Grain-size partitioning of butyltins in estuarine and coastal sediments

Grain-size partitioning of tributyltin (TBT) and its degradation products di- and monobutyltin (DBT and MBT) in coastal sediments revealed a strong tendency on the part of these compounds to adsorb on to detrital fragments (algal and leaf debris mixed with light mineral particles). Butyltins have been weakly detected in sands washed from these debris, a finding which underlined the need to separate both fractions (sands and debris) for an accurate assessment of the grain size partitioning. In debris-free sediments, butyltins were mostly detected in the silt/clay fraction. It was found necessary to consider the total amount of butyltins in each fraction, and hence the relative proportion of each fraction, in order accurately to assess the grain-size partitioning of these compounds. At this stage however, it was difficult to determine whether butyltins were only adsorbed on the surface of particles (high adsorption capacities in organic debris and silt/clays) or strongly bound to organic matter.