Water quality of urban runoff in a small catchment area in Urriðaholt neighbourhood

Abstract

Urriðaholt is the first BREEAM (Building Research Establishment’s Environmental Assessment Method) certified neighborhood in Iceland. The main topic of this study was to examinate stormwater quality within a small residential area in Urriðaholt. The study area contains a divers set of Sustainable urban Drainage Systems (SuDS) which are used to control the quantity of runoff, manage the quality of runoff to prevent pollution, and create a sustain place for people and nature. The research is a small-scale study involving the collection of stormwater samples from Mosagata Street in Urriðaholt in four events spanning eight months in 2023. The sampling location was situated within a stormwater pipe that captures runoff from Mosagata and directs it to a swale. Samples were analyzed for conductivity, turbidity, total suspended solids (TSS) and heavy metals. One grab sample was analyzed for emerging pollutants such as PFAS. Comparative evaluations were then conducted regarding heavy metals. Each result was compared with that of a non-SuDS neighborhood in Iceland, called Grafarholt, and to the official regulatory limits for heavy metals pollution in surface water. Finally, comparative evaluations were conducted for PFAS concentration. The study aimed to encompass four distinct seasonal precipitation events (winter, spring, summer, and autumn). The first event, occurred on Jan. 20, involved rain on snow (RoS). Subsequent events included rainfall on Apr. 7 (spring), a summer rainfall event on Aug. 26, and an autumn rainfall event on Sept. 1. The result showed that the heavy metal pollution in Urriðaholt was highest in January and the heavy metal were generally higher in Urriðaholt than in Grafarholt. Also, the heavy metal concentration frequently exceeded environmental limits, suggesting a considerable degree of pollution in Urriðaholt. The location of the sampling proved to be confounding factor, as the autosampler was placed such that it collected water flowing directly from the street¬ rather than post SuDS–therefore potentially biasing toward higher concentration readings. According to existing studies, the PFAS concentration in Urriðaholt were very low.