Heavy metals from heavy land use? Spatio-temporal patterns of urban runoff metal loads

• Published in: The Science of the total environment Vol. 817; p. 152855
• Main Authors: Taka, Maija, Sillanpää, Nora, Niemi, Tero, Warsta, Lassi, Kokkonen, Teemu, Setälä, Heikki
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.04.2022
• Subjects: cold; environment; Environmental Monitoring; Environmental Pollutants - analysis; exports; Finland; land use; Metal; Metals, Heavy - analysis; Pollutant export; pollutants; Rain; seasonal variation; Seasonality; Seasons; Stormwater; urban runoff; Urban water; urbanization; Water Pollutants, Chemical - analysis; watersheds; winter; Finland; Urban water; Stormwater; Metal; Pollutant export; Seasonality
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.152855

Urban hydrology is characterized by increased runoff and various pollutant sources. We studied the spatio-temporal patterns of stormwater metal (Al, V, Cr, Mn, Fe, Cu, Zn, and Pb) concentrations and loads in five urbanized and one rural catchment in Southern Finland. The two-year continuous monitoring revealed a non-linear seasonal relationship between catchment urban intensity and metal export. For runoff, seasonal variation decreased with increasing imperviousness. The most urbanized catchments experienced greatest temporal variation in metal concentrations: the annual Cu and Zn loads in most of the studied urbanized catchments were up to 86 times higher compared to the rural site, whereas Fe loads in the urbanized catchments were only circa 29% of the rural load. Total metal levels were highest in the winter, whereas the winter peak of dissolved metal concentrations was less pronounced. The collection of catchment characteristics explained well the total metal concentrations, whereas for the dissolved concentrations the explanatory power was weaker. Our catchment-scale analysis revealed a mosaic of mainly diffuse pollutant sources and calls for catchment-scale management designs. As urban metal export occurred across seasons, solutions that operate also in cold conditions are needed. [Display omitted] •Impact of urban land use on metal export was studied by monitoring six catchments.•Continuous monitoring, automatic sampling and statistical modelling were performed.•Urban intensity increased seasonality in concentrations, especially for Zn and Cu.•Highest total metal load occurred in winter; seasonality in dissolved metals was modest.