Environmental Engineering Reference
In-Depth Information
instance for copper, processes such as sorption, speciation, and redox reac-
tions have a prominent role in the fraction of freely bioavailable and poten-
tially toxic copper ions [1].
Among the trace element mechanisms, partitioning and rate constants are
highly element specific, and may depend strongly on the physico-chemical
speciation. The speciation is highly dependent on environmental factors,
such as salinity, pH, pE, particulate matter, presence and nature of ligand-
substrates. In contrast to the category of neutral hydrophobic compounds
there are no simple and generic relationships with which partitioning and
rate constants can be estimated. Only a few of the available generic chemical
fate models, such as EXAMS [2] and DELWAQ [3] allow for the evaluation
of speciation in the chemical fate of trace metals. In environments with low
exchange rates or pseudo stagnant conditions the chemical and biological
processes are likely to become more important. Especially in energy rich
marine environments, such as the coastal areas where most of the main har-
bors are situated, the hydrodynamic transport and mixing processes of water
masses and sedimentation tend to have a major impact on the environmental
fate of chemicals. In this chapter some of the basic principles of hydrody-
namic exchange processes in estuarine harbors have been described. As this
phenomenon is not properly addressed in most regulatory screening-type
models (Sect. 4), special models such as REMA [4] and Mam-Pec [5] have
been developed for the prediction of the chemical fate of antifoulants. The
environmental conditions and emission estimation procedures (Sect. 2) in
these models have recently been evaluated by a joint EU and OECD working
group [6], and were the basis of the recommended default emission and expo-
sure scenarios recommended for regulatory admission procedures in OECD
countries.
2
Emission Estimation
Emissions of antifouling products in harbors originate mainly from leaching
of the underwater paints and to a lesser extent from maintenance operations.
For large commercial harbors the emissions due to leaching dominate and
are usually estimated as the product of a leaching rate (LR in mg
cm
2
day)
andthetotalantifouledunderwaterarea(
A
in m
2
). In various modelling
studies [5] and the recently adopted emission scenario document (ESD) for
antifouling products by a joint EU-OECD working group [6] the total emis-
sions (
E
tot
in g d
-1
) in a harbor are estimated according to Eq. 1 or similar
formulas.
E
tot
=
i
=1-
n
/
/
(
A
i
∗
N
ib
∗
F
i
∗
LR
b
)+
i
=1-
n
(
A
i
∗
N
im
∗
F
i
∗
LR
m
) gd
-1
)
(1)
