En utvärdering av källor som bidrar till förorening av dagvatten

Urban runoff is a significant pathway for the transport of diverse substances from the urban environment to receiving water bodies. Many of these substances are pollutants of environmental concern with potentially harmful effects on aquatic life. Detailed knowledge of the sources of pollutants entering stormwater runoff is needed to mitigate these effects.The overall aim of this doctoral thesis is therefore to provide new knowledge on the sources contributing to urban runoff pollution and to evaluate the specific contributions of micropollutants from two known major sources: building and structure surface materials, and vehicular activities. The work presented herein also (i) identifies pollutants that are expected to occur in runoff from buildings and other structure surfaces in the urban environment as well as in runoff from the road environment, (ii) estimates the concentrations of these pollutants released into runoff, and (iii) evaluates methods for identifying sources contributing to the pollution of urban stormwater runoff. The novel work presented in the thesis includes a critical review of the literature on sources contributing to urban runoff pollution, laboratory leaching tests and open-air sampling of pilot panels of building and structure surface materials, and field sampling of urban roadside snow. The literature review was not restricted in terms of type of pollution, while the experiments focused on selected metals and organic micropollutants including phthalates, alkylphenols, bisphenol A, and polycyclic aromatic hydrocarbons (PAHs). According to the literature review, atmospheric deposition, vehicular activities, and metallic building envelopes are the major pollution sources in the urban environment and have been studied far more extensively than other sources. Moreover, their dominance is likely to continue given their central roles in urban environments. The experimental results confirmed that vehicular activities were sources of octylphenols, bisphenol A, and phthalates as well as the metal(loid)s Sb and W, both of which were rarely determined in previous studies on urban runoff. Building and structure surface materials such as copper sheets, zinc sheets, and polyvinyl chloride (PVC) roofing membranes were found to release Cu, Zn, nonylphenols, and phthalates. Among alkylphenols, nonylphenols were predominantly found in building surface runoff while octylphenols occurred predominantly in roadside snow. Metals occurred more commonly in dissolved (<0.45 μm) form in building surface runoff than in roadside snow, where metals were mainly attached to particles. A comparison of methods for identifying building surface materials contributing to runoff pollution showed that laboratory leaching tests were generally effective for source identification but not for estimating concentrations in actual runoff, whereas open-air pilot studies were resource-intensive but give results that agree well with analyses of real runoff. In addition, the release of pollutants from building surface materials subjected to in-situ ageing was investigated and the water quality of rainwater-induced runoff was compared to that of snowmelt-induced runoff; neither of these issues were adequately addressed in the previous literature. These studies showed that pollutant concentrations were generally higher in rain runoff than in snowmelt runoff and that pollutant releases from most materials and substances exhibited no decreasing or increasing trend over time. However, the release of nonylphenols from one of the PVCs did decrease over time, possibly because of washing out and material ageing