Perfluoroalkyl acids
(PFAAs) are widely distributed in the oceans
which are their largest global reservoir, but knowledge is limited
about their vertical distribution and fate. This study measured the
concentrations of PFAAs (perfluoroalkyl carboxylic acids (PFCAs) with
6 to 11 carbons and perfluoroalkanesulfonic acids (PFSAs) with 6 and
8 carbons) in the surface and deep ocean. Seawater depth profiles
from the surface to a 5000 m depth at 28 sampling stations were collected
in the Atlantic Ocean from ∼50° N to ∼50°
S. The results demonstrated PFAA input from the Mediterranean Sea
and the English Channel. Elevated PFAA concentrations were observed
at the eastern edge of the Northern Atlantic Subtropical Gyre, suggesting
that persistent contaminants may accumulate in ocean gyres. The median
ΣPFAA surface concentration in the Northern Hemisphere (n= 17) was 105 pg L–1, while for the
Southern Hemisphere (n= 11) it was 28 pg L–1. Generally, PFAA concentrations decreased with increasing distance
to the coast and increasing depth. The C6–C9 PFCAs and C6 and
C8 PFSAs dominated in surface waters, while longer-chain PFAAs (C10–C11
PFCAs) peaked at intermediate depths (500–1500 m). This profile
may be explained by stronger sedimentation of longer-chain PFAAs,
as they sorb more strongly to particulate organic matter.