In-situ estimation of non-regulated pollutant emission factors in an urban area of Nantes, France, with fleet composition characterization

The purpose of this study is to estimate the in-situ emission factors of several pollutants (particle number [PN], black carbon [BC] and several volatile and semi-volatile organic compounds [VOCs and SVOCs]) in an urban area of Nantes, France, with real-world traffic conditions and characterization of the fleet composition. The fleet composition and driving conditions are characterized by the number of vehicles, their speeds and their types (passenger cars [PCs], light commercial vehicles [LCVs], heavy-duty vehicles [HDVs]) as well as their characteristics (make, model, fuel, engine, EURO emission standard, etc.). The number of vehicles passing on the boulevard is around 20,000 per day with about 44% of Euro 5 and Euro 6 vehicles. The impacts of fleet composition on emission were analyzed by ANOVA. The results show that the fleet composition has a significant impact on emissions for different pollutants. Higher percentage of gasoline PCs between Euro 4 to Euro 6 and Euro 4 diesel PCs induces more BC emission. Higher percentage of old gasoline and diesel vehicles (? Euro 3) induces higher emission of toluene, ethylbenzene and m+p- and o-xylene. Furthermore, emission factors estimated in this work were compared to those calculated in other in-situ studies that show a good agreement. For the chassis bench comparison, the in-situ PN and BC emission factors are in the same range as those measured for diesel vehicles without particle filter and gasoline vehicles with direct injection system. These EFs are also comparable with old heavy duty vehicles without particle filter (5x1013-2x1014 #/km)

Une plateforme pour l'analyse de matériaux par faisceaux d'ions à ARRONAX : Etude de l'effet d'humidité sur les échantillons

International audienceQuantification of soil pollution with method based on X-ray detection like X-Ray Fluorescence(XRF) suffers of multiple bias (moisture, surface state) especially when it's used for insituanalysis using portable-XRF. In order to study the effect of moisture on the results of ananalysis performed using X-Ray, we have performed studies using high energy PIXE/PIGE atthe ARRONAX. Samples were made of sand of different type. High energy PIXE/PIGE allowsus to avoid bias from surface state and to focus on moisture effect. It also allows to assessthe chemical composition of the sample. Results show a different behavior for each elementpresent in volcanic sand.</p

Food production and resource use of urban farms and gardens: a five-country study

There is a lack of data on resources used and food produced at urban farms. This hampers attempts to quantify the environmental impacts of urban agriculture or craft policies for sustainable food production in cities. To address this gap, we used a citizen science approach to collect data from 72 urban agriculture sites, representing three types of spaces (urban farms, collective gardens, individual gardens), in five countries (France, Germany, Poland, United Kingdom, and United States). We answered three key questions about urban agriculture with this unprecedented dataset: (1) What are its land, water, nutrient, and energy demands? (2) How productive is it relative to conventional agriculture and across types of farms? and (3) What are its contributions to local biodiversity? We found that participant farms used dozens of inputs, most of which were organic (e.g., manure for fertilizers). Farms required on average 71.6 L of irrigation water, 5.5 L of compost, and 0.53 m2 of land per kilogram of harvested food. Irrigation was lower in individual gardens and higher in sites using drip irrigation. While extremely variable, yields at well-managed urban farms can exceed those of conventional counterparts. Although farm type did not predict yield, our cluster analysis demonstrated that individually managed leisure gardens had lower yields than other farms and gardens. Farms in our sample contributed significantly to local biodiversity, with an average of 20 different crops per farm not including ornamental plants. Aside from clarifying important trends in resource use at urban farms using a robust and open dataset, this study also raises numerous questions about how crop selection and growing practices influence the environmental impacts of growing food in cities. We conclude with a research agenda to tackle these and other pressing questions on resource use at urban farms

Column leaching of chromium and nickel from a contaminated soil using EDTA and citric acid

International audienceThis study investigates the column leaching of a soil contaminated mainly with Cr and Ni by using two chelants: citric acid (biodegradable) and EDTA (non-biodegradable) followed with water rinse. The chelants lead to Cr and Ni leaching, in addition to major elements (Ca, Fe, Mg, Al, Mn and Zn) showing the dissolution of soil mineral constituents. EDTA leaches more major elements and Ni than citric acid related to the respective stability of metal/chelant complexes; citric acid leaches more Cr than EDTA, certainly because of a substitution reaction with Cr(VI). In the case of alternating chelant/water applications, leaching occurs during the chelant applications, but also during water applications. In the case of chelant/water applications followed by continuous water application, both Cr and Ni leach over time. This increased mobility could be due to the residual chelant present in soil as well as to the dissolution/ mobilization of mineral or organic soil fractions

Influence de l’historique d’usage des sols : les jardins de Nantes

International audienc

Pollutant characteristics and size distribution of trace elements during stormwater runoff events

Priority trace elements As, Cu, Cr, Ni, Pb, and Zn are largely present in urban stormwaters and should be controlled due to their impact on water bodies. As it has been observed that there are numerous limitations in the purification performance of roadway stormwater runoff treatment systems, the particulate size distribution of trace elements was studied extensively to assess the colloidal fractions present in stormwater runoff of a high-traffic roadway site (100 000 vehicles/day). Besides the evaluation of the total Event Mean Concentrations (EMCs) and dissolved concentrations, a complete fractionation scheme of low settling phase of runoff water (<30 µm) was applied to a series of rain events, considering 8 µm and 5 kDa, as relevant cut-offs between particulate/colloidal elements, and colloidal/truly dissolved elements. The intra-event size distribution was also considered to assess the first-flush effect and the variation of the physical speciation. The high-level traffic associated with climatic conditions (rainfall depth) are responsible for very high EMCs for Zn and Cu, together with a significant exceedance of the European environmental water standards (<0.45 µm concentrations). Ni, Cr and Pb are mainly present as particulate and colloidal metals. Therefore, considering a more complete size distribution is relevant for these elements. For As, Cu and Zn, the conventional fractionation at 0.45 µm seems to be sufficient to evaluate the highly mobile fraction. The results also indicate that, while the main particulate load may be collected within the early volumes of the rainfall events (about 30%), the variability of rain intensity during long events induces changes in particulate and colloidal metals in the runoff. The treatment of runoff must then be considered as a whole in view of the variability of trace metal size distribution. This suggests that urban stormwater runoff treatment systems which employ only the settleable fraction are not sufficient to limit the chemical and ecological risks to receiving water bodies

Variabilité temporelle de la spéciation physique des éléments trace dans les eaux de ruissellement au cours des événements pluvieux

International audienceThe particulate size distribution of trace elements was studied to assess the colloidal form presence in stormwater runoff of a high-traffic roadway site (100 000 vehicle/day). A complete fractionation scheme was applied to a series of rain events, considering 8 µm and 5 kDa as relevant cut-offs between particulate/colloidal elements and colloidal/truly dissolved elements. The intra-event size distribution was also considered to assess the first-flush effect and the variation of the physical speciation. Ni, Cr and Pb are mainly present as particulate and colloidal metals. Therefore, considering a complete size distribution is relevant for these elements. For As, Cu and Zn, the conventional fractionation at 0.45 µm seems to be sufficient to evaluate the highly mobile fraction. Moreover, the results indicate that the variability of rain intensity during long events induces changes in particulate and colloidal metals in the runoff. The treatment of runoff must then be considered as a whole in view of the variability of trace metal size distribution. This suggests that urban stormwater runoff treatment based only on the removal of settleable fraction is not sufficient to limit the chemical and ecological risks to receiving water bodies.La spéciation physique des éléments trace a été étudiée afin d’évaluer leur présence sous forme colloïdale dans les eaux de ruissellement d'un site routier à fort trafic (100 000 véhicules/jour). Un schéma de fractionnement complet a été appliqué à une série d'événements pluvieux, en considérant 8 µm et 5 kDa comme des seuils pertinents entre forme particulaire - forme colloïdale et forme colloïdale - forme dissoute. La distribution intra-événement a également été prise en compte pour évaluer l'effet "first-flush" ainsi que la variation de la spéciation physique. Ni, Cr et Pb sont présents principalement sous forme particulaire et colloïdale. Il est donc pertinent de considérer une distribution en taille fine pour ces éléments. Pour As, Cu et Zn, la filtration conventionnelle à 0,45 µm semble être suffisante pour évaluer la fraction mobile. Par ailleurs, les résultats indiquent que la variabilité de l'intensité des pluies lors d'événements longs induit des changements de distribution entre forme particulaire et forme colloïdale des éléments trace dans les eaux de ruissellement. Le traitement du ruissellement doit alors être considéré dans son ensemble compte tenu de la variabilité de la distribution des éléments trace. Ceci suggère que le dimensionnement des ouvrages de gestion des eaux de ruissellement basé sur la fraction décantable devrait être revu pour limiter les risques chimiques et écologiques pour les masses d'eau réceptrices

Platinum group elements in atmospheric PM10 particles and dry deposition in France

Platinum group elements (PGEs, i.e. platinum, Pt; palladium, Pd; and rhodium, Rh) catalyse over 90% of carbon monoxide, nitrogen oxides and hydrocarbons from combustion residues into water vapour, carbon dioxide and nitrogen in the vehicle&apos;s catalytic converter. But there is a major concern over these metals in the scientific world, since they are emitted by catalytic converters and accumulating in the environment. The distribution of PGEs in PM10 fraction was studied in an open urban site (Nantes, France) and in a tunnel (Paris, France) using low- and high-volume air samplers. PGEs were also investigated in dry deposition particles and deposited dust sampled in the tunnel. Pd occurred at the highest levels in both PM10 and dry deposition samples, followed by Rh and Pt. Maximum concentrations in PM10 fraction were 114 pg m-3 for Pd, 14.3 pg m-3 for Rh and 3.3 pg m-3 for Pt in the urban site (Nantes) and 91 pg m-3 for Pd and 16 pg m-3 for Rh in the tunnel (Paris). The concentrations for dry depositions in the tunnel were 261 ug kg-1 for Pt, 431 ug kg-1 for Pd and 85 ug kg-1 for Rh. The results on PGEs levels in atmospheric particles and dry depositions are the first data of their kind in France and will provide new insights into the contribution of catalytic converters to the environment. We also observed Pd and Rh being 2 times higher PM10 particles compared to dry depositions, leading us to suggest that particles rich in Pd and Rh are smaller than 10 um. An overall concentration trend of Pd &gt; Rh &gt; Pt was observed in all samples, showing the replacement of Pt by Pd and Rh in newer catalytic converters

La mémoire des sols : rôle des usages historiques sur la contamination par des éléments traces - exemples de jardins associatifs (Nantes, France)

International audienceUrban gardening practices are exploding around the world, especially in industrialized countries. The question of soil contamination nevertheless arises, insofar as the soil memorizes the impacts linked to various successive human activities. Urban soils are therefore likely to have high concentrations of contaminants, particularly trace elements. Research on the link between contaminants distribution and different types of land use appears to be limited. In this context, this paper aims to illustrate how former land use influences the current spatial distribution of trace element in urban soils, based on the example of urban allotment gardens located in Nantes (France).The 8 gardens studied are part of a large urban allotment garden (UAG) program in Nantes (France). Land use changes were determined using a historical analysis of the human activities for each site. Trace elements measurements in topsoils and soil profiles were carried out using a portable X-Ray fluorescence spectrometer, with additional laboratory analyses to calibrate the results. The origin of trace elements and their spatial distribution in soils were interpreted in light of land-use changes. Successive human activities such as industry, backfilling, agricultural crops… appear as key factors of the distribution of trace element in soils. However, it is not always sufficient to understand the source of trace elements. Therefore, it is essential to characterize soil geochemistry in the context of soil management and urban redevelopment to ensure that soil quality is compatible with current and further land use