Ministry of Transport’s technical laboratory [52], but this approach was not used by
the river basin authorities.
From 1982 to 1992, the six French river basin agencies developed their own
monitoring strategies. The AESN turned to deposited sediments and rotating surveys
on 204 sediment stations. The bed sediment analyses were carried out on the fraction
<2 mm, i.e. including the sand fraction; unfortunately, ancillary data (e.g. % fine
fraction, aluminium), which would have allowed for grain-size effect correction,
were lacking, limiting data interpretation [53]. The official assessment of the metal
contamination (Ministère de l’environnement, 1985) stated: “one finds high concentrations only for copper: metals in sediments are low”. This statement ignored the
severe Cd and Hg contamination occurring at that time, gradually unveiled by the
PIREN-Seine programme in the 1990s using SPM analysis (e.g. [41]). In 2006,
the monitoring within the WFD considered the dissolved fraction only. It therefore
appears that the shifting strategies of micropollutant monitoring from 1971 to 2006
did not generate a general spatial and temporal assessment for contamination.
The sediment quality guidelines (SQG) that were or could have been used to
assess the contamination of micropollutants is another limitation to contamination
assessments. From 1971 to 2003, the guidelines concerning metal contamination
evolved considerably, depending on the media (e.g. unfiltered waters, agricultural
soils, dredged river materials, urban sludges). For a long time, the SQG did not exist
in France, until they were finalised in 2003 by the French water quality assessment
system, the SEQ-Eau [54]; sediment guidelines were therefore replaced by the WFD
criteria on waters in 2006. Metal contamination in rivers has not been assessed on a
national scale [55, 56], ignoring this critical issue.
3.3 Spatial Position of Sedimentary Archives Within the Seine
River Basin
The core position within river systems should be chosen depending on the expected
environmental information. In the Seine River basin, our coring strategy has considered very different positions of the intercepted basin area (Fig. 2). In addition, the
coring sites are geographically located in Fig. 1 [37]. Coring sites are listed in
Table 1 and greater detail can be found in the related articles. Cores taken directly
from the river bed by a diver in 1994 [57], which cannot be dated, presented sharp
contamination boundaries, suggesting erosion of previous deposits, are not used
here.
Our pristine or sub-pristine site (PRI) is a headwater reservoir, which intercepts
forested area. The medium impacts are studied on two floodplain cores, downstream
of the city of Troyes (URB), on the Upper Seine River, and in the middle part of the
Oise River (IND), a major Seine River tributary impacted by heavy industries. The
maximum impact is assessed on a core taken 20 km downstream of the centre of
Paris, in a navigated reach blocked by a sluice, which actually acts as a sediment trap
278
S. Ayrault et al.
the river basin authorities.
From 1982 to 1992, the six French river basin agencies developed their own
monitoring strategies. The AESN turned to deposited sediments and rotating surveys
on 204 sediment stations. The bed sediment analyses were carried out on the fraction
<2 mm, i.e. including the sand fraction; unfortunately, ancillary data (e.g. % fine
fraction, aluminium), which would have allowed for grain-size effect correction,
were lacking, limiting data interpretation [53]. The official assessment of the metal
contamination (Ministère de l’environnement, 1985) stated: “one finds high concentrations only for copper: metals in sediments are low”. This statement ignored the
severe Cd and Hg contamination occurring at that time, gradually unveiled by the
PIREN-Seine programme in the 1990s using SPM analysis (e.g. [41]). In 2006,
the monitoring within the WFD considered the dissolved fraction only. It therefore
appears that the shifting strategies of micropollutant monitoring from 1971 to 2006
did not generate a general spatial and temporal assessment for contamination.
The sediment quality guidelines (SQG) that were or could have been used to
assess the contamination of micropollutants is another limitation to contamination
assessments. From 1971 to 2003, the guidelines concerning metal contamination
evolved considerably, depending on the media (e.g. unfiltered waters, agricultural
soils, dredged river materials, urban sludges). For a long time, the SQG did not exist
in France, until they were finalised in 2003 by the French water quality assessment
system, the SEQ-Eau [54]; sediment guidelines were therefore replaced by the WFD
criteria on waters in 2006. Metal contamination in rivers has not been assessed on a
national scale [55, 56], ignoring this critical issue.
3.3 Spatial Position of Sedimentary Archives Within the Seine
River Basin
The core position within river systems should be chosen depending on the expected
environmental information. In the Seine River basin, our coring strategy has considered very different positions of the intercepted basin area (Fig. 2). In addition, the
coring sites are geographically located in Fig. 1 [37]. Coring sites are listed in
Table 1 and greater detail can be found in the related articles. Cores taken directly
from the river bed by a diver in 1994 [57], which cannot be dated, presented sharp
contamination boundaries, suggesting erosion of previous deposits, are not used
here.
Our pristine or sub-pristine site (PRI) is a headwater reservoir, which intercepts
forested area. The medium impacts are studied on two floodplain cores, downstream
of the city of Troyes (URB), on the Upper Seine River, and in the middle part of the
Oise River (IND), a major Seine River tributary impacted by heavy industries. The
maximum impact is assessed on a core taken 20 km downstream of the centre of
Paris, in a navigated reach blocked by a sluice, which actually acts as a sediment trap
278
S. Ayrault et al.