Particle-bound Dechlorane Plus and polybrominated diphenyl ethers in ambient air around Shanghai, China

In present study, atmospheric particles from Shanghai, the biggest city and the most important industrial base in China, were analyzed for polybrominated diphenyl ethers (PBDEs) and Dechlorane Plus (DP). Concentrations of ∑(20)PBDEs and DP both exhibited the changing trend of industrial area > urban areas. Jiading District had the highest levels of particulate PBDEs and DP with values of 744 ± 152 pg/m(3) and 5.48 ± 1.28 pg/m(3), respectively. Compared with similar data in other areas of the world, PBDEs in Shanghai were at medium pollution level, while DP was at lower level, which reflected their different production and use in Shanghai. The results from multiple linear regression analysis suggested that deca-BDE mixture was the most important contributor of particulate PBDEs in Shanghai. The fractions of anti-DP showed no significant differences to those of the technical mixtures (p > 0.05), which suggested that no obviously stereoselective process occurred in ambient air around Shanghai.     

Sampling of nitrates in ambient air

Methods for the measurement of nitric acid, particulate nitrate and total inorganic nitrate (i.e. HNO₃ plus particulate nitrate) are compared using atmospheric samples from the Los Angeles Basin. Nitric acid was measured by (1) the nitrate collected on nylon or NaCl-impregnated cellulose filters after removal of particulate matter with Teflon prefilters, (2) long-path Fourier transform infrared spectroscopy (FTIR) performed by a collaborating investigator, and (3) the difference between total inorganic nitrate (TIN) and particulate nitrate (PN). TIN was measured by the sum of the nitrate collected with a Teflon prefilter and nylon or NaCl-impregnated after-filter. PN was measured by the nitrate able to penetrate a diffusion dénuder coated to remove acidic gases (e.g. HNO₃). Losses of nitrate from Teflon prefilters were determined by comparing the nitrate retained by these filters to the nitrate penetrating the acid gas denuder. TIN and the nitrate collected with glass fiber filters were compared to assess the origin of the artifact particulate nitrate on the latter.Nitric acid measurements using nylon or NaCl-impregnated after-filters were substantially higher than those by the difference technique. This correlated with losses of nitrate from the Teflon prefilters, which exceeded 50 % at high ambient temperature and low relative humidity. Nitric acid by the difference method exceeded that by FTIR by, on average, 20 %. Thus errors inferred in HNO₃ measurements by comparison to the difference measurements are considered minimum values. The high values for HNO₃ by the difference method are consistent with the partial loss of PN in the acid gas denuder. However, no loss of 0.1 μm to 3 μm diameter NH₄NO₃ particles was observed. Thus, if significant, such loss is restricted to coarse particulate nitrate. Heating the filter samplers was shown to increase sampling errors. Nitrate results obtained in short-term, low volume sampling with Gelman A glass fiber filters approximated those with the TIN samplers. Accordingly, these glass fiber filters retained essentially all the gaseous nitric acid sampled.     

fluoride concentrations in the ambient air

The body of the information presented in this paper is of general interest to those concerned with air quality. This paper reports data for ambient atmospheric concentrations of water-soluble fluorides determined in samples of suspended particulate matter collected on glass-fiber filters by the National Air Surveillance Network. Data for over 12,000 samples collected in calendar years 1966, 1967, and 1968 are examined. The purpose of the examination of the data is to give an estimation of current air quality with respect to fluoride content.

The samples are extracted with pure boiling water, and the fluoride concentration of the extracts measured using a fluoride-ion selective electrode. The data engendered are tabulated on an annual basis, and a table is presented summarizing the results. Comparative data will be presented showing the distribution of urban and non-urban stations that exhibit various specified fluoride levels. The results show that the fluoride content in the majority of the samples is below the minimum detectable amount of 0.05 µgF/m³. Conclusions that can be drawn include the observations that: few of the urban samples contain over 1.00 µg/m ³ of fluoride, very few of all samples exceeded 1.00 µ/m³ of fluoride, and no non-urban sample contained over 0.16 µg/m³ of fluoride. It was also concluded that only in rare instances would the fluoride concentrations at the sites sampled be in excess of published standards.     

Air toxics in ambient air of Delhi

Volatile organic compounds (VOCs) are major group of air pollutants which play critical role in atmospheric chemistry. It contributes to toxic oxidants which are harmful to ecosystem human health and atmosphere. Data on levels of VOCs in developing countries is lacking. In India information at target VOCs as defined in USEPA compendium method TO-14 is almost totally lacking. The present work deals with estimation of target VOCs at 15 locations in five categories namely residential, industrial, commercial, traffic intersections and petrol refueling stations in Delhi, the capital of India. The monitoring was carried out during peak hours in morning and evening each month for a year in 2001. Ambient air was adsorbed on adsorbent tubes, thermally desorbed and analyzed on GC–MS. The results show that levels of VOCs are high and stress the need for regular monitoring programme of VOCs in urban environment.     

An investigation into the acid content of aerosols in the ambient air at the Taj Mahal, Agra

A chemical analysis of suspended particulate matter (SPM) collected near the world famous Taj Mahal monument at Agra has been carried out. SPM samples collected on glass fibre filters were analysed for water-soluble sulphate, nitrate, chloride and ammonium ions. The data were derived from over 200 samples (each of 24 h), collected continuously during the winter periods (October through to March) of 1984-1985 and 1985-1986. The SO(4)(2-) and NO(3)(-) components are acidic in nature causing corrosion and effects on visibility, and so were studied in more detail. Mean values for SO(4)(2-) and NO(3)(-) derived from two-year data are 7.2 microg m(-3) and 8.2 microg m(-3), respectively. The SO(4)(2-)/SO(2) and NO(3)(-)/NO(2) ratiosobserved indicate faster conversion of SO(2) to SO(4)(2-) than NO(2) to NO(3)(-), the maximum levels being in January. Thus, both SO(4)(2-) and NO(3)(-) results appear to offer more promising indices of air quality than do SPM data alone.     

Measurement of phase-distributed nitrophenols in Rome ambient air

Atmospheric nitrophenols (NPs) were determined both in the gas and particle phases by combining the annular denuder sampling technique with GC-MS analysis. The phase distribution of six mono-NPs identified in air sampled in downtown Rome was assessed. 4-NP, 3-methyl-4-NP and 2,6-dimethyl-4-NP were found for more than 75% in the particle phase, whilst 2-NP, 4-methyl-2-NP and 5-methyl-2-NP predominated in the gas phase. Concentration levels lower than 20 ng m-3 were observed for all NPs, among which 4-NP (17.8+/-5.6 ng m-3) and 2-NP (10.4+/-4.2 ng m-3) were the most abundant congeners in the two phases, respectively.     

Speciated mercury in size-fractionated particles in Shanghai ambient air

Size-fractionated particles were collected at two sites from July 2004 to April 2006 in Shanghai. The mercury in particles was extracted and divided operationally into four species: exchangeable particulate mercury (EXPM), HCl-soluble particulate mercury (HPM), elemental particulate mercury (EPM) and residual particulate mercury. The total particulate Hg concentration during the study period ranged from 0.07 ng m^?3 to 1.45 ng m^?3 with the average 0.56 ± 0.22 ng m^?3 at site 1, while 0.20 ng m^?3–0.47 ng m^?3 with the average 0.33 ± 0.09 ng m^?3 at site 2, which is far higher than some foreign cities and comparable to some cities with heavy air pollution in China. The Hg mass content also displayed evident size distribution, with higher value in PM_1.6–3.7, somewhat higher or lower than the source profile. EXAM was only found in the summer, HPM have higher percentage in summer and fall rather than in winter and spring. The different mercury species showed different correlation to temperature, relative humidity, wind speed. HPM positively depends on temperature at both sites which implies the importance of mercury transformation on particles. In foggy days TPM increased greatly, but HPM didn't vary greatly as anticipated. Instead, RPM gained a distinguished increase. It demonstrated that aqueous reaction and complex heterogenic reactions in droplet might happen in acidic environment. The correlation of mercury with other pollutants including SO₂, NO₂, CO and PM₁₀ varies with the different mercury forms. Hybrid single-particle lagrangian integrated trajectories (HYSPLIT) model was used to back trace air mass at different representative days and results indicated that transportation from Huabei Plain will increase mercury concentration in winter and fall to some extent. The possible existing compounds and their atmospheric behavior of HPM, EPM and RPM were calculated and the compared to analyze its implication on atmospheric mercury cycle.     

National review of ambient air toxics observations

Ambient air observations of hazardous air pollutant (HAPs), also known as air toxics, derived from routine monitoring networks operated by states, local agencies, and tribes (SLTs), are analyzed to characterize national concentrations and risk across the nation for a representative subset of the 187 designated HAPs. Observations from the National Air Toxics Trend Sites (NATTS) network of 27 stations located in most major urban areas of the contiguous United States have provided a consistent record of HAPs that have been identified as posing the greatest risk since 2003 and have also captured similar concentration patterns of nearly 300 sites operated by SLTs. Relatively high concentration volatile organic compounds (VOCs) such as benzene, formaldehyde, and toluene exhibit the highest annual average concentration levels, typically ranging from 1 to 5 µg/m³. Halogenated (except for methylene chloride) and semivolatile organic compounds (SVOCs) and metals exhibit concentrations typically 2–3 orders of magnitude lower. Formaldehyde is the highest national risk driver based on estimated cancer risk and, nationally, has not exhibited significant changes in concentration, likely associated with the large pool of natural isoprene and formaldehyde emissions. Benzene, toluene, ethylbenzene, and 1,3-butadiene are ubiquitous VOC HAPs with large mobile source contributions that continue to exhibit declining concentrations over the last decade. Common chlorinated organic compounds such as ethylene dichloride and methylene chloride exhibit increasing concentrations. The variety of physical and chemical attributes and measurement technologies across 187 HAPs result in a broad range of method detection limits (MDLs) and cancer risk thresholds that challenge confidence in risk results for low concentration HAPs with MDLs near or greater than risk thresholds. From a national monitoring network perspective, the ability of the HAPs observational database to characterize the multiple pollutant and spatial scale patterns influencing exposure is severely limited and positioned to benefit by leveraging a variety of emerging measurement technologies.

Implications:?Ambient air toxics observation networks have limited ability to characterize the broad suite of hazardous air pollutants (HAPs) that affect exposures across multiple spatial scales. While our networks are best suited to capture major urban-scale signals of ubiquitous volatile organic compound HAPs, incorporation of sensing technologies that address regional and local-scale exposures should be pursued to address major gaps in spatial resolution. Caution should be exercised in interpreting HAPs observations based on data proximity to minimum detection limit and risk thresholds.     

Characterization of size-fractionated particulate mercury in Shanghai ambient air

The size-fractionated particulate mercury in ambient air was collected at the top of a university campus building in Shanghai from March 2002 to September 2003. Wet digestion followed by cold vapor atom adsorption spectroscopy (CVAAS) was employed to analyze total particulate mercury concentration. Two-step extraction was performed to differentiate volatile particle-phase mercury (VPM), reactive particle-phase mercury (RPM) and inert particle-phase mercury (IPM). The average concentrations of mercury in PM_1.6, PM₈ and total suspended particle (TSP) were 0.058–0.252, 0.148–0.398 and 0.233–0.529 ng m⁻³, respectively. About 50%–60% of mercury in PM₈ was in PM_1.6, and about 60%–70% of mercury in TSP was in PM₈. Particulate mercury was mainly concentrated on fine particles. The mercury fraction in fine particulate matters (<1.6 μm) was over 4 μg g⁻¹ while 1–2 μg g⁻¹ in TSP. Both were much higher than background values, suggesting that anthropogenic sources are the predominant emission contributors. Seasonal variation indicated that the mercury in TSP in spring was higher than that in summer; however, the mercury in fine particles (<1.6 μm) varied little. The fact that fine particulate mercury (<1.6 μm) was well correlated with sulfate and elemental carbon, but not with fluoride, chloride, nitrate and organic carbon, demonstrates that fine particulate mercury is closely associated with stationary sources and gas–particle transformation. Speciation analysis of mercury showed that VPM fraction decreased with the decrease of particle size, while IPM fraction increased and occupied over 50% in particle <1.6 μm. The detailed species in VPM, RPM and IPM were discussed. Coal burning was estimated to contribute approximately 80% of total atmospheric mercury.     

Effect of fireworks on ambient air quality in Malta

Religious festivals (festas) in the densely populated Maltese archipelago (Central Mediterranean) are ubiquitous during summer when 86 of them are celebrated between June and October, each involving the burning of fireworks both in ground and aerial displays over a period of 3 days or longer per festival. We assessed the effect of fireworks on the air quality by comparing PM₁₀ and its content of Al, Ba, Cu, Sr and Sb which materials are used in pyrotechnic compositions. PM₁₀ was collected mainly from two sites, one in Malta (an urban background site) and the other in Gozo (a rural site) during July–August 2005 when 59 feasts were celebrated and September–October 2005 when only 11 feasts occurred. For both Malta and Gozo, PM₁₀ and metal concentration levels measured as weekly means were significantly higher during July–August compared to September–October and there exist strong correlations between PM₁₀ and total metal content. Additionally, for Malta dust, Al, Ba, Cu and Sr correlated strongly with each other and also with total concentration of all five metals. The same parameters measured in April 2006 in Malta were at levels similar to those found in the previous October. Ba and Sb in dust from the urban background site in Malta during July–August were at comparable or higher concentration than recently reported values in PM₁₀ from a heavily-trafficked London road and this suggests that these metals are locally not dominated by sources from roadside materials such as break liner wear but more likely by particulate waste from fireworks. Our findings point to the fact that festa firework displays contribute significantly and for a prolonged period every year to airborne dust in Malta where PM₁₀ is an intractable air quality concern. The presence in this dust of elevated levels of Ba and especially Sb, a possible carcinogen, is of concern to health.     

Polynuclear aromatic compounds in the ambient air of Stockholm

The abundance of 15 polynuclear aromatic compounds (PAC) in the ambient air in Stockholm have been monitored over a period of four years. Correlation was made between the concentrations of PAC and other simultaneously measured parameters.     

Sources of variability in ambient air toxics monitoring data

Under the Clean Air Act Amendments, the United States Environmental Protection Agency is required to regulate emissions of 188 hazardous air pollutants. The EPA, Office of Air Quality Planning and Standards is currently conducting a National-scale Air Toxics Assessment with a goal to identify air toxics which are of greatest concern, in terms of contribution to population inhalation risk. The results will be used to set priorities for the collection of additional air toxics emissions and monitoring data. Expanded ambient air toxics monitoring will take the form of a national air toxics monitoring network. With all monitoring data, however, comes uncertainty in the form of environmental variability (spatial and temporal) and monitoring error (sample collection and laboratory analysis). With this in mind, existing data from the Urban Air Toxics Monitoring Program (UATMP) were analyzed to obtain a general understanding of these sources of variability and then provide recommendations for managing the data uncertainties of a national network. The results indicate that environmental variability, in particular temporal, comprises most of the overall variability observed in the UATMP data. However, at lower ambient levels (on the order of 0.1–0.5 ppbv or lower) environmental variability tends to dissipate and monitoring error takes over, most notably analytical error. Overall, the results suggest that common techniques in ambient air toxics monitoring for carbonyls and volatile organic compounds may satisfy many of the primary objectives of a national air toxics monitoring network.     

Modeling PAH uptake by vegetation from the air using field measurements

We examined PAH uptake by Norway spruce needles following the emergence of new buds in spring 2004–June 2005. Atmospheric PAH concentrations (gaseous phase and particle-bound) were monitored during this period, and PAH concentrations from these three environmental media were then used to calculate deposition and transfer velocities. Benzo(a)pyrene was found almost exclusively associated to particles and thus was used to determine a particle-bound deposition velocity of 10.8 m h^?1. PAHs present in both compartments had net gaseous transfer velocities ranging from negligible values to 75.6 m h^?1 and correlated significantly with log K_OA. The loss velocities thereafter calculated were found to be higher for more volatile PAHs. Using the calculated average atmospheric PAH concentrations and deposition velocities, it was thus possible to model PAH uptake by vegetation through time. We demonstrate that this approach can be used to determine deposition velocities without the use of a surrogate surface. In considering both particulate-bound and gaseous deposition processes this model can be used not only to study air–foliage exchange of semi-volatile organic compounds, but also to illustrate the relative contribution of gaseous deposition and particulate-bound deposition in the overall atmospheric vegetation uptake of semi-volatile organic compounds.     

Detecting improvement in ambient air toxics: An application to ambient benzene measurements in Houston,Texas

Traditional regulatory methods for evaluating air toxics have several limitations. Two common methods rely either on self-reported industrial emissions from the Toxics Release Inventory or a single summary statistic such as the average or arithmetic mean. A novel statistical approach for detecting overall long term improvement in ambient air quality is demonstrated using measurements of the air toxic benzene evaluated over five years in Houston, Texas. Through trends of seven key statistical measures, long term improvements were detected at more monitors than would have been found using traditional methods while lack of improvement is highlighted at other monitors. This new approach includes analysis of high and low end concentrations, as well as central tendency, evaluated at specific air toxic human health risk thresholds.