Observed PM10 Concentrations Research Articles

Modeling Particulate Matter Concentrations in Makkah, Applying a Statistical Modeling Approach

Particulate matter originates from a variety of sources in Makkah, Saudi Arabia. Since Makkah is situated in an arid region and is a very busy city due to its religious importance in the Muslim world, PM10 concentrations here exceed the international and national air quality standards set for the protection of human health. The main aim of this paper is to model PM10 concentrations with the aid of meteorological variables (wind speed, wind direction, temperature, and relative humidity) and traffic related air pollutant concentrations (carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), sulphur dioxide (SO2) and lag_PM10 concentrations), which are measured at the same location near Al-Haram (the Holy Mosque) in Makkah. A Generalized Additive Model was developed for predicting hourly PM10 concentrations. Predicted and observed PM10 concentrations are compared, and several metrics, including the coefficients of determination (R2 = 0.52), Root Mean Square Error (RMSE = 84), Fractional Bias (FB = –0.22) and Factor of 2 (FAC2 = 0.88), are calculated to assess the performance of the model. The results of these, along with a graphical comparison of the predicted and observed concentrations, show that model is able to perform well. While effects of all the covariates were significant (p-value ＜ 0.01), the meteorological variables, such as temperature and wind speed, seem to be the major controlling factors with regard to PM10 concentrations. Traffic related air pollutants showed a weak association with PM10 concentrations, suggesting road traffic is not the major source of these. No modeling study has been published with regards to air pollution in Makkah and thus this is the first work of this kind. Further work is required to characterize road traffic flow, speed and composition and quantify the contribution of each source, which is part of the ongoing project for managing the air quality in Makkah.

A numerical study of the effect of frozen soil on dust emission during an East Asian dust event in December 2009

There are few dust simulation studies for East Asian dust events that took place in the wintertime, when the surface conditions of the dust source region differ from those of the springtime. The soil water turns into ice when the temperature falls below freezing, and the ice might prohibit wind erosion by increasing the binding strength between soil particles. However, the contribution of frozen soil to reducing dust outbreaks remains unclear. This study investigates the effect of frozen soil on dust emission through a case study of a severe wintertime East Asian dust event that originated on 23 and 24 December 2009 in Southern Mongolia and Inner Mongolia and reached Korea on 25 and 26 December 2009 using WRF/Chem with a new dust emission scheme. Model simulations with and without the effect of frozen soil were conducted. A temperature below 0°C and relative soil saturation exceeding 40% were used for frozen soil criteria, and the frozen soil was prohibited from emitting dust. The dust concentrations derived from the simulation without the effect of frozen soil were about three times higher than the observed PM10 concentrations, while the results from the simulation with the frozen-soil effect were quite similar to those of the observation data. The simulation of the wintertime East Asian dust event with the frozen-soil effect improved the model representation. The sensitivity tests for frozen soil indicate that the criteria of frozen soil used in this study are appropriate for this case study.

A new approach for determination of crustal and trace elements in airborne particulate matter

An ICP-OES procedure was developed for fast and accurate determination of various crustal (Al, Ca, Fe, Mg, Si) and trace elements (Ba, Cu, Mn, Na, K, Sr, Ti, Zn) in airborne particulate matter. The method is based on a preliminary treatment of the aerosol samples with a mixture of nitric acid and hydrogen peroxide at elevated temperature leading to a mineralization of the organic sampling substrate, dissolution of soluble material and homogeneous suspension of the remaining non-soluble fraction. After dilution the derived slurry solutions were measured using ICP-OES. The reproducibility of analysis given as the relative standard deviation (% RSD) varied between 3.2 and 6.8% for bulk constituents such as Al, Ca, Fe, Mg and Si whereas values ranging from 3.5 to 9.1% were obtained for trace metals present with distinctly lower abundance in PM10 (e.g. Ba, Cu, Mn, Sr, Zn). The limits of detection (LOD) calculated as three times the standard deviation (3σ) of the signal derived from filter blank samples ranged from approximately 1 ng m−3 (Sr) to 71 ng m−3(Ca). The developed procedure was evaluated by comparing the obtained results with the findings derived for the same set of aerosol samples analyzed using a microwave procedure for sample dissolution with subsequent ICP-OES analysis. Finally the developed procedure was applied for the analysis of crustal and trace elements in PM10 samples collected at an urban site (Getreidemarkt, Vienna) and a rural site (Hartberg, Styria), in Austria. The concentrations of the investigated crustal elements varied between some hundred ng m−3 and few µg m−3 with highest concentrations for Fe and Si, distinctly reduced concentrations ranging from some ng m−3 (Sr) to more than hundred ng m−3 (K) were found for trace elements. Observed PM10 concentrations were found to be in accordance to literature findings from urban sites in central Europe.

Impact of the extreme meteorological conditions during the summer 2003 in Europe on particulate matter concentrations

Due to the strong relation between meteorology and air quality, a changing climate is anticipated to significantly impact air pollution. To investigate this effect a synoptic situation in the past which is expected to occur more often in future is analyzed in terms of air quality. In this study the effect of the meteorological conditions in the extreme summer 2003 on the concentration of PM10 and its components is investigated over Europe. To this end measurements of the EMEP network in Europe of the summer 2003 were compared to the average of the summers of a five years period (2003–2007). Furthermore simulation runs were performed with the German chemistry transport model REM-Calgrid and the Dutch model LOTOS-EUROS, to analyze whether state-of-the-art chemistry transport models are able to reproduce the observed concentrations during this episode.The synoptic situation in summer 2003 resulted in 1–10 μg m−3 higher observed PM10 concentrations compared to the five years average. This increase was not reproduced to the same extent by the two models at most of the stations and the two models show evident differences in their PM10 simulations. The correlation between PM10 concentrations and meteorological parameters indicates that observed concentrations increase during weather conditions with high daily maximum temperature. The same holds for elemental carbon which is chosen as an example for a primary component. Low horizontal transport and the absence of wet deposition as a result of low wind speed and little precipitation associated with conditions with high temperatures favour the accumulation of pollutants in the lower troposphere. Although these conditions are reflected in the meteorological input data of the chemistry transport models used in this study, the models were not able to reproduce this relationship; they underestimate the observed high concentrations. This indicates that the underestimation of the variability of PM with meteorology is due to missing but important components and associated emissions or uncertainties therein, e.g. mineral dust, secondary organic aerosols and wild fires. To improve the simulation performance of the chemistry transport models as function of meteorological conditions these emission sources and the formation of secondary organic aerosols have to be included or improved and the dependency of anthropogenic emissions on meteorological conditions should be explicitly taken into account. These are essential issues for the simulation of such extreme conditions.

Seasonal Characteristics of Water-Soluble Dicarboxylates Associated with PM10 in the Urban Atmosphere of Durg City, India

PM10 samples were collected between July 2009 and June 2010 in the urban area of Durg City, India, and analyzed for water-soluble dicarboxylate species. Observed PM10 concentrations varied from 94.0 to 432.1 μg/m3 with an annual average of 253.5 μg/m3. The annual average concentration of PM10 was four times higher than the Indian Central Pollution Control Board (CPCB) National Ambient Air Quality Standard (Indian NAAQS) prescribed limit of 100 μg/m3. The high PM10 mass concentration in Durg City are attributed to anthropogenic activities, including a high rate of construction activities, biomass combustion and mechanical disturbance of road dusts. The highest PM10 value was recorded during the winter, a period characterized by extensive biomass burning, especially at night, while the lowest PM10 concentration was recorded during the monsoon, when there was significant precipitation. The highest concentrations of dicarboxylates were found during winter and spring. On average, total water-soluble dicarboxylates (966 ng/m3) accounted for 0.39% of the PM10 mass. Oxalate (C2), followed by malonate (C3) and succinate (C4), dominated the total mass of dicarboxylates, the sum of these three species accounting for 77.5% of the total analyzed. The malonate to succinate concentration ratio calculated in this study was higher than those reported for vehicular emissions, suggesting that in addition to vehicular exhausts, secondary formation of particulate dicarboxylates via photo-oxidation also occurred. Principal component analysis (Varimax Rotated Component Matrix) revealed that secondary aerosol formation, coal and biomass combustion, and vehicular emissions were the major sources contributing to overall PM10 mass in Durg City, India.

Integrated model for the estimation of annual, seasonal, and episode PM10 exposures of children in Rome, Italy

Population exposure assessment plays a central role in developing efficient policies to control the significant health impacts caused by ambient pollution. Policy development requires comparison of alternative control options, which by definition can only be conducted using models. The current work presents results from an integrated model developed for Rome, Italy, to estimate the exposure distributions of children. Spatial distribution of the hourly PM10 levels in 2005 was modeled by a chemical transport model and the modeled concentrations were adjusted using a procedure based on the observed PM10 concentrations at urban stations. The PM10 exposures of children were then estimated accounting for: the time–activity patterns in indoors, outdoors, and in traffic; adjusted ambient levels; and outdoor to indoor infiltration factors. The mean annual exposure level was 22 μg/m3, compared to the mean observed ambient concentration at a central station of 48 μg/m3, with higher seasonal levels estimated for spring and summer than for autumn and winter. The differences are caused by the longer time spent outdoors and higher residential ventilation rates during spring and summer. The highest integrated exposures took place in the northeasterly districts. Average exposure levels in almost the whole city exceeded 20 μg/m3. Short-term exposures were also investigated during a winter PM10 episode for which exposure levels in excess of 30 μg/m3 were calculated. Cumulative distribution results for the children indicate that the 24-h limit of 50 μg/m³ set for the protection of human health is not exceeded by the exposures of children during the episode. The results of this study are important for a correct interpretation of the epidemiological studies taking into account the relationship of exposures and ambient air quality and for the development of alternative policy options to reduce children’s exposures by lifestyle modification and interventions focused on the reduction of the infiltration of PM10 into indoor environments.

The Effects of Snow Cover and Soil Moisture on Asian Dust: I. A Numerical Sensitivity Study

Semi-arid regions of East Asian dust source areas are frequently covered by snow. We conducted a sensitivity study of East Asian dust storms to investigate the effects of snow cover and soil moisture with a global aerosol model (MASINGAR). The simulated dust concentration greatly underestimated the dust event in late March 2007 relative to the observed PM10 concentration. When the effect of soil moisture is not taken into consideration, the simulated total dust emission amount is almost doubled, and the simulated dust concentration is comparable or overestimated with regard to the PM10 observations. The result of the sensitivity study suggests that the underestimation of the dust event is due to excessive soil moisture, which suppresses the dust emission. In contrast, the simulated dust concentration of the control experiment is in agreement with the observed PM10 concentration in May, suggesting that the effects of snow cover and soil moisture on the dust event in May were very small. To improve our ability to forecast Asian dust events in March, the treatment of the hydrological cycles of snow in the land surface model and the soil moisture dependence of dust emission flux should be regarded as the key factors.

Comparison of Surface Observations and a Regional Dust Transport Model Assimilated with Lidar Network Data in Asian Dust Event of March 29 to April 2, 2007

Surface observation data taken in Mongolia, China, Korea and Japan during the Asian dust event of March 29 to April 2, 2007 were compared with a regional dust transport model assimilated with the lidar network data. The assimilated model reproduced the reported dust event in Mongolia and the observed PM10 concentrations in Korea and Japan very well. The mass/extinction conversion factor (MEF) obtained from the lidar dust extinction coefficient and PM10 concentration was also compared with the assimilated model for Seoul and Tsukuba where both the lidar and PM10 data were available. The MEFs for PM10 and PM2.5 (the ratio of dust-only PM10 or PM2.5 to the dust extinction coefficient) were calculated with the assimilated model. The modeled MEF for PM10 reproduced the observed MEF reasonably and exhibited spatial and temporal variations reflecting the variations in the dust particle size distribution. The modeled MEF for PM2.5 had much less variation. This indicates that the dust extinction coefficient has a higher correlation with dust PM2.5 and should be a useful index for studying the effect of dust on human health.

Annual simulation of secondary pollution over northern Italy

A secondary pollution modelling system for simulating airborne dispersion and chemical reactions is applied over a regional scale domain located in the North-West of Italy, where urban and industrial areas are present. It was found an overestimation of NO2 in the urban areas, probably due to an underestimation of the vertical diffusivity; the analysis of OX confirms that the discrepancies in O3 and NO2 are mainly due to local scale effects; the model shows a general underestimation of the observed PM10 concentrations due to the uncertainties in the emission inventories, spatial resolution, and the adopted aerosol modelling approach.

Comparison of predicted and observed PM10 concentrations in several urban street canyons

This paper presents an evaluation of a street canyon model (Operational Street Pollution Model) in several urban streets having different configurations. The model was performed for the prediction of particulate matter (PM10) concentrations from exhaust emissions of mobile sources in five street canyons in the city of Izmir, Turkey. Hourly concentrations of PM10 were observed at the streets and the relevant hourly meteorological parameters were measured at the roof level. The hourly street level measurements by a mobile ambient air quality monitoring station and on-site automatic traffic counts were conducted for 1 week in each street during the period of November 2007 and March 2008. The urban background concentrations were also obtained from four stationary air quality monitoring stations in the city during the measurement campaigns and they were included in the modeling studies as the contribution of background air quality. Finally, statistical analyses were carried out to evaluate the model performance by comparing the predicted and observed time series of PM10 concentrations using a correlation coefficient and an index of agreement (IA). The IA varied from 0.87 to 0.98 at the symmetric canyons and the correlation coefficient ranged from 0.68 to 0.92, indicating modeling performances ranging from acceptable to very good. The similar values were calculated between 0.74 and 0.76 for IA and between 0.34 and 0.41 for correlation coefficient at the asymmetric canyons. The best agreement between predicted and observed PM10 concentrations (IA = 0.98, R2 = 0.92) was found for Cumhuriyet Avenue in this study. These values are found as the best agreement in overall studies in literature.

The Asian Dust Aerosol Model 2 (ADAM2) with the use of Normalized Difference Vegetation Index (NDVI) obtained from the Spot4/vegetation data

The operational Asian Dust Aerosol Model (ADAM)1 in Korea Meteorological Administration has been modified to the ADAM2 model to be used as an operational forecasting model all year round not only in Korea but also in the whole Asian domain (70-160°E and 5-60°N) using the routinely available World Meteorological Organization (WMO) surface reporting data and the Spot/vegetation Normalized Difference Vegetation Index (NDVI) data for the period of 9 years from 1998 to 2006. The 3-hourly reporting WMO surface data in the Asian domain have been used to re-delineate the Asian dust source region and to determine the temporal variation of the threshold wind speed for the dust rise. The dust emission reduction factor due to vegetation in different surface soil-type regions (Gobi, sand, loess, and mixed soil) has been determined with the use of NDVI data. It is found that the threshold wind speed for the dust rise varies significantly with time (minimum in summer and maximum in winter) and surface soil types with the highest threshold wind speed of 8.0 m s−1 in the Gobi region and the lowest value of 6.0 m s−1 in the loess region. The statistical analysis of the spot/vegetation NDVI data enables to determine the emission reduction factor due to vegetation with the free NDVI value that is the NDVI value without the effect of vegetation and the upper limit value of NDVI for the dust rise in different soil-type regions. The modified ADAM2 model has been implemented to simulate two Asian dust events observed in Korea for the periods from 31 March to 2 April 2007 (a spring dust event) and from 29 to 31 December 2007 (a winter dust event) when the observed PM10 concentration at some monitoring sites in the source region exceeds 9,000 μg m−3. It is found that ADAM2 model successfully simulates the observed high dust concentrations of more than 8,000 μg m−3 in the dust source region and 600 μg m−3 in the downstream region of Korea. This suggests that ADAM2 has a great potential for the use of an operational Asian dust forecast model in the Asian domain.

Characterisation and source apportionment of PM10 in an urban background site in Lecce

The analysis reported in this work has been performed to characterise PM10 concentration measured in an urban background site in Lecce (Apulia region, Italy). PM10 concentration and its inorganic chemical composition have been studied using three procedures: a qualitative analysis of the correlation coefficients between the different species and of the crustal enrichment factor; the cluster analysis (CA) and the principal component analysis (PCA). The results of the three procedures are in good agreement. The five groups identified by the CA correspond to the five principal components obtained with the PCA and they reflect the results qualitatively inferred using the two-species correlation coefficients. The CA results helped in putting in evidence a correlation between Ni, V and sulphate that was less evident in the PCA. The relative abundance of V is larger with wind from the N-NW directions where the main industrial sites of the region are located. This suggests the presence of anthropogenic inorganic secondary aerosol generated by a common source of V and SO2 that are likely the industrial releases and the ship emissions. The absolute PCA (APCA) allowed the quantitative apportionment of the five components observed: crustal matter (49.5%), secondary inorganic aerosol (24.1%), marine aerosol (6.3%), traffic (16.5%), and industrial (2.1%). Observed PM10 concentration clearly shows a seasonal pattern, opposite to the one observed in the northern and central Italy, with average PM10 larger in the warm season (spring and summer) with respect to the cold season as a consequence of the increase of crustal matter contribution likely due to the intrusion of African dust. These intrusions are more frequent in the warm season and have an influence on daily PM10 concentrations variable between 6% and 120% in this site. Correlation with meteorological data indicates that the more intense cases of intrusions of African dust happen with wind blowing from the SW direction. Average PM10 concentration decreases of about 23% during precipitation. The decrease is mainly due to the decrease in crustal matter contribution and secondary inorganic aerosol. The sum of the other three sources is almost not changing during precipitation.

Measurement and modeling of respirable particulate (PM10) and lead pollution over Madurai, India

Samples of particulate matter less than or equal to 10 μm (PM10) were collected round the clock duration by using a respirable dust sampler (APM 460 BL) in Madurai, the second largest and most densely populated city of Tamil Nadu, India. The Environmental Protection Agency (EPA)-recommended standard methods were adopted not only for sample collection but also for subsequent analysis of respirable particulate pollutants. The observed PM10 concentrations varied from 88.1 to 226.9 μg/m3, and lead concentrations ranged between 0.21 to 1.18 μg/m3. The annual averages of the concentrations of the pollutants of current concern manifested that they were mostly below the Indian air quality standards and were generally comparable with those concentrations observed in most other Indian urban areas. The AERMOD model was validated simultaneously by comparing the predicted levels with the estimated levels of PM10. The generated database of the present investigation on the degree of pollution may be used for further research investigation and pollution abatement in the city.

Quantitative classification of northeast Asian dust events

In this paper, we introduce a quantitative classification of dust events on the basis of dust, PM10 concentration, and wind speed for northeast Asia. The empirical relationship between visibility and PM10 concentration is established by regression of visibility and PM10 concentration that were taken every 5 min at 11 sites in the spring of 2004 and 2005. The empirical relationship is then applied to establish the spatial and temporal patterns of dust and PM10 concentrations by using the visibility data obtained from 1680 meteorological stations in the spring seasons of 2000–2005. The results showed that the PM10 concentration estimated from visibility is consistent with the observed PM10 concentration. The classification standard of dust events used by different countries did not show consistent results in northeast Asia. It is recommended that dust events in northeast Asia be classified as follows: (1) severe dust storm, ρTSP ≥ 6000 μg m−3, ρPM10 ≥ 5000 μg m−3, and v ≥ 10 m s−1; (2) dust storm, 3000 μg m−3 ≤ ρTSP < 6000 μg m−3, 3000 μg m−3 ≤ ρPM10 < 5000 μg m−3, and 10 m s−1 ≤ v < 15 m s−1; (3) blowing dust, 900 μg m−3 ≤ ρTSP < 1500 μg m−3, 200 μg m−3 ≤ ρPM10 < 600 μg m−3, and 5 m s−1 ≤ v < 10 m s−1; and (4) floating dust, 750 μg m−3 ≤ ρTSP < 1200 μg m−3, 200 μg m−3 ≤ ρPM10 < 400 μg m−3, and 2 m s−1 ≤ v < 5 m s−1.

Application of LIDAR Technique and MM5-CMAQ Modeling Approach for the Assessment of Winter PM10 Air Pollution: A Case Study in Beijing, China

This paper reports the use of LIDAR technique, vertical wind profiler (VWP) and the coupled MM5-CMAQ air quality modeling system to investigate a high PM10 concentration episode occurred in Beijing, China during January 8–9, 2004. Through the regression analysis between the observed PM10 concentrations and the observed extinction coefficients, the converting formulas from the LIDAR records to the PM10 mass concentrations in Beijing have been found. Further, a 2-level-nested grid domain with spatial resolutions of 36 and 12 km have been designed and employed for this study, and the coupled MM5-CMAQ modeling system has then been evaluated using both the ground-level PM10 observations and the vertical profiles of PM10 deduced from the measured LIDAR extinction coefficients. Based on the verified modeling system, two emission scenarios were designed to quantitatively assess the trans-boundary PM10 contributions from the surrounding provinces of Beijing. The results illustrated that the particulate matter buildup over the Beijing region was due to a number of factors, including pollutants brought in from its surrounding provinces by the southwest winds and the emission from local sources within Beijing. It indicates that while Beijing needs to take positive steps to reduce its own pollution emissions, much effort should also be placed on demanding more pollution reduction and better environmental performance from its surrounding provinces.

The soil particle size dependent emission parameterization for an Asian dust (Yellow Sand) observed in Korea in April 2002

Abstract Intense Asian dust (Yellow Sand) events have been observed in Korea on 21–23 March and 7–9 April 2002. During these periods the observed PM10 concentrations were over 1000 μg m−3 at most monitoring sites in South Korea. The operational meteorological model of the Regional Data Assimilation and Prediction System of the Korea Meteorological Administration and the aerosol transport model with the improved particle size distribution parameterization developed at Seoul National University were used to simulate the intense Yellow Sand event observed on 7–9 April 2002. The comparison with the observational data shows that the present model system could reasonably simulate the evolutionary features of Yellow Sand over South Korea including the starting and ending time of the event, the particle size spectrum and the PM10 concentration. It was found that the dominant particle diameter in the mass concentration ranged from 3.67 to 10 μm during this dust event. A promising dust emission model depending on the particle size distribution constructed by the sum of several log-normal distributions of particle sizes of different soil types has been developed and found to yield better spectral-mass concentration in the size range of larger than 10 μm. This result suggests that size distributions of Asian dust (Yellow Sand) are consistent with those found in the USA, Central Asia and the Sahara desert. However, the accuracy of the model requires more detailed soil particle distributions in the source region.