In modelling the fate and transport of heavy metals, the sorption processes
, through the distribution coefficient, are applied to determine the amount
of sorbed and dissolved fractions. Usually, these distribution coefficient
s are assumed to depend only on suspended sediment interactions. In estuari
es, however, observations indicate that dissolved concentrations increase w
ith salinity. It is hypothesized that salt competes for binding sites, lead
ing to lower distribution coefficients. To study the fate and transport of
heavy metals in an estuarine environment, a two-dimensional finite volume,
depth-averaged toxic transport model has been developed. The distribution c
oefficients are approximated as a function of sodium activity or salt conce
ntration. Other model parameters are obtained from a recently developed hyd
rodynamic model, salt transport and cohesive sediment transport modules. Th
e model has been applied to the Scheldt Estuary and the results for both so
rbed and dissolved heavy metal concentrations agree fairly well with measur
ed data, indicating that under estuarine mixing, salt concentration is an i
mportant factor affecting the fate and transport of heavy metals. Copyright
(C) 1999 John Wiley & Sons, Ltd.