Quantifying evapotranspiration fluxes on green roofs: A comparative analysis of observational methods.

Evapotranspiration (ET) is an important process in green stormwater infrastructure (GSI) aiming to reduce urban drainage, to promote cooling and/or to contribute to an urban hydrological balance restoration closer to the natural one. However, on these structures and particularly on green roofs (GR), its evaluation remains challenging and subject to discussion. Estimates of ET by water balance, energy balance, and an ET chamber were performed on five different plots of a full-scale experimental green roof in Trappes (France). Compared to both water balance (90th percentile range of daily ET values: 0.8 mm/d to 3 mm/d) and chamber methods (90th percentile range of daily ET values: 1 mm/d to 1.5 mm/d), the energy balance (90th percentile range of daily ET values is between 1.8 mm and 3.7 mm) produces higher values, 1 to 2 times higher in cumulative values during common periods. The chamber ET displays a similar trend to the energy balance on an hourly basis, and its values remain within the same range as the water balance evaluations on a daily time-step. All three assessments consistently fell below the potential ET values estimated with the Penman-Monteith formula. Critical issues in ET estimation through experimentation have arisen. Sensible heat flux (H) significantly increases ET values when using the energy balance approach compared to the other two methods. The Water Balance method is practical, but on days following rainfall events, the Chamber method may prove more reliable, albeit more time and labour-intensive. The three methods indicated that the substrate thickness was the main contributing factor to increase ET, with well-maintained herbaceous plants providing higher ET values than sedums in thick (15 cm) substrates. In addition, the substrate's nature, especially its organic content, is another factor that promotes ET in green roofs.

A decade of monitoring micropollutants in urban wet-weather flows: What did we learn?

Urban wet-weather discharges from combined sewer overflows (CSO) and stormwater outlets (SWO) are a potential pathway for micropollutants (trace contaminants) to surface waters, posing a threat to the environment and possible water reuse applications. Despite large efforts to monitor micropollutants in the last decade, the gained information is still limited and scattered. In a metastudy we performed a data-driven analysis of measurements collected at 77 sites (683 events, 297 detected micropollutants) over the last decade to investigate which micropollutants are most relevant in terms of 1) occurrence and 2) potential risk for the aquatic environment, 3) estimate the minimum number of data to be collected in monitoring studies to reliably obtain concentration estimates, and 4) provide recommendations for future monitoring campaigns. We highlight micropollutants to be prioritized due to their high occurrence and critical concentration levels compared to environmental quality standards. These top-listed micropollutants include contaminants from all chemical classes (pesticides, heavy metals, polycyclic aromatic hydrocarbons, personal care products, pharmaceuticals, and industrial and household chemicals). Analysis of over 30,000 event mean concentrations shows a large fraction of measurements (> 50%) were below the limit of quantification, stressing the need for reliable, standard monitoring procedures. High variability was observed among events and sites, with differences between micropollutant classes. The number of events required for a reliable estimate of site mean concentrations (error bandwidth of 1 around the "true" value) depends on the individual micropollutant. The median minimum number of events is 7 for CSO (2 to 31, 80%-interquantile) and 6 for SWO (1 to 25 events, 80%-interquantile). Our analysis indicates the minimum number of sites needed to assess global pollution levels and our data collection and analysis can be used to estimate the required number of sites for an urban catchment. Our data-driven analysis demonstrates how future wet-weather monitoring programs will be more effective if the consequences of high variability inherent in urban wet-weather discharges are considered.

Intra- and inter-site variability of soil contamination in road shoulders - Implications for maintenance operations.

This study addresses soil contamination in vegetated road shoulders with diffuse inflow of runoff. It aims (i) to characterize the spatial distribution of three metals (copper, lead, zinc) and PAHs, and (ii) to identify influencing factors for the inter-site differences. An extensive sampling campaign was carried out on forty road segments in the Paris region, targeting various distances and soil depths. Copper and zinc contamination was found to be mainly restricted to the first 30 cm from the road, where their concentrations ranged respectively between 40 and 270 mg.kg-1, and between 150 and 950 mg.kg-1 (with a few additional extreme values related to the presence of a galvanized steel guardrail). Lead contamination was moderate (< 100 mg.kg-1 in more than 75% of the sites) and relatively uniform across the width of the shoulders. Conversely, highest PAH concentrations were found further from the road. These differences between contaminants were likely due to the varying importance of wet weather-related processes and atmospheric transport in their dispersion mechanisms. Copper and zinc concentrations correlated well with the traffic density, which alone explained ≥ 69% of the inter-site variability, whereas lead and PAHs did not exhibit such dependence. Soil organic matter was found to control the "ceiling" concentration of metals, thus limiting the maximum amounts that can be intercepted from road runoff. These results illustrate the feasibility of estimating contamination levels on road shoulders, and thus offer interesting perspectives for better consideration of the infrastructures' maintenance needs and improved routine operations.

An Investigation of the Accuracy of EC5 and 5TE Capacitance Sensors for Soil Moisture Monitoring in Urban Soils-Laboratory and Field Calibration.

Recently, emphasis has been placed on finding a reliable estimation of soil water content. In this study, two capacitance sensors EC5 and 5TE (METER Group) were utilized. These sensors provide many benefits relative to other sensors in that they are cost-effective and very economical regarding energy use, operate at a high measurement frequency of 70 MHz, and are dedicated to measuring at a small volume because of their small size. This makes them suitable for the context of use in this research, which consists of multiple sustainable drainage systems SuDS. Several studies have evaluated these two types of sensor but not for urban soils with specific characteristics. In addition, results from the literature are divergent and the published calibration data are limited. Therefore, an in-depth investigation of their accuracy is assessed in this paper. At first, the literature's existing procedures and methods were examined. The sensor-to-sensor variability, as well as repeatability, were tested in soil and solutions. Additionally, a field calibration method was conducted to estimate the effects of soil texture on sensors readings. Two laboratory calibration methods having different principles were also applied, compared to each other and to the field calibration as well. Results revealed weak sensor-to-sensor variability (coefficient of variation up to 15% in soil) and also good repeatability (0.1%), for both sensors. A soil-specific calibration equation has improved the estimation of the volumetric water content. In case of soil having high field bulk density, the undisturbed soil calibration method described and proposed in this paper gives promising results. The latter method yields a volumetric water content (VWC) prediction accuracy of 0.025 m3∙m-3 on a sandy loam soil. This paper presents a large knowledge of capacitance sensors measurement technique as well as their calibration procedures and methods. Limitations of existing procedures have been identified and key elements for selecting the appropriate one are suggested. Derived calibration equations have also been provided for three urban soils with different particle size distribution, ranging from sandy loam to silt loam. Accurate monitoring of soil moisture content in urban soils is thus achievable.

Retention and transport processes of particulate and dissolved micropollutants in stormwater biofilters treating road runoff.

Road runoff is contaminated by various micropollutants and may be treated using low impact development techniques, such as stormwater biofilters. Better understanding the processes, such as filtration, sorption and leaching, which affect pollutants in these systems is essential to reliably predicting treatment performance and optimizing system design. Field data from an in situ monitoring campaign, wherein dissolved and particulate concentrations of a wide range of micropollutants (trace metals, polycyclic aromatic hydrocarbons, bisphenol-A, alkylphenols and phthalates) were characterized in untreated road runoff and biofilter outlets for 19 rain events, are used to explore transport and retention processes. Although retention of the particulate phase of pollutants was generally quite effective, unusually high particle concentrations were observed at biofilter outlets for three winter events. Particle characterization in road runoff and outlet waters revealed that this degraded performance was due to poor filtration rather than particle erosion, which was attributed to the relative abundance of small (<10 µm) particles during this period, along with possible preferential flows. Dissolved pollutants were less effectively removed in general. To better understand this behavior, field results were combined with laboratory sorption and leaching tests. Dissolved concentrations of trace metals were shown to be influenced by organic carbon; leaching from road-originated particles may also influence their transport. Removal of the dissolved phase of organic micropollutants was limited by the contamination of the filter media, either before installation or during the first period of operation, due to emissions from construction materials.

Field performance of two biofiltration systems treating micropollutants from road runoff.

The treatment efficiency of a vegetative filter strip and a biofiltration swale treating heavily loaded road runoff are evaluated. Concentrations measured in water drained from the two systems are compared to those in untreated road runoff collected from a reference catchment for a wide range of contaminants including organic carbon, nutrients (N and P), trace metals, and organic micropollutants (polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), alkylphenols, bisphenol-A, phthalates), in both total and dissolved phases. Predominantly particulate pollutants, including Pb, Zn and PAH, were very efficiently removed (around 90%) for most events. However, poor particulate removal was observed during a winter period. Relatively few pollutants were significantly removed in the dissolved phase and observed concentration reductions tended to be lower than those of suspended solids and associated pollutants; as such, lower removals were observed for total concentrations of moderately particulate micropollutants, including bisphenol-A, alkylphenols and phthalates. In addition, some pollutants appear to be emitted from various biofilter components (filter media, drainage and lining materials), as low or negative concentration removals were observed during the first months of operation of the biofiltration swale.

Alkylphenol and bisphenol A contamination of urban runoff: an evaluation of the emission potentials of various construction materials and automotive supplies.

Alkylphenol (AP) and bisphenol A (BPA) contamination of urban runoff has already been established. Potential sources of these contaminants in runoff are endogenous to the urban watershed and are mainly related to traffic and leaching from construction materials. This article summarizes the results of experimental work carried out on a selection of building materials, automotive materials, and consumables, which can be in contact with rain, to assess their potential emission of alkylphenols, alkylphenol ethoxylates, and bisphenol A into runoff. 36 samples of materials, new and used, across 7 major families of building materials (PVC, concrete, polycarbonate, SBS-modified bitumen, drainage materials) and automotive materials (body, tires) were subjected to leaching tests with methanol and then, for a selection of them, with water. Automotive fluids were also directly analyzed. The results demonstrate the ubiquitous presence of APs and BPA in urban materials and their extractable character with water. The compounds with the strongest emission rates were bisphenol A and nonylphenol. The most important BPA emissions into water (10 to 300 ng/g) were measured for polycarbonate, tires, some car bodies, and PVC. Nonylphenol was leached in large quantities (1 to 10 ng/g) from PVC, some concretes, SBS-modified bitumen, and body samples. The tires were the only materials having a strong emission in octylphenol (1 to 10 ng/g). The analysis of automotive fluids confirmed the presence of BPA (0.3 to 5.5 g/L) and nonylphenol (2.3 to 2.9 mg/L) in brake fluids, while APs and BPA were found at trace levels in coolants and windscreen washer. Graphical abstract ᅟ.

Impacts from urban water systems on receiving waters - How to account for severe wet-weather events in LCA?

Sewage systems are a vital part of the urban infrastructure in most cities. They provide drainage, which protects public health, prevents the flooding of property and protects the water environment around urban areas. On some occasions sewers will overflow into the water environment during heavy rain potentially causing unacceptable impacts from releases of untreated sewage into the environment. In typical Life Cycle Assessment (LCA) studies of urban wastewater systems (UWS), average dry-weather conditions are modelled while wet-weather flows from UWS, presenting a high temporal variability, are not currently accounted for. In this context, the loads from several storm events could be important contributors to the impact categories freshwater eutrophication and ecotoxicity. In this study we investigated the contributions of these wet-weather-induced discharges relative to average dry-weather conditions in the life cycle inventory for UWS. In collaboration with the Paris public sanitation service (SIAAP) and Observatory of Urban Pollutants (OPUR) program researchers, this work aimed at identifying and comparing contributing flows from the UWS in the Paris area by a selection of routine wastewater parameters and priority pollutants. This collected data is organized according to archetypal weather days during a reference year. Then, for each archetypal weather day and its associated flows to the receiving river waters (Seine), the parameters of pollutant loads (statistical distribution of concentrations and volumes) were determined. The resulting inventory flows (i.e. the potential loads from the UWS) were used as LCA input data to assess the associated impacts. This allowed investigating the relative importance of episodic wet-weather versus "continuous" dry-weather loads with a probabilistic approach to account for pollutant variability within the urban flows. The analysis at the scale of one year showed that storm events are significant contributors to the impacts of freshwater eutrophication and ecotoxicity compared to those arising from treated effluents. At the rain event scale the wet-weather contributions to these impacts are even more significant, accounting for example for up to 62% of the total impact on freshwater ecotoxicity. This also allowed investigating and discussing the ecotoxicity contribution of each class of pollutants among the broad range of inventoried substances. Finally, with such significant contributions of pollutant loads and associated impacts from wet-weather events, further research is required to better include temporally-differentiated emissions when evaluating eutrophication and ecotoxicity. This will provide a better understanding of how the performance of an UWS system affects the receiving environment for given local weather conditions.

Zirconium deficit as a tracer of urban sediment accumulation in Sustainable Urban Drainage Systems - Application to the calibration of a filtration model.

Among the processes governing contaminant retention in soil-based Sustainable Urban Drainage Systems (SUDS), quantifying the relative contribution of particle settling and filtration requires a tracer of runoff-generated solids. Since zirconium (Zr) is a widely used geochemical invariant in pedological approaches, with few anthropogenic sources, the present investigation aims to assess whether its use may be extended to sediment identification in SUDS. High-resolution horizontal and vertical soil sampling was carried out in 11 infiltration systems, as well as in road-deposited sediment. Following elemental analysis via X-ray fluorescence spectrometry, the spatial distribution of both Zr and urban-derived metals could be determined. Zr content in sediment was found to be fairly stable and significantly lower than in soil. In most devices, Zr and metals exhibited "mirror" trends, both horizontally and vertically, i.e. a deficit of Zr could be observed in the most contaminated area. This indicated a "dilution-like" mixture of soil and sediment, the fraction of which could be calculated and appraised spatially. The vertical profiles proved the occurrence of bed filtration over 5 to 15 cm, and enabled the calibration of a simple filtration model. The uncertainties associated with the determined filter coefficient were found to be comparable to the other experimental methods - with the additional improvement that the present approach does not require water sampling.

Stochastic evaluation of annual micropollutant loads and their uncertainties in separate storm sewers.

This article describes a stochastic method to calculate the annual pollutant loads and its application over several years at the outlet of three catchments drained by separate storm sewers. A stochastic methodology using Monte Carlo simulations is proposed for assessing annual pollutant load, as well as the associated uncertainties, from a few event sampling campaigns and/or continuous turbidity measurements (representative of the total suspended solids concentration (TSS)). Indeed, in the latter case, the proposed method takes into account the correlation between pollutants and TSS. The developed method was applied to data acquired within the French research project "INOGEV" (innovations for a sustainable management of urban water) at the outlet of three urban catchments drained by separate storm sewers. Ten or so event sampling campaigns for a large range of pollutants (46 pollutants and 2 conventional water quality parameters: TSS and total organic carbon (TOC)) are combined with hundreds of rainfall events for which, at least one among three continuously monitored parameters (rainfall intensity, flow rate, and turbidity) is available. Results obtained for the three catchments show that the annual pollutant loads can be estimated with uncertainties ranging from 10 to 60%, and the added value of turbidity monitoring for lowering the uncertainty is demonstrated. A low inter-annual and inter-site variability of pollutant loads, for many of studied pollutants, is observed with respect to the estimated uncertainties, and can be explained mainly by annual precipitation.

Assessment of metal and PAH profiles in SUDS soil based on an improved experimental procedure.

The increasing use of infiltration-based systems for stormwater management questions the soil's ability to act as a long-term filter for runoff contaminants, and brings about operational matters regarding the most effective maintenance practices to enhance contaminant retention in SUDS. This paper reports the vertical extent of metal and PAH contamination in the soil of seven source-control devices in operation for more than 10 years, assessed via a two-step sampling strategy to optimize the representativeness of the contamination profiles. Metal distribution was typically characterized by a significant surface buildup, followed by a decrease in concentrations with increasing depth, usually coming close to the background values. PAH were more heterogeneously distributed with depth, but their accumulation was globally restricted to the upper 10-40 cm. This indicates an interesting potential for pollution interception by the upper horizons of soil, but does not necessarily prevent from downward fluxes, even while measuring low surface contents, as deeper strata may have lesser retention capacities. Specific amendments of the surface soil may help prevent this problem. Surface soil renewal - which would be necessary over 2.5-30 cm in four sites, according to the "strictest" standards for soil remediation - may regenerate the soil's sorption potential, but such a practice could disrupt the interactions with the local ecosystem, so this should be carried out exceptionally and not as a preventive measure.

Evaluation of the relative roles of a vegetative filter strip and a biofiltration swale in a treatment train for road runoff.

In order to determine the relative importance of a vegetative filter strip and a biofiltration swale in a treatment train for road runoff, US EPA Storm Water Management Model was used to model infiltration and runoff from the filter strip. The model consisted of a series of subcatchments representing the road, the filter strip and the side-slopes of the swale. Simulations were carried out for different rain scenarios representing a variety of climatic conditions. In addition, a sensitivity analysis was conducted for the model's different parameters (soil characteristics and initial humidity, roughness, geometry, etc.). This exercise showed that for the system studied, the majority of road runoff is treated by the filter strip rather than the biofiltration swale, an effect observed especially during periods of low-intensity rainfall. Additionally, it was observed that the combination of infiltration of road runoff in the filter strip and direct rainfall on the system leads to a significant and variable dilution of the runoff reaching the swale. This result has important implications for evaluating the treatment efficiency of the system.

Spatial distribution of heavy metals in the surface soil of source-control stormwater infiltration devices - Inter-site comparison.

Stormwater runoff infiltration brings about some concerns regarding its potential impact on both soil and groundwater quality; besides, the fate of contaminants in source-control devices somewhat suffers from a lack of documentation. The present study was dedicated to assessing the spatial distribution of three heavy metals (copper, lead, zinc) in the surface soil of ten small-scale infiltration facilities, along with several physical parameters (soil moisture, volatile matter, variable thickness of the upper horizon). High-resolution samplings and in-situ measurements were undertaken, followed by X-ray fluorescence analyses and spatial interpolation. Highest metal accumulation was found in a relatively narrow area near the water inflow zone, from which concentrations markedly decreased with increasing distance. Maximum enrichment ratios amounted to >20 in the most contaminated sites. Heavy metal patterns give a time-integrated vision of the non-uniform infiltration fluxes, sedimentation processes and surface flow pathways within the devices. This element indicates that the lateral extent of contamination is mainly controlled by hydraulics. The evidenced spatial structure of soil concentrations restricts the area where remediation measures would be necessary in these systems, and suggests possible optimization of their hydraulic functioning towards an easier maintenance. Heterogeneous upper boundary conditions should be taken into account when studying the fate of micropollutants in infiltration facilities with either mathematical modeling or soil coring field surveys.

Impact of runoff infiltration on contaminant accumulation and transport in the soil/filter media of Sustainable Urban Drainage Systems: A literature review.

The increasing use of Sustainable Urban Drainage Systems (SUDS) for stormwater management raises some concerns about the fate of ubiquitous runoff micropollutants in soils and their potential threat to groundwater. This question may be addressed either experimentally, by sampling and analyzing SUDS soil after a given operating time, or with a modeling approach to simulate the fate and transport of contaminants. After briefly reminding the processes responsible for the retention, degradation, or leaching of several urban-sourced contaminants in soils, this paper presents the state of the art about both experimental and modeling assessments. In spite of noteworthy differences in the sampling protocols, the soil parameters chosen as explanatory variables, and the methods used to evaluate the site-specific initial concentrations, most investigations undoubtedly evidenced a significant accumulation of metals and/or hydrocarbons in SUDS soils, which in the majority of the cases appears to be restricted to the upper 10 to 30cm. These results may suggest that SUDS exhibit an interesting potential for pollution control, but antinomic observations have also been made in several specific cases, and the inter-site concentration variability is still difficult to appraise. There seems to be no consensus regarding the level of complexity to be used in models. However, the available data deriving from experimental studies is generally limited to the contamination profiles and a few parameters of the soil, as a result of which "complex" models (including colloid-facilitated transport for example) appear to be difficult to validate before using them for predictive evaluations.

Modeling the temporal variability of zinc concentrations in zinc roof runoff-experimental study and uncertainty analysis.

This study investigates the temporal variability of zinc concentrations from zinc roof runoff. The influence of rainfall characteristics and dry period duration is evaluated by combining laboratory experiment on small zinc sheets and in situ measurements under real weather conditions from a 1.6-m(2) zinc panel. A reformulation of a commonly used conceptual runoff quality model is introduced and its ability to simulate the evolution of zinc concentrations is evaluated. A systematic and sharp decrease from initially high to relatively low and stable zinc concentrations after 0.5 to 2 mm of rainfall is observed for both experiments, suggesting that highly soluble corrosion products are removed at early stages of runoff. A moderate dependence between antecedent dry period duration and the magnitude of zinc concentrations at the beginning of a rain event is evidenced. Contrariwise, results indicate that concentrations are not significantly influenced by rainfall intensities. Simulated rainfall experiment nonetheless suggests that a slight effect of rainfall intensities may be expected after the initial decrease of concentrations. Finally, this study shows that relatively simple conceptual runoff quality models may be adopted to simulate the variability of zinc concentrations during a rain event and from a rain event to another.

Performance assessment of a commonly used "accumulation and wash-off" model from long-term continuous road runoff turbidity measurements.

The suitability of a commonly used accumulation and wash-off model for continuous modelling of urban runoff contamination was evaluated based on 11-month turbidity and flow-rate records from an urban street. Calibration and uncertainty analysis were performed using a Markov Chain Monte-Carlo sampling method for both suspended solids loads (discharge rates) and concentration modelling. Selected models failed at replicating suspended solids concentration over the complete monitoring period. The studied dataset indeed suggests that the accumulation process is rather unpredictable and cannot be satisfactorily represented with usual accumulation models unless short periods are considered. Regarding suspended solid loads modelling, noticeably better performance was achieved, but similar results could as well be obtained with much simpler constant concentration models. Unless providing very accurate estimates of concentrations in runoff, accounting for their temporal variability during rain events may therefore not always be necessary for pollutant loads modelling, as loads are in fact mostly explained by runoff volumes.

Stormwater management criteria for on-site pollution control: a comparative assessment of international practices.

Over the last decade, a growing interest has been shown toward innovative stormwater management practices, breaking away from conventional "end of pipe" approaches (based on conveying water offsite to centralized detention facilities). Innovative strategies, referred to as sustainable urban drainage systems, low impact development (LID) or green infrastructures, advocating for management of runoff as close to its origin as possible, have therefore gained a lot of popularity among practitioners and public authorities. However, while the need for pollution control is generally well accepted, there is no wide agreement about management criteria to be given to developers. This article hence aims to compare these criteria through literature analysis of different state or local stormwater management manuals or guidelines, investigating both their suitability for pollution control and their influence on best management practices selection and design. Four categories of criteria were identified: flow-rate limitations, "water quality volumes" (to be treated), volume reduction (through infiltration or evapotranspiration), and non-hydrologic criteria (such as loads reduction targets or maximum effluent concentrations). This study suggests that hydrologic criteria based on volume reduction (rather than treatment) might generally be preferable for on-site control of diffuse stormwater pollution. Nonetheless, determination of an appropriate management approach for a specific site is generally not straightforward and presents a variety of challenges for site designers seeking to satisfy local requirements in addressing stormwater quantity and quality issues. The adoption of efficient LID solution may therefore strongly depend on the guidance given to practitioners to account for these management criteria.

Efficiency of source control systems for reducing runoff pollutant loads: feedback on experimental catchments within Paris conurbation.

Three catchments, equipped with sustainable urban drainage systems (SUDS: vegetated roof, underground pipeline or tank, swale, grassed detention pond) for peak flow mitigation, have been compared to a reference catchment drained by a conventional separate sewer system in terms of hydraulic behaviour and discharged contaminant fluxes (organic matter, organic micropollutants, metals). A runoff and contaminant emission model has been developed in order to overcome land use differences. It has been demonstrated that the presence of peak flow control systems induces flow attenuation even for frequent rain events and reduces water discharges at a rate of about 50% depending on the site characteristics. This research has also demonstrated that this type of SUDS contributes to a significant reduction of runoff pollutant discharges, by 20%-80%. This level of reduction varies depending on the considered contaminant and on the design of the drainage system but is mostly correlated with the decrease in runoff volume. It could be improved if the design of these SUDS focused not only on the control of exceptional events but also targeted more explicitly the interception of frequent rain events.

Nonpoint source pollution of urban stormwater runoff: a methodology for source analysis.

The characterization and control of runoff pollution from nonpoint sources in urban areas are a major issue for the protection of aquatic environments. We propose a methodology to quantify the sources of pollutants in an urban catchment and to analyze the associated uncertainties. After describing the methodology, we illustrate it through an application to the sources of Cu, Pb, Zn, and polycyclic aromatic hydrocarbons (PAH) from a residential catchment (228 ha) in the Paris region. In this application, we suggest several procedures that can be applied for the analysis of other pollutants in different catchments, including an estimation of the total extent of roof accessories (gutters and downspouts, watertight joints and valleys) in a catchment. These accessories result as the major source of Pb and as an important source of Zn in the example catchment, while activity-related sources (traffic, heating) are dominant for Cu (brake pad wear) and PAH (tire wear, atmospheric deposition).

A new method for modelling roofing materials emissions on the city scale: application for zinc in the City of Créteil (France).

Today, urban runoff is considered as an important source of environmental pollution. Roofing materials, in particular, the metallic ones, are considered as a major source of urban runoff metal contaminations. In the context of the European Water Directive (2000/60 CE), an accurate evaluation of contaminant flows from roofs is thus required on the city scale, and therefore the development of assessment tools is needed. However, on this scale, there is an important diversity of roofing materials. In addition, given the size of a city, a complete census of the materials of the different roofing elements represents a difficult task. Information relating roofing materials and their surfaces on an urban district do not currently exist in urban databases. The objective of this paper is to develop a new method of evaluating annual contaminant flow emissions from the different roofing material elements (e.g., gutter, rooftop) on the city scale. This method is based on using and adapting existing urban databases combined with a statistical approach. Different rules for identifying the materials of the different roofing elements on the city scale have been defined. The methodology is explained through its application to the evaluation of zinc emissions on the scale of the city of Créteil.