Photochemical Formation Research Articles

Toward combined photobiological–photochemical formation of kerosene-type biofuels: which small 1,3-diene photodimerizes most efficiently?

A transition from fossil- to bio-based hydrocarbon fuels is required to reduce greenhouse gas emissions; yet, traditional biomass cultivation for biofuel production competes with food production and impacts negatively on biodiversity. Recently, we reported a proof-of-principle study of a two-step photobiological–photochemical approach to kerosene biofuels in which a volatile hydrocarbon (isoprene) is produced by photosynthetic cyanobacteria, followed by its photochemical dimerization into C10 hydrocarbons. Both steps can utilize solar irradiation. Here, we report the triplet state (T1)-sensitized photodimerization of a broader set of small 1,3-dienes to identify which structural features lead to rapid photodimerization. Neat 1,3-cyclohexadiene gave the highest yield (93%) after 24 h of irradiation at 365 nm, followed by isoprene (66%). The long triplet lifetime of 1,3-cyclohexadiene, which is two orders of magnitude longer than those of acyclic dienes, is key to its high photoreactivity and stem from its planar T1 state structure. In contrast, while isoprene is conformationally flexible, it has both photochemical and photobiological advantages, as it is the most reactive among the volatile 1,3-dienes and it can be produced by cyanobacteria. Finally, we explored the influence of solvent viscosity, diene concentration, and triplet sensitizer loading on the photodimerization, with a focus on conditions that are amenable when the dienes are produced photobiologically. Our findings should be useful for the further development of the two-step photobiological–photochemical approach to kerosene biofuels.Graphical abstract

Recombination of X-ray-Generated Radical Ion Pairs in Alkane Solution Assembles Optically Inaccessible Exciplexes from a Series of Perfluorinated para-Oligophenylenes with N,N-Dimethylaniline.

We demonstrate that a series of perfluorinated para-oligophenylenes C6F5-(C6F4)n-C6F5 (n = 1-3) produce exciplexes with N,N-dimethylaniline (DMA) in degassed X-irradiated n-dodecane solutions. The optical characterization of the compounds shows that their short fluorescence lifetimes (ca. 1.2 ns) and UV-Vis absorption spectra, overlapping with the spectrum of DMA with molar absorption coefficients of 2.7-4.6 × 104 M-1cm-1, preclude the standard photochemical exciplex formation pathway via selective optical generation of the local excited state of the donor and its bulk quenching by the acceptor. However, under X-rays, the efficient assembly of such exciplexes proceeds via the recombination of radical ion pairs, which delivers the two partners close to each other and ensures a sufficient energy deposition. The exciplex emission is completely quenched by the equilibration of the solution with air, providing a lower bound of exciplex emission lifetime of ca. 200 ns. The recombination nature of the exciplexes is confirmed by the magnetic field sensitivity of the exciplex emission band inherited from the magnetic field sensitivity from the recombination of spin-correlated radical ion pairs. Exciplex formation in such systems is further supported by DFT calculations. These first exciplexes from fully fluorinated compounds show the largest known red shift of the exciplex emission from the local emission band, suggesting the potential of perfluoro compounds for optimizing optical emitters.

Current ambient ozone levels mitigate the effect of Puccinia striiformis on wheat: Is Mediterranean wheat ready for pre-industrial background ozone levels?

Increasing surface ozone is a main concern for crop production in the Global Change framework, especially in the Mediterranean basin where climate conditions favor its photochemical formation. Meanwhile, increasing common crop diseases, such as yellow rust, one of the most important pathogens affecting global wheat production has been detected in the area in recent decades. However, the impact of O3 on the occurrence and impact of fungal diseases is scarcely understood.A close-to-field-conditions assay (Open Top Chamber facility) situated in a Mediterranean cereal rainfed farming area was carried out to study the impact of increasing O3 levels and N-fertilization on spontaneous fungal outbreaks in wheat. Four O3-fumigation levels reproducing pre-industrial to future pollutant atmospheres with additional 20 and 40 nL L−1 over the ambient levels were considered (7 h-mean ranging from 28 to 86 nL L−1). Two top N-fertilization supplementations (100 and 200 kg ha−1) were nested within the O3 treatments; foliar damage, pigment content and gas exchange parameters were measured. Pre-industrial natural background O3 levels strongly favored the yellow rust infection, where the O3-polluted levels currently observed at the farm highly benefited the crop, mitigating the presence of rust by 22 %. However, future expected high O3-levels neutralized the beneficial infection-controlling effect by inducing early wheat senescence, decreasing the chlorophyll index of the older leaves by up to 43 % under the higher O3 exposure. Nitrogen promoted the rust infection by up to 49.5 % without interacting with the O3-factor. Achieving future air quality standards might require considering new varietal improvement programs, to be able to adapt crops to an increased pathogen tolerance without requiring the assistance provided by O3-pollution.

Estimation of particle size distributions in the atmosphere—analysis of Fe and Ca particles as the representative examples

Atmospheric aerosols, including primary aerosols emitted directly into the atmosphere and secondary aerosols generated in the atmosphere from various chemically complex particles, cause a variety of environmental problems such as climate change, photochemical smog formation, and a decrease in incoming solar radiation. Therefore, it is important to understand the causes of aerosol particles and their impact on human society. In particular, particle size is an important indicator of lung penetration depth, aerosol transport, and optical properties. Hence, we mathematically estimated the airborne particle size distributions of each chemical component by collecting aerosol samples from the atmosphere using two types of cyclone samplers, large and small cyclone samplers. This study’s findings also suggest that calculated changes in particle size distribution can reflect changes in particle sources. The higher resolution of the continuous functions will enable the detection of the subtle changes in particle size distributions of each chemical component, which is helpful to understand the temporal changes in the chemical properties of the airborne aerosol particles.

Towards the carbon neutrality of sludge treatment and disposal in China: A nationwide analysis based on life cycle assessment and scenario discovery

Motivated by the carbon neutrality target, strategic planning for a low-carbon transition of sludge treatment and disposal in China is challenging due to the unpredictability of technical, regional, socioeconomic, and political factors affecting greenhouse gas (GHG) emissions. This study combines the use of a Life Cycle Assessment and the Patient Rule Induction Method, accounting for possibilities that could achieve net-zero carbon emissions by exploring multiple plausible future profiles of sludge treatment and disposal. Results show that reducing sludge landfill and increasing anaerobic digestion are effective methods to facilitate GHG reduction. Achieving carbon neutrality is closely linked to developing a cleaner electricity mix. Based on a cascaded scenario analysis considering regional differences for 31 Chinese provinces, results demonstrated a maximum cumulative reduction potential of 371 Mt CO2 equivalents from 2020 to 2050, equal to 59.84% of the business-as-usual scenario. Together with GHG reductions, terrestrial acidification and ecotoxicity as well as freshwater ecotoxicity are synergistically reduced. However, the shifting environmental burden results in freshwater eutrophication, human toxicity, marine ecotoxicity, marine eutrophication, and photochemical oxidant formation. This study presents a novel method for systematically identifying possible future development paths toward carbon neutrality. The findings may support policy designs for achieving target carbon reduction effects for sludge disposal.

Small steps towards energy poverty mitigation: Life cycle assessment and economic feasibility analysis of a photovoltaic and battery system in a Brazilian indigenous community

The so-called energy transition has been associated with decreasing dependence on fossil fuel energy and low environmental impacts. Additionally, several communities worldwide still face energy poverty, with no or limited access to energy services. This paper evaluates the environmental and economic aspects related to replacing diesel-based power systems with photovoltaic and battery storage systems in a small indigenous community in northern Brazil. Nine environmental categories were analyzed for the life cycle perspective, from which it was established that the benefits of the photovoltaic system outperformed the diesel-based system in seven of the nine categories i.e., climate change (by a difference of 189.8 t CO2-eq over the system's lifetime, i.e., 300 MWh generated over 25 years), fossil depletion (by 66.7 t oil-eq), environmental toxicity (by 1.4 t 1,4-DCB-eq), particulate matter formation (by 1.5 t PM10-eq), photochemical oxidant formation (by 4.8 t NMVOC), terrestrial acidification (by 2.5 t SO2-eq), and eutrophication (by 1.7 t nutrients-eq). On the other hand, metal depletion showed similar values for both cases, while the diesel-based system was associated with lower human toxicity (by 14.8 t 1,4-DCB-eq) given the high usage of toxic metals when manufacturing the battery systems. Regarding the economic aspects, from stochastic analysis, the results for replacing diesel-based systems result in average savings of around 9 thousand USD over 25 years. Hopefully, these positive results might stimulate policy efforts that lead to mitigating energy poverty in Brazilian indigenous communities.

Characteristics, Ozone Formation Potential and Sources of VOCs in Shandong Province, Eastern China

Between 9 July and 19 August 2016, the air concentrations of 57 volatile organic compounds (VOCs) were measured in Shandong Province, eastern China. Seven sampling sites representing urban, coastal and background sites were selected for sampling. The measured data were employed to investigate the VOCs’ characteristics, ozone formation potential, and main sources. During the sampling period, the concentrations of the VOCs ranged between 15.3 and 883 ppbv, with a mean of 139 ppbv. The most severely polluted city was Zibo (833 ppbv), followed by Jinan (33.5 ppbv) and Qingdao (32.8 ppbv). Propane was the most abundant species in all of the sampling sites, with a concentration range of 1.05–9.86 ppbv. Ethene, i-butane, 1-butene, cis-2-butene, n-butane, i-pentane, n-pentane, benzene and toluene were the predominant species in both the urban and coastal sites. Propylene equivalent concentrations (Pro-Equiv) and maximum incremental reactivity (MIR) were employed to assess the reactivity and contribution of each species to the photochemical ozone formation. The results showed that alkenes and aromatics were the most active species performing a key function in the ozone formation, accounting for 43.9–90.7% of the Pro-Equiv and 41.0–93% of the ozone formation potential (OFP). The ratios of ethylbenzene and m/p-xylene were calculated, and the results showed that local emissions were the main sources. Gasoline exhaust/fuel evaporation, industry process/solvent usage, diesel exhaust/petrochemical emission and coal burning were the dominant sources of VOCs in Shandong Province.

Photoinduced Cascade Reactions of 2-Allylphenol Derivatives toward the Production of 2,3-Dihydrobenzofurans

A light-driven protocol for the synthesis of 2,3-dihydrobenzofurans under mild conditions is reported. Specifically, the cascade process is initiated by the photochemical activity of allyl-functionalized phenolate anions, generated in situ upon deprotonation of the corresponding phenols. The reaction proceeds rapidly with reaction times as low as 35 min, delivering a wide range of densely functionalized products (20 examples, yields up to 69%). Mechanistic studies have also been performed providing convincing evidence for the photochemical formation of carbon-centered radical species. A cascade reaction pathway involving a tandem atom transfer radical addition (ATRA) and an intramolecular nucleophilic substitution (SN) process is proposed to occur.

Decoupling Optical Response and Photochemical Formation of Singlet Oxygen in Size Isolated Fractions of Ozonated Dissolved Organic Matter.

The complex effects of ozonation on the photophysical and size-based properties of dissolved organic matter (DOM) were investigated using two DOM isolates, Suwannee River Fulvic Acid (SRFA) and Pony Lake Fulvic Acid (PLFA). A size exclusion chromatography system paired with absorbance, fluorescence, and total organic carbon detection was used to determine the fluorescence quantum yield (Φf) as a function of the apparent molecular weight (AMW). Size-based fractions of each isolate were collected and irradiated to measure singlet oxygen (1O2) quantum yield (Φ1O2). Φf decreased with ozonation in low AMW fractions, while increasing in high AMW fractions. Φ1O2 increased with ozone dose in low AMW fractions from ∼2 to ∼7% and ∼3 to ∼11% for PLFA and SRFA, respectively, indicating that these are the most photoreactive fractions of DOM. Decreases in Φf and concomitant increases in Φ1O2 in low AMW fractions indicated that chemical transformations occurred, likely including the conversion of phenols to quinones, particularly in SRFA. Results further suggest that the photoactive and fluorescent fractions of DOM are likely independent pools of chromophores from different AMW fractions. In PLFA, a linear response in Φ1O2, specific UV absorbance at wavelength 254 nm (SUVA254), and Φf with ozonation indicated the equal distribution of ozone-reactive moieties.

Comparative sustainability assessment of lithium-ion, lithium-sulfur, and all-solid-state traction batteries

PurposeTraction batteries are a key component for the performance and cost of electric vehicles. While they enable emission-free driving, their supply chains are associated with environmental and socio-economic impacts. Hence, the advancement of batteries increasingly focuses on sustainability next to technical performance. However, due to different system definitions, comparing the results of sustainability assessments is difficult. Therefore, a sustainability assessment of different batteries on a common basis considering the three sustainability dimensions is needed.MethodsThis paper investigates the sustainability of current and prospective traction battery technologies for electric vehicles. It provides a common base for the comparison of the predominant lithium-ion batteries with new technologies such as lithium-sulfur and all-solid-state batteries regarding the environmental and socio-economic impacts in their supply chain. A life cycle sustainability assessment of ten battery types is carried out using a cradle-to-gate perspective and consistent system boundaries. Four environmental impact categories (climate change, human toxicity, mineral resource depletion, photochemical oxidant formation), one economic performance indicator (total battery cost), and three social risk categories (child labor, corruption, forced labor) are analyzed.ResultsThe assessment results indicate that the new battery technologies are not only favorable in terms of technical performance but also have the potential to reduce environmental impacts, costs, and social risks. This holds particularly for the lithium-sulfur battery with solid electrolyte. The environmental benefits are even amplified with a higher share of renewable energy for component and battery production. Nevertheless, hotspots related to the high energy demand of production and the supply chain of the active materials remain.ConclusionsThis article emphasizes the need to evaluate different battery technologies on a common basis to ensure comparability of the results and to derive reliable recommendations. The results indicate that the lithium-sulfur battery with solid electrolyte is preferable since this battery has the best indicator scores for all impact categories investigated. However, all-solid-state batteries are still under development so that no conclusive recommendation can be made, but further development of these battery technologies appears promising.

Integrating ambient carbonyl compounds provides insight into the constrained ozone formation chemistry in Zibo city of the North China Plain

Quantifying the impact of carbonyl compounds (carbonyls) on ozone (O3) photochemical formation is crucial to formulating targeted O3 mitigation strategies. To investigate the emission source of ambient carbonyls and their integrated observational constraint on the impact of O3 formation chemistry, a field campaign was conducted in an industrial city (Zibo) of the North China Plain from August to September 2020. The site-to-site variations of OH reactivity for carbonyls were in accordance with the sequence of Beijiao (BJ, urban, 4.4 s−1) > Xindian (XD, suburban, 4.2 s−1) > Tianzhen (TZ, suburban, 1.6 s−1). A 0-D box model (MCMv3.3.1) was applied to assess the O3-precursor relationship influenced by measured carbonyls. It was found that without carbonyls constraint, the O3 photochemical production of the three sites was underestimated to varying degrees, and the biases of overestimating the VOC-limited degree were also identified through a sensitivity test to NOx emission changes, which may be associated with the reactivity of carbonyls. In addition, the results of the positive matrix factorization (PMF) model indicated that the main source of aldehydes and ketones was secondary formation and background (81.6% for aldehydes, 76.8% for ketones), followed by traffic emission (11.0% for aldehydes, 14.0% for ketones). Incorporated with the box model, we found that biogenic emission contributed the most to the O3 production at the three sites, followed by traffic emission as well as industry and solvent usage. Meanwhile, the relative incremental reactivity (RIR) values of O3 precursor groups from diverse VOC emission sources featured consistencies and differences at the three sites, which further highlights the importance of the synergetic mitigation of target O3 precursors at regional and local scales. This study will help to provide targeted policy-guiding O3 control strategies for other regions.

Environmental and economic sustainability of fresh-cut and pre-cooked vegetables

Due to the growing awareness about the environmental and economic sustainability of food products, the present research aims to evaluate the sustainability of fresh-cut and pre-cooked vegetables, a niche market with growing demand. An analysis was carried out using a detailed material, energy, and economic inventory based on a commercial food processing plant located in northeast Spain. The environmental sustainability was determined using process-based environmental life cycle assessment (E-LCA), applying a cradle-to-market approach, and using the EF3.0 impact assessment methodology to quantify impacts on five midpoint categories (climate change, photochemical ozone formation, acidification, freshwater eutrophication, and fossil resource use) and an aggregated single score. Additionally, an environmental life cycle costing (E-LCC) was performed. The pre-cooked vegetable products showed a higher environmental footprint than the fresh-cut products in all the impact categories (between 14.0 % and 39.9 %) and involved higher life cycle costs (15.2 %), due to the increased demand for ingredients, packaging materials, and electricity consumption per FU (kg of product). The carbon footprint (CF) and the cost for the fresh-cut products were 0.72 kg CO2 eq/kg and 2.62 €/kg, respectively, compared to 0.86 kg CO2/kg and 3.02 €/kg for the pre-cooked vegetables. The environmental profiles of both products were rather similar, with a dominance of the Upstream stage (production of ingredients and packaging materials), followed by the Core stage (mainly due to electricity consumed during vegetable processing). The relevance of the Core stage is amplified in the economic analysis due to the incorporation of certain processes which were not included in the process-based E-LCA (e.g., labour, capital, insurance, maintenance costs, etc.). To integrate the economic and environmental analyses, an eco-efficiency index was calculated that describes the carbon emissions per unit of monetary cost, resulting in 0.27 kg CO2eq/€ for the fresh-cut and 0.28 kg CO2 eq/€ for the pre-cooked vegetables.

Environmental impacts of upgrading gas to electric heating and cooling, considering decarbonisation of the electricity grid

Rising temperatures and higher energy costs have created the imperative for Australian households to reduce energy consumption via more efficient heating and cooling systems. These energy efficient systems could lower the overall environmental impacts as heating and cooling accounts for around 20%–50% of total energy usage of residential buildings. Nonetheless, the embodied energy of efficiency upgrades and whether it is offset by operational savings as well as decarbonisation of the electricity grid, is often overlooked. This research aims to determine the environmental impacts of 59 gas heater to electric reverse cycle air conditioner upgrades via a life cycle assessment. A reference gas heater and air conditioner were deconstructed and assessed on their material compositions. The operational energy savings of one year prior and after were collected for all upgrades.The results show that operational energy savings offset the embodied energy for the following impact categories: climate change (short-term), fossil and nuclear energy use, mineral resources use and ozone layer depletion. However, climate change (long-term), photochemical oxidant formation, human toxicity (cancer) freshwater and terrestrial acidification, marine eutrophication, particulate matter formation, ionizing radiation, water scarcity, land occupation and transformation (biodiversity) can only be offset with the decarbonisation of the electricity grid. Notwithstanding, human toxicity (non-cancer), freshwater ecotoxicity and eutrophication cannot be offset even with a complete decarbonisation of the electricity grid, as the impacts from the production stage are too high. Notwithstanding the limited effectiveness of full decarbonisation, it is worthwhile considering the materials used in the appliance to further lower the environmental impact.

Anthropogenic and biogenic tracers in fine aerosol based on seasonal distributions of dicarboxylic acids, sugars and related compounds at a rural background site in Central Europe

Water-soluble organic compounds in aerosols are considered as relevant indicators of atmospheric processes. Fine particulate matter (PM1) samples were collected at National Atmospheric Observatory Košetice (NAOK), a rural background site representative of Central Europe, from September 27, 2013 to August 9, 2014. The samples (n = 146) were analyzed for water-soluble dicarboxylic acids (hereafter referred to as diacids) and related compounds to identify their seasonal variations and origins. Based on the Positive Matrix Factorization (PMF) analysis, we identified 5 factors – 2 anthropogenic, 2 biogenic and 1 background factors.In winter, anthropogenic contributions dominated in total organic matter (OM). Typical tracers for the main winter anthropogenic factor 1, connected with biomass burning (BB), were anhydrosugars together with maleic (M), methylmaleic (mM) and methylsuccinic (iC5) acids. This BB factor accounted for 64.1 ± 14.3% of OM in winter (annual avg. 36.7 ± 27.4%). A secondary anthropogenic factor 2 was characterized by phthalic (Ph), terephthalic (tPh) and ketomalonic (kC3) acids, which we assigned to secondary combustion products. The contribution of anthropogenic factor 2 was at a similar level throughout the year (12.5 ± 10.1% in OM). Mainly in winter, although also in spring and autumn, was the characteristic formation of diacids by secondary aqueous phase reactions, typically accompanied by lower temperatures, global radiation and ozone (O3) concentrations, yet higher relative humidity (RH) and aerosol liquid water content (ALWC).In summer, contributions of biogenic origin dominated. Secondary organic aerosols (SOA) of biogenic origin were typically represented by malonic (C3), methylmalonic (iC4), 3-oxopropanoic (ωC3), 4-ketopimelic (kC7), 7-oxoheptanoic (ωC7), pimelic (C7) and suberic (C8) acids. The factor, named as Biogenic 1, was dominant in summer with a contribution of 40.3 ± 19.6% in OM, while in other seasons, its contribution was below 10%. This factor was mainly characterized by a relative summer increase in the concentrations of kC7 and ωC7 acids. The second biogenic factor 2, also significant in summer (36.8 ± 20.5%) and dominant in spring (34.9 ± 19.9%), was represented by primary sugars (fructose, galactose and sucrose), normal chain diacids (oxalic (C2) to azelaic (C9)) and their oxidative precursors (ωC3, 4-oxobutanoic (ωC4) and 5-oxopentanoic (ωC5) acids). The photochemical formation of SOA in the gas phase was characteristic mostly for the summer season, accompanied by higher temperatures, global radiation and O3 concentrations, and lower RH.Additionally, background factor was resolved, which represents compounds with no distinctive seasonal variation and can therefore be of both anthropogenic and biogenic origin and contained mainly less oxidized compounds (methylglyoxal (MeGly), glyoxal (Gly), glyoxylic acid (ωC2) and pyruvic acid (Pyr)).

Identifying photochemical alterations of dissolved pyrogenic organic matter using fluorescence spectroscopy

Many streams originate in forested watersheds at risk of wildfires. Wildfires can introduce thermally altered organic compounds to terrestrial and aquatic systems. Understanding the degradation of leachates from these burned organic materials, referred to as dissolved pyrogenic organic material (PyDOM), is critical in determining water quality impacts in forested watersheds. This study used fluorescence spectroscopy to examine photochemical alterations of PyDOM generated by leaching organic matter burned at various temperatures. The PyDOM was exposed to natural sunlight for 25 days and the photochemical formation of hydrogen peroxide was monitored. PyDOM was characterized using ultraviolet–visible absorption, excitation–emission matrix (EEM) fluorescence spectroscopy, and fluorescence indices. Throughout the experiment, the emission intensity of the humic peak for all light-exposed leachates decreased while dark leachates exhibited no significant change in their fluorescence spectra. Additionally, hydrogen peroxide concentrations and UV absorbance decreased progressively over time, providing direct evidence that PyDOM concentrations can be significantly reduced by photodegradation. A characteristically low emission peak was observed in the EEMs of the fresh PyDOM, which could help in detecting fresh PyDOM. These results demonstrate that PyDOM derived from burned leachates is susceptible to photodegradation and that fluorescence measurements could be used as proxies for detecting PyDOM immediately post-wildfire.

Environmental assessment of road transport fueled by ammonia from a life cycle perspective

Renewable energy penetration into the electricity market has been increasing over the last decades; however, it is a different story in the transport sector. Fossil fuels are still predominant; therefore, several alternatives are being studied to attain a low-carbon, more sustainable transport and, consequently, a sustainable society. Ammonia has the potential to be a viable option, and it is critical to study its environmental profile in this early phase to appraise its sustainability as a fuel for passenger road transportation. This work aimed to develop a life cycle assessment of an ammonia-fueled internal combustion engine passenger car from the cradle to the grave, considering 1 km traveled as the basis for comparison. The product system under study included four stages: (i) vehicle, (ii) infrastructure, (iii) energy production, and (iv) operation. Life cycle inventory data related to vehicle operation, specifically ammonia combustion, resulted from various simulations of a model that considered the effect of different operation modes and vehicle emission control strategies, which resulted in nine configurations. The results show that rich mixtures (with an equivalence ratio of 1.1) help to reduce both nitrogen oxides (NOX) and nitrous oxide (N2O) emissions. As for unburnt ammonia (NH3), the after-treatment system drastically diminishes these and NOX emissions. Data on infrastructure and other upstream processes was taken from the Ecoinvent 3.7.1 database, and the ammonia production was based on the life cycle inventory from previous research. The life cycle impact assessment was performed on OpenLCA software implementing the ReCiPe2016 Midpoint (H) v1.13 methodology. On average, per 1 km traveled in an ammonia-based ICEV represents 0.098 kg CO2-eq for global warming potential (GWP100), 30.755 g oil-eq for fossil depletion potential (FDP), 38.974 mg P-eq for freshwater eutrophication potential (FEP), 8.907 μg CFC-11-eq for ozone depletion potential (ODP), 0.906 g NMVOC-eq for photochemical oxidant formation potential (POFP), and 1.029 g SO2-eq for terrestrial acidification potential (TAP). These results show a significant reduction, above −70%, for GWP100, FDP, and ODP compared with the same vehicle fueled on gasoline.

Climate-driven deterioration of future ozone pollution in Asia predicted by machine learning with multi-source data

Abstract. Ozone (O3) is a secondary pollutant in the atmosphere formed by photochemical reactions that endangers human health and ecosystems. O3 has aggravated in Asia in recent decades and will vary in the future. In this study, to quantify the impacts of future climate change on O3 pollution, near-surface O3 concentrations over Asia in 2020–2100 are projected using a machine learning (ML) method along with multi-source data. The ML model is trained with combined O3 data from a global atmospheric chemical transport model and real-time observations. The ML model is then used to estimate future O3 with meteorological fields from multi-model simulations under various climate scenarios. The near-surface O3 concentrations are projected to increase by 5 %–20 % over South China, Southeast Asia, and South India and less than 10 % over North China and the Gangetic Plains under the high-forcing scenarios in the last decade of 21st century, compared to the first decade of 2020–2100. The O3 increases are primarily owing to the favorable meteorological conditions for O3 photochemical formation in most Asian regions. We also find that the summertime O3 pollution over eastern China will expand from North China to South China and extend into the cold season in a warmer future. Our results demonstrate the important role of a climate change penalty on Asian O3 in the future, which provides implications for environmental and climate strategies of adaptation and mitigation.

Oligomerization of photochemically oxidized phenothiazine by nanostructured α‐Fe2O3

AbstractPhenothiazines (PTZs) and their derivatives are a group of compounds that have diverse applications in medicine, the dye industry and advanced materials. Due to the electron–hole donating characteristic, these compounds have also been applied in batteries and solar energy devices. PTZs can be converted into stable radical cations by chemical and photochemical reactions. The PTZ radical cations are reactive for polymerization. The photochemical formation of PTZ radical cations is favored in aggregates by the Type I mechanism in which one molecule in the triplet excited state abstracts one electron from a neighbor molecule. In the present study, 10H‐phenothiazine (PHT) was dissolved in chloroform and converted to the radical cation species (PHT•+) by UV light irradiation. The radical cation was characterized by UV–visible absorption and electron paramagnetic resonance techniques. Addition of α‐Fe2O3 nanorods and nanowires to PHT•+ chloroform solution promoted its color change from orange to blue‐green. Absorption measurement revealed a significant decrease of the UV and visible bands assigned to radical cation species and the appearance of a broad band at the spectral region of 650 nm. The blue‐green solution was dried, leading to the formation of crystals that were characterized using the X‐ray diffraction technique. Considering possible PHT oligo(poly)merization, the crystals were analyzed using matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry that corroborated the formation of oligomers containing three, four and five PHT residues and their sulfoxide derivatives. The PHT oligomers retained photosensitivity and exhibited an electron paramagnetic resonance signal indicating possible applications as hole donors in electronic devices. Oligomerization was also obtained by aggregation of PHT•+ in sodium dodecylsulfate micelles indicating that proximity and orientation of the free radical molecules is the mechanism for the oligomerization. Therefore, a new route for PHT oligomerization catalyzed by α‐Fe2O3 nanowires is proposed. The method is readily available, inexpensive and environmentally safe. © 2022 Society of Industrial Chemistry.

Photochemical formation and reversible base-induced cleavage of a phosphagallene.

The reactivity of Cp*Ga (Cp* = C5Me5) towards phosphanylidenephosphoranes of the type ArTerP(PMe3) (ArTer = DipTer 2,6-(2,6-iPr2C6H3)2C6H3), TipTer 2,6-(2,4,6-iPr3C6H2)2C6H3 was investigated. While no thermal reaction was observed (in line with DFT results), irradiation at 405 nm at low temperatures resulted in the formation of phosphagallenes DipTerP = GaCp* (1a) and TipTerP = GaCp* (1b) accompanied by release of PMe3. When warming the reaction mixture to ambient temperatures without irradiation, the clean re-formation of ArTerP(PMe3) and Cp*Ga in a second-order reaction was observed. Upon removal of PMe3, 1a and 1b were isolated and fully characterized. Both derivatives were found to be labile and decomposed to the phosphafluorenes 2a and 2b, indicating generation of the transient phosphinidene ArTerP along with Cp*Ga. First reactivity studies show that CO2 and H2O cleanly reacted with 1a, affording DipTerPCO (3) and DipTerPH2 (4), respectively.

Photochemical formation of water-soluble oxyPAHs, naphthenic acids, and other hydrocarbon oxidation products from Cook Inlet, Alaska crude oil and diesel in simulated seawater spills

Hydrocarbon oxidation products (HOPs) formed from crude oil and diesel were generated from laboratory simulated spills at four different periods (1, 4, 7, and 10 days) under environmental conditions that mimicked those in Cook Inlet, Alaska.