Environmental Engineering Reference
In-Depth Information
Ausa-Corno River system in connection with the lagoon (Piani et al., 2005). In 1984, due to
application of law rules, a modern wastewater system treatment was installed; hence no more
inputs of Hg should have been released into the environment.
Covelli et al. (2009) stated that although uncontrolled Hg discharge from the CAP stopped,
the artificial channel connecting the industrial area to the upper river course is still an active
Hg source for the Marano lagoon environment.
During the application of the WFD 2000/60/EC, ARPA FVG investigated the distribution of
ten elements (Al, As, Cd, Cr, Fe, Hg, Ni, Pb, V and Zn) and of MeHg in surface sediment (0-
5 cm) collected in 28 stations distributed throughout the lagoon ecosystem.
In this monitoring plan some critical rose. However, where some elements exceed the
environmental quality standards (EQS) set by the WFD it should be stressed that these
represent, similarly to what reported for the adjacent Gulf of Trieste (Acquavita et al.,
2010b), the values underlying the region's natural lagoon geochemistry.
Previous data for As in the Gulf of Trieste showed a mean value of 7.4 µg g
-1
. In the lagoon
an average of value 8.9±1.7 µg g
-1
confirm that sediments can be considered as
uncontaminated (Francesconi & Edmonds, 1997). Moreover, only one site with 12.5 µg g
-1
exceeded the EQS (12.0 µg g
-1
) fixed by the law. For cadmium, the mean concentration
detected was equal to 0.17±0.04 µg g
-1
, with the whole set of data <0.30 µg g
-1
(EQS). The
element was significantly correlated with Fe (r=0.7940, p<0.05) and with Cr, Ni, Pb and Zn,
thus suggesting a common origin among these elements. Cr exceeds the EQS (50 µg g
-1
) only
in some stations (mean value 45.6±12.3 µg g
-1
. The Pearson matrix correlation showed a
distribution mainly influenced by mineralogy (Cr vs. Al, r=0.9255, p<0.05) rather than the
textural characteristics. A good correlation was also found with Zn and Pb. This latter
showed values quite low (16.9±4.7 µg g
-1
) if compared with those reported by Covelli &
Fontolan (1997) mean 55 µg g
-1
with a maximum of 144 µg g
-1
. Zn exhibits an extreme
variability also in uncontaminated sediments. In the Gulf of Trieste a wide range of values
from 8 to 213 µg g
-1
) is reported (Stefanini, 1971; Ministero dell'Ambiente, Servizio Difesa
Mare, 2005). Sediments of the lagoon showed a mean value of 68.5±19.4 µg g
-1
and the
significant correlation with Al (r=0.9003, p<0.05) suggest that there no significant
anthropogenic contribution. Ni always exceeds the EQS (30 µg g
-1
) proposed, thus ARPA
FVG will pose particular attention in the future monitoring. The data collected for Hg
confirms a range between 0.5 to 8.1 µg g
-1
, and clearly that Grado is more heavily polluted
than Marano. However, some spikes were detected at the Ausa-Corno River mouth (5.9 µg
g
-1
). MeHg contents were similar (2.0±0.9 ng g
-1
) to those already observed by Covelli et al.
(2008). Since the production of methylated Hg species depends on several factors (i. e., redox
state of the system, presence and quality of organic carbon, presence/absence of specific
bacteria solforiduttori) but not on total Hg contents, no correlation was found between the
two species (r=0.4343, p<0.5).
The concentration of Hg, Cd, Pb and benzo(a)pyrene are semiannually detected in bivalves
(
T. philippinarum
,
C. gallina
,
C. chione
and
M. galloprovincialis
) on the basis of Regulation (EC)
1881/2006, setting maximum levels for certain contaminants in foodstuffs. During the ten
years monitoring conducted by ARPA FVG (2001-2010), concentrations of these heavy
metals were always below the maximum level. In addition, benzo(a)pyrene levels were
always under limit of detection. The maximum level of MeHg in Manila clam from shell
farm in the Lagoon of Marano was 0.089 mg/kg wet weight. (Rampazzo et al., 2009).
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