Impact of Traffic Emissions on Local Air Quality and the Potential Toxicity of Traffic-related Particulates in Beijing, China

Objective Air-borne particulates from different sources could have different physicochemical properties and inflammatory potentials. This study aims to characterize the chemical compositions and the toxicity of ambient particulate matter （PM） associated with traffic emissions. Methods The concentrations of trace elements, organic carbon （OC）, elemental carbon （EC） and polycyclic aromatic hydrocarbons （PAHs） in PM2.5 and PMlo were measured in samples collected at sites in Beijing, China. Their toxic effects on the pulmonary system of rats were investigated. Biochemical parameters （LDH, T-AOC, TP） and inflammatory cytokine（IL-6, IL-1, TNF-a） levels were measured in the lungs of rats exposed to traffic-related PM. Oxidative damage was observed. PM samples were taken from a near road site and an off road site in summer time in 2006. Results The concentrations of the USEPA priority pollutant PAHs in both PMlo and PM2.s were higher （299.658 and 348.412） at the near road site than those （237.728 and 268.472） at the off road site. The similar trend was observed for the concentrations of trace elements in PM. Compared to coarse particles （PM^0）, fine particles （PM2.s） have a greater adsorption capacity to enrich toxic elements than inhalable particles. Decrease in antioxidant capacity and an increase in the amount of lipid peroxidation products in rat lung tissues was observed. Conclusion The findings of the present study suggest that the differing inflammatory responses of PM collected from the two road sites might have been mediated by the differing physicochemical characteristics.

Health Risk Assessment of Mobility-Related Air Pollution in Ha Noi, Vietnam

Hanoi is the capital city of Vietnam and the second largest city of the country, just behind Ho Chi Minh City. During the last two decades, Hanoi developed fast and expanded steadily. Since the city acquired large parts of the surrounding provinces in 2008, Hanoi tripled its size and doubled its population. The new development aims to spread the concentrated population and economic activities to alleviate the stress caused by pollution and the decreasing quality of life of the residents. Hanoi has a very fast growing fleet of motor vehicles, at the rate of 12% - 15% annually. The fast transition from bikes to motorcycles and to cars results in a most serious environmental burden in particular on the air quality and human health. This paper overviews the air quality and pollution caused by road traffic in central Hanoi (5 old districts) and the related health outcomes due to particulate matters (PM10 and PM2.5). It uses dose-response functions to quantify the number of extra deaths resulting from traffic-related particulate matters. The results are compared with those of other studies to assess the impacts of air pollution on human health in large, crowded and fast developing cities in Southeast Asia. Assessment of the health risk caused by traffic shows that mobility in Hanoi causes a high health burden. In 2009, mobility caused 3200 extra deaths by traffic related PM10. The result shows that health impacts due to air pollution are by far larger than the number of fatalities due to traffic accidents.

Sources appointment and health risks of PM_(2.5)-bound trace elements in a coastal city of southeastern China

To gain a comprehensive understanding of sources and health risks of trace elements in an area of China with high population densities and low PM_(2.5)concentrations,15 trace elements(Al,K,Ca,Ti,V,Cr,Mn,Fe,Ni,Cu,Zn,As,Sn,Ba,Pb)in PM_(2.5)were monitored from December 2020 to November 2021 in a representative city,Xiamen.The concentrations of trace elements in Xiamen displayed an obvious seasonal variation and were dominated by K,Fe,Al,Ca and Zn.Based on Positive Matrix Factorization analysis,source appointment revealed that the major sources of trace elements in Xiamen were traffic,dust,biomass and firework combustion,industrial manufacture and shipping emission.According to health risk assessment combined with the source appointment results,it indicated that the average noncarcinogenic risk was below the threshold and cancer risk of four hazardous metals(Cr,Ni,As,Pb)exceeded the threshold(10^(-6)).Traffic-related source had almost half amount of contribution to the health risk induced by PM_(2.5)-bound trace elements.During the dust transport period or Spring Festival period,the health risks exceeded an acceptable threshold even an order of magnitude higher,suggesting that the serious health risks still existed in low PM_(2.5)environment at certain times.Health risk assessment reminded that the health risk reduction in PM_(2.5)at southeastern China should prioritize traffic-related hazardous trace elements and highlighted the importance of controlling vehicles emissions in the future.

Insight study of rare earth elements in PM_(2.5)during five years in a Chinese inland city:Composition

The booming development of rare earth industry and the extensive utilization of its products accompanied by urban development have led to the accelerated accumulation of rare earth elements(REEs)as emerging pollutants in atmospheric environment.In this study,the variation of REEs in PM_(2.5)with urban(a non-mining city)transformation was investigated through five consecutive years of sample collection.The compositional variability and provenance contribution of REEs in PM_(2.5)were characterized,and the REEs exposure risks of children and adults via inhalation,ingestion and dermal absorption were also evaluated.The results showed an increase in the total REEs concentration from 46.46±35.16 mg/kg(2017)to 81.22±38.98 mg/kg(2021)over the five-year period,with Ce and La making the largest contribution.The actual increment of industrial and traffic emission source among the three pollution sources was 1.34 ng/m^(3).Coal combustion source displayed a downward trend.Ingestion was the main exposure pathway for REEs in PM_(2.5)for both children and adults.Ce contributed the most to the total intake of REEs in PM_(2.5)among the population,followed by La and Nd.The exposure risks of REEs in PM_(2.5)in the region were relatively low,but the trend of change was of great concern.It was strongly recommended to strengthen the concern about traffic-related non-exhaust emissions of particulate matter.

Investigation of the spatiotemporal variation and influencing factors on fine particulate matter and carbon monoxide concentrations near a road intersection

The minute-scale variations of fine particulate matter （PM2.5） and carbon monoxide （CO） concentrations near a road intersection in Shanghai, China were investigated to identify the influencing factors at three traffic periods. Measurement results demonstrate a synchronous variation of pollutant concentrations at the roadside and setbacks, and the average concentration of PM2.5 at the roadside is 7% （44% for CO） higher than that ofsethacks within 500 m of the intersection. The pollution level at traffic peak periods is found to be higher than that of off-peak periods, and the morning peak period is found to be the most polluted due to a large amount of diesel vehicles and unfavorable dispersion conditions. Partial least square regressions were constructed for influencing factors and setback pollutant concentrations, and results indicate that meteorological factors are the most significant, followed by setback distance from the intersection and traffic factors. CO is found to be sensitive to distance from the traffic source and vehicle type, and highly dependent on local traffic conditions, whereas PM2.5 originates more from other sources and background levels. These findings demonstrate the importance of localized factors in understanding spatiotemporal patterns of air pollution at intersections, and support decision makers in roadside pollution management and control.

On the effects of urban-like intersections on ventilation and pollutant dispersion

Focusing on the effect of street morphology on the ventilation efficiency,this paper presents 3D computational fluid dynamics(CFD)simulations of airflow and pollutant dispersion within urban-like three-way intersections,four-way intersections and roundabouts.The steady-state Reynolds-averaged Navier-Stokes(RANS)k-εturbulence model is adopted and eight directions of the approaching wind are considered.The ventilation efficiency is evaluated using the ventilation indices purging flow rate(PFR)and the net escape velocity(NEV).Results show the sensitivity of the ventilation efficiency to the type of intersection,to the wind direction and to the number of branches.Specifically,the ventilation efficiency of the investigated three-way intersections is found to be better than that of the other intersections,especially when the angle between the streets is large,while that of roundabouts is also considerable,even with a similar average wind velocity,among the cases evaluated in this paper.Further,the influence of the wind direction for the three-way and four-way intersections is greater than that on roundabouts.Studies on the ventilation efficiency at urban intersections are not common in the literature and this work may help urban planners to better design such hub nodes of urban traffic,where traffic-related pollutants are not easily dispersed,thus avoiding harm to the health of pedestrians and surrounding residents.