Abstract. Understanding the compositions and evolution of atmospheric organic vapors is crucial for exploring their impact on air quality. However, the molecular and seasonal characteristics of organic vapors in urban areas, with complex anthropogenic emissions and high variability, remain inadequately understood. In this study, we conducted measurements in urban Beijing during 2021–2022 covering four seasons using a Vocus-PTR, an improved Proton Transfer Reaction-Mass Spectrometry (PTR-MS). During the measurement period, a total of 895 peaks are observed, and 543 of them can be assigned to formulas. The contribution of CxHyOz species is most significant, which compose up to 53.7 % of the number and 76.0 % of the mass of total organics. With enhanced sensitivity and mass resolution, various sub-ppt level species and organics with multiple oxygens (≥3) were discovered. When counting the species number, 42.2 % of the organics measured are at sub-ppt level and 37.8 % of the species contain 3–8 oxygens. Organic vapors with multiple oxygens mainly consist of intermediate volatility and semi-volatile compounds, and many of them are found to be the multi-generational oxidation products of various volatile organic precursors. In summer, the fast photooxidation process generates organic vapors with multiple oxygens, and leads to an increase in both their concentration and proportion. While in other seasons, the variations of organic vapors with multiple oxygens are closely correlated with those of organic vapors with 1–2 oxygens, which could be heavily influenced by primary emissions. Organic vapors with low oxygen content (≤ 2 oxygens) are comparable to the results obtained by traditional PTR-MS measurements in both urban Beijing and neighboring regions.
Gaseous oxygenated organic molecules (OOMs) are crucial precursors of atmospheric organic aerosols. OOMs in urban atmospheres have complex compositions, posing challenges to understanding their formation, evolution, and influences. In this study, we identify 2403 atmospheric gaseous OOMs in urban Beijing using online nitrate-based chemical ionization Orbitrap mass spectrometry based on one-year atmospheric measurements. We find that OOMs in urban atmospheres can be identified with higher accuracy and wider coverage, compared to previously used online mass spectrometry. With optimized OOM resolving capabilities, previous knowledge of OOMs in urban atmospheres can be expanded. First, clear homologous and oxygen-addition characteristics of the OOMs are revealed. Second, OOMs with lower concentrations or higher masses are identified and characterized with high confidence, e.g., OOMs with masses above 350 Da. In particular, dimers of OOMs (e.g., C
This research investigated the use of composite coagulants for enhanced coagulation of algae‐containing water from Taihu Lake in China. The composite coagulants comprised aluminum sulfate (AS) and poly dimethyl diallyl ammonium chloride (PDMDAAC) of different intrinsic viscosity values (0.55‐ .99 dL/g) and different mass percentages (5‐20%) in formulation. For algae‐containing water with a temperature of 29‐ 0oC and algal content of .52 × 104 cells/mL, algae removal rates of 81.11% and 85.89‐90.5 %, respectively, were realized using AS at a dose of 7.78 mg/L and AS/PDMDAAC at formulations of 0.55/5‐ .99/20% and doses of 6.55‐ .54 mg/L when 2‐ntu residual turbidity of effluent water after sedimentation was required. The removal rates of chemical oxygen demand and ammonia using AS/PDMDAAC in algae‐containing water were higher than those using AS alone. Composite coagulants could reduce required doses and decrease algal content in effluent water when 1‐ntu residual turbidity is required. When identical doses were used, 1.5 /10% AS/PDMDAAC outperformed AS combined with prechlorination.
Liquid crystal monomers (LCMs) in liquid crystal displays (LCDs) may be released into the environment, especially in electronic waste (e-waste) recycling industrial parks with a high pollution risk. However, little has been known about the environmental release and human exposure to LCMs until now. Herein, a total of 45 LCMs were detected in LCDs of commonly used smartphones and computers by high-resolution mass spectrometry with suspect screening analysis. Fluorinated biphenyls and their analogs were the dominant LCMs. Based on available standards of the screening results and previous studies, 55 LCMs were quantified in samples from an e-waste recycling industrial park in Central China. The LCMs were frequently detected in outdoor dust (n = 43), workshop #1 indoor dust (n = 53), and hand (n = 43) and forehead wipes (n = 43), with median concentrations of 6950 ng/g, 67,400 ng/g, 46,100 ng/m2, and 62,100 ng/m2, respectively. The median estimated daily intake values of the LCMs via dust ingestion and dermal absorption were 48.3 and 16.5 ng/kg body weight/day, respectively, indicating a high occupational exposure risk of these compounds. In addition, 16 LCMs were detected in the serum of eight elderly people (≥60 years old) with over 5 years of experience in e-waste dismantling operations, resulting in a total concentration range of 3.9–26.3 ng/mL.
This paper considers the inverse problem of determining an unknown source which depends only one spatial variable on modified Helmholtz equation. This problem is well known to be severely ill-posed, the solution (if it exists) does not depend continuously on the data. Landweber iterative regularization method is used to solve this inverse source problem. The Hölder type error estimates are obtained between the exact solution and regularization solutions under an a priori and an a posteriori regularization parameters choice rules, respectively. Numerical examples are provided to show the effectiveness of the proposed method.
In order to facilitate the calibration and scale of pyroelectric detectors for environmental dose monitoring, a new simple standard irradiation device was designed.Through Monte Carlo software, the uniformity of radiation field, absorbed dose of pyroelectric detector and scattering contribution rate of this device are simulated.The simulation results show that the new simple standard irradiator satisfies the national standards and can fulfill the calibration and scaling requirements of pyroelectric detectors for environmental dose monitoring.
Abstract. The predominating role of aerosol Fuchs surface area, AFuchs, in determining the occurrence of new particle formation (NPF) events in Beijing was elucidated in this study. The analysis was based on a field campaign from 12 March to 6 April 2016 in Beijing, during which aerosol size distributions down to ∼ 1 nm and sulfuric acid concentrations were simultaneously monitored. The 26 days were classified into 11 typical NPF days, 2 undefined days, and 13 non-event days. A dimensionless factor, LΓ, characterized by the relative ratio of the coagulation scavenging rate over the condensational growth rate (Kuang et al., 2010), was applied in this work to reveal the governing factors for NPF events in Beijing. The three parameters determining LΓ are sulfuric acid concentration, the growth enhancement factor characterized by contribution of other gaseous precursors to particle growth, Γ, and AFuchs. Different from other atmospheric environments, such as in Boulder and Hyytiälä, the daily-maximum sulfuric acid concentration and Γ in Beijing varied in a narrow range with geometric standard deviations of 1.40 and 1.31, respectively. A positive correlation between the estimated new particle formation rate, J1.5, and sulfuric acid concentration was found with a mean fitted exponent of 2.4. However, the maximum sulfuric acid concentrations on NPF days were not significantly higher (even lower, sometimes) than those on non-event days, indicating that the abundance of sulfuric acid in Beijing was high enough to initiate nucleation, but may not necessarily lead to NPF events. Instead, AFuchs in Beijing varied greatly among days with a geometric standard deviation of 2.56, whereas the variabilities of AFuchs in Tecamac, Atlanta, and Boulder were reported to be much smaller. In addition, there was a good correlation between AFuchs and LΓ in Beijing (R2 = 0.88). Therefore, it was AFuchs that fundamentally determined the occurrence of NPF events. Among 11 observed NPF events, 10 events occurred when AFuchs was smaller than 200 µm2 cm−3. NPF events were suppressed due to the coagulation scavenging when AFuchs was greater than 200 µm2 cm−3. Measured AFuchs in Beijing had a good correlation with its PM2.5 mass concentration (R2 = 0.85) since AFuchs in Beijing was mainly determined by particles in the size range of 50–500 nm that also contribute to the PM2.5 mass concentration.
China has sufficient historical evidence and international law to assert its sovereignty over the South China Sea. China’s construction of islands and reefs in the South China Sea is essentially a man-made accretion, and this behavior is legal and reasonable under international law. The nature of the construction in the South China Sea has not changed before and after the artificial accretion, nor does it harm the rights of neighboring countries. On the contrary, the construction of islands and reefs in the South China Sea not only ensures the safety of navigation channels, but also promotes the development of China and regional countries.
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