Environmental Engineering Reference
In-Depth Information
rate studies used in regulatory procedures is confidential and unfortunately
is not available for peer-review. Summarizing the available information from
Table 1 it becomes evident, that for each of the compounds a broad range of
leaching rate estimates has been observed. Copper leaching rates usually are
higher than for other compounds. Leaching rates reported for TBT usually
are below regulatory implied values of 4
cm
2
day in some countries (USA,
Sweden). For the development of the Mam-Pec model [5] a set of default
leaching rates was proposed based on expertise available within the CEPE An-
tifouling Working Group: 50
µ
g
/
/
cm
2
cm
2
µ
g
/
/
day for copper, 4
µ
g
/
/
day for TBT
cm
2
(moving ships), and 2.5
µ
g
/
/
day for generic organic antifouling agents.
2.2
Underwater Surface Area
A second parameter in the emission estimation, the total antifouled underwa-
ter area of ships in a certain harbor area, depends on multiple factors, such as
shipping intensities, dimensions and shape of the various categories of ships,
cargo load, residence time in the harbor, and various other factors. Some
paint suppliers [24] have published rule of thumb formulas for estimation
of the underwater surface (
A
) and required amount of paint for recreational
ships, from simple dimensions such as length (
L
)orlengthatthewaterline
(
L
WL
)width(
W
)ordepth(
D
), as indicated in Table 2.
For commercial ships related formulas have been used to derive the esti-
mated surface area, which surprisingly show limited differences in average
estimated surface area. In the formula proposed by Willingham and Ja-
cobson [17] and used in the emission estimation module in the Mam-Pec
model [5] further simplifications were obtained by applying average ratios
between
L
and
W
(
W
as 14-15% of
L
)and
L
and
D
(
D
as 5% of
L
). In the
final ESD of the joint EU-OECD working group various approaches were com-
Table 2
Simple formulas for first estimation of average underwater area
Type of ship
Formula
Refs.
Recreational ships
motor-launch (low draught)
A
=
L
WL
(
W
+
D
)
[24]
sailing-yacht (intermediate draught)
A
=0.75
L
WL
(
W
+
D
)
[24]
sailing yacht (deep keel)
A
=0.5
L
WL
(
W
+
D
)
[24]
generic motor-boat
A
=0.85
L
WL
(
W
+
D
)
[45]
Commercial ships
New York Harbor
A
=
LW
1.3
[17]
Port of Rotterdam
A
=
L
(
W
+
D
)+
WD
[5]
Finnish harbors
A
=0.95
L
(0.8(
D
+
W
)+
W
)
[45]
