Bituminous Roof Sealing Membranes as Major Sources of the Herbicide (<i>R</i>,<i>S</i>)-Mecoprop in Roof Runoff Waters:  Potential Contamination of Groundwater and Surface Waters

Abstract

During a field study on the occurrence and behavior of pesticides during artificial infiltration of roof runoff, the herbicide R -mecoprop and its S -enantiomer were detected in roof runoff in much higher concentrations (up to 500 μg/L) than in the corresponding rainwater. We hypothesized in the foregoing paper in this issue that the root protection 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 runoff from different flat roofs were investigated. It is shown that concentrations of a few micrograms per liter at an R to S enantiomeric ratio (ER) of 0.8−1.4 can permanently be expected in roof runoff from flat roofs which have Preventol B 2 containing sealing membranes incorporated. The major factors that govern the release of ( R, S )-mecoprop are the type of bituminous sheet, the biological activity, and the intensity of the applied rooftop greening. A field study in the Greifensee catchment area revealed that wastewater treatment plants (WWTPs) are a major source of ( R, S )-mecoprop which most probably originates from construction materials equipped with Preventol B 2. A comparison of the ( R, S )-mecoprop loads from flat roofs and from agricultural applications into surface waters revealed that these loads were in the same order of magnitude.