BITUMINOUS ROOF SEALING MEMBRANES AS MAJOR SOURCES OF THE HERBICIDE (R,S)-MECOPROP IN ROOF RUNOFF WATERS - POTENTIAL CONTAMINATION OF GROUNDWATER AND SURFACE WATERS

During a field study on the occurrence and behavior of pesticides duri ng artificial infiltration of roof runoff, the herbicide R-mecoprop an d its S-enantiomer were detected in roof runoff in much higher concent rations (up to 500 mu g/L) than in the corresponding rainwater. We hyp othesized in the foregoing paper in this issue that the root protectio n agent Preventol B 2 in the bituminous sheets, which is a bi-ester of (R,S)-mecoprop (see Figure 1), was the source of these compounds. In this work, the occurrence and variations of (R,S)-mecoprop in the run off from different flat roofs were investigated. It is sh own that con centrations of a few micrograms per liter at an R to S enantiomeric ra tio (ER) of 0.8-1.4 can permanently be expected in roof runoff from fl at roofs which have Preventol B 2 containing sealing membranes incorpo rated. The major factors that govern the release of (R,S)mecoprop are the type of bituminous sheet, the biological activity, and the intensi ty of the applied rooftop greening. A field study in the Greifensee ca tchment area revealed that wastewater treatment plants (WWTPs) are a m ajor source of (R,S)-mecoprop which most probably originates from cons truction materials equipped with Preventol B 2. A comparison of the (R ,S)-mecoprop loads from fiat roofs and from agricultural applications into surface waters revealed that these loads were in the same order o f magnitude.