Estimation of PM10 in the traffic-related atmosphere for three road types in Beijing and Guangzhou, China

Optimization of Emission Reduction Target in the Beijing-Tianjin-Hebei Region: An Atmospheric Transfer Coefficient Matrix Perspective

In recent years, the problem of atmospheric pollution has been concerning in the Beijing-Tianjin-Hebei region, due to the frequent haze. It has become a significant issue to improve regional air quality through appropriate emission reduction measures. In this study, considering the regional atmospheric transmission of air pollutants, the WRF/CALPUFF model (the Weather Research and Forecasting model coupled with the California Puff air quality model) was used to describe the impact of each city's pollutant emissions on the concentrations of every city. Then, a new optimization model was designed to calculate the maximum allowable emissions of every city. The results showed that NOx and PM_2.5 emissions need to be reduced by 44% and 48%, respectively, in the traditional mitigation scenario (any city's pollutant emissions are not allowed to increase). However, in the optimized scenario, NOx and PM_2.5 emissions should be reduced by 23% and 46%, respectively, to meet the national secondary standard. The emissions of cities with low transfer coefficients, such as Zhangjiakou, Qinhuangdao, and Chengde, could even be appropriately increased. This means that the optimized scenario could reduce the pressure on emission reduction. Although the optimization results are theoretical and idealistic, this research study provides a new idea for formulating emission mitigation policies in various regions to reduce the impact on the economy.

Assessment of different methods in analyzing motor vehicle emission factors

To explore the emission characteristics of vehicle's pollutants is of great significance to prevent and control the diffusion of pollutants. Limited by geographic location and economic condition, the model- and guideline-based studies on vehicle's emission factor have become more concerned measures than the actual measurement. By analyzing the actual operating conditions of motor vehicles, this study obtains the emission factors of typical pollutants from different motor vehicles by adopting international vehicle emission (IVE) model and guideline method, respectively. Furthermore, the resulting emission factors by the above methods were compared and analyzed with on-road method. The results show that: (1) the emission factors of vehicle pollutants change regularly with velocity, emission standard, and accumulated mileage. Taking CO as an example, its emission factor shows a downward trend with the increase of velocity and emission standard and an upward trend with the increase of accumulated mileage; (2) compared with the actual measurement, the vehicle emission factor obtained by the guideline method has a large error, while the IVE model is close to the actual.

Source apportionment and health risk assessment for potentially toxic elements in size-fractionated road dust in Busan Metropolitan City, Korea

Potentially toxic elements' (PTEs; V, Cr, Co, Ni, Cu, Zn, As, Cd, Sb, Pb, and Hg) pollution level was investigated in size-fractionated road dust in Busan Metropolitan City. Health risks to humans (adult and children) were also evaluated in fine particle fraction (< 63 μm) of road dust. PTE concentrations in the fine particles (< 63 μm) were ranked as follows (unit: mg/kg): Zn (2511) > Cu (559) > Cr (531) > Pb (385) > Ni (139) > V (83.8) > Sb (31.6) > Co (21.6) > As (17.2) > Cd (4.1) > Hg (0.38). The PTE concentrations in fine particles (< 63 μm) were significantly higher than those in coarse particles except for V, Co, and As. The mean PTE loadings of fine particle fraction (< 63 μm; 233 mg/m2) in road dust were up to 4.5 times higher than other particle fractions. Igeo values of Sb were higher than 5 except for > 1000-μm fraction, indicating extremely polluted status. PCA results and elemental ratios indicated that most of the PTEs in road dust were derived from non-exhaust traffic-related sources such as brake pads and tires. Cr, Pb, and Sb had higher HI values than other metals for both adults and children. Sampling sites of heavy traffic and industrial areas showed that the carcinogenic risk exceeded the maximum threshold level (10 - 4). Especially in children, the mean carcinogenic risk (ingestion pathway) of As (6.8 × 10 - 4) Cd (2.0 × 10 - 4), and Ni (4.1 × 10 - 4) exceeded the maximum threshold level, indicating that continuous exposure to road dust may pose a high cancer risk to children. Therefore, continuous monitoring and management of these metals are needed to protect human health and the urban environment.

A complex network approach for the model of vehicle emission propagation and intelligently mine the interaction rules

With the increasing number of motor vehicles, exhaust emission has become a major source of urban pollution. Most studies are limited to the prediction of pollutant concentration, which cannot clearly indicate the change of pollution emissions and regional relationship. In this paper, we propose an emission propagation model of vehicle source pollution based on complex network in order to intelligently mine the interaction and propagation rules hidden behind dynamic spatiotemporal data. First, aiming at the problems of low resolution and insufficient data volume of vehicle emission data, a high-resolution pollution emission data is generated based on the COPERT (Computer Program to Calculate Emissions from Road Transport). For study the influence of causality between regions, a propagation model is designed based on the convergent cross mapping method to transform the emission time series into a complex network. In addition, we propose a novel key node mining algorithm using hybrid local and global information to identify areas of heavy pollution. Experimental results on real datasets demonstrate that the spread of pollution follows certain rules and is also affected by regional influences. Moreover, the proposed algorithm is superior to the state-of-the-art methods.

Fine road dust contamination in a mining area presents a likely air pollution hotspot and threat to human health

The road dust found in mining areas is composed of dust from multiple sources, including wind transported mineral dust from mines and tailings as well as uncovered trucks leakage. Collectively, these are then distributed via wind and traffic activity, becoming an important source of particulate matter (PM) and subsequently inhaled by pedestrians. A common practice in previous road dust risk assessments has regarded them as soil, which likely led to a significant underestimation of the actual inhaled amount. To more accurately understand the inhalation risk presented by road dust in mining areas, the study applied a detailed pollution analysis and dust dispersion model to assess the inhaled amount of road dust. Road dust samples located at different distances to the mine and tailings were collected and sieved to 10 μm (RD10). Enrichment factors (EFs) of Ce, As, Cd, and Mo exceeded 20 across most sampled sites, suggesting extreme pollution. Source analysis indicated that most of the collected RD10 had greater than half of its mass originating from the mine. To assess the risk presented by inhalation exposure to local populations, we built a method using Gaussian diffusion model and two exposure scenarios for both adults and children were considered. The level of simulated particle concentrations was comparable to that described in the literature; the inhalation of potential toxic elements (PTEs) in RD10 led to health risks for both adults and children (adult and child HI > 1, with adults CR in industrial areas >10^-4). Results also indicated that a ten-fold reduction of silt load resulted in a >4-fold decrease in risk. Collectively, the results suggest that fine road dust is a potential hotspot for mineral exposure in populations living around a mine and its tailings; moreover, that effective prevention measures like road cleaning and truck regulation are urgently needed.

Physicochemical characterization and sources of the thoracic fraction of road dust in a Latin American megacity

Road dust has been identified as one of the main sources of outdoor PM₁₀ in Bogota (a Latin American megacity), but there are no studies that have analyzed the physicochemical characteristics and origins of its respirable fraction. A characterization of inorganic compounds (water soluble ions, major and trace elements, organic and elemental carbon) and an analysis of source contributions to the PM₁₀ fraction of road dust were carried out in this study. A total of twenty road dust samples, selected from representative industrial, residential and commercial areas, were swept and resuspended to obtain the thoracic fraction. Size distribution by laser diffraction and individual particle morphology by Scanning Electron Microscopy were also evaluated. The data obtained revealed that the volume (%) of thoracic particles was higher in samples from industrial zones where heavy vehicular traffic, industrial emissions and deteriorated pavements predominated. Crustal elements were the most abundant species, accounting for 49-62% of the thoracic mass, followed by OC (13-29%), water-soluble ions (1.4-3.8%), EC (0.8-1.9%) and trace elements (0.2-0.5%). The Coefficient of Divergence was obtained to identify the spatial variability of the samples. A source apportionment analysis was carried out considering the variability of chemical profiles, enrichment factors and ratios of Fe/Al, K/Al, Ca/Al, Ti/Al, Cu/Sb, Zn/Sb, OC/TC and OC/EC. By means of a PCA analysis, five components were identified, including local soils and pavement erosion (63%), construction and demolition activities (13%), industrial emissions (6%), brake wear (5%) and tailpipe emissions (4%). These components accounted for 91% of the total variance. The results provide data to understand better one of the main sources of PM₁₀ emissions in Bogota, such as road dust. These data will be useful to optimize environmental policies, and they may be used in future studies of human health and air quality modeling.

Trace Elements and Polycyclic Aromatic Hydrocarbons Variation Along the Guang-Shen Expressway Before and After the 2016 Qingming Festival in Guangzhou

PM_2.5 samples (particles with aerodynamic diameter < 2.5 μm) were collected along the Guang-Shen expressway around the Qingming Festival, one of the most congested periods in China, which started from April 2-4, in 2016. Twenty-five trace elements and 16 priority polycyclic aromatic hydrocarbons (PAHs) of the samples were analyzed. Their major sources at different periods were identified. The concentrations of PAHs distinctly increased with growing traffic flow 2 days before the Qingming Festival (March 31th and April 1st), decreased gradually on the first 2 days of the 3-day festival (April 2nd and 3rd) and rose again on the last day (April 4th). The proportion changing of higher molecular weight containing 5- and 6-ring PAHs (HMW PAHs) closely related to the traffic flow variation were consistent with the concentration variation of PAHs during the experimental period. Indicators of gasoline/diesel engines emission, i.e., Mo, Co, Mn, and Pb showed similar concentration variation with PAHs. The concentrations of trace elements, mainly derived from wear instead of combustion process, such as Cu, Zn, Ti, and Sb, raised significantly during the rainy days. Incremental lifetime cancer risk (ILCR) values were calculated to evaluate the health risk caused by PAH around the Qingming Festival. The ILCR values increased by 3-10 times 2 days before and on the last day of the festival comparing with other days, as a result of traffic related sources, including engine emission and wearing of tires. It concluded by recommending the necessity of traffic diversion to alleviate the health risk to drivers and nearby residents during important festivals.

Effects of dissolved low molecular weight organic acids on oxidation of ferrous iron by Acidithiobacillus ferrooxidans

A few researchers have reported on work concerning bioleaching of heavy-metal-contaminated soil using Acidithiobacillus ferrooxidans, since this acidophile is sensitive to dissolved low molecular weight (LMW) organic acids. Iron oxidation by A. ferrooxidans R2 as well as growth on ferrous iron was inhibited by a variety of dissolved LMW organic acids. Growth experiments with ferrous iron as an oxidant showed that the inhibition capability sequence was formic acid>acetic acid>propionic acid>oxalic acid>malic acid>citric acid. The concentrations that R2 might tolerate were formic acid 0.1mmolL(-1) (2mmolkg(-1)soil), acetic and propionic acids 0.4mmolL(-1) (8mmolkg(-1)soil), oxalic acid 2.0mmolL(-1) (40mmolkg(-1)soil), malic acid 20mmolL(-1) (400mmolkg(-1)soil), citric acid 40mmolL(-1) (800mmolkg(-1)soil), respectively. Although R2 was sensitive to organic acids, the concentrations of LMW organic acids in the contaminated soils were rather lower than the tolerable levels. Hence, it is feasible that R2 might be used for bioleaching of soils contaminated with metals or metals coupled with organic compounds because of the higher concentrations of LMW organic acids to which R2 is tolerant.