| 1. |
- Galfi, Helen
(author)
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Assessment of stormwater and snowmelt quality based on water management priorities and the consequent water quality parameters
- 2020
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Doctoral thesis (other academic/artistic)abstract
- 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.
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| 2. |
- Galfi, Helen, et al.
(author)
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Comparison of indicator bacteria concentrations obtained by automated and manual sampling of urban stormwater runoff
- 2014
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In: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 225:9
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Galfi, Helen, et al.
(author)
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Estimation of Faecal Indicator Bacteria in Stormwater by Multiple Regression Modelling and Microbial Partitioning to Solids
- 2019
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In: New Trends in Urban Drainage Modelling. - Cham : Springer International Publishing. ; , s. 830-835
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Conference paper (peer-reviewed)abstract
- 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.
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| 4. |
- Galfi, Helen, et al.
(author)
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Indicator bacteria and associated water quality constituents in stormwater and snowmelt from four urban catchments
- 2016
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 539, s. 125-140
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Journal article (peer-reviewed)abstract
- 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.
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| 5. |
- Galfi, Helen, et al.
(author)
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Indicator bacteria variation in separate sewersystems in Östersund, Sweden - Preliminary results : [La variation des indicateurs bactériens et des flux de MES dans les systèmes séparatifs d'eaux pluviales à Östersund, en Suède - Résultats préliminaires]
- 2013
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Conference paper (peer-reviewed)abstract
- 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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| 6. |
- Galfi, Helen, et al.
(author)
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Influence of sampling methods on the measurements of urban stormwater quality constituents - Preliminary results : [Influence des méthodes d'échantillonnage pour la mesure de la qualité des eaux pluviales urbaines - Résultats préliminaires]
- 2013
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Conference paper (peer-reviewed)abstract
- 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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| 7. |
- Galfi, Helen, et al.
(author)
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Inter-Event and Intra-Event Variations of Indicator Bacteria Concentrations in the Storm Sewer System of the City of Östersund, Sweden
- 2016
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In: Journal of environmental engineering. - 0733-9372 .- 1943-7870. ; 142:7
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Journal article (peer-reviewed)abstract
- 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.
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| 8. |
- Galfi, Helen, et al.
(author)
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Mineral and Anthropogenic Indicator Inorganics in Urban Stormwater and Snowmelt Runoff : Sources and Mobility Patterns
- 2017
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In: Water, Air and Soil Pollution. - : Springer. - 0049-6979 .- 1573-2932. ; 228:7
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Galfi, Helen
(author)
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Suspended solids and indicator bacteria in stormwater runoff : Sources of bias in field measurements
- 2014
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Licentiate thesis (other academic/artistic)abstract
- 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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| 10. |
- Järlskog, Ida, 1991, et al.
(author)
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Occurrence of tire and bitumen wear microplastics on urban streets and in sweepsand and washwater
- 2020
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 729
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Journal article (peer-reviewed)abstract
- Tire and road wear particles have been identified as a potential major source of microplastics in the environment. However, more knowledge of the emissions and their further fate in the environment is needed, and the effectiveness and benefits of potential measures must be investigated to support future risk management efforts. Here the concentrations of tire and bitumen microplastic particles (TBMP) on roads and in nearby in stormwater, sweepsand and washwater were measured for the first time within the same area and time period. The analysis also included plastic, paint and fiber particles. Road dust was sampled on the road surface using a wet dust sampler, before and after street sweeping on two occasions. On each of these occasions, and several occasions during a four-month period with frequent street sweeping, sweepsand and washwater, as well as flow-weighted sampling of stormwater, were collected. TBMP concentrations were operationally defined, using density separation for some samples, followed by analysis by stereo microscopy. Sodium iodide (NaI) was found to be effective for density separation of TBMP. The largest proportion of anthropogenic microplastics detected consisted of tire tread wear and bitumen. The number of TBMP ≥100 μm in the WDS samples was up to 2561 particles/L. Sweepsand and washwater contained high amounts of TBMP ≥100 μm, up to 2170 particles/kg dw and 4500 particles/L, respectively. The results show that the sweeper collects considerable amounts of TBMP, and thus weekly sweeping might prevent further transport of TBMP to the receiving stormwater. In stormwater the number of particles ≥100 μm was up to 3 particles/L and ≥ 20 μm was up to 5900 particles/L showing the importance of analysing smaller microparticle sizes than 100 μm in all samples in future studies. This study also confirms that there is a substantial volume of TBMP generated from traffic that enters the environment.
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| 11. |
- Järlskog, Ida, 1991, et al.
(author)
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Traffic-related microplastic particles, metals, and organic pollutants in an urban area under reconstruction
- 2021
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 774
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Journal article (peer-reviewed)abstract
- In urban environments, particularly areas under reconstruction, metals, organic pollutants (OP), and microplastics (MP), are released in large amounts due to heavy traffic. Road runoff, a major transport route for urban pollutants, contributes significantly to a deteriorated water quality in receiving waters. This study was conducted in Gothenburg, Sweden, and is unique because it simultaneously investigates the occurrence of OP, metals, and MP on roads and in stormwater from an urban area under reconstruction. Correlations between the various pollutants were also explored. The study was carried out by collecting washwater and sweepsand generated from street sweeping, road surface sampling, and flow-proportional stormwater sampling on several occasions. The liquid and solid samples were analyzed for metals, polycyclic aromatic hydrocarbons (PAH), oxy-PAH, aliphatics, aromatics, phthalates, and MP. The occurrence of OP was also analyzed with a non-target screening method of selected samples. Microplastics, i.e. plastic fragments/fibers, paint fragments, tire wear particles (TWP) and bitumen, were analyzed with a method based on density separation with sodium iodide and identification with a stereo microscope, melt-tests, and tactile identification. MP concentrations amounted to 1500 particles/L in stormwater, 51,000 particles/L in washwater, and 2.6 × 106 particles/kg dw in sweepsand. In stormwater, washwater and sweepsand, MP ≥20 μm were found to be dominated by TWP (38%, 83% and 78%, respectively). The results confirm traffic as an important source to MP, OP, and metal emissions. Concentrations exceeding water and sediment quality guidelines for metals (e.g. Cu and Zn), PAH, phthalates, and aliphatic hydrocarbons in the C16–C35 fraction were found in most samples. The results show that the street sweeper collects large amounts of polluted materials and thereby prevents further spread of the pollutants to the receiving stormwater.
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| 12. |
- Nordqvist, Kerstin, et al.
(author)
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Measuring solid concentrations in urban stormwater and snowmelt : a new operational procedure
- 2014
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In: Environmental Science. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 16:9, s. 2172-2183
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Journal article (peer-reviewed)abstract
- 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.
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| 13. |
- Polukarova, Maria, 1992-, et al.
(author)
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Organic pollutants, nano- and microparticles in street sweeping road dust and washwater
- 2020
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In: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 135
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Journal article (peer-reviewed)abstract
- Road areas are pollution hotspots where many metals, organic pollutants (OPs) and nano/microparticles accumulate before being transported to receiving waters. Particles on roads originate from e.g. road, tyre and vehicle wear, winter road maintenance, soil erosion, and deposition. Street sweeping has the potential to be an effective and affordable practice to reduce the occurrence of road dust, and thereby the subsequent spreading of pollutants, but there is currently little knowledge regarding its effectiveness. In this paper we investigate the potential of street sweeping to reduce the amounts of OPs and nano/microparticles reaching stormwater, in a case study sampling road dust and washwater from a street sweeping machine, road dust before and after sweeping, and stormwater. The compound groups generally found in the highest concentrations in all matrices were aliphatics C5–C35 > phthalates > aromatics C8–C35 > PAH-16. The concentrations of aliphatics C16–C35 and PAHs in washwater were extremely high at ≤ 53,000 µg/L and ≤ 120 µg/L, respectively, and the highest concentrations were found after a 3-month winter break in sweeping. In general, fewer aliphatic and aromatic petroleum hydrocarbons and PAHs were detected in road dust samples than in washwater. The relative composition of the specific PAH-16 suggests tyre wear, vehicle exhausts, brake linings, motor oils and road surface wear as possible sources. The study indicates that many of the hydrophobic compounds quantified in washwater are attached to small particles or truly dissolved. The washwater contains a wide range of small particles, including nanoparticles in sizes from just below 1 nm up to 300 nm, with nanoparticles in the size range 25–300 nm present in the highest concentrations. The results also indicated agglomeration of nanoparticles in the washwater. The street sweeping collected a large amount of fine particles and associated pollutants, leading to the conclusion that washwater from street sweeping needs to be treated before disposal.
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| 14. |
- Westerlund, Camilla, et al.
(author)
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Particle pathways during urban snowmelt and mass balance of selected pollutants
- 2011
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Conference paper (peer-reviewed)abstract
- 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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