International audience | Growth in the presence of sucrose was shown to confer to Arabidopsis thaliana (thale cress or mustard weed) seedlings, under conditions of in vitro culture, a high level of tolerance to the herbicide atrazine and to other photosynthesis inhibitors. This tolerance was associated with root-to-shoot transfer and accumulation of atrazine in shoots, which resulted in significant decrease of herbicide levels in the growth medium. In soil microcosms, application of exogenous sucrose was found to confer tolerance and capacity to accumulate atrazine in Arabidopsis thaliana plants grown on atrazine-contaminated soil, and resulted in enhanced decontamination of the soil. Application of sucrose to plants grown on herbicide-polluted soil, which increases plant tolerance and xenobiotic absorption, thus appears to be potentially useful for phytoremediation.

Corresponding author. fax: +49 381 498 2159. E-mail address: bernd.lennartz@uni-rostock.de (B. Lennartz). | International audience | This work was initiated to study the effects of climate induced soil water status variations which can reach extreme values under natural conditions on the sorption process of hydrophobic organic compounds. Based on the classical slurry batch methodology an approach is developed that allows the fast and careful complete drying of soil suspensions (microwave technique). Classical adsorption experiments were followed by three desorption steps with and without drying cycles. Drying and re-wetting enhanced the sorption-desorption hysteresis and Freundlich adsorption coefficients increased from 5.9 to 16 and 5.2 to 21 over three drying cycles for diuron and terbuthylazine respectively. Assuming the validity of a dual stage adsorption process, model evaluation suggests that drying is as a shrinking-like process leading to conformational changes of the dominant sorbent (soil organic matter) which restrict the intra-micro-particle diffusion. Rewetting only leads to a partial recovery of the diffusional pore space.

International audience | From 1899 to 2002, sandy Luvisol in the Paris region has been intensively irrigated with raw wastewater, resulting in major soil pollution by metallic trace elements (MTE). To identify the soil phases implicated in retaining these metals, sequential extractions were performed on a solum irrigated with untreated wastewater and another reference solum. The endogenous and exogenous fractions of MTE in the contaminated soil were discriminated using correlations between MTE and major elements defined from unpolluted soils of the area. In the contaminated soil no exogenous lead and chromium are present below the surface horizon, whereas exogenous zinc and copper are found down to the base of the solum. The endogenous MTE are mainly found in the residual fraction. Exogenous MTE appear to be associated with organic matter in the surface horizon, and exogenous zinc seems to be readsorbed on iron and manganese oxyhydroxides in the underlying horizons. After 100 years of intensive irrigation with wastewater, no exogenous Pb and Cr are found in the subsoil, while exogenous Zn and Cu are found down to the base of the solum, mostly readsorbed.

International audience | Phytoremediation is an emerging strategy to remediate soils contaminated with pollutants like explosives in which plants will uptake, degrade and/or accumulate pollutants. To implement this technology on a site contaminated with RDX, we chose rice, which is able to grow in lagoons, and we tested its ability to grow in soils with high levels of RDX and to decrease RDX concentrations in soil. Rice was grown for 40 days in soil contaminated with increasing [14C]RDX concentrations. Emergence and growth were not affected by RDX. Total chlorophyll content decreased with RDX concentrations of over 500 mg kg−1. Amounts of chlorophyll were correlated with the appearance of necrosis in leaf extremities. After 40 days, rice translocated 89% of uptaken radioactivity to leaves with 90% in leaf extremities. Analyzes of leaf extracts showed that 95% of radioactivity was RDX in its parent form. Necrosis appears to be a phytotoxic symptom of RDX accumulation.

Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas-aerosol interactions, organic nitrogen and N2 fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N2O, NO and bi-directional NH3 exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols

[Departement_IRSTEA]MA [TR1_IRSTEA]TED / EPURE | International audience | Samples of pig slurry, as well as dairy and poultry manures collected in Brittany (western France)were analysed to test the ability of sterol profiles to provide a fingerprint of pig slurry contribution to soil organic matter. The data show that the 5β-stanol, known as coprostanol, is the most abundant sterol present in pig slurry, whereas this compound occurs only in minor amounts in both poultry and dairy manures. Moreover, systematic variations of (campesterol + sitosterol)/cholesterol (i.e., C28+29/C27) and (coprostanol + epi-coprostanol)/cholesterol (i.e., 5β/C27) ratios allow to discriminate clearly pig slurry from poultry and dairy manures. The robustness of the pig slurry sterol fingerprint was tested by analysing the sterol profiles of soil samples from an experimental field that had received a massive pig slurry input between 10 to 14 years ago. The results indicate that the specific sterol profile of pig slurry is conservative once the slurry has been incorporated into the soil. In particular, the diagnostic 5β/C27 ratio proves to be constant with time in soils having received pig slurry application, even 10 years after the end of the application. The sterol fingerprint of pig slurry is thus sufficiently distinctive from dairy and poultry manures, and also sufficiently time-resistant, to be of diagnostic value in determining whether a soil sample was once contaminated by pig slurry.

A multiplicative and a semi-mechanistic, BWB-type [Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatalconductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggens, J. (Ed.), Progress in Photosynthesis Research, vol. IV. Martinus Nijhoff, Dordrecht, pp. 221–224.] algorithm for calculating stomatalconductance (gs) at the leaf level have been parameterised for two crop and two tree species to test their use in regional scale ozone deposition modelling. The algorithms were tested against measured, site-specific data for durum wheat, grapevine, beech and birch of different European provenances. A direct comparison of both algorithms showed a similar performance in predicting hourly means and daily time-courses of gs, whereas the multiplicative algorithm outperformed the BWB-type algorithm in modelling seasonal time-courses due to the inclusion of a phenology function. The re-parameterisation of the algorithms for local conditions in order to validate ozone deposition modelling on a European scale reveals the higher input requirements of the BWB-type algorithm as compared to the multiplicative algorithm because of the need of the former to model net photosynthesis (An)

peer reviewed | It is now irrefutable that air pollution caused by large amounts of Total Suspended Particulates (TSP) and respiratory particulates or Particulate Matter less than 10 mu m in aerodynamic diameter (PM10) has numerous undesired consequences on human health. Air quality degradation far from the African continent, in the US and in Europe, caused by high concentrations of African dust, is seen as a major threat even though most of these countries are very distant from the Sahara. Surprisingly, no estimates of TSP or PM10 levels near the Saharan dust source are available. Based on horizontal visibility observations which are reduced by the presence of dust in the atmosphere, TSP and PM10 levels are estimated throughout the year 2000 at Nouakchott-Airport, Mauritania, using relations found in the literature. It appears that concentrations of particles are significant both in terms magnitude and frequency, as the 24-hour PM10 thresholds established by the US EPA National Ambient Air Quality Standards and the EU Limits Values for Air Quality were exceeded 86 and 137 times, respectively. The average annual concentration is far above air quality standards and estimated at 159 mu g m(-3) for TSP and 108 mu g m(-3) for PM10. These very high particulate levels are likely to represent an important public health hazard and should be considered as a major environmental risk.

Recent EU legislation is directed to reverse the upward trends in the concentrations of agricultural pollutants in groundwater. However, uncertainty of the groundwater travel time towards the screens of the groundwater quality monitoring networks complicates the demonstration of trend reversal. We investigated whether trend reversal can be demonstrated by relating concentrations of pollutants in groundwater to the time of recharge, instead of the time of sampling. To do so, we used the travel time to monitoring screens in sandy agricultural areas in the Netherlands, determined by 3H/3He groundwater dating. We observed that concentrations of conservative pollutants increased in groundwater recharged before 1985 and decreased after 1990. Thereby, we demonstrated trend reversal of groundwater quality. From this research we concluded that 3H/3He dating can be used to facilitate (re)interpretation of existing groundwater quality data. The presented approach is widely applicable in areas with unconsolidated granular aquifers and large agricultural pressures on groundwater resources. Groundwater age dating reveals trends and trend reversal in groundwater quality.