Landfills and waste water treatment plants as sources of ... - GKSS

INTRODUCTION
1.3 Physico-chemical properties
Ionic and neutral PFCs, PBDEs and musk fragrances have considerably different physicochemical
properties that determine their partitioning behaviour in the environment. In general,
those properties are determined by their functional groups within the molecule as well as
carbon-fluorine chain lengths (PFCs) or bromine content (PBDEs). Physico-chemical
constants of substances investigated in this study are presented in table 4.
The vapour pressures of PFSAs and PFCAs are generally low (Rayne and Forest 2009). In
contrast, vapour pressures of neutral PFCs are more than 1000 times higher than those of
ionic PFCs (Hekster et al. 2002; Rayne and Forest 2009). Vapour pressures of PBDEs are
directly linked to the bromine content of the congener. Each additional bromine substitution
causes a decline of vapour pressures by factors of 6-9 (Wong et al. 2001). Musk fragrances
have comparable vapour pressures as FASEs. Therefore, neutral PFCs, BDE28 and BDE47 as
well as musk fragrances are likely being transported as gaseous compounds in the
atmosphere. Ionic PFCs and higher-brominated BDE congeners are not primarily expected in
the gas phase, but atmospheric transport may still be possible if compounds adsorb to
particles.
The water solubilities of ionic PFCs are several orders of magnitude higher than those of
neutral PFCs. Solubility decreases with increasing chain length of the both neutral and ionic
PFCs (Rayne and Forest 2009). In contrast, musk fragrances are fairly well soluble in water. It
is assumed that PBDEs are not predominantly transported via the water phase, whereas musk
fragrances are more likely entering aqueous media (Rimkus 1999; Wania and Dugani 2003).
Ionic PFCs are predominantly dissolved in the aqueous phase and/or bound to particles
(especially long-chained PFSAs) (Rayne and Forest 2009).
Polycyclic musk fragrances and FTOHs have relatively high Henry’s law constants that
exceed those of PBDEs and nitro musks. For PBDEs, the tendency to volatilize from the
water phase is influenced by the degree of bromination (Wong et al. 2001). In contrast to
FTOHs, ionic PFCs have lower Henry constants (OECD 2002). Overall, it can be concluded
that particularly FTOHs and polycyclic musk fragrances may volatilize from the aqueous
phase to the atmosphere, whereas PBDEs and ionic PFCs rather partition to the water phases.
It has been reported that KOA values for PBDEs, FTOHs, FASAs and FASEs are increasing
with decreasing of temperatures (Harner and Shoeib 2002; Thuens et al. 2008; Dreyer et al.
2009a). Particularly highly brominated congeners are expected in the particle phase (Harner
and Shoeib 2002). For musk fragrances KOA values have not yet been reported. However,
10