Trophic
Magnification and Isomer Fractionation of
Perfluoroalkyl Substances in the Food Web of Taihu Lake, China
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Abstract
Biomagnification
of perfluoroalkyl substances (PFASs) are well
studied in marine food webs, but related information in fresh water
ecosystem and knowledge on fractionation of their isomers along the
food web are limited. The distribution, bioaccumulation, magnification,
and isomer fractionation of PFASs were investigated in a food web
of Taihu Lake, China. Perfluorooctanesulfonate (PFOS) and perfluorocarboxylates
(PFCAs) with longer carbon chain lengths, such as perfluorodecanoate
(PFDA) and perfluoroundecanoate (PFUnA), were predominant in organisms,
while perfluorohexanoate (PFHxA) and perfluorooctanoate (∑PFOA)
contributed more in the water phase. The consistent profile signature
of PFOA isomers in water phase with 3M electrochemical fluorination
(ECF) products suggests that ECF production of PFOA still exists in
China. Linear proportions of PFOA, PFOS and perfluorooctane sulfonamide
(PFOSA) in the biota were in the range of 91.9–100%, 78.6–95.5%,
and 72.2–95.5%, respectively, indicating preferential bioaccumulation
of linear isomers in biota. Trophic magnification factors (TMFs) were
estimated for PFDA (2.43), perfluorododecanoate (PFDoA) (2.68) and
PFOS (3.46) when all biota were included, suggesting that PFOS and
long-chained PFCAs are biomagnified in the fresh water food web. The
TMF of PFOS isomers descended in the order: <i>n</i>-PFOS
(3.86) > 3+5<i>m</i>-PFOS (3.35) > 4<i>m</i>-PFOS (3.32) > 1<i>m</i>-PFOS (2.92) > <i>m</i><sub>2</sub>-PFOS (2.67) > <i>iso</i>-PFOS (2.59), which
is roughly identical to their elution order on a FluoroSep-RP Octyl
column, suggesting that hydrophobicity may be an important contributor
for isomer discrimination in biota