In a recently published study, PhD student Alexandra Müller compared three methods for the identification of building surface materials as sources of metals, phthalates and nonylphenols in runoff: a screening of the actual substances found in the material composition, laboratory leaching experiments with synthetic rainwater, and pilot-scaled experiments in outdoor environment. Nine materials commonly applied to roofs, facades, or other structures in the urban environments were included in the study: metal sheets of zinc, copper, galvanised steel, coated corrugated steel and stainless steel; and, four different roofing membranes of bitumen as well as PVC. The studied methods cover a wide span of e.g., financial and labour resources, and resemblance to real conditions.
The results from the study showed that all three methods may be useful for the identification or pollution sources, and that some benefits may be achieved by integrated use of more than one method. The material screening, being relatively resource effective, risks to identify substances present in the material formulation, but not likely to release in contact with water. The laboratory leaching with synthetic rainwater was successful in identifying the sources of pollutants released, with the exception of phthalates, but are not suitable for estimations of concentrations in actual runoff. The pilot-scaled experiments in outdoor environment was thought to correspond well to runoff from actual buildings and structure surfaces, both in terms of the identified substances and the estimation of concentrations, but was high-demanding in terms of financial and labour resources. Moreover, studies in the outdoor environment need to be corrected to the contribution of pollutants from atmospheric deposition. Future studies for identification of sources of stormwater pollution should carefully consider the choice of methods with respect to the study objectives as well as available resources.