Qualitative and quantitative study of various forms of phosphorous in storm and runoff waters in Toulouse (31) and Florensac (34), France

Storm water and runoff water has been analyzed. Phosphorous was measured in three forms: orthophosphates, hydrolysable phosphate (polyphosphates), and total phosphorous. The difference [total phosphorous] - {[hydrolysable phosphorous] + [orthophosphates]} gives a good idea of the organic origin phosphorous content. The qualitative and quantitative assessment of different phosphorous amounts enabled us to find that the irreducible part (organic soluble phosphorous) is about 23% of total phosphorous for runoff waters. Annual loads of orthophosphates, total phosphorous and so phosphorous known as organic were evaluated in the case of the motorway site at 3,3 kg of total phosphorous of which 0,60 kg of orthophosphates and 1,1 kg of soluble phosphorous known as organic for a catchment area of 1 hectare: motorway runoff waters are three times less loaded in total phosphorous than treated waters. As the urban site is much more loaded than a motorway site, it seems very important to supervise urban runoff waters.