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Particle pathways during urban snowmelt and mass balance of selected pollutants
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.ORCID iD: 0000-0003-1725-6478
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
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2011 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

The pathways and mass balance of selected pollutants, released during the snowmelt process, were investigated for urban bulk snow placed in small, intermediate, and large-scale lysimeters. The results showed that low percentages of TSS (total suspended solids) and heavy metal (Cu, Zn, Pb) loads contained in snow were transported with snowmelt, the rest remained in situ with the particulate residue. The TSS loads transported with snowmelt were 3, 3.4, and 4.8% of the initial TSS mass in the small, intermediate and large lysimeters, respectively. Particulate heavy metal loads transported with snowmelt, during the whole melting process, were measured in the intermediate lysimeter for copper and zinc, and for lead in the large lysimeter. The measured mass loads in snowmelt leaving the intermediate lysimeter were 7.5 and 7.2% for copper and zinc, respectively, and 1.7% for lead leaving the large lysimeter. The remainder of the loads stayed in situ with the particulate residue. The loads transported with snowmelt were independent of the initial TSS and metal concentrations in bulk snow. These findings have implications for siting and operating snow disposal facilities; most of the initial TSS and particulate heavy metal loads can be retained on site, rather than released with snowmelt into the receiving environments.

Place, publisher, year, edition, pages
2011.
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-32682Local ID: 73eff0f4-d23d-449e-af7e-39fe5d330683OAI: oai:DiVA.org:ltu-32682DiVA, id: diva2:1005916
Conference
International Conference on Urban Drainage : 11/09/2011 - 15/09/2011
Note
Godkänd; 2011; 20120510 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2020-03-01Bibliographically approved
In thesis
1. Assessment of stormwater and snowmelt quality based on water management priorities and the consequent water quality parameters
Open this publication in new window or tab >>Assessment of stormwater and snowmelt quality based on water management priorities and the consequent water quality parameters
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Stormwater and snowmelt pollution contributes to degradation of quality of the receiving waters. For assessing such impacts, it is effective to focus on specific causes of degradation, as done in this study of the quality of stormwater and snowmelt discharges into the receiving waters serving for supply of raw drinking water and water-based recreation. While the main priority were faecal indicator bacteria (FIBs), the understanding of their occurrence, and of other potential effects on the receiving waters, required addressing additional water quality parameters as well.     

Exports of FIBs in stormwater and snowmelt discharged from four urban catchments yielded the following findings: (a) E.coli, with mean concentration of all stormwater data Cmean = 430 cfu (colony forming units)/100 mL, and enterococci (Cmean=1380 cfu/100 mL) were the best indicators of faecal pollution of stormwater, but total coliform (Cmean=3130 cfu/100 mL) and C. perfringens (Cmean=150 cfu/100 mL) were much less effective: the former indicator includes non-faecal bacteria and the latter one barely varied; (b) Among the different catchments, the central catchment with mixed land use produced the highest concentrations of FIBs; (c) FIB concentrations in snowmelt were significant only in the case of enterococci (400 cfu/100 mL); and, (d) Baseflows in two catchments were practically devoid of FIBs, with Cmean=10 cfu/100 mL for both E.coli and enterococci. Hence, there were no contributions of sanitary sewage to the storm sewer baseflows.

FIB concentrations varied with stormwater or snowmelt quality, described by associated parameters, which were identified by cluster analysis as: temperature, conductivity, TSS, flow rate, and TP. Such findings were used in statistical regressions indicating that E. coli and enterococci could be statistically modelled in three of the four catchments, with determination coefficients R2 ranging from 38-66%. In spite of uncertainties, such modelling would be useful for future FIB monitoring, or for comparing remediation alternatives. Estimation of FIBs by microbial partitioning to settleable solids (represented by gully pot sediments) was infeasible, because these highly mineral sediments contained little FIBs.

Storm sewer outfall effluents were also analyzed for mineral (Al, Ca, Fe, K, Mg, Na) and anthropogenic indicator trace metal (TM) inorganics (Cd, Cr, Cu, Ni, Pb, Zn). The total mass of inorganics exported from the catchments by runoff or snowmelt was dominated by mineral inorganics, which were particularly high in baseflows. TM concentrations were compared to the tentative guidance limits suggested in Sweden as annual mean, or maximum event mean, total TM concentrations. Effluents from the catchments studied clearly exceeded the recommended values 5 times in the case of Zn.

Field studies drew attention to uncertainties in measured FIBs and solids. Automated sampling of greatly varying FIB concentrations was affected by sampling line water residuals, which can be minimized by short sampling lines and avoidance of sags in the sampling line. Stormwater and snowmelt solids were underestimated by the conventional TSS method requiring withdrawal of aliquots from total samples. This bias can be eliminated by using whole-sample methods; either the existing SSC (suspended sediment concentration) method, or the newly proposed (and easier to use) multiple filter procedure (MFP), filtering whole samples through progressively finer filters (pore sizes 25, 1.6 and 0.45 µm). The MFP produced data equivalent to those obtained with SSC, as confirmed by the Limits of Agreement (LoA) statistical procedure.

Abstract [sv]

Dagvatten från regn och snösmältning är viktiga komponenter i föroreningstransport till ytvattentäkter som används för dricksvattenproduktion och badvatten. I denna studie har potentiella källor och transportvägar av mikrobiologiska föroreningar studerats i Östersund genom mätningar och utvärdering av fekala indikatorbakterier (FIB) i dagvatten som släpps ut i den närliggande Storsjön. Även andra föroreningar, så som metaller, ingick i studien för att bättre förstå källorna till och förhållanden mellan dessa parametrar och FIB.

Transport av FIB i dagvatten som släppts ut från fyra urbana avrinningsområden gav följande resultat: (a) E. koli, med medelkoncentration av all data sammanlagt (Cmean = 430 cfu (kolonibildande enheter)/100 ml), och enterokocker (Cmean = 1380 cfu/100 ml), var de bästa fekala indikatorerna; (b) koliformer (Cmean = 3130 cfu/100 ml) och C. perfringens (Cmean = 150 cfu/100 ml) var mycket mindre effektiv som indikator; där koliformer inkluderar icke-fekala bakterier och C. perfringens uppvisade knappt någon variation mellan platser och provtagningstillfällen; (c) mellan de olika avrinningsområdena uppmättes de högsta halterna av FIB i ett centralt avrinningsområde med blandad markanvändning; (d) FIB-halter i snösmältning var endast signifikanta för enterokocker (400 = cfu/100 ml) och (e) i basflöden, vilket förekom i två av avrinningsområdena, uppmättes nästan inga FIB. Följaktligen har dagvattnet i dessa områden inte påverkats av felkopplingar eller inläckage av spillvatten.

FIB-halter varierade i dagvatten från regn och snösmältning beroende av andra parametrar. Hur dessa parametrar relaterade till FIB identifierades genom klusteranalys. Parametrarna var: temperatur, konduktivitet, suspenderade ämnen (TSS), flödeshastighet och fosfor. Dessa har vidare använts i regressionsanalys. E. koli och enterokocker kunde statistiskt modelleras i tre avrinningsområden med determinationskoefficienter, R2, mellan 38-66%. Trots osäkerheter skulle sådan modellering vara användbar för framtida FIB-övervakning eller för att jämföra olika alternativ av åtgärder. Uppskattning av FIB genom provtagning av dagvattensediment i rännstensbrunnar lyckades inte, eftersom dessa mycket mineralhaltiga partiklar innehöll låga FIB-halter.

Dagvatten analyserades även för oorganiska ämnen såsom mineraler (Al, Ca, Fe, K, Mg, Na) och antropogena tungmetaller (Cd, Cr, Cu, Ni, Pb, Zn). Transport av oorganiska ämnen från avrinningsområden via dagvattenledningar dominerades av mineraler som uppvisade höga halter i basflöden. Tungmetallhalter jämfördes med riktvärden som föreslagits i Sverige. Dagvatten i respektive avrinningsområde överskred de rekommenderade värdena fem gånger för Zn.

Vid genomförda fältstudier påvisades osäkerheter i uppmätta FIB-halter och suspenderade ämnen. Automatiserad provtagning med kraftigt varierande FIB-halter påverkades av rester av vattnet i provtagningsslangarna, vilket kan minimeras genom kortare provtagningsslang utan böjar i provtagningslinjen. Vidare påvisades att mängden suspenderade ämnen i dagvatten underskattades med den konventionella TSS-metoden som innebär analys på delprov istället av helprov. Felkällor i uppskattning kan elimineras med hjälp av helprovsanalys; antingen den befintliga SSC-metoden (suspenderad sedimentkoncentration) eller i denna studie föreslagen MFP (multipel filter procedure) som innebär filtrering av hela provet genom succesivt finare filter (porstorlekar 25, 1,6 och 0,45 µm). MFP genererade resultat som var ekvivalenta med de som erhölls med SSC, vilket bekräftas genom statistiska metoder.

Place, publisher, year, edition, pages
Luleå University of Technology, 2020. p. 85
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Stormwater quality, indicator bacteria, water quality assessment
National Category
Water Engineering
Research subject
Urban Water Engineering
Identifiers
urn:nbn:se:ltu:diva-77915 (URN)978-91-7790-546-2 (ISBN)978-91-7790-547-9 (ISBN)
Public defence
2020-05-05, D770, 10:00 (English)
Opponent
Supervisors
Available from: 2020-03-02 Created: 2020-03-01 Last updated: 2020-03-31Bibliographically approved

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