Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Guangzhou,China

Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was investigated at four locations, namely at Yuancun, Wushan, Haizhu and Changban in Guangzhou City, Guangdong Province. The annual deposition fluxes of tetra- to octa-CDD/Fs (total PCDD/Fs) were found to range from 170 to 3000 (mean 1500) pg m⁻² day⁻¹, and the fluxes of total 2, 3, 7, 8-substituted PCDD/F congeners ranged from 2.1 to 41 (mean 20) pg WHO-TEQ m⁻² day⁻¹ at Wushan. The average deposition fluxes of total 2, 3, 7, 8-substituted PCDD/F congeners in rainy season were found to be 37, 27 and 28 pg WHO-TEQ m⁻² day⁻¹ at Yuancun, Haizhu and Changban, respectively, and the PCDD/F deposition fluxes behaved obviously higher in rainy season than in dry season. Results from regression analysis showed that number of rainy days, the amount of wet precipitation, PCDD/F concentrations in particles and organic carbon content played important roles in the variation of PCDD/F deposition fluxes. Monthly average temperatures change little over the year. Therefore, it only played a minor role in monthly variation of PCDD/F deposition fluxes. Particle deposition fluxes were generally not considered as the factor that could cause the differences in PCDD/F deposition fluxes between rainy and dry season, but were found to be related with PCDD/F deposition fluxes in rainy season or dry season. It was found that the profiles of PCDD/F homologs or congeners in the samples were the same either spatially or temporally, indicating that the PCDD/F emission sources were similar to one another. The similarities in PCDD/F homolog patterns and the differences in deposition fluxes between samples collected from heavy-traffic roadside and nearby residence house roof indicated that vehicle exhaust might be an important source for PCDD/F in Guangzhou. PCDD/F concentrations and profiles of PCDD/F homologs in atmospheric deposition were compared with those in both total suspended particles in air and soils, and conclusions indicated that atmospheric deposition possibly tended to remove lower-chlorinated DD/Fs from air and was one of sources for PCDD/Fs in soils.     

Ambient air quality of two metropolitan cities of Pakistan and its health implications

The present study reports findings on TSP loading in the ambient air of two major cities in Pakistan – Karachi and Islamabad. Data for TSP were collected at one site in Karachi and two in Islamabad between 10 December 1998 and 08 January 1999. This article reports one of the highest TSP loadings recorded so far in any megacity of the world. During the study period, average daily TSP concentrations at the Karachi site ranged from 627 to 938 μg m⁻³ with a mean of 668 μg m⁻³. On four occasions TSP concentrations were >1000 μg m⁻³ (range 1031–1736 μg m⁻³). At the Islamabad sampling site in close proximity to the city's industrial sector, daily TSP concentrations varied in the range of 428–998 μg m⁻³ (mean 691 μg m⁻³). Even at a relatively remote site of the city (Saidpur), TSP loading was high (range 145–448 μg m⁻³; mean 275 μg m⁻³). By virtue of the WHO definition, the 24-h average TSP concentrations in a busy commercial site in Karachi and in the vicinity of an industrial sector in Islamabad were in “exceedance” by a factor of 4–8. At Saidpur, the remote site, the 24-h average TSP loading exceeded the WHO guideline of 120 μg m⁻³ by a factor of 1.2–3.7.     

Dioxins,furans and polycyclic aromatic hydrocarbons emissions from a hospital and cemetery waste incinerator

An experimental campaign was carried out on a hospital and cemetery waste incineration plant in order to assess the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polycyclic aromatic hydrocarbons (PAHs). Raw gases were sampled in the afterburning chamber, using a specifically designed device, after the heat recovery section and at the stack. Samples of slags from the combustion chamber and fly ashes from the bag filter were also collected and analyzed. PCDD/Fs and PAHs concentrations in exhaust gas after the heat exchanger (200–350 °C) decreased in comparison with the values detected in the afterburning chamber. Pollutant mass balance regarding the heat exchanger did not confirm literature findings about the de novo synthesis of PCDD/Fs in the heat exchange process. In spite of a consistent reduction of PCDD/Fs in the flue gas treatment system (from 77% up to 98%), the limit of 0.1 ng ITEQ Nm⁻³ at the stack was not accomplished. PCDD/Fs emission factors for air spanned from 2.3 up to 44 μg ITEQ t⁻¹ of burned waste, whereas those through solid residues (mainly fly ashes) were in the range 41–3700 μg ITEQ t⁻¹. Tests run with cemetery wastes generally showed lower PCDD/F emission factors than those with hospital wastes. PAH total emission factors (91–414 μg kg⁻¹ of burned waste) were in the range of values reported for incineration of municipal and industrial wastes. In spite of the observed release from the scrubber, carcinogenic PAHs concentrations at the stack (0.018–0.5 μg Nm⁻³) were below the Italian limit of 10 μg Nm⁻³.     

Measurements of GEM fluxes and atmospheric mercury concentrations (GEM,RGM and Hgp) from an agricultural field amended with biosolids in Southern Ont., Canada (October 2004–November 2004)

Five weeks of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle bound mercury (Hg^p) concentrations as well as fluxes of GEM were measured at Maryhill, Ontario, Canada above a biosolids amended field. The study occurred during the autumn of 2004 (October–November) to capture the effects of cool weather conditions on the behaviour of mercury in the atmosphere. The initial concentration of total mercury (Hg) in the amended soil was relatively low (0.4 μg g⁻¹±10%).A micrometeorological approach was used to infer the flux of GEM using a continuous two-level sampling system with inlets at 0.40 and 1.25 m above the soil surface to measure the GEM concentration gradient. The required turbulent transfer coefficients were derived from meteorological parameters measured on site. The average GEM flux over the study was 0.1±0.2 ng m⁻² h⁻¹(±one standard deviation). The highest averaged hourly GEM fluxes occurred when the averaged net radiation was highest, although the slight diurnal patterns observed were not statistically significant for the complete flux data series. GEM emission fluxes responded to various local events including the passage of a cold front when the flux increased to 2 ng m⁻² h⁻¹ and during a biosolids application event at an adjacent field when depositional fluxes peaked at −3 ng m⁻² h⁻¹. Three substantial rain events during the study kept the surface soil moisture near field capacity and only slightly increased the GEM flux. Average concentrations of RGM (2.3±3.0 pg m⁻³), Hg^p (3.0±6.2 pg m⁻³) and GEM (1.8±0.2 ng m⁻³) remained relatively constant throughout the study except when specific local events resulted in elevated concentrations. The application of biosolids to an adjacent field produced large increases in Hg^p (25.8 pg m⁻³) and RGM (21.7 pg m⁻³) concentrations only when the wind aligned to impact the experimental equipment. Harvest events (corn) in adjacent fields also corresponded to higher concentrations of GEM and Hg^p but with no elevated peaks in RGM concentrations. Diurnal patterns were not statistically significant for RGM and Hg^p at Maryhill.     

PCDDs/PCDFs in ambient air (<1 fg m−3) – The CTDEP long term sampling (30 d) method

The Connecticut Department of Environmental Protection (CTDEP) commenced monitoring for PCDDs/PCDFs (polychlorinated dibenzodioxins and polychlorinated dibenzofurans) in ambient air in 1987 and adopted the long term (30 d) sampling approach in 1993. The CTDEP method represents the first use of isotopically labeled PCDDs/PCDFs as field surrogates to monitor the behavior of native PCDDs/PCDFs present in actual ambient air samples. This feature first introduced in 1987 was later adopted by US EPA in revisions to sampling methods for PCDDs/PCDFs in ambient air (EPA Method TO9A) as well as development of EPA Reference Method 23 for measurement of PCDDs/PCFDs in stationary source emissions. Results are provided here for a total of twenty-three (23) samples (reported as pairs) representing twelve (12) 30 d sampling events conducted at a site located in metropolitan Hartford CT. Samples were collected in winter months during calendar years 2002–2008. PCDDs/PCDFs concentration data (pg m⁻³) are reported as both congener sums (Cl₄–Cl₈) and 2378-substitued congeners. Total PCDDs/PCDFs concentrations for these twelve (12) sampling events ranged from 0.68 pg m⁻³ (2003) to 4.18 pg m⁻³ (2004) with a mean concentration of 2.04 pg m⁻³.Method performance was monitored through use of collocated samples, in field isotopically labeled compounds, isotopically labeled laboratory applied internal standards and field blank samples. Method performance consistently exceeded goals established in USEPA Method TO9A for these same parameters. Average recoveries of in field labeled PCDDs/PCDFs ranged from 97.5% to 104.2%. Average (mean) recoveries for each of the ten (10) isotopically labeled internal standards ranged from 77.0% (¹³C-OCDF) to 95.5% (¹³C-2,3,7,8-TCDF). Method precision defined as % RPD data for collocated sampler pairs ranged from 8% to 14% for PCDDs and from 5% to 12% for PCDFs. The mean RPD for all PCDDs/PCDFs combined is 9.6%. Field monitoring results demonstrate method sensitivity for all PCDDs/PCDFs congeners and 2378-substituted congeners to be well below concentrations typically found for these compounds in ambient air (all reported data represent measured concentrations). Quantities (pg) found in field blanks represent the major determinant to achieving further enhancements in method sensitivity for selected congeners (OCDD < 42 fg m⁻³; 1,2,3,4,6,7,8-HpCDD < 5.7 fg m⁻³; and 1,2,3,4,6,7,8-HpCDF < 2.1 fg m⁻³). The CTDEP method represents a highly sensitive and reliable technique for monitoring of PCDDs/PCDFs congeners and other persistent organic pollutants (POPs) at ultra trace levels in ambient air (fg m⁻³).     

Polycyclic aromatic hydrocarbons in Costa Rican air and soil: A tropical/temperate comparison

Surface soil and passive air samples from a network of 23 sampling sites across Costa Rica were analyzed for polycyclic aromatic hydrocarbons (PAHs), allowing for an evaluation of absolute levels, spatial distribution patterns, air/soil concentration (A/S) ratios and relative composition. Annual mean concentrations of four-ring PAHs in air were low (median of approximately 40 pg m⁻³), except in Costa Rica's densely populated central valley (approximately 650 pg m⁻³). PAH concentrations in soil were also low (median of 5 ng g⁻¹ dry weight) and comparable to those reported for other tropical regions. These low soil concentrations result in A/S ratios of four-ring PAHs in Costa Rica that are higher than the equilibrium air–soil partitioning coefficients and also higher than A/S ratios reported for temperate locations. A series of model calculations of increasing complexity were used to seek an explanation for variable A/S ratios of PAHs under tropical and temperate conditions. Temperature-driven changes in air–soil partitioning and differences in PAH degradability under temperate and tropical conditions are insufficient to explain the higher soil concentrations and lower A/S ratios in temperate regions. However, these can be explained by atmospheric deposition of PAHs during historical periods of much higher emissions and air concentrations and by persistence of PAHs in soils on the order of decades. Low PAH concentrations in tropical soils were found to be consistent with constant or increasing emissions, and in particular, do not require that degradation rates in soil are much faster than in temperate areas. In comparison to temperate soils, soils from Costa Rica and other tropical regions have a higher relative abundance of the lighter PAHs. This likely reflects a higher source contribution from biomass burning in the tropics, as well as the preferential loss of lighter PAHs from temperate soils that experienced high PAH deposition in the past.     

Laboratory studies on the uptake of aromatic hydrocarbons by ice crystals during vapor depositional crystal growth

Uptake of aromatic hydrocarbons (AH) by ice crystals during vapor deposit growth was investigated in a walk-in cold chamber at temperatures of 242, 251, and 260 K, respectively. Ice crystals were grown from ambient air in the presence of gaseous AH namely: benzene (C₆H₆), toluene (methylbenzene, C₇H₈), the C₈H₁₀ isomers ethylbenzene, o-, m-, p-xylene (dimethylbenzenes), the C₉H₁₂ isomers n-propylbenzene, 4-ethyltoluene, 1,3,5-trimethylbenzene (1,3,5-TMB), 1,2,4-trimethylbenzene (1,2,4-TMB), 1,2,3-trimethylbenzene (1,2,3-TMB), and the C₁₀H₁₄ compound tert.-butylbenzene. Gas-phase concentrations calculated at 295 K were 10.3–20.8 μg m⁻³. Uptake of AH was detected by analyzing vapor deposited ice with a very sensitive method composed of solid-phase micro-extraction (SPME), followed by gas chromatography/mass spectrometry (GC/MS).Ice crystal size was lower than 1 cm. At water vapor extents of 5.8, 6.0 and 8.1 g m⁻³, ice crystal shape changed with decreasing temperatures from a column at a temperature of 260 K, to a plate at 251 K, and to a dendrite at 242 K. Experimentally observed ice growth rates were between 3.3 and 13.3×10⁻³ g s⁻¹ m⁻² and decreased at lower temperatures and lower value of water vapor concentration. Predicted growth rates were mostly slightly higher.Benzene, toluene, ethylbenzene, and xylenes (BTEX) were not detected in ice above their detection limits (DLs) of 25 pg g_ice⁻¹ (toluene, ethylbenzene, xylenes) and 125 pg g_ice⁻¹ (benzene) over the entire temperature range. Median concentrations of n-propylbenzene, 4-ethyltoluene, 1,3,5-TMB, tert.-butylbenzene, 1,2,4-TMB, and 1,2,3-TMB were between 4 and 176 pg g_ice⁻¹ at gas concentrations of 10.3–10.7 μg m⁻³ calculated at 295 K. Uptake coefficients (K) defined as the product of concentration of AH in ice and density of ice related to the product of their concentration in the gas phase and ice mass varied between 0.40 and 10.23. K increased with decreasing temperatures. Values of Gibbs energy (ΔG) were between −4.5 and 2.4 kJ mol⁻¹ and decreased as temperatures were lowered. From the uptake experiments, the uptake enthalpy (ΔH) could be determined between −70.6 and −33.9 kJ mol⁻¹. The uptake entropy (ΔS) was between −281.3 and −126.8 J mol⁻¹ K⁻¹. Values of ΔH and ΔS were rather similar for 4-ethlytoluene, 1,3,5-TMB and tert.-butylbenzene, whereas 1,2,3-TMB showed much higher values.     

Particulate matter in the indoor air of classrooms—exploratory results from Munich and surrounding area

Numerous epidemiological studies have demonstrated the association between particle mass (PM) concentration in outside air and the occurrence of health related problems and/or diseases. However, much less is known about indoor PM concentrations and associated health risks. In particular, data are needed on air quality in schools, since children are assumed to be more vulnerable to health hazards and spend a large part of their time in classrooms.On this background, we evaluated indoor air quality in 64 schools in the city of Munich and a neighbouring district outside the city boundary. In winter 2004–2005 in 92 classrooms, and in summer 2005 in 75 classrooms, data on indoor air climate parameters (temperature, relative humidity), carbon dioxide (CO₂) and various dust particle fractions (PM₁₀, PM_2.5) were collected; for the latter both gravimetrical and continuous measurements by laser aerosol spectrometer (LAS) were implemented. In the summer period, the particle number concentration (PNC), was determined using a scanning mobility particle sizer (SMPS). Additionally, data on room and building characteristics were collected by use of a standardized form. Only data collected during teaching hours were considered in analysis. For continuously measured parameters the daily median was used to describe the exposure level in a classroom.The median indoor CO₂ concentration in a classroom was 1603 ppm in winter and 405 ppm in summer. With LAS in winter, median PM concentrations of 19.8 μg m⁻³ (PM_2.5) and 91.5 μg m⁻³ (PM₁₀) were observed, in summer PM concentrations were significantly reduced (median PM_2.5=12.7 μg m⁻³, median PM₁₀=64.9 μg m⁻³). PM_2.5 concentrations determined by the gravimetric method were in general higher (median in winter: 36.7 μg m⁻³, median in summer: 20.2 μg m⁻³) but correlated strongly with the LAS-measured results. In explorative analysis, we identified a significant increase of LAS-measured PM_2.5 by 1.7 μg m⁻³ per increase in humidity by 10%, by 0.5 μg m⁻³ per increase in CO₂ indoor concentration by 100 ppm, and a decrease by 2.8 μg m⁻³ in 5–7th grade classes and by 7.3 μg m⁻³ in class 8–11 compared to 1–4th class. During the winter period, the associations were stronger regarding class level, reverse regarding humidity (a decrease by 6.4 μg m⁻³ per increase in 10% humidity) and absent regarding CO₂ indoor concentration. The median PNC measured in 36 classrooms ranged between 2622 and 12,145 particles cm⁻³ (median: 5660 particles cm⁻³).The results clearly show that exposure to particulate matter in school is high. The increased PM concentrations in winter and their correlation with high CO₂ concentrations indicate that inadequate ventilation plays a major role in the establishment of poor indoor air quality. Additionally, the increased PM concentration in low level classes and in rooms with high number of pupils suggest that the physical activity of pupils, which is assumed to be more pronounced in younger children, contributes to a constant process of resuspension of sedimented particles. Further investigations are necessary to increase knowledge on predictors of PM concentration, to assess the toxic potential of indoor particles and to develop and test strategies how to ensure improved indoor air quality in schools.     

Dietary intake of PCDD/Fs and dioxin-like PCBs from the Chinese total diet study in 2007

Concentrations of 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and 12 dioxin-like polychlorinated biphenyls (dl-PCBs) were measured in 96 food composite samples from eight varieties of food groups from the Chinese total diet study (TDS) in 2007. The concentrations of samples, expressed as WHO toxic equivalents (TEQ), ranged from 0.001 pg TEQ g^?1 to 0.85 pg TEQ g^?1 (fresh weight). Dietary intake of PCDD/Fs and dl-PCBs of 12 age/gender subgroups of the Chinese population subsequently estimated ranges from 15.4 pg TEQ kg^?1 bw month^?1 to 38.7 pg TEQ kg^?1 bw month^?1 for average population and from 68.5 pg TEQ kg^?1 bw month^?1 to 226.1 pg TEQ kg^?1 bw month^?1 for high consumers (the 97.5th percentile). Dietary exposure of children (mean: 32.5 pg TEQ kg^?1 bw month^?1) is significantly higher than that of the adults (mean: 21.5 pg TEQ kg^?1 bw month^?1) (p < 0.01) presumably due to more food consumed by children relative to their body weight compared to adults. There is no difference of dietary exposure, expressed as pg TEQ kg^?1 bw, found between different genders. Across various regions in China, there are large differences of dietary exposure of adult population and pattern of contribution of food groups to total exposure due to different contamination level and food habits. Dietary exposures of average population of various subgroups were all below the PTMI recommended by JECFA, but those of higher consumers were found exceeding or comparable to the PTMI.     

Spatial variation of mass concentration of roadside suspended particulate matter in metropolitan Hong Kong

This study conducted roadside particulate sampling to measure the total suspended particulate (TSP), PM₁₀ (particles <10 μm in aerodynamic diameter) and PM_2.5 (particles <2.5 μm in aerodynamic diameter) mass concentration in 11 urbanized and densely populated districts in Hong Kong. One hundred and thirty-three samples were obtained to measure the mass concentrations of TSP, PM₁₀ and PM_2.5. According to these results, the TSP, PM₁₀ and PM_2.5 mass concentrations varied from 94.85 to 301.63 μg m⁻³, 67.67 to 142.68 μg m⁻³ and 50.01 to 125.12 μg m⁻³, respectively. The PM_2.5/PM₁₀ ratio of all samples was 0.82 which ranged from 0.62 to 0.95. The PM levels and PM ratios in metropolitan Hong Kong significantly fluctuated from site-to-site and over time. The PM_2.5 mass concentration in different districts corresponding to urban industrial, new town, urban residential and urban commercial were 77.64, 87.50, 106.96 and 88.54 μg m⁻³, respectively. The PM_2.5 level is high in Hong Kong, and for individual sampling, more than 60% daily measurements exceeded the NAAQS. The mass fraction of PM_2.5 in PM₁₀ and TSP is relatively high when compared with overseas studies.     

Polychlorinated biphenyls and particulate organic/elemental carbon in the atmosphere of Chesapeake Bay,USA

Polychlorinated biphenyls (PCBs) and particulate organic/elemental carbon (OC/EC) differ as to sources, but are both elevated in major urban areas leading to loadings of proximate terrestrial and aquatic systems. Because of the dramatic difference in speciation, sources, and sinks of these compunds, gas+particulate phase PCBs and particulate OC/EC were measured in urban Baltimore, MD and over Chesapeake Bay at 4 and 12 h frequencies in July 1997. Gas phase ∑PCBs averaged 1180 pg m⁻³ for Baltimore and 550 pg m⁻³ for northern Chesapeake Bay. PCB homolog distributions in the gas phase differed between the land and over-water sites whereby the trichlorobiphenyls were higher in Baltimore compared to Chesapeake Bay. Autocorrelation analysis yielded a diurnal cycle for gas phase PCBs at Baltimore with the lowest concentrations observed during the day. Particulate organic and elemental carbon constituted 12.4% (17.4% organic matter) and 2.8% of total suspended particles (TSP) in Baltimore, and 15.0% (21.0% organic matter) and 5.3% over the Chesapeake Bay, respectively. Variability in PCB concentrations was not related to the variability in OC/EC concentrations. OC/EC ratios suggest that particulate organic carbon was mostly primary aerosol. Emissions of both classes of compounds into the Baltimore atmosphere and vicinity are major sources to the Bay.     

Survey of polyfluorinated chemicals (PFCs) in the atmosphere over the northeast Atlantic Ocean

High volume air sampling in Bermuda, Sable Island (Nova Scotia) and along a cruise track from the Gulf of Mexico to northeast coast of the USA, was carried out to assess air concentrations, particle-gas partitioning and transport of polyfluorinated chemicals (PFCs) in this region. Samples were collected in the summer of 2007. Targeted compounds included the neutral PFCs: fluorotelomer alcohols (FTOHs), perfluoroalkyl sulfonamides (FOSAs) and perfluoroalkyl sulfonamido ethanols (FOSEs).Among the FTOHs, 8:2 FTOH was dominant in all samples. Sum of the concentration of FTOHs (gas+particle phase) were higher in Bermuda (mean, 34 pg m^?3) compared to Sable Island (mean, 16 pg m^?3). In cruise samples, sum of FTOHs were highly variable (mean, 81 pg m^?3) reflecting contributions from land-based sources in the northeast USA with concentrations reaching as high as 156 pg m^?3.Among the FOSAs and FOSEs, MeFOSE was dominant in all samples. In Bermuda, levels of MeFOSE were exceptionally high (mean, 62 pg m^?3), exceeding the FTOHs. Sable Island samples also exhibited the dominance of MeFOSE but at a lower concentration (mean, 15 pg m^?3). MeFOSE air concentrations (pg m^?3) in cruise samples ranged from 1.6 to 73 and were not linked to land-based sources. In fact high concentrations of MeFOSE observed in Bermuda were associated with air masses that originated over the Atlantic Ocean.The partitioning to particles for 8:2 FTOH, 10:2 FTOH, MeFOSE and EtFOSE ranged from as high as 15 to 42% for cruise samples to 0.9 to 14% in Bermuda. This study provides key information for validating and developing partitioning and transport models for the PFCs.     

Phosphine in the marine atmosphere along a hemispheric course from China to Antarctica

The gas phosphine (PH₃) is a part of an atmospheric link of the phosphorus cycle on earth. Previous research reported the terrestrial lower tropospheric PH₃ at night in the 1 ng m⁻³ range in remote areas, with the peak of 100 ng m⁻³ in populated areas, and at daytime even lower concentrations in the pg m⁻³ range. The data of the global marine atmospheric PH₃ are still very sparse.This study presents surprisingly high concentrations of PH₃ in the order of 0.1–1 μg m⁻³ in many of 32 samples of the marine atmosphere in the latitudinal range from 30°N to 65°S (the cruise of research ship Xuelong from Shanghai Harbor, China, to Antarctica). The highest concentrations were measured near coastal areas of Eastern Asia and Western Australia. A significant correlation exists between marine atmospheric PH₃ concentration and air temperature at 22:00 (local time). PH₃ concentrations at different latitudes strongly decline with daylight intensity according to a logarithmic relationship. These surprisingly high concentrations of the readily oxidizable PH₃ in the air indicate hitherto unknown but important PH₃ emission sources in marine environment. More work is necessary to evaluate the sources of atmospheric PH₃ from marine biosphere.     

Atmospheric distribution of polycyclic aromatic hydrocarbons and deposition to Galveston Bay,Texas, USA

Estimates of the atmospheric deposition to Galveston Bay of polycyclic aromatic hydrocarbons (PAHs) are made using precipitation and meteorological data that were collected continuously from 2 February 1995 to 6 August 1996 at Seabrook, TX, USA. Particulate and vapor phase PAHs in ambient air and particulate and dissolved phases in rain samples were collected and analyzed. More than 95% of atmospheric PAHs were in the vapor phase and about 73% of PAHs in the rain were in the dissolved phase. Phenanthrene and napthalene were the dominant compounds in air vapor and rain dissolved phases, respectively, while 5 and 6 ring PAH were predominant in the particulate phase of both air and rain samples. Total PAH concentrations ranged from 4 to 161 ng m⁻³ in air samples and from 50 to 312 ng l⁻¹ in rain samples. Temporal variability in total PAH air concentrations were observed, with lower concentrations in the spring and fall (4–34 ng m ⁻³) compared to the summer and winter (37–161 ng m⁻³). PAHs in the air near Galveston Bay are derived from both combustion and petroleum vaporization. Gas exchange from the atmosphere to the surface water is estimated to be the major deposition process for PAHs (1211 μg m^{− 2} yr^{− 1}), relative to wet deposition (130 μg m⁻² yr^{− 1}) and dry deposition (99 μg m⁻² yr^{− 1}). Annual deposition of PAHs directly to Galveston Bay from the atmosphere is estimated as 2  t yr⁻¹.     

Atmospheric bulk deposition of dioxin and furans to Danish background areas

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in bulk deposition at three Danish rural forest sites with a mutual maximum distance of 450 km. At one of the forest sites concentrations in the ambient atmosphere were sampled from a 12 m high tower. Sampling was carried out within a period of 3 years with sampling intervals of 1–2 months. Mean bulk deposition fluxes were 1 ng m⁻² yr⁻¹ I-TEQ and deviated less than 30% between the sites. Yearly average PCDD/F concentrations in the atmosphere were 24 fg m⁻³ I-TEQ with maximum values in the winter period. During winter months atmospheric concentrations of PCDD/F and oxidized sulphur compounds showed a positive correlation, furthermore seasonal bulk deposition showed correlation between PCDD/F and sulphate.     

Accumulation of hydroxylated polychlorinated biphenyls (OH-PCBs) and implications for PCBs metabolic capacities in three porpoise species

The present study investigated polychlorinated biphenyls (PCBs) and hydroxylated metabolites of PCBs (OH-PCBs) in blood from three porpoise species: finless porpoises (Neophocaena phocaenoides), harbor porpoises (Phocoena phocoena), and Dall’s porpoises (Phocoenoides dalli). The porpoises were found stranded or were bycaught along the Japanese coast. Concentrations of OH-PCB were the highest in Dall’s porpoises (58 pg g⁻¹ wet wt), second highest in finless porpoises (20 pg g⁻¹ wet wt), and lowest in harbor porpoises (8.3 pg g⁻¹ wet wt). The concentrations in Dall’s porpoises were significantly higher than the concentrations in finless porpoises and harbor porpoises (p < 0.05 and p < 0.01, respectively). There was a positive correlation between PCB and OH-PCB concentrations (r = 0.67, p < 0.001), suggesting the possible concentration-dependent induction of CYP enzymes. The three porpoise species may have exceptionally low metabolic capacities compared with other marine and terrestrial mammals, because low OH-PCB/PCB concentration ratios were found, which were 0.0016 for Dall’s porpoises, 0.0013 for harbor porpoises, and 0.00058 for finless porpoises. Distinct differences in the OH-PCB congener patterns were observed for the three species, even though they are taxonomically closely related.     

Characterization of aerosol over the Northern South China Sea during two cruises in 2003

Atmospheric transport of trace elements has been found to be an important pathway for their input to the ocean. TSP, PM10, and PM2.5 aerosol samples were collected over the Northern South China Sea in two cruises in 2003 to estimate the input of aerosol from continent to the ocean. About 23 elements and 14 soluble ions in aerosol samples were measured. The average mass concentration of TSP in Cruise I in January (78 μg m⁻³) was ∼twice of that in Cruise II in April (37 μg m⁻³). Together with the crustal component, heavy metals from pollution sources over the land (especially from the industry and automobiles in Guangzhou) were transported to and deposited into the ocean. The atmospheric MSA concentrations in PM2.5 (0.048 μg m⁻³ in Cruise I and 0.043 μg m⁻³ in Cruise II) over Northern South China Sea were comparable to those over other coastal regions. The ratio of non-sea-salt (NSS)-sulfate to MSA is 103-655 for Cruise I and 15-440 for Cruise II in PM2.5 samples, which were much higher than those over remote oceans. The estimated anthropogenic sulfate accounts for 83–98% in Cruise I and 63–95% in Cruise II of the total NSS-sulfate. Fe (II) concentration in the aerosols collected over the ocean ranged from 0.1 to 0.9 μg m⁻³, accounting for 16–82% of the total iron in the aerosol, which could affect the marine biogeochemical cycle greatly.     

A comparison of air particulate matter and associated polycyclic aromatic hydrocarbons in some tropical and temperate urban environments

A 12 month study of urban concentrations of total suspended particulates (TSP) and 20 polycyclic aromatic hydrocarbons (PAH) was carried out in Seoul (South Korea), Hong Kong, Bangkok (Thailand), Jakarta (Indonesia) and Melbourne (Australia). Concentrations of particulate matter in the atmosphere varied widely between the cities over the course of the study, ranging from a low of 24.1 μg m⁻³ in Melbourne during the winter to a high of 376.2 μg m⁻³ in Jakarta during the dry season. Seasonal variations in both TSP and PAH were observed in the tropical cities in the study with higher concentrations during the dry season and lower concentrations during the wet season. TSP and PAH concentrations are correlated with each other in these cities, suggesting that they have related sources and sinks for these cities. In the temperate cities of Melbourne and Seoul, PAH concentrations were higher during the cold winter season and lower during the warm summer. However, TSP was quite variable over the years in these latter cities and no clear seasonal trend was observed. A number of factors have been investigated which could be contributing to seasonal variations in pollutant levels. In the temperate climates, increased emissions due to the use of fossil fuels for heating in the winter is evident. However, an interrogation of the database with respect to the other factors such as (1) increased photolytic degradation during the summer, (2) transport of pollutants from other sources, (3) removal of PAH via wet deposition and in-cloud scavenging mechanisms and (4) volatilisation of lower molecular weight species during periods of high temperature indicates the importance of multiple processes. Even though there are clearly much lower levels of both particulates and PAH in the wet season of the tropical climates, no statistically significant correlations have been observed between rainfall levels and pollutant concentrations.     

Source apportionment of secondary organic aerosol during a severe photochemical smog episode

The UCD/CIT air quality model was modified to predict source contributions to secondary organic aerosol (SOA) by expanding the Caltech Atmospheric Chemistry Mechanism to separately track source apportionment information through the chemical reaction system as precursor species react to form condensable products. The model was used to predict source contributions to SOA in Los Angeles from catalyst-equipped gasoline vehicles, non-catalyst equipped gasoline vehicles, diesel vehicles, combustion of high sulfur fuel, other anthropogenic sources, biogenic sources, and initial/boundary conditions during the severe photochemical smog episode that occurred on 9 September 1993. Gasoline engines (catalyst+non-catalyst equipped) were found to be the single-largest anthropogenic source of SOA averaged over the entire model domain. The region-wide 24-h average concentration of SOA produced by gasoline engines was predicted to be 0.34 μg m⁻³ with a maximum 24-h average concentration of 1.81 μg m⁻³ downwind of central Los Angeles. The region-wide 24-h average concentration of SOA produced by diesel engines was predicted to be 0.02 μg m⁻³, with a maximum 24-h average concentration of 0.12 μg m⁻³ downwind of central Los Angeles. Biogenic sources are predicted to produce a region-wide 24-h average SOA value of 0.16 μg m⁻³, with a maximum 24-h average concentration of 1.37 μg m⁻³ in the less-heavily populated regions at the northern and southern edges of the air basin (close to the biogenic emissions sources). SOA concentrations associated with anthropogenic sources were weakly diurnal, with slightly lower concentrations during the day as mixing depth increased. SOA concentrations associated with biogenic sources were strongly diurnal, with higher concentrations of aqueous biogenic SOA at night when relative humidity (RH) peaked and little biogenic SOA formation during the day when RH decreased.