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  • 1.
    Galfi, Helen
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Assessment of stormwater and snowmelt quality based on water management priorities and the consequent water quality parameters2020Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

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  • 2.
    Galfi, Helen
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Suspended solids and indicator bacteria in stormwater runoff: Sources of bias in field measurements2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Stormwater quality monitoring and control is a prerequisite for sustainable water resources management in urban areas. Stormwater monitoring programs are based on general water sampling guidance and, in the absence of standard procedures, employ various sampling and analytical methods. The aim of this thesis is to assess stormwater sampling methods and sample analyses with respect to the bias which may be introduced at different stages of the process of monitoring suspended solids and indicator bacteria.The focus was on the bias introduced by automated sampling methods and by analyses of suspended solids. Towards this end, suspended solids and four indicator bacteria (total coliforms, E. coli, int. enterococci and C. perfringens) concentrations were compared in stormwater samples in two urban catchments, which were collected manually or by automatic samplers. The impact of automatic samplers on E. coli concentrations in stormwater samples was further investigated by conducting a study of sampling line cross-contamination. The representativeness of suspended solids results obtained by the standard Total Suspended Solids (TSS) method was studied in urban bulk snow by assessing the ratio of suspended and settleable solids. TSS concentrations were compared to those obtained by other analytical procedures, including the Suspended Sediment Concentration (SSC) method and a newly introduced Multiple Filter Procedure (MFP). The MFP builds on the existing standard methods involving the filtration of whole water samples, but uses three filters with decreasing pore sizes to reduce filter clogging, and is designed to retain a broad range of solids, which is typical for stormwater. Finally, recognizing the affinity of indicator bacteria to suspended solids, both constituents were manually sampled in stormwater in four urban catchments during fall to assess their natural variation and correlation patterns between these contaminants.The comparison of samples collected manually and by automatic samplers yielded large differences in suspended solids concentrations, especially in the lower concentration range (0-100 mg/L), whereas the agreement between the two types of samples was within the analytical uncertainty (±30%) for all the four indicator bacteria. During the laboratory study, E. coli concentration in the first sample (following sudden bacteria concentration changes) were positively biased in automated samples due to the stormwater residue in the sampling line. When high E. coli concentrations were followed by low concentrations, the low concentrations were overestimated 10-20 times depending on the sampling line length (tested up to 5 m). The study findings should be helpful for improving field protocols for suspended solids and indicator bacteria sampling.The standard TSS analytical method underestimated solids in urban snow packs, because of high amounts of settleable particles remaining in situ, rather than leaving with snowmelt. The comparison between analytical procedures, including TSS, SSC and MFP yielded highly varying results for stormwater samples. The methods using whole water-samples, rather than aliquots withdrawn from such samples, as done in the case of TSS, produced more accurate estimates of solids concentrations, with a fairly good precision. The precision of the newly proposed MFP was generally better than ±10% and its results were comparable to those of standard methods using whole water samples, but the new procedure was less labourious. Consequently, the MFP was recommended for use when the total mass of solids in stormwater runoff is needed.The suspended solids and indicator bacteria concentrations in stormwater runoff varied from catchment to catchment and weak correlations were found between solids and bacteria, partly due to low concentrations of bacteria during the fall period. However, it was shown that the natural variation of the studied concentrations was affected by the sampling and the analytical method. Thus, the bias introduced during the stormwater quality monitoring process is relevant when assessing pollutant concentrations and the compliance of stormwater discharges with prescribed threshold values in the receiving waters.

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  • 3.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Haapala, Jenny
    Vatten Östersund.
    Nordqvist, Kerstin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Westerlund, Camilla
    Länsstyrelsen i Norrbotten.
    Blecken, Godecke-Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Indicator bacteria variation in separate sewer systems in Östersund, Sweden: Preliminary results2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Faecal bacteria are a major pollution threat of water bodies designated for multipurpose use including drinking water sources or recreational purposes. Even though stormwater discharges may contribute significantly to microbiological pollution, they have not been fully investigated in the European context. We have studied the presence of indicator bacteria and total suspended solids (TSS) in stormwater discharged from four urban catchments, with areas between 5 and 40 ha, in Östersund, Sweden. The aim was to determine local variation of standard bacteria strains and TSS in Swedish urban catchments with specific land uses. Further, intra event variations were investigated. During dry weather, indicator bacteria concentrations in sewers conveying baseflow did not exceed 100 CFU/100 mL. During storm runoff, total coliform and int. enterococci concentrations increased 102 to 103 times, compared to those in baseflow. Compared to these two parameters, considerably lower concentrations were observed for E. coli and C. perfringens. Bacteria concentrations differed significantly among the sampling sites and partly, a first flush phenomenon was observed. Partly, significant correlations between TSS and indicator bacteria were observed. These were catchment specific and need a more detailed assessment. Further research will focus on seasonal variations and influential factors.

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  • 4.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Haapala, Jenny
    Vatten Östersund, Water Engineering, Water Department Östersund, Östersund Municipality.
    Nordqvist, Kerstin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Westerlund, Camilla
    Blecken, Godecke-Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Inter-Event and Intra-Event Variations of Indicator Bacteria Concentrations in the Storm Sewer System of the City of Östersund, Sweden2016Ingår i: Journal of environmental engineering, ISSN 0733-9372, E-ISSN 1943-7870, Vol. 142, nr 7, artikel-id 6016003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An episode of microbiological contamination of the drinking water supply of the City of Östersund, Sweden (63°10′45″N; 14°38′09″E) prompted a study of fecal pollution in four storm drainage catchments discharging in the vicinity of the water treatment plant intake, with the overall aim of determining the presence and variation of standard fecal indicator bacteria strains and total suspended solids (TSS) in stormwater from urban catchments with specific land uses and sizes varying from 5 to 40 ha. Four bacteria strains used as indicators of fecal pollution in Sweden were studied: total coliforms, enterococci, Escherichia coli (E. coli) and Clostridium perfringens (C. perfringens). In dry weather, indicator bacteria concentrations in storm sewers conveying baseflow did not exceed 100  colony forming units (CFU)/100  mL 100  colony forming units (CFU)/100  mL, but during wet weather, total coliform and enterococci concentrations increased 10 2 102 to 10 3 103 times, compared to those in baseflow, and considerably less in the case of E. coli and C. perfringens. Bacteria concentrations differed significantly among the sampling sites and in the majority of events observed in the four catchments; higher bacteria concentrations were observed during the early phases of runoff. Only in one catchment, positive correlations were observed between TSS and total coliforms, E. coli, and enterococci, suggesting similar sources; in the remaining catchments, no such correlations were observed. The collected indicator bacteria data represent a useful addition to the available data on indicator bacteria in stormwater in cold-climate regions.

  • 5.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Nordqvist, Kerstin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Blecken, Godecke-Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Influence of sampling methods on the measurements of urban stormwater quality constituents: Preliminary results2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    The choice between automatic and manual sampling of urban stormwater quality has been addressed in the past as an issue of economic efficiency, field safety, and practicality. Nevertheless, there is experimental evidence that both types of sampling may yield statistically different stormwater quality data. While the past attention focused on differences in sampled solids, a new issue was addressed in this study, the potential impacts of sampling methods on concentrations of indicator bacteria. Towards this end, four indicator bacteria (coliforms, E. coli, enterococci and C. perfringens) were sampled in storm sewers of two urban catchments in Östersund, Sweden, using both automatic samplers and manual sampling. Such data were further supplemented by measurements of total suspended solids (TSS) and turbidity, recognizing that bacteria are mostly transported in the attachment to solids. Preliminary results indicate that there may be large differences between indicator bacteria in automatic and manual samples, with E. coli measurements yielding the least differences, and turbidity readings were correlated well with all the indicator bacteria and particularly E. coli. These findings will be used in the continuation of this study for refining the existing experimental design and developing practical guidance for surveys of municipal storm sewers for faecal pollution.

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  • 6.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Nordqvist, Kerstin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Sundelin, Monica
    Hjortens Lab, Östersund.
    Blecken, Godecke-Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Comparison of indicator bacteria concentrations obtained by automated and manual sampling of urban stormwater runoff2014Ingår i: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 225, nr 9, artikel-id 2065Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A comparative study of indicator bacteria concentrations obtained by laboratory analysis of grab samples of storm water, which were collected manually or by automatic samplers, was carried out in two urban catchments. Samples were analyzed for four types of indicator bacteria, total coliforms, Escherichia coli (E. coli), enterococci, and Clostridium perfringens and further documented by measurements of total suspended solids (TSS) and turbidity. Analysis of complete data sets (N=198) indicated no statistically significant differences in the geometric means of all the constituent samples collected automatically or manually, but there were some small differences between the results produced by the two sampling methods applied. Total coliform concentrations were positively biased in samples collected by automatic samplers, but for the three remaining indicator bacteria (E. coli, enterococci, and C. perfringens), the opposite was true. Risk of sample cross-contamination in automatic samplers was assessed in the laboratory by sampling consecutively synthetic storm water with high and low concentrations of E. coli and enterococci. The first low-concentration samples preceded by high-concentration samples were cross-contaminated and the measured concentrations were positively biased. This cross-contamination was explained by storm-water residue in the sampling line. Such a residue remained in place even after line purging by compressed air, and its mass depended on the sampling line length (tested up to 5 m), as verified by measurements in the laboratory. The study findings should be helpful for improving field protocols for indicator bacteria sampling.

  • 7.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Österlund, Helene
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Estimation of Faecal Indicator Bacteria in Stormwater by Multiple Regression Modelling and Microbial Partitioning to Solids2018Ingår i: New Trends in Urban Drainage Modelling: UDM 2018 / [ed] Giorgio Mannina, Cham: Springer, 2019, s. 830-835, 2018, s. 830-835Konferensbidrag (Refereegranskat)
    Abstract [en]

    Concerns about the contamination of sources of drinking water by stormwater motivated a sanitary survey of several urban catchments in the City of Östersund (Northern Sweden). A data subset from these surveys, comprising of faecal indicator bacteria (FIB) concentrations (E. coli and enterococci), measured for six storm events in three catchments, was used for investigating the feasibility of developing a FIB estimation procedure for the studied catchments by two approaches: (a) Multiple regression models, and (b) microbial partitioning to solids. In regressions, five explanatory variables (associated constituents) were derived from the literature and measured data: stormwater temperature and flow rate, and measurements of total suspended solids (TSS), total phosphorus (TP) and electric conductivity (EC). The obtained regression models were satisfactory for enterococci (regression of modelled FIBs on measured FIB was described by R2 = 0.7), but less acceptable for E. coli (R2 = 0.2). Microbial partitioning to stormwater solids from gully pots was found infeasible; the sediment sampled contained very low FIB counts. Hence, the former method is recommended for further refinement and applications.

  • 8.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Österlund, Helene
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Indicator bacteria and associated water quality constituents in stormwater and snowmelt from four urban catchments2016Ingår i: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 539, s. 125-140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    SummaryFour indicator bacteria were measured in association with physico-chemical constituents and selected inorganics during rainfall, baseflow and snowmelt periods in storm sewers of four urban catchments in a northern Swedish city. The variation patterns of coliforms, E. coli, enterococci and C. perfringens concentrations were assessed in manually collected grab samples together with those of phosphorus, nitrogen, solids, and readings of pH, turbidity, water conductivity, temperature and flow rates to examine whether these constituents with variation patterns similar to those of indicator bacteria, and to exclude the constituents with less similarity. In the reduced data set, the similarities were quantified by the clustering correlation analysis. Finally, the positive/negative relationships found between indicator bacteria and the identified associated constituent groups were described by multilinear regressions. In the order of decreasing concentrations, coliforms, E. coli and enterococci were found in the highest mean concentrations during both rainfall and snowmelt generated runoff. Compared to dry weather baseflow, concentrations of these three indicators in stormwater were 10 (snowmelt runoff) to 102 (rain runoff) times higher. C. perfringens mean concentrations were practically constant regardless of the season and catchment. The type and number of variables associated with bacteria depended on the degree of catchment development and the inherent complexity of bacteria sources. The list of variables associated with bacteria included the flow rate, solids with associated inorganics (Fe and Al) and phosphorus, indicating similar sources of constituents regardless of the season. On the other hand, bacteria were associated with water temperature only during rain periods, and somewhat important associations of bacteria with nitrogen and pH were found during the periods of snowmelt. Most of the associated constituents were positively correlated with bacteria responses, but conductivity, with two associated inorganics (Si and Sr), was mostly negatively correlated in all the catchments. Although the study findings do not indicate any distinct surrogates to indicator bacteria, the inclusion of the above identified constituents (flow rate, solids and total phosphorus for all seasons, water temperature for rainfall runoff, and total nitrogen and pH for snowmelt only) in sanitary surveys of northern climate urban catchments would provide additional insight into indicator bacteria sources and their modelling.

  • 9.
    Galfi, Helen
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Österlund, Helene
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Mineral and Anthropogenic Indicator Inorganics in Urban Stormwater and Snowmelt Runoff: Sources and Mobility Patterns2017Ingår i: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 228, nr 7, artikel-id 263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inorganic chemicals in urban stormwater and snowmelt runoff originate from catchment geology and anthropogenic activities. The occurrence, partitioning and mobility of six minerals and six trace metal (TM) indicators of anthropogenic activities were studied in stormwater, snowmelt and baseflow in four urban catchments, and the sampling of inorganics was supplemented by measurements of electrical conductivity (EC), pH and total suspended solids (TSSs). Minerals occurred at concentrations several orders of magnitude higher (1–102 mg/L) than those of TMs (10−2–102 μg/L) and reflected the composition of local groundwater seeping into sewers. Concentrations of Ca, K, Mg and Na were enhanced by baseflow contributions and followed closely the electrical conductivity. Al and Fe minerals occurred in insoluble forms, and their pollutographs were similar to those of TMs, whose concentrations mimicked, to some extent, the flux of TSS. The TMs with the highest and lowest particulate fractions were Cr&Pb and Cu&Zn, respectively. The concentrations of total TMs in snowmelt were two to four times higher than those in stormwater, and both sources likely exceeded some of the stormwater effluent limits (for Cd, Cu and Zn) proposed in Sweden. Where such concentrations depended on water hardness, the risk of toxicity might be reduced by elevated hardness of the monitored snowmelt and stormwater. Recognizing the good ecological status of the study area receiving water, Lake Storsjön, some protection against polluted runoff and snowmelt may be needed and could be achieved by implementing stormwater management measures controlling TSS and TMs.

  • 10.
    Nordqvist, Kerstin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Galfi, Helen
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Österlund, Helene
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Westerlund, Camilla
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Measuring solid concentrations in urban stormwater and snowmelt: a new operational procedure2014Ingår i: Environmental Science: Processes & Impacts, ISSN 2050-7887, E-ISSN 2050-7895, Vol. 16, nr 9, s. 2172-2183Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A comparative study of five methods measuring suspended sediment or solid concentrations in water–sediment mixtures indicated that, depending on the method used, broadly varying results can be obtained. For water–sediment mixtures containing sand size particles, the standard TSS method produced negatively biased results, accounting for 0 to 90% of the present solids; the negative bias directly depended on the magnitude of the sand fraction in the water–sediment mixture. The main reason for the differences between the TSS and the rest of the methods laid in the handling of samples; in the former methods, whole samples were analysed, whereas the TSS analysis was performed on sub-samples withdrawn from the water sample, the withdrawal process tending to exclude large particles. The methods using whole water–solid samples, rather than aliquots withdrawn from such samples, produced accurate estimates of solid concentrations, with a fairly good precision. Two whole-sample methods were studied in detail, a slightly modified standard SSC-B method and the newly proposed operational procedure referred to as the Multiple Filter Procedure (MFP), using three filters arranged in a series with decreasing pore sizes (25, 1.6 and 0.45 µm). Both methods assessed accurately concentrations of solids in a broad range of concentrations (200–8000 mg L−1) and particle sizes (0.063–4.0 mm). The newly introduced MFP was in good agreement with the SSC procedure, the differences between the two procedures not exceeding the standard bias defined for the SSC-B method. The precision of both SSC and MFP was generally better than ±10%. Consequently, these methods should be used when the total mass of transported solids is of interest.

  • 11.
    Westerlund, Camilla
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Nordqvist, Kerstin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Galfi, Helen
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Marsalek, Jiri
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Particle pathways during urban snowmelt and mass balance of selected pollutants2011Konferensbidrag (Refereegranskat)
    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.

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