In the estuary site, the main Cd peak is observed around 1970 and a second one is
observed in the late 1970s. A third very sharp peak is observed in 1987. These peaks
are not observed in the OUT 1 core, suggesting that the 1970, 1975–1980 and 1987
estuary contamination episodes are due to very local events as the direct release of
phosphogypsum wastes from a fertiliser industry using Cd-rich ore. There has been
continuous dumping of “phosphogypsum residues” from the phosphoric acid industry, treating phosphorus ores at several locations in the estuary. Such waste materials
were first released in the upper estuary, over several decades, then in the middle
estuary and finally by barges in the outer estuary (Baie de Seine) with substantial
overspills. These dumpings were on the order of magnitude of the Seine River
sediment load (0.7 Mt. year
À1 on average): 1974 (0.4 Mt. year
À1 ) to 1987 (0.4
Mt. year
À1 ) with a maximum between 1980 and 1984 (1.6–2 Mt. year
À1 ) [60]. The
EST core reveals this long-term impact on many metals and phosphorus (P content
up to 5,000 mg kg
À1 in EST sediment vs 800 mg kg
À1 for the basin reference) and
for Y, La and lanthanides, U, Cd, As, Cr, Mo, Th, Ba, etc. [26]. All show a marked
increase of their contents in the estuarine core with the same temporality as phosphorus. This contamination source is estimated to account for 50–70% of these
elements’ contamination, reaching 90% for Y. This type of generalised contamination by a mineral chemistry industry has rarely been documented.
These contaminations were superimposed to those originating from the upstream
river basin: the EFs recorded in the estuarine sediments were extreme in the 1970s,
from 100 to 1,000 for many elements (Hg, Pb, Ag, Cd), making this waterbody one
of the most polluted in Europe [69].
5.2 Compared POP Contamination History: The PAH
Example
The comparison of the PAH contamination trends at five coring stations is illustrated
in Fig. 8 (Step E, Fig.1). The sub-pristine site (PRI, Fig. 2) is considered to be
representative of the non-impacted levels. Particle size analysis of the sediment core
reveals that the core bottom layers (dated between 1952 and 1955) correspond to a
mixture of soil and sediment, which is consistent with the reservoir’s impoundment
date (1949). Therefore, the analyses performed on layers deposited after 1955 are
considered as representative of the contamination trend of this area of the basin
where direct industrial and urban sources of contamination are minimal.
In the 1950s, the PRI PAH levels were below 0.2 mg kg
À1 . Then PAHs increased,
possibly due to atmospheric inputs. The maximum levels reached 10 mg kg
À1 (∑13
PAHs). In 1992, the contamination was still present at 2 mg kg
À1
, which is five times
less than at OUT 1 at the same time but remains high for this type of basin slightly
impacted by anthropogenic pressure.
The PAH contamination at the Seine River basin outlet was assessed in three
cores taken 10 km apart (two cores at OUT 1 and one core at OUT 2 ). This allows for a
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S. Ayrault et al.
observed in the late 1970s. A third very sharp peak is observed in 1987. These peaks
are not observed in the OUT 1 core, suggesting that the 1970, 1975–1980 and 1987
estuary contamination episodes are due to very local events as the direct release of
phosphogypsum wastes from a fertiliser industry using Cd-rich ore. There has been
continuous dumping of “phosphogypsum residues” from the phosphoric acid industry, treating phosphorus ores at several locations in the estuary. Such waste materials
were first released in the upper estuary, over several decades, then in the middle
estuary and finally by barges in the outer estuary (Baie de Seine) with substantial
overspills. These dumpings were on the order of magnitude of the Seine River
sediment load (0.7 Mt. year
À1 on average): 1974 (0.4 Mt. year
À1 ) to 1987 (0.4
Mt. year
À1 ) with a maximum between 1980 and 1984 (1.6–2 Mt. year
À1 ) [60]. The
EST core reveals this long-term impact on many metals and phosphorus (P content
up to 5,000 mg kg
À1 in EST sediment vs 800 mg kg
À1 for the basin reference) and
for Y, La and lanthanides, U, Cd, As, Cr, Mo, Th, Ba, etc. [26]. All show a marked
increase of their contents in the estuarine core with the same temporality as phosphorus. This contamination source is estimated to account for 50–70% of these
elements’ contamination, reaching 90% for Y. This type of generalised contamination by a mineral chemistry industry has rarely been documented.
These contaminations were superimposed to those originating from the upstream
river basin: the EFs recorded in the estuarine sediments were extreme in the 1970s,
from 100 to 1,000 for many elements (Hg, Pb, Ag, Cd), making this waterbody one
of the most polluted in Europe [69].
5.2 Compared POP Contamination History: The PAH
Example
The comparison of the PAH contamination trends at five coring stations is illustrated
in Fig. 8 (Step E, Fig.1). The sub-pristine site (PRI, Fig. 2) is considered to be
representative of the non-impacted levels. Particle size analysis of the sediment core
reveals that the core bottom layers (dated between 1952 and 1955) correspond to a
mixture of soil and sediment, which is consistent with the reservoir’s impoundment
date (1949). Therefore, the analyses performed on layers deposited after 1955 are
considered as representative of the contamination trend of this area of the basin
where direct industrial and urban sources of contamination are minimal.
In the 1950s, the PRI PAH levels were below 0.2 mg kg
À1 . Then PAHs increased,
possibly due to atmospheric inputs. The maximum levels reached 10 mg kg
À1 (∑13
PAHs). In 1992, the contamination was still present at 2 mg kg
À1
, which is five times
less than at OUT 1 at the same time but remains high for this type of basin slightly
impacted by anthropogenic pressure.
The PAH contamination at the Seine River basin outlet was assessed in three
cores taken 10 km apart (two cores at OUT 1 and one core at OUT 2 ). This allows for a
286
S. Ayrault et al.