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In regard to serious environmental pollution by methylene blue (MB) dye, it was crucial to design an efficacious adsorbent for the elimination of MB. Utilizing tannic acid (TA) to functionalize graphene oxide (GO) and employing acrylic acid (AA) and sodium p-styrenesulfonate (SSS) as the monomers, a pH-responsive TGO/P(SSS-co-AA) aerogel (where TGO represented TA-modified GO, and P(SSS-co-AA) denoted the copolymer of SSS and AA) was synthesized by a facile and green one-pot method. The resulting aerogel was subjected to a variety of characterizations, and its adsorption behaviors were systematically explored with MB as the model dye. The results indicated the pH-responsive TGO/P(SSS-co-AA) aerogel possessed the maximum theoretical adsorption capacity of 1782.5 mg/g, and the adsorption process could be accurately described by quasi-second order kinetics model and Langmuir model. The adsorption thermodynamics revealed that the adsorption was a spontaneous, endothermic, and entropy-increasing process. TGO/P(SSS-co-AA) aerogel exhibited highly selective adsorption property and excellent regeneration performance. Even following five regeneration cycles, adsorption capacity of the aerogel could still maintain 936.09 mg/g. In conclusion, TGO/P(SSS-co-AA) aerogel exhibited exceptional performance as an adsorbent for removing MB, providing an inspiration for the construction of GO-based composite aerogel and its actual application in efficient and selective wastewater treatment.

Despite the bandwidth scaling limit of electrical switching and the high cost of building Clos data center networks (DCNs), the adoption of optical DCNs is still limited. There are two reasons. First, existing optical DCN designs usually face high deployment complexity. Second, these designs are not full-optical and the performance benefit over the non-blocking Clos DCN is not clear. After exploring the design tradeoffs of the existing optical DCN designs, we propose TROD (Threshold Routing based Optical Datacenter), a low-complexity optical DCN with superior performance than other optical DCNs. There are two novel designs in TROD that contribute to its success. First, TROD performs robust topology optimization based on the recurring traffic patterns and thus does not need to react to every traffic change, which lowers deployment and management complexity. Second, TROD introduces tVLB (threshold-based Valiant Load Balance), which can avoid network congestion as much as possible even under unexpected traffic bursts. We conduct simulation based on both Facebook’s real DCN traces and our synthesized highly bursty DCN traces. TROD reduces flow completion time (FCT) by about 1.15- $2.16\times $ compared to Google’s Jupiter DCN, at least $2\times $ compared to other optical DCN designs, and about 2.4- $3.2\times $ compared to expander graph DCN. Compared with the non-blocking Clos, TROD reduces the hop count of the majority packets by one, and could even outperform the non-blocking Clos with proper bandwidth over-provision at the optical layer. Note that TROD can be built with commercially available hardware and does not require host modifications.

Aerosol black carbon (BC) is a short-lived climate pollutant. The poorly constrained provenance of tropical marine aerosol BC hinders the mechanistic understanding of extreme climate events and oceanic carbon cycling. Here, we collected PM2.5samples during research cruise NORC2016-10 through South China Sea (SCS) and Northeast Indian Ocean (NEIO) and measured the dual-carbon isotope compositions (δ13C–Δ14C) of BC using hydrogen pyrolysis technique. Aerosol BC exhibits six different δ13C−Δ14C isotopic spaces (i.e., isotope provinces). Liquid fossil fuel combustion, from shipping emissions and adjacent land, is the predominant source of BC over isotope provinces “SCS close to Chinese Mainland” (53.5%), “Malacca Strait” (53.4%), and “Open NEIO” (40.7%). C3biomass burning is the major contributor to BC over isotope provinces “NEIO close to Southeast Asia” (55.8%), “Open NEIO” (41.3%), and “Open SCS” (40.0%). Coal combustion and C4biomass burning show higher contributions to BC over “Sunda Strait” and “Open SCS” than the others. Overall, NEIO near the Bay of Bengal, Malacca Strait, and north SCS are three hot spots of fossil fuel-derived BC; the first two areas are also hot spots of biomass-derived BC. The comparable δ13C–Δ14C between BC in aerosol and dissolved BC in surface seawater may suggest atmospheric BC deposition as a potential source of oceanic dissolved BC.

Biomass burning (BB) is an important source of atmospheric persistent organic pollutants (POPs) across the world. However, there are few field-based regional studies regarding the POPs released from BB. Due to the current limitations of emission factors and satellites, the contribution of BB to airborne POPs is still not well understood. In this study, with the simultaneous monitoring of BB biomarkers and POPs based on polyurethane foam-based passive air sampling technique, we mapped the contribution of BB to polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the Indo-China Peninsula. Spearman correlations between levoglucosan and 16 PCBs (rs= 0.264–0.767, p< 0.05) and 2 OCPs (rs= 0.250–0.328, p< 0.05) confirmed that BB may facilitate POP emissions. Source apportionment indicated that BB contributed 9.3% to the total PCB and OCP mass. The high contribution of positive matrix factorization-resolved BB to PCBs and OCPs was almost consistent with their concentration distributions in the open BB season but not completely consistent with those in the pre-monsoon and/or monsoon seasons. Their contribution distributions may reflect the use history and geographic distribution in secondary sources of POPs. The field-based contribution dataset of BB to POPs is significant in improving regional BB emission inventories and model prediction.

Many optical circuit switched data center networks (DCN) have been proposed in the last decade to attain higher capacity and topology reconfigurability, though commercial adoption of these architectures have been minimal. One major challenge these architectures face is the difficulty of handling uncertain traffic demands using commercial optical circuit switches (OCS) with high switching latency. Prior works have generally focused on developing fast-switching OCS prototypes to quickly react to traffic variations through frequent reconfigurations. This approach, however, adds tremendous complexity overhead to the control plane, and raises the barrier for commercial adoption of optical circuit switched data center networks. We propose COUDER, a robust topology and routing optimization framework for reconfigurable optical circuit switched data centers. COUDER co-optimizes topology and routing based on a convex set of traffic matrices, and offers strict throughput guarantees for any future traffic matrices bounded by the convex set. For the bursty traffic demands that are unbounded by the convex set, we employ a desensitization technique to reduce performance hit. This enables COUDER to generate topology and routing solutions capable of handling unexpected traffic changes without relying on frequent topology reconfigurations. Our extensive evaluations based on Facebook’s production DCN traces show that, even with daily reconfigurations which could be realized by current commercial MEMS-based OCSs from Calient Technologies, COUDER achieves about 20% lower max link utilization, and about 32% lower average hop count compared to cost-equivalent static topologies. Our work shows that adoption of reconfigurable topologies in commercial DCNs is feasible even without fast OCSs.

The current understanding of the legacy and emerging organic pollutants in the soil of Bangladesh remains limited. Inadequate disposal practices, particularly in e-waste, landfills, and industrial operations, may lead to the pervasive presence of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in the country. This study aimed to systematically investigate the concentrations, sources, and risk assessment of halogenated flame retardants (HFRs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), organochlorine pesticides (OCPs), chlorinated paraffins (CPs), and PAHs in the contaminated soil of Dhaka's dumpsites, e-waste, and industrial areas collected in 2017. The total concentration of investigated pollutants averaged at 4790 ± 4040 ng g−1dw, with the following order: ∑44CPs (4110 ± 4140 ng g−1dw) > ∑16PAHs (422 ± 491 ng g−1dw) > ∑16HFRs (190 ± 538 ng g−1dw) > ∑209PCBs (43.5 ± 73.5 ng g−1dw) > ∑50PCNs (17.7 ± 21.0 ng g−1dw) > ∑27OCPs (9.41 ± 9.61 ng g−1dw). The e-waste site exhibited the highest total concentration of the target pollutants, reaching 12,700 ng g−1dw. CPs were the predominant contributors, accounting for averages of 81.8%, 70.5%, and 68.5% to waste landfills, e-waste, and industrial sites, respectively. A comprehensive analysis of 209 PCB congeners revealed their primary origin from Aroclor PCBs, with minor contributions from unintentionally produced PCBs. The highest incremental lifetime carcinogenic risk (ILCR) occurred in e-waste sites, contributed by dioxin-like PCBs, with a maximum value of 5.9 × 10−5for adults, exceeding the limit 1.0 × 10−6set by the U.S. EPA. The non-carcinogenic hazard quotients (HQs) were much lower, suggesting no significant risk from the investigated pollutants. Our findings highlight the importance of proper waste management and regulated e-waste recycling to mitigate potential hazardous risks to the Bangladeshi population.

Obtaining homogeneous blends of two covalently cross-linked polymers by mechanical mixing is not possible due to their permanent network topologies. Here, we demonstrate an effective route to prepare polymer blends from the common cross-linked epoxidized natural rubber (ENR) and epoxy resin vitrimer (EV) by mechanical mixing. Interfacial exchange reactions between these two networks occur by a dynamic transesterification. The as-prepared ENR–EV blends show excellent mechanical strength, extensibility, and thermal stability. Moreover, they also show typical vitrimeric properties, including self-healing, welding, and reprocessability. This work demonstrates a large-scale preparation of vitrimeric materials with high performance and versatility from commercially available polymers and affords a promising strategy to recycle both waste rubbers and resins.

Although organochlorine pesticides (OCPs) have been banned for more than three decades, their concentrations have only decreased gradually. This may be largely attributable to their environmental persistence, illegal application, and exemption usage. This study assessed the historic and current regional context for dichlorodiphenyltrichloroethane (DDT), chlordane, and hexachlorobenzene (HCB), which were added to the Stockholm Convention in 2001. An air sampling campaign was carried out in 2018 in nine cities of the Pearl River Delta (PRD), where the historical OCP application was the most intensive in China. Different seasonalities were observed: DDT exhibited higher concentrations in summer than in winter; chlordane showed less seasonal variation, whereas HCB was higher in winter. The unique coupling of summer monsoon with DDT-infused paint usage, winter monsoon with HCB-combustion emission, and local chlordane emission jointly presents a dynamic picture of these OCPs in the PRD air. We used the BETR Global model to back-calculate annual local emissions, which accounted for insignificant contributions to the nationally documented production (<1‰). Local emissions were the main sources of p,p’-DDT and chlordane, while ocean sources were limited (<4%). This study shows that geographic–anthropogenic factors, including source, history, and air circulation pattern, combine to affect the regional fate of OCP compounds.

The optical properties of secondary brown carbon (BrC) aerosols are poorly understood, hampering quantitative assessments of their impact. We propose a new method for estimating secondary source of BrC using excitation‐emission matrix (EEM) fluorescence spectroscopy, combined with parallel factor analysis (PARAFAC) and partial least squares regression (PLSR). Experiments were conducted on a collection of PM2.5samples from urban areas in five Chinese cities during winter and summer. The humic‐like component with long‐emission wavelengths (L‐HULIS) was identified as a secondary source tracer of BrC. This was confirmed by correlating PARAFAC components with secondary organic aerosol tracers and molecular oxidation indices obtained from Fourier transform ion cyclotron resonance mass spectrometry analysis. Using L‐HULIS as a secondary tracer of BrC, it was determined that the contribution of secondary sources to water‐soluble BrC (WS‐BrC) in source emission samples is significantly smaller than in PM2.5from five Chinese cities, supporting our method. In the five cities, secondary source derived via L‐HULIS contributes a dominant potion (80% ± 3.5%) of WS‐BrC at 365 nm during the summer, which is approximately twice as high as during the winter (45% ± 4.9%). Radiocarbon isotope (14C) analysis provides additional constraints to the sources of L‐HULIS‐derived secondary WS‐BrC in urban PM2.5, suggesting that aged biomass burning is the dominant contributor to secondary WS‐BrC in winter, and biogenic emission is dominant during summer. This study is the first report on identification of secondary sources of BrC using the fluorescence technique. It demonstrates the potential of this method in characterizing non‐fossil source secondary BrC in the atmosphere. Brown carbon (BrC) originates from primary combustion emissions and secondary formation, with large source‐dependent uncertainties of radiative forcing. Direct measurements to separate the primary and secondary BrC are challenging due to the chemical complexity. Recent online studies have shown that excitation‐emission matrix fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis identified some fluorescent components that may be linked to secondary sources. However, there is a knowledge gap on whether PARAFAC components correlate closely with atmospheric secondary chemical components, particularly biogenic and anthropogenic secondary organic aerosol, as their precursors can also form secondary BrC chromophores. We established the correlations between PARAFAC components and secondary organic aerosol tracers and compound oxidations to identify the long‐emission‐wavelength humic‐like component as a secondary source tracer of BrC. Then, we estimated non‐fossil source secondary BrC in urban aerosols during the winter and summer. Our studies provide references for quantifying secondary sources of BrC in the atmosphere. A fluorescence‐based method was developed to investigate secondary sources of water‐soluble brown carbon in five cities in ChinaThe contribution of secondary sources to water‐soluble brown carbon in the summer is approximately twice as high as during the winterThis secondary water‐soluble brown carbon was more associated with aging biomass burning in winter and biogenic emissions in summer A fluorescence‐based method was developed to investigate secondary sources of water‐soluble brown carbon in five cities in China The contribution of secondary sources to water‐soluble brown carbon in the summer is approximately twice as high as during the winter This secondary water‐soluble brown carbon was more associated with aging biomass burning in winter and biogenic emissions in summer

Humic‐like substances (HULIS) are significant contributor to the light absorption of water‐soluble brown carbon (WSBrC), which contains certain strong light‐absorbing chemical components that are not well understood, impeding the assessment of WSBrC's climate impact. China as the hotspot regions with high loading of WSBrC characterized by high light‐absorbing capacity, here, we investigated the sources and atmospheric processes (δ13C–Δ14C), molecular composition (Fourier transform ion cyclotron resonance mass spectrometry), and light absorption properties (UV spectrophotometry) of HULIS in PM2.5from 10 Chinese cities. HULIS‐C was major contributor to the light absorption coefficient (70.5 ± 6.6%) of WSBrC at 365 nm, which was more enriched with fossil sources (48.0 ± 9.0% vs. 30.3 ± 13.9%) but depleted in 13C (δ13C: −25.6 ± 0.9‰ vs. −22.4 ± 1.0‰) relative to non‐HULIS‐C. This suggests that the fossil components in HULIS are more recalcitrant to oxidative aging and exhibit higher light‐absorbing capacity, while the non‐fossil organic carbon is more likely to be oxidatively bleached into small, colorless, and highly polar molecules (i.e., non‐HULIS). Aromatic components are the major strong light‐absorbing fossil components in HULIS, dominantly originating from coal combustion (>77%). Non‐negative matrix factorization model showed that aromatic molecules from coal combustion have higher molecular weight and lower oxidation levels than biomass burning, potentially making them to be photo‐recalcitrant compounds. Our finding that coal combustion‐derived BrC maybe more persistent in the atmosphere and has greater long‐term impact on climate than BrC derived from biomass burning is an important consideration in climate models and mitigation policies. Both the loading and light‐absorbing capacity of water‐soluble brown carbon (WSBrC) are high in China, but little is known about sources and atmospheric processes of strong light‐absorbing components in WSBrC. Humic‐like substances (HULIS) account for a significant fraction of light absorption by WSBrC, which may contain strong light‐absorbing components. Through dual carbon isotopic analysis, we discovered that HULIS‐C from 10 Chinese cities had relatively higher fossil sources contribution but lower δ13C values compared to non‐HULIS‐C. This indicates that the fossil components in HULIS not only possess a higher light‐absorbing capacity but are also more resistant to oxidative aging than non‐fossil components. The higher light‐absorbing capacity and resilience of fossil components can be attributed to the enrichment of aromatic compounds derived from coal combustion. Using the non‐negative matrix factorization model, we found that coal combustion tends to generate aromatic compounds with higher molecular weight and lower oxidation‐to‐carbon (O/C: 0.31 ± 0.03 vs. 0.50 ± 0.07) ratios than biomass burning. This characteristic may contribute to the recalcitrant property of coal combustion‐derived HULIS. Our findings highlight that coal combustion‐derived BrC may persists longer in the atmosphere and has a greater long‐term impact on climate than that derived from biomass burning. The aromatic components with strong light‐absorbing capacity in HULIS mainly originated from coal combustion, enhancing light‐absorbing capacity of HULIS‐C and making it more recalcitrant to oxidative aging.

In this article, we develop online multistage decisions for procuring and dispatching generators with diverse capabilities to provably ensure reliability of power grid operations under high renewable uncertainty. We jointly consider both the day-ahead reliability assessment commitment (RAC) and the real-time dispatch problems. We first focus on the real-time dispatch problem and define “maximally robust algorithms,” in the sense that they are not dominated by any other algorithm in terms of reliability. We characterize a class of maximally robust algorithms using the concept of “safe dispatch set,” which also provides conditions for verifying grid reliability for RAC. However, in general, such safe dispatch sets may be difficult to compute. We then develop efficient computational algorithms for characterizing the safe dispatch sets. Specifically, for a simpler single-bus two-generator case, we show that the safe dispatch sets can be exactly characterized by a polynomial number of convex constraints. Then, based on this two-generator characterization, we develop a new solution for the multibus multigenerator case using the idea of virtual demand splitting (VDS), which can effectively compute a suitable subset of the safe dispatch set. A distinct advantage of our proposed approach is that it intelligently exploits the complementary capabilities of generators with different ramping capabilities, and thus leads to a larger safe dispatch set than existing approaches in the literature based purely on affine policies. Our numerical results on an IEEE 30-bus system demonstrate that a VDS-based solution outperforms the standard approaches in the literature in terms of reliability, without sacrificing economy.

Polychlorinated biphenyls (PCBs) were not widely manufactured or used in China before they became the subject of international bans on production. Recent work has shown that they have reached China associated with imported wastes and that there are considerable unintentional sources of PCBs that have only recently been identified. As such, it was hypothesized that the source inventory and profile of PCBs may be different or unique in China, compared to countries where they were widely used and which have been widely studied. For the first time in this study, we undertook a complete analysis of 209 PCB congeners and assessed the contribution of unintentionally produced PCBs (UP-PCBs) in the atmosphere of China, using polyurethane foam passive air samplers (PUF-PAS) deployed across a wide range of Chinese locations. ∑209PCBs ranged from 9 to 6856 pg/m3(median: 95 pg/m3) during three deployments in 2016–2017. PCB 11 was one of the most detected congeners, contributing 33 ± 19% to ∑209PCBs. The main sources to airborne PCBs in China were estimated and ranked as pigment/painting (34%), metallurgical industry/combustion (31%), e-waste (23%), and petrochemical/plastic industry (6%). For typical Aroclor-PCBs, e-waste sources were dominated (>50%). Results from our study indicate that UP-PCBs have become the controlling source in the atmosphere of China, and an effective control strategy is urgently needed to mitigate emissions from multiple industrial sources.

Although polychlorinated biphenyls (PCBs) have been banned for several decades, they are still detected with elevated levels due to their unintentional production from combustion and industrial thermal processes (UP-PCBs). To investigate the composition and current levels of UP-PCBs and understand which sources are controlling PCB burdens in ambient atmosphere, air samples were collected from August 2012 to August 2015 at a background site in east China. An unexpected high abundance of PCB47+48+75 was observed to be the predominant congener with an average concentration of 786 ± 637 pg/m3. It accounted for 48 ± 16% of ΣPCBs, followed by PCB51 (10 ± 4%), PCB11 (8 ± 6%), and PCB68 (7 ± 3%). Seasonal variations with high levels in summer and lowest levels in winter were observed for PCB47+48+75, 51, and 68. These tetrachlorobiphenyl congeners were strongly correlated with temperature (r2> 0.7), suggesting the control of temperature-dependent volatilization processes from contaminated surfaces. The decreased occurrence of PCB47+48+75, 51, and 68 in commercial products and their negative correlations (|r| < 0.35) with polycyclic aromatic hydrocarbon (PAHs) and weak correlation with other PCB congeners suggested unique unintentional sources that differ from combustion and industrial thermal processes or pigment, such as the use of polymer sealant, for PCB47+48+75, 51, and 68 in the ambient air.

Monosaccharides are important tracers of pollution aerosol from biomass burning. Air sampling of monosaccharides is often conducted using active samplers. However, applicability of sampling monosaccharides using polyurethane foam passive air samplers (PUF–PASs) has not been investigated, since passive air samplers are often applied to monitor semivolatile organic contaminants in large scale and remote area. Our study successfully collected atmospheric monosaccharides using PUF–PASs, providing a valuable tool for monosaccharides sampling. PUF–PAS sampling rates for individual monosaccharides were calibrated using an active sampler for 92 days, and were 1.1, 1.5, and 1.1 m3/d for levoglucosan, mannosan, and galactosan, respectively. Degradation of monosaccharides in PUF–PAS was demonstrated to be negligible by spike test of 13C-labeled levoglucosan. Furthermore, passive sampling was carried out at 11 sites in the Pearl River Delta of Southern China from January to April and July to September of 2015. Monosaccharide concentrations derived from PUF–PASs were comparable with the reported data obtained by active sampling, demonstrating that the PUF–PAS approach is valid for monosaccharides monitoring. On the basis of our approach, we found that there is a clear correlation between the monosaccharide concentrations and the MODIS fire activities during January–April.

This study aimed for the first time to reconstruct historical exposure profiles for PCBs to the Chinese population, by examining the combined effect of changing temporal emissions and dietary transition. A long-term (1930–2100) dynamic simulation of human exposure using realistic emission scenarios, including primary emissions, unintentional emissions, and emissions from e-waste, combined with dietary transition trends was conducted by a multimedia fate model (BETR-Global) linked to a bioaccumulation model (ACC-HUMAN). The model predicted an approximate 30-year delay of peak body burden for PCB-153 in a 30-year-old Chinese female, compared to their European counterpart. This was mainly attributed to a combination of change in diet and divergent emission patterns in China. A fish-based diet was predicted to result in up to 8 times higher body burden than a vegetable-based diet (2010–2100). During the production period, a worst-case scenario assuming only consumption of imported food from a region with more extensive production and usage of PCBs would result in up to 4 times higher body burden compared to consumption of only locally produced food. However, such differences gradually diminished after cessation of production. Therefore, emission reductions in China alone may not be sufficient to protect human health from PCB-like chemicals, particularly during the period of mass production. The results from this study illustrate that human exposure is also likely to be dictated by inflows of PCBs via the environment, waste, and food.

In this paper, we study how to utilize forecasts to design online electrical vehicle (EV) charging algorithms that can attain strong performance guarantees. We consider the scenario of an aggregator serving a large number of EVs together with its background load, using both its own renewable energy (for free) and the energy procured from the external grid. The goal of the aggregator is to minimize its peak procurement from the grid, subject to the constraint that each EV has to be fully charged before its deadline. Further, the aggregator can predict the future demand and the renewable energy supply with some levels of uncertainty. We show that such prediction can be very effective in reducing the competitive ratios of online control algorithms, and even allow online algorithms to achieve close-to-offline-optimal peak. Specifically, we first propose a 2-level increasing precision model (2-IPM), to model forecasts with different levels of accuracy. We then develop a powerful computational approach that can compute the optimal competitive ratio under 2-IPM over any online algorithm, and also online algorithms that can achieve the optimal competitive ratio. Simulation results show that, even with up to 20% day-ahead prediction errors, our online algorithms still achieve competitive ratios fairly close to 1, which are much better than the classic results in the literature with a competitive ratio of $e$ . The second contribution of this paper is that we solve a dilemma for online algorithm design, e.g., an online algorithm with good competitive ratio may exhibit poor average-case performance. We propose a new Algorithm-Robustification procedure that can convert an online algorithm with good average-case performance to one with both the optimal competitive ratio and good average-case performance. We demonstrate via trace-based simulations the superior performance of the robustified version of a well-known heuristic algorithm based on model predictive control. [ABSTRACT FROM PUBLISHER]

Abstract

Atmospheric nitrogen‐containing organic compounds (NOCs) are critical components of global nitrogen deposition and light‐absorption species. The sources and compositions of NOCs are complex and remain largely unknown. Here, NOCs in 55 ambient aerosol samples collected in Guangzhou, South China, were analyzed via ultrahigh‐resolution Fourier transform ion cyclotron resonance mass spectrometry in negative‐ion and positive‐ion electrospray ionization (ESI) modes. The molecular compositions of NOCs measured via ESI– and ESI+ exhibited considerable differences. NOCs detected in the negative mode were mainly composed of highly oxygenated organic nitrates (O/N = 6), whereas NOCs detected in the positive mode were mainly composed of reduced nitrogen‐containing compounds (e.g., amides and amino acids). CHN compounds potentially corresponding to amines and alkaloids showed low abundance in the detection modes. Non‐metric multidimensional scaling and individual compound correlation analyses showed that the molecular compositions of NOCs were mainly affected by anthropogenic activities and meteorological parameters. For example, anthropogenic activities such as biomass burning and secondary nitrogen‐chemistry processes led to the accumulation of aromatic and highly oxygenated NOCs during winter. During summer, higher OH radical concentrations and temperatures will result in more prevalent or persistent reduced aliphatic NOCs, particularly lipid‐like amines. Some variables (e.g., relative humidity) have distinct effects on the variation of different types of NOCs. More research is needed to reveal the influencing mechanisms. This study clarifies the molecular compositions of NOCs and the mechanisms by which various factors influence the molecular variations. The findings can guide the assessment of NOCs evolution and deposition. Negative and positive electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI‐FT‐ICR‐MS) was used to characterize the molecular composition of nitrogen‐containing organic compounds (NOCs) from aerosol samples in Guangzhou. It was determined that a large amount of various NOCs are present in the samples, with NOCs in highly oxidative and reduced states can be roughly identified by distinct ionization modes. By combining the ESI‐FT‐ICR‐MS results and statistical analysis, the factors that associated with the distribution of NOCs and how these factors worked were identified. Anthropogenic activities and meteorological parameters (e.g., temperature and oxidation levels) are the two important drivers that led to the variations of NOCs, resulting to inverse molecular patterns with different response to aromatic/highly unsaturated and saturated structures, respectively. This study provides a useful clue for studying NOCs in complex system, bridges the links between the filed observation and knowledge about sources and formation pathways of NOCs that derived from controlled laboratory studies. Most of identified CHON− species had O/N ≥ 3 and showed higher O/C ratios than CHON+ species; CHN only constituted small fraction of nitrogen‐containing organic compounds (NOCs)Biomass burning and secondary inorganic‐nitrogen processes lead to the accumulation of aromatic and phenolic NOCs during winterHigher OH radical concentrations and temperatures result in more prevalent or persistent reduced aliphatic NOCs in summer Most of identified CHON− species had O/N ≥ 3 and showed higher O/C ratios than CHON+ species; CHN only constituted small fraction of nitrogen‐containing organic compounds (NOCs) Biomass burning and secondary inorganic‐nitrogen processes lead to the accumulation of aromatic and phenolic NOCs during winter Higher OH radical concentrations and temperatures result in more prevalent or persistent reduced aliphatic NOCs in summer

Abstract: By taking into account the valence electron number and periodic number of constituting metals, a new method is first proposed to calculate the structural enthalpy in the Miedema’s model and the modified Miedema’s model is then used to predict the formation of metastable phases in Ni-Ti system. To testify the relevance of the present prediction, the multilayered films of Ni1−x Ti x (x=27.3, 30.5, 42.4, 83.1, 89) are prepared and irradiated by 200 keV xenon ions. Experiment results reveal that uniform amorphous phases are obtained in the Ni72.7Ti27.3, Ni69.5Ti30.5, and Ni57.6Ti42.4 films by increasing the irradiation dose. While for the Ni16.9Ti83.1 and Ni11Ti89 films, an hcp Ti-based solid solution phase and a bcc Ti-rich solid solution phase coexist upon irradiation dose higher than 6×1014 Xe+/cm2. The predictions of relative stabilities of metastable phases in Ni-Ti system by the modified Miedema’s model match well with IBM experiments, thus justifying the modification proposed in the present study.

An increasing number of alternative flame retardants (FRs) are being introduced, following the international bans on the use of polybrominated diphenyl ether (PBDE) commercial mixtures. FRs’ production capacity has shifted from developed countries to developing countries, with China being the world’s largest producer and consumer of FRs. These chemicals are also imported with e-waste to China. Therefore, it is important to understand the current status of regulated brominated FRs, their phase-out in China, and their replacement by alternatives. In this study, a broad suite of legacy and alternative FRs, including eight PBDEs, six novel brominated FRs (NBFRs), two dechlorane plus variants (DPS), and 12 organophosphate FRs (OPFRs) were evaluated in the air of 10 large Chinese cities in 2018. OPFRs are the most prevalent FRs in China, exhibiting a wide range of 1–612 ng/m3, which is several orders of magnitude higher than PBDEs (1–1827 pg/m3) and NBFRs (1–1428 pg/m3). BDE 209 and DBDPE are the most abundant compounds in brominated FRs (>80%). The North China Plain (NCP, excluding Beijing), Guangzhou, and Lanzhou appear to be three hotspots, although with different FR patterns. From 2013/2014 to 2018, levels of PBDEs, NBFRs, and DPs have significantly decreased, while that of OPFRs has increased by 1 order of magnitude. Gas-particle partitioning analysis showed that FRs could have not reached equilibrium, and the steady-state model is better suited for FRs with a higher log KOA(>13). To facilitate a more accurate FR assessment in fine particles, we suggest that, in addition to the conventional volumetric concentration (pg/m3), the mass-normalized concentration (pg/g PM2.5) could also be used.

Under the framework of second moment approximation of the tight binding theory, a realistic interatomic potential is first developed for the Ni--Zr--Al ternary metal system and then applied to predict the glass-forming ability of the system through molecular dynamics simulation. It is found that when the composition falls into the hexagonal region defined by six vertexes of Ni20Zr80Al0, Ni0Zr65Al35, Ni0Zr25Al75, Ni20Zr0Al80, Ni40Zr0Al60, and Ni77Zr23Al0, the super-saturated solid solution becomes unstable and spontaneously turns into the disorder state, i.e., the metallic glass state. The defined composition region could be considered as a quantitative glass-forming ability, within which the Ni--Zr--Al ternary metallic glass is predicted to be energetically favored to form. Interestingly, the prediction based on the interatomic potential matches well with experimental observations.