POLLUTION OF URBAN RUNOFF WATERS BY HEAVY -METALS .2. SPECIATION

The speciation of cadmium, copper, lead and zinc has been studied in t he particulate and the dissolved fractions of urban runoff waters. Seq uential sampling has been performed during seven important rainfalls i n a same residential area in 1991 and 1992. In the dissolved fraction cadmium is essentially labile, copper is present as very stable comple x species, lead in stable slowly labile compounds whereas the lability of zinc species depends on the concentration of suspended solids. Par ticulate cadmium belongs to the ''exchangeable'' fraction, copper is l inked to the organic and residual fractions, lead to organic matter an d ''exchangeable'' fraction. Particulate zinc is shared between all fr actions.