Sorption of Perfluoroalkyl Phosphonates and Perfluoroalkyl Phosphinates in Soils

Perfluoroalkyl phosphonates (PFPAs) and perfluoroalkyl phosphinates (PFPiAs) are recently discovered perfluoroalkyl acids (PFAAs) that have been widely detected in house dust, aquatic biota, surface water, and wastewater environments. The sorption of C6, C8, and C10 monoalkylated PFPAs and C6/C6, C6/C8, and C8/C8 dialkylated PFPiAs was investigated in seven soils of varying geochemical parameters. Mean distribution coefficients, log <i>K</i>_d^*, ranged from 0.2 to 2.1 for the PFPAs and PFPiAs and were generally observed to increase with perfluoroalkyl chain length. The log<i> K</i>_d^* of PFPiAs calculated here (1.6–2.1) were similar to those previously measured for the longer-chain perfluorodecanesulfonate (1.9, PFDS) and perfluoroundecanoate (1.7, PFUnA) in sediments, but overall when compared as a class, were greater than those for the perfluoroalkanesulfonates (−0.8–1.9, PFSAs), perfluoroalkyl carboxylates (−0.4–1.7, PFCAs), and PFPAs (0.2–1.5). No single soil-specific parameter, such as pH and organic carbon content, was observed to control the sorption of PFPAs and PFPiAs, the lack of which may be attributed to competing interferences in the naturally heterogeneous soils. The PFPAs were observed to desorb to a greater extent and likely circulate as aqueous contaminants in the environment, while the more sorptive PFPiAs would be preferentially retained by environmental solid phases

Dietary Bioaccumulation of Perfluorophosphonates and Perfluorophosphinates in Juvenile Rainbow Trout: Evidence of Metabolism of Perfluorophosphinates

The perfluorophosphonates (PFPAs) and perfluorophosphinates (PFPiAs) are high production volume chemicals that have been observed in Canadian surface waters and wastewater environments. To examine whether their occurrence would result in contamination of organisms in aquatic ecosystems, juvenile rainbow trout (<i>Oncorhynchus mykiss)</i> were separately exposed to a mixture of C6, C8, and C10 monoalkylated PFPAs and a mixture of C6/C6, C6/C8, and C8/C8 dialkylated PFPiAs in the diet for 31 days, followed by 32 days of depuration. Tissue distribution indicated preferential partitioning to blood and liver. Depuration half-lives ranged from 3 to 43 days and increased with the number of perfluorinated carbons present in the chemical. The assimilation efficiencies (α, 7–34%) and biomagnification factors (BMFs, 0.007–0.189) calculated here for PFPAs and PFPiAs were lower than those previously observed for the perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs) in the same test organism. Bioaccumulation was observed to decreased in the order of PFSAs > PFCAs > PFPAs of equal perfluorocarbon chain length and was dependent on the charge of the polar headgroup. Bioaccumulation of the PFPiAs was observed to be low due to their rapid elimination via metabolism to the corresponding PFPAs. Here, we report the first observation of an <i>in vivo</i> cleavage of the carbon–phosphorus bond in fish, as well as, the first <i>in vivo</i> biotransformation of a perfluoroalkyl acid (PFAA). As was previously observed for PFCAs and PFSAs, none of the BMFs determined here for the PFPAs and PFPiAs were greater than one, which suggests PFAAs do not biomagnify from dietary exposure in juvenile rainbow trout

Investigating the Biodegradability of a Fluorotelomer-Based Acrylate Polymer in a Soil–Plant Microcosm by Indirect and Direct Analysis

Fluorotelomer-based acrylate polymers (FTACPs) are a class of side-chain fluorinated polymers used for a variety of commercial applications. The degradation of FTACPs through ester hydrolysis, cleavage of the polymer backbone, or both could serve as a significant source of perfluoroalkyl carboxylates (PFCAs). The biodegradation of FTACPs was evaluated in a soil–plant microcosm over 5.5 months in the absence/presence of wastewater treatment plant (WWTP) biosolids using a unique FTACP determined to be a homopolymer of 8:2 fluorotelomer acrylate (8:2 FTAC). Although structurally different from commercial FTACPs, the unique FTACP possesses 8:2 fluorotelomer side chain appendages bound to the polymer backbone via ester moieties. Liberation and subsequent biodegradation of the 8:2 fluorotelomer appendages was indirectly determined by monitoring for PFCAs of varying chain lengths (C6–C9) and known fluorotelomer intermediates by liquid chromatography tandem mass spectrometry (LC–MS/MS). A FTACP biodegradation half-life range of 8–111 years was inferred from the 8:2 fluorotelomer alcohol (8:2 FTOH) equivalent of the unique FTACP and the increase of degradation products. The progress of FTACP biodegradation was also directly monitored qualitatively using matrix-assisted laser desorption/ionization (MALDI-TOF) time-of-flight mass spectrometry. The combination of indirect and direct analysis indicated that the model FTACP biodegraded predominantly to perfluorooctanoate (PFOA) in soils and at a significantly higher rate in the presence of a plant and WWTP biosolids

Fate of Polyfluoroalkyl Phosphate Diesters and Their Metabolites in Biosolids-Applied Soil: Biodegradation and Plant Uptake in Greenhouse and Field Experiments

Significant contamination of perfluoroalkyl acids (PFAAs) in wastewater treatment plant (WWTP) sludge implicates the practice of applying treated sludge or biosolids as a potential source of these chemicals onto agricultural farmlands. Recent efforts to characterize the sources of PFAAs in the environment have unveiled a number of fluorotelomer-based materials that are capable of degrading to the perfluoroalkyl carboxylates (PFCAs), such as the polyfluoroalkyl phosphate diesters (diPAPs), which have been detected in WWTP and paper fiber biosolids. Here, a greenhouse microcosm was used to investigate the fate of endogenous diPAPs and PFCAs present in WWTP and paper fiber biosolids upon amendment of these materials with soil that had been sown with Medicago truncatula plants. Biodegradation pathways and plant uptake were further elucidated in a separate greenhouse microcosm supplemented with high concentrations of 6:2 diPAP. Biosolid-amended soil exhibited increased concentrations of diPAPs (4–83 ng/g dry weight (dw)) and PFCAs (0.1–19 ng/g dw), as compared to control soils (nd–1.4 ng/g dw). Both plant uptake and biotransformation contributed to the observed decline in diPAP soil concentrations over time. Biotransformation was further evidenced by the degradation of 6:2 diPAP to its corresponding fluorotelomer intermediates and C4–C7 PFCAs. Substantial plant accumulation of endogenous PFCAs present in the biosolids (0.1–138 ng/g wet weight (ww)) and those produced from 6:2 diPAP degradation (100–58 000 ng/g ww) were observed within 1.5 months of application, with the congener profile dominated by the short-chain PFCAs (C4–C6). This pattern was corroborated by the inverse relationship observed between the plant–soil accumulation factor (PSAF, <i>C</i>_plant/<i>C</i>_soil) and carbon chain length (<i>p</i> < 0.05, <i>r</i> = 0.90–0.97). These results were complemented by a field study in which the fate of diPAPs and PFCAs was investigated upon application of compost and paper fiber biosolids to two farm fields. Together, these studies provide the first evidence of soil biodegradation of diPAPs and the subsequent uptake of these chemicals and their metabolites into plants

Li/X Phosphinidenoid Pentacarbonylmetal Complexes: A Combined Experimental and Theoretical Study on Structures and Spectroscopic Properties

The synthesis of <i>P</i>-F phosphane metal complexes [(CO)₅M­{RP­(H)­F}] <b>2a</b>–<b>c</b> (R = CH­(SiMe₃)₂; <b>a</b>: M = W; <b>b</b>: M = Mo; <b>c</b>: M = Cr) is described using AgBF₄ for a Cl/F exchange in <i>P</i>-Cl precursor complexes [(CO)₅M­{RP­(H)­Cl}] <b>3a</b>–<b>c</b>; thermal reaction of 2<i>H</i>-azaphosphirene metal complexes [(CO)₅M­{RP­(C­(Ph)N}] <b>1a</b>–<b>c</b> with [Et₃NH]­X led to complexes <b>3a</b>–<b>c</b>, <b>4</b>, and <b>5</b> (M = W; <b>a</b>–<b>c</b>: X = Cl; <b>4</b>: X = Br; <b>5</b>: X = I). Complexes <b>2a</b>–<b>c</b>, <b>3a</b>–<b>c</b>, <b>4</b>, and <b>5</b> were deprotonated using lithium diisopropylamide in the presence of 12-crown-4 thus yielding Li/X phosphinidenoid metal complexes [Li­(12-crown-4)­(Et₂O)_<i>n</i>]­[(CO)₅M­(RPX)] <b>6a</b>–<b>c</b>, <b>7a</b>–<b>c</b>, <b>8</b>, and <b>9</b> (<b>6a</b>–<b>c</b>: M = W, Mo, Cr; X = F; <b>7a</b>–<b>c</b>: M = W, Mo, Cr; X = Cl; <b>8</b>: M = W; X = Br; <b>9</b>: M = W; X = I). This first comprehensive study on the synthesis of the title compounds reveals metal and halogen dependencies of NMR parameters as well as thermal stabilities of <b>6a</b>, <b>7a</b>, <b>8</b>, and <b>9</b> in solution (F > Cl > Br > I). DOSY NMR experiments on the Li/F phosphinidenoid metal complexes (<b>6a</b>–<b>c</b>; M = W, Mo, Cr) rule out that the cation and anion fragments are part of a persistent molecular complex or tight ion pair (in solution). The X-ray structure of <b>6a</b> reveals a salt-like structure of [Li­(12-crown-4)­Et₂O]­[(CO)₅W­{P­(CH­(SiMe₃)₂)­F}] with long P–F and P–W bond distances compared to <b>2a</b>. Density functional theory (DFT) calculations provide additional insight into structures and energetics of cation-free halophosphanido chromium and tungsten complexes and four contact ion pairs of Li/X phosphinidenoid model complexes [Li­(12-crown-4)]­[(CO)₅M­{P­(R)­X}] (<b>A-D</b>) that represent principal coordination modes. The significant increase of the compliance constant of the P–F bond in the anionic complex [(CO)₅W­{P­(Me)­F}] (<b>10a</b>) revealed that a formal lone pair at phosphorus weakens the P–F bond. This effect is further enhanced by coordination of lithium and/or the Li­(12-crown-4) countercation (to <b>10a</b>) as in type <b>A-D</b> complexes. DFT calculated phosphorus NMR chemical shifts allow for a consistent interpretation of NMR properties and provide a preliminary explanation for the “abnormal” NMR shift of <i>P</i>-Cl derivatives <b>7a</b>–<b>c</b>. Furthermore, calculated compliance constants reveal the degree of P–F bond weakening in Li/F phosphinidenoid complexes, and it was found that a more negative phosphorus–fluorine coupling constant is associated with a larger relaxed force constant