Potential role of sea spray generation in the atmospheric transport of perfluorocarboxylic acids.
ABSTRACT The observed environmental concentrations of perfluorooctanoic acid (PFOA) and its conjugate base (PFO) in remote regions such as the Arctic have been primarily ascribed to the atmospheric transport and degradation of fluorotelomer alcohols (FTOHs) and to direct PFO transport in ocean currents. These mechanisms are each capable of only partially explaining observations. Transport within marine aerosols has been proposed and may explain transport over short distances but will contribute little over longer distances. However, PFO(A) has been shown to have a very short half-life in aqueous aerosols and thus sea spray was proposed as a mechanism for the generation of PFOA in the gas phase from PFO in a water body. Using the observed PFO concentrations in oceans of the Northern Hemisphere and estimated spray generation rates, this mechanism is shown to have the potential for contributing large amounts of PFOA to the atmosphere and may therefore contribute significantly to the concentrations observed in remote locations. Specifically, the rate of PFOA release into the gas phase from oceans in the Northern Hemisphere is calculated to be potentially comparable to global stack emissions to the atmosphere. The subsequent potential for atmospheric degradation of PFOA and its global warming potential are considered. Observed isomeric ratios and predicted atmospheric concentrations due to FTOH degradation are used to elucidate the likely relative importance of transport pathways. It is concluded that gas phase PFOA released from oceans may help to explain observed concentrations in remote regions. The model calculations performed in the present study strongly suggest that oceanic aerosol and gas phase field monitoring is of vital importance to obtain a complete understanding of the global dissemination of PFCAs.
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ABSTRACT: Nonylphenol ethoxylates (NPEOs) are environmentally ubiquitous non-ionizing surfactants that show a preference for the air–water interface. They are therefore potentially subject to enhanced transport by aqueous aerosols. The extent to which aqueous aerosols affect the overall environmental fate and behavior of NPEOs is investigated with a combination of laboratory and field experiments and mathematical modeling. Aqueous aerosol droplets were generated in a laboratory-based experimental system. Aqueous aerosols were measured to have concentrations of NPEOs at least four times greater than in the bulk source water.The concentration of nonylphenol and nonylphenol monoethoxylate in aqueous aerosols off the coast of Bermuda were 4.3–19.2 times higher than in coastal water and open water collected from the Bermuda Atlantic Time Series sampling site. Coastal water showed higher concentrations than open water samples ranging from 36 to 51 ng L−1 and 14 to 21 ng L−1 respectively. Depth profiling showed a loss of detection below 300 m. Aqueous aerosol enrichment was demonstrated and relative atmospheric concentrations ranged from 0.28 to 1.8 ng m−3. A generic marine model was developed using independent North Sea data to estimate the relative potential for NPEO transfer within spray droplets to the atmosphere and subsequently into the gas phase by volatilization. The results were compared to the estimated direct volatilization from the surface of a natural water body. The upward mass flux of NPEOs by direct volatilization was comparable in magnitude to the fluxes due to spray generation, depending on the wind speed and droplet sizes. The experimental results and the model calculations were illustratively applied to reported NPEO concentrations in the North Sea. Aerosol generation provides a feasible mechanism for atmospheric transport of NPEOs and their degradation products, nonylphenols (NPs).Atmospheric Environment 04/2013; 69:304–312. · 3.06 Impact Factor
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ABSTRACT: The use of snow and ice cores as recorders of environmental contamination is particularly relevant for per- and polyfluoroalky substances (PFASs) given their production history, differing source regions and varied mechanisms driving their global distribution. In a unique study perfluoroalkyl acids (PFAAs) were analysed in dated snow-cores obtained from high mountain glaciers on the Tibetan Plateau (TP). One snow core was obtained from the Mt Muztagata glacier (accumulation period of 1980-1999), located in western Tibet and a second core from Mt. Zuoqiupo (accumulation period: 1996-2007) located in south eastern Tibet, with fresh surface snow collected near Lake Namco in 2010 (southern Tibet). The higher concentrations of ΣPFAAs were observed in the older Mt Muztagata core and dominated by perfluorooctanesulfonic acid (PFOS) (61.4-346 pg/L) and perflurooctanoic acid (PFOA) (40.8-243 pg/L), whereas in the Mt Zuoqiupu core the concentrations were lower (e.g. PFOA: 37.8-183 pg/L) with PFOS below detection limits. These differences in PFAA concentrations and composition profile likely reflect the upwind sources affecting the respective sites (e.g. European/central Asian sources for Mt Muztagata and India sources for Mt Zuoqiupu). Perfluorobutanoic acid (PFBA) dominated the recent surface snowpack of Lake Namco which is mainly associated with India sources where the shorter chain volatile PFASs precursors predominate. The use of snow cores in different parts of Tibet provides useful recorders to examine the influence of different PFASs source regions and reflect changing PFAS production/use in the Northern Hemisphere.Environmental Science & Technology 12/2013; · 5.48 Impact Factor
- Environmental Chemistry 08/2011; 8(4):399-406. · 3.04 Impact Factor