Emission Estimation and Chemical FateModelling of Antifoulants - Antifouling Paint Biocides - page 101

Emission Estimation and Chemical Fate Modelling
of Antifoulants

B. van Hattum 1 ( )·A.Baart 2 ·J.Boon 2

1 Institute for Environmental Studies, Vrije Universiteit, De Boelelaan 1087,
1081 HV Amsterdam, The Netherlands
[e-mail]
2 WL

|

Delft Hydraulics, P.O. Box 177, 2600 MH, Delft, The Netherlands
[e-mail], [e-mail]

1 I tr cti n ................................... 103

2 Emission Estimation .............................. 104

2.1 LeachingRate .................................. 105

2.2 UnderwaterSurfaceArea............................ 107

2.3 ShippingIntensity................................ 108

3 Water Exchange Mechanisms in Coastal Environments ........... 110

3.1 TidalExchange ................................. 110

3.2 WaterExchangebyaHorizontalEddy..................... 111

3.3 WaterExchangeduetoDensityCurrents ................... 112

4 Environmental Fate Models .......................... 115

5 cl si s a d tl ............................ 118

References ....................................... 118

Abstract Triggered by the debates around entry of force of the antifouling convention of
the International Maritime Organization and the upcoming ban of TBT, much progress
has been made during the last ten years in the field of the environmental risk assessment
of new and existing antifouling agents. In this chapter an overview is given of existing
exposure assessment models and two important areas of uncertainties, such as the hydro-
dynamic exchange and emission estimation in estuarine and coastal harbors. Apart from
tidal mixing, current and flow-induced horizontal mixing as well as density difference-
driven exchange processes and sedimentation have a major impact on the environmental
fate of antifouling compounds in coastal harbors. Existing generic screening models are
not capable of accounting for the complex hydrodynamics and interaction with chem-
ical fate processes. Considerable uncertainties are involved in the estimation of emissions,
based on the biocide leaching rate extrapolated from laboratory studies and affected by
temperature, salinity and pH, and shipping activity related parameters, i.e. number and
dimensions of ships, speed, underwater surface area, and the time spent in- port. Two re-
cent exposure assessment models for antifoulants in estuarine and marine environments,
REMA and Mam-Pec are discussed. The environmental emission scenarios linked to these
models were evaluated by a joint OECD-EU working group and formed the basis of the
current emission scenario document (ESD-PT21) adopted for application in the frame-
works of the Biocide Directive in Europe. The available models for antifoulants have been