6 research outputs found
Ombrotrophic Peat Bogs Are Not Suited as Natural Archives To Investigate the Historical Atmospheric Deposition of Perfluoroalkyl Substances
No full textAs ombrotrophic peat bogs receive only atmospheric input of contaminants, they have been identified as suitable natural archives for investigating historical depositions of airborne pollutants. To elucidate their suitability for determining the historical atmospheric contamination with perfluoroalkyl substances (PFAS), two peat cores were sampled at Mer Bleue, a bog located close to Ottawa, Canada. Peat cores were segmented, dried, and analyzed in duplicate for 25 PFASs (5 perfluororalkyl sulfonates (PFSAs), 13 perfluoroalkyl carboxylates (PFCAs), 7 perfluororalkyl sulfonamido substances). Peat samples were extracted by ultrasonication, cleaned up using a QuEChERS method, and PFASs were measured by HPLC-MS/MS. Twelve PFCAs and PFSAs were detected regularly in peat samples with perfluorooctane sulfonate (85-655 ng kg-1), perfluorooctanoate (150-390 ng kg-1), and perfluorononanoate (45-320 ng kg-1) at highest concentrations. Because of post depositional relocation processes within the peat cores, true or unbiased deposition fluxes (i.e., not affected by post depositional changes) could not be calculated. Apparent or biased deposition rates (i.e., affected by post depositional changes) were lower than measured/calculated deposition rates for similar urban or near-urban sites. Compared to PFAS production, PFAS concentration and deposition maxima were shifted about 30 years toward the past and some analytes were detected even in the oldest segments from the beginning of the 20th century. This was attributed to PFAS mobility in the peat profile. Considerable differences were observed between both peat cores and different PFASs. Overall, this study demonstrates that ombrotrophic bogs are not suited natural archives to provide authentic and reliable temporal trend data of historical atmospheric PFAS deposition. © 2012 American Chemical Society
How suitable are peat cores to study historical deposition of PAHs?
No full textOmbrotrophic peat bogs are natural archives of atmospheric pollution, their depth profiles can be used to study the deposition chronology of harmful contaminants. Prerequisites for deriving historical deposition rates from the peat archive are that contaminants are persistent and immobile in the peat and that the applied dating technique is accurate. To examine these requirements and the accuracy of peat archives for polycyclic aromatic hydrocarbons (PAHs) 12 peat profiles were sampled in 4 bogs in Ontario, Canada, as well as surface peat in one bog. Additionally we carried out laboratory incubations; no degradation occurred over a 3-year period in these experiments. The standard deviations of PAN concentrations in surface samples and of PAH inventories in whole cores was approximately 30%, and concentrations in surface peat were on average 50% higher in hollows than in hummocks. No indications for mobility of PAHs were observed in peat. Temporal deposition trends inferred from peat cores were generally in agreement with trends derived from a sediment core sampled close by but deposition rates to the sediment were substantially higher. A major source of uncertainty was the rather coarse vertical sampling resolution of 5 cm which introduced substantial uncertainty in the dating of the individual segments. This caused variations of the deposition rates up to 70% per PAH between three replicate cores, and it also impedes the identification of deposition peaks. Overall, we conclude that peat cores are suitable archives for inferring atmospheric deposition trends, but due to their relatively low temporal resolution short-term events may not be identified and the development of sampling methods that allow a higher vertical resolution would greatly improve the performance of the method. The analysis of more than one core per site is suggested to provide a realistic estimate of the historic deposition and total inventories.</p
Comparison of Atmospheric Travel Distances of Several PAHs Calculated by Two Fate and Transport Models (The Tool and ELPOS) with Experimental Values Derived from a Peat Bog Transect
No full textMultimedia fate and transport models are used to evaluate the long range transport potential (LRTP) of organic pollutants, often by calculating their characteristic travel distance (CTD). We calculated the CTD of several polycyclic aromatic hydrocarbons (PAHs) and metals using two models: the OECD POV& LRTP Screening Tool (The Tool), and ELPOS. The absolute CTDs of PAHs estimated with the two models agree reasonably well for predominantly particle-bound congeners, while discrepancies are observed for more volatile congeners. We test the performance of the models by comparing the relative ranking of CTDs with the one of experimentally determined travel distances (ETDs). ETDs were estimated from historical deposition rates of pollutants to peat bogs in Eastern Canada. CTDs and ETDs of PAHs indicate a low LRTP. To eliminate the high influence on specific model assumptions and to emphasize the difference between the travel distances of single PAHs, ETDs and CTDs were analyzed relative to the travel distances of particle-bound compounds. The ETDs determined for PAHs, Cu, and Zn ranged from 173 to 321 km with relative uncertainties between 26% and 46%. The ETDs of two metals were shorter than those of the PAHs. For particle-bound PAHs the relative ETDs and CTDs were similar, while they differed for Chrysene
Ombrotrophic Peat Bogs Are Not Suited as Natural Archives To Investigate the Historical Atmospheric Deposition of Perfluoroalkyl Substances
No full textAs ombrotrophic peat bogs receive only atmospheric input
of contaminants,
they have been identified as suitable natural archives for investigating
historical depositions of airborne pollutants. To elucidate their
suitability for determining the historical atmospheric contamination
with perfluoroalkyl substances (PFAS), two peat cores were sampled
at Mer Bleue, a bog located close to Ottawa, Canada. Peat cores were
segmented, dried, and analyzed in duplicate for 25 PFASs (5 perfluororalkyl
sulfonates (PFSAs), 13 perfluoroalkyl carboxylates (PFCAs), 7 perfluororalkyl
sulfonamido substances). Peat samples were extracted by ultrasonication,
cleaned up using a QuEChERS method, and PFASs were measured by HPLC-MS/MS.
Twelve PFCAs and PFSAs were detected regularly in peat samples with
perfluorooctane sulfonate (85–655 ng kg–1), perfluorooctanoate (150–390 ng kg–1),
and perfluorononanoate (45–320 ng kg–1) at
highest concentrations. Because of post depositional relocation processes
within the peat cores, true or unbiased deposition fluxes (i.e., not
affected by post depositional changes) could not be calculated. Apparent
or biased deposition rates (i.e., affected by post depositional changes)
were lower than measured/calculated deposition rates for similar urban
or near-urban sites. Compared to PFAS production, PFAS concentration
and deposition maxima were shifted about 30 years toward the past
and some analytes were detected even in the oldest segments from the
beginning of the 20th century. This was attributed to PFAS mobility
in the peat profile. Considerable differences were observed between
both peat cores and different PFASs. Overall, this study demonstrates
that ombrotrophic bogs are not suited natural archives to provide
authentic and reliable temporal trend data of historical atmospheric
PFAS deposition
Determination of the Octanol−Air Partition Coefficients (<i>K</i><sub>OA</sub>) of Fluorotelomer Alcohols
No full textOctanol−air partition coefficients (KOA) for five fluorotelomer alcohols (4:2 FTOH, 6:2 FTOH, 8:2 FTOH, 10:2 FTOH, and for the first time 12:2 FTOH) were determined over a temperature range from (5 to 40) °C using a modified generator column method. Octanol-saturated air at a fixed temperature was blown over a column filled with glass spheres which were coated with an FTOH solution. FTOHs partitioning to the gas phase were collected on a trap filled with XAD-2 and eluted with acetone afterward. The concentrations of FTOH were measured by GC-MS using positive chemical ionization. The KOA values were calculated as the ratio of the FTOH concentrations in the octanol to the FTOH concentrations in the air. Values of log KOA at 25 °C ranged from 4.5 (4:2 FTOH) to 6.2 (12:2 FTOH). The calculated internal energies of phase change (ΔUOA) ranged from 42.8 kJ·mol−1 (12:2 FTOH) to 61.1 kJ·mol−1 (4:2 FTOH). The combined uncertainty of the method applied ranged from 8.3 % (4:2 FTOH) to 10.5 % (10:2 FTOH). The expanded uncertainty (P = 95 %) ranged from 18.7 % (4:2 FTOH) to 38.7 % (10:2 FTOH), respectively
Application of XAD-resin based passive air samplers to assess local (roadside) and regional patterns of persistent organic pollutants
No full textWe used XAD-resin based passive air samplers (PAS) to measure atmospheric levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) at five ombrotrophic bogs in Eastern Canada. The aims of our study were to investigate the influence of local roads on contaminant levels in the bogs, to derive the regional pattern of atmospheric concentrations, and to assess the uncertainties of the method. Expanded uncertainties based on the duplicate PAS deployed at 24 sites were good for the PAHs, while the deployment period of approx. 100 days was too short to yield acceptable uncertainties for PCBs. The regional PAH distribution was in good agreement with the calculated source proximity of the sampled bogs. We conclude that XAD-resin based PAS deployed for comparatively short periods are well suited for measuring atmospheric concentrations of volatile PAHs, while in remote regions longer deployment is necessary for less volatile PAHs and for PCBs.</p
