Atmospheric deposition of organochlorine contaminants to Galveston Bay,Texas

Atmospheric monitoring of PCBs and chlorinated pesticides (e.g., HCHs, chlordanes, and DDTs) in Galveston Bay was conducted at Seabrook, Texas. Air and wet deposition samples were collected from 2 February 1995 and continued through 6 August 1996. Vapor total PCB (tPCB) concentrations in air ranged from 0.21 to 4.78 ng m⁻³ with a dominance of tri-chlorinated PCBs. Dissolved tPCBs in rain ranged from 0.08 to 3.34 ng l⁻¹, with tetra-chlorinated PCBs predominating. The predominant isomers found in air and rain were α- and γ-HCH, α- and γ-chlordanes, 4,4′-DDT, and dieldrin. The concentrations of PCBs and pesticides in the air and rain revealed no clear seasonal trend. Elevated levels of PCBs in the air occurred when temperatures were high and wind came from urban and industrialized areas (S, SW, NW, and W of the site). Concentrations of HCHs were elevated in April, May, and October, perhaps due to local and/or regional applications of γ-HCH (lindane). Other pesticides showed no notable temporal variation. When winds originated from the Gulf of Mexico (southeasterly), lower concentrations of organochlorines were detected in the air. The direct deposition rate (wet+dry) of PCBs to Galveston Bay (6.40 μg m⁻² yr⁻¹) was significantly higher than that of pesticides by a factor of 5–10. The net flux from gas exchange estimated for PCBs was from Galveston Bay water to the atmosphere (78 μg m⁻² yr⁻¹). Gas exchange of PCBs from bay water to the atmosphere was the dominant flux.     

Assessment of variations in atmospheric PCDD/Fs by Asian dust in Southeastern Korea

Atmospheric concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were measured in southeastern Korea during the spring of 2002. During this period, severe Asian dust events (ADs) occurred throughout Korea. Total suspended particulates (TSP) of ADs (456.8 μg m⁻³) increased approximately 3.6-fold compared with non-Asian dust events (NADs; 128.5 μg m⁻³). However, the concentrations of PCDD/Fs (average concentration, 3.34 pg m⁻³) did not increase as much as TSP; there was not a significant difference in the concentrations of particle-bound PCDD/Fs collected between ADs (2.45 pg m⁻³) and NADs (2.05 pg m⁻³). Meanwhile, according to TSP levels, the concentrations during NADs were 2.8-fold higher than ADs (16.73 and 5.98 ng g⁻¹-TSP, respectively). High TSP levels during sand storms without an increase in PCDD/Fs reflected an increase in coarse and accumulation mode particles. Gas/particle partitioning studies revealed the additional inputs of particulate matters to the air during ADs which did not relate with the increase of PCDD/Fs. Furthermore, emissions from ADs may consist of relatively complex atmospheric particles; back trajectories showed air masses moving at low altitudes over Korea, but there were no differences in PCDD/Fs or atmospheric pollutants regardless of air movements. The study area, which is located in southeastern Korea, might be affected by both marine and regional anthropogenic sources, which do not appear to cause clear differences in PCDD/F concentrations or congener profiles between different air trajectories.     

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.     

Levels of persistent organic pollutants in air in China and over the Yellow Sea

The occurrence of persistent toxic substances (PTS) in China and possibly their regional transport in the Yellow and East China Seas region was studied. Organochlorines in atmospheric gas-phase and particulate matter were collected by high-volume sampling (filters and polyurethane foams) during 2 weeks in June 2003 (dry season) simultaneously at a Yellow Sea coastal site in an urban area, Qingdao, China, and a rural island site, Gosan, Jeju Island, Korea. Using GC methods, the samples were analysed for 9 persistent organic pollutants (POPs) regulated under the global POP convention, namely aldrin, chlordane (cis- and trans-isomers CC and TC), DDT and metabolites (o,p′-DDT, p,p′-DDD, and p,p′-DDE), dieldrin, endrin, heptachlor, hexachlorobenzene (HCB), mirex and PCB (congeners number 28, 52, 101, 153 and 180), and for hexachlorocyclohexane (α-, β- and γ-isomers), a PTS and now considered for regulation under the convention, too. At the coastal site additionally o,p′-DDE and -DDD, β-endosulfan, isodrin, heptachlorepoxide and δ-HCH, and at the island site additionally p,p′-DDT and 12 additional PCB congeners were analysed. 9 samples were collected at the coastal and 15 (for PCBs 5) at the island site. Long-range advection pathways were determined based on analysed back-trajectory calculations.The mean concentrations of DDT and its metabolites, HCB, HCH, and PCB at the coast were in the 100–1000 pg m⁻³ range. Higher concentrations prevailed during nighttime. The levels were in general lower at the island site, but not for DDT. Local sources are likely. PCBs were even 2 orders of magnitude lower, suggesting that PCBs are not subject to regional transport but elevated concentrations in air are limited to the source areas. Organochlorine pesticide levels on the other hand were seemingly determined by regional transport over Mainland China rather than by emissions in the coastal area. The currently used pesticides mirex and chlordane were found at elevated levels, i.e. 79 (6.6–255) and 36 (<6–71) pg m⁻³, respectively, at the coast but not over the island. The POPs pesticides aldrin, dieldrin and endrin, never registered in China, were mostly found at <10 pg m⁻³ except for endrin at the coastal site (up to 400 pg m⁻³) and aldrin at the island site (up to 50 pg m⁻³).     

High concentrations of persistent organic pollutants including PCBs,DDT, PBDEs and PFOS in little brown bats with white-nose syndrome in New York,USA

White-nose syndrome (WNS) is a condition associated with white fungal growth on ears, wings, and nose of hibernating bats; this condition has recently resulted in high bat mortality in the northeastern United States. Nevertheless, the pathogenesis of morbidity and mortality are still unknown. Elevated exposure to toxic contaminants could be a contributing factor via the consequent immunosuppression and endocrine disruption. In this study, diseased little brown bats (Myotis lucifugus) were collected from several hibernacula in eastern New York State in 2008. Fat tissues of bats were analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), and organochlorine pesticides (OCPs; DDT, chlordanes, HCB, and HCH), and liver was analyzed for perfluorinated compounds (PFCs). A reference population of little brown bats, not affected by WNS, was also collected from a cave in Kentucky for the analysis of trace organic contaminants. Concentration of PCBs in fat tissues of bats from New York ranged from 1900 ng g^?1 to 35 000 ng g^?1, lipid wt, with the highest concentrations found in bats collected from caves in Albany County. High concentrations of PCBs were also found in bats from Kentucky (17 100–18 400 ng g^?1, lipid wt). Total PBDE concentrations in fat tissues ranged from 520 ng g^?1 to 10 900 ng g^?1, lipid wt, in bats from New York and from 4300 ng g^?1 to 13 000 ng g^?1, lipid wt, in bats from Kentucky. High concentrations of DDT (26 900 ng g^?1, lipid wt), chlordanes (6350 ng g^?1, lipid wt), and HCB (260 ng g^?1, lipid wt) were found in bats from New York. Concentrations of hexabromobiphenyl congener 153 (PBB 153) in bats from New York ranged from 8.6 ng g^?1 to 12 4000 ng g^?1, lipid wt. Concentrations of PFCs were on the order of a few tens to a few hundreds of nanograms per gram liver, on a wet weight basis. Overall, high concentrations of PCBs, PBDEs, DDT, and chlordanes were found in fat tissues of diseased bats from New York, although the concentrations in bats from non-diseased, reference population, from Kentucky were also high.     

Reproductive performance in East Greenland polar bears (Ursus maritimus) may be affected by organohalogen contaminants as shown by physiologically-based pharmacokinetic (PBPK) modelling

Polar bears (Ursus maritimus) feed mainly on ringed seal (Phoca hispida) and consume large quantities of blubber and consequently have one of the highest tissue concentrations of organohalogen contaminants (OHCs) worldwide. In East Greenland, studies of OHC time trends and organ system health effects, including reproductive, were conducted during 1990–2006. However, it has been difficult to determine the nature of the effects induced by OHC exposures on wild caught polar bears using body burden data and associated changes in reproductive organs and systems. We therefore conducted a risk quotient (RQ) evaluation to more quantitatively evaluate the effect risk on reproduction (embryotoxicity and teratogenicity) based on the critical body residue (CBR) concept and using a physiologically-based pharmacokinetic (PBPK) model. We applied modelling approaches to PCBs, p,p′-DDE, dieldrin, oxychlordane, HCHs, HCB, PBDEs and PFOS in East Greenland polar bears based on known OHC pharmacokinetics and dynamics in laboratory rats (Rattus rattus). The results showed that subcutaneous adipose tissue concentrations of dieldrin (range: 79–1271 ng g⁻¹ lw) and PCBs (range: 4128–53 923 ng g⁻¹ lw) reported in bears in the year 1990 were in the range to elicit possible adverse health effects on reproduction in polar bears in East Greenland (all RQs ⩾ 1). Similar results were found for PCBs (range: 1928–17 376 ng g⁻¹ lw) and PFOS (range: 104–2840 ng g⁻¹ ww) in the year 2000 and for dieldrin (range: 43–640 ng g⁻¹ lw), PCBs (range: 3491–13 243 ng g⁻¹ lw) and PFOS (range: 1332–6160 ng g⁻¹ ww) in the year 2006. The concentrations of oxychlordane, DDTs, HCB and HCHs in polar bears resulted in RQs < 1 and thus appear less likely to be linked to reproductive effects. Furthermore, sumRQs above 1 suggested risk for OHC additive effects. Thus, previous suggestions of possible adverse health effects in polar bears correlated to OHC exposure are supported by the present study. This study also indicates that PBPK models may be a supportive tool in the evaluation of possible OHC-mediated health effects for Arctic wildlife.     

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.     

Bioaccumulation of polybrominated diphenyl ethers in harbor seals from the northwest Atlantic

Polybrominated diphenyl ethers (PBDEs) were analyzed in blubber of harbor seals (Phoca vitulina concolor) collected between 1991 and 2005 along the northwest Atlantic. ∑PBDE concentrations (mono- to hexa-BDEs) detected in blubber samples (n = 42) ranged from 80 to 25 720 ng g⁻¹ lw, (overall mean 2403 ± 5406 ng g⁻¹ lw). By age, mean ∑PBDE concentrations were: 3645 ± 7388, 2945 ± 5995, 1385 ± 1265, and 326 ± 193 ng g⁻¹ lw in pups, yearlings, adult males, and adult females, respectively. Unlike the trend for PCBs, no decreasing gradient from urban to rural/remote areas was observed for PBDEs in these samples, likely reflecting inputs from local sources. No significant temporal trend was observed for PBDEs in harbor seals between 1991 and 2005, although congener profiles shifted over time. Tetra-BDE-47 was the dominant congener, followed by BDEs-99, -100, -153, -154, and -155 in varying order, suggesting exposure to the penta-BDE product. In adult males, the hexa-BDEs contributed more to the total (22%) than BDEs-99 and -100 (14%), and concentrations of BDE-155 were elevated compared with -154. Higher BDEs were detected in a subset of seals (n = 12) including hepta-BDE-183, the marker for the octa-BDE mixture, and octa-BDE-197, along with several unidentified hepta- and octa- congeners. BDE-209 was detected in seal blubber at concentrations ranging from 1.1 to 8 ng g⁻¹ lw, indicating that deca-BDE is bioavailable in this marine food web. This is the first study to document the accumulation of BDE-209 at measurable levels in wild harbor seals. While the PBDE patterns in blubber indicate exposure to all three BDE commercial mixtures, the data also suggest that BDE-209 debromination by seal prey fish may contribute to the loading of lower brominated congeners (hexa- to octa-BDEs) in these seals.     

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.     

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.     

Measurement of the vapor phase deposition of polychlorinated bipheyls (PCBs) using a water surface sampler

A water surface sampler (WSS) was employed in combination with greased knife-edge surface deposition plates (KSSs) to measure the vapor phase deposition rates of PCBs to the sampler at an urban site, Chicago, IL. This sampler employed a water circulation system that continuously removed deposited PCBs. Total (gas+particle) and particulate PCB fluxes were collected with the WSS and KSSs, respectively. Gas phase PCB fluxes were then calculated by subtracting the KSS fluxes (particulate) from the WSS fluxes (gas+particle). The calculated gas phase PCB fluxes averaged 830±910 ng m⁻²d⁻¹. This flux value is, in general, higher than the fluxes determined using simultaneously measured air–water concentrations in natural waters and is in the absorption direction. This difference is primarily because the PCBs were continuously removed from the WSS water keeping the water PCB concentration near zero.Concurrently, ambient air samples were collected using a modified high volume air sampler. The gas phase PCB concentrations ranged between 1.10 and 4.46 ng m⁻³ (average±SD, 2.29±1.28 ng m⁻³). The gas phase fluxes were divided by the simultaneously measured gas phase ambient concentrations to determine the overall gas phase mass transfer coefficients (MTCs) for PCBs. The average gas phase overall MTCs (K_g) for each homolog group ranged between 0.22 and 1.32 cm s⁻¹ (0.54±0.47 cm s⁻¹). The average MTC was in good agreement with those determined using similar techniques.     

Aerosol scattering properties in northern China

The aerosol scattering properties were investigated at two continental sites in northern China in 2004. Aerosol light scattering coefficient (σ_sp) at 525 nm, PM₁₀, and aerosol mass scattering efficiencies (α) at Dunhuang had a mean value of 165.1±148.8 M m⁻¹, 157.6±270.0 μg m⁻³, and 2.30±3.41 m² g⁻¹, respectively, while these values at Dongsheng were, respectively, 180.2±151.9 M m⁻¹, 119.0±112.9 μg m⁻³, and 1.87±1.41 m² g⁻¹. There existed a seasonal variability of aerosol scattering properties. In spring, at Dunhuang PM₁₀, σ_sp, and α were 184.1±211.548 μg m⁻³, 126.3±89.6 M m⁻¹, and 1.05±0.97 m² g⁻¹, respectively, and these values at Dongsheng were 146.4±142.1 μg m⁻³, 183.4±81.7 M m⁻¹, and 1.98±1.52 m² g⁻¹, respectively. However, in winter at Dunhuang PM₁₀, σ_sp, and α were 158.1±261.4 μg m⁻³, 303.3±165.2 M m⁻¹, and 3.17±1.93 m² g⁻¹, respectively, and these values at Dongsheng were 155.7±170.1 μg m⁻³, 304.4±158.1 M m⁻¹, and 2.90±1.72 m² g⁻¹, respectively. σ_sp and α in winter were higher than that in spring at both the sites, which coincides with the characteristics of dust aerosol and pollution aerosol. Overall, the dominant aerosol types in spring and winter at both sites in northern China are dust aerosol and pollution aerosol, respectively.     

Atmospheric polychlorinated biphenyl concentrations and apparent degradation in coastal New Jersey

To characterize the atmospheric dynamics and behavior of organic compounds in the NY–NJ Harbor Estuary, atmospheric concentrations of polychlorinated biphenyls (PCBs) were measured at coastal, suburban and urban sites in New Jersey in 1997–1999. ∑PCB concentrations at the suburban site varied from 86 to 2300 pg m⁻³ and from 84 to 1100 pg m⁻³ at the coastal site. Although the temporal trends of total concentrations were significantly different at the three sites (p<0.01), PCB congener profiles revealed similar patterns (r²>0.90, p<0.001) implicating a dominant emission type and/or process. Temperature explained >50% of the total variability in ln[PCB] at both sites. Atmospheric concentrations at the suburban site increased when winds blew from an eastnortheast vector, while increased wind speeds led to a slight dilution. Wind speed and direction were not significantly correlated with the concentrations measured at the coastal site. Temporal changes in congener distribution at the suburban site are consistent with the preferential atmospheric removal of 3–5 Cl-biphenyls by hydroxyl radical attack with estimated half-lives of 0.7–1.8 years.     

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.     

Concentration-dependent NH3 deposition processes for mixed moorland semi-natural vegetation

Dry deposition modelling typically assumes that canopy resistance (R_c) is independent of ammonia (NH₃) concentration. An innovative flux chamber system was used to provide accurate continuous measurements of NH₃ deposition to a moorland composed of a mixture of Calluna vulgaris (L.) Hull, Eriophorum vaginatum L. and Sphagnum spp. Ammonia was applied at a wide range of concentrations (1–100 μg m⁻³). The physical and environmental properties and the testing of the chamber are described, as well as results for the moorland vegetation using the ‘canopy resistance’ and ‘canopy compensation point’ interpretations of the data.Results for moorland plant species demonstrate that NH₃ concentration directly affects the rate of NH₃ deposition to the vegetation canopy, with R_c and cuticular resistance (R_w) increasing with increasing NH₃ concentrations. Differences in R_c were found between night and day: during the night R_c increases from 17 s m⁻¹ at 10 μg m⁻³ to 95 s m⁻¹ at 80 μg m⁻³, whereas during the day R_c increases from 17 s m⁻¹ at 10 μg m⁻³ to 48 s m⁻¹ at 80 μg m⁻³. The lower resistance during the day is caused by the stomata being open and available as a deposition route to the plant. R_w increased with increasing NH₃ concentrations and was not significantly different between day and night (at 80 μg m⁻³ NH₃ day R_w=88 s m⁻¹ and night R_w=95 s m⁻¹). The results demonstrate that assessments using fixed R_c will over-estimate NH₃ deposition at high concentrations (over ∼15 μg m⁻³).     

Concentration-dependent NH3 deposition processes for moorland plant species with and without stomata

Currently, in operational modelling of NH₃ deposition a fixed value of canopy resistance (R_c) is generally applied, irrespective of the plant species and NH₃ concentration. This study determined the effect of NH₃ concentration on deposition processes to individual moorland species. An innovative flux chamber system was used to provide accurate continuous measurements of NH₃ deposition to Deschampsia cespitosa (L.) Beauv., Calluna vulgaris (L.) Hull, Eriophorum vaginatum L., Cladonia spp., Sphagnum spp., and Pleurozium schreberi (Brid.) Mitt. Measurements were conducted across a wide range of NH₃ concentrations (1–140 μg m⁻³).NH₃ concentration directly affects the deposition processes to the vegetation canopy, with R_c, and cuticular resistance (R_w) increasing with increasing NH₃ concentration, for all the species and vegetation communities tested. For example, the R_c for C. vulgaris increased from 14 s m⁻¹ at 2 μg m⁻³ to 112 s m⁻¹ at 80 μg m⁻³. Diurnal variations in NH₃ uptake were observed for higher plants, due to stomatal uptake; however, no diurnal variations were shown for non-stomatal plants. R_c for C. vulgaris at 80 μg m⁻³ was 66 and 112 s m⁻¹ during day and night, respectively. Differences were found in NH₃ deposition between plant species and vegetation communities: Sphagnum had the lowest R_c (3 s m⁻¹ at 2 μg m⁻³ to 23 at 80 μg m⁻³), and D. cespitosa had the highest nighttime value (18 s m⁻¹ at 2 μg m⁻³ to 197 s m⁻¹ at 80 μg m⁻³).     

Quantitative analysis of volatile organic compounds (VOCs) in atmospheric particles

There are a number of difficulties associated with the quantitative analysis of volatile organic compounds (VOCs) in atmospheric particles. Therefore, majority of the previous studies on VOCs associated with particles have been qualitative. Air samples were collected in Izmir, Turkey to determine ambient particle and gas phase concentrations of several aromatic, oxygenated and halogenated VOCs. Samples were quantitatively analyzed using thermal desorption–gas chromatography/mass spectrometry. Gas-phase concentrations ranged between 0.02 (bromoform) and 4.65 μg m⁻³ (toluene) and were similar to those previously measured at the same site. Particle-phase concentrations ranged from 1 (1,3-dichlorobenzene) to 933 pg m⁻³ (butanol). VOCs were mostly found in gas-phase (99.9±0.25%). However, the particulate VOCs had comparable concentrations to those reported previously for semivolatile organic compounds. The distribution of particle-phase VOCs between fine (d_p<2.5 μm) and coarse (2.5 μm<d_p<10 μm) fractions was also investigated. It was found that VOCs were mostly associated with fine particles.     

Biogenic VOC emissions from fresh leaf mulch and wood chips of Grevillea robusta (Australian Silky Oak)

The emissions of VOC from freshly cut and shredded Grevillea robusta (Australian Silky Oak) leaves and wood have been measured. The VOC emissions from fresh leaf mulch and wood chips lasted typically for 30 and 20 h respectively, and consisted primarily of ethanol, (E)-2-hexenal, (Z)-3-hexen-1-ol and acetaldehyde. The integrated emissions of the VOCs were 0.38±0.04 g kg⁻¹ from leaf mulch, and 0.022±0.003 g kg⁻¹ from wood chips. These emissions represent a source of VOCs in urban and rural air that has previously been unquantified and is currently unaccounted for. These VOCs from leaf mulch and wood chips will contribute to both urban photochemistry and secondary organic aerosol formation. Any CH₄ emissions from leaf mulch and wood chips were <1×10⁻¹¹ g g dry mass⁻¹ s⁻¹.