Impact assessment of climate change on farming systems in the South Mediterranean area: a Tunisian case study

Regional Environmental Change - This study considers a quantitative approach for assessing the performance of Tunisian farming systems to face climate change. It is based on the resilience concept...     

Evaluation of the diffusion size classifier (meDiSC) for the real-time measurement of particle size and number concentration of nanoaerosols in the range 20-700 nm

In the frame of assessing exposure to nanostructured particles, the aim of this work is to study the performance of a new device devoted to the real-time measurement of nanostructured aerosol: the meDiSC (Diffusion Size Classifier, Matter Engineering, Switzerland). This instrument is based on unipolar diffusion charging of particles which are then collected successively in diffusion and filtration stages. From currents measured in these stages, the instrument is capable of determining aerosol mean size and number concentration. These data were compared to reference measurements regarding monodisperse aerosols in a range from 20 to 700 nm; the relative biases were found unsatisfying. This led us to investigate the principle of the instrument. Consequently, the charging law of the diffusion charger was experimentally established, as well as the calibration curve allowing the determination of the mean size of the particles. The latter analysis was completed by a model based on diffusion theory. Our results indicate the possibility to improve the range of size measurement up to 350 nm. Measured particle size and number concentration were also used to calculate geometric surface-area concentration; the experimental data were compared to a reference calculated surface-area concentration. The results demonstrate the possibility to evaluate this parameter within acceptable uncertainty. In a second step, the meDiSC was challenged with polydisperse aerosols. It was observed that meDiSC overestimates particle size by a factor 1.7, while particle number concentrations are found within ±40% of the reference. The model applied to polydisperse aerosols indicates that polydispersity little influences particle size up to 300 nm while geometric standard deviation remains below 1.7.     

Internal distribution of uranium and associated genotoxic damages in the chronically exposed bivalve Corbicula fluminea

Uranium (U) internal distribution and involved effects in the bivalve Corbicula fluminea have been studied after direct chronic exposure (90 d, 10 μg.L-1). U distribution was assessed at the subcellular level (Metal Rich Granules -MRG-, pellets and cytosol fractions) in two main organs of the bivalve (gills and visceral mass). Micro-localisation was investigated by TEM-EDX analysis in the gills epithelium. DNA damage in gill and hemolymph samples was measured by the Comet assay. The 90-d exposure period led to a significant increase of U concentration in gills over time (×5) and a large U quantity in subcellular granules in gills. Finally, a significant increase (×2) in DNA damage was noted in exposed gills and haemocytes. This study shows that the accumulation levels and consequently the potential toxicity cannot be successfully predicted only on the basis of concentration in water or in tissues and subcellular fractions after chronic exposure.     

Plant uptake of pesticides and human health: dynamic modeling of residues in wheat and ingestion intake

Human intake of pesticide residues from consumption of processed food plays an important role for evaluating current agricultural practice. We take advantage of latest developments in crop-specific plant uptake modeling and propose an innovative dynamic model to estimate pesticide residues in the wheat-environment system, dynamiCROP. We used this model to analyze uptake and translocation of pesticides in wheat after foliar spray application and subsequent intake fractions by humans. Based on the evolution of residues in edible parts of harvested wheat we predict that between 22 mg and 2.1 g per kg applied pesticide are taken in by humans via consumption of processed wheat products. Model results were compared with experimentally derived concentrations in wheat ears and with estimated intake via inhalation and ingestion caused by indirect emissions, i.e. the amount lost to the environment during pesticide application. Modeled and measured concentrations in wheat fitted very well and deviate from less than a factor 1.5 for chlorothalonil to a maximum factor 3 for tebuconazole. Main aspects influencing pesticide fate behavior are degradation half-life in plant and time between pesticide application and crop harvest, leading to variations in harvest fraction of at least three orders of magnitude. Food processing may further reduce residues by approximately 63%. Intake fractions from residues in sprayed wheat were up to four orders of magnitude higher than intake fractions estimated from indirect emissions, thereby demonstrating the importance of exposure from consumption of food crops after direct pesticide treatment.     

Model reduction via principal component truncation for the optimal design of atmospheric monitoring networks

A numerically efficient methodology for the optimal design of monitoring networks aiming at the surveillance of accidental atmospheric release is proposed in this paper. In a realistic context, the design of such a network requires the knowledge of a database of potential dispersion accidents occurring in the domain of the study. An objective function measures the ability of a potential network to provide measurements in order to reconstruct any accidental plume taken from the database. In the optimisation of such cost functions with respect to networks, most of the computational time is spent in the evaluation of the function, especially if the accidents database is large. In this paper we show how to optimally reduce this database and how this affects the design via a mathematical expansion in the cost function. We introduce methods based on principal component analysis, which are rigorous when the cost function is of least-squares type. These methods are then tested and validated with success on the design of a radionuclides monitoring network to be deployed over France. This is the so-called Descartes network which will be operated by the French Institute for Radiation and Nuclear Safety. These techniques are then applied on Descartes to solve several issues that are computationally demanding, but are also of more general interest, such as: how should one sequentially deploy the stations of the network? How is affected the optimal network when other European potential radiological sources are taken into account?     

Objectives for management of socio-ecological systems in the Great Barrier Reef region,Australia

A wide range of goals and objectives have to be taken into account in natural resources management. Defining these objectives in operational terms, including dimensions such as sustainability, productivity, and equity, is by no means easy, especially if they must capture the diversity of community and stakeholder values. This is especially true in the coastal zone where land activities affect regional marine ecosystems. In this study, the aim was firstly to identify and hierarchically organise the goals and objectives for coastal systems, as defined by local stakeholders. Two case study areas are used within the Great Barrier Reef region being Mackay and Bowen–Burdekin. Secondly, the aim was to identify similarities between the case study results and thus develop a generic set of goals to be used as a starting point in other coastal communities. Results show that overarching high-level goals have nested sub-goals that contain a set of more detailed regional objectives. The similarities in high-level environmental, governance, and socio-economic goals suggest that regionally specific objectives can be developed based on a generic set of goals. The prominence of governance objectives reflects local stakeholder perceptions that current coastal zone management is not achieving the outcomes they feel important and that there is a need for increased community engagement and co-management. More importantly, it raises the question of how to make issues relevant for the local community and entice participation in the local management of public resources to achieve sustainable environmental, social, and economic management outcomes.     

Managing Fleet Capacity Effectively Under Second-Hand Market Redistribution

Fishing capacity management policies have been traditionally implemented at national level with national targets for capacity reduction. More recently, capacity management policies have increasingly targeted specific fisheries. French fisheries spatially vary along the French coastline and are associated to specific regions. Capacity management policies, however, ignore the capital mobility associated with second-hand vessel trade between regions. This is not an issue for national policies but could limit the effectiveness of regional capacity management policies. A gravity model and a random-effect Poisson regression model are used to analyze the determinants and spatial extent of the second-hand market in France. This study is based on panel data from the French Atlantic Ocean between 1992 and 2009. The trade flows between trading partners is found to increase with their sizes and to be spatially concentrated. Despite the low trade flows between regions, a net impact analysis shows that fishing capacity is redistributed by the second-hand market to regions on the Channel and Aquitaine from central regions. National capacity management policies (constructions/destructions) have induced a net decrease in regional fleet capacity with varying magnitude across regions. Unless there is a change of policy instruments or their scale of implementation, the operation of the second-hand market decreases the effectiveness of regional capacity management policies in regions on the Channel and Aquitaine.     

Comparative bioaccumulation kinetics of trace elements in Mediterranean marine sponges

While marine organisms such as bivalves, seagrasses and macroalgae are commonly used as biomonitors for the environment pollution assessment, widely distributed sponges received little attention as potential helpful species for monitoring programmes. In this study, the trace element and radionuclide bioaccumulation and retention capacities of some marine sponges were estimated in a species-comparative study using radiotracers technique. Six Mediterranean species were exposed to background dissolved concentrations of ^110mAg, ²⁴¹Am, ¹⁰⁹Cd, ⁶⁰Co, ¹³⁴Cs, ⁵⁴Mn, ⁷⁵Se and ⁶⁵Zn allowing the assessment of the uptake and depuration kinetics for selected elements. Globally, massive demosponges Agelas oroides, Chondrosia reniformis and Ircinia variabilis displayed higher concentration factor (CF) than the erectile ones (Acanthella acuta, Cymbaxinella damicornis, Cymbaxinella verrucosa) at the end of exposure, suggesting that the morphology is a key factor in the metal bioaccumulation efficiency. Considering this observation, two exceptions were noted: (1) A. acuta reached the highest CF for ^110mAg and strongly retained the accumulated metal without significant Ag loss when placed in depuration conditions and (2) C. reniformis did not accumulate Se as much as A. oroides and I. variabilis. These results suggest that peculiar metal uptake properties in sponges could be driven by specific metabolites or contrasting biosilification processes between species, respectively. This study demonstrated that sponges could be considered as valuable candidate for biomonitoring metal contamination but also that there is a need to experimentally highlight metal-dependant characteristic among species.     

Field Evidence of Dissolution and Degradation Rates Enhancement During ISCR and ENA Treatments of Chlorinated Solvents

This article presents field tests comparing two methods of treatment of chlorinated solvents undertaken at the same site. The site is an automobile factory where two chlorinated solvents (CS) plumes were identified. At the first source, in situ chemical reduction (ISCR) was applied, while at the second one, enhanced natural attenuation (ENA) was used. A set of specific multilevel sampling wells were installed approximately 20 m downgradient of the sources to estimate the efficiency of the treatments. The presence of a low‐permeability layer (source 1) or a thick oil lens (source 2) in the top part of the aquifer prevented the CS from reaching the bottom of the aquifer. These layers led to difficulties treating the contamination. At the ISCR and ENA treatment zones, the concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) did not change significantly, while the concentration of metabolites (cis‐1,2‐DCE, vinyl chloride, and ethene) significantly increased 50 to 150 days after treatment. Due to high concentration of CS in the source zone, a mass balance calculation, including chlorine, was possible. It showed that around 1 to 2 percent of the injected products were used to reduce the CS. A detailed analysis and 1D analytical modeling of CS concentrations showed that the treatment led to a large (two to three times) increase in dissolution of the organic phase. This explains why, despite an efficient treatment, the PCE and TCE concentrations remained virtually unchanged. Degradation rates also increased due to the treatment. Due to some differences in the source‐zone chemistry, it was not possible to differentiate between the ISCR and ENA efficiencies. © 2013 Wiley Periodicals, Inc.