3.2 Dynamics of PFASs in the Seine River
A longitudinal upstream–downstream concentration gradient was previously
observed for various contaminants (e.g. PAHs, organohalogens, phthalates) in
relation to the impact of the Greater Paris conurbation [33]. The dynamics of selected
PFASs in the Seine River were investigated using a dual strategy: (1) the time trends
and mass flows were determined for a single study site during a flood cycle, and
(2) both the seasonal and spatial fluctuations at the water year scale were studied at
the regional scale.
Changes in river flow may have a large impact on the concentration of chemical
point sources, and coordinating water quality monitoring with the analysis of
hydrological conditions is essential to understand the fate and transport of trace
organics in surface waters [34]. Thus, water samples were first collected weekly over
a 4-month period in 2011 (January–May), in the centre of Paris (Quai d’Austerlitz),
right at the heart of the conurbation. This sampling site was deemed representative of
the impact on water bodies of urban inputs. Selected PFASs, including C 4 –C 14
carboxylates (PFCAs) and C 4 –C 10 sulfonates (PFSAs), were analysed in both the
particulate and dissolved phases of water samples using liquid chromatography
coupled with tandem mass spectrometry (LC-MS/MS) [32].
Over the period considered, the river flow rate ranged between 150 and
640 m
3 s
À1 , and several spate events were recorded. Suspended solid (SS) levels
were generally low, in good agreement with previous reports [4]; these levels
exhibited large variations (3–60 mg L
À1 ) and were strongly correlated with the
river flow rate [32]. Among the targeted PFASs, perfluorooctane sulfonate (PFOS)
and perfluorohexane sulfonate (PFHxS) were the dominant compounds. ∑PFASs
varied between 30 and 90 ng L
À1 (average, 55 ng L
À1 ), and PFASs were mainly
found in the dissolved phase due to the relatively low SS levels. These PFAS
concentrations were in good agreement with those determined in the Seine downstream of Paris during low-flow periods [35] and were close to the average value
determined for 122 watercourses at the European level (59 ng L
À1 ) [36], which
suggests that the Seine River in Paris is not a hotspot of contamination of PFASs by
European standards. However, the median ∑PFASs for this site was approximately
three times higher than that determined at a nationwide level in France
(i.e. 7.8 ng L
À1 ) [31]. In addition, PFOS levels (10–40 ng L
À1 ) were lower than
the maximum allowable concentration (EQS-MAC, 35 μg L
À1 ) but consistently
above the environmental quality standard expressed as an annual average value
(EQS-MA) of 0.65 ng L
À1 in Directive 2013/39/EU.
∑PFASs and the river flow rate were negatively correlated, which suggests a
dilution of the contributions from point sources when flow increases. However, the
selected linear model explained only 25% of the observed variation of concentration.
Other contributions via the sewerage network or urban runoff are therefore likely to
influence the levels observed in the Seine River. In addition, the PFHpA to PFOA
concentration ratio, indicative of the contribution of direct (i.e. non-atmospheric)
inputs [37], was also positively correlated with flow rate. This suggests an increase
Contaminants of Emerging Concern in the Seine River Basin: Overview of. . .
363
A longitudinal upstream–downstream concentration gradient was previously
observed for various contaminants (e.g. PAHs, organohalogens, phthalates) in
relation to the impact of the Greater Paris conurbation [33]. The dynamics of selected
PFASs in the Seine River were investigated using a dual strategy: (1) the time trends
and mass flows were determined for a single study site during a flood cycle, and
(2) both the seasonal and spatial fluctuations at the water year scale were studied at
the regional scale.
Changes in river flow may have a large impact on the concentration of chemical
point sources, and coordinating water quality monitoring with the analysis of
hydrological conditions is essential to understand the fate and transport of trace
organics in surface waters [34]. Thus, water samples were first collected weekly over
a 4-month period in 2011 (January–May), in the centre of Paris (Quai d’Austerlitz),
right at the heart of the conurbation. This sampling site was deemed representative of
the impact on water bodies of urban inputs. Selected PFASs, including C 4 –C 14
carboxylates (PFCAs) and C 4 –C 10 sulfonates (PFSAs), were analysed in both the
particulate and dissolved phases of water samples using liquid chromatography
coupled with tandem mass spectrometry (LC-MS/MS) [32].
Over the period considered, the river flow rate ranged between 150 and
640 m
3 s
À1 , and several spate events were recorded. Suspended solid (SS) levels
were generally low, in good agreement with previous reports [4]; these levels
exhibited large variations (3–60 mg L
À1 ) and were strongly correlated with the
river flow rate [32]. Among the targeted PFASs, perfluorooctane sulfonate (PFOS)
and perfluorohexane sulfonate (PFHxS) were the dominant compounds. ∑PFASs
varied between 30 and 90 ng L
À1 (average, 55 ng L
À1 ), and PFASs were mainly
found in the dissolved phase due to the relatively low SS levels. These PFAS
concentrations were in good agreement with those determined in the Seine downstream of Paris during low-flow periods [35] and were close to the average value
determined for 122 watercourses at the European level (59 ng L
À1 ) [36], which
suggests that the Seine River in Paris is not a hotspot of contamination of PFASs by
European standards. However, the median ∑PFASs for this site was approximately
three times higher than that determined at a nationwide level in France
(i.e. 7.8 ng L
À1 ) [31]. In addition, PFOS levels (10–40 ng L
À1 ) were lower than
the maximum allowable concentration (EQS-MAC, 35 μg L
À1 ) but consistently
above the environmental quality standard expressed as an annual average value
(EQS-MA) of 0.65 ng L
À1 in Directive 2013/39/EU.
∑PFASs and the river flow rate were negatively correlated, which suggests a
dilution of the contributions from point sources when flow increases. However, the
selected linear model explained only 25% of the observed variation of concentration.
Other contributions via the sewerage network or urban runoff are therefore likely to
influence the levels observed in the Seine River. In addition, the PFHpA to PFOA
concentration ratio, indicative of the contribution of direct (i.e. non-atmospheric)
inputs [37], was also positively correlated with flow rate. This suggests an increase
Contaminants of Emerging Concern in the Seine River Basin: Overview of. . .
363