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TABLE 3 Concentration of butyltin compounds in sediment
from 2012 monitoring campaign. All results are
expressed as cations μg/kg d.w. (n.d. not detectable:
LOD TBT 1.2 μg/kg d.w., DBT 1.0 μg/kg d.w.,
MBT 0.8 μg/kg d.w; n.a, not available)
TABLE 4 Concentration of butyltin compounds in sediment
from 2013 monitoring campaign. All results are
expressed as cations μg/kg d.w. (n.d. not detectable: diuron, irgarol, dichlofluanid and chlorothalonil in all
LOD TBT 1.2 μg/kg d.w., DBT 1.0 μg/kg d.w.,
MBT 0.8 μg/kg d.w; n.a, not available)
the highest concentration, 2.4 ng/l, was found in the
Port of Favignana.
Clearly, only a passive sampling strategy can deal with
these concentrations, which are below the range of
routine methods of analysis.
Marine sediments still represent a problem in the long
term because they are a source of biocides for the water
column and biota even after the source of contamination Research & development
has been removed. The ability of marine sediments to
accumulate these compounds varies geographically
and geologically, according to the physicochemical
characteristics of the sediment (e.g., particle size and
organic carbon content). In particular, the restriction on
the use of TBT [11] has not yet led to TBT disappearance
in port areas, owing to its hydrophobicity and long
persistence (years) in sediments [12-14]. The TBT
contaminated sediment may continue to act as input
sources of TBT to overlying water by desorption or
resuspension of sediment-bound TBT in areas where
maritime traffic is intense.
The sediment samples collected in the MPA of Egadi
Islands clearly showed that butyltin compounds are
consistently detected only in port areas, even if at
low concentrations, in agreement with published
work for sediment collected in others Sicilian MPAs
[17]. Favignana, Levanzo and Marettimo ports showed
TBT concentrations ranging from 2 μg/kg to 4 μg/kg
(Tables 3 and 4) in both monitoring campaigns. Such
concentrations can be classified as the lowest among
the Italian port areas [18], always below the EQS of WFD
(5 μg/kg).
Conclusions
The analysis of seawater samples from different location
of Egadi Islands’ coastline indicates the absence of
the MPA locations studied.
The LOD of the analytical method is sufficient to state
that the presence of these biocides in the seawater is
well below the EQS defined by the WFD for diuron and
irgarol and the accepted international quality standards
for dichlofluanid and chlorothalonil.
TBT presence was not detected by grab sampling but
only using passive sampling, at concentration levels
higher than the extremely low EQS defined by the WFD
(<1 ng/l).
The results confirm that only passive sampling by SPMD
allows to measure TBT levels in the investigated areas
reaching quantification limits similar to the requested
EQS for this contaminant. TBT in sediments is only
detected in portual samples, with concentrations below
35EAI Energia, Ambiente e Innovazione 4/2015