesized and uncoated AgNPs was investigated as a function of HA concentration (0–250 mg/L). In the absence of HA, AgNPs underwent oxidative dissolution and aggregation disturbing the colloidal stability of AgNPs. In the HA concentration range of 1–20 mg/L, HA stabilized AgNPs due to the inhibition of the release of ionic Ag ensuring the persistence of AgNPs in the aquatic environment for a longer period. At higher concentrations of HA (20–250 mg/L) in the soil environment, AgNPs were wrapped by the HA molecules, increasing the hydrodynamic diameter of the AgNPs. Due to the suppression of dissolution of AgNPs, primary particles remained stable in the environment for a prolonged period with no change in the primary particle size and morphology. Furthermore, it was observed that ionic Ag in the solution can be reduced to form fresh, secondary AgNPs at the lower levels of HA in the aquatic environment, in the presence of sunlight. This study is important in understanding the role of HA on the stability of AgNPs in the natural environment.

Performance Evaluation of Diethylamine to the Removal of Polycyclic Aromatic Hydrocarbons (PAHs) from Polluted Soils with Sunlight

In the present study, the removal of polycyclic aromatic hydrocarbon (PAH) compounds from contaminated soil with solar radiation was investigated. In this context, the effect of diethylamine (DEA) as a photo-sensitizer on the photodegradation of PAH was examined, and the ring distributions of the PAHs were determined. DEA was added to samples at the doses of 1%, 10%, and 20% of dry weight of soil, and samples were kept in ambient air for 24 hours. Concentrations of Σ12PAH in soil samples were detected with Gas Chromatography-Mass Spectrophotometer (GC-MS) as 4382 ng/g dry matter (DM). The total PAH content of the soil decreased by 45% in the presence of sunlight without using DEA. Σ12PAH removal efficiency was at the maximum level of 76% with the addition of 1% DEA to the soil. The increase in the dose of DEA adversely affected the PAH elimination process, and minimum removal ratio (32%) was obtained in the sample containing 20% DEA. The use of DEA has contributed to the elimination of most 3-ring PAH species. Heavy species, 5-6 ring compounds, have not been removed in the presence of sunlight.

Titanate based photocatalysts for climate-efficient water treatment

The sol-gel dip-coating method is a simple method to synthesize TiO2 thin film, using titanium butoxide and hydrogen peroxide. In this study in addition to TiO2 thin film, the photocatalytic activity of its intermediate products, titanium peroxide gel and ambient dried titanium peroxide film, was also evaluated. The titanium peroxide gel was used directly after gelation, ambient dried titanium peroxide film coated on glass rings was used without thermal treatment and anatase TiO2 thin film was used after thermal treatment at 500oC. These photocatalysts were characterized by different characterization techniques and their adsorption and photocatalytic activity were evaluated by using methylene blue as a model pollutant. All three photocatalysts adsorbed the selected dye model and degraded it in the presence of sunlight but with different removal rate. It was found that the gel had the highest removal rate followed by ambient dried titanium peroxide film and TiO2 thin film. However, this sequence was vice versa in the case of photocatalyst life span when the photocatalysts were reused. The photocatalytic study showed that all three photocatalysts are very effective for 100% degradation of methylene blue within 5-60 minutes under sunlight irradiation. This can be a breakthrough of using titanate based photocatalyst for the cost-effective adsorption and photocatalytic degradation of pollutants based on the climate and availability of sunlight. The energy cost analysis was performed for the catalyst based on electrical power consumption. The calculated power cost for synthesizing TiO2 thin film was approximately 0.9 $/kWh. However, the energy required for the synthesis of two other catalysts was zero, means there is no money needed to be spent on electricity.

Photocatalytic efficiency of molybdenum-doped zinc oxide nanoparticles in treating landfill leachate

Among various techniques available for leachate treatment, nano-photocatalytic-based techniques have been considered as efficient. The photocatalytic leachate treatment using nanoparticles of zinc oxide doped with molybdenum oxide was performed in the presence of sunlight at a laboratory scale. The molybdenum oxide doped ZnO nanoparticles were synthesized. The properties of nanoparticle were analyzed by using FTIR, SEM, and XRD. Then the parameters such as pH (3, 5, 7, 9, & 11), concentration of nanoparticles (0.5, 1, 2 and 3 g/l), concentration of leachate with dilution (1:10, 1:25, 1:50 and 1:100), and contact time (15, 30, 45, 60, 90, & 120 min) were measured to determine the removal of COD and turbidity. The analysis indicated that nanoparticle size was appropriate and acceptable. Electron microscope images also showed that the nanoparticle shape was hexagonal. The optimum value of pH was 5. It was found that increasing the concentration of nanoparticles enhances the efficiency of the process, the concentration of nanoparticles from 0.5 to 2 g/l at 60 min of contact time, and the efficiency from 34.8 to 55.6%, and increasing in contact time decreases the COD and turbidity leachate. Enhancing the initial concentration of leachate reduces the treatment efficiency of landfill leachate.

AIR POLLUTANTS MITIGATION BY USING VARIOUS FORMS OF PHOTOCATALYTIC CEMENTITIOUS COATINGS MATERIALS

Nitric oxide generated from various sources like car combustion is one of the most surrounding pollutants, which can be transferred from one form to another in the presence of sunlight. Titanium dioxide considered one of the most environmentally friendly active photocatalytics that can be used with building materials safely and effectively to react with nitric oxides. To study the possibility for the reduction of air pollutants like nitric oxides, two types of substrates coatings were prepared. First, mixing nano particles of TiO2 with cement paste in two percents 3% and 6%. Second, mortar substrates coated with nano TiO2 aqueous solution. Two coating methods have been used dip and spray. A laboratory test procedure was adopted to assess the performance of the prepared photoactive specimens. The specimens were subjected to NO gas and there efficiency in gas removal was monitored with time. Results showed the effectivity of coating building materials with titanium dioxide, the removal of gaseous pollutants like nitric oxide reached to 98.85% when spary and dip methods are used. Mixing nano titanium with a percent of 3% was also efficient in the removal of nitric oxides, the removal reached to 97%. It was concluded that spray method was more practical to be used.

Inactivation and Loss of Infectivity of Enterovirus 70 by Solar Irradiation

Enterovirus 70 (EV70) is an emerging viral pathogen that remains viable in final treated effluent. Solar irradiation is, therefore, explored as a low-cost natural disinfection strategy to mitigate potential concerns. EV70 was exposed to simulated sunlight for 24 h at a fluence rate of 28.67 J/cm2/h in three different water matrices, namely, phosphate-buffered saline (PBS), treated wastewater effluent, and chlorinated effluent. In the presence of sunlight, EV70 decreased in infectivity by 1.7 log, 1.0 log, and 1.3 log in PBS, effluent, and chlorinated effluent, respectively. Irradiated EV70 was further introduced to host cell lines and was unable to infect the cell lines. In contrast, EV70 in dark microcosms replicated to titers 13.5, 3.3, and 4.2 times the initial inoculum. The reduction in EV70 infectivity was accompanied by a reduction in viral binding capacity to Vero cells. In addition, genome sequencing analysis revealed five nonsynonymous nucleotide substitutions in irradiated viruses after 10 days of infection in Vero cells, resulting in amino acid substitutions: Lys14Glu in the VP4 protein, Ala201Val in VP2, Gly71Ser in VP3, Glu50Gln in VP1, and Ile47Leu in 3Cpro. Overall, solar irradiation resulted in EV70 inactivation and an inhibition of viral activity in all parameters studied.

Promoting photocatalytic nitrogen fixation with alkali metal cations and plasmonic nanocrystals.

Photocatalytic nitrogen fixation can produce ammonia from nitrogen and water under ambient conditions in the presence of sunlight. Here, we report that alkali metal cations (Li+, Na+, and K+) can significantly promote nitrogen activation and plasmonic nanocrystals (Au and Ag) can sensitize photocatalysts under visible light. The ammonia yield and selectivity on Au/P25 under UV-vis irradiation could be increased from 0.085 mmol g-1 h-1 and 75% to 0.43 mmol g-1 h-1 and 94.5% when promoted by K+, showing a visible-light-driven activity of 0.14 mmol g-1 h-1 and an AQE of 0.62% at 550 nm. The activity could be further increased to 1.02 (UV-vis) and 0.32 (visible) mmol g-1 h-1 with AQE of 0.93% at 550 nm with methanol added as the sacrificial agent. This strategy could be applied to a series of photocatalysts (e.g. TiO2, ZnO, and BiOBr) and may represent a general approach for designing efficient nitrogen fixation processes.

Experiments on filtering nano-aerosols from vehicular and atmospheric pollutants under dominant diffusion using nanofiber filter

Nano-aerosols of size 100 nm and below are manifested everywhere in various urban micro-environments. In outdoor, the vehicular emission during traffic jam can release nano-aerosols with concentration above 200 million/m3 (200/cm3). Superimposed on vehicular emission are smog particles, around 10–50 nm, generated from the photochemical reaction of hydrocarbon and NOx in the presence of sunlight. These nano-aerosols, by virtue of their small sizes, can be inhaled readily into our bodies leading possibly to various chronic diseases. Air-borne viruses from influenza to epidemic viruses, which can lead to acute sickness and even death, are also in the same size range of 100 nm.Despite microfibers are being commonly used today in filters, there has been limited studies on filtration of real aerosols using microfiber filters, let alone nanofibrous filters, as most studies used simulated aerosols (e.g. sodium chloride) or test dust. Also, in standard sodium chloride test, only monodispersed aerosol size is allowed to challenge the filter. On the other hand, in reality aerosols of all sizes challenge simultaneously the filter. In this study, for the first time we have used nanofiber filter in a portable test filter set-up to filter polydispersed aerosols from the micro-environment near busy traffic area where aerosols comprise of both vehicular and atmospheric pollutants with size range between 10 and 400 nm. Real-time measurements are carried out with the portable test filter. The test results are compared to the theoretical correlation from Payet with diffusion correction at small Peclet number (Pe). We have found good comparison between test results with theoretical correlations using equivalent aerodynamic diameter for the aerosols with face velocity from 1 to 11 cm/s. A new dimensionless parameter, specific filter resistance (also established independently by Buckingham-π approach), is defined for the first time. It measures the flow drag on fibers to the amount of fibers present in the filter, the lower is the specific filter resistance the better is the filter. For our test condition, it is approximately 1.0–1.2. We have also improved the filtration efficiency of the filter by increasing the fiber basis weight by stacking up two layers of nanofibers. We have demonstrated that the efficiency increases while both the quality factor and specific filter resistance remain constant. We have also investigated the single fiber efficiency due to diffusion and found that at low velocity and low Peclet number (Pe < 10), the test results agree well with the theoretical prediction. On the other hand, at higher face velocity (>0.07 m/s) and large Peclet number (>10), there is small deviation from the theory, which is probably due to the smaller aerosols collecting by the larger aerosols upstream of the filter with an airstream consisting of polydispersed aerosol distribution challenging the filter. This has not been realized previously as tests conducted were mostly using monodispersed aerosol size distribution for which aerosol-aerosol interaction was absent.

Algae induce siderophore biosynthesis in the freshwater bacterium Cupriavidus necator H16.

Cupriachelin is a photoreactive lipopeptide siderophore produced by the freshwater bacterium Cupriavidus necator H16. In the presence of sunlight, the iron-loaded siderophore undergoes photolytic cleavage, thereby releasing solubilized iron into the environment. This iron is not only available to the siderophore producer, but also to the surrounding microbial community. In this study, the cupriachelin-based interaction between C. necator H16 and the freshwater diatom Navicula pelliculosa was investigated. A reporter strain of the bacterium was constructed to study differential expression levels of the cupriachelin biosynthesis gene cucJ in response to varying environmental conditions. Not only iron starvation, but also culture supernatants of N. pelliculosa were found to induce cupriachelin biosynthesis. The transcription factors involved in this differential gene expression were identified using DNA-protein pulldown assays. Besides the well-characterized ferric uptake regulator, a two-component system was found to tune the expression of cupriachelin biosynthesis genes in the presence of diatom supernatants.

New insight of ozone pollution impact from flare emissions of chemical plant start-up operations

Flaring is a common and necessary operation for chemical industries, which is designed to manage dangerous process overpressure scenarios or to release and destroy off-spec products during chemical plant upsets or turnarounds. However, excessive flaring can emit large quantities of VOCs and NOx into the atmosphere, which will cause transient and localized ozone pollution events in the presence of sunlight. The objective of this study was to quantify the impact to regional air-quality due to flare emissions from chemical plant start-up operations through the coupling of dynamic process simulations via Aspen Plus and air-quality simulations via CAMx. Simulation results from case studies have indicated that the corresponding ozone increments can vary significantly from 0.2 ppb to 17.8 ppb under different temporal and spatial factors, including the start-up starting hour, starting day, and plant location. Additional ozone sensitivity simulations have also indicated that the corresponding ozone increments are higher when the plant is located in a VOC-limited area than that in a NOx-limited area. The results from this study have delivered a cost-effective air-quality control practice for plant start-ups with a minimum air-quality impact through selecting the optimal starting time within the allowable ranges. The practice has significant potential to benefit all stakeholders, including environmental agencies, chemical industries, and local communities.

Green Synthesis of Selenium Nanoparticle Using Leaves Extract of Withania somnifera and Its Biological Applications and Photocatalytic Activities

The green Se NPs (selenium nanoparticles) are formed by simple mixing of Withania somnifera (W. somnifera) leaves extract and selenious acid (H2SeO3) solution. This mixture was stirred which gave a dispersion of Se NPs conjugated with W. somnifera secondary metabolites. The work was focused to determine the phytochemical analysis of leaves extract, green synthesis, its characterization and its applications. Screening analysis showed enormous phytoconstituents in leaves aqueous extract and simultaneously, the synthesized Se NPs by FT-IR spectrum confirm the presence of functional groups which were associated with bioactive molecules. The total flavonoid, phenolic and tannin contents in the aqueous extract were found to be 12.74, 40.54, and 156.33 μg/mg respectively. The suspension solution confirms the formation of Se NPs showed (310 nm) by UV analysis. X-ray diffraction study exhibits the amorphous nature of Se NPs. Se NPs were spherical in shape within the diameter range of 45–90 nm by FE-SEM. The intense, narrow width of selenium has high purity and was identified using EDX. The TEM analysis exhibited the amorphous nature of particles. Green synthesized Se NPs were found to possess significant antioxidant activity (IC50 – 14.81 μg/mg) and considerable antibacterial activity on Bacillus subtilis (12 mm), Klebsiella pneumoniae (14 mm) and Staphylococcus aureus (19.66 mm). Antiproliferative effects of Se NPs possess great growth control against A549 cells (IC50 at 25 μg/ml). Se NPs exhibit efficient methylene blue (MB) dye degradation in the presence of sunlight. The present results support the advantages of green method for the production of Se NPs having potential activities.Graphical Highlights• Withania somnifera leaves extract possesses active phytoconstituents and acts as reducing agents for the preparation of Se NPs and the capping by the phytoconstituents providing stability to Se NPs as evident from FT-IR studies.• The green synthesized metal nanoparticle has emerged at low cost, simpler and better choice than physical and chemical methods.• Green synthesized Se NPs were found to be almost spherical in shape with particle size around 40–90 nm, selenium has high purity and crystalline nature was identified using EDX and XRD.• The DPPH scavenging analysis of the amorphous Se NPs has significant antioxidant activity and serves as a potential antibacterial agent to treat diseases caused by bacteria.• Antiproliferative activity results suggest that Se NPs possess higher growth control against A549 lung carcinoma cancer cells (IC50 at 25 μg/ml) which indicated their potential in medical applications.• The photocatalytic study concludes that these Se NPs have efficiency to degrade MB under sunlight irradiation. Therefore, they can find application in water treatment plants and textile industries.

Green synthesis of silver nanoparticles using Nardostachys jatamansi and evaluation of its anti-biofilm effect against classical colonizers

In this communication, we present the green synthesis of silver nanoparticles (AgNPs) using medicinally important Nardostachys jatamansi rhizome extract in the presence of sunlight. UV–vis spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Transmission electron microscope (TEM) and Energy dispersive X-ray analysis (EDX) were employed to characterize the synthesized AgNPs. UV–visible spectroscopic studies confirmed the presence of biosynthesized AgNPs. Transmission Electron Microscopic studies revealed the structure of spherical AgNPs in the diameter range of 10–15 nm. Energy dispersive X-ray analysis and elemental mapping clearly confirmed the presence of silver in AgNPs samples. Interestingly, biomolecules functionalised AgNPs exhibited a remarkable antioxidant, anti-inflammatory, and anti-biofilm activities and hence biosynthesized AgNPs from N. jatamansi can be used as a promising biomaterial for biomedical applications.

Facile immobilization of Ag nanoparticles on g-C3N4/V2O5 surface for enhancement of post-illumination, catalytic, and photocatalytic activity removal of organic and inorganic pollutants

Multifunctional nanocatalyst that is efficient in removal of organic and inorganic contaminant under different light illumination is highly anticipated. Here, we report a ternary nanocatalyst that has catalytic, photocatalytic and a good photocatalytic memory for oxidation/reduction processes. The ternary nanocatalyst was prepared by the facile immobilization of Ag NPs on the V2O5/g-C3N4 surface by photodeposition method. The morphology of the ternary nanostructure shows the uniform distribution of V2O5 on the g-C3N4 surface decorated with 20–30 nm average diameters of Ag NPs. The prepared catalyst exhibits unique catalytic, photocatalytic and post-oxidation/reduction ability for removal of organic, p-nitrophenol (NP), methylene blue (MB) and inorganic (Cr+6) water pollutants. The catalytic reduction conversion of NP was completed in 60 min was ascribed to the electron relay mechanism, while the photocatalytic hydrogenation of NP was achieved in only 8 min and assigned to the solid Z-scheme electron-hole pair generation facilitated by the good electron storage of Ag NPs. On the other hand, the electron storage memory of the photocatalyst was responsible for the post- oxidation/reduction of MB/Cr+6 respectively. Oxidation of MB increased by 27%, while the Reduction of Cr+6 to Cr+3 was enhanced by 28% after sunlight post-illumination. The proposed ternary nanocatalyst provide an efficient tool for the removal of water pollutants from different sources during the daytime: in presence of sunlight or after the sunset.

Oxidation of benzoic acid from biomass burning in atmospheric waters

This work evaluates the degradation of benzoic acid, a tracer from biomass burning, by different oxidation agents (Fe (III); H2O2; sunlight; and combinations of the previous ones) in model solutions and in real atmospheric waters. The extent of reactions was assessed by Ultraviolet–Visible and molecular fluorescence spectroscopies. The oxidation of benzoic acid occurred with the chemical oxidants Fe (III), H2O2, Fe (III) and H2O2 simultaneously in the presence of sunlight, and with Fe (III) and H2O2 simultaneously in the absence of light. The decrease of the pH value from neutral to acid for atmospheric waters generally increased the extent of oxidation. Sunlight was an important oxidation agent, and its combination with chemical oxidants increased the oxidation rate of benzoic acid, possibly due to the photogeneration of hydroxyl radicals. The results also suggested the occurrence of direct and indirect photolysis of benzoic acid in atmospheric waters. Moreover, the oxidation of benzoic acid produced new and more complex chromophoric compounds, which were then degraded. In addition, the nocturnal period is not sufficient for the full degradation of benzoic acid and of the intermediates formed by Fenton-like oxidation. The diurnal period may be enough for their full degradation through photo-Fenton-like oxidation, but this depends on the composition of the atmospheric waters, namely of the chromophoric content. Thus, this study highlights that benzoic acid from biomass burning, and its derivatives, may persist in atmospheric waters for periods of longer than one day, becoming available for other reactions, and may also affect the terrestrial and aquatic ecosystems through the wet depositions.