Showing papers in "Aerosol and Air Quality Research in 2014"

Emission of Air Pollutants from Crop Residue Burning in India

Abstract: Agricultural crop residue burning contribute towards the emission of greenhouse gases (CO2, N2O, CH4), air pollutants (CO, NH3, NOx, SO2, NMHC, volatile organic compounds), particulates matter and smoke thereby posing threat to human health. In the present study a state-wise inventory of crop residue burnt in India and the air pollutants emitted was prepared using the Inter-Governmental Panel on Climate Change (IPCC) national inventory preparation guidelines for the year 2008–09. Total amount of residue generated in 2008–09 was 620 Mt out of which ~15.9% residue was burnt on farm. Rice straw contributed 40% of the total residue burnt followed by wheat straw (22%) and sugarcane trash (20%). Burning of crop residues emitted 8.57 Mt of CO, 141.15 Mt of CO2, 0.037 Mt of SOx, 0.23 Mt of NOx, 0.12 Mt of NH3 and 1.46 Mt NMVOC, 0.65 Mt of NMHC, 1.21 Mt of particulate matter for the year 2008–09. The variability of 21.46% in annual emission of air pollutants was observed from 1995 to 2009.

A Review: CO2 Utilization

Abstract: Global warming due to the accumulation of atmospheric CO2 has received widespread attention in recent years. Although various CO2 capture technologies have been proposed, using the captured CO2 from power plants is increasingly popular because of concerns with regard to the safety of underground and ocean CO2 storage. Various techniques related to utilization of CO2 from the exhausted gas of power plants are discussed in this article. The existing and under-development technologies for CO2 utilization in the world are briefly reviewed. Two categories, direct utilization of CO2 and conversion of CO2 to chemicals and energy products, are used to classify different forms of CO2 utilization. Regarding the direct utilization of CO2, in addition to its use in soft drinks, welding, foaming, and propellants, as well as the use of supercritical CO2 as a solvent, CO2 capture via photosynthesis to directly fix carbon into microalgae has also attracted the attention of researchers. The conversion of CO2 into chemicals and energy products via this approach is a promising way to not only reduce the CO2 emissions, but also generate more economic value. Since CO2 is just a source of carbon without hydrogen, a clean, sustainable and cheap source of hydrogen should be developed. This article reviews the literature on the production of biofuel from microalgae cultivated using captured CO2, the conversion of CO2 with hydrogen to chemicals and energy products, and sustainable and clean sources of hydrogen, in order to demonstrate the potential of CO2 utilization.

Understanding the Reaction Mechanism of Photocatalytic Reduction of CO2 with H2O on TiO2-Based Photocatalysts: A Review

Abstract: Recently, there has been an increasing interest in the research of photocatalytic reduction of CO2 with H2O, an innovative way to simultaneously reduce the level of CO2 emissions and produce renewable and sustainable fuels. Titanium dioxide (TiO2) and modified TiO2 composites are the most widely used photocatalysts in this application; however, the reaction mechanism of CO2 photoreduction on TiO2 photocatalysts is still not very clear, and the reaction intermediates and product selectivity are not well understood. This review aims to summarize the recent advances in the exploration of reaction mechanism of CO2 photoreduction with H2O in correlation with the TiO2 photocatalyst characteristics. Discussions are provided in the following sections: (1) CO2 adsorption, activation and dissociation on TiO2 photocatalyst; (2) mechanism and approaches to enhance charge transfer from photocatalyst to reactants (i.e., CO2 and H2O); and (3) surface intermediates, reaction pathways, and product selectivity. In each section, the effects of material properties are discussed, including TiO2 crystal phases (e.g., anatase, rutile, brookite, or their mixtures), surface defects (e.g., oxygen vacancy and Ti^(3+)) and material modifications (e.g., incorporation of noble metal, metal oxide, and/or nonmetal species to TiO2). Finally, perspectives on future research directions and open issues to be addressed in CO2 photoreduction are outlined in this review paper.

Characterization of PM2.5 Major Components and Source Investigation in Suburban Hong Kong: A One Year Monitoring Study

Abstract: PM2.5 filter sampling was conducted on a daily basis at the HKUST Air Quality Research Supersite (AQRS) for one year from March 2011 to February 2012. Approximately one fifth of the filter samples were subjected to full chemical analysis including major ions, elements, organic carbon (OC), elemental carbon (EC), and non-polar organic compounds (NPOCs). The major ions (sulfate, nitrate, and ammonium) were compared with those measured online by a MARGA system and the two sets of data were found in agreement within 25% or better. The major PM2.5 components (crustal materials, organic matter, soot, ammonium sulfate, ammonium nitrate, and non-crustal trace elements) accounted for 90% of the measured mass with sulfate being the most abundant (32.0%), followed by organic matter (23.5%) and ammonium (11.8%). The monthly variation patterns for different components suggested variable regional/super-regional sources, reflecting variation of transport contribution caused by shifts in synoptic weather conditions. Receptor modeling analysis by Positive Matrix Factorization revealed that secondary sulfate formation process (annual average of 31%), biomass burning (23%), and secondary nitrate formation process (13%) were the three dominant contributing sources to the observed PM2.5 at HKUST AQRS throughout the sampling year. The PM2.5 mass concentrations of all the individual sampling days were within the recently-proposed AQOs standards by the Hong Kong government (35 µg/m 3 for annual average and 75 µg/m 3 for 24-hr average) while approx. 52% of the sampling days were recorded with PM2.5 concentrations exceeding the WHO health 24-hr standards of 25 µg/m 3 . Major composition and source analysis showed that the increased mass concentrations on high PM days were mainly caused by air pollutant transport from the outside-Hong Kong regions. Results from this study indicate the importance of regional/super-regional strategies such as reduction in SO2, NO2 (precursors for secondary inorganic aerosols) and restricting biomass burning for lowering PM2.5 in Hong Kong.

Comparison of CO2 Photoreduction Systems: A Review

Abstract: Carbon dioxide (CO2) emissions are a major contributor to the climate change equation, and thus strategies need to be developed in order to reduce increases in CO2 levels in the atmosphere. One of the most promising approaches is to convert CO2 into useful products in engineered processes. The photocatalytic reduction of CO2 into hydrocarbon fuels is a promising way to recycle CO2 as a fuel feedstock by taking advantage of the readily available solar energy. This article reviews the basics of CO2 photoreduction mechanisms, limiting steps, possible strategies to enhance photoreduction efficiency, and the state-of-the-art photocatalytic systems for CO2 reduction. In particular, a comparison between different catalytic systems, including biological (plants and algae), inorganics (semiconductors), organics (molecular complexes), and hybrid (enzyme/semiconductors) systems is provided.

Comparison of filtration efficiency and pressure drop in anti-yellow sandmasks, quarantine masks, medical masks, general masks, and handkerchiefs

Abstract: Particulate respirators have been used in both general environments and in the workplace. Despite the existence of certified respirators for workers, no strict regulations exist for masks worldwide. The aims of this study were to evaluate the filter efficiency of various mask types using the Korean Food and Drug Administration (KFDA) [similar to the European Union (EU) protocol] and the National Institute for Occupational Safety and Health (NIOSH) protocol and to compare the test results. We tested a total of 44 mask brands of four types (anti-yellow sand, medical, quarantine, general) and handkerchiefs with a TSI 8130 Automatic Filter Tester. A wide variation of penetration and pressure drops was observed by mask types. The overall mean penetration and pressure drop of all tested masks were respectively 35.6 ± 34.7%, 2.7 ± 1.4 mm H2O with the KFDA protocol, and 35.1 ± 35.7%, 10.6 ± 5.88 mm H2O with the NIOSH protocol. All tested quarantine masks satisfied the KFDA criterion of 6%. Six-ninths and four-sevenths of the anti-yellow sand masks for adults and children satisfied the criterion of 20%, respectively. Medical masks, general masks, and handkerchiefs were found to provide little protection against respiratory aerosols.

Study of Surface Morphology, Elemental Composition and Origin of Atmospheric Aerosols (PM2.5 and PM10) over Agra, India

Abstract: In situ measurements of PM (PM2.5 and PM10) particles were carried out using a medium volume air sampler (offline) and particle number concentrations of PM were measured by a Grimm aerosol spectrophotometer (online) during the study period of 2010–2011. The morphology and elemental composition analyses of PM were performed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS), respectively. The average mass concentrations of PM2.5 and PM10 were 97.2 and 242.6 µg/m 3 at roadside (RD) and 121.2 and 230.5 µg/m 3 at a semirural (SR) site, respectively. These concentrations were substantially higher than the NAAQS, WHO and USEPA standards. The highest mass and number concentrations of PM2.5 and PM10 were observed during winter, followed by those during the post-monsoon period and summer, with the lowest in the monsoon period. SEM and EDS analysis of PM indicated the presence of soot, mineral, tarballs, fly ash, aluminosilicates/silica, fluorine, carbon rich, and Cl-Na rich particles. Of these particles, soot, tarballs, and F-C rich particles dominate in PM2.5, whereas mineral, aluminosilicates, and Cl-Na rich particles dominate in PM10. The morphology and elemental composition of the particles varied over the seasons due to atmospheric processing. The highest carbon concentration (56%) was observed in PM2.5 during summer at the RD, while in the monsoon, postmonsoon period and winter the carbon concentration was ~9% lower at the RD as compared to the SR. However, the concentration of carbon in PM10 was ~38% higher at the RD as compared to SR during both summer and winter. Air mass backward trajectory cluster analysis was performed, and the results indicate that the aerosol loadings over Agra are mainly transported from the Middle East and Arabian Sea during the summer and monsoon period, while during the pre-monsoon period and winter the aerosol loadings came from the northern region, and were due to the burning of biomass and coal, as well as other local activities.

Source Profiles of Volatile Organic Compounds from Biomass Burning in Yangtze River Delta, China

Abstract: The volatile organic compounds (VOCs) associated with biomass burning were characterized in the Yangtze River Delta of China, including two types of burning conditions (stove burning and field burning) and five typical kinds of biomass (straws of rice, wheat, bean and rape, and wood). According to the results, the VOC emission factors of straw burning ranged from 2.08 g/kg to 6.99 g/kg with an average of (4.89 ± 1.70) g/kg, compared to 0.98 g/kg for wood burning. Some differences in VOC composition were observed with the burning of different biomasses. Oxygenated VOC (o-VOC) were the largest contributors to the mass concentration of measured VOCs from straw burning, with a proportion of 49.4%, followed by alkenes 21.4%, aromatics 13.5%, alkanes 10.6% and halogenated VOC (x-VOC) 5.0%. More aromatics and x-VOC were emitted from wood burning compared with straw burning. Field burning emitted more o-VOC due to more air being supplied during the burning test compared with stove burning. Further examination of the detailed VOC species showed the most abundant VOC species from biomass burning were o-VOC, C2–C3 alkenes and C6–C7 aromatics. The ozone formation potential (OFP) of VOCs from straw burning was in the range of 13.92–33.24 g/kg, which was much higher than that of wood burning (4.30 g/kg). Alkenes and o-VOC were the largest contributors to OFP of VOCs from biomass burning. The top five contributors of OFP were ethene, n-hexanal, propylene, acetaldehyde and methyl vinyl ketone, the sum of which accounted for 77% of total OFP. The ratio of ethylbenzene to m,p-xylenes from biomass burning was significantly higher than those from other VOC sources, and thus this could be seen as the fingerprint of biomass burning.

Impact of relative humidity and water soluble constituents of PM2.5 on visibility impairment in Beijing, China

Abstract: Beijing has been experiencing severe particulate pollution accompanying the fast growing population and economy. This study investigated the impact of PM2.5 and its water soluble organic and inorganic constituents on visual impairment in Beijing under different meteorological conditions. According to the analysis of PM2.5 samples collected in Spring 2012, water soluble species took up 38.1% of PM2.5 mass, among which NO3– was the most abundant constituent, followed by SO42–, NH4+ and water soluble organic matter. The correlation analysis between visibility and aerosol loadings as well as meteorological parameters revealed the dominant impact of meteorological conditions, relative humidity in particular, on visibility impairment over the mass concentration of PM2.5. Compared to the total aerosol loading of PM2.5, visibility was better correlated with the total mass of water soluble constituents (WSC). The visual range in Beijing was the most sensitive to both WSC and PM2.5 in the RH range of 30–70%. Severe visual impairment was observed for RH ? 70% with the least sensitivity to WSC and PM2.5. The effects of synoptic scale circulation on meteorological variables that affect air quality were also examined with the movement of a cold front as a case study. The findings have direct implications to region-wide policy-making and control strategies. (Less)

Source Profiles and Chemical Reactivity of Volatile Organic Compounds from Solvent Use in Shanghai, China

Abstract: Chamber experiments, exhaust collection, and in-situ sampling were employed to study the emission profiles of volatile organic compounds (VOCs) from solvent use, specifically indoor paint, auto paint, furniture paint, and print ink, which are of significant importance with regard to VOC emissions in Shanghai. The results showed that there were some differences among these VOC source profiles of the emissions associated with different solvents. On the one hand, for emissions from imported indoor solvents, ~50% of the total mass concentration was contributed by aromatics, and ~30% by alkanes. On the other hand, VOC source profiles from domestic indoor paint, furniture paint, and auto paint were similar in the sense that aromatics made a much larger contribution to total VOCs, specifically, 98% for domestic indoor paint, 80%–93% for the other two, and C8–C9 aromatics accounted for ~70% of total VOCs. For VOCs from printing, C2–C5 species dominated by more than 50%, followed by C8–C9 aromatics. VOCs from the use of different solvents presented different chemical reactivities. Among the four solvents listed above, the average OH loss rate constant (k-avg) and maximum incremental reactivity (MIR-avg) of VOCs from printing were the lowest, with values of 8.2 × 10 –12 cm 3 /molecule/s and 2.9 g(O3)/g(VOC), respectively. For VOCs from painting, the average reactivity was twice that of VOCs from printing, and its value of MIR-avg was 4.7–6.3 g(O3)/g(VOC). There are significant variations in the VOC source profiles related to solvent use in different studies. The representativeness of the solvents studied and the VOC samples collected should thus be more closely examined. The accuracy of VOC source profiles related to solvent use is highly dependent on location and sampling frequency.

Comparing the Performance of Statistical Models for Predicting PM10 Concentrations

Abstract: The ability to accurately model and predict the ambient concentration of Particulate Matter (PM) is essential for effective air quality management and policies development. Various statistical approaches exist for modelling air pollutant levels. In this paper, several approaches including linear, non-linear, and machine learning methods are evaluated for the prediction of urban PM10 concentrations in the City of Makkah, Saudi Arabia. The models employed are Multiple Linear Regression Model (MLRM), Quantile Regression Model (QRM), Generalised Additive Model (GAM), and Boosted Regression Trees1-way (BRT1) and 2-way (BRT2). Several meteorological parameters and chemical species measured during 2012 are used as covariates in the models. Various statistical metrics, including the Mean Bias Error (MBE), Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), the fraction of prediction within a Factor of Two (FACT2), correlation coefficient (R), and Index of Agreement (IA) are calculated to compare the predictive performance of the models. Results show that both MLRM and QRM captured the mean PM10 levels. However, QRM topped the other models in capturing the variations in PM10 concentrations. Based on the values of error indices, QRM showed better performance in predicting hourly PM10 concentrations. Superiority over the other models is explained by the ability of QRM to model the contribution of covariates at different quantiles of the modelled variable (here PM10). In this way QRM provides a better approximation procedure compared to the other modelling approaches, which consider a single central tendency response to a set of independent variables. Numerous recent studies have used these modelling approaches, however this is the first study that compares their performance for predicting PM10 concentrations.

Validation of MicroAeth® as a Black Carbon Monitor for Fixed-Site Measurement and Optimization for Personal Exposure Characterization.

Abstract: This paper reports on validation experiments with the recently developed microAeth®, a pocket-sized device which is able to obtain real-time and personal measurements of black carbon (BC) aerosol. High reproducibility was observed when comparing the results from six new individual units during fixed-site monitoring out of a window (relative standard deviation [RSD] = 8% ± 5%, N = 1442). The results obtained from the microAeth devices agreed with those obtained from a full size rack mounted Aethalometer, based on both the 1-minute data (R = 0.92, slope = 1.01 ± 0.01, N = 1380) and 24-h average data. The 24-h average of real time data obtained from the microAeths was comparable to the BC concentration obtained from 24-h integrated PM2.5 filter deposits, as determined by multi-wavelength optical absorption (R = 0.98, slope = 0.92 ± 0.07, N = 12). Rapid environmental changes in relative humidity (RH) and temperature (T) can result in false positive and negative peaks in the real time BC concentrations, though averages > 1–2-hour are only minimally affected. An inlet with a diffusion drier based on Nafion® tubing was developed in order to use BC data with a high time resolution. The data shows that the diffusion drier greatly reduce the impacts from rapid changes in RH and T when the monitoring system is worn in close proximity to the body (e.g., in the vest pocket).

Seasonal Variability of Atmospheric Aerosol Parameters over Greater Noida Using Ground Sunphotometer Observations

Abstract: Atmospheric aerosols over northern India are subject of significant temporal and spatial variability and many studies have been carried out to investigate their physico-chemical and optical properties. The present work emphasizes on examining the aerosol optical properties and types over Greater Noida, Delhi region, using ground-based sun photometer data during the period 2010–2012. The analysis reveals a relatively high mean aerosol optical depth at 500 nm (AOD500 = 0.82 ± 0.39), associated with a moderate Angstrom exponent α440–870 of 0.95 ± 0.37. Both parameters, exhibit significant daily, monthly and seasonal variability with higher values of AOD500 during post-monsoon (0.98 ± 0.50) and winter (0.87 ± 0.35) seasons associated with high α values (> 1.1) suggesting significant urban and biomass-burning contribution. On monthly basis, the highest AOD is found during July and November and the lowest one in the transition months of March and September. The aerosol-type discrimination via the relationship AOD vs. α shows a clear dominance of urban/industrial and biomass-burning aerosols during post-monsoon and winter in fractions of 74.5% and 72%, respectively, while aerosols of desert-dust characteristics were most frequent in pre-monsoon (41.7%) and monsoon (21%) seasons. In general, the analysis shows a rather well-mixed aerosol type under very turbid atmosphere, which is associated with the long range transport of pollutants through the westerly winds from the Thar desert and biomass burning in the western parts of India. Keyword: Atmospheric aerosols; Sunphotometer; Aerosol optical depth; Dust storm; AERONET; Dust; Biomass burning.

Temporal Variation of Particulate Matter (PM) and Potential Sources at an Urban Site of Udaipur in Western India

Abstract: Measurements of mass concentrations of particulate matters (PM_(2.5) and PM_(10)) and mixing ratio of carbon monoxide (CO) were made at an urban site of Udaipur (24.58°N, 73.68°E) in India from April 2010 to March 2011. Concentrations of PM_(2.5), PM_(10) and CO show strong diurnal and seasonal variations. The highest concentrations coincide with the rush traffic and lower nocturnal boundary layer depth. The lowest concentrations in the afternoon hours are attributed to the dilution caused by higher boundary layer height and reduced traffic. The levels of trace constituents during the weekend were significantly reduced compared to the weekdays of observations. The daily PM_(2.5), PM_(10) and CO varied in the large ranges of 8-111 μg/m^3, 28-350 μg/m^3 and 145-795 ppbv, respectively. PM_(2.5) and CO show strong seasonality with higher and lower values during winter and monsoon seasons, respectively, while PM_(10) shows highest value during the premonsoon season. Flow of cleaner marine air and negligible biomass burning resulted in lower values in the monsoon season. Long-rang transport and extensive biomass burning caused higher values in winter and pre-monsoon seasons. Back trajectories show seasonal shift in the long- range transport which is consistent with the seasonality of aerosols and CO. Except for the monsoon season, mass concentrations of PM_(2.5) and PM_(10) show good correlation (typically r^2 ＞ 0.5). Relations of PM_(2.5) and PM_(10) with CO varied with the season but show good correlations (r^2 ＞ 0.5) during the winter season, while poor correlation during monsoon. The correlations suggest dominance of combustion related emissions particularly during winter season. Monthly emission ratios of ΔPM_(2.5)/ΔPM_(10), ΔPM_(2.5)/ΔCO and ΔPM_(10)/ΔCO varied in the ranges of 0.19-0.31 μg/m^3/ppbv, 0.05-0.10 μg/m^3/ppbv and 0.15-0.25 μg/m^3/ppbv, respectively. The mass concentration of PM_(2.5) tends to decrease with the increasing wind speed, while PM_(10) increases with wind speed.

Source Characterization of Trace Elements in Indoor Environments at Urban, Rural and Roadside Sites in a Semi Arid Region of India

Abstract: The present study investigated the particle size distribution of trace metals (Fe, Pb, Mn, Cu, Ni, Cr, Zn, Cd, Hg, and As) in the domestic environment, and examined the relationships among the levels of these metals and identified the related sources. Five homes at each site i.e., urban, rural and roadside, were selected for sampling. PM_(10) and PM_(2.5) samples were collected by using an APM-550 particulate sampler. Metals were analyzed by AAS after acid digestion. The monthly average PM_(2.5) concentration ranged from 80 to 184.67 μg/m^3, while the PM_(10) monthly concentration ranged from 167.56 to 307.95 μg/m^3. PM_(2.5) contributed 50-56% of PM_(10). The total contribution of the analyzed trace metals in PM_(2.5) was 6.2% while in PM_(10) it was 2.2%. This followed the order Fe ＞ Zn ＞ Pb ＞ Cr ＞ Ni ＞ Cu ＞ Mn. Pb and Ni exceeded the prescribed annual National Ambient Air Quality Standards (NAAQS) given by the Central Pollution Control Board (CPCB) by up to 5 and 36 times, respectively. For Pb and Ni it is 0.50 μg/m^3 and 0.02 μg/m^3, respectively. The particle mass was concentrated in the coarse size fraction, and the mass of individual trace metals was concentrated in finer sizes (except Fe), which is a major issue of concern. Intercorrelations and Principal Component Analysis were used to classify the two groups of sources, one from house dust and anthropogenic activities indoors, and the other from infiltration from outdoors. Enrichment factors with respect to outdoor metal concentrations have been identified for each metal. Fe was found to be totally contributed by outdoor dust. Mn and Cr are found to be less enriched, while Pb, Ni, Zn and Cu were found to have indoor sources.

Seasonal Variation of Physical and Chemical Properties in TSP, PM10 and PM2.5 at a Roadside Site in Beijing and Their Influence on Atmospheric Visibility

Abstract: In Beijing, capital of China, decreasing visibility has become a serious problem on people's life, thus a hot environmental concern. An urban roadside site in Beijing was chosen to collect 24-h TSP, PM10 and PM2.5 samples for one month each season from June 2009 to March 2010. The PM mass concentrations, and the concentrations of ions, EC, OC and metals in PM10 and PM2.5 were measured, and their correlation with visibility, as well as the influence of weather factors on visibility were studied. The results showed that daily mean concentrations of TSP, PM10 and PM2.5 were 75-1350 μg/m^3 (mean 275.8), 29-448 μg/m^3 (mean 187) and up to 300 μg/m^3 (mean 92.6), with the number of days exceeding the secondary standard (GB3095-2012) representing 33.3%, 59.8% and 51.0%, respectively. All PM concentrations were higher in spring than in other seasons. Obvious seasonal variations were observed for certain ions, OC, EC and metal concentrations in PM10 and PM2.5. Average mean visibility was low (5.64 km), showing better visibility in summer than in other seasons. PM10 and PM2.5 showed stronger negative correlation with visibility giving coefficients of -0.52 and -0.50. Almost all significant correlations were negative and occurred in autumn for visibility with TSP, PM10 and PM2.5, and with ions, EC and OC in both PM10 and PM2.5. The only positive and significant correlation was found between fine OC and visibility. Negative and significant correlations were also observed for visibility with humidity in autumn and winter, and with minimum temperature in all seasons but summer.

Chemical Characterization of Summertime Dust Events at Kanpur: Insight into the Sources and Level of Mixing with Anthropogenic Emissions

Abstract: The aim of this study conducted at Kanpur (26.51°N, 80.23°E), India, was to quantify chemical properties of dust and the intensity of mixing, due to its interaction with various emissions from anthropogenic activities, during its long range transport. Aerosol mass was collected at Indian Institute of Technology, Kanpur (IIT-K) located in the Indo-Gangetic Plain from April–July 2011, a period marked by intense dust storms and onset of monsoon. The sampling days were classified as Dust, Polluted Dust1 (PD1), Polluted Dust2 (PD2) and Continental days. PM10 (coarse mode) and PM2.5 (fine mode) collected on filter substrates were analysed for chemical composition. Elemental concentrations were measured using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). The results show that crustal elements like Ca, Fe, K, Na and Mg were dominant in coarse mode during dusty days, whereas, elements of anthropogenic origin like Cu, Ni, Se and V were mostly concentrated in fine mode during PD1 as well as PD2. Very low elemental concentrations were found during continental days. SO4 2– , Cl – and NO3 – were found to be high during PD1 and PD2 days. Very good correlations of NH4 + with Cl – and SO4 2– ions in PD1 days indicate their common sources of origin and formation of ammonium chloride and ammonium sulphate. Water Soluble Inorganic Carbon (WSIC) was found during all dust days, Water Soluble Organic Carbon (WSOC) was found to be highest during PD1 and PD2 days.

Composition of PM2.5 and PM10 Collected at Urban Sites in Brazil

Abstract: Atmospheric particulate matter samples (PM2.5 and PM10) were collected at urban sites (Sao Paulo, SPA; Piracicaba, PRB) in Sao Paulo State, Brazil. In order to characterize the chemical composition of particulate matter, several chemical components were analyzed from the samples, and among these were inorganic and organic anions, monosaccharide anhydrides, and organic and elemental carbon. Long-range transport of the particulate matter while sugar cane was being burned contributed to an increase in PM2.5 and PM10 concentrations at the SPA site. Sulphate, nitrate, ammonium, elemental carbon and particulate organic material (POM) were major components of the total PM2.5 and PM2.5-10. The contribution of POM to PM2.5 at PRB was 29%, similar to the results found for the winter season at the SPA site.The Cl^-/Na^+ ratio at the SPA site for PM2.5 was different from that at the other site, with chloride depletion indicating several sources beyond sea salt. The occurrence of levoglucosan and its correlations with potassium confirm the contribution of local biomass burning (at PRB) and long-range transported particles at SPA. OC/EC ratios and the correlation coefficients indicated secondary formation of OC at both sites.

Aerosol Characteristics and Radiative Forcing during Pre-Monsoon and Post- Monsoon Seasons in an Urban Environment

Abstract: The present study reports on aerosol characteristics and radiative properties utilizing ground based Aerosol Robotic Network (AERONET) data for the pre-monsoon (March, April, May) and post-monsoon (September, October, November) seasons over Lahore, Pakistan, for the two years during 2009–2010. The Aerosol Optical Depth (AOD) data from AERONET and a Moderate Resolution Imaging Spectro-radiometer (MODIS) were compared in order to validate both systems. The correlation coefficient for the post-monsoon season was > 0.68 in comparison to > 0.66 for the pre-monsoon season. In the pre-monsoon season, AERONET and MODIS AOD values were in the range of 0.2 to 1.2, and 0.2 to 1.67, respectively. For the post-monsoon season, these values were in the range of 0.17 to 2.46, and 0.15 to 2.45 for AERONET and MODIS, respectively. Strong dust loading resulted in higher values for the coarse particles during the pre-monsoon period, followed by an increase in the absorbing anthropogenic aerosols with the change from the pre-monsoon to post-monsoon season. The higher dust loading corresponded to the higher values of the real part of the refractive index in the pre-monsoon season, causing a relatively large single scattering albedo (SSA) (0.85–0.915) and thus a higher value for the asymmetry parameter (ASY). Similarly, the higher value of absorbing anthropogenic aerosols resulted in a higher value for the imaginary part of the refractive index in the post-monsoon period, followed by relatively lower values for SSA (0.88–0.911) and ASY. The averaged aerosol radiative forcing (ARF) for the pre-monsoon period at the top of the atmosphere was –19 ± 6 W/m 2 , while at the surface it was –93 ± 22 W/m 2 leading to an atmospheric forcing of +74 ± 16 W/m 2 . Likewise, the averaged ARF for the post-monsoon period at the top of the atmosphere was –28 ± 8 W/m 2 , while at the surface it was –98 ± 24 W/m 2 leading to an atmospheric forcing of +70 ± 15 W/m 2 , indicating significant heating of the atmosphere.

Influence of Biomass Burning on the Levels of Atmospheric Polycyclic Aromatic Hydrocarbons and Their Nitro Derivatives in Chiang Mai, Thailand

Abstract: Chiang Mai and several other provinces in northern Thailand have been annually facing air pollution problems during the dry season. Ten polycyclic aromatic hydrocarbons (PAHs); 19 nitropolycyclic aromatic hydrocarbons (NPAHs); and levoglucosan (LG), a marker for biomass burning, were quantified in total suspended particulates (TSP) collected in Chiang Mai during the dry, transition, and wet seasons in 2010. The concentrations of PAHs and NPAHs in the dry season were significantly higher than in the wet season. The [Benzo[a]pyrene (BaP)] – [benzo[ghi]perylene (BghiPe)] ratio, as an indicator of traffic, and the correlations of PAHs and NPAHs with LG showed that biomass burning significantly contributes to air pollution in the dry season. 9-Nitroanthracene (9-NA) was the most abundant NPAH which suggests that 9-NA is generated from biomass burning. We proposed the [9-NA] – [1-nitropyrene (1-NP)] ratio as a new indicator for assessing the contribution of biomass burning. Biomass burning was a major source of PAHs and NPAHs in the dry season, whereas vehicle exhaust was the main contribution in the wet season. The high carcinogenic risks in the dry season correlate with more harmful air conditions during this season. Thus, it is important to control biomass burning to reduce air-pollution-related health risks during the dry season in northern Thailand.

Content and Distribution of Trace Elements and Polycyclic Aromatic Hydrocarbons in Fly Ash from a Coal-Fired CHP Plant

Abstract: The levels of trace elements and polycyclic aromatic hydrocarbons (PAHs) in fly ash generated by coal combustion have received considerable attention in recent years, due to their potential environmental impact. Sixteen high priority PAHs and 14 trace elements in coal fly ash were measured. The particle sizes of fly ash showed a bimodal distribution, and most ash particles were within a range of 20–25 µm in diameter. The fly ash exhibited high contents of CaO and SO3, which was influenced by the desulfidation treatment of limestone. The Be, Cu, Ni, V, Se, Mo and Cd contents increased significantly with decreasing particle sizes of fly ash, while those of Zn and Pb showed no obvious trends. PAHs with three- and four-rings were the dominate species in all the fly ash. The amount low molecular weight PAHs with two-, three- and four- rings was inversely correlated with the particle sizes of the fly ash.

Towards Solar Thermochemical Carbon Dioxide Capture via Calcium Oxide Looping: A Review

Abstract: This article presents a review of research in the field of solar thermochemical carbon dioxide capture based on calcium oxide looping. Topics covered include thermodynamics, kinetics, and heat and mass transfer as well as reactor design, modeling, and testing.

Systematic Approach for the Prediction of Ground-Level Air Pollution (around an Industrial Port) Using an Artificial Neural Network

Abstract: The prediction of air pollution levels is critical to enable proper precautions to be taken before and during certain events. In this paper a rigorous method of preparing air quality data is proposed to achieve more accurate air pollution prediction models based on an artificial neural network (ANN). The models consider the prediction of daily concentrations of various ground-level air pollutants, namely CO, PM10, NO, NO2, NOx, SO2, H2S, and O3, which were measured by an ambient air quality monitoring station in Ghadafan village, located 700 m downwind of the emissions of Sohar Industrial Port on the Al-Batinah coast of Oman. The training of the models is based on the multi-layer perceptron (MLP) method with the Back-Propagation (BP) algorithm. The results show very good agreement between the actual and predicted concentrations, as the values of the coefficient of multiple determinations (R 2 ) for all ANN models exceeded 0.70. The results also show the importance of temperature in the daily variations of O3, SO2, and NOx, whilst the wind speed and wind direction play significant roles in the daily variations of NO, CO, NO2, and H2S. PM10 concentrations are influenced by almost all the measured meteorological parameters.

Microstructure and Chemical Composition of Diesel and Biodiesel Particle Exhaust

Abstract: The complexity and large variability of transport-emitted aerosols leads to necessity of comprehensive characterization of their physico-chemical and toxicological properties, remaining great uncertainties in health effect assessments. Particles produced by combustion of fossil diesel (B0), 20% rapeseed methyl ester in fossil diesel (B20), and pure rapeseed methyl ester (B100) were sampled from exhaust of an Opel Astra diesel engine using sulfated ash, phosphorous and sulfur (SAPS) lube oil with low and high ash content. Microscopic and chemical characterization is performed to quantify the common and specific properties of diesel/biodiesel exhausts. Hydrophobic saturated aliphatic dominate diesel particle chemistry. Oxygen and nitrogen-containing functionalities are specific for more hydrophilic biodiesel particles. A full range of chemical species for individual particles is grouped by clustering technique combined with water-soluble ion measurements. Analysis of group abundance shows carbonaceous particles (soot externally mixed with inorganic salts) and inorganic fly ash (metal oxides) in a structure of exhaust, in correlation with inorganic contaminations in fuel and lube oil. Quantification of particle types in terms of physicochemical relevance supports the identification of groups which may act as biomicromarkers discriminating between diesel and biofuel exhaust and micromarkers of using high ash lube oil, thus providing a basis for correlative toxicological assessment of diesel/biofuel engine emissions.

ab initio Thermodynamic Study of the CO2 Capture Properties of M2CO3 (M = Na, K)- and CaCO3-Promoted MgO Sorbents Towards Forming Double Salts

Abstract: The CO2 capture properties of M2CO3 (M = Na, K)-promoted and CaCO3-promoted MgO sorbents are investigated by first-principles density functional theory complemented with lattice phonon calculations. The calculated thermodynamic properties indicate that by forming double salts (M2Mg(CO3)2 and CaMg(CO3)2), compared to pure MgO, the maximum allowable CO2 capture temperatures of the M2CO3- and CaCO3- modified MgO sorbents are shifted to higher temperature ranges. Under pre-combustion conditions with PCO2 = 10 bar, the Na2CO3-promoted and CaCO3-promoted MgO sorbents can capture CO2 at temperatures as high as 915 K and 740 K respectively. While under post-combustion conditions with PCO2 = 0.1 bar, their maximum allowable CO2 capture temperatures are 710 K and 600 K respectively. However, when adding K2CO3 into MgO, under both pre- and post-combustion conditions, its maximum CO2 capture temperatures only increased about 10 K relative to pure MgO. These results indicate that by mixing another solid into MgO, it is possible to shift its CO2 capture temperature to fit practical industrial needs.

Source Apportionment of PM2.5 Using a CMB Model for a Centrally Located Indian City

Abstract: Samples of PM2.5 were collected sequentially for 24 hours during the last week of September to mid February 2009–10 at three locations representing residential (R), commercial (C) and industrial (I) sites in Nagpur city to determine their chemical composition and estimations of the sources contributing to them. Two receptor models were used for the source apportionment viz. enrichment factors (EF) to differentiate crustal and non-crustal sources, whereas chemical mass balance (CMB 8.2) was used to identify and quantify the major sources contributing to PM2.5. The ambient mass concentrations and chemical compositions of PM2.5 with respect to ionic species (Na+, NH4+, K+, Ca2+, F–, Cl–, NO3– and SO42–); carbonaceous species (organic and elemental carbon) and trace metals (Al, Ba, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Si and Zn) were determined. The most abundant chemical species were OC, EC, SO42–, NO3–, NH4+, K+ and trace metals (Al, Fe, Si, Mg, and Cu) at all the sites. Findings of EF showed the anthropogenic origin of Cd, Ni, Pb, Cu, Fe and Zn, whereas Ba, Cr, Mg, Mn, and Si were contributed from crustal sources. On the other hand, results of CMB using source profiles developed in India for non-vehicular and vehicular sources revealed that vehicular emissions were major contributing sources 57, 62 and 65%; followed by secondary inorganic aerosol 16, 12, 16%; biomass burning 15, 11, 9% and then by re-suspended dust 6,10, 7% at R, C and I sites, respectively. This study showed that while the sources at all three sites were mostly consistent, the percent contributions of these varied among the sites as per the intensity of ongoing activities at the receptor sites.

Facile Preparation of Nitrogen-Doped Activated Carbon for Carbon Dioxide Adsorption

Abstract: Nitrogen-doped activated carbons with high surface areas obtained from resorcinol and formaldehyde resins were evaluated as CO2 adsorbents in a simulated flue gas stream under anhydrous and humid conditions. These carbons were prepared using two approaches, namely ammonia treatment without nitric acid pre-oxidation and amination after preoxidation. The pre-oxidation of activated carbons considerably enhanced the nitrogen incorporation during the amination process. The amination temperature affects the content and type of nitrogen incorporated onto the carbon surface, as determined by X-ray photoelectron spectroscopy, which enhances the specific adsorbent-adsorbate interaction for CO2 in humid conditions. The presence of H2O in the feed gas significantly decreased CO2 adsorption for a very low nitrogen content of virgin activated carbon. A sample prepared via the amination of pre-oxidized carbon at 700°C (NORF700) exhibited excellent tolerance to moisture and the highest CO2 capacity of 2.10 mmol/g in a 7% CO2/83% N2/10% H2O wet stream at 50°C and 130 kPa. The high performance of NORF700 was ascribed to its high surface area, adequate micropore volume, and high amounts of pyrindinic-like and pyrrole-like nitrogen species. The results indicate that nitric acid preoxidation followed by ammonia treatment at 700°C is an appropriate process for preparing adsorbents for CO2 separation in post-combustion applications.

Indoor/Outdoor Relationships between PM10 and Associated Organic Compounds in a Primary School

Abstract: Airborne particulate matter (PM10) samples were collected daily, indoors and outdoors, in a primary school at Aveiro, Portugal, from February 28 to May 27, 2011. The carbonaceous content (organic and elemental carbon) was determined by a thermo-optical technique. The organic speciation of PM10 was performed by gas chromatography-mass spectrometry. Mean PM10 levels of 107 and 36 µg/m 3 were obtained in the schoolroom and outdoors, respectively. On average, organic carbon accounted for 30.0% of the mass of PM10 indoors, whereas a lower mass fraction of 21.3% was found outdoors. The lack of correlation between indoor and outdoor organic carbon and the much higher indoor levels suggest significant contributions by indoor sources. The most abundant organic compound classes were acids, sugars, polyols and n-alkanes. Infiltration of outdoor particles leads to contamination of the schoolroom with vehicle emissions, as well as emissions related to the burning of biofuel in nearby restaurants and bakeries. However, the much higher indoor concentrations than in the outdoor air for the majority of compounds suggest that the origin of much of the particulate matter is from within the school building (due to school activities and materials, skin debris, microorganisms, and so on), and this also includes the formation of secondary organic aerosols. Based on the concentrations of polycyclic aromatic hydrocarbons, a negligible cancer risk was estimated in relation to the air within the school.

Seasonal characteristics of aerosol black carbon in relation to long range transport over Tripura in Northeast India

Abstract: This study presents the characteristics of aerosol black carbon (BC) from a rural continental site, Agartala, located in the North-Eastern part of India using two year measurements from September 2010 to September 2012. Diurnal and seasonal variations are examined in relation to the unique geographical location, changeable meteorological conditions and distinct source characteristics. Winter season is characterized by extremely high BC concentration (17.8 ± 9.2 µg/m 3 ) comparable to those seen in urban environments of India, dropping off to much lower values during the monsoon (2.8 ± 1.7 µg/m 3 ). Even this lowest seasonal mean is rather high, given the rural nature of Tripura. Examination of the spectral dependence of aerosol absorption coefficients indicates that the main source of aerosol to total BC burden at Agartala is the fossil fuel combustions. Concentration weighted trajectory (CWT) analysis indicate that the characteristic high BC during winter is mostly associated with the advection from the Indo-Gangetic Plains (IGP), while the air mass pattern is constricted to the oceanic region during monsoon making BC aloft due to local pollution only.

Filterable and Condensable Fine Particulate Emissions from Stationary Sources

Abstract: PM_(2.5) emissions from stationary sources contain a filterable and condensable portion. In this study, USEPA Method 201A/202 are used to measure filterable and condensable PM_(2.5) emissions from 5 stationary sources (power plants, boilers, brick manufacturing plant, incinerators and arc furnaces). The average filterable PM_(2.5) concentrations for power plant, boiler, brick manufacturing plant, incinerator and arc furnace are 0.75, 16.9, 8.67 , 0.15 and 2.12 mg/Nm^3, respectively. The amount of PM_(2.5) residue on the exit tube of cyclone and front half of the filter holder is significantly higher when the filterable PM_(2.5) concentrations are low. It is necessary to collect both filter and the residue particulates to avoid underestimation of PM_(2.5) emissions. The condensable PM accounts for 61.2%, 73.5%, 44.2%, 52.8% and 51.2% of total PM_(2.5) for power plant, boiler, brick manufacturing plant, incinerator and arc furnace plant, respectively. The real PM_(2.5) contribution to the atmosphere would be underestimated if condensable PM is not included. The condensable PM fraction increases as the exhaust temperature rises. The inorganic fraction accounts for 89.0%,69.4%, 72.3%,89.8% and 72.8% of condensable PM, respectively, for power plant, boiler, brick manufacturing plant, incinerator and arc furnace. The inorganic fraction is dominant in the condensable PM, which might be due to the high content of SO_4.