Dietary exposure of rainbow trout to 8:2 and 10:2 fluorotelomer alcohols and perfluorooctanesulfonamide: Uptake, transformation and elimination

The bioaccumulation of perfluorooctanesulfonamide (PFOSA) and two fluorotelomer alcohols (8:2 FTOH, 10:2 FTOH) by rainbow trout (Oncorhynchus mykiss) through dietary exposure, including depuration rates and metabolism was investigated. Concentrations in the spiked feed ranged from 10.9 μg g⁻¹ wet weight (wet wt) for PFOSA and 6.7 μg g⁻¹ wet wt for 8:2 FTOH to 5.0 μg g⁻¹ wet wt for 10:2 FTOH. Trout was fed at 1.5% body weight per day for 30 d and depuration was followed for up to 30 d following previously published dietary exposure protocols. Perfluorooctanesulfonate (PFOS) was the major perfluoroalkylsulfonate (PFSA) detected in fish following dietary exposure to PFOSA. Half-lives of PFOS and PFOSA were 16.9 ± 2.5 and 6.0 ± 0.4 d, respectively. A biomagnification factor (BMF) of 0.023 was calculated for PFOSA which indicates that dietary exposure to PFOSA does not result in biomagnification in the rainbow trout. PFOS had a BMF of 0.08. The fluorotelomer saturated acids (8:2 FTCA, 10:2 FTCA) and fluorotelomer unsaturated acids (8:2 FTUCA, 10:2 FTUCA) were the major products detected in rainbow trout following dietary exposure to 8:2 FTOH and 10:2 FTOH, respectively. Half-lives were 3.7 ± 0.4, 2.1 ± 0.5, 3.3, and 1.3 d for 10:2 FTCA, 10:2 FTUCA, 8:2 FTCA, and 8:2 FTUCA, respectively. Small amounts of perfluorooctanoate (PFOA) and perfluorodecanoate (PFDA) were also detected in the FTOH exposed fish.     

Quantification of the inhibitory effect of methyl fluoride on methanogenesis in mesophilic anaerobic granular systems

The inhibitory effect of CH₃F on methanogenesis in mesophilic anaerobic granules was tested at different concentrations (0-10% v/v, in the gas phase) and verified by the stable carbon isotopic signatures of CH₄ and CO₂. The results showed that the inhibitory effect increased with the initial CH₃F concentration up to 5%. The CH₃F concentration causing 50% metabolic inhibition was 0.32%. Complete inhibition of acetoclastic methanogenesis with a 91% reduction in total methanogenic activity was achieved when 5% CH₃F was initially added to the headspace, which resulted in 870 μM dissolved CH₃F in the liquid. It was much higher than that applied in other natural anoxic non-granular systems, indicating that the layered granular structure influenced the inhibitory effect. The obvious increase in hydrogen content indicated that high concentrations of CH₃F (?5%) suppressed hydrogenotrophic methanogenesis as well. The stable inhibition lasted for at least 6 d as the CH₃F concentration decreased slowly with incubation time. These results suggested that CH₃F could be used for investigating methanogenic processes in anaerobic granular systems after the CH₃F concentration and incubation time for specific inhibition of acetoclastic methanogenesis were carefully determined. In the present system, CH₃F concentration of 5% was suggested to be optimal.     

Photocatalytic mineralization of hydroperfluorocarboxylic acids with heteropolyacid H₄SiW₁₂O₄₀ in water

The decomposition of hydroperfluorocarboxylic acids [H-PFCAs; HC_nF_2nCOOH (n = 4 and 6)] induced by heteropolyacid photocatalyst H₄SiW₁₂O₄₀ in water was investigated, and the results are compared with the results for the corresponding perfluorocarboxylic acids (PFCAs; C_nF_2n+1COOH). This is the first report on the photochemical decomposition of H-PFCAs, which are being developed as alternative surfactants to environmentally persistent and bioaccumulative PFCAs. H-PFCAs were not decomposed by irradiation with UV-Visible light (>290 nm) in the absence of H₄SiW₁₂O₄₀. In contrast, UV-Visible light irradiation of H-PFCAs in the presence of H₄SiW₁₂O₄₀ efficiently decomposed H-PFCAs to F⁻ and CO₂. The decomposition reactions showed pseudo-first-order kinetics, and the decomposition rate constants were 1.8-2.5 times higher than those for the corresponding PFCAs. The reaction mechanism can be explained by elimination of H⁺ from the ω-H atom of the H-PFCAs by the excited catalyst, followed by formation of perfluorodicarboxylic acids.     

Carbon isotope signature of dissolved inorganic carbon (DIC) in precipitation and atmospheric CO2

This paper describes results of chemical and isotopic analysis of inorganic carbon species in the atmosphere and precipitation for the calendar year 2008 in Wroc?aw (SW Poland). Atmospheric air samples (collected weekly) and rainwater samples (collected after rain episodes) were analysed for CO₂ and dissolved inorganic carbon (DIC) concentrations and for δ¹³C composition. The values obtained varied in the ranges: atmospheric CO₂: 337-448 ppm; δ¹³C_CO2 from −14.4 to −8.4‰; DIC in precipitation: 0.6-5.5 mg dm⁻³; δ¹³C_DIC from −22.2 to +0.2‰. No statistical correlation was observed between the concentration and δ¹³C value of atmospheric CO₂ and DIC in precipitation. These observations contradict the commonly held assumption that atmospheric CO₂ controls the DIC in precipitation. We infer that DIC is generated in ambient air temperatures, but from other sources than the measured atmospheric CO₂. The calculated isotopic composition of a hypothetical CO₂ source for DIC forming ranges from −31.4 to −11.0‰, showing significant seasonal variations accordingly to changing anthropogenic impact and atmospheric mixing processes.     

Greenhouse gas production and efficiency of planted and artificially aerated constructed wetlands

Greenhouse gas (GHG) emissions by constructed wetlands (CWs) could mitigate the environmental benefits of nutrient removal in these man-made ecosystems. We studied the effect of 3 different macrophyte species and artificial aeration on the rates of nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) production in CW mesocosms over three seasons. CW emitted 2-10 times more GHG than natural wetlands. Overall, CH₄ was the most important GHG emitted in unplanted treatments. Oxygen availability through artificial aeration reduced CH₄ fluxes. Plant presence also decreased CH₄ fluxes but favoured CO₂ production. Nitrous oxide had a minor contribution to global warming potential (GWP < 15%). The introduction of oxygen through artificial aeration combined with plant presence, particularly Typha angustifolia, had the overall best performance among the treatments tested in this study, including lowest GWP, greatest nutrient removal, and best hydraulic properties.