Keywords Contaminant trajectories, Emerging pollutants, Metals, Persistent
organic pollutants, Sediment archives
1 Introduction
Sedimentary archives have been used since the early 1970s to reconstruct the past
contaminant contents of river particles settled in the river continuum, particularly
in the United States. They were used to reconstruct the past contamination of
the Chesapeake Bay [1], the progressive eutrophication of the Great Lakes and
their gradual contamination with mercury [2] and polychlorinated biphenyls
(PCBs) [3]. Cores taken in the Mississippi River Delta integrate the contamination
over 3.2 M km
2 [4, 5] for trace metals, polycyclic aromatic hydrocarbons (PAHs)
and chlorinated organic compounds. Their analysis demonstrated that the lead
(Pb) profile showed a doubling of concentrations from 1900 to 1970, followed by
a significant decline of Pb contamination over this wide territory. These trends could
not be demonstrated by the regulatory monitoring performed on filtered and unfiltered (whole-water) water sample pairs [6]: the analysis of a single core provided
more valuable results on river contamination than 15 years of water quality surveys
over the entire United States. To overcome the difficulties raised by this protocol,
between 1991 and 2015, the United States Geological Survey (USGS) added the
analysis of fine deposited river sediments to regulatory monitoring (Horowitz, pers.
comm.) The sedimentary archive approach was then recommended by the National
Oceanic and Atmospheric Administration (NOAA) [7].
In Europe, sedimentary archives were also considered in the 1970s in Alpine
lakes [8] and the Rhine River delta [9]. In this basin, contamination for As, Cd, Cr,
Cu, Hg, Ni, Pb and Zn started before 1920 and peaked in the 1970s, a trend
confirmed later [10]. Most of these studies focused on the evolution of contaminant
levels, generally at the river mouth or in deltas, therefore integrating the whole river
basin.
In France, sediment archive analysis started with the metal contamination in the
Garonne estuary (Gironde) [11] and then in the Lot reservoirs, a tributary of the
Garonne, downstream of a former zinc mining site, which was the major source of
Zn and Cd for this system [12, 13]. More recently, sediment cores have been
analysed in the Seine basin [14, 15], the Loire basin [16] and the Rhône basin
[17, 18]. In addition to trace elements and persistent organic pollutants (POPs),
pharmaceutical products have been analysed more recently [19, 20]. This brief and
non-comprehensive review does not cover the many lake cores analysed in France
[21]. At all French sites, the sediment archives reveal the evolution of micropollutant
contamination for the period when their regulatory analyses in water were limited or
insufficient (<1990s) and long before, over periods that may exceed 100 years.
Apart from some notable exceptions, the archive-based studies, conducted by
geochemists, have rarely documented the river basin history, which is needed to
Sedimentary Archives Reveal the Concealed History of Micropollutant. . .
271
organic pollutants, Sediment archives
1 Introduction
Sedimentary archives have been used since the early 1970s to reconstruct the past
contaminant contents of river particles settled in the river continuum, particularly
in the United States. They were used to reconstruct the past contamination of
the Chesapeake Bay [1], the progressive eutrophication of the Great Lakes and
their gradual contamination with mercury [2] and polychlorinated biphenyls
(PCBs) [3]. Cores taken in the Mississippi River Delta integrate the contamination
over 3.2 M km
2 [4, 5] for trace metals, polycyclic aromatic hydrocarbons (PAHs)
and chlorinated organic compounds. Their analysis demonstrated that the lead
(Pb) profile showed a doubling of concentrations from 1900 to 1970, followed by
a significant decline of Pb contamination over this wide territory. These trends could
not be demonstrated by the regulatory monitoring performed on filtered and unfiltered (whole-water) water sample pairs [6]: the analysis of a single core provided
more valuable results on river contamination than 15 years of water quality surveys
over the entire United States. To overcome the difficulties raised by this protocol,
between 1991 and 2015, the United States Geological Survey (USGS) added the
analysis of fine deposited river sediments to regulatory monitoring (Horowitz, pers.
comm.) The sedimentary archive approach was then recommended by the National
Oceanic and Atmospheric Administration (NOAA) [7].
In Europe, sedimentary archives were also considered in the 1970s in Alpine
lakes [8] and the Rhine River delta [9]. In this basin, contamination for As, Cd, Cr,
Cu, Hg, Ni, Pb and Zn started before 1920 and peaked in the 1970s, a trend
confirmed later [10]. Most of these studies focused on the evolution of contaminant
levels, generally at the river mouth or in deltas, therefore integrating the whole river
basin.
In France, sediment archive analysis started with the metal contamination in the
Garonne estuary (Gironde) [11] and then in the Lot reservoirs, a tributary of the
Garonne, downstream of a former zinc mining site, which was the major source of
Zn and Cd for this system [12, 13]. More recently, sediment cores have been
analysed in the Seine basin [14, 15], the Loire basin [16] and the Rhône basin
[17, 18]. In addition to trace elements and persistent organic pollutants (POPs),
pharmaceutical products have been analysed more recently [19, 20]. This brief and
non-comprehensive review does not cover the many lake cores analysed in France
[21]. At all French sites, the sediment archives reveal the evolution of micropollutant
contamination for the period when their regulatory analyses in water were limited or
insufficient (<1990s) and long before, over periods that may exceed 100 years.
Apart from some notable exceptions, the archive-based studies, conducted by
geochemists, have rarely documented the river basin history, which is needed to
Sedimentary Archives Reveal the Concealed History of Micropollutant. . .
271