In this work, an excitonic energy transfer (EET) based non-radical mechanism was proposed for the degradation of organic pharmaceuticals by graphitic carbon nitride (g-C3N4) under visible light irradiation. Using diclofenac (DCF) as a model molecule, the competition between single electron transfer (SET) and EET was studied through modulating the exciton binding energy of g-C3N4. The different mechanisms of SET and EET for DCF degradation were predicted by DFT calculation, and further confirmed by their different degradation pathways. When EET played an important role, the rationality of some very popular radical scavengers, such as p-BQ, TEMPOL and furfuryl alcohol must be reconsidered. In addition, humic acid (HA) had a distinct effect on EET and SET. Specifically, HA enhanced the EET process through photosensitization, but suppressed SET through radical quenching effect. The effect of HA on DCF degradation depended on the contribution ratio of SET and ET.
Fracture-cave carbonate reservoirs represent a significant amount of oil and gas resources worldwide, while their intrinsic complex pore network, large caves and tectonic fractures bring challenges to reservoir characterizations and productions. Many models have been proposed to solve the pressure transient analysis (PTA) solutions for such reservoirs. With recent explorations, the position of fractures and caves can be determined by seismic data. However, models using the position information with the coexistence of discrete fractures and caves were not reported in the literature. This paper proposes a novel semi-analytical model based on the Boundary Element Method (BEM), to describe the transient pressure behavior of the fracture-cave carbonate reservoirs. Basically, the proposed model treats the cave edge as an inner boundary and includes the fracture-cave fluid interchanges. As a results, the model's solution is proved to be flexible for arbitrary cave and reservoir shape. A typical system consisting of one fracture and one case is discussed in detail. The result indicates the well location is the key factor to the pressure response, where the pressure response is mostly affected by the cave volume and fracture conductivity when the well is on the cave and fracture, respectively. The sensitivities of three major parameters on the pressure response are analyzed. In addition, the proposed model is applied in two field cases. The result shows the proposed model is reliable and accurate.
Global climate changes urge prompt energy transition for less carbon emissions, from traditional fossil fuels to renewable and sustainable clean energy. However, in reality, the world's energy majority cannot make U-turn immediately to renewables or clean energy due to the immature technology readiness, insufficient resource availability and unstable energy supply. In the next few decades, the fossil fuels, particularly oil and gas, will continue acting as the primary energy sector. Thus, instead of absolutely abandoning fossil fuel and seeking for impractical carbon mitigation technologies, to decarbonise the oil and gas will be definitely feasible and contribute more to net-zero transitions. This study, initially put eyes on the oil and gas decarbonization, critically reviewing the oil and gas resources, technologies, policies, and their futures toward net-zero. Basically, the status of oil and gas resources from different global regions, including the details of reserves, productions, consumptions, are summarized and analyzed. Moreover, the oil and gas technologies are categorized as gas, thermal and non-thermal, new recovery methods, each of which is specifically discussed in the applicable reservoir, mechanism, features and examples. Then, the global carbon emissions are reviewed in perspectives of emissions from fuel types and world regions as well as mitigations policies. Accordingly, the carbon mitigation approaches, specially in the oil and gas industry, are collected and listed from enterprise managements and technology renovations. Lastly, based on all the information and analyses and assisted with IEA energy outlook report, we provide a potential pathway for the oil and gas towards carbon neutral. This paper provides comprehensive overview on the oil and gas pathway to net-zero, which will not only technically guide the oil and gas decarbonisations, also be of interest to wide-range readers who are not experts but intend to understand the energy transitions.
The practical importance of coherent forecasts in hierarchical forecasting has inspired many studies on forecast reconciliation. Under this approach, so-called base forecasts are produced for every series in the hierarchy and are subsequently adjusted to be coherent in a second reconciliation step. Reconciliation methods have been shown to improve forecast accuracy, but will, in general, adjust the base forecast of every series. However, in an operational context, it is sometimes necessary or beneficial to keep forecasts of some variables unchanged after forecast reconciliation. In this paper, we formulate reconciliation methodology that keeps forecasts of a pre-specified subset of variables unchanged or "immutable". In contrast to existing approaches, these immutable forecasts need not all come from the same level of a hierarchy, and our method can also be applied to grouped hierarchies. We prove that our approach preserves unbiasedness in base forecasts. Our method can also account for correlations between base forecasting errors and ensure non-negativity of forecasts. We also perform empirical experiments, including an application to sales of a large scale online retailer, to assess the impacts of our proposed methodology.
Organic peroxides (POs) are organic molecules with one or more peroxide (−O–O−) functional groups. POs are commonly regarded as chemically labile termination products from gas-phase radical chemistry and therefore serve as temporary reservoirs for oxidative radicals (HOx and ROx) in the atmosphere. Owing to their ubiquity, active gas-particle partitioning behavior, and reactivity, POs are key reactive intermediates in atmospheric multiphase processes determining the life cycle (formation, growth, and aging), climate, and health impacts of aerosol. However, there remain substantial gaps in the origin, molecular diversity, and fate of POs due to their complex nature and dynamic behavior. Here, we summarize the current understanding on atmospheric POs, with a focus on their identification and quantification, state-of-the-art analytical developments, molecular-level formation mechanisms, multiphase chemical transformation pathways, as well as environmental and health impacts. We find that interactions with SO2 and transition metal ions are generally the fast PO transformation pathways in atmospheric liquid water, with lifetimes estimated to be minutes to hours, while hydrolysis is particularly important for α-substituted hydroperoxides. Meanwhile, photolysis and thermolysis are likely minor sinks for POs. These multiphase PO transformation pathways are distinctly different from their gas-phase fates, such as photolysis and reaction with OH radicals, which highlights the need to understand the multiphase partitioning of POs. By summarizing the current advances and remaining challenges for the investigation of POs, we propose future research priorities regarding their origin, fate, and impacts in the atmosphere.
Organosulfur compounds (OSCs) are important components of fine particulate matter (PM2.5); however, little information is available on OSCs in urban regions due to their chemical complexity, especially for novel species such as aromatic sulfonates. To supplement the detection technique and systematically identify OSCs, in this study we developed a nontargeted approach based on gas chromatography and high-resolution mass spectrometry (GC-HRMS) to screen OSCs in PM2.5 of urban Beijing and provide field evidence for their source and formation mechanism. 76 OSCs were found through mass difference of sulfur isotopes and characteristic sulfur-containing fragments. 6 species were confirmed as aromatic sulfonates by authentic standards. 32 OSCs showed higher levels in the heating season, presumably because of the intensive emission, especially from coal combustion. While certain species, with 2-sulfobenzoic acid as the representative, were 2.6-times higher in the non-heating season than in the heating season. Such species were significantly correlated with ozone and aerosol liquid water content (r = 0.2–0.8, p < 0.05), implying an oxidation-involved aqueous-phase formation in the atmosphere. In addition, with an average proportion of ∼95 % of the total sulfobenzoic acids, the predominance of the 2-substitution product over its isomers of 3- or 4-sulfobenzoic acid suggests a more plausible mechanism of radical-initiated reaction of phthalic acid followed by sulfonation, with atmospheric reactivity indicated by ozone and temperature as the determining factor. This study provided not only a nontargeted approach for OSCs in ambient PM2.5, but also field evidence on their secondary formation proposed in previous simulation studies.
Vacuum ultraviolet (VUV) based advanced oxidation processes (AOPs) recently attracted widespread interests. However, the role of UV185 in VUV is only considered to be generating a series of active species, while the effect of photoexcitation has long been overlooked. In this work, the role of UV185 induced high-energy excited state for the dephosphorization of organophosphorus pesticides was studied using malathion as a model. Results showed malathion degradation was highly related to radical yield, while its dephosphorization was not. It was UV185 rather than UV254 or radical yield that was responsible for malathion dephosphorization by VUV/persulfate. DFT calculation results demonstrated that the polarity of P-S bond was further increased during UV185 excitation, favoring dephosphorization while UV254 did not. The conclusion was further supported by degradation path identification. Moreover, despite the fact that anions (Cl-, SO42- and NO3-) considerably affected radical yield, only Cl- and NO3- with high molar extinction coefficient at 185 nm significantly affected dephosphorization. This study shed light on the crucial role of excited states in VUV based AOPs and provided a new idea for the development of mineralization technology of organophosphorus pesticides.
Tungsten oxide nanowires (WO3−x) with rich oxygen vacancies (OVs) were fabricated through a facile hydrothermal method, which had both high adsorptive capability and photocatalytic activity. 95.1% of total U(VI) (C0 = 10 mg/L) was removed by WO3−x at pH 5, and 79.9% was transformed to U(IV) to achieve reductive immobilization after photocatalysis under simulated solar light. Band structure and optical characterizations indicated WO3−x had narrower band gap energy, but higher charger carrier separation and transfer rates compared with conventional WO3. Density functional theory (DFT) calculations further demonstrate the spin polarization state electrons of W 5d in WO3−x due to the construction of OVs, thus greatly inhibiting recombination of electron-hole pairs. In addition, the electron density increases in WO3−x and the photogenerated e– in the conduction band of WO3−x has higher reduction ability than WO3, leading to more efficient electron transfer from WO3−x to UO22+ after photo-excitation for U(VI) reduction.
Global hydrofluorocarbon (HFC) cumulative emissions will bemore than 20 Gt CO2-equiv during 2020−2060 and have a non-negligible impacton global warming even in full compliance with the Kigali Amendment (KA).Fluorochemical manufacturers (including multinationals) in China haveaccounted for about 70% of global HFC production since 2015, of which about60% is emitted outside China. This study built an integrated model (i.e., DECAF)to estimate both territorial and exported emissions of China under three scenariosand assess the corresponding climate effects as well as abatement costs. Achievingnear-zero territorial emissions by 2060 could avoid 23 ± 4 Gt CO2-equiv ofcumulative territorial emissions (compared to the 2019 Baseline scenario) during2020−2060 at an average abatement cost of 9 ± 6 USD/t CO2-equiv. Under thenear-zero emission (including territorial and abroad) pathway, radiative forcingfrom HFCs will peak in 2037 (60 ± 6 mW/m2) with a 33% peak reduction and 8years in advance compared to the path regulated by the KA, and the radiative forcing by 2060 will be lower than that in 2019.
Accelerated phase-out of HFC production in China could provide a possibility for rapid global HFC abatement and achieve greater climate benefits.
The propagation of antibiotic-resistant bacteria (ARB) greatly endangers the ecological safety and human health. This study employed pyrite (FeS2, naturally abundant mineral) for periodate (PI) activation to disinfect ARB. FeS2/PI system could disinfect 1 × 107 CFU mL−1 of kanamycin-resistant E.coli below the limit of detection in 20 min. Efficient ARB inactivation performance was achieved in pH from 3 to 9, ionic strength from 0 to 300 mM, with HA (0.1–10 mg L−1) in suspension, and in real water samples including tap water, river water and sewage. FeS2/PI system could also efficiently disinfect gentamycin-resistant E.coli and Gram-positive B. subtilis. The generated reactive species including Fe(IV), ·O2– and ·OH would attack cell membrane and overwhelmed intracellular defense system. The intracellular kanamycin resistance genes in cells would be released and then degraded in FeS2/PI system. PI preferred to be adsorbed on Fe site of FeS2 (with lower adsorption energy, more occupancy of bonding state and stronger bonding strength). The subsequent transfer of electron cloud from Fe site to PI would cleave IO bond to generate reactive species. Moreover, FeS2/PI system could also combine with sand filtration system to efficiently capture and disinfect ARB. Therefore, FeS2/PI system is a promising approach to inactivate ARB in different scenarios.
