Stormwater quality and land use impacts Storm water expert meeting, 11th December 2014, Turku Marjo Valtanen Department of Environmental Sciences, University of Helsinki 17.12.2014 1
Stormwater quality the concept CONCENTRATIONS Varying continuously LOADS Concentrations x runoff volume -> volume has a great role E.g. annual unit loads (kg/km²/year) May reflect better the overall pollution potential
Stormwater quality and land use characteristics Land use type -> pollutant sources -> concentrations Activities -> e.g. snow removal, deicing, traffic density, population Imperviousness -> runoff volumes and intensitites -> pollutant loads Weather -> runoff volumes and intensitites -> pollutant loads www.uusisuomi.fi www.yle.fi
Atmosphere Traffic Industry Rooftops Housing Construction sites Grass areas Others Nitrogen x x x x x x x phosphorus x x x x x x x Solids x x x x x x x Sulphate x x Sulphur oxides x x Chloride x x Heavy metals x x x x x PAHs x x x x VOCs x x Oils and hydrocarbons x x x x Pesticides x x x x Coliform bacteria x x x Min 5 common sources for the pollutant (City of Edmond, edmondok.com)
Pollutant concentration variation 17.12.2014 5
Cold climate considerations 40 % of the 40% of the annual precipitation falls as snow Spring thaw (Talouselama.fi) Freezed and/or saturated soils during cold months Increased pollutant emissions during wintry months Snow ploughing and transportation Yle.fi (helsinginuutiset.fi)
LOW, residential 19 % The study catchments HIGH, city centre 89% INTERMEDIATE, city centre 62 %
Pollutant even mean concentrations max 3000 3500 max 3000 3500 max 17200 3100 High concentration -> requires treatment Middle level concentration (Stockholm Vatten 2001)
Pollutant event mean concentrations No threshold values set Ei asetetua raja-arvoa max 1800 1200 max 1800 1200 75 max 1500 1100 max 1800 1200 Concentrations below middle level max 580 240 max 580 max 580 240 240 max 100 92 max 90 120 High concentration -> requires treatment Middle level concentration
Dissolved vs. particulate bound metals Proportion Liuenneiden of the metallien dissolved osuus metals (% of kokonaismetalleista) the total metals (%) Cr Mn Ni Zn Cu Keskusta City centre 8989% % 21 14 21 33 20 Kylmä kausi Keskusta City centre 62 62 % 12 9.6 38 31 17 Asuinalue Residential 1919% % 46 23 61 98 61 Keskusta City centre 8989% % 38 9.0 44 61 56 Lämmin kausi Keskusta City centre 62 62 % 8.3 25 8.9 49 37 Asuinalue Residential 1919% % 36 15 44 63 88 Cold period Warm period Dissolved metals ~ 40 % At the residential cathcments a larger proportion of the metals in dissolved form and also the concentration of dissolved metals is higher there During cold seasons, a larger proportion of metals is particulate bounded
Annual pollutant loads (unit loads) No systematic pattern kg/km²/yr High Intermediate Low TSS 58000 41000 5300 tot-n 330 240 260 tot-p 68 47 8.1 TOC 2104 682 768 Mn 30 20 6.0 Zn 55 45 11 Al 1885 1451 387 Co 1.4 0.9 0.2 Cr 3.7 3.0 1.0 Ni 2.4 2.0 0.4 Cu 10 5.0 2.0 Pb 2.0 2.0 0.3 Sillanpää 2013: Finnish residential areas (kg/km²/yr) TSS: 13 000 27 000 Tot-N: 510-1010 Tot-P: 26 50 Developing catchment (kg/km²/yr) TSS: 55 000 Tot-N: 2290 Tot-P: 65
Seasonality of the pollutant loading (2-year averages) 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % High High High tot-n TOC Zn Ni 0 % High High Intermediate Low tot-p HighChart Al Title High Cr High Cu High HighIntermediate Low TSS High Mn High Co High Pb High High Intermediate Low autumn summer spring winter autumn summer spring winter autumn summer spring winter autumn summer spring winter
First flush COLD PERIOD KYLMÄ KAUSI Kiintoaines TOC N P Al Cr Mn Co Ni Zn Cu Pb Keskusta City centre 89 89% 23 21 22 22 21 26 26 23 27 22 24 27 Keskusta City centre 62 62 % 17 18 18 19 24 26 24 22 29 20 22 25 Asuinalue Residential 19 19% 15 23 15 16 11 37 11 12 72 13 19 17 WARM PERIOD LÄMMIN KAUSI Kiintoaines TOC N P Al Cr Mn Co Ni Zn Cu Pb Keskusta City centre 89 89% 26 35 34 30 33 35 40 32 35 30 36 30 Keskusta City centre 62 62 % 19 40 34 27 19 16 24 21 21 33 28 27 Asuinalue Residential 19 19% 34 26 33 38 39 48 41 39 38 35 32 46 First flush (alkuhuuhtouma) is not very common in city centre areas, particularly during the cold period At the residential area there is a slight first-flush for some pollutants
Weather dependent runoff generation 1st study year 2nd study year Warm Cold Warm Cold High 0.64 0.45 0.53 0.27 Intermediate 0.35 0.28 0.34 0.36 Low 0.09 0.49 0.05 0.63