Analysis of the parameters relevant for metal runoff estimation from zinc roofing - A test bed approach in Paris conurbation

Roofing materials are known to be a significant source of urban runoff metallic contamination. In order to quantify annual runoff rates involved, three types of zinc have been tested during one year in two different atmospheric environments within Paris conurbation. Fourteen metallic species have been analysed in runoff waters, highlighting different profiles of contamination according to the material. Concerning zinc emissions, annual runoff rates evaluated are 3.8, 4.1 and 2.2 g Zn.m-2 yr-1, respectively for new natural zinc, old natural zinc and new Anthra zinc. Variations of monthly zinc runoff rates from one sampling period to another appeared to be strongly correlated to the rain depth but not to atmospheric parameters. Zinc runoff rates were not observed to decrease over the exposure time. Three attempts of zinc runoff loads modelling were realized, showing that a model taking in account exposure duration, corresponding rainfall and a parameter considering previous exposure period can give satisfactory results, for different successive exposure periods.