VOC in an urban and industrial harbor on the French North Sea coast during two contrasted meteorological situations

Two measurement campaigns of volatile organic compounds (VOC) were carried out in the industrial city of Dunkerque, using Radiello passive samplers during winter (16–23 January) and summer (6–13 June) 2007. 174 compounds were identified belonging to six chemical families. Classifying sampling sites with similar chemical profiles by hierarchical ascending classification resulted in 4 groups that reflected the influence of the main industrial and urban sources of pollution. Also, the BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) quantification allowed us to map their levels of concentration. Benzene and toluene (BT) showed high concentrations in Northern Dunkerque reflecting the influence of two industrial plants. Differences among spatial distributions of the BT concentrations over contrasted meteorological conditions were also observed. An atypical ratio of T/B in the summer samples led us to investigate the BTEX origins shedding light on the contribution of pollutants transported across various zones of VOC emissions situated in Europe.     

Using research-based knowledge to underpin waste and resources policy.

The concept of a knowledge-based approach to policy making (also referred to as 'evidence-based policy making' or 'science meets policy') has been around for 10 years, and is widely 'signed up to' by Governments. This paper examines the theory and the practice at national government (using the UK as a case study) and European levels, looking at how the knowledge-based approach has been applied in waste and resources management. There is general agreement that a knowledge-(or evidence-) based approach to policy making is a 'good thing'; however putting the concept into practice has proven challenging and is still evolving. The linkages between researchers and policy makers need to be further strengthened, as does the 'demand' for evidence from policy; requiring policy specialists to articulate their requirements for evidence sufficiently well in advance, and to do so routinely, is still an area of weakness. Using a model developed by the UK's Department for Environment, Food and Rural Affairs (Defra), we examine in detail some of the implications of changing the question from 'is this good research on waste and resources issues?' to 'is this good evidence for waste and resources policy?'. The paper also provides recommendations for further work required to achieve this at a European level, and for priority areas where international co-ordination of waste and resources research could add most value to policy.     

Development of a standardized in vitro approach to evaluate microphysical, chemical, and toxicological properties of combustion-derived fine and ultrafine particles

Ultrafine particles represent a growing concern in the public health community but their precise role in many illnesses is still unknown. This lack of knowledge is related to the experimental difficulty in linking their biological effects to their multiple properties, which are important determinants of toxicity. Our aim is to propose an interdisciplinary approach to study fine(FP) and ultrafine(UFP) particles, generated in a controlled manner using a mini CAST(Combustion Aerosol Standard) soot ...     

Impact of radical versus non-radical pathway in the Fenton chemistry on the iron redox cycle in clouds

Modeling studies have shown that the Fenton reaction of iron(II) with H2O2 can contribute, in a significant amount, to OH radicals production in cloud droplets. However, the destruction mechanism of hydrogen peroxide by iron(II) is still uncertain. Two reaction pathways for the first step of Fenton chemistry have been advanced: a radical pathway which considers an OH radical production and a non-radical pathway considering ferryl ion production. The aim of this work is to evaluate the impact of these two possible reaction pathways for Fenton chemistry on the iron redox cycle in cloud droplets. For this purpose, the numerical model of multiphase chemistry M2C2 has been applied to a rural chemical scenario representative of continental conditions. This study highlights that the iron redox cycling is driven by Fenton reaction whatever Fenton mechanism is considered. The ferryl ion chemistry becomes significant in the iron redox cycling when this species is considered as an active intermediate in Fenton chemistry and under night time conditions the iron redox chemistry is controlled by the ferryl ion reactivity. The partitioning of iron between its two main oxidation states (+II and +III) in cloud droplets, which is the indicator of the iron oxido-reduction potential, does not change significantly between the two cases. However, for the non-radical case, the ferryl ion concentration is up to four orders of magnitude higher than the OH concentration highlighting its potential role in oxidative capacity of cloud droplets.     

Influence of different digital terrain models (DTMs)on alpine permafrost modeling

The thawing of alpine permafrost due to changes in atmospheric conditions can have a severe impact, e.g., on the stability of rock walls. The energy balance model, PERMEBAL, was developed in order to simulate the changes and distribution of ground surface temperature (GST) in complex high-mountain topography. In such environments, the occurrence of permafrost depends greatly on the topography, and thus, the digital terrain model (DTM) is an important input of PERMEBAL. This study investigates the influence of the DTM on the modeling of the GST. For this purpose, PERMEBAL was run with six different DTMs. Five of the six DTMs are based on the same base data, but were generated using different interpolators. To ensure that only the topographic effect on the GST is calculated, the snow module was turned off and uniform conditions were assumed for the whole test area. The analyses showed that the majority of the deviations between the different model outputs related to a reference DTM had only small differences of up to 1 K, and only a few pixels deviated more than 1 K. However, we also observed that the use of different interpolators for the generation of a DTM can result in large deviations of the model output. These deviations were mainly found at topographically complex locations such as ridges and foot of slopes.     

A model for tropospheric multiphase chemistry: application to one cloudy event during the CIME experiment

A multiphase box model for a remote environment of the troposphere has been developed with an explicit chemistry for both gas and aqueous phase. The model applied to a set of measurements performed by Voisin et al. (2000) during the European CIME experiment for a cloud event on 13th December 1997 at the top of the Puy de Dôme (France). The results of the simulation are compared to the measurements in order to follow the evolution of the ambient chemical composition as a function of the pH and of the varying water content. After verifying that the model retrieves the main features observed in the behavior of species in the cloud droplets, a detailed analysis of the simulated chemical regime is performed. It essentially discusses the sources and sinks of radical in aqueous phase, the relative importance of the oxidation pathways of volatile organic compounds by the main radicals and the conversion of S(IV) into S(VI) which seems to be influenced by the presence of peroxonitric acid, HNO₄, in aqueous phase in the environmental conditions that are considered with low H₂O₂. These numerical results are then compared with the theoretical study from Herrmann et al. (2000), who proposed a slightly different mechanism, including C2 chemistry and transition metal chemistry whereas they neglect some reaction pathways, such as the one involving OHCH₂O₂ radical. This double confrontation between model results and both real experimental data and numerical results from Herrmann et al. (1999c) underlines limitations of such modeling approach that does not include any dynamical or microphysical coupling but also demonstrates its capability to identify the main oxidants or reactants in aqueous phase in real environmental conditions more realistic than a purely theoretical approach. The originality of this study resides in the explicit and exhaustive ways the chemical reactions are treated in aqueous phase and in a first attempt to compare such a detailed chemical scheme to real environmental conditions.     

Evaluation of the ecotoxicological impact of the organochlorine chlordecone on soil microbial community structure,abundance, and function

The insecticide chlordecone applied for decades in banana plantations currently contaminates 20,000 ha of arable land in the French West Indies. Although the impact of various pesticides on soil microorganisms has been studied, chlordecone toxicity to the soil microbial community has never been assessed. We investigated in two different soils (sandy loam and silty loam) exposed to different concentrations of CLD (D0, control; D1 and D10, 1 and 10 times the agronomical dose) over different periods of time (3, 7, and 32 days): (i) the fate of chlordecone by measuring ¹⁴C-chlordecone mass balance and (ii) the impact of chlordecone on microbial community structure, abundance, and function, using standardized methods (-A-RISA, taxon-specific quantitative PCR (qPCR), and ¹⁴C-compounds mineralizing activity). Mineralization of ¹⁴C-chlordecone was inferior below 1 % of initial ¹⁴C-activity. Less than 2 % of ¹⁴C-activity was retrieved from the water-soluble fraction, while most of it remained in the organic-solvent-extractable fraction (75 % of initial ¹⁴C-activity). Only 23 % of the remaining ¹⁴C-activity was measured in nonextractable fraction. The fate of chlordecone significantly differed between the two soils. The soluble and nonextractable fractions were significantly higher in sandy loam soil than in silty loam soil. All the measured microbiological parameters allowed discriminating statistically the two soils and showed a variation over time. The genetic structure of the bacterial community remained insensitive to chlordecone exposure in silty loam soil. In response to chlordecone exposure, the abundance of Gram-negative bacterial groups (β-, γ-Proteobacteria, Planctomycetes, and Bacteroidetes) was significantly modified only in sandy loam soil. The mineralization of ¹⁴C-sodium acetate and ¹⁴C-2,4-d was insensitive to chlordecone exposure in silty loam soil. However, mineralization of ¹⁴C-sodium acetate was significantly reduced in soil microcosms of sandy loam soil exposed to chlordecone as compared to the control (D0). These data show that chlordecone exposure induced changes in microbial community taxonomic composition and function in one of the two soils, suggesting microbial toxicity of this organochlorine.