| 1. |
- Broekhuizen, Ico
(författare)
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Hydrological modelling of green urban drainage systems : Advancing the understanding and management of uncertainties in data, model structure and objective functions
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of green urban drainage systems such as green roofs, swales and pervious areas has in recent years become a popular option to reduce flood risk and water quality problems in a more sustainable way than with traditional pipe-based drainage systems. Computer models are valuable tools for the management of such systems. While uncertainties associated with these models have been investigated for pipe-based systems, their adaptation and application to green areas requires re-examination of these uncertainties, as additional hydrological processes become relevant and new opportunities for model calibration arise. The overall aim of this thesis is to contribute to understanding and reducing of uncertainties in the mathematical modelling of green urban drainage studies. Specific topics adressed are field measurements, data processing, data selection, model structures and objective functions.Weighing-bucket precipitation sensors were confirmed on multiple occasions to be accurate to within ±1% of accumulated precipitation. A new signal processing method was able to convert accumulated precipitation to noise-free 1-minute rainfall rates that reproduced total rainfall volumes with only minor errors.Area-velocity flow sensors were tested and their measurement uncertainties quantified in laboratory experiments for flow rates up to 9 L s-1. Total flow rate uncertainty was ±0.34 L s-1 in optimal conditions (flat pipe), increasing to 0.60 and 0.83 L s-1 for pipe slopes of 2% and 4% respectively. In the presence of an upstream obstacle the uncertainty was 2 to 3 times larger, although in the case of no pipe slope this could be reduced to the same as the optimal conditions by increasing water levels in the pipe.Three different urban drainage models for green areas were compared using long-term simulations of synthetic catchments with different soil types and depth. In all models surface runoff formed a significant component of the annual water balance for some soil profiles, while the models reacted differently to changes in soil type an depth. Inter-model variation was large compared to the variation between different soil profiles.Four different models were tested for the simulation of runoff from two full-scale green roofs. More complex models showed better performance in reproducing observed runoff, while the magnitude and source of model predictive uncertainties varied between the models. It was also found that for all models calibration periods with high inter-event variability in terms of runoff retention provided more information in the calibration process.The use of soil water content observations (SWC) was investigated for the calibration of a detailed model of an urban swale. SWC observations were found to be useful for improving the identifiability of certain model parameters and the model predictions of SWC, and for setting the initial SWC in simulations. Different approaches to combining SWC and outflow observations were compared, revealing that the precision and reliability of model predictions could in some cases be improved by using a different way of determining which parameter sets to use for the generation of uncertain model predictions.The influence of calibration data selection was investigated using a model of a small green urban catchment. Performance of the model when calibrated using different sets of events varied significantly. Two-stage calibration strategies (where first small rainfall events were used to calibrate impervious area parameters, followed by using larger events to calibrate green area parameters) showed good performance especially in terms of runoff volume and peak flow. Finally it was found that the benefits of the two-stage calibration were greater when using a model with a low spatial resolution than with a high spatial resolution.For the same catchment tests were also carried out of an objective function that explicitly allows for timing errors, rather than comparing only simulated and observed values for the same time step. Model predictions generated using this objective function were equally reliable, but more precise and therefore of more practical value.Finally, drawing upon the practical experience from working with different models and drainage systems an overview is provided of the applicability of the modelling techniques used in this thesis for different models and what features may be desirable to add to models to improve this.
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| 2. |
- Galfi, Helen
(författare)
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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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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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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| 3. |
- Gavric, Snezana
(författare)
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Trace metals in swale soils and sediments from gully pots and stormwater management ponds
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three commonly used drainage system components, with considerably different characteristics and roles in stormwater management, were studied and reported on in this thesis: (i) grass swales, (ii) gully pots (GPs), and (iii) stormwater management ponds. With time, solids and associated pollutants accumulate in these components, and regular maintenance is needed to ensure that their design functions, including protection of the environment, are sustained.Trace metals and their concentrations, loads and speciation were investigated within and among the individual types of components. The study program started with a critical review of processes enhancing the quality of stormwater passing over grass filter strips and through swales, and continued with field research of swale soils, and sediments from GPs and ponds.The swales studied in the thesis served for stormwater drainage and storage of snow cleared from adjacent trafficked areas during winter months. Results suggest that both stormwater runoff and snow stored in the swale were transport vectors of metals originating from traffic. Other sources of metals were native soils and traction material used in winter road maintenance.Moreover, the speciation results showed that across components, Zn and Pb were the metals with the highest share in the most mobile fraction, followed by Cu, while Ba, Cr,V, Co, and Ni were found in a higher share in the less mobile fractions.GP and pond sediments showed similar organic matter content, whereas swales soils showed relatively low organic content, further decreasing with the soil depth. Results suggested that higher organic matter content corresponded to higher concentrations of certain metals in the case of ponds and, to some extent, swales. In the case of GPs, a positive relationship between metals and the proportion of fine particles was detected.The highest concentrations of Cu and Zn were observed in sediments from ponds and reached 319 and 1380 mg/kg DW, respectively. The highest concentration of Pb (188mg/kg DW) was observed in swale, operating for 57 years located next to a road with the traffic intensity of 11,650 v/day.The large variation in the accumulated dry mass of solids in GPs (2-91 kg) questions the current practice of emptying all GPs at the same regular intervals. Moreover, of the 26 GP samples, Swedish thresholds for soils with the sensitive (S) land use were exceeded for Cu in five samples and Zn in six samples. Of 32 pond samples, the S threshold was exceeded for Cu in nine samples and Zn in 12 samples; of these, three and eight of the pond samples also exceeded the less sensitive (LS) threshold. Of 96 swale samples, 25 samples exceeded the S threshold for Pb, with one sample also exceeding the LS threshold.
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| 4. |
- Müller, Alexandra
(författare)
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An evaluation of sources contributing to urban runoff pollution
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Urban runoff is a significant pathway for the transport of diverse substances from the urban environment to receiving water bodies. Many of these substances are pollutants of environmental concern with potentially harmful effects on aquatic life. Detailed knowledge of the sources of pollutants entering stormwater runoff is needed to mitigate these effects.The overall aim of this doctoral thesis is therefore to provide new knowledge on the sources contributing to urban runoff pollution and to evaluate the specific contributions of micropollutants from two known major sources: building and structure surface materials, and vehicular activities. The work presented herein also (i) identifies pollutants that are expected to occur in runoff from buildings and other structure surfaces in the urban environment as well as in runoff from the road environment, (ii) estimates the concentrations of these pollutants released into runoff, and (iii) evaluates methods for identifying sources contributing to the pollution of urban stormwater runoff.The novel work presented in the thesis includes a critical review of the literature on sources contributing to urban runoff pollution, laboratory leaching tests and open-air sampling of pilot panels of building and structure surface materials, and field sampling of urban roadside snow. The literature review was not restricted in terms of type of pollution, while the experiments focused on selected metals and organic micropollutants including phthalates, alkylphenols, bisphenol A, and polycyclic aromatic hydrocarbons (PAHs).According to the literature review, atmospheric deposition, vehicular activities, and metallic building envelopes are the major pollution sources in the urban environment and have been studied far more extensively than other sources. Moreover, their dominance is likely to continue given their central roles in urban environments. The experimental results confirmed that vehicular activities were sources of octylphenols, bisphenol A, and phthalates as well as the metal(loid)s Sb and W, both of which were rarely determined in previous studies on urban runoff. Building and structure surface materials such as copper sheets, zinc sheets, and polyvinyl chloride (PVC) roofing membranes were found to release Cu, Zn, nonylphenols, and phthalates. Among alkylphenols, nonylphenols were predominantly found in building surface runoff while octylphenols occurred predominantly in roadside snow. Metals occurred more commonly in dissolved (<0.45 μm) form in building surface runoff than in roadside snow, where metals were mainly attached to particles.A comparison of methods for identifying building surface materials contributing to runoff pollution showed that laboratory leaching tests were generally effective for source identification but not for estimating concentrations in actual runoff, whereas open-air pilot studies were resource-intensive but give results that agree well with analyses of real runoff. In addition, the release of pollutants from building surface materials subjected to in-situ ageing was investigated and the water quality of rainwater-induced runoff was compared to that of snowmelt-induced runoff; neither of these issues were adequately addressed in the previous literature. These studies showed that pollutant concentrations were generally higher in rain runoff than in snowmelt runoff and that pollutant releases from most materials and substances exhibited no decreasing or increasing trend over time. However, the release of nonylphenols from one of the PVCs did decrease over time, possibly because of washing out and material ageing.
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| 5. |
- Okwori, Emmanuel, 1988-
(författare)
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Analytics-driven approaches supporting asset management of sanitary sewer networks
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sewer blockages can cause overflows and flooding, with consequences such as damage to property and environmental pollution, risks to public health and economic loss. Despite the causes being understood, blockages in sewer networks may occur unpredictably. The responsible staff for sewer networks at water utilities need to efficiently determine the most effective action (what), the specific network location needing attention (where), the optimal timing for intervention (when), and the appropriate remedial task (how), especially given the unpredictability of blockages. Today a reactive approach to asset management and maintenance is often adopted. Additionally, data availability, quality and interoperability between systems are not always at levels that can support decided objectives, proactive maintenance planning and asset management of pipe networks. Thus, the aim of this thesis is to propose and evaluate approaches that can support analytics-driven maintenance planning and asset management for sewer networks. These approaches aim to contribute to mitigating the impact of siloed data structures and enhance the understanding of blockage root causes from a spatial perspective.In this thesis, the challenges of data management in the asset management of pipe networks were investigated through focus group workshops and questionnaire surveys. A conceptual framework was developed based on findings from focus group workshops and surveys. The framework combines data quality assessments, interoperability evaluations between asset management tools, data collection, and informational benefits analysis. This framework aimed to identify the presence of data silos and plausible pathways towards more data-driven data management strategies. A performance assessment combining performance indicators associated with blockages and partial least squares regression (PLS) was conducted to draw inferences that could be useful at a strategic level. Furthermore, a spatial heterogeneity assessment of blockages and factors affecting blockages was carried out. This approach combined network kernel density estimation (NKDE), network k-function, and geographically weighted Poisson regression (GWPR). Lastly, a vulnerability assessment was carried out that combined topological analysis using edge-based centrality measures and network cross-k-function. These approaches were applied to three sewer networks.The focus group workshops and questionnaire surveys identified several challenges affecting data management in the context of pipe network asset management. Many of the challenges could be ascribed to issues related to data quality and interoperability. Results from the preliminary application of the conceptual framework showed how it could be applied for identifying data silos and pathways to data-driven decision-making towards proactive management blockages in sewers. The observed spatial trends and patterns from network k-function analysis and network kernel density estimation showed spatial variability in the occurrence of blockages (single occurring and recurring). Geographically-weighted Poisson regression analysis showed spatial heterogeneity in factors influencing blockage propensity. The network cross-k-function analysis demonstrated that pipes with historical blockage incidents tend to be clustered around critical pipes with higher centrality values. These results could support vulnerability assessments in sewer networks and the development of targeted maintenance strategies. These approaches together could aid data-informed maintenance planning and asset management at the strategic, tactical and operational levels.
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| 6. |
- Rujner, Hendrik, 1983-
(författare)
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Hydrologic processes of vegetated swales in controlling urban stormwater
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vegetated swales are an integral component of Green Stormwater Infrastructure (GSI), designed to manage urban stormwater at its source by reducing volumes and peaks, retaining water within the urban landscape, and providing high-capacity runoff pathways. They facilitate the integration of vegetation-based stormwater solutions with traditional grey infrastructure, creating synergies and enhancing urban drainage. In light of contemporary urban drainage challenges, swales are now assigned multiple functions beyond stormwater conveyance, necessitating enhanced predictability and reduced uncertainties in their hydrologic performance.This thesis investigates the hydrologic functions of vegetated swales in controlling urban stormwater. Vegetated swales are shallow, vegetated channels that manage runoff through infiltration, conveyance, storage, dissipation, and filtration, leading to reduced runoff volumes and attenuated peak flows. The study aims to advance the understanding of swale functions by examining their hydrologic and hydraulic performance under varying conditions. Key objectives include exploring the relationship between hydraulic and hydrological factors and swale hydrographs, such as soil moisture dynamics and swale characteristics, representing swale processes and spatial variability, and evaluating long-term hydrological behavior concerning soil water content (SWC).The methodology involved field experiments and long-term monitoring at two swales in Luleå and a combined stormwater control measure (SCM) in Skellefteå, Northern Sweden. These swales, with differing topographies and vegetative covers, were subjected to controlled irrigation experiments to mimic runoff inflows. The combined SCM, consisting of a rocky slope, vegetated slope, and vegetated collector swale arranged in series, was monitored to assess hydrologic parameters and responses based on natural rainfall inflows. Data collection included rainfall events, inflow and outflow hydrographs, soil infiltration, and SWC using Time Domain Reflectometry (TDR).The study highlights the influence of initial soil moisture conditions only on vegetated swale function. Low SWC leads to high runoff attenuation (up to 74%), whereas high SWC results in predominant conveyance function (attenuation as low as 17%). Runoff peaks were proportionally reduced, with outflow hydrograph lag times ranging from 5 to 15 minutes. Variability in soil properties, hydraulic conductivity, and topography significantly affected swale performance, with bottom slope irregularities impacting runoff dissipation. Double-ring infiltrometer measurements showed infiltration rates varying from 1.78 to 9.41 cm/hr across the swales.For the example of a vegetated swale in combination with additional drainage features upstream, runoff volume reductions frequently exceeded those in studies on grassed swales or filter strips, attributed to large pervious areas and abundant depression storage. Hydrological reductions varied with site-specific conditions, such as soil properties and shallow groundwater interactions, resulting in a median runoff coefficient of 0.03 over 60 storm events. Groundwater interactions and soil moisture fluctuations influenced unsaturated zone dynamics, causing water exfiltration even during dry periods, leading to variable runoff travel times and delayed peak lag times.Eight years of monitoring revealed high spatial variability in SWC, attributed to soil mixing during development. Vegetated slopes showed greater SWC variability than the downstream swale, influenced by lateral stormwater inflows. Seasonal trends indicated increasing site moisture, driven by vegetation maturation, which improved stormwater retention and site resilience.Overall, this dissertation enhances the understanding of influential processes and environmental conditions impacting the function and effectiveness of vegetated swales, providing valuable information to reduce uncertainties in designing and predicting swale hydrological responses.
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| 7. |
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| 8. |
- Vijayan, Arya
(författare)
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Traffic-related pollutants in urban snow : Concentrations, size fractionation, and release with snowmelt
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In urban areas with seasonal snow, traffic-related pollutants such as solid particles, metals, chloride, organic pollutants, and microplastics (MPs) can be temporarily stored in snowbanks along roads and streets. When the snow melts, it releases the accumulated pollutants and the resulting snowmelt with diverse pollutants may partly infiltrate into the ground, or enter storm sewers and eventually be discharged into, and impact on, the receiving waters. To address the resulting environmental concerns, it is important to gain a more comprehensive understanding of (i) occurrence, distribution, and temporal variation of conventional (TSS, Cu, Zn, Pb, Cd, chloride and PAHs) as well as emerging pollutants (Tire and Road Wear Particles (T&RWPs), Platinum Group Elements (PGEs), tungsten (W) and antimony (Sb)) in urban snow, (ii) size fractionation of pollutants in snow, (iii) behaviour of pollutants during snow melting, and (iv) influence of various snow sampling strategies on estimating pollutant loads in snow. Therefore, these four points form the focus of this doctoral thesis.The work presented in the thesis includes a literature review of metal pollution in urban snow, field sampling of urban roadside snowbanks and snow storage piles, and laboratory-scale snow melting experiments. The field sampling included snow sampling surveys at three locations in Sweden – Frihamnen (one of the ports of Stockholm), and Luleå and Umeå municipalities in Northern Sweden, and served for studies of variations in snow quality in terms of solids, metals, chloride, PAHs and MPs. Some of the field samples were also used in laboratory-scale snow melting experiments to advance the understanding of the fate of pollutants during the snow melting process.A literature survey identified Zn, Cu, Pb, Cd and Ni as the metals most frequently studied in urban snow, while Sb, W and PGEs in urban snow were seldom studied, and consequently were designated here as ‘emerging pollutants’ in urban snow. These pollutant concentrations in the analysed snow samples differed distinctly because of differences in study area characteristics such as meteorological conditions, traffic intensity and composition, and winter road maintenance as well as snow cover age (SCA). Investigation of estimation accuracies for pollutant loads in temporary snow storage piles highlighted the significant role of the sampling design. Single-column samples were prone to underestimating or overestimating the pollutant loads in snow piles, with variations of up to 400%, observed in the samples collected at Frihamnen. This underscores the importance of collecting and analysing multiple samples for reliable pollutant load assessments.Comparison of snow quality in three winter seasons (1994-95, 2002-03, and 2020-21) showed a statistically significant decrease in Pb and Cd concentrations in snow samples from 1995 to 2021. This decline may be associated with the regulations limiting these pollutants in car manufacturing industry and the phasing out of leaded gasoline.In the laboratory snow melting experiments, only 10% of both total metals (Cu, Zn, and Cd) and PAHs, and 20% of T&RWPs, were carried away by the meltwater, while the rest stayed in the (immobilised) sediment residue. The dissolved (<0.45 µm) and truly dissolved (<3000 MWCO) metals and chloride exhibited a preferential elution during melting, whereas TSS and PAHs displayed a delayed release.In summary, the thesis contributes to developing a comprehensive understanding of urban snow pollution dynamics and underscores the significance of, and need for, effective snow management for mitigating environmental impacts of urban snow pollution.
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| 9. |
- Viklander, Maria
(författare)
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Snow quality in urban areas
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The studies reported on this thesis aim to provide information and increase knowledge about the quality of urban snow and the path of pollutants. The results develop a basis for decisions regarding the prevention of environmental damage. A number of projects have been carried out to provide more detailed knowledge about: snow quality in cities, sediments that had accumulated during the winter, and that were left at the surface when the snow had melted, and the paths of pollutants at urban snow deposit. For these purposes studies have been performed in laboratory, pilot and full scale. The snow quality was studied in the city of Luleå with regard to variation with time and area. The aim was to investigate urban snow in its actual environment, throughout an entire winter season. Snow samples were taken in a housing area and in the city centre, at sites with different traffic load. It was found that traffic or activities related to traffic was a major source of heavy metals and phosphorus in urban snow, both in the city centre and the housing area. Also the type of area and the design of the street were important for the snow quality. A clear relation between the pH and the quantity of suspended solids in the snow was found. Higher pH values were found in snow from sites with higher traffic loads, compared to sites with small quantities of particles which were the no-traffic sites. The dissolved fractions showed more complicated results. The concentration of the studied substances in the snow was affected by the precipitation at the site with no traffic. At the street where the snow was left beside the street, the concentration of substances increased with time, while the precipitation was of less importance. The mass loads of substances increased with time for both the streets, where the snow stayed in the vicinity of the street, and for the non-traffic site. For the site with traffic the snow handling operations evidently affected the mass loads. This was especially the case for particle-connected substances. As a result of the increased interest in reuse of friction material the sediment which remained along the streets after snow melt was studied with regard to physical and chemical characteristics. The side walk affected the amount of substances on the street more than the traffic load. For the streets without sidewalk an increased traffic load increased the amounts of sediment. The particle size distribution of the sediments swept from the street with a sidewalk differed from the distribution at the streets without a sidewalk. With two exceptions the smallest size fraction (>75 µm) had the largest concentration of heavy metals. For composite samples the concentration increased with traffic load. The pathways of pollutants in urban snow deposits have been studied in three different scales; laboratory, pilot, and full-scale. The initial snow, melt water and sediment were analysed with regard to chemical content. It was found that the dissolved substances to a great extent folowed with the melt water while for the particle bounded substances as much as 90-99% stayed in the sediment below the deposit. The dissolved substances left the snow in the beginning of the melt period, while the substances connected to particles showed a uniform release. The laboratory study showed that melt- freeze cycles delayed the release of substances. Almost all substances were attached to particles in the snow, while in the melt water a large part was in solution. It should be noted that a so-called acid shock was not found during these studies.
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| 10. |
- Wei, Haoyu
(författare)
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Accumulation and Composition of Gully Pot Sediments under Varying Anthropogenic Activities
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gully pots (GPs) are an integral urban drainage component, contributing to conveying runoff from urban surfaces and reducing the load of solids and associated contaminants entering downstream piped systems and receiving waters. Over time, the silting-up of GPs impairs their hydraulic performance, increasing the risk of GP blockage-induced flood events and reducing solids retention performance. These challenges are typically addressed through GP emptying programmes. However, current GP maintenance strategies lack clear aims and a robust evidence-base, against which their effectiveness can be benchmarked. The overall aim of this doctoral thesis is to enhance understanding of the factors influencing the physicochemical properties and accumulation of solids in GPs, thereby laying the groundwork for further assessment and optimisation of GP maintenance strategies. The study encompasses various anthropogenic factors such as land use types, seasonal activities, traffic conditions, environmental regulatory measures, GP design and catchment characteristics. Research reported in this thesis includes both desk-based modelling (e.g. a study on sediment scour behaviours), and the results of an extensive field sampling campaign (sediments from a total of 87 GPs were assessed for dry masses, particle size distribution (PSD) and a range of conventional and emerging urban and traffic-related substances).The considerable variations in physicochemical properties, mass accumulation rates of sediments and associated contaminants in GPs question the utility of the prevalent generalised maintenance strategy. Although GPs in trafficked roads showed significantly higher solids mass accumulation rates compared to those in non-trafficked catchments, this factor alone could not fully explain observed variations. For example, whilst selected typically traffic-sourced contaminants such as 4-tert-octylphenol (OP) and heavy-molecular-weight polycyclic aromatic hydrocarbons (PAH-H) exhibited significantly higher concentrations in GP sediments from trafficked roads, further typically-traffic-related pollutants (e.g. aliphatic hydrocarbon > C16-C35 and Zn), as well as 4-nonylphenol (NP) and monobutyltin (MBT) were reported for GPs located in commercial and car parking land-use types. In terms of temporal dynamics, winter-spring road safety measures did not consistently result in significantly higher solids mass accumulation rates compared to summer-autumn accumulation data. However, where present, a greater influence of winter-spring road safety measures was identified under certain conditions. For example, GPs along straight roads with adjacent pedestrian/bicycle paths showed an up-to 130-fold increase in solids accumulation rates following winter-spring accumulation, largely due to the practice of using coarse traction grits in this road feature type. Synergistic impacts of winter-spring road safety measures and road layout features were also observed. This includes amplified tyre and road wear (a function of the combined use of studded tyres, traction grits and frequent braking at roundabouts) is identified as contributing to e.g. significantly higher mass fraction of <63 µm sediments and concentrations of Zn, Cd, OP, selected PAHs and phthalates in corresponding GPs following winter-spring accumulation. Additionally, significant temporal changes in basic parameters of GP sediments such as pH, electrical conductivity (EC) and total organic carbon (TOC) were identified, indicating substance phase changes (e.g. adsorption/desorption) at solid-liquid interfaces should be anticipated, and their impact considered when assessing GP sediment management needs.This research also contributes to sediment management through the characterisation of GP sediments for a broad list of contaminants. The comparison of sediment substance concentrations with Predicted No-Effect Concentrations (PNECs) (and, where these are not available, with Norwegian guideline values) indicated that 31 substances in at least one investigated GP exceeded threshold values. This demonstrates that GPs can accumulate contaminated sediments and underscores the need to revisit the role of GPs in mitigating runoff quality (and quantity) as part of an integrated urban stormwater management plan.
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