validation of the sediment archive approach: there is no significant PAH source
between Muids and Bouafles and the two OUT 1 cores should be identical. Actually,
the contamination pattern is very similar in the three cores (date of maximum
contamination, slope of contamination and decontamination), which proves the
reliability of the general trend. Small differences (less than 30%) in peak values
may stem from local patterns of sedimentation or sediment reworking.
Focusing on the 1970–2000 period, similar PAH decontamination rates are
observed in the outlet cores (OUT 1 and the EST), but second-order peaks in 1997
and 2004 showed by the EST core suggest a direct PAH source in the estuary. Also,
the decontamination rates for OUT 1 (3.0 Æ 0.3 mg kg
À1 year
À1 ) and for the
upstream site (PRI) (2.8 Æ 0.2 mg kg
À1 year
À1 ) are very close, representative of
the general decrease of PAH emissions at the scale of the Seine River basin, probably
linked to the decrease in coal consumption over this period (see Sect. 4.1).
6 Interbasin Comparison of Metal Contamination Trends
in Western European Rivers Using Sedimentary Archives
Interbasin comparisons can be performed at basin outlets which integrate the whole
catchment area (Fig. 1, F). The evolution of metals in nine rivers in Europe (Rhine
Volga and Danube, Mersey, Scheldt and Garonne) and in the Mississippi Delta
shows various levels of contamination, highly controlled by the river SPM contamination level [70]: the Mississippi had the lowest EFs and the highest dilution power
0
5
10
15
20
25
30
1960
1970
1980
1990
2000
2010
Dock (EST)
Bouafles 11
(OUT1)
0
20
40
60
80
100
120
1910
1930
1950
1970
1990
2010
Bouafles 10 (OUT1)
Pannecière (PRI)
Dock (EST)
Muids (OUT2)
Bouafles 11 (OUT1)
A
B
PAH contents (mg kg -1
)
Fig. 8 (a) Comparison between the sum of PAH contents (13 PAHs, mg kg
À1
), in the Seine River
sediment archives, downstream of Paris (Bouafles and Muids sediment (black, grey and open
triangles)) with the upstream sub-pristine reference (Pannecière reservoir sediment, open squares).
(b) Enlargement of the 1970–2010 period for basin outlet (Bouafles) and estuary (Dock). These
contents are also compared with estuary sediment (dark circles)
Sedimentary Archives Reveal the Concealed History of Micropollutant. . .
287
between Muids and Bouafles and the two OUT 1 cores should be identical. Actually,
the contamination pattern is very similar in the three cores (date of maximum
contamination, slope of contamination and decontamination), which proves the
reliability of the general trend. Small differences (less than 30%) in peak values
may stem from local patterns of sedimentation or sediment reworking.
Focusing on the 1970–2000 period, similar PAH decontamination rates are
observed in the outlet cores (OUT 1 and the EST), but second-order peaks in 1997
and 2004 showed by the EST core suggest a direct PAH source in the estuary. Also,
the decontamination rates for OUT 1 (3.0 Æ 0.3 mg kg
À1 year
À1 ) and for the
upstream site (PRI) (2.8 Æ 0.2 mg kg
À1 year
À1 ) are very close, representative of
the general decrease of PAH emissions at the scale of the Seine River basin, probably
linked to the decrease in coal consumption over this period (see Sect. 4.1).
6 Interbasin Comparison of Metal Contamination Trends
in Western European Rivers Using Sedimentary Archives
Interbasin comparisons can be performed at basin outlets which integrate the whole
catchment area (Fig. 1, F). The evolution of metals in nine rivers in Europe (Rhine
Volga and Danube, Mersey, Scheldt and Garonne) and in the Mississippi Delta
shows various levels of contamination, highly controlled by the river SPM contamination level [70]: the Mississippi had the lowest EFs and the highest dilution power
0
5
10
15
20
25
30
1960
1970
1980
1990
2000
2010
Dock (EST)
Bouafles 11
(OUT1)
0
20
40
60
80
100
120
1910
1930
1950
1970
1990
2010
Bouafles 10 (OUT1)
Pannecière (PRI)
Dock (EST)
Muids (OUT2)
Bouafles 11 (OUT1)
A
B
PAH contents (mg kg -1
)
Fig. 8 (a) Comparison between the sum of PAH contents (13 PAHs, mg kg
À1
), in the Seine River
sediment archives, downstream of Paris (Bouafles and Muids sediment (black, grey and open
triangles)) with the upstream sub-pristine reference (Pannecière reservoir sediment, open squares).
(b) Enlargement of the 1970–2010 period for basin outlet (Bouafles) and estuary (Dock). These
contents are also compared with estuary sediment (dark circles)
Sedimentary Archives Reveal the Concealed History of Micropollutant. . .
287