Characterization of particulate polycyclic aromatic hydrocarbons in the east of France urban areas

Background

Air samples collected on three different urban sites in East of France (Strasbourg, Besan?on, and Spicheren), from April 2006 to January 2007, were characterized to measure the concentrations of polycyclic aromatic hydrocarbons (PAHs) in the particulate phase (PM₁₀) and to examine their seasonal variation, diurnal variations, and emission sources.

Results

The average concentrations of ??PAHs were 12.6, 9.5, and 8.9?ng?m^?3 for the Strasbourg, Besan?on, and Spicheren sites, respectively. Strong seasonal variations of individual PAH concentrations were found at the three sampling sites, with higher levels in the winter that gradually decreased to the lowest levels in the summer. The diurnal variations of PAH concentrations in summer presented highest concentrations during the morning (04:00?C10:00) and the evening (16:00?C22:00) times, indicating the important contribution from vehicle emissions, in the three sampling sites. Furthermore, the ratio of BaP/BeP suggests that the photochemical degradation of PAHs can suppress their concentrations in the midday/afternoon (10:00?C16:00), time interval of highest global irradiance. In winter, concentrations of PAH were highest during the evening (16:00?C22:00) time, suggesting that domestic heating can potentially be an important source for particulate PAH, for the three sampling sites.

Conclusion

Diagnostic ratios were used to identify potential sources of PAHs. Results showed that vehicle emissions may be the major source of PAHs, especially in summer, with a prevalent contribution of diesel engines rather than gasoline engines at the three sites studied, independently of the seasons.     

Sources of ambient volatile organic compounds and their contributions to photochemical ozone formation at a site in the Pearl River Delta, southern China

The Positive Matrix Factorization (PMF) receptor model and the Observation Based Model (OBM) were combined to analyze volatile organic compound (VOC) data collected at a suburban site (WQS) in the PRD region. The purposes are to estimate the VOC source apportionment and investigate the contributions of these sources and species of these sources to the O₃ formation in PRD. Ten VOC sources were identified. We further applied the PMF-extracted concentrations of these 10 sources into the OBM and found "solvent usage 1", "diesel vehicular emissions" and "biomass/biofuel burning" contributed most to the O₃ formation at WQS. Among these three sources, higher Relative Incremental Reactivity (RIR)-weighted values of ethene, toluene and m/p-xylene indicated that they were mainly responsible for local O₃ formation in the region. Sensitivity analysis revealed that the sources of "diesel vehicular emissions", "biomass/biofuel burning" and "solvent usage 1" had low uncertainties whereas "gasoline evaporation" showed the highest uncertainty.     

Environmental lead pollution threatens the children living in the Pearl River Delta region, China

Introduction and purpose

The objective of this study is to determine children??s blood lead levels and identify sources of lead exposure. Childhood lead exposure constitutes a major pediatric health problem today in China. A blood lead screening survey program for children in the age group of 2?C12?years residing in Pearl River Delta region, south of China, was carried out from Dec 2007 to Jan 2008.

Methods

Blood lead levels and lead isotope ratios of a total of 761 participants were assessed by inductively coupled plasma mass spectroscopy. Measurements of urban environmental samples for source identification of children lead exposure were also performed.

Results and conclusions

The geometric mean value of the children??s blood lead levels was 57.05???g/L, and 9.6% of them were higher than 100???g/L. The blood lead levels were still much higher than those in developed countries. Based on the data of environmental lead source inventories, lead isotopic tracing revealed that there is about 6.7% past used gasoline Pb embedded in Shenzhen residential dust and about 15.6% in Guangzhou dust, respectively.     

An integrated approach to identify the origin of PM10 exceedances

Purpose

This study was aimed to the development of an integrated approach for the characterization of particulate matter (PM) pollution events in the South of Italy.

Methods

PM₁₀ and PM_2.5 daily samples were collected from June to November 2008 at an urban background site located in Bari (Puglia Region, South of Italy). Meteorological data, particle size distributions and atmospheric dispersion conditions were also monitored in order to provide information concerning the different features of PM sources.

Results

The collected data allowed suggesting four indicators to characterize different PM₁₀ exceedances. PM_2.5/PM₁₀ ratio, natural radioactivity, aerosol maps and back-trajectory analysis and particle distributions were considered in order to evaluate the contribution of local anthropogenic sources and to determine the different origins of intrusive air mass coming from long-range transport, such as African dust outbreaks and aerosol particles from Central and Eastern Europe. The obtained results were confirmed by applying principal component analysis to the number particle concentration dataset and by the chemical characterization of the samples (PM₁₀ and PM_2.5).

Conclusions

The integrated approach for PM study suggested in this paper can be useful to support the air quality managers for the development of cost-effective control strategies and the application of more suitable risk management approaches.     

Microbial structure and chemical components of aerosols caused by rotating brushes in a wastewater treatment plant

Purpose

Bacterial community structure and the chemical components in aerosols caused by rotating brushes in an Orbal oxidation ditch were assessed in a Beijing municipal wastewater treatment plant.

Methods

Air samples were collected at different distances from the aerosol-generating rotating brushes. Molecular culture-independent methods were used to characterize the community structure of the airborne bacteria in each sample regardless of cell culturability. A clone library of 16S rDNA directly amplified from air DNA of each sample was constructed and sequenced to analyze the community composition and diversity. Insoluble particles and water-soluble ions emitted with microorganisms in aerosols were analysis by a scanning electron microscope together with energy dispersive X-ray spectroscopy and ion chromatogram analyzer.

Results

In total, most of the identified bacteria were Proteobacteria. The majority of sequences near the rotating brushes (the main source of the bioaerosols) were Proteobacteria (62.97 %) with ??-(18.52 %) and ??-(44.45?%) subgroups and Bacteroidetes (29.63 %). Complex patterns were observed for each sampling location, suggesting a highly diverse community structure, comparable to that found in water in the Orbal oxidation ditch. Accompany with microorganisms, 46.36???g/m³ of SO ₄ ^2? , 29.35???g/m³ of Cl^?, 21.51???g/m³ of NO ₃ ^? , 19.76???g/m³ of NH ₄ ⁺ , 11.42???g/m³ of PO ₄ ^3? , 6.18???g/m³ of NO ₂ ^? , and elements of Mg, Cl, K, Na, Fe, S, and P were detected from the air near the aerosols source.

Conclusions

Differences in the structure of the bacterial communities and chemical components in the aerosols observed between sampling sites indicated important site-related variability. The composition of microorganisms in water was one of the most important sources of bacterial communities in bioaerosols. Chemical components in bioaerosols may provide a media for airborne microorganism attachment, as well as a suitable microenvironment for their growth and survival in the air. This study will be benefit for the formulation of pollution standards, especially for aerosols, that take into account plant workers?? health.     

GC-MS analyses and chemometric processing to discriminate the local and long-distance sources of PAHs associated to atmospheric PM2.5

Purpose

This study presents a procedure to differentiate the local and remote sources of particulate-bound polycyclic aromatic hydrocarbons (PAHs).

Methods

Data were collected during an extended PM_2.5 sampling campaign (2009?C2010) carried out for 1?year in Venice-Mestre, Italy, at three stations with different emissive scenarios: urban, industrial, and semirural background. Diagnostic ratios and factor analysis were initially applied to point out the most probable sources. In a second step, the areal distribution of the identified sources was studied by applying the discriminant analysis on factor scores. Third, samples collected in days with similar atmospheric circulation patterns were grouped using a cluster analysis on wind data. Local contributions to PM_2.5 and PAHs were then assessed by interpreting cluster results with chemical data.

Results

Results evidenced that significantly lower levels of PM_2.5 and PAHs were found when faster winds changed air masses, whereas in presence of scarce ventilation, locally emitted pollutants were trapped and concentrations increased. This way, an estimation of pollutant loads due to local sources can be derived from data collected in days with similar wind patterns. Long-range contributions were detected by a cluster analysis on the air mass back-trajectories. Results revealed that PM_2.5 concentrations were relatively high when air masses had passed over the Po Valley. However, external sources do not significantly contribute to the PAHs load.

Conclusions

The proposed procedure can be applied to other environments with minor modifications, and the obtained information can be useful to design local and national air pollution control strategies.     

Heavy metals of the Tibetan top soils

Objective

Due to its high elevation, rare human activities and proximity to south Asia where industries are highly developed, it is required to investigate the fragile environment of the Tibetan Plateau. We are aiming to obtain the concentration level, source, spatial distribution, temporal variation and potential environmental risk of Tibetan soils.

Methods

A total of 128 surf ace soil samples were collected and analyzed f or V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd and Pb, and an additional 111 samples were analyzed f or Hg and total organic carbon. Concentration comparisons coupled with multivariate statistics were used to analysis the sources of elements of soils. We also carried out Risk assessment on the soils.

Results

Concentrations of Hg, Cr, Ni, Cd and Pb are slightly higher than those of the late 1970s. Concentrations of Cr and Ni are higher than averaged world background values. Tibetan soils present a high natural As concentration level.

Discussion

Anthropogenic sources may partly contribute to the elevated Hg, Cd and Pb concentrations. Cr and Ni are mainly originated from soil parent materials. Soil elements in Anduo and Qamdo regions may threaten the health of local people.

Conclusion

Heavy metal elements of Tibetan Plateau are mainly from the natural source. Arsenic present a high background level. Soil elements in Anduo and Qamdo regions may threaten the health of local people, which should be of concern to scientists and the government.     

Source apportionment of ultrafine and fine particle concentrations in Brisbane, Australia

Purpose

To investigate the significance of sources around measurement sites, assist the development of control strategies for the important sources and mitigate the adverse effects of air pollution due to particle size.

Methods

In this study, sampling was conducted at two sites located in urban/industrial and residential areas situated at roadsides along the Brisbane Urban Corridor. Ultrafine and fine particle measurements obtained at the two sites in June?CJuly 2002 were analysed by positive matrix factorization.

Results

Six sources were present, including local traffic, two traffic sources, biomass burning and two currently unidentified sources. Secondary particles had a significant impact at site 1, while nitrates, peak traffic hours and main roads located close to the source also affected the results for both sites.

Conclusions

This significant traffic corridor exemplifies the type of sources present in heavily trafficked locations and future attempts to control pollution in this type of environment could focus on the sources that were identified.     

Chemical mass balance receptor model applied to ambient C2–C9 VOC concentration in Seoul,Korea: Effect of chemical reaction losses

A chemical mass balance (CMB) receptor model was used for estimating the diurnal contributions of VOC emission sources to the ambient C₂–C₉ VOC concentration in Seoul, Korea. For this purpose, the VOC concentrations were measured in the morning, the afternoon, and the evening. The samples were collected using a 2-h integrated SUMMA canister. The source profiles were developed for the CMB calculation in the Seoul area. To investigate the effect of the chemical reaction loss of VOCs on the CMB calculation, the modified model employing a decay factor and the standard model that considers no loss were compared. The modified model estimated that the vehicle exhaust (52%) was the largest leading source of VOCs in the Seoul atmosphere, followed by the use of solvents (26%), gasoline evaporation (15%), the use of liquefied petroleum gas (LPG) (5%), and the use of liquefied natural gas (LNG) (2%). Relative source contribution for vehicle exhaust showed a clear diurnal variation with a high in the morning and evening and a low in the afternoon, while the contribution of evaporative emissions (gasoline evaporation and solvent usage) showed a different diurnal pattern from that of the vehicle exhaust, exhibiting a high in the afternoon and evening and a low in the morning. It was found that the difference between the total source contribution (μg m⁻³) estimated from these two models was not statistically significant. However, when the paired-sample t-test is applied to the individual sources, a significant difference was found for the vehicle exhaust and the solvent use. In addition, the modified model brought forth a better performance with high R² and low χ² as compared to those obtained from the standard model in the CMB calculation. The vehicle exhaust and solvent use were estimated to be the largest and the second largest contributors to ambient benzene as well as ozone formation potential (OFP), respectively. Based on above results we believe that incorporating the reaction loss in the CMB calculations helps to better fit the source profile to the ambient VOC concentrations. However, the reaction loss does not significantly affect the estimation of source contributions.     

Characterizing and locating air pollution sources in a complex industrial district using optical remote sensing technology and multivariate statistical modeling

Emissions of volatile organic compounds (VOCs) are most frequent environmental nuisance complaints in urban areas, especially where industrial districts are nearby. Unfortunately, identifying the responsible emission sources of VOCs is essentially a difficult task. In this study, we proposed a dynamic approach to gradually confine the location of potential VOC emission sources in an industrial complex, by combining multi-path open-path Fourier transform infrared spectrometry (OP-FTIR) measurement and the statistical method of principal component analysis (PCA). Close-cell FTIR was further used to verify the VOC emission source by measuring emitted VOCs from selected exhaust stacks at factories in the confined areas. Multiple open-path monitoring lines were deployed during a 3-month monitoring campaign in a complex industrial district. The emission patterns were identified and locations of emissions were confined by the wind data collected simultaneously. N,N-Dimethyl formamide (DMF), 2-butanone, toluene, and ethyl acetate with mean concentrations of 80.0?±?1.8, 34.5?±?0.8, 103.7?±?2.8, and 26.6?±?0.7 ppbv, respectively, were identified as the major VOC mixture at all times of the day around the receptor site. As the toxic air pollutant, the concentrations of DMF in air samples were found exceeding the ambient standard despite the path-average effect of OP-FTIR upon concentration levels. The PCA data identified three major emission sources, including PU coating, chemical packaging, and lithographic printing industries. Applying instrumental measurement and statistical modeling, this study has established a systematic approach for locating emission sources. Statistical modeling (PCA) plays an important role in reducing dimensionality of a large measured dataset and identifying underlying emission sources. Instrumental measurement, however, helps verify the outcomes of the statistical modeling. The field study has demonstrated the feasibility of using multi-path OP-FTIR measurement. The wind data incorporating with the statistical modeling (PCA) may successfully identify the major emission source in a complex industrial district.     

Source apportionment and location by selective wind sampling and Positive Matrix Factorization

In order to determine the pollution sources in a suburban area and identify the main direction of their origin, PM_2.5 was collected with samplers coupled with a wind select sensor and then subjected to Positive Matrix Factorization (PMF) analysis. In each sample, soluble ions, organic carbon, elemental carbon, levoglucosan, metals, and Polycyclic Aromatic Hydrocarbons (PAHs) were determined. PMF results identified six main sources affecting the area: natural gas home appliances, motor vehicles, regional transport, biomass combustion, manufacturing activities, and secondary aerosol. The connection of factor temporal trends with other parameters (i.e., temperature, PM_2.5 concentration, and photochemical processes) confirms factor attributions. PMF analysis indicated that the main source of PM_2.5 in the area is secondary aerosol. This should be mainly due to regional contributions, owing to both the secondary nature of the source itself and the higher concentration registered in inland air masses. The motor vehicle emission source contribution is also important. This source likely has a prevalent local origin. The most toxic determined components, i.e., PAHs, Cd, Pb, and Ni, are mainly due to vehicular traffic. Even if this is not the main source in the study area, it is the one of greatest concern. The application of PMF analysis to PM_2.5 collected with this new sampling technique made it possible to obtain more detailed results on the sources affecting the area compared to a classical PMF analysis.     

VOC source–receptor relationships in Houston during TexAQS-II

During the TRAMP field campaign in August–September 2006, C₂–C₁₀ volatile organic compounds (VOCs) were measured continuously and online at the urban Moody Tower (MT) site. This dataset was compared to corresponding VOC data sets obtained at six sites located in the highly industrialized Houston Ship Channel area (HSC). Receptor modeling was performed by positive matrix factorization (PMF) at all sites. Conditional probability functions (CPF) were used to determine the origin of the polluted air masses in the Houston area. A subdivision into daytime and nighttime was carried out to discriminate photochemical influences. Eight main source categories of industrial, mobile, and biogenic emissions were identified at the urban receptor site, seven and six, respectively, at the different HSC sites. At MT natural gas/crude oil contributed most to the VOC mass (27.4%), followed by liquefied petroleum gas (16.7%), vehicular exhaust (15.3%), fuel evaporation (14.3%), and aromatics (13.4%). Also petrochemical sources from ethylene (4.7%) and propylene (3.6%) play an important role. A minor fraction of the VOC mass can be attributed to biogenic sources mainly from isoprene (4.4%). Based on PMF analyses of different wind sectors, the total VOC mass was estimated to be twofold at MT with wind directions from HSC compared to air from a typical urban sector, for petrochemical compounds more than threefold. Despite the strong impact of air masses influenced by industrial sources at HSC, still about a third of the total mass contributions at MT can be apportioned to other sources, mainly motor vehicles and aromatic solvents. The investigation of diurnal variation in combination with wind directional frequencies revealed the greatest HSC impact at the urban site during the morning, and the least during the evening.     

Synthesis, properties and application research of atrazine Fe3O4@SiO2 magnetic molecularly imprinted polymer

Introduction

Magnetic Fe₃O₄ nanoparticles were prepared by coprecipitation and then were coated with SiO₂ on the surface.

Materials and methods

Fe₃O₄@SiO₂ composite microspheres were modified by KH570. Using molecular imprinting technology, atrazine magnetic molecularly imprinted polymer was prepared by using atrazine as template molecule, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linkers. The morphology, composition and magnetic properties of magnetic nanoparticles were characterized. The recognition selectivity of polymer was studied for template molecule and simulation by UV spectrophotometry. The adsorption properties and selectivity ability were analyzed by Scatchard analysis.

Results

Scatchard linear regression analysis indicated that there are two binding sites of the target molecules. The magnetic molecularly imprinted polymer has been applied to the analysis of atrazine in real samples.

Conclusion

The results show that: the recovery rates and the relative standard deviation were 94.0??98.7% and 2.1??4.0% in corn, the recovery rates and the relative standard deviation were 88.7??93.5% and 2.8??7.2% in water.     

Characterization of PM10 atmospheric aerosol at urban and urban background sites in Fuzhou city, China

Background

PM₁₀ aerosol samples were simultaneously collected at two urban and one urban background sites in Fuzhou city during two sampling campaigns in summer and winter. PM₁₀ mass concentrations and chemical compositions were determined.

Methods

Water-soluble inorganic ions (Cl^?, NO ₃ ^? , SO ₄ ^2? , NH ₄ ⁺ , K⁺, Na⁺, Ca²⁺, and Mg²⁺), carbonaceous species (elemental carbon and organic carbon), and elements (Al, Si, Mg, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, and Pb) were detected using ion chromatography, thermal/optical reflectance, and proton-induced X-ray emission methods, respectively.

Results

PM₁₀ mass concentrations, as well as most of the chemical components, were significantly increased from urban background to urban sites, which were due to enhanced anthropogenic activities in urban areas. Elements, carbonaceous species, and most of the ions were more uniformly distributed at different types of sites in winter, whereas secondary ion SO ₄ ^2? , NO ₃ ^? , and NH ₄ ⁺ showed more evident urban-background contrast in this season. The chemical mass closure indicated that mineral dust, organic matters, and sulfate were the most abundant components in PM₁₀. The sum of individually measured components accounted for 86.9?C97.7% of the total measured PM₁₀ concentration, and the discrepancy was larger in urban area than in urban background area.

Conclusion

According to the principal component analysis?Cmultivariate linear regression model, mineral dust, secondary inorganic ions, sea salt, and motor vehicle were mainly responsible for the PM₁₀ particles in Fuzhou atmosphere, and contributed 19.9%, 53.3%, 21.3%, and 5.5% of PM₁₀, respectively.     

Exploratory data analysis in the study of 7Be present in atmospheric aerosols

Purpose

Exploratory data analysis (EDA) is applied in this research to study the behavior of radioactive aerosols present in the surface atmosphere of Granada, using ⁷Be as radiotracer. The reason for this study is to reduce the large number of parameters involved in understanding their behavior, given the complexity of the atmosphere.

Methods

Aerosol particles were collected weekly in Granada (Spain) over a 5-year period. Low-background gamma spectrometry was used to determine concentrations of ⁷Be-aerosol activity. The variables studied were: ⁷Be concentration, cosmic ray intensity, temperature, temperature interval, rainfall, relative humidity, and Saharan intrusions. Least significant difference test (LSD), hierarchical cluster analysis (HCA), and principal component analysis (PCA) with varimax rotation have been applied to study the datasets.

Results and discussion

The results of our study reveal that aerosol behavior is represented by two principal components which explain 86.23?% of total variance. Components PC1 and PC2 respectively explain 74.61 and 11.62?% of total variance. PC1 explains the cyclical and seasonal pattern of the samples, while PC2 is related to the production of ⁷Be. In addition, PCA and HCA show good distribution of the samples by families with two groups, summer and winter, at the extremes and spring?Cautumn in the middle. This result corroborates that there are no differences between spring and autumn in the climate of Granada.

Conclusions

EDA has been found to be quite useful in studying the behavior of radioactive aerosols in the surface atmosphere of a city with the climate and geographical characteristics of Granada.     

Study of TiO2 anatase nano and microstructures with dominant {001} facets for NO oxidation

Introduction

TiO₂ anatase nanoplates and hollow microspheres were fabricated by a solvothermal?Chydrothermal method using titanium isopropoxide as a titanium precursor and hydrofluoric acid as a capping agent in order to enhance the formation of the {001} crystal facets of the anatase nanocrystals.

Methods

These different morphological structures of TiO₂ anatase can be achieved by only changing the solvent, keeping the amount of the precursor and of the capping agent identical during the solvothermal?Chydrothermal process.

Results and discussion

After calcination of the samples, the adsorbed fluoride atoms on the {001} crystal facets of the TiO₂ anatase nanocrystals were completely removed from their surface according to XPS analysis. The calcined TiO₂ anatase structures were higher crystallized and the specific surface area of the catalysts increased, enhancing their photocatalytic activity in comparison to the non-calcined TiO₂ anatase structures. All TiO₂ anatase samples with adsorbed as well as non-adsorbed fluoride atoms on their {001} crystal facets, exhibited a higher photonic efficiency than Degussa P25, which was used as a reference.

Conclusion

The fluoride free TiO₂ anatase nanoplates exhibited the best photocatalytic activity in oxidizing the NO gas to NO₂ and NO₃ ^?.     

Potential source apportionment of polycyclic aromatic hydrocarbons in surface sediments from the middle and lower reaches of the Yellow River,China

In this work, principal component analysis/multiple linear regression (PCA/MLR), positive matrix factorization (PMF), and UNMIX model were employed to apportion potential sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments from middle and lower reaches of the Yellow River, based on the measured PAHs concentrations in sediments collected from 22 sites in November 2005. The results suggested that pyrogenic sources were major sources of PAHs. Further analysis indicated that source contributions of PAHs compared well among PCA/MLR, PMF, and UNMIX. Vehicles contributed 25.1–36.7 %, coal 34.0–41.6 %, and biomass burning and coke oven 29.2–33.2 % of the total PAHs, respectively. Coal combustion and traffic-related pollution contributed approximately 70 % of anthropogenic PAHs to sediments, which demonstrated that energy consumption was a predominant factor of PAH pollution in middle and lower reaches of the Yellow River. In addition, the distributions of contribution for each identified source category were studied, which showed similar distributed patterns for each source category among the sampling sites.     

Identification of haze-creating sources from fine particulate matter in Dhaka aerosol using carbon fractions

Fine particulate matter (PM_2.5) samples were simultaneously collected on Teflon and quartz filters between February 2010 and February 2011 at an urban monitoring site (CAMS2) in Dhaka, Bangladesh. The samples were collected using AirMetrics MiniVol samplers. The samples on Teflon filters were analyzed for their elemental composition by PIXE and PESA. Particulate carbon on quartz filters was analyzed using the IMPROVE thermal optical reflectance (TOR) method that divides carbon into four organic carbons (OC), pyrolized organic carbon (OP), and three elemental carbon (EC) fractions. The data were analyzed by positive matrix factorization using the PMF2 program. Initially, only total OC and total EC were included in the analysis and five sources, including road dust, sea salt and Zn, soil dust, motor vehicles, and brick kilns, were obtained. In the second analysis, the eight carbon fractions (OC1, OC2, OC3, OC4, OP, EC1, EC2, EC3) were included in order to ascertain whether additional source information could be extracted from the data. In this case, it is possible to identify more sources than with only total OC and EC. The motor vehicle source was separated into gasoline and diesel emissions and a fugitive Pb source was identified. Brick kilns contribute 7.9 μg/m³ and 6.0 μg/m³ of OC and EC, respectively, to the fine particulate matter based on the two results. From the estimated mass extinction coefficients and the apportioned source contributions, soil dust, brick kiln, diesel, gasoline, and the Pb sources were found to contribute most strongly to visibility degradation, particularly in the winter.

Implications: Fine particle concentrations in Dhaka, Bangladesh, are very high and cause significant degradation of urban visibility. This work shows that using carbon fraction data from the IMPROVE OC/EC protocol provides improved source apportionment. Soil dust, brick kiln, diesel, gasoline, and the Pb sources contribute strongly to haze, particularly in the winter.     

Impacts of urbanization on surface sediment quality: evidence from polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) contaminations in the Grand Canal of China

Introduction

Organic pollutants, especially synthetic organic compounds, can indicate paces of anthropogenic activities. Effects of urbanization on polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) distributions in surface sediment were conducted in urban sections of the Grand Canal, China, consisting of a four-level urbanization gradient.

Materials and methods

The four-level urbanization gradients include three countryside towns, two small-size cities, three medium-size cities, and a large-size city. Diagnostic ratio analysis and factor analysis?Cmultiple linear regression model were used for source apportionment of PAHs. Sediment quality guidelines (SQGs) of USA and Canada were employed to assess ecological risks of PAHs and PCBs in surface sediments of the Canal.

Results and discussion

Ranges of PAH and PCB concentrations in surface sediments were 0.66?C22?mg/kg and 0.5?C93???g/kg, respectively. Coal-related sources were primary PAH sources and followed by vehicular emission. Total concentration, composition, and source apportionment of PAHs exhibited urbanization gradient effects. Total PCB concentrations increased with the urbanization gradient, while total PAHs concentration in surface sediments presented an inverted U Kuznets curve with the urbanization gradient. Elevated concentrations of both PAHs and PCBs ranged at effect range low levels or interim SQG, assessed by USA and Canadian SQGs.

Conclusions

PAHs and PCBs in surface sediments of the Grand Canal showed urbanization gradient effects and low ecological risks.     

Improvement of biodegradability of PVA-containing wastewater by ionizing radiation pretreatment

Background

Polyvinyl alcohol (PVA) has been widely used as sizing agents in textile and manufacturing industry, and it is a refractory compound with low biodegradability.

Objective

The objective of this paper was to treat the PVA-containing wastewater using gamma irradiation as a pretreatment strategy to improve its biodegradability and to determine the roles of different kinds of radical species played during pretreatment.

Methods

Gamma radiation was carried out in a ⁶⁰Cobalt source station, PVA concentration was analyzed by using a visible spectrophotometer and specific oxygen uptake rate (SOUR, milligram of O₂ per gram of mixed liquor volatile suspended solids (MLVSS) per hour) was measured by a microrespirometer.

Results

The results showed that the biodegradability of PVA-containing wastewater with low initial concentration (e.g., 327.8?mg/l) could be improved greatly with increasing irradiation dose. However, PVA gel formation was observed at higher initial PVA concentration (e.g., 3,341.6?mg/l) and higher irradiation dose, which inhibited PVA degradation by aerobic microorganisms. However, the formed gel could be separated by microfiltration, which led to more than 90% total organic carbon (TOC) removal.

Conclusion

Ionizing radiation could be used as a pretreatment technology for PVA-containing wastewater, and its combination with biological process is feasible.