Environmental Engineering Reference
In-Depth Information
Table 1). Hg levels recorded during late 90's in the Ligurian Sea (1875 ±
2633 µg/g, Capelli et al. 2008) and Adriatic Sea (1573 ± 5.3 µg/g, Storelli
and Marcotrigiano 2002) were also higher than the levels found in South
Atlantic Oceans (4 ± 2 µgg
-1
, Kunito et al. 2004, Student test: t = 4.62, df =
23,
P
< 0.01 and t = 1282.6626 df = 35,
P
< 0.01 respectively).
Our results are in agreement with previous review and papers (Aguilar
et al. 2002, Kakuschke and Prange 2007) where a global increase trend of
some heavy metals (Hg, Cu, Zd and Zn) was observed.
Persistent organic pollutants
With the advent of synthetic pesticides in the 1930s and 1940s, effects of DDT
and other pesticides were investigated in free-ranging and captive wildlife
(Rattner 2009). In the mid-1960s, Koeman and van Genderen (1966) reported,
for the fi rst time, the presence of organochlorine compound residues in the
tissues of a wild marine mammal. They found a few parts per million of
dieldrin and various forms of DDTs in blubber and fat of three common
seals (
Phoca viulina
) from the Wadden Sea. Soon after, Jensen and others
(1969), in a toxicological survey of Swedish marine fauna, were the fi rst to
detect polychlorinated biphenyls (PCBs) in the tissues of marine mammals,
this time in common seals (
Phoca vitulina
), grey seals (
Halichoerus grypus
)
and ringed seals (
Pusa hispida
). Since then, the number of references on the
subject has increased exponentially, reaching a ceiling of 30-40 refereed
articles per year in the 1990s (Aguilar and Borrell 1996).
As a global trend numerous works have revealed that marine mammals
from the northern hemisphere, which inhabit the mid-latitudes of Europe
and North America, show the greatest organochlorine loads whereas
tropical and equatorial areas of the northern hemisphere and all over the
southern hemisphere show low or very low loads. The polar regions of
both hemispheres showed the lowest concentrations of DDTs and PCBs,
although levels of HCHs, chlordanes and HCB were moderate to high in
the cold waters of the North Pacifi c. During recent decades, concentrations
have tended to decrease in the regions where pollution was initially high
but they have increased in regions located far from the pollution source as
a consequence of atmospheric transport and redistribution. It is expected
that the Arctic and, to a lesser extent, the Antarctic, will become major sinks
for organochlorines in future (Aguilar et al. 2002).
Organochlorine concentrations referred to in this paper were always
calculated on the basis of the sample content of extractable lipids (lipid
basis). This expression was preferred to that calculated on the basis of
the fresh weight of the sample because it corrects, at least partially, for
heterogeneity of nutritive condition and laboratory methods used for
lipid extraction. These two sources of heterogeneity are likely to introduce
additional variation in the determination of levels of organochlorine
