Leaching Assessment of Non-Metal Roofs - Comparison of Field Studies and Laboratory Leaching Tests

Building products, like non-metal roofing materials, can contribute pollutants to stormwater. Laboratory leaching tests, particularly the dynamic surface leaching test (DSLT), are employed to evaluate the substance release, but are not designed to simulate field conditions. By comparing results from a DSLT and a 6-month field study for the same materials (clay tiles, concrete tiles, fiber cement sheets, bitumen shingles, treated wood shingles, and plastic tiles) and same analyzed inorganic and organic parameters we provided a basis for interpreting and translating the DSLT outcome to real weather conditions. The objective was to evaluate the reliability of the DSLT in predicting which parameter types are leached from non-metal roofing materials in the field, as well as its suitability for estimating the corresponding concentration levels. The comparison demonstrated that the DSLT reliably predicted more than 80% of pollutants released under environmental conditions, supporting its use for investigating new roofing materials or emerging pollutants to identify parameters contributing to stormwater pollution. Our results serve as a database for interpreting DSLT results and for developing and calibrating transfer models. However, no general pattern was observed between laboratory and field results: for fiber cement, clay and concrete tiles, the DSLT overestimated the concentrations; median concentrations exceeded those in the field, with factors of 2.6 to 115. For bitumen and wood shingles, the DSLT rather underestimated the substance release, resulting in median field concentrations that exceeded those in the laboratory by factors of 1.3 to 10.4. Consequently, transfer models must account for different surface properties of the materials.