Thierry Winiarski

Retention and distribution of three heavy metals in a carbonated soil: comparison between batch and unsaturated column studies

Abstract The uptake of 5×10 −4 mol/l solutions of Cd, Pb and Zn by a fluvio glacial deposit with high carbonate content (227 mg/g) was studied in column and batch experiments. The heavy metals were added to soil samples and the retention examined using a speciation scheme with five fractions: exchangeable, acid-soluble, reducible, oxidizable and residual. In batch experiments, the three metal ions were completely bound by the soil, mostly to the acid-soluble fraction: 62% for Cd, 96% Pb and 86% Zn. The exchangeable fraction was of minor importance, with 27% Cd, 4% Pb and 11% Zn. The thermodynamic data suggested that lead and cadmium were mainly associated with carbonate ions while the zinc was found in two forms, zinc hydroxide and zinc carbonate. The influence of initial metal concentration was examined for Cd; an increase in metal concentration led weaker retention. The column experiments showed progressive saturation of the soil, with lead being retained better than cadmium or zinc. The measured retentions of all three metals were lower for columns than in batches. This difference was not explainable by thermodynamic data or by reaction kinetics alone. We believe it is mainly due to preferential flows in column experiments, favouring metal ion elution.

Temporal evolution of urban wet weather pollution: analysis of PCB and PAH in sediment cores from Lake Bourget, France

In order to evaluate the historical impact of urban stormwater runoff on a lacustrine environment, eight sediment cores were collected in October 2006 in Lake Bourget (Savoie, France). Sediment samples were analysed for polycyclic aromatic hydrocarbons (PAH) and polychlorobyphenyls (PCB) in order to correlate the vertical profiles of contamination and the evolution of the urbanisation on the watershed for the last 100 years. Overall, we observe that vertical profiles of PCB and PAH concentrations in Lake Bourget are showing a downward trend, probably resulting from the pollution control measures. Concentrations of PCB and PAH measured in surface sediments are approximately 5-10 fold less than maximal concentrations found in the cores. Maximal PAH concentrations were found at the bottom of the cores ( approximately 40 cm) which approximately correspond to the beginning of the 20th century. Maximal PCB concentrations measured in cores L5 and L6 are respectively 850 and 790 microg/g dw (dryweight). The peak of PCB corresponds to the maximum of PCB production and consumption in the 1970s. In surface sediments total PCB concentrations range between 47 and 79 microg/kg dw. Those concentrations are particularly high compared to other values measured in lake sediments and highlight the problem of a local source of PCB contamination in the watershed. General trends were observed, yet the part of urban stormwater runoff in the total contamination could not be determined.

Assessing the Mobility of Lead, Copper and Cadmium in a Calcareous Soil of Port-au-Prince, Haiti

The presence of heavy metals in the environment constitutes a potential source of both soil and groundwater pollution. This study has focused on the reactivity of lead (Pb), copper (Cu) and Cadmium (Cd) during their transfer in a calcareous soil of Port-au-Prince (Haiti). Kinetic, monometal and competitive batch tests were carried out at pH 6.0. Two simplified models including pseudo-first-order and pseudo-second-order were used to fit the experimental data from kinetics adsorption batch tests. A good fit of these data was found with pseudo-second-order kinetic model which indicates the applicability of this model to describe the adsorption rates of these metals on the soil. Monometal batch tests indicated that both Langmuir and Freundlich models allowed a good fit for experimental data. On the basis of the maximum adsorption capacity (qmax), the order affinity of Pb, Cu and Cd for the studied soil was Pb2+ > Cu2+ > Cd2+. Competitive sorption has proved that the competition between two or several cations on soils for the same active sites can decrease their qmax. These results show that, at high metal concentrations, Cd may pose more threat in soils and groundwater of Port-au-Prince than Pb and Cu.

Combined effect of capillary barrier and layered slope on water, solute and nanoparticle transfer in an unsaturated soil at lysimeter scale

It is well recognized that colloidal nanoparticles are highly mobile in soils and can facilitate the transport of contaminants through the vadose zone. This work presents the combined effect of the capillary barrier and soil layer slope on the transport of water, bromide and nanoparticles through an unsaturated soil. Experiments were performed in a lysimeter (1×1×1.6m(3)) called LUGH (Lysimeter for Urban Groundwater Hydrology). The LUGH has 15 outputs that identify the temporal and spatial evolution of water flow, solute flux and nanoparticles in relation to the soil surface conditions and the 3D system configuration. Two different soil structures were set up in the lysimeter. The first structure comprises a layer of sand (0-0.2cm, in diameter) 35cm thick placed horizontally above a layer of bimodal mixture also 35cm thick to create a capillary barrier at the interface between the sand and bimodal material. The bimodal material is composed of a mixture 50% by weight of sand and gravel (0.4-1.1cm, in diameter). The second structure, using the same amount of sand and bimodal mixture as the first structure represents an interface with a 25% slope. A 3D numerical model based on Richards equation for flow and the convection dispersion equations coupled with a mechanical module for nanoparticle trapping was developed. The results showed that under the effect of the capillary barrier, water accumulated at the interface of the two materials. The sloped structure deflects flow in contrast to the structure with zero slope. Approximately 80% of nanoparticles are retained in the lysimeter, with a greater retention at the interface of two materials. Finally, the model makes a good reproduction of physical mechanisms observed and appears to be a useful tool for identifying key processes leading to a better understanding of the effect of capillary barrier on nanoparticle transfer in an unsaturated heterogeneous soil.

Deterministic modeling of the impact of underground structures on urban groundwater temperature

Underground structures have a major influence on groundwater temperature and have a major contribution on the anthropogenic heat fluxes into urban aquifers. Groundwater temperature is crucial for resource management as it can provide operational sustainability indicators for groundwater quality and geothermal energy. Here, a three dimensional heat transport modeling approach was conducted to quantify the thermally affected zone (TAZ, i.e. increase in temperature of more than +0.5°C) caused by two common underground structures: (1) an impervious structure and (2) a draining structure. These design techniques consist in (1) ballasting the underground structure in order to resist hydrostatic pressure, or (2) draining the groundwater under the structure in order to remove the hydrostatic pressure. The volume of the TAZ caused by these underground structures was shown to range from 14 to 20 times the volume of the underground structure. Additionally, the cumulative impact of underground structures was assessed under average thermal conditions at the scale of the greater Lyon area (France). The heat island effect caused by underground structures was highlighted in the business center of the city. Increase in temperature of more than +4.5°C were locally put in evidence. The annual heat flow from underground structures to the urban aquifer was computed deterministically and represents 4.5GW·h. Considering these impacts, the TAZ of deep underground structures should be taken into account in the geothermal potential mapping. Finally, the amount of heat energy provided should be used as an indicator of heating potential in these areas.

A 300 year history of lead contamination in northern French Alps reconstructed from distant lake sediment recordsPresented as part of the Archives of Environmental Contamination at the 6th International Symposium on Environmental Geochemistry, Edinburgh, Scotland, 7?11 September 2003.

Lead concentrations and isotopic ratios were measured along two well-dated sediment cores from two distant lakes: Anterne (2100 m a.s.l.) and Le Bourget (270 m a.s.l.), submitted to low and high direct human impact and covering the last 250 and 600 years, respectively. The measurement of lead in old sediment samples (>3000 BP) permits, in using mixing-models, the determination of lead concentration, flux and isotopic composition of purely anthropogenic origin. We thus show that since ca. 1800 AD the regional increase in lead contamination was mostly driven by coal consumption ((206)Pb/(207)Pb approximately 1.17-1.19; (206)Pb/(204)Pb approximately 18.3-18.6), which peaks around 1915 AD. The increasing usage of leaded gasoline, introduced in the 1920s, was recorded in both lakes by increasing Pb concentrations and decreasing Pb isotope ratios. A peak around 1970 ((206)Pb/(207)Pb approximately 1.13-1.16; (206)Pb/(204)Pb approximately 17.6-18.0) corresponds to the worldwide recorded leaded gasoline maximum of consumption. The 1973 oil crisis is characterised by a drastic drop of lead fluxes in both lakes (from approximately 35 to <20 mg cm(-2) yr(-1)). In the late 1980s, environmental policies made the Lake Anterne flux drop to pre-1900 values (<10 mg cm(-2) yr(-1)) while Lake Le Bourget is always submitted to an important flux (approximately 25 mg cm(-2) yr(-1)). The good match of our distant records, together and with a previously established series in an ice core from Mont Blanc, provides confidence in the use of sediments as archives of lead contamination. The integration of the Mont Blanc ice core results from Rosman et al. with our data highlights, from 1990 onward, a decoupling in lead sources between the high elevation sites (Lake Anterne and Mont Blanc ice core), submitted to a mixture of long-distance and regional contamination and the low elevation site (Lake Le Bourget), where regional contamination is predominant.

Analysis of the spatial and temporal variations in the water quality of a karstic aquifer using UV spectrophotometry

This article presents a simple method based on the examination of ultraviolet multiwavelength absorptiometry of groundwater samples collected from a karstic aquifer, for direct and fast quality evaluation. The method provides information about the flow conditions of a karstic system, it helps with the monitoring of groundwater sampling during the pumping procedure and, finally, it gives an insight into the complexity of the spatial and temporal evolutions of the system. Application of this method to the study of a karstic experimental field situated in the south of France is subsequently presented. UV spectrophotometry used during investigations shows the hydraulic relation between two piezometers, and also between a piezometer and a surface watercourse. It stresses the influence of surface hydrology on water quality of this karstic aquifer. During periods of high flow, the water quality is the same in all the piezometers and is linked to the leaching of nitrates present in the upper surrounds of the aquifer; during mean or low flow, each piezometer presents a particular water quality depending on its local transmissivity.

Ecotoxicological characterisation of sediments from stormwater retention basins

Retention-detention basins are important structures for managing stormwater. However, their long-term operation raises the problem of managing the sediments they accumulate. Potential uses for such sediments have been envisaged, but each sediment must be characterised beforehand to verify its harmlessness. In this paper we address this issue through the development of a battery of bioassays specifically adapted to such sediments. We tested the method on samples taken from four retention basins in the region of Lyon (France). This battery focuses on the toxic effects linked to both the solid phase (ostracod and Microtox(®) solid-phase tests) and the liquid-phase (interstitial water) of sediments (rotifer and Microtox(®) liquid-phase tests). The results obtained permit the sorting of sediments presenting little toxicity, and which could therefore be potentially exploitable, from those from more polluted areas presenting higher toxicity that limits their use.

Deterministic modelling of the cumulative impacts of underground structures on urban groundwater flow and the definition of a potential state of urban groundwater flow: example of Lyon, France

Underground structures have been shown to have a great influence on subsoil resources in urban aquifers. A methodology to assess the actual and the potential state of the groundwater flow in an urban area is proposed. The study develops a three-dimensional modeling approach to understand the cumulative impacts of underground infrastructures on urban groundwater flow, using a case in the city of Lyon (France). All known underground structures were integrated in the numerical model. Several simulations were run: the actual state of groundwater flow, the potential state of groundwater flow (without underground structures), an intermediate state (without impervious structures), and a transient simulation of the actual state of groundwater flow. The results show that underground structures fragment groundwater flow systems leading to a modification of the aquifer regime. For the case studied, the flow systems are shown to be stable over time with a transient simulation. Structures with drainage systems are shown to have a major impact on flow systems. The barrier effect of impervious structures was negligible because of the small hydraulic gradient of the area. The study demonstrates that the definition of a potential urban groundwater flow and the depiction of urban flow systems, which involves understanding the impact of underground structures, are important issues with respect to urban underground planning.RésuméLes structures souterraines ont montré avoir une grande influence sur les ressources du sous-sol dans les aquifères urbains. Une méthodologie d’évaluation de l’état actuel et potentiel de l’écoulement des eaux souterraines dans une zone urbaine est proposée. L’étude développe une approche de modélisation en trois dimensions pour comprendre les impacts cumulés des infrastructures souterraines sur les écoulements des eaux souterraines en milieu urbain, en utilisant une étude de cas dans la ville de Lyon (France). Toutes les structures souterraines connues ont été intégrées dans un modèle numérique. Plusieurs simulations ont été effectuées : l’état actuel de l’écoulement d’eaux souterraines, l’état potentiel de l’écoulement d’eaux souterraines (sans structures souterraines), un état intermédiaire (sans structures imperméables) et une simulation en transitoire de l’état actuel des écoulements d’eaux souterraines. Les résultats montrent que les structures souterraines fragmentent les systèmes d’écoulement d’eaux souterraines conduisant à une modification du régime de l’aquifère. Pour le cas étudié, les systèmes d’écoulement sont stables au cours du temps avec une simulation en transitoire. Les structures avec des systèmes de drainage ont un impact majeur sur les systèmes d’écoulement. L’effet de barrière des structures imperméables est négligeable à cause du faible gradient hydraulique de la zone. L’étude démontre que la définition d’un écoulement potentiel d’eaux souterraines en milieu urbain et la représentation des systèmes des flux en milieu urbain, qui impliquent la compréhension de l’impact des structures souterraines, sont des sujets importants en matière de planification urbaine souterraine.ResumenLas estructuras del subsuelo han demostrado tener una gran influencia sobre los recursos subterráneos en los acuíferos urbanos. Se propone una metodología para evaluar el estado actual y potencial del flujo de agua subterránea en una zona urbana. El estudio desarrolla un enfoque de modelado tridimensional para entender los impactos acumulativos de las infraestructuras del subsuelo en el flujo de las aguas subterráneas urbanas, usando un caso de la ciudad de Lyon (Francia). Todas las estructuras conocidas del subsuelo fueron integradas en el modelo numérico. Se llevaron a cabo varias simulaciones: el estado actual del flujo de agua subterránea, el estado potencial del flujo de agua subterránea (sin estructuras en el subsuelo), un estado intermedio (sin estructuras impermeables), y una simulación transitoria del estado actual del flujo de agua subterránea. Los resultados muestran que las estructuras en el subsuelo fragmentan los sistemas de flujo del agua subterránea conduciendo a una modificación del régimen del acuífero. Para el caso estudiado, se demuestra que los sistemas de flujo son estables a través del tiempo con una simulación transitoria. Se muestra que las estructuras con sistemas de drenaje tienen un impacto mayor en los sistemas de flujo. El efecto de barrera de las estructuras impermeables fue despreciable debido al pequeño gradiente hidráulico de la zona. El estudio demuestra que la definición de un flujo potencial de agua subterránea urbana y la esquematización de los sistemas de flujo urbano, que implica entender el impacto de las estructuras del subsuelo, son cuestiones importantes con respecto a la planificación de las estructuras del subsuelo urbano.摘要地下建筑物显示出对城市含水层下层土壤有很大的影响。本文论述了评价城区地下水流实际和潜在的状态的方法。本研究利用(法国)里昂一个实例开发了三维模拟方法以了解地下建筑对城市地下水流的累积影响。所有已知的地下建筑物都并归到数值模型中。进行了几个模拟 :地下水流的实际状态,地下水流的潜在状态(无地下建筑物),中间状态(没有不透水的建筑物),地下水实际状态的瞬时模拟。结果显示,地下建筑物使地下水流系统四分五裂,致使含水层发生改变。在研究的实例中,水流系统在瞬时模拟中显示随着时间的过去趋于稳定。有排水系统的建筑物显示对水流系统有重要影响。无透水建筑物的屏障效应可以忽略,因为该地区水力梯度太小。研究显示,潜在城市地下水流的定义及城市水流系统的描述涉及到对地下建筑物影响的了解,是城市地下规划的重要课题。ResumoEstruturas subterrâneas comprovadamente apresentam uma grande influência sobre os recursos subterrâneos de aquíferos urbanos. Propõe-se neste estudo uma metodologia para avaliar a situação real e potencial do escoamento de água subterrânea em uma área urbana. O estudo desenvolve uma modelagem tridimensional para entender os impactos cumulativos das infraestruturas subterrâneas sobre o escoamento de água subterrânea urbana utilizando-se o caso da cidade de Lyon (França). Todas as estruturas subterrâneas conhecidas foram integradas ao modelo. Foram realizadas diversas simulações: a situação real do escoamento de água subterrânea, a situação potencial do escoamento de água subterrânea (sem estruturas subterrâneas) e uma simulação de transitório da situação real do escoamento de água subterrânea. Os resultados mostram que as estruturas subterrâneas segregam o sistema de escoamento alterando o regime de escoamento do aquífero. O efeito de barreira das estruturas impermeáveis foi desprezível devido ao gradiente hidráulico reduzido na área. O estudo demonstra que a definição de uma situação potencial de escoamento de água subterrânea urbana e o mapeamento do escoamento de sistemas aquíferos urbanos, que envolvem o entendimento do impacto de infraestruturas, são discussões importantes com respeito ao planejamento do ambiente subterrâneo urbano.

Influences on the establishment and dominance of vegetation in stormwater infiltration basins

Infiltration basins are widely used in urban environments as a technique for managing and reducing the volume of stormwater. These basins can be spontaneously colonized by wild plants, which can be used as bioindicators of edaphic characteristics. As the basins are anthropogenic environments, the description of plant biodiversity allows the determination of which species colonize such environments and identification of the relationships between plants, basin type and operation. Nineteen infiltration basins were selected according to their catchment types (industrial, urban, agricultural). The dominant species were identified and sampled. Rumex sp., Taraxacum sp. and Artemisia sp. are the three types most represented (88, 61 and 55% respectively of the basins studied). Their families and their respective orders are those most commonly found (Caryophyllales, Asterales and Polygonaceae, Asteraceae). Poaceae is the family grouping with the largest number of different species (11). Although each species occupies only 1 or 2 basins, plants of this family occupy 61% of the basins. Although the catchment characteristics of the 19 basins do not play a direct role in the diversity of plant families, they can influence the presence or absence of certain species. Thus, these plants can be used as bio-indicators of basin soil and operating characteristics, such as sediment depths, inundation frequency and duration.