Abstract
Severe events of wintertime particulate air pollution in Beijing (winter haze) are associated with high relative humidity (RH) and fast production of particulate sulfate from the oxidation ...of sulfur dioxide (SO
2
) emitted by coal combustion. There has been considerable debate regarding the mechanism for SO
2
oxidation. Here we show evidence from field observations of a haze event that rapid oxidation of SO
2
by nitrogen dioxide (NO
2
) and nitrous acid (HONO) takes place, the latter producing nitrous oxide (N
2
O). Sulfate shifts to larger particle sizes during the event, indicative of fog/cloud processing. Fog and cloud readily form under winter haze conditions, leading to high liquid water contents with high pH (>5.5) from elevated ammonia. Such conditions enable fast aqueous-phase oxidation of SO
2
by NO
2
, producing HONO which can in turn oxidize SO
2
to yield N
2
O.This mechanism could provide an explanation for sulfate formation under some winter haze conditions.
Atmospheric amines – Part I. A review Ge, Xinlei; Wexler, Anthony S.; Clegg, Simon L.
Atmospheric environment (1994),
2011, 2011-1-00, 20110101, Letnik:
45, Številka:
3
Journal Article
Recenzirano
Amines are emitted by a wide range of sources and are ubiquitous atmospheric organic bases. Approximately 150 amines and about 30 amino acids have been identified in the atmosphere. We review the ...present knowledge of atmospherically relevant amines with respect to their sources, fluxes, and dynamics including gas-phase reactions, gas-to-particle conversion and deposition. The health effects of aliphatic and aromatic amines are briefly summarized as well as the atmospheric occurrence and reactivity of amino acids and urea.
► 154 amines, 32 amino acids and urea have been identified in the atmosphere. ► Sources, fluxes, and dynamics of atmospheric amines and amino acids are reviewed. ► Health effects of aliphatic and aromatic amines are briefly summarized.
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•PM, SO2, CO reduced significantly, NO2 was less clear, and O3 increased significantly.•Excess health risks (ER) based on WHO guideline are two times than those from CAAQS ...guideline.•PM10 rather than PM2.5 contributed the most to ER.•~15%, ~85% and ~95% people in YRD, FWP and JJJ were exposed to polluted air (HAQI > 100) in 2018.•Population-normalized HAQI significantly added the inequality of people exposure to polluted air.
Air pollution events occurred frequently in China, and tremendous efforts were devoted to the reduction of air pollution in recent years. Here, analysis of ambient monitoring data of six criteria air pollutants from 367 Chinese cities during 2015–2018, showed that PM2.5, PM10, SO2 and CO were reduced significantly by 22.1%, 13.5%, 46.4% and 21.5%, respectively, NO2 reduction was less significant (6.3%) while O3 level instead increased over China (13.7%). Spatial distribution, seasonal, monthly and diurnal variations of the air pollutants during 2018, implicated of effective control measures, were discussed in details, especially for the five key densely populated regions of Jing-Jin-Ji (JJJ), Fen Wei Plains (FWP), Yangtze River Delta (YRD), Sichuan Basin (SCB) and Pearl River Delta (PRD). Moreover, excess health risks (ERs) of the six pollutants were estimated for 2018, and such risks was two times higher if the World Health Organization (WHO) air quality guideline rather than Chinese guideline was adopted. PM10 rather than PM2.5 was the dominant contributor to ERs, and the case with both PM2.5 and PM10 exceeding threshold values occupied ~1/3 of total days, yet contributed ~2/3 of total ERs. For 2018, the health-risk based air quality index (HAQI) was further calculated by combining health risks from multiple pollutants, and it was found that high HAQI mostly distributed in North China Plain (NCP). ~15%, ~85% and ~95% people in YRD, FWP and JJJ were exposed to polluted air (HAQI > 100), and population-normalized HAQI further added the inequality, JJJ and a small region of SCB had much higher HAQI (>280). Investigations on HAQI with socioeconomic factors show that total population, population density and built-up area presented an inverted U-shape, suggesting existence of Environmental Kuznets Curve (EKC), while a positive relationship was found between HAQI and share of secondary industry. Multiple regression analysis suggested that built-up area was the most prominent factor to HAQI, followed by the gross domestic product (GDP). The findings here demonstrate in great details the current characteristics of air pollution and its associated health risks in China, therefore providing important implications for effective air pollution control strategies in near future for different regions of China.
An alternative way has been proposed for the PVC-containing medical wastes valorization by co-hydrothermal carbonization (HTC) with lignocellulosic biomass. The organic-Cl in PVC can be converted to ...the inorganic-Cl via hydrolysis, defunctionalization, recondensation, and aromatization in the HTC process. Followed by the washing process with the condensed water, the inorganic-Cl with high water-solubility could be removed from the solid products (i.e. hydrochar). Lignin as a biomass component can significantly improve the dechlorination efficiency of PVC in the HTC process. Here, the dechlorination performance of lignocellulosic components is given as the following order: lignin > cellulose > hemicellulose. In addition, lignin can adjust the particle sizes of solid products by inhibiting the agglomeration in the order of lignin > hemicellulose > cellulose. In the pilot-scale HTC process, the addition of woodchips improves the dechlorination efficiency of hospital wastes (HW). The hydrochar particles with low-chlorine content and higher heating value could be used as a clean coal-alternative fuel.
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•An alternative method has been proposed for converting PVC wastes to energy.•Dechlorination efficiency was enhanced by co-HTC with lignocellulosic biomass.•Organic chlorine was transformed into the inorganic chlorine via the HTC process.•The dechlorination performance of lignocellulose was given: lignin > cellulose > hemicellulose.•Lignin can adjust the particle sizes of hydrochars by inhibiting the agglomeration.
Non-refractory submicron aerosol (NR-PM1) species measured by an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) along with collocated gaseous species are used to investigate the impacts of ...relative humidity (RH) on aerosol composition and evolution processes during wintertime in Beijing, China. Aerosol species exhibit strong, yet different RH dependence between low and high RH levels. At low RH levels (<50%), all aerosol species increase linearly as a function of RH, among which organics present the largest mass increase rate at 11.4 μg m−3/10% RH. Because the particle liquid water predicted by E-AIM model is very low and the temperature is relatively constant, the enhancement of aerosol species is primarily due to the decrease of wind speed. While the rates of increase for most aerosol species are reduced at high RH levels (>50%), sulfate presents an even faster increasing rate, indicating the significant impact of liquid water on sulfate production. The RH dependence of organic aerosol (OA) components is also quite different. Among OA components, coal combustion OA (CCOA) presents the largest enhancement in both mass concentration and contribution as a function of RH. Our results elucidate the important roles of liquid water in aerosol processing at elevated RH levels, in particular affecting sulfate and CCOA via aqueous-phase reaction and gas-particle partitioning associated with water uptake, respectively. It is estimated that aqueous-phase processing can contribute more than 50% of secondary inorganic species production along with an increase of aerosol particle acidity during the fog periods. However, it appears not to significantly enhance secondary organic aerosol (SOA) formation and the oxidation degree of OA.
•The RH impacts on aerosol composition and processes in Beijing were examined.•The RH shows the largest impact on sulfate and coal combustion OA during wintertime.•Aqueous processing appears not to significantly enhance SOA production and oxidation degree.
Hydrogen peroxide (H2O2) is an environment‐friendly and efficient oxidant with a wide range of applications in different industries. Recently, the production of hydrogen peroxide through direct ...electrosynthesis has attracted widespread research attention, and has emerged as the most promising method to replace the traditional energy‐intensive multi‐step anthraquinone process. In ongoing efforts to achieve highly efficient large‐scale electrosynthesis of H2O2, carbon‐based materials have been developed as 2e− oxygen reduction reaction catalysts, with the benefits of low cost, abundant availability, and optimal performance. This review comprehensively introduces the strategies for optimizing carbon‐based materials toward H2O2 production, and the latest advances in carbon‐based hybrid catalysts. The active sites of the carbon‐based materials and the influence of coordination heteroatom doping on the selectivity of H2O2 are extensively analyzed. In particular, the appropriate design of functional groups and understanding the effect of the electrolyte pH are expected to further improve the selective efficiency of producing H2O2 via the oxygen reduction reaction. Methods for improving catalytic activity by interface engineering and reaction kinetics are summarized. Finally, the challenges carbon‐based catalysts face before they can be employed for commercial‐scale H2O2 production are identified, and prospects for designing novel electrochemical reactors are proposed.
The latest advances in carbon‐based hybrid catalysts toward hydrogen peroxide (H2O2) production are reviewed. In particular, the design of functional groups and the dependence of electrolyte pH play important roles to further improve the selectivity of H2O2 production via the oxygen reduction reaction.
It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH‐20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID‐19) outbreak, ...than in 2019 (NYH‐19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH‐19 and NYH‐20. Much higher secondary aerosol fraction in PM2.5 were observed during NYH‐20 (73%) than during NYH‐19 (59%). During NYH‐20, PM2.5 levels correlated significantly with the oxidation ratio of nitrogen (r2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH‐20, despite the overall low atmospheric NO2 levels.
Plain Language Summary
In China, there are multiple cases (e.g., the 2008 Summer Olympics in Beijing and the 2010 World Expo in Shanghai) when combustion‐related emissions (e.g., NOx) were actively, and successfully, reduced to transiently improve air quality. During the extended Chinese Lunar New Year holiday in 2020 (between 24 January and 10 February), whole China was in an unprecedented state of shutdown, because most people were contained in their homes to reduce the spread of the novel coronavirus disease (COVID‐19). Mobility, energy demand, and industrial output remained far below their normal levels. Nevertheless, widespread haze pollution still occurred over Eastern China. To elucidate haze formation mechanisms, we performed comprehensive and continuous measurements of aerosol chemistry and physics in and out of Shanghai before, during, and after the Chinese New Year Holiday in 2019 and 2020, respectively. We argue that the synergistic effects of long‐range transport and atmospheric chemistry leading to the efficient conversion of NOx to particulate nitrate were the key of haze formation during the Chinese New Year Holiday of the COVID‐19 outbreak in Shanghai.
Key Points
Higher concentrations and distinct compositions of aerosol particles were observed during the COVID‐19 shutdown
Fast formation of secondary inorganic aerosol contributed to high aerosol mass loading
Longer‐range, regional transport facilitated and enhanced particulate nitrate formation
In this study, we evaluated the variations of air quality in Lanzhou, a typical city in Northwestern China impacted by the COVID‐19 lockdown. The mass concentration and chemical composition of ...non‐refractory submicron particulate matter (NR‐PM1) were determined by a high‐resolution aerosol mass spectrometer during January‐March 2020. The concentration of NR‐PM1 dropped by 50% from before to during control period. The five aerosol components (sulfate, nitrate, ammonium, chloride, and organic aerosol OA) all decreased during the control period with the biggest decrease observed for secondary inorganic species (70% of the total reduction). Though the mass concentration of OA decreased during the control period, its source emissions varied differently. OA from coal and biomass burning remained stable from before to during control period, while traffic and cooking related emissions were reduced by 25% and 50%, respectively. The low concentration during the control period was attributed to the lower production rate for secondary aerosols.
Plain Language Summary
At the beginning of 2020, a novel coronavirus disease (COVID‐19) was spreading in China and lasting through the following months. People's outdoor activities due to the coupling effect of this epidemic and the Chinese New Year holiday were greatly reduced and pollutant emissions related with these activities were also reduced during this period. This situation provides us a unique chance to look into the air quality and evaluate the corresponding mitigation measures in the city. We observed a significant drop of the mass concentration of NR‐PM1 by 50% in Lanzhou. The reduction of NR‐PM1 was mainly from secondary inorganic species accounting for 70% of reduced NR‐PM1. This finding is significantly different from that observed in Eastern China where the mass concentration of fine particulate matter was not reduced significantly with the reduction of primary emissions due to enhanced secondary production. In contrast, the production rates for secondary inorganic and organic aerosols showed a decreasing trend from before to during control period. These results revealed the large difference in air pollution chemistry between East and West China.
Key Points
The submicron aerosol mass concentration was reduced by 50% during COVID‐19 lockdown in Lanzhou
The reduction of aerosol was mainly due to a decline in secondary species; we identify an overall low production rate as the main driver
The result is contrast to those reported recently in East China where the reductions were offset by an increase in secondary species production
In this paper, a new method called sliding windows based on the extended convergent cross-mapping is proposed. Specifically, we add a dynamic perspective in causality analysis by implementing sliding ...window techniques. In addition, we show how sliding windows can clarify our understanding of the causal effects, which can be valuable in producing a more detailed and intuitive description of causal dynamics in real systems. Here, we use cross-mapping coefficient to quantify the causal relationship between time series. The main contribution of this paper is to introduce ECCM into economic and financial systems from a dynamic perspective, which effectively eliminates the impact of causal variability. As demonstrated in our model simulations, it can identify the dynamic evolution of coupling under different time delays, as well as detect the time-varying characteristics of coupling strength. Furthermore, we apply it to financial system to supplement and deepen the current understanding of time-varying causal relationships between Chinese and American stock markets.
Organic aerosols (OA) were studied in Fresno, California, in winter 2010 with an Aerodyne High Resolution Time‐of‐Flight Aerosol Mass Spectrometer (HR‐ToF‐AMS). OA dominated the submicron aerosol ...mass (average = 67%) with an average concentration of 7.9μg m−3 and a nominal formula of C1H1.59N0.014O0.27S0.00008, which corresponds to an average organic mass‐to‐carbon ratio of 1.50. Three primary OA (POA) factors and one oxygenated OA factor (OOA) representative of secondary OA (SOA) were identified via Positive Matrix Factorization of the high‐resolution mass spectra. The three POA factors, which include a traffic‐related hydrocarbon‐like OA (HOA), a cooking OA (COA), and a biomass burning OA (BBOA) released from residential heating, accounted for an average 57% of the OA mass and up to 80% between 6 – 9 P.M., during which enhanced emissions from evening rush hour traffic, dinner cooking, and residential wood burning were exacerbated by low mixed layer height. The mass‐based size distributions of the OA factors were estimated based on multilinear analysis of the size‐resolved mass spectra of organics. Both HOA and BBOA peaked at ∼140 nm in vacuum aerodynamic diameter (Dva) while OOA peaked at an accumulation mode of ∼460 nm. COA exhibited a unique size distribution with two size modes centering at ∼200 nm and 450 nm respectively. This study highlights the leading roles played by anthropogenic POA emissions, primarily from traffic, cooking and residential heating, in aerosol pollution in Fresno in wintertime.
Key Points
POA was emitted by three main sources: traffic, cooking, and residential heating
POA dominated aerosol composition, especially in ultrafine particles
SOA elevated at night, likely influenced by aqueous‐phase processing
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