Impact of biogenic SOA loading on the molecular composition of wintertime PM2.5 in urban Tianjin: an insight from Fourier transform ion cyclotron resonance mass spectrometry

Biomass burning is one of the key sources of urban aerosols in the North China Plain, especially in winter when the impact of secondary organic aerosols (SOA) formed from biogenic volatile organic compounds (BVOCs) is generally considered to be minor. However, little is known about the influence of biogenic SOA loading on the molecular composition of wintertime organic aerosols. Here, we investigated the water-soluble organic compounds in fine particles (PM2.5) from urban Tianjin by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Our results show that most of the CHO and CHON compounds were derived from biomass burning; they contain O-poor and highly unsaturated compounds with aromatic rings, which are sensitive to photochemical reactions, and some of which probably contribute to light-absorbing chromophores. Under moderate to high SOA loading conditions, the nocturnal chemistry is more efficient than photooxidation to generate secondary CHO and CHON compounds with high oxygen content. Under low SOA-loading, secondary CHO and CHON compounds with low oxygen content are mainly formed by photochemistry. Secondary CHO compounds are mainly derived from oxidation of monoterpenes. But nocturnal chemistry may be more productive to sesquiterpene-derived CHON compounds. In contrast, the number- and intensity-weight of S-containing groups (CHOS and CHONS) increased significantly with the increase of biogenic SOA-loading, which agrees with the fact that a majority of the S-containing groups are identified as organosulfates and nitrooxy-organosulfates that are derived from the oxidation of BVOCs. Terpenes may be potential major contributors to the chemical diversity of organosulfates and nitrooxy-organosulfates under photo-oxidation. While the nocturnal chemistry is more beneficial to the formation of organosulfates and nitrooxy-organosulfates under low SOA-loading. The SOA-loading is an important factor associating with the oxidation degree, nitrate group content and chemodiversity of nitrooxy-organosulfates. Furthermore, our study suggests that the hydrolysis of nitrooxy-organosulfates is a possible pathway for the formation of organosulfates.</p

Behavior Management Training for Parents of Children with Preschool ADHD Based on Parent-Child Interactions: A Multicenter Randomized Controlled, Follow-Up Study

Objective. There is a need to develop optimized, evidence-based parent training programs tailored for preschoolers with attention deficit hyperactivity disorder (ADHD). The objective of this study was to explore a behavioral management training program aimed at the parents of preschool children with ADHD, which directly analyzes parent-child interaction from the perspective of system theory, and the intervention effect on ADHD in preschool children. Methods. A multicenter randomized controlled study was conducted using system-based group therapy with 62 parents of preschool children with ADHD aged four to six years. ADHD symptoms, behavioral and emotional problems, and social functioning were compared with 61 control children whose parents did not receive training by applying the ADHD Rating Scale (ADHD-RS), Strengths and Difficulties Questionnaire (SDQ), and Questionnaire-Children with Difficulties (QCD) at the time of subject entry and at two and six months of entry, respectively. Results. The results of the ADHD-RS assessment showed that children in the intervention group had significantly lower factor scores for attention deficit, hyperactivity, and impulsivity than the children in the control group after parental training and at follow-up (P0.05). Compared with the control group, the total scores of the QCD scale and the scores of each factor in the intervention group remained significantly higher at the follow-up (P<0.05). Conclusion. After continuous intervention for eight weeks, parents were able to help the children with preschool ADHD to improve their ADHD symptoms and emotional behavioral and social functioning significantly, and the efficacy was maintained at the four-month follow-up; the systemic-based parent training in behavior management (PTBM) is applicable to the treatment of preschool ADHD and is worth promoting

Interstitial Hydrogen Atom Modified PdPt Nanosheets for Efficient Ethanol Electro-oxidation with High C–C Bond Cleavage Selectivity

Direct ethanol fuel cells (DEFCs) are a type of promising portable power source with low environmental pollution and high energy density. However, the further commercialization of DEFCs is hindered by the incomplete oxidation of ethanol on the electrocatalysts. Herein, we report a successful synthesis of ultrathin PdPtH nanosheets (NSs) for the first time by the in situ formation of interstitial hydrogen atoms accompanied by wet-chemical coreduction of Pd and Pt precursors. The PdPtH NSs possess selectivity of 15.1% related to C–C bond splitting for ethanol complete oxidation to CO2 through the C1 pathway at a low potential, while the contrast selectivity is 4.8% for Pt black, 9.2% for commercial Pd black, and 11.7 for PdH NSs, respectively. Accordingly, the PdPtH NSs exhibited enhanced catalytic activity in comparison to the counterparts. The mass activity toward ethanol oxidation reaction (EOR) of the PdPtH NSs is 5.2 times and 87 times higher than that of commercial Pd and commercial Pt, respectively. The structure stability and growth mechanism of the PdPtH NSs were also investigated. The results of in situ Fourier transform infrared spectra revealed a stronger C–C bond cleavage ability and CO stripping shows the better antipoisoning properties of the PdPtH NSs arising from the cooperation of the PdPt alloy with interstitial H atoms

A New Structural Classification Scheme for Dissolved Organic Sulfur in Urban Snow from North China

The chemical composition of dissolved organic sulfur in snow is important in understanding the sources and scavenging processes of atmospheric organic matter. Snow samples collected simultaneously from four megacities in North China were analyzed using ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry. The modified oxygen and redefined aromaticity index help in the interpretation of the possible structural information and evaluation of the aromaticity of sulfur-containing molecules. By extending these parameters, we provide a new structural classification for organic sulfur species in the atmosphere. With the new classification, the oxidized (O/S > 3) and less oxidized (O/S ≤ 3) sulfur-containing molecules can be easily distinguished. Typical known secondary organosulfates and sulfonates and anthropogenically derived anionic surfactants verified the validity of this new classification. The new classification was applied to the molecular characterization of dissolved organic sulfur in snow samples. More than one hundred (138–150) of the molecules with medium O/S ratios of 5–11 and a low to medium mass range of <500 Da are related with typical known secondary organosulfates and anthropogenically derived anionic surfactants. Our study provides new insights into the molecular compositions of organic sulfur species in ambient air, although their atmospheric behaviors between the snow–aerosol interfaces warrant further examination

Controlled Encapsulation of Flower-like Rh–Ni Alloys with MOFs via Tunable Template Dealloying for Enhanced Selective Hydrogenation of Alkyne

For new composite materials with functional nanoparticles (NPs) embedded in metal organic frameworks (MOFs), rational design and precise control over their architectures are imperative for achieving enhanced performance and novel functions. Especially in catalysis, the activity and selectivity of such composite materials are strongly determined by the encapsulation state and thickness of the MOF shell, which greatly influences the diffusion and adsorption of substance molecules onto the NP surface. In this study, MOF-74­(Ni)-encapsulated Rh–Ni hierarchical heterostructures (Rh–Ni@MOF-74­(Ni)) were successfully constructed using magnetic Rh–Ni-alloyed nanoflowers (NFs) as a self-sacrificial template. Strikingly, the encapsulation state and thickness of the formed MOF shell were well-tuned via template dealloying by changing the Ni content in the Rh–Ni NFs template. More interestingly, such unique Rh–Ni composites encapsulated with MOFs as catalysts could be magnetically recyclable and exhibited enhanced catalytic performance for the selective hydrogenation of alkynes to cis products, owing to the confinement effect of the MOF shell, as compared to their pristine counterparts

Abundance and diurnal trends of fluorescent bioaerosols in the troposphere over Mt. Tai, China, in spring

Primary biological aerosol particles are ubiquitous in the global atmosphere and can affect cloud formation, deteriorate air quality, and cause human infections. Mt. Tai (1,534 m a.s.l.) is an elevated site in the North China Plain where atmospheric aerosols reflect both regional advection and long-range transport. In this study, we deployed a Wideband Integrated Bioaerosol Sensor (WIBS-4A) and collected total suspended particles and eight-stage size-segregated aerosol samples at the summit of Mt. Tai in spring from 21 March to 8 April 2017 to quantify the abundance, size distributions, and diurnal variations of fluorescent bioaerosols and to investigate the effect of different fluorescence thresholds of WIBS for ambient bioaerosol recognition. During the whole sampling period, the number concentration of fluorescent particles (&gt;0.8 μm) was 647 ± 533 L−1, accounting for 26.9% ± 10.0% by number of the total particles in that size range. Three-dimensional excitation-emission matrix fluorescence of water-soluble organic matter in size-segregated aerosols shows that humic-like substances (HULIS) are mainly in the fine mode (&lt;2.1 μm) while protein-like substances are mainly in the coarse mode (&gt;2.1 μm). From the diurnal variation, it is shown that bioaerosols can undergo transformation during long-range transport and contribute to HULIS. For bioaerosol recognition, we find that 6σ-threshold can lead to better classification of fluorescent aerosol particles for fungal spores. Overall, our results constrain the abundance of primary bioaerosols in the troposphere over East Asia and elucidate the processes for their evolution via mountain/valley breezes and long-range transport

Dominant contribution of combustion-related ammonium during haze pollution in Beijing

Aerosol ammonium (NH4+), mainly produced from the reactions of ammonia (NH3) with acids in the atmosphere, has significant impacts on air pollution, radiative forcing, and human health. Understanding the source and formation mechanism of NH4+ can provide scientific insights into air quality improvements. However, the sources of NH3 in urban areas are not well understood, and few studies focus on NH3/NH4+ at different heights within the atmospheric boundary layer, which hinders a comprehensive understanding of aerosol NH4+. In this study, we perform both field observation and modeling studies (the Community Multiscale Air Quality, CMAQ) to investigate regional NH3 emission sources and vertically resolved NH4+ formation mechanisms during the winter in Beijing. Both stable nitrogen isotope analyses and CMAQ model suggest that combustion-related NH3 emissions, including fossil fuel sources, NH3 slip, and biomass burning, are important sources of aerosol NH4+ with more than 60% contribution occurring on heavily polluted days. In contrast, volatilization-related NH3 sources (livestock breeding, N-fertilizer application, and human waste) are dominant on clean days. Combustion-related NH3 is mostly local from Beijing, and biomass burning is likely an important NH3 source (∼15%–20%) that was previously overlooked. More effective control strategies such as the two-product (e.g., reducing both SO2 and NH3) control policy should be considered to improve air quality.</p