Photochemical Oxidation Research Articles

Batch to Continuous Flow Visible‐Light Photooxidations Using Alumina Supported Hydroxyanthraquinones

AbstractThe discovery of new environmentally friendly recyclable photosensitizers is key to develop future applications in photooxidation chemistry. We report here the evaluation of a set of differently substituted biobased hydroxyanthraquinones in the context of visible light mediated singlet oxygen (1O2) photochemistry. This class of compounds is efficiently immobilized on alumina supports, which offers a simple way of removing them from the reaction mixture downstream. An integrated process using a flow reactor with a fixed catalytic bed is also evaluated and its performance is compared with homogeneous conditions.

Enhancement of Charge Separation in the Photochemical Two-Electron Water Oxidation by Sn-Porphyrins Covalently Bound through Silylation with Flexible Bridging Moieties on SnO2 Nanoparticles

Enhancement of Charge Separation in the Photochemical Two-Electron Water Oxidation by Sn-Porphyrins Covalently Bound through Silylation with Flexible Bridging Moieties on SnO₂ Nanoparticles

Effects of relative humidity on atmospheric organosulfur species derived from photooxidation and nocturnal chemistry in a forest environment

The molecular composition of organic aerosols in ambient PM2.5 was investigated at the northern foothills of Qinling Mountain region in central China during the summer of 2022. The molecular characteristics of organic matter were analyzed using ultrahigh performance liquid chromatography coupled with high-resolution Orbitrap mass spectrometry. The number of molecular formula assignments was dominated by organosulfur species (OrgS, on average 28–47% in total). Both the number and peak area of OrgS increased significantly with higher relative humidity (RH), while those of CHO and CHON species decreased, indicating the different impacts of RH on individual organic groups. The entire study period was divided into two distinct stages, including a low RH and a high RH period (LRH and HRH). The enhanced formation of CHOS with O>7 in HRH was primarily attributed to photochemical oxidation, whereas the increase in CHONS with O>7 was driven by enhanced NO3 radical-initiated oxidation under elevated RH conditions. Nearly 50% of OrgS presented only in HRH had aliphatic structures with C≥9. Although isoprene-derived organosulfates dominated the peak area across the entire period, the monoterpenes and long-chain alkanes-derived organosulfates largely increased in HRH. The strong correlations between aerosol liquid water content and OrgS containing high oxygen content (O>7) indicate that aqueous-phase reactions played a crucial role in multigenerational oxidation of OrgS. This study highlights the important effects of RH on the formation of OrgS, particularly for organosulfates derived from monoterpenes and long-chain alkanes.

Recycling Fly Ash into Lightweight Aggregate: Life Cycle Assessment and Economic Evaluation of Waste Disposal

This study analyzed environmental impacts and economic feasibility to evaluate whether recycling fly ash, which has rarely been addressed in previous studies, as a raw material for lightweight aggregates can be a sustainable waste management alternative. This study presents a comparative analysis of three disposal scenarios: landfill disposal, recycling as cement raw material, and recycling as lightweight aggregate raw material. Nine environmental impacts were assessed through life cycle assessment (LCA): acidification, global warming, eutrophication, photochemical oxidation, stratospheric ozone depletion, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, and terrestrial ecotoxicity. The results showed that the landfill disposal scenario posed the greatest threat to global warming, eutrophication, and marine aquatic ecotoxicity, while the cement scenario had the greatest impact on stratospheric ozone depletion, human toxicity, and other ecotoxicity items while recycling as lightweight aggregate showed the lowest environmental impacts in most items except acidification and photochemical oxidation. Life cycle costing (LCC) analysis was also performed to compare the economic aspects of each scenario. The lightweight aggregate scenario is more energy-intensive and costly, but it has significant economic benefits due to the significant revenues from the products produced. Therefore, even though the cost is high, this scenario is considered economically advantageous. This study highlights that recycling fly ash into lightweight aggregate reduces environmental impacts, provides economic benefits, and is a better alternative to landfilling and recycling cement raw materials. It will also contribute to promoting sustainable practices of fly ash recycling.

Pemantauan Kualitas Udara Ambien pada Pekerjaan Preservasi Jalan

Heavy traffic, especially from large vehicles passing through the road, can potentially cause congestion and increase air pollution. Ambient air quality can significantly decrease due to vehicle emissions, impacting public health and environmental quality. This study focuses on monitoring ambient air quality during road preservation work conducted along the route of Jalan Bts. Prov. Sumsel – Tempino – Pal. Sepuluh – Lingkar Timur – Sp. Sijenjang – Pel. Talang Duku in Muaro Jambi Regency.objective of this research is to analyze the ambient air quality at th road preservation work sites. The research method applied is a survey method with the selection of three locations along the road segment: 1. AMP Tempino, located at coordinates LS 01°47’01.23’’ BT 103°28’27.56’’; 2. STA 11+050 located at coordinates LS 01°45’51’’ BT 103°33’23’’; and 3. Ruas Simpang Paal. X, located at coordinates LS 01°40’12’’ BT 103°36’1’’. This research is descriptive in nature, focusing on the observation and analysis of ambient air quality according to the SNI 7119-3:2017 standard for each test parameter. The results show that at the AMP Tempino site, Particulate dust is 46,50 µg/Nm³,Sulfur Dioxide is 99,88 µg/Nm³, and Carbon Monoxide is 6563,05 µg/Nm³. The highest Nitrgen Dioxide level of 47,88 µg/Nm³ was recorded at STA 11+050, and the highest level of Photochemical Oxidants as Ozone at 41,76 µg/Nm³ was found at Ruas Simpang Paal. X. All test parameters are below the standard quality limits. Overall, Carbon Monoxide has the highest concentration across all locations, while Nitrogen Dioxide often shows the lowest values

Molecular Compositions, Mutagenicity, and Mutation Spectra of Atmospheric Oxidation Products of Alkenes and Dienes Initiated by NOx + UV or Ozone: A Structure-Activity Analysis.

Photooxidation products resulting from volatile organic compounds (VOCs) reacting with sunlight are important contributors to gas-phase air pollution. We characterized the product-weighted mutagenic potencies (rev m3 mgC-1 h-1) in Salmonella TA100 of atmospheres resulting from the hydroxyl radical (OH)-initiated photochemical oxidation of 11 C4 or C5 alkenes or dienes in the presence of nitric oxide (NO) and from the ozonolysis of four VOCs without NO (isoprene; 1,3-pentadiene; 1,4-pentadiene; and 1,3-butadiene). Irradiated atmospheres from precursors with a single C═C bond (3-methyl-1-butene, 2-methyl-1-butene, cis/trans-2-pentene, 2-methyl-2-butene, 1-butene, and 1-pentene) had low potencies (<5), whereas linear dienes with terminal C═C bonds had high potencies (50-65). Dienes with a branched structure (isoprene) or internal C═C bonds (1,3-pentadiene) had intermediate potencies (15-20). No VOCs were mutagenic without photochemical oxidation. VOCs+O3 in the dark produced less mutagenic atmospheres than photochemistry in the presence of NO. Atmospheres induced primarily C to T and C to A mutations, the main base substitutions in nonsmoker lung cancer. Atmospheres from the photooxidation of isoprene and 1,3-pentadiene also induced GG to TT, the signature mutation of peroxyacetyl nitrate. Five molecular compositions identified by Chemical Ionization Mass Spectrometry (CIMS), most containing nitrogen, correlated (r = 0.76-0.85) with the mutagenic potencies of irradiated atmospheres; most had a likely nitrate functional group. Assessment of the mutagenicity of emitted VOCs should consider VOC photooxidation products, especially dienes with terminal C═C bonds, as these products likely contribute to overall health effects from ambient air pollution.

Combining life cycle assessment and dynamic qualitative comparative analysis to analyze the environmental impacts of urban development across different provinces in China

Examining the environmental pollution landscape is a vital link for urban development. Across production, distribution, and usage stages of 24 provinces in China between 2010 and 2019, this study conducts Life Cycle Assessment and Dynamic Qualitative Comparative Analysis to explore the effects of conditional combination on environmental impact assessment indicators including Photochemical Oxidation, Eutrophication, Global Warming Potential, Human Toxicity, and Acidification. The results reveal that: (1) Shandong contributes most significantly to environmental impact assessment indicators in the production and distribution stages, while Inner Mongolia dominates the usage stage. In contrast, Beijing, Hainan, and Shanghai show lower contributions, though Hainan exhibits a rising trend in the Global Warming Potential index across all stages; (2) The production stage consistently accounts for the largest environmental impact, with notable differences in contributions from Beijing, Ningxia, Inner Mongolia, and Shanghai across the three stages; (3) Environmental impact is not driven by individual factors alone; rather, it is the combination of factors that proves influential. Complex nonlinear relationships are revealed between energy consumption patterns and environmental impacts in the production stage. The combination of transport operating distance and traffic volume has an interaction during the distribution stage. The usage stage leads only to the environmental impact of Eutrophication, which is caused by the resident population and ecological water consumption excluding residential water use. These findings present a new strategy for optimizing energy structure and water resource utilization, and emphasize the synergies to reduce the environmental impacts, providing instrumental implications for policymakers and government managers in environmental management and urbanization development.

Environmental drivers of sediment accumulation in urban sewer systems: a case study of Kyoto City, Japan

Sediment accumulation can reduce the drainage capacity of sewer systems, and thus increase the risk of urban flooding and jeopardize the safety of urban environments. The interaction between multiple environmental factors drives sedimentation in sewer systems, but this interaction is poorly understood. To fill this gap, this study examined the interaction between five categories of environmental factors (population, traffic, climate, air quality, and wastewater quality: 25 factors overall) and the effects of these factors on sediment accumulation in different sewer system structures (open channels (OCs), circular channels (CCs), junctions) in Kyoto, Japan, from 2014 to 2023. The results showed that population and traffic contributed to sediment accumulation through pollutant emission, whereas climate factors promoted sediment accumulation by enhancing wash-off and the deposition of air pollutants. Most sediment was deposited in OCs and junctions under the combined effects of climate and air quality. Air quality has a greater influence on sedimentation in the OCs than climate, and the opposite is found for Junction, whereas sedimentation in CCs was mainly influenced by the combined effects of climate, air quality, and wastewater quality. Photochemical oxidants, humidity, temperature, and vapor pressure had the greatest impact on sediment deposition in OCs and junctions, while wastewater alkalinity and NH4-N and PO4-P concentration had a non-negligible effect on CCs sedimentation. These results emphasize the key role of climate-driven wash-off and dry/wet deposition, and the localized role of wastewater quality (in CCs), in sewer sedimentation. These insights can inform the predictive modeling of sewer sedimentation during climate change.

TiO2 modified NiFe-LDH as photoanode to achieve high efficiency photochemical water oxidation reaction

With the semiconductor modified oxygen evolution (OER) catalyst as the photoanode, the solar energy can be fully utilized, and the synergistic reaction makes the OER catalyst play a great role in the photochemical (PEC) water decomposition. Herein, we adopted a one-step hydrothermal method to introduce TiO2 to form heterojunction as photoanode in a well-known NiFe-LDH electrocatalyst, which contributes to carrier separation and transfer efficiency, thereby speeding up the water oxidation reaction kinetics. Benefiting from the TiO2/Ni4Fe6-LDH heterojunctions, the TiO2/ Ni4Fe6-LDH shows an overpotential of 371 mV @30 mA cm−2 and a Tafel slope of 131.36 mV/dec under illumination, which is better than Ni4Fe6-LDH and TiO2. The comparison experiment of oxygen evolution efficiency showed that the polarization current density of TiO2/Ni4Fe6-LDH reached 12 mA cm−2 under the illumination voltage of 1.72 V, which was twice the current density under the non-illumination condition. Surface electronic structure analysis shows that these excellent OER performance are largely due to the introduction of TiO2, which not only enables Ni4Fe6-LDH surface to have more oxygen vacancy, increase photoanode conductivity and accelerate reaction electron conduction, but also accelerates hole capture and enhances OER reaction kinetics. This synergistic effect between semiconductor and OER catalyst provides more ideas for realizing efficient and stable photoelectrochemical water oxidation.

Comparative analysis of life cycle assessment of biogas-powered and coal-powered power plant for optimized environmental operation

The major concerns that mankind faces today are limited reserves of conventional energy, growing energy demand, and environmental pollution. This study depicts a comparative analysis done for the life cycle assessment of the biogas-based plant and coal-based plant designed for Bikaji Foods International Ltd., India. OpenLCA version 1.11.0 software was used with the database ecoinvent 3.3 LCIA methods (ReCiPe Midpoint H) to analyze the environmental impact and investigate the effect of the biogas-based plant and the coal-based plant. The functional unit of 1 MJ of energy generated from biogas and coal was selected to represent the results of the production of 15,271,600 MJ of energy. The results for marine eutrophication, particulate matter formation, photochemical oxidant formation and terrestrial acidification for the biogas-based plant were 734.527 kg N-Eq, 6314.012 kg PM10-Eq, 1328.629 kg NMVOC and 3.933E04 kg SO2-Eq, respectively. Whereas, for coal-based plant, these values were 4919.442 kg N-Eq, 1.962E04 kg PM10-Eq, 6486.987 kg NMVOC and 13.448E04 kg SO2-Eq, respectively. The greenhouse gas emissions and fossil depletion from the biogas-based plant were found negligible as compared to the coal-based plant. Overall, it was found that the biogas-based plant has a more remunerative impact on the environment than the coal-based plant. This study recommends that local authorities and industrial communities should invest more and more in increasing the number of biogas plants at domestic as well as commercial levels and secure a clean and green future for coming generations.

Photochemical Oxidation of Polyethylene Terephthalate Microplastics Adsorbed on Sand and Silica Surfaces.

The environmental contamination by plastics, microplastics, and related compounds is a major concern. While the detection and release of micro- and nanoparticles from these materials have been widely studied, the formation and release of molecules resulting from their degradation in the environment have been overlooked. This work presents a study of the products released from poly(ethylene terephthalate) (PET) irradiated as pure particles and adsorbed on silica and sand surfaces under different irradiation conditions. The role of oxygen was also evaluated. The products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The main released molecules can be accounted for by considering the cleavage of α- and β-bonds next to the ester moiety of the polymer chain. Volatile products such as benzene as well as monomer units of the polymer and related products were identified. In the presence of oxygen, acetic acid and products resulting from hydroxylation at the benzenic ring or at the ethyl moiety were detected. Adsorption on silica and sand has little effect on the photoproduct distributions. The irradiation at 360 nm leads to distributions similar to the ones observed at 257 nm, but the reaction rate is lower. The identified product ethylene terephthalate is a marker of PET plastics and particles and can therefore be used to evaluate the environmental contamination by this polymer material.

Comparative analysis of winter composite-PM2.5 in Central Indo Gangetic Plain cities: Combined organic and inorganic source apportionment and characterization, with a focus on the photochemical age effect on secondary organic aerosol formation

To gain insights into air quality dynamics, a high-end instrument such as High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) alongside an Aethalometer was used to measure the Composite PM2.5 (C-PM2.5) in Lucknow and Kanpur during winter. It encompasses non-refractive PM2.5 (NR-PM2.5) and Black Carbon (BC) mass concentrations. Significant variation was noted in average C-PM2.5 concentrations at both sites, as 168.8 ± 61.3 μg m−3 in Lucknow and 90.7 ± 25.7 μg m−3 in Kanpur. Organics emerged as the predominant component, constituting ∼55%–65% of the C-PM2.5 mass, followed by inorganics (24% and 30%) and BC (20% and 8%). The present study employs Positive Matrix Factorization (PMF) on combined organic and inorganic source apportionment, resolving eight and seven source factors at Lucknow and Kanpur, respectively. Both sites exhibit significant contributions from solid-fuel combustion organic aerosol (SFC-OA), with ∼11% in Lucknow and 8% in Kanpur. However, SFC-OA mass concentration in Lucknow, at 24.67 μg m-³, is nearly double that in Kanpur (12.05 μg m-³). This was likely due to domestic coal burning in the nearby households, unregulated open burning, and burning of garbage on roadsides. The study shows that both sites were affected by oxidized biomass burning OA (O-BBOA) emissions, with increased concentration during the night due to dark oxidation by NO3 radicals. The diurnal variation of secondary organic aerosols (SOA), such as O-BBOA and semi-volatile oxygenated OA (SVOOA), shows increasing concentration during daytime hours. Therefore, the photochemical aging (ta) role in SOA formation was analyzed, and it was revealed that the formation might primarily be driven by photochemical oxidation. Additionally, two inorganic-rich factors, sulfate and nitrate-related OA (SO4-OA and NO3-OA) at both sites and additional ammonium chloride-related OA (NH4Cl-OA) resolved at Lucknow. Our study shows that NO3-OA and SO4-OA formation was dominated by aqueous phase processes due to high relative humidity and decline in concentration with increasing ta (ta > 30 h) during winter.

Environmental, technological, and economic analysis of supercritical coal-fired power system.

Developing countries primarily rely on fossil-based energy sources to meet their energy demands. The use of fossil fuels has several adverse environmental repercussions that damage the biosphere both directly and indirectly. Among fossil fuels, coal brings about the heaviest environmental externalities, yet its abundance makes its use widespread, particular in countries having significant power generation deficits, such as Pakistan. This study presents an environmental, technological, and economic analysis of a supercritical coal-based power unit located in Pakistan and used for electricity generation. For environmental assessment, the CML-1A baseline method in OpenLCA software was used, and eight midpoint impact indicators were selected. The functional unit chosen was 1 MWh of generated electricity. The results indicated that the category of ozone layer depletion has the least impact, whereas global warming potential has the highest impact score. Except for photochemical oxidation and human toxicity, the plant operational stage dominated most of the selected impact categories. The current paper also reveals that the removal efficiency of CO2 and other pollutants is higher in supercritical compared to subcritical plants. Moreover, the economic feasibility of supercritical plant is compared with chemical looping combustion (CLC)-based supercritical coal-fired power plant, and results shows that CLC-based coal-fired power plant is a more competitive and environmentally friendly option. The utilization of a scientific cleaner energy-management system in real-time, as exemplified in this study, may facilitate the development of a optimalpolicy framework that encouragesfor the adoption of cleaner coal power generation in developing countries, ultimately resulting in improved energy sustainability. Furthermore, this paper also presents some policy implications which could be helpful for policymakers, researchers, and industrialists to improve the sustainability of energy in emerging economies.

Photocatalyzed Synthesis of a Schiff Base via C-N Bond Formation: Benzyl Alcohol as Sustainable Surrogates of Aryl Aldehydes.

The advancement of photocatalytic techniques has enabled green chemical synthesis through visible-light-mediated photochemical oxidation under mild conditions. A novel approach under visible-light conditions was facilitated by eosin-Y for the reaction between substituted benzyl alcohols and anilines, resulting in the synthesis of diverse Schiff bases. This innovative method is emphasized for its environmentally friendly nature, lack of metal catalysts, cost-effectiveness, and nontoxic characteristics.

Effects of Ammonia Mitigation on Secondary Organic Aerosol and Ammonium Nitrate Particle Formation in Photochemical Reacted Gasoline Vehicle Exhausts

Gaseous air pollutants emitted primarily by anthropogenic sources form secondary products through photochemical reactions, complicating the regulatory analysis of anthropogenic emissions in the atmosphere. We used an environmental chassis dynamometer and a photochemical smog chamber to conduct a parameter sensitivity experiment to investigate the formation of secondary products from a gasoline passenger car. To simulate the mitigation of ammonia emissions from gasoline vehicle exhausts assuming future emission controls and to allow photochemical oxidation and aging of the vehicle exhaust, ammonia was selectively removed by a series of five denuders installed between the vehicle and photochemical smog chamber. Overall, there were no differences in the formation of secondary organic aerosols and ozone with or without ammonia mitigation. However, the potential for ammonium nitrate particle formation was significantly reduced with ammonia mitigation. In addition, ammonia mitigation resulted in increased aerosol acidity due to nitric acid in the gas phase not being neutralized by ammonia and condensing onto the liquid particle phase, indicating a potentially important secondary effect associated with ammonia mitigation. Thus, we provide new insights into the effects of ammonia mitigation on secondary emissions from gasoline vehicle exhaust and into a potentially useful experimental approach for determining primary and secondary emissions.

Effect of Mn(II) photochemical oxidation on Cd immobilization in hematite

Hematite, a commonly stable iron oxide in the environment, which can not only adsorb Cd in the environment, but also catalyze the photochemical oxidation of Mn(II) in the environment. However, the impact of Mn(II) on the structure of hematite and the adsorption of Cd during the surface oxidation of hematite remains unknown. In this study, we investigated the surface and structural changes of hematite after the photochemical oxidation of Mn(II), as well as the geochemical behavior of Cd during this process. The results demonstrate that Mn(II) was oxidized to Mn(III/IV) on the hematite surface, with some Mn(III) being incorporated into the hematite structure. Simulations using XRD data showed that higher Mn(II) concentrations resulted in increased levels of Mn doping, leading to significant variations in the hematite unit cell. This was further confirmed through FTIR and Raman spectroscopy characterization. The oxidation of Mn(II) on the hematite surface resulted in a shift in surface charge from positive to negative, enhancing the adsorption capacity of Cd. However, when Mn(II) exceeded 0.4 mM, the immobilization of Cd within the system decreased. This was attributed to the competitive adsorption of Mn(II) and a reduction in the relative abundance of Mn(IV) oxides.

γ-Lactones in Canadian high arctic aerosols: Tracers for the oxidation of unsaturated fatty acids and intramolecular esterification of γ-hydroxyacids during polar sunrise

In this study, we detected for the first time a series of γ-lactones (C7-C16) isolated from Canadian high arctic aerosols collected from late February to June as the sun rises from below the horizon to the maximum. γ-Lactones were identified and quantified by GC-MS utilizing the fragment ion (m/z 85) of [C4H5O2]+. Their molecular distributions showed the predominance of C9 species (on average, 25 pg/m3) followed by C10, C8, C11, C12, C16, C15, and C7. The odd-carbon numbered γ-lactones such as C9 and C11 are produced by the oxidation of oleic (Δ9C18:1) and eicosanoic (Δ9C20:1) acids, respectively, to monocarboxylic acids in the atmosphere, followed by the subsequent oxidation to positional isomers of hydroxy acids and intramolecular esterification of γ-hydroxy acids. Unsaturated fatty acids, plausible sources of the γ-lactones, can originate from marine phytoplankton and terrestrial vegetation via long-range atmospheric transport to the Arctic. Series of ω-oxoacids were also detected with the predominance of C9 species, supporting the photochemical oxidation of biogenic unsaturated fatty acids in the Arctic atmosphere after polar sunrise and/or during the long-range transport to the Arctic.

Important yet Overlooked HONO Source from Aqueous-phase Photochemical Oxidation of Nitrophenols.

Nitrites (NO2-/HONO), as the primary source of hydroxyl radicals (•OH) in the atmosphere, play a key role in atmospheric chemistry. However, the current understanding of the source of NO2-/HONO is insufficient and therefore hinders the accurate quantification of atmospheric oxidation capacity. Herein, we highlighted an overlooked HONO source by the reaction between nitrophenols (NPs) and •OH in the aqueous phase and provided kinetic data to better evaluate the contribution of this process to atmospheric HONO. Three typical NPs, including 4-nitrophenol (4NP), 2-nitrophenol (2NP), and 4-nitrocatechol (4NC), underwent a denitration process to form aqueous NO2- and gaseous HONO through the •OH oxidation, with the yield of NO2-/HONO varied from 15.0 to 33.5%. According to chemical composition and structure analysis, the reaction pathway, where the ipso addition of •OH to the NO2 group on 4NP generated hydroquinone, can contribute to more than 61.9% of the NO2-/HONO formation. The aqueous photooxidation of NPs may account for HONO in the atmosphere, depending on the specific conditions. The results clearly suggest that the photooxidation of NPs should be considered in the field observation and calculation to better evaluate the HONO budget in the atmosphere.

Stable isotope compositions, source apportionment and transformation processes of carbonaceous aerosols in PM10 in the urban city of Hyderabad, India

This study apportions sources of carbonaceous aerosols using isotopic characteristics of total carbon (TC) and elemental carbon (EC) in PM10 aerosols using filter-based CTO-375 method for pre-monsoon (summer), post-monsoon, and winter (2019–2021) over Hyderabad, India. Highest secondary organic carbon, SOC (primary organic carbon, POC) of 13.78 ± 10.25 (7.87 ± 2.48) μg/m3 was during post-monsoon 2020 (2019), while lowest was 8.90 ± 5.55 (4.18 ± 0.92) μg/m3 during pre-monsoon 2021 (post-monsoon 2020), respectively. Average effective carbon ratio (ECR) > 1 indicates dominance of light scattering aerosols during pre-monsoon and post-monsoon. δ13CTC and δ13CEC varied from – 28.1 to – 24.7 ‰ (avg. – 26.5 ± 0.7) and - 32.5 to – 24.6 ‰ (avg. – 27.4 ± 1.1), indicating contribution from C3 plant burning and liquid fuel combustion. Positive value of δ13COC – δ13CEC and heavier δ13CTC, along with gradual enrichment in δ13CTC and δ13CEC from December 2020 to March 2021, suggested photochemical aging of carbonaceous aerosols. Lighter δ13CTC and OC/EC > 4 for all seasons indicates dominance of biomass burning (wood and crop residue burning), photochemical oxidation and secondary organic aerosol (SOA) formation. The tropical study experiences dominance of lighter δ13CEC compared to subtropical, high latitude regions.

Economic and environmental sustainability of copper indium gallium selenide (CIGS) solar panels recycling

End-of-life management of copper indium gallium selenide (CIGS) thin-film solar photovoltaics (PV) panels is crucial due to the necessity of recycling valuable elements such as indium ($400/kg) and gallium ($618/kg), ensuring both economic viability and environmental sustainability. In this study, we analyze the private and external costs of end-of-life management for CIGS PV designed for mass-scale recycling. Our findings reveal that the private and external costs of end-of-life management range from ∼$3.5 to $4.5 and ∼$3.0 to $4.0 per m2, respectively. The chemicals utilized in the recycling process, particularly NaOH and HCl, significantly contribute to climate change, photochemical oxidant formation, particulate matter formation, and freshwater eutrophication impact categories, accounting for ∼50 % to 90 % of the impacts. Furthermore, we found the net cost of recycling by subtracting the economic benefit obtained from recovered materials from the sum of private and external costs, revealing values ranging between $4.3 and $5.7 per m2 of CIGS PV module. These findings suggest that there is room to reduce the net cost further by recovering more materials from the CIGS PV modules components.