Microplastics in gully pot sediment in urban areas: Presence, quantities and characteristics.

Stormwater is widely recognized as a pathway for transporting pollutants, including microplastics, from sources in urban environments to receiving waters. Gully pots are often where urban runoff drains into the piped network; they typically include a trap where sediments accumulate. The aim of this work was to contribute to a better understanding of the fate of microplastics as they enter into the urban drainage system, and the role of gully pots in trapping microplastics. Sediment samples collected from 29 gully pots were analysed for non-carbon-black and carbon-black (e.g. tire wear particles) microplastics larger than 40 µm using µ-FTIR and ATR-FTIR, respectively. Commonly found polymers in descending order were PP>EPDM>EVA>PS>SBR, PP was most common both by mass and by number of microplastics. The total concentration of carbon black and non-carbon black microplastics ranged from 709 to 10 600 items/100 g dry matter (DM), (median: 2960 items/100 g). Estimated mass of non-carbon black microplastics ranged from 0.19 to 490 mg/100 g, (median: 3.66 mg/100 g). In total 21 different types of microplastics were detected, the majority of these (13) were carbon black and eight non-carbon black polymer types. By number and the carbon black particles accounted for up to 68% of the microplastics (average 30%), this stress the importance of using analytical methods enabling the detection of both carbon-black and non-carbon black microplastics. Furthermore, the results indicate that gully pots can act as temporary sinks for microplastics, mainly for microplastics larger than 125 µm. The amount of microplastics found in gully pots, together with the very large number of gully pots sited in urban areas, indicates that gully pots can potentially trap large amounts of microplastics, and thus if gully pots are fitted and maintained properly they could significantly contribute to reducing the amount of microplastics reaching receiving waters.

Traffic-related metals in urban snow cover: A review of the literature data and the feasibility of filling gaps by field data collection.

A literature search on traffic related metals in polluted urban snow revealed a significant volume of references representing a substantive knowledge base. The frequently studied metals in urban snow included Zn, Cu, Pb, Cd and Ni. However, comparing metal concentrations across studies proves to be a complex effort due to the variations in site-specific factors among studies, such as traffic intensity, pavement conditions, hydrometeorological conditions, and research method aspects, such as sampling equipment and frequency, and laboratory analytical methods. The literature review indicated that among the commonly studied metals, Zn and Cu indicated potential environmental concerns, and that there was a lack of data on the occurrence and accumulation in snow of antimony (Sb), tungsten (W), and platinum group elements (PGEs). To partly mitigate this knowledge gap, a field study of these elements was carried out by sampling urban roadside snow at six locations with various land use and traffic intensities, focusing on accumulation of these elements in snowbanks along roadways. The results indicated that traffic related activities are the sources of PGEs, W and Sb in roadside snowbanks, as the concentrations of these metals increased with increasing traffic intensity. The mean concentrations of the studied metals followed this descending order: W (0.4 (Reporting limit-RL)-987 µg/l) > Sb (0.1 RL-33.2 µg/l) > Pd (0.02 (RL)-0.506 µg/l) > Rh (0.02 (RL)-0.053 µg/l). In laboratory melted snow, both W and Sb were mostly in the particulate-bound phase, with <25 % in the dissolved phase. For sites with metal concentrations above the detection limit, the regression analysis indicated linear trends in unit area deposition rates of W with time (snow age), described by R2 = 0.94.

Impacts of stormwater pipe materials and pipe repairs on stormwater quality: a review.

The water quality implications of transferring stormwater through pipes composed of concrete (new and used), polyvinyl chloride (PVC), galvanized corrugated steel (GCS), high-density polyethylene (HDPE), and pipes subjected to cured in place pipe (CIPP) and spray in place pipe (SIPP) trenchless repair technologies on stormwater quality are reviewed. Studies involve either the use of flowing water or an immersion experimental design, with data showing contact with pipe materials can affect stormwater quality parameters including pH, electrical conductivity (EC), and concentrations of minerals, metals, and organic constituents, e.g. styrene. 'In-transport' changes in pH (1-3 units), EC (2-3-fold), bicarbonate (3-44-fold), and calcium (2-17-fold) in stormwaters were reported following exposure to concrete pipes. Differences between the use of synthetic and field-collected stormwater were identified, e.g. turbidity levels in field-collected stormwater reduced on passage through all pipe types, compared to synthetic water where levels of turbidity on exposure to concrete and cement-based SIPP increased slightly. Transfer through PVC and HDPE pipes had minimal effects on physicochemical parameters, whereas exposure to galvanized corrugated steel pipes led to increases in EC, Zn, and Pb. Though limited data was available, the use of CIPP repairs and associated waste condensate generated during thermal curing and/or incomplete curing of resins was identified to release organic contaminants of concerns (e.g. styrene, vinylic monomers, dibutyl phthalate (DBP), diethyl phthalate (DEP), and benzaldehyde). The implications of findings for both future research and stakeholders with responsibility for reducing diffuse pollution loads to receiving waters are considered.

Accumulation and contamination of gully pot sediments from varied land-use types: metal loads, concentrations and speciation.

Urban stormwater typically enters sewer networks through gully pots, which allow a primary sedimentation of solids upstream of the piped network. The regular removal and disposal of retained sediment are necessary, costly and can involve environmental risks due to the contamination of sediments with substances from the urban environment such as metals. The concentrations and speciation of Cd, Cr, Cu, Ni, Pb and Zn were analysed in sediments from 26 gully pots located in different land use areas in Stockholm, Sweden. In addition, accumulation rates of both sediment and metal masses were evaluated, providing a basis for optimising maintenance practices and better understanding of impacts of characteristic urban land use types. Metal concentrations varied by at most a factor of eight between samples and were always below Swedish polluted site guidelines for less sensitive land use, with only eight samples exceeding the guideline values for Cu and Zn for sensitive land use. Sequential extraction showed Pb and Zn to be the most mobile metals. Sediment accumulation rates varied from 0.003 to 0.197 kg/m2 impermeable surface/year. Metal accumulation rates were much more variable than metal concentrations, with a factor of up to 172 between the highest and lowest rates and the highest metal accumulation rates corresponding to the lower range of mass loads in road runoff. Differences in metal concentrations, sediment or metal mass accumulations could not be solely attributed to either traffic or catchment land use. In contrast, traction grit used for winter road maintenance, which has low (but detectable) metal concentrations, is identified as a major component of gully pot sediments, with a combined effect of both moderating metal concentrations and contributing to total mass.

Releases of micropollutants from building surface materials into rainwater and snowmelt induced runoff.

Building surface materials, exposed to wash-off by rainwater or snowmelt, are recognised as one of the significant urban diffuse pollution sources contributing to the impairment of stormwater quality. The pollution conveyed by roof runoff originates from two potential sources, migration of surface material constituents, or wash-off of pollutants deposited on the surface by atmospheric deposition. This study investigated the releases of metals and several groups of contaminants of emerging concern: alkylphenols, alkylphenol ethoxylates, and phthalates, from commercially available materials, which are commonly used on buildings and structure surfaces in the urban environment. The materials tested included the following: metal sheets of stainless steel, copper, zinc, galvanised steel, corten steel, corrugated and coated steel, coated zinc; and bitumen-based roofing felt and shingles, as well as polyvinyl chloride (PVC) from two manufacturers. The stainless steel was considered a control material serving to estimate pollutant contributions deposited on the pilot panels from the surrounding environment. Moreover, this study presents novel data on roof snowmelt induced runoff quality, not reported in the previous literature. The experimental setup consisted of 2-m2 rectangular panels mounted in triplicates of each material and placed in an open-air setting on the campus of Luleå University of Technology, Sweden. Runoff leaving the gently sloping material panels was collected during 11 rain and three snowmelt driven runoff events occurring over a five-year period. The results showed that, in general, the micropollutant concentrations and loads were lower in snowmelt than rain induced runoff, and no decreasing trend was detected in the releases of phthalates or metals during the study period. Moreover, on a yearly basis, copper sheets were estimated to release 0.6 g/m2 Cu to runoff, zinc and galvanised sheets 1.3 and 0.7 g/m2 Zn, respectively, and, PVC sheets were estimated to release up to 78 mg/m2 of diisononyl phthalate (DINP).

Abundance, distribution, and composition of microplastics in the filter media of nine aged stormwater bioretention systems.

Bioretention systems are designed for quality treatment of stormwater. Particulate contaminants are commonly treated efficiently and accumulate mainly in the surface layer of the bioretention filter material. However, concerns exist that microplastic particles may not show equal accumulation behavior as other sediment particles. So far only two field and two laboratory studies are available on the fate of microplastics in few relatively newly built bioretention systems. Therefore, this study investigated the abundance and distribution of microplastics in nine 7-12 years old stormwater bioretention systems. It was found that microplastics generally accumulate on the surface of bioretention systems. Microplastic median particle concentrations decreased significantly from the surface layer (0-5 cm) of the filter material to the 10-15 cm depth layer from 448 to 136 particles/100 g, respectively. The distance to the inlet did not significantly affect the surface accumulation of microplastic particles, suggesting modest spatial variability in microplastics accumulation in older bioretention systems. Further, this study investigated the polymer composition in bioretention systems. It was shown that PP, EVA, PS and EPDM rubber are the most abundant polymer types in bioretention systems. Also, it was found that large percentages of microplastic particles are black particles (median percentage of black particles: 39%) which were found in 28 of the 33 investigated samples. This underlines the importance of including black particles in microplastic studies on stormwater, which has been overlooked in most previous studies.

Microplastics in urban catchments: Review of sources, pathways, and entry into stormwater.

Urban areas play a key role in the production of microplastics (MPs) and their entry into water bodies. This article reviews the literature on the sources, transport, and control of MPs in urban environments with the aim of clarifying the mechanisms underlying these processes. Major MP sources include atmospheric deposition, micro-litter, and tire and road wear particles (TRWPs). MPs deposited from the atmosphere are mostly fibers and may be particularly important in catchments without traffic. Littering and attrition of textiles and plastic products is another important MP source. However, the quantities of MPs originating from this source may be hard to estimate. TRWPs are a significant source of MPs in urban areas and are arguably the best quantified source. The mobilization of MPs in urban catchments is poorly understood but it appears that dry unconsolidated sediments and MP deposits are most readily mobilized. Sequestration of MPs occurs in green areas and is poorly understood. Consequently, some authors consider green/pervious parts of urban catchments to be MP sinks. Field studies have shown that appreciable MP removal occurs in stormwater quality control facilities. Street cleaning and snow removal also remove MPs (particularly TRWPs), but the efficacy of these measures is unknown. Among stormwater management facilities, biofiltration/retention units seem to remove MPs more effectively than facilities relying on stormwater settling. However, knowledge of MP removal in stormwater facilities remains incomplete. Finally, although 13 research papers reported MP concentrations in stormwater, the total number of field samples examined in these studies was only 189. Moreover, the results of these studies are not necessarily comparable because they are based on relatively small numbers of samples and differ widely in terms of their objectives, sites, analytical methods, size fractions, examined polymers, and even terminology. This area of research can thus be considered "data-poor" and offers great opportunities for further research in many areas.

Microplastics (MPs) in urban roadside snowbanks: Quantities, size fractions and dynamics of release.

The microplastics (MP) pollution has been receiving high attention in recent years, because of the massive amounts of plastics it contributes to the environment. Tyre wear and road wear particles (TWP and RWPs) were identified as major sources of MPs, but the observed data on these particles in urban snow deposits and snowmelt is scarce. To contribute to remediation of this situation, a study designed to quantify TWPs and RWPs in urban roadside snowbanks, and assess the MP occurrence in three size fractions, was conducted in the Luleå and Umeå municipalities in Northern Sweden. TWPs and RWPs were determined in three size fractions: 50-100 µm, 100-300 µm, and ≥300 µm, and their release from melting snow was investigated in the laboratory under controlled conditions. Among the MPs identified in snow and the associated snowmelt samples, a majority consisted of both types of particles (T&RWPs) with an average of 20,000 ± 48,000 number/L, whereas other MPs (fibres, fragments, flakes, and films of plastic) were much less plentiful with an average concentration of 24 ± 16 number/L. The largest proportion of T&RWPs was detected in the size fraction 50-100 µm (around 80%), and the smallest proportion was in the fraction ≥300 µm (about 2%). Of the T&RWPs, about 85% were black bitumen particles (RWPs), composed of bitumen, mineral material and polymer modifiers, and 15% were tyre wear particles (TWPs) composed of rubber. The laboratory snow melting experiments demonstrated that urban snow stored MPs, which were eventually released during snowmelt. The ultimate fate of released MPs would depend on snowmelt drainage; it may either drain away from the road pavement and infiltrate into the ground, or enter the road gutter and be conveyed to storm sewers discharging to the receiving waters.

Exploiting urban roadside snowbanks as passive samplers of organic micropollutants and metals generated by traffic.

Stormwater and snowmelt runoff is known to contribute to the deterioration of quality of urban surface waters. Vehicular traffic is recognised as a major source of a wide range of pollutants to urban runoff, including conventional pollutants, such as suspended solids and metals, and those referred to as 'contaminants of emerging concern'. The aim of this study was to investigate the contribution of selected metal(loid)s (Cd, Cr, Cu, Ni, Pb, Pd, Sb, W, Zn), polycyclic aromatic hydrocarbons (PAHs), nonylphenols, octylphenols and -ethoxylates, phthalates and bisphenol A (BPA) from vehicular traffic by sampling urban roadside snow at eight sites, with varying traffic intensities, and one control site without direct impacts of traffic. Our results confirmed that vehicles and traffic-related activities were the sources of octylphenols, BPA and phthalates as well as the metal(loid)s Sb and W, infrequently reported in previous studies. Among metal(loid)s, Cu, Zn and W occurred in the highest concentrations (up to 1.2 mg/L Cu, 2.4 mg/L Zn and 1.9 mg/L W), while PAHs and phthalates occurred in the highest concentrations among the trace organic pollutants (up to 540 µg/L phthalate diisononyl phthalate). Among the phthalates, di-(2-ethylhexyl)phthalate had the highest frequency of detection (43% of the roadside samples). While BPA and octylphenols had relatively high frequencies of detection (50% for BPA and 81% for octylphenols), they were present in comparatively low concentrations (up to 0.2 µg/L BPA and 1.1 µg/L octylphenols). The control site displayed generally low concentrations of the pollutants studied, indicating that atmospheric deposition was not a significant source of the pollutants found in the roadside snow. Several of the pollutants in the roadside snow exceeded the applicable surface water and stormwater effluent guideline values. Thus, the transport of these pollutants with runoff posed risk of causing adverse effects in the receiving surface waters.

Facilitating maintenance of stormwater ponds: comparison of analytical methods for determination of metal pollution.

Stormwater ponds are widely used for controlling runoff quality through the sedimentation of particles and associated pollutants. Their maintenance requires regular removal and disposal of accumulated material. This necessitates an assessment of material hazardousness, including potential hazard due to its contamination by metals. Here we analyze 32 stormwater pond sediment samples from 17 facilities using several chemical analysis methods (total extraction, sequential extraction, diffusive gradients in thin-films DGT, and pore water extraction) in order to consider the complementarity and comparability of the different approaches. No clear relationship was found between analyses that have the potential to measure similar metal fractions (DGT and either fraction 1 of the sequential extraction (adsorbed and exchangeable metals and carbonates) or pore water concentrations). Loss on ignition (LOI) had a significant positive correlation with an indicator of the environmental risk developed in this paper (∑ranks) that incorporates different metals, speciations, and environmental endpoints. Large variations in metal levels were observed between ponds. As clustering was limited between the different analyses, a comprehensive analysis of different parameters is still needed to fully understand metal speciation and bioavailability.

Occurrence and concentration of 20-100 µm sized microplastic in highway runoff and its removal in a gross pollutant trap - Bioretention and sand filter stormwater treatment train.

Microplastic pollution of stormwater can be a serious threat to the environment. Gross pollutant trap (GPT) - bioretention treatment trains have been shown previously to treat (inter alia) particulate stormwater pollutants including microplastic particles larger than 100 µm. This study was carried out to investigate whether such stormwater treatment trains also remove smaller 20 to 100 µm sized microplastic particles from highway runoff. Further, it investigates occurrence and concentration of 20 to 100 µm sized microplastic particles in highway runoff and which polymer types they can be assigned to. Volume proportional samples from nine rain events were taken from the incoming highway stormwater, from the gross pollutant trap effluent and the outflow from a bioretention system as well as a non-vegetated sand filter. The microplastic analyses were carried out using µFTIR and FTIR-ATR, which made it possible to detect particles where carbon black was present. It was found that 20 to 100 µm sized microplastic particles are abundant in highway runoff and that their concentrations are highly variable, with a median of 230 particles/L, a minimum of 42 particles/L and a maximum of 8577 particles/L. The dominant polymer types in highway stormwater were Polypropylene (PP), Ethylene Propylene Diene (EPDM) rubber and Ethylene-vinyl acetate (EVA). The treatment train with the bioretention system treated 20 to 200 µm sized microplastic particles significantly better than the treatment train with a non-vegetated sand filter, with median effluent concentrations of 26.5 particles/L and 121 particles/L, respectively. The GPT had no significant impact on the treatment of 20 to 100 µm sized microplastic particles.

Comparison of three explorative methods for identifying building surface materials contributing pollutants to stormwater.

Runoff from building and structure surfaces may contribute to the pollution of urban stormwater and, thereby, to the degradation of the receiving water quality. Various micropollutants have been found in surface runoff from buildings in the urban environment, including metals and organic micropollutants. Effective methods for identification of such pollutants and their sources are the prerequisites for the development of control measures. In this paper, three different methods for the identification of building surface materials acting as sources of metals (Cd, Cr, Cu, Ni, Pb and Zn), nonylphenols and phthalates are presented: (i) screening of the material composition, (ii) laboratory leaching experiments with synthetic rainwater, and (iii) open-air pilot testing of material panels exposed to actual rainfall and runoff. These three methods cover a wide span of experimental aspects, including, e.g., size of material samples, resource demands, and control of influential factors. Nine materials commonly used on building and structure surfaces in the urban environment were tested: metal sheets of zinc, copper, galvanised steel, coated corrugated steel and stainless steel; and, four different roofing membranes of bitumen as well as polyvinyl chloride (PVC). The experimental results indicated that all three methods were meritorious in providing some information contributing to the identification of pollutant sources. The screening of material composition for targeted pollutants is relatively quick and inexpensive, but may fail to identify minor sources of pollutants, or may identify the substances present in the material, but not released in contact with water. Laboratory leaching was generally effective in identifying sources of substances present in surface runoff, but was unsuitable for estimating the magnitude of actual concentrations in building runoff. Open-air pilot studies of material samples (exposed area = 2 m2) were thought to provide the results corresponding well to concentrations in runoff from actual building surfaces, but required relatively large financial and labour resources. Thus, the choice of the method for pollutant identification should be based on study objectives, and some benefits may be achieved using more than one method in an integrated manner; e.g., composition screening and lab or open-air leaching of targeted materials.

Evaluation of measured dissolved and bio-met predicted bioavailable Cu, Ni and Zn concentrations in runoff from three urban catchments.

Urban runoff is a diffuse source of pollution contributing to the poor ecological and chemical status of surface waters. Whilst the EU Priority Hazardous Substances Directive now identifies environmental quality standards for selected metals in relation to the bioavailable metal fraction the relationship between analytically determined metal size fractions transported by urban runoff and the often variably defined concept of bioavailability has not been thoroughly evaluated. This paper provides a review of the terminology used within urban runoff studies to characterise metal fractions and behaviour. Measured dissolved and truly dissolved (determined by ultrafiltration; <3000 molecular weight cutoff) Cu, Ni, and Zn concentrations are also compared to the bioavailable metal fraction (as predicted using Bio-met, a simplified biotic ligand model) in snowmelt and rainfall derived runoff samples from three urban catchments. The study shows that predicted bioavailable concentrations were significantly lower than truly dissolved concentrations for all metals and discusses current bioavailability modelling parameters in relation to rainfall and snowmelt runoff data sets. Statistical analysis of relationships between field and predicted bioavailable data sets indicate that the bioavailable fractions originate from both colloidal and truly dissolved fractions.

Contamination of Urban Stormwater Pond Sediments: A Study of 259 Legacy and Contemporary Organic Substances.

Stormwater ponds improve water quality by facilitating the sedimentation of particles and particulate contaminants from urban runoff. Over time, this function entails the accumulation of contaminated sediments, which must be removed periodically to maintain a pond's hydraulic and treatment capacity. In this study, sediments from 17 stormwater sedimentation facilities from four Swedish municipalities were analyzed for 259 organic substances likely to be found in the urban environment. A total of 92 substances were detected in at least one sample, while as many as 52 substances were detected in a single sample. A typical profile of urban contamination was identified, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, organotins, aliphatic hydrocarbons, phthalates, aldehydes, polybrominated diphenyl ethers, perfluorinated substances, and alkylphenols. However, levels of contamination varied greatly between ponds, influenced heavily by the dilution of urban pollutants and wear particles from other sources of particles such as eroded soil, sand, or natural organic matter. For 22 of 32 samples, the observed concentrations of at least one organic substance exceeded the regulatory threshold values derived from toxicity data for both sediment and soil.

Metal enrichment of soils in three urban drainage grass swales used for seasonal snow storage.

Enrichment of soils in three urban drainage swales by metals associated with traffic sources was investigated in a cool temperate climate with seasonal snow. Such swales differed from those not exposed to snow by receiving additional pollutant loads from winter road maintenance involving applications of salt and grit, use of studded tires, and storage and melting of polluted snow cleared from trafficked areas into swales. Among the swales studied, swale L2 in the downtown was the oldest (built around 1960), drained runoff from a road with the highest traffic intensity, and exhibited the highest mean concentrations of most of the metals studied (Pb, Cu, Zn, Cr, Cd, Ni, Co, V, Ti, and W). In the case of Pb, this exceedance was about an order of magnitude: 71 mg/kg DW in L2, compared to about ~8 mg/kg DW in L1 and L3, both built in 1979. Among the metals originating from local geology, barium (Ba) was found in the swales and the grit material at high concentrations of ~650 mg/kg DW and 700-1000 mg/kg DW, respectively. Such concentrations exceeded the Swedish EPA guideline limits of 300 mg/kg DW for less sensitive soil use. The sequential extraction analysis of samples from swale L2 indicated that Ba was mostly in the immobile residual fraction (90%). The absence of clear decline in metal concentrations with distance from the trafficked surfaces suggested that stored snow was another source of metals partly balancing spatial distribution of metals in swale soils.

Metal size distribution in rainfall and snowmelt-induced runoff from three urban catchments.

The size distribution of metals transported by urban runoff has implications for treatment type and design, predicting their mobility and evaluating their potential impact on receiving waters. There is an urgent need to better understand the distribution of metals between fractions, particularly those in the sub-dissolved fractions. As a contribution to addressing this need, this study characterises the size distribution of Cd, Cr, Cu, Ni, V and Zn using conventional and novel techniques. Data is presented as event mean concentrations (EMC) of a total of 18 rainfall and snowmelt events at three urban sites. For all studied metals in all events and at all sites, the contribution of the truly dissolved fraction made a greater contribution to the total concentrations than the colloidal fraction. Truly dissolved Cd and Zn concentrations contributed (on average) 26% and 28% respectively, of the total EMCs with truly dissolved Cu and Ni contributing (on average) 18%. In contrast, only 1% (V) and 3% (Cr) were identified in the truly dissolved fraction. The greatest contribution of truly dissolved Cd, Cu and Zn concentrations (relative to total concentrations) were reported during rainfall events. However, no seasonal differences were identified and differences between the sites regarding the EMCs distribution by fractions were not at a statistically significant level (p > 0.05) for any metal or event. The loads of truly dissolved and colloidal metals did not follow the patterns of particulate metal loads indicating particulates are not the main source of sub-dissolved metals. The data suggests that ultrafiltration as a treatment technique would not efficiently mitigate the risks posed by metals to receiving water ecologies.

Metal speciation in stormwater bioretention: Removal of particulate, colloidal and truly dissolved metals.

For comprehensive estimation of the metal treatment efficiency of bioretention systems, information on metal speciation in the stormwater and the effluent is needed. However, so far, most bioretention studies only considered total metal concentrations. Despite their environmental importance, dissolved metals (defined as fractions < 0.45 µm) have only been evaluated in few studies. This study represents the first bioretention study to subdivide the <0.45 µm fraction further by filtration through a 3 kDa ultrafilter (corresponding to appr. 2-3 nm), thus enabling distinction between particulate, colloidal and truly dissolved metals. Higher bioavailability of the truly dissolved fraction has been indicated by previous research, underlining the importance of this study. Since vegetation and salt in stormwater both may be explanatory variables for metal fractionation, these have been added as factors in the utilized full factorial pilot-scale column experiment. While total metal removal was often >95%, detailed fractionation revealed that Cu and (when no salt was added) Zn removal in the <0.45 µm and <3 kDa fractions was significantly lower. Further, mean concentrations of Cu and (in one treatment) Cd in the <0.45 µm effluent fraction did not meet Swedish receiving water quality guidelines. By calculating the particulate, colloidal and truly dissolved fractions, it was shown that bioretention systems affect metal speciation of Cu and Zn. Colloidal and truly dissolved fractions were mostly prevalent in the effluent rather than the influent. Salt affected metal removal mostly negatively. Fractionation was affected by salt mainly in the influent where it increased the concentrations of Cd and Zn in the truly dissolved fraction (no effects on Cu and Pb fractions). In the effluent, Cu and Zn were only slightly affected by salt. Vegetation had mostly no significant effects on metal removal and fractionation. Further integration of detailed metal fractionation into sampling routines in bioretention research is recommended.

The pollution conveyed by urban runoff: A review of sources.

Urban stormwater and snowmelt pollution contributes significantly to the deterioration of surface waters quality in many locations. Consequently, the sources of such pollution have been studied for the past 50 years, with the vehicular transportation sector and the atmospheric deposition identified early as the major pollution sources. In search for mitigation of this pollution, source controls, besides other measures, were recognised as effective pollution mitigation tools, whose successful implementation requires a good knowledge of pollution sources. Even though great research efforts have been exerted to document specific sources of urban runoff pollution, or specific groups of pollutants present in urban runoff, a comprehensive overview of all known contributing sources is still missing. This review contributes to closing this gap by compiling findings of previous research and critically synthesizing the current knowledge of various stormwater pollution sources. As the emphasis is placed on the sources, the related issues of implications for urban surface water quality and possible source controls for individual sources are touched upon just briefly, where required. The review showed that the atmospheric deposition, vehicular transportation-related activities and metallic building envelopes continue to be among the major pollution sources, which have been studied in a far greater detail than other sources. Furthermore, it was noted that because of the rapid advances in clean manufacturing and pollution control technologies, a large part of the body of data on stormwater quality available in the literature should be considered as historical data, which may no longer describe well the current conditions. Progressing historical data obsolescence, combined with continuing releases of new materials and chemicals, and, in some cases of new substances of potential concern, into the environment, suggests that the identification of important stormwater runoff/snowmelt pollution sources, and the associated pollutants, has been and will remain to be a work in progress.

Building surface materials as sources of micropollutants in building runoff: A pilot study.

Control of diffuse pollution is critical for achieving good surface water quality status. In this context, pollutant contributions from building materials have received increased attention in recent decades. This study examined the releases of metals, nonylphenols and phthalates from ten common building surface materials (installed in triplicates) into rainwater runoff from six rain events. The highest releases of metals were from copper and zinc sheets (average concentrations of 3090 µg/L Cu and 7770 µg/L Zn respectively), while other metal materials, e.g., Corten weathering steel, exhibited lower releases. PVC roofing released high concentrations of nonylphenols and phthalates (average concentrations of up to 26 µg/L nonylphenols and 455 µg/L Diisononyl phthalate, DINP) which have not been investigated in the earlier studies. Pollutant releases varied between events, likely because of weather conditions and rainfall characteristics. Study findings should be valuable for environmentally responsible applications of the existing building materials and the development of new ones, as well as the investigations and risk assessment of specific pollutants in stormwater.