Particulate pollution in an underground car park in Wuhan,China

Particulate matter（PM） pollution in an underground car park in Wuhan was investigated.Mass concentrations of PM₁₀ and PM_2.5 were obtained using gravimetric method.Selected metal elements,such as Fe,Mn,Zn,Pb,and Cu in PM₁₀ samples,were determined using atomic absorption spectrometer（AAS）. Beta attenuation method was applied to observe the hourly variation of PM₁₀ levels.Results show that average PM₁₀ concentrations at the entrance and at the exit were 101.3μg/m³ and 234.4μg/m³,respectively, and average PM_2.5 concentrations at the entrance and at the exit were 47.7μg/m³ and 62.7μg/m³, respectively.PM pollution was worse at the exit than at the entrance.Hourly PM₁₀ concentration was weakly correlated with traffic flow.Regarding element concentrations,the most enriched element in PM₁₀ samples was Fe.Re-suspension of soil dust at the exit is an important source of PM₁₀.     

Transmission dynamics of COVID-19 in Wuhan,China: effects of lockdown and medical resources

Nonlinear Dynamics - Due to the strong infectivity of COVID-19, it spread all over the world in about three months and thus has been studied from different aspects including its source of...     

Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu,China

Daily fine particulate (PM_2.5) samples were collected in Chengdu from April 2009 to February 2010 to investigate their chemical profiles during dust storms (DSs) and several types of pollution events, including haze (HDs), biomass burning (BBs), and fireworks displays (FDs). The highest PM_2.5 mass concentrations were found during DSs (283.3 μg/m³), followed by FDs (212.7 μg/m³), HDs (187.3 μg/m³), and BBs (130.1 μg/m³). The concentrations of most elements were elevated during DSs and pollution events, except for BBs. Secondary inorganic ions (NO₃^?, SO₄^2?, and NH₄⁺) were enriched during HDs, while PM_2.5 from BBs showed high K⁺ but low SO₄^2?. FDs caused increases in K⁺ and enrichment in SO₄^2?. Ca²⁺ was abundant in DS samples. Ion-balance calculations indicated that PM_2.5 from HDs and FDs was more acidic than on normal days, but DS and BB particles were alkaline. The highest organic carbon (OC) concentration was 26.1 μg/m³ during FDs, followed by BBs (23.6 μg/m³), HDs (19.6 μg/m³), and DSs (18.8 μg/m³). In contrast, elemental carbon (EC) concentration was more abundant during HDs (10.6 μg/m³) and FDs (9.5 μg/m³) than during BBs (6.2 μg/m³) and DSs (6.0 μg/m³). The highest OC/EC ratios were obtained during BBs, with the lowest during HDs. SO₄^2?/K⁺ and TCA/SO₄^2? ratios proved to be effective indicators for differentiating pollution events. Mass balance showed that organic matter, SO₄^2?, and NO₃^? were the dominant chemical components during pollution events, while soil dust was dominant during DSs.     

Impact of meteorological conditions on a nine-day particulate matter pollution event observed in December 2013,Shanghai,China

A severe particulate matter pollution event occurred in Shanghai from 1 to 9 December 2013.The mean hourly mass concentrations of PM_2.5 and PM₁₀ were 211.9 and 249.0 μg/m³,respectively.Reanalysis data,in situ,and remote-sensing measurements were used to examine the impacts of meteorological conditions on this event.It was found that the synoptic pattern of weak pressure,the reduced planetary boundary layer height,and the passage of two cold fronts were key factors causing the event.Four stages were identified during this event based on the evolution of its PM_2.5 levels and weather conditions.The highest concentration of PM2.5（602 μg/m³） was observed in stage 3.High PM2.5 concentrations were closely associated with a low local ventilation index,with an average of 505m²/s,as well as with the influx of pollutants from upstream,transported by the cold fronts.     

Impact of meteorological conditions on a nine-day particulate matter pollution event observed in December 2013, Shanghai,China

A severe particulate matter pollution event occurred in Shanghai from 1 to 9 December 2013. The mean hourly mass concentrations of PM_2.5 and PM₁₀ were 211.9 and 249.0 μg/m³, respectively. Reanalysis data, in situ, and remote-sensing measurements were used to examine the impacts of meteorological conditions on this event. It was found that the synoptic pattern of weak pressure, the reduced planetary boundary layer height, and the passage of two cold fronts were key factors causing the event. Four stages were identified during this event based on the evolution of its PM_2.5 levels and weather conditions. The highest concentration of PM_2.5 (602 μg/m³) was observed in stage 3. High PM_2.5 concentrations were closely associated with a low local ventilation index, with an average of 505 m²/s, as well as with the influx of pollutants from upstream, transported by the cold fronts.     

Vibration of an underground pipe in a field of a plane harmonic wave

Moscow. Institute of Irrigation. Translated from Prikladnaya Mekhanika, Vol. 24, No. 5, pp. 38–43, May, 1988     

Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu,China

Daily fine particulate(PM_2.5) samples were collected in Chengdu from April 2009 to February 2010 to investigate their chemical profiles during dust storms（DSs） and several types of pollution events, including haze（HDs）,biomass burning（BBs）,and fireworks displays（FDs）.The highest PM_2.5 mass concentrations were found during DSs（283.3μg/m³）,followed by FDs（212.7μg/m³）,HDs（187.3μg/m³）,and BBs（130.1μg/m³）.The concentrations of most elements were elevated during DSs and pollution events, except for BBs.Secondary inorganic ions(NO₃^-,SO₄^2-,and NH₄⁺) were enriched during HDs,while PM_2.5 from BBs showed high K⁺ but low SO₄^2-.FDs caused increases in K⁺ and enrichment in SO₄^2-.Ca²⁺ was abundant in DS samples.Ion-balance calculations indicated that PM_2.5 from HDs and FDs was more acidic than on normal days,but DS and BB particles were alkaline.The highest organic carbon（OC） concentration was 26.1μg/m³ during FDs,followed by BBs（23.6μg/m³）,HDs（19.6μg/m³）,and DSs（18.8μg/m³）. In contrast,elemental carbon（EC） concentration was more abundant during HDs（10.6μg/m³） and FDs （9.5μg/m³） than during BBs（6.2μg/m³） and DSs（6.0μg/m³）.The highest OC/EC ratios were obtained during BBs,with the lowest during HDs.SO₄^2-/K⁺ and TCA/SO₄^2- ratios proved to be effective indicators for differentiating pollution events.Mass balance showed that organic matter,SO₄^2-,and NO₃^- were the dominant chemical components during pollution events,while soil dust was dominant during DSs.     

Erratum to Aerosol pollution in China: Present and future impact on environment

PARTICUOLOGY regrets that the above paper was mistakenly classified as a ‘Review’ rather than an ‘Invited paper’ when originally published in volume 7, issue 6, 426–431.     

Analysis of the causes of heavy aerosol pollution in Beijing,China:A case study with the WRF-Chem model

The causes and variability of a heavy haze episode in the Beijing region was analyzed.During the episode,the PM2.5 concentration reached a peak value of 450 μg/kg on January 18,2013 and rapidly decreased to100 μg/kg on January 19,2013,characterizing a large variability in a very short period.This strong variability provides a good opportunity to study the causes of the haze formation.The in situ measurements(including surface meteorological data and vertical structures of the winds,temperature,humidity,and planetary boundary layer(PBL)) together with a chemical/dynamical regional model(WRF-Chem) were used for the analysis.In order to understand the rapid variability of the PM2.5 concentration in the episode,the correlation between the measured meteorological data(including wind speed,PBL height,relative humidity,etc.) and the measured particle concentration(PM2.5 concentration) was studied.In addition,two sensitive model experiments were performed to study the effect of individual contribution from local emissions and regional surrounding emissions to the heavy haze formation.The results suggest that there were two major meteorological factors in controlling the variability of the PM2.5 concentration,namely,surface wind speed and PBL height.During high wind periods,the horizontal transport of aerosol particles played an important role,and the heavy haze was formed when the wind speeds were very weak(less than 1 m/s).Under weak wind conditions,the horizontal transport of aerosol particles was also weak,and the vertical mixing of aerosol particles played an important role.As a result,the PBL height was a major factor in controlling the variability of the PM_(2.5) concentration.Under the shallow PBL height,aerosol particles were strongly confined near the surface,producing a high surface PM_(2.5) concentration.The sensitivity model study suggests that the local emissions(emissions from the Beijing region only)were the major cause for the heavy haze events.With only local emissions,the calculated peak value of the PM_(2.5) concentration was 350 μg/kg,which accounted for 78%of the measured peak value(450 μg/kg).In contrast,without the local emissions,the calculated peak value of the PM_(2.5) concentration was only100 μg/kg,which accounted for 22%of the measured peak value.     

Analysis of the causes of heavy aerosol pollution in Beijing,China: A case study with the WRF-Chem model

The causes and variability of a heavy haze episode in the Beijing region was analyzed. During the episode, the PM_2.5 concentration reached a peak value of 450 μg/kg on January 18, 2013 and rapidly decreased to 100 μg/kg on January 19, 2013, characterizing a large variability in a very short period. This strong variability provides a good opportunity to study the causes of the haze formation. The in situ measurements (including surface meteorological data and vertical structures of the winds, temperature, humidity, and planetary boundary layer (PBL)) together with a chemical/dynamical regional model (WRF-Chem) were used for the analysis. In order to understand the rapid variability of the PM_2.5 concentration in the episode, the correlation between the measured meteorological data (including wind speed, PBL height, relative humidity, etc.) and the measured particle concentration (PM_2.5 concentration) was studied. In addition, two sensitive model experiments were performed to study the effect of individual contribution from local emissions and regional surrounding emissions to the heavy haze formation. The results suggest that there were two major meteorological factors in controlling the variability of the PM_2.5 concentration, namely, surface wind speed and PBL height. During high wind periods, the horizontal transport of aerosol particles played an important role, and the heavy haze was formed when the wind speeds were very weak (less than 1 m/s). Under weak wind conditions, the horizontal transport of aerosol particles was also weak, and the vertical mixing of aerosol particles played an important role. As a result, the PBL height was a major factor in controlling the variability of the PM_2.5 concentration. Under the shallow PBL height, aerosol particles were strongly confined near the surface, producing a high surface PM_2.5 concentration. The sensitivity model study suggests that the local emissions (emissions from the Beijing region only) were the major cause for the heavy haze events. With only local emissions, the calculated peak value of the PM_2.5 concentration was 350 μg/kg, which accounted for 78% of the measured peak value (450 μg/kg). In contrast, without the local emissions, the calculated peak value of the PM_2.5 concentration was only 100 μg/kg, which accounted for 22% of the measured peak value.