Environmental Engineering Reference
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was a slight increase (FD= 0.7). Zn and Cu, also showed a steady increase
in their concentrations until the late 90's followed with a slight decrease
by 2002 (FD = 0.1) in the same coastal regions. Cd concentration showed
an important decrease in their levels (FD = 7) from 1994 to 1999 followed
by an increase (FD = 0.1) towards 2002. As a general trend, once again, Cd
showed increased levels in the Mediterranean Sea (FD = 0.5).
The North Sea ecosystem was highly loaded with both organic and
metal pollutants introduced by various anthropogenic activities within the
coastal zones in the past century. Until the middle of the 80's the yearly
input of metal pollution was around 340 tn of Cd, 75 tn of Hg and 11.000
tn of Pb (Rachor and Rühl 1990, Kakuschke and Prange 2007). Currently
several studies have shown a diminishing trend in the input of pollutants
into the ecosystem, this general tendency was especially confi rmed for
metal pollutants (Kakuschke and Prange 2007). The Quality Status Report
of the Trilateral Monitoring and Assessment Program (TMAP) concluded
that major reductions in the input and the concentrations of metals in the
Wadden Sea occurred mainly in the late 1980s until the early 1990s and
continued moderately until 2002 (Kakuschke and Prange 2007). Our results
are in agreement with those fi ndings, FD show an increase from the late
70's and 80's (FD Hg = 0.3, Cu = 0.4, Zn = 0.2). The Hg concentration trend
continued with a steady decline in its levels in the North Sea (FD Hg
1993-2001
=
1.7, Table 1, Fig 1). Whereas Cu and Zn showed an increase in their levels
for late 80's until 2001 (FD
1989-2001
Cu= 0.7, Zn = 0.6). Finally, Hg levels
exhibited an increase (FD = 0.2) in North Atlantic Ocean (Gulf of Mexico,
France, Portugal, Spain, Grand Britain coasts, Iceland and Norway) during
late 60's to 90's followed by a sharp decrease during early 90's to 2000 (FD
= 26.3) and a smooth increasing trend from 2000 to 2003 (FD = 0.3).
Extensive studies of metal concentrations in cetaceans have been
carried out in the Northern Hemisphere but relatively little is known about
contaminant levels in Southern Hemisphere cetaceans. Hg levels showed an
increase during 90's decade (FD
1988-1996
= 0.2) in the Southern Atlantic Ocean
(Argentina, Australia, Brazil and China coasts). This trend was followed by
a sharp decrease up to 2000 (FD
1996-2000
= 13) and a mild increase until 2004
(FD
2000-2004
= 0.5). Cu, Cd and Zn showed similar trends, a decrease from 1988
to late 90's (FD Cd= 3.6, Cu = 1.4, Zn = 2.2). The concentrations of Cd and
Zn continued that trend by increasing their levels to the present (FD Cd =
0.2, Zn = 0.9). Meanwhile Cu levels tend to decrease (FD = 1.2).
The average levels of Hg (liver) of the Northern Hemisphere (North
and Irish sea) were higher than those found in the Southern Hemisphere
(South Atlantic Ocean: Brazil and Uruguay) (Student test: SAO vs North
seal: t = 2.67, df = 35,
P
= 0.01; SAO vs Irish Sea: t = 2.3, df = 57,
P
= 0.02;