Sampling silica and ferrihydrite colloids with fiberglass wicks under unsaturated conditions

The suitability of passive capillary samplers (PCAPS) for collection of representative colloid samples under partially saturated conditions was evaluated by investigating the transport of negatively and positively charged colloids in fiberglass wicks. A synthetic pore water solution was used to suspend silica microspheres (330 nm in diameter) and ferrihydrite (172 nm in diameter) for transport experiments on fiberglass wicks. Breakthrough curves were collected for three unsaturated flow rates with silica microspheres and one unsaturated flow rate with ferrihydrite colloids. A moisture characteristic curve, relating tensiometer measurements of matric potential to moisture content, was developed for the fiberglass wick. Results indicate that retention of the silica and the ferrihydrite on the wick occurred; that is, the wicks did not facilitate quantitative sampling of the colloids. For silica microspheres, 90% of the colloids were transmitted through the wicks. For ferrihydrite, 80 to 90% of the colloids were transmitted. The mechanisms responsible for the retention of the colloids on the fiberglass wicks appeared to be physicochemical attachment and not thin-film, triple-phase entrapment, or mechanical straining. Visualization of pathways by iron staining indicates that flow is preferential at the center of twisted bundles of filaments. Although axial preferential flow in PCAPS may enhance their hydraulic suitability for sampling mobile colloids, we conclude that without specific preparation to reduce attachment or retention, fiberglass wicks should only be used for qualitative sampling of pore water colloids.     

Characterization of organic coatings on hygroscopic salt particles and their atmospheric impacts

The photooxidation of α-pinene in the presence of NO₂, with and without added NaNO₃ seed particles, has been studied in a large-diameter flow tube. Particles formed by homogeneous nucleation and by condensation on the pre-existing seeds were sampled at various stages of the reaction, dried using four diffusion dryers, size selected at different mobility diameters (d_m) using a differential mobility analyzer (DMA), and characterized with a single particle mass spectrometer (SPLAT II). It was found that homogeneously nucleated particles are spherical, have a density (ρ) of 1.25 ± 0.02 g cm^?3 (±2σ) and contain a significant amount of organic nitrates. The mass spectra of the low volatility products condensed on the NaNO₃ seed particles were found to be virtually the same as in the case of homogeneous nucleation. The data show that the presence of even a submonolayer of organics on the NaNO₃ particles causes water retention that leads to a decrease in particle density and that the amount of water retained increases with organic coating thickness. Thicker coatings appear to inhibit water evaporation from the particle seeds altogether. This suggests that in the atmosphere, where low volatility organics are plentiful, some hygroscopic salts will retain water and have different densities and refractive indices than expected in the absence of the organic coating. This water retention combined with the organic shell on the particles can potentially impact light scattering by these particles and activity as cloud condensation nuclei (CCN), as well as heterogeneous chemistry and photochemistry on the particles.     

Water-soluble organic compounds at a mountain-top site in Colorado,USA

Water extracts of atmospheric particulate matter (PM_2.5) collected at the Storm Peak Laboratory (SPL) (3210 MSL, 40.45° N, 106.74° W) were analyzed for a wide variety of polar organic compounds. The unique geographical character of SPL allows for extended observations/sampling of the free tropospheric interface. Under variable meteorological conditions between January 9th and January14th 2007, the most abundant compounds were levoglucosan (9–72 ng m^?3), palmitic acid (10–40 ng m^?3) and succinic acid (18–27 ng m^?3). Of 84 analytes included in the GC–MS method, over 50 individual water extractable polar organic compounds (POC) were present at concentrations greater than 0.1 ng m^?3. During a snow event (Jan. 11th–13th), the concentrations of several presumed atmospheric transformation compounds (dicarboxylic acids) were reduced. Lower actinic flux, reduced transport distance, and ice crystal scavenging may explain this variability. Diurnal averages over the sampling period revealed a higher total concentration of water extractable POC at night, 211 ng m^?3 (105–265 ng m^?3), versus day, 160 ng m^?3 (137–205 ng m^?3), which suggests a more aged nighttime aerosol character. This may be due to the increased daytime convective mixing of local primary emissions from the Yampa Valley. XAD resin extracts revealed a gas-phase partitioning of several compounds, and analysis of cloud water collected at this site in 2002 revealed a similar compound abundance trend. Levoglucosan, a wood smoke tracer was generally found to be the most abundant compound in both aerosol and cloud water samples. Variations in meteorological parameters and local/regional transport analysis play an important interpretive role in understanding these results.     

Evaluation of an urban NMHC emission inventory by measurements and impact on CTM results

This paper presents an evaluation of the consistency of an urban state-of-the-art hydrocarbon (HC) emission inventory. The evaluation was conducted through the comparison of this inventory with hourly HC measurements during two summer months in the centre of Marseille, on the Mediterranean French coast. Factors of under or overestimation could be calculated for each compound on the basis of a systematic HC to HC ratio analysis. These results, associated with a deep analysis of the speciation profiles, show that most of the common and highly concentrated hydrocarbons (such as butanes) are too much predominant in the emission speciation, while the heavy and less common species (branched alkanes, substituted aromatics) are under-represented in the inventory. The urban diffuse sources appear here as one critical point of the inventories. The disagreements were shown to have a strong incidence on the representation of the air mass reactivity. In a last step, the identified uncertainties in emissions were implemented in an air-quality model for sensitivity studies. It was shown that the observed biases in the inventory could affect the regional ozone production, with a probable impact on ozone peaks of 2–10 ppbv over the area.     

Hydrological and environmental conditions as key drivers for spatial and seasonal changes in PCDD/PCDF concentrations, transport and deposition along urban cascade reservoirs

To investigate the drivers for transport and deposition of 17 2,3,7,8-substituted PCDDs/PCDFs along an urban river, water samples from five reservoirs located along the river course were collected in January and July 2008. The concentrations of 17 congeners of PCDD/PCDF were determined and compared to environmental - physical, chemical and biological - conditions. The obtained data revealed that the concentration of the sum of toxic PCDDs/PCDFs in water samples differ between reservoirs as well as between seasons, ranging from 12.04 pg L(-1) in UP (first in the cascade) to 1327.94 pg L(-1) in PR (last in the cascade) during winter of 2008; and from 34.94 pg L(-1) in UP to 1352.50 pg L(-1) in TR (next to last) in summer 2008. In comparison, water samples collected from the river had a concentration several times lower at the first two sites (sites no. 1 and 4) and no detectable values at the last three stations (sites no. 7, 8, 10). The obtained data demonstrated strong or moderate correlations between the sum of 17 PCDDs/PCDFs and TEQ in reservoir water samples and physical, chemical and biological conditions, such as: Mg(2+) (R=0.82; R=0.80, respectively), SO(4)(2-) (R=0.80; R=0.80, respectively), K(+) (R=0.80; R=0.80, respectively), Ca(2+) (R=0.67, R=0.70, respectively), OSM (R=0.63, R=0.70, respectively). In addition, the positive strong correlation between TEQ concentrations and the water temperature (R=0.63) and chlorophyll a content (R=0.90) was noted. The violent weather conditions occurred during the research season with periods of intensive storm events (up to 32 mm in mid July), and thus the increased river flow velocity (up to 0.45 m(3)s(-1)) could have a direct and indirect influence on PCDDs/PCDFs concentration through changes in the sedimentation/resuspension ratio and consequently in transport, deposition and degradation processes along the river/reservoirs.     

Multivariate analysis of mineral constituents of edible Parasol Mushroom (Macrolepiota procera) and soils beneath fruiting bodies collected from Northern Poland

Caps and stipes of 141 fruiting bodies of Parasol Mushroom (Macrolepiota procera) and surface layer of soils collected from 11 spatially distant and background (pristine) areas in Northern Poland were analyzed for Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, Sr, and Zn by inductively coupled plasma optical emission spectroscopy and cold vapor atomic absorption spectroscopy. In terms of bioconcentration and bioexclusion concept, K, Ag, Cu, Rb, and P were highly bioconcentrated in caps, and their bioconcentration factor values varied for the 11 sites between 120 and 500—67–420, 70–220, 10–170, and 45–100, respectively. Cd, Zn, Mg, and Na showed bioconcentration factors (BCFs) between 3.3 and 36, 3.7–15, 0.92–6.3, and 1.4–44 while Al, Ba, Ca, Co, Cr, Mn, Ni, Pb, and Sr were excluded (BCF < 1). The Parasol Mushroom is a species harvested in the wild, and its caps are of unique taste and can contain a spectrum of essential and hazardous mineral compounds accumulated at elevated concentrations, even if collected at the background (pristine) areas. These elevated mineral concentrations of the caps are due to the efficient bioconcentration potential of the species (K, Ag, Cu, Rb, P, Cd, Zn, Mg, and Na) and abundance in the soil substrates (Al, Ca, Fe, Mn). The estimated intake rates of Cd, Hg, and Pb contained in Parasol Mushroom’s caps show a cause for concern associated with these metals resulting from the consumption of between 300- and 500-g caps daily, on a frequent basis in the mushrooming season.     

Metals in edible fish from Vistula River and Dead Vistula River channel, Baltic Sea

Metals including Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Sr and Zn were determined in muscle tissue of 12 fish species by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and cold vapour-atomic absorption spectroscopy (CV-AAS). Fish were collected from Vistula River at lower course and Dead Vistula River channel in south of Baltic Sea in Poland. The fish species examined include Round Goby (Neogobius melanostomus), Crucian Carp (Carassius carassius), Bull-rout (Myoxocephalus scorpius), Tench (Tinca tinca), Bream (Abramis brama), Burbot (Lota lot), Perch (Perca perca), Roach (Rutilus rutilus), Silver Carp (Hypophthalmichthys molitrix), Pikeperch (Stizostediun lucioperca), Brown salmon (Salmo trutta m. Trutta) and Eel (Anguilla anguilla). The median values of metal concentrations in fresh muscle tissue of 11 fish species varied as follows: Al < 0.5-60; Ba < 0.05-0.31; Ca 120-1800; Cd < 0.05-0.096; Co < 0.10; Cr < 0.10-0.50; Cu < 0.15-0.77; Fe 1.5-21; Hg 0.0058-0.65; K 1800-4200; Mg 130-560; Mn 0.12-0.59; Na 350-840; Ni < 0.2-0.31; Pb < 0.75; Sr 0.079-2.9; Zn 3.3-23 μg/g fresh weight. The Target Hazard Quotient (THQ) values calculated in this study for Cd and Hg from muscles of fish species collected from Vistula River were low in the range of 0.4 for Hg and 0.8 for Cd.     

Estimation of K(OA) values of 209 polychlorinated trans-azobenzenes by PM6 and DFT methods

The octanol-air partition coefficients (K(OA)) of all 209 PCt-ABs were determined computationally to fill gaps on their environmentally relevant physical and chemical properties. These properties have been determined using two computational approaches: the semi-empirical quantum chemistry method for property parameterization (PM6) of the molecular orbital package (MOPAC) and density functional theory (DFT) method using B3LYP functional and 6-311++G** basis set in Gaussian 03 software and artificial neural network (ANN) predicting abilities. Both computational methods enabled estimation of log K(OA) partition coefficients of PCt-ABs with a similar accuracy and precision. The PM6 method compared to DFT was highly superior because it requires much less time, manpower and cost of hardware. The determined log K(OA) values of the investigated PCt-ABs for standard condition (25 °C) varied between 8.30 and 8.75 for Mono-; 8.71 and 9.92 for Di-; 9.58 and 10.72 for Tri-; 10.11 and 11.34 for Tetra-, 10.83 and 11.85 for Penta-; 11.24 and 12.36 for Hexa-; 11.87 and 12.66 for Hepta-; 12.31 and 12.97 for Octa-; 12.89 and 13.21 for Nona-Ct-ABs; and 13.17- and 13.49 for Deca-Ct-AB. PCt-ABs, in view of these log K(OA) values, can be classified as compounds of relatively low (Mono-, Di- and some of Tri- Ct-ABs with values of log K(OA) around 8 to 10) environmental mobility (most of Tri- to Nona-Ct-ABs and Deca-Ct-AB homologues with values of log K(OA) >10), and with a potential to be adsorbed by soil particles.     

Mercury in European Blushers, Amanita rubescens, mushrooms and topsoils: bioconcentration potential and intake assessment

Total mercury content has been determined in fruiting bodies of European Blushers and topsoils collected from 11 sites across Poland in 2006-2008. Mercury analysis was carried out using a validated analytical method and cold-vapour atomic absorption (CV-AAS). The European Blusher effectively accumulated mercury in fruiting bodies. The mean values of total mercury in caps of European Blushers from background (uncontaminated) areas were from 0.22 to 1.0 (0.067-3.2) and in stipes from 0.16 to 0.65 (0.071-2.7) μg/g dry weight. In topsoil beneath to fruiting bodies, the median Hg concentration at 10 sites in Northern Poland varied between 0.030 and 0.072 (0.0096-0.19) μg/g dw, and in one site in Southern Poland was 0.20 (0.079-0.34) μg/g dw. Data on Hg in European Blushers from different countries were reviewed. The mean concentrations of total Hg in caps of European Blushers from two "pristine" sites in northern part of Poland were ～1.0 μg/g dw. A meal made with 300-500 g of fresh caps of European Blushers collected at such sites (assuming 90% water content in caps) can result in Hg intake of 0.0003-0.0005 mg Hg/kg bm (assuming a 60 kg bm), which is a dose equipotent to a new provisional tolerable weekly intake (PTWI) value set for inorganic Hg.