sources for this compound downstream of the basin is reinforced by the lack of
correlation between its levels and those of major PFASs (e.g. PFOS).
During this monitoring study, the river flow rate was in the range 30–100 m
3 s
À1
at Marnay and 170–500 m
3 s
À1 at Triel. At each site, PFAS levels appeared constant
under stable hydrological conditions over short monitoring periods (e.g. 4 weeks),
while the molecular pattern remained unchanged for a given site. Seasonal variations
were examined at the water year scale, and the highest PFAS concentrations
appeared to be associated with low-flow conditions. At the downstream sites
(e.g. under the influence of the Paris conurbation), all major PFASs displayed
negative correlations with flow rate, strongly suggesting that point sources were
predominant. However, at the farthest upstream site, a few compounds only were
negatively correlated with flow rate (e.g. PFOS; see Fig. 3), and no significant trend
was found between ΣPFASs and flow rate. Thus, the upstream site (Marnay), located
in a rural area between the urban centres of Troyes and Paris, appeared to be rather
under the combined influence of point and diffuse PFAS sources.
The average PFAS daily flow in the Seine River increased by a factor of about
80 between Marnay (upstream) and Triel (downstream), thereby providing evidence
of the major contribution of the Paris conurbation. The order of magnitude of the
annual total PFAS mass flow estimate was 10 and 800 kg year
À1 at Marnay and
Triel, respectively. These figures are in good agreement with those previously
determined in the centre of Paris (around 500 kg year
À1 ), especially considering
the methodological differences between the two studies (e.g. sampling frequency).
3.3 Transfer of PFASs to Biota in the Seine River Basin
Considering the current mechanistic understanding of PFAS bioaccumulation,
experimental studies are still needed to characterise the transfer of these chemicals
within food webs. In the PIREN-Seine programme, the bioaccumulation of PFASs
was investigated through several field studies that addressed this issue at different
levels of biological organisation. In particular, two model organisms were selected,
namely, (1) common chub, Leuciscus cephalus, a fish species widely used for water
quality monitoring, and (2) periphytic biofilm. Note that only the results obtained
with the latter are shown below.
Periphytic biofilms are mainly composed of both heterotrophic and autotrophic
microbial cells embedded in an exopolymer matrix comprising polysaccharides and
proteins [39]. At the interface of the water column and solid substrates such as bed
sediment, they may play a central role in controlling contaminant bioavailability and
transfer to consumers such as invertebrates or fish that graze on it.
Biofilm samples (3–4 per site, n ¼ 11) were collected on artificial support
(low-density polyethylene) colonised in situ. High detection frequencies
(80–100%) were observed for C 8 –C 12 PFCAs, PFHxS and PFOS. ∑PFASs were
in the range 4.3–33 ng g
À1 dw, and concentrations in biofilm samples largely
exceeded those of sediment samples [38]. The linear isomer of PFOS dominated
Contaminants of Emerging Concern in the Seine River Basin: Overview of. . .
365
correlation between its levels and those of major PFASs (e.g. PFOS).
During this monitoring study, the river flow rate was in the range 30–100 m
3 s
À1
at Marnay and 170–500 m
3 s
À1 at Triel. At each site, PFAS levels appeared constant
under stable hydrological conditions over short monitoring periods (e.g. 4 weeks),
while the molecular pattern remained unchanged for a given site. Seasonal variations
were examined at the water year scale, and the highest PFAS concentrations
appeared to be associated with low-flow conditions. At the downstream sites
(e.g. under the influence of the Paris conurbation), all major PFASs displayed
negative correlations with flow rate, strongly suggesting that point sources were
predominant. However, at the farthest upstream site, a few compounds only were
negatively correlated with flow rate (e.g. PFOS; see Fig. 3), and no significant trend
was found between ΣPFASs and flow rate. Thus, the upstream site (Marnay), located
in a rural area between the urban centres of Troyes and Paris, appeared to be rather
under the combined influence of point and diffuse PFAS sources.
The average PFAS daily flow in the Seine River increased by a factor of about
80 between Marnay (upstream) and Triel (downstream), thereby providing evidence
of the major contribution of the Paris conurbation. The order of magnitude of the
annual total PFAS mass flow estimate was 10 and 800 kg year
À1 at Marnay and
Triel, respectively. These figures are in good agreement with those previously
determined in the centre of Paris (around 500 kg year
À1 ), especially considering
the methodological differences between the two studies (e.g. sampling frequency).
3.3 Transfer of PFASs to Biota in the Seine River Basin
Considering the current mechanistic understanding of PFAS bioaccumulation,
experimental studies are still needed to characterise the transfer of these chemicals
within food webs. In the PIREN-Seine programme, the bioaccumulation of PFASs
was investigated through several field studies that addressed this issue at different
levels of biological organisation. In particular, two model organisms were selected,
namely, (1) common chub, Leuciscus cephalus, a fish species widely used for water
quality monitoring, and (2) periphytic biofilm. Note that only the results obtained
with the latter are shown below.
Periphytic biofilms are mainly composed of both heterotrophic and autotrophic
microbial cells embedded in an exopolymer matrix comprising polysaccharides and
proteins [39]. At the interface of the water column and solid substrates such as bed
sediment, they may play a central role in controlling contaminant bioavailability and
transfer to consumers such as invertebrates or fish that graze on it.
Biofilm samples (3–4 per site, n ¼ 11) were collected on artificial support
(low-density polyethylene) colonised in situ. High detection frequencies
(80–100%) were observed for C 8 –C 12 PFCAs, PFHxS and PFOS. ∑PFASs were
in the range 4.3–33 ng g
À1 dw, and concentrations in biofilm samples largely
exceeded those of sediment samples [38]. The linear isomer of PFOS dominated
Contaminants of Emerging Concern in the Seine River Basin: Overview of. . .
365