Les lysimètres de petite taille : un outil pertinent d'évaluation du transfert des pesticides ?

Small size lysimeters placed under field conditions are compared to field studies for pesticide leaching and fate. Such column apparatus allows easy collection of leachates and use of radiolabeled pesticides. Soil structure can also be preserved as well as when using the usual larger lysimeters. Moreover, the small size permits an increase in the replicate number and to avoid soil sampling variability. Two exemples are provided to evaluate the relevance of those experimental models compared to field monitoring campaigns. / Des lysimètres de petite taille, placés sous conditions naturelles, sont utilisés en parallèle avec des expériences de suivi de transfert d'herbicides au champ. Ce type de dispositif permet une récolte facile des eaux de percolation ainsi que l'utilisation de molécules marquées. Comme pour des lysimètres classiques de grande taille, il est possible de travailler en préservant la structure du sol mais leurs faibles dimensions permettent d'augmenter le nombre de répétitions ainsi que de s'affranchir des problèmes d'échantillonnage. Deux exemples de résultats obtenus sont présentés pour permettre de juger de la validité de ce type de modèle par rapport à des résultats de plein champ

La pollution de l'eau par les produits phytosanitaires : état et origine

Les campagnes d'analyse des eaux de surface ou souterraines utilisées comme ressource en eau potable montrent fréquemment une pollution par les produits phytosanitaires au-delà de la norme UE. Cette situation est en partie due à une agriculture intensive, au non respect des bonnes pratiques agricoles, aux usages non agricoles des pesticides mais également à l'existence de sites particulièrement vulnérables (réseau hydrologique dense et diffus, relief accidenté, sols filtrants ou fissurés, nappes peu profondes). Son évaluation peut être réalisée à différentes échelles. Cependant, seule l'étude régionale apparaît comme satisfaisante. En effet, elle permet de mieux cibler les produits à rechercher, les dates d'échantillonnage et le type d'eau à surveiller en fonction des ressources en eau potable. Les pesticides mis en cause dans la pollution de l'eau en France sont actuellement peu nombreux : atrazine, simazine, lindane, carbofuran, phénylurées. Mais cette liste peut se diversifier en prenant en compte la spécificité de l'agriculture locale par réduction de l'échelle d'investigation ou par la prise en compte des produits de dégradation des pesticides utilisés (dééthylatrazine). Pour les eaux de surface, la pollution peut être très élevée mais de courte durée. Elle est étroitement liée aux possibilités de transport des pesticides par ruissellement et à l'effet de dilution par les eaux provenant de secteurs non traités. En revanche, pour les eaux souterraines, la pollution est plus discrète mais elle peut être permanente. Elle est régulée par le processus de lessivage, lui-même lié à la disponibilité du produit et à la dynamique de l'eau. Dans le cas où le pesticide est à la fois persistant et quelque peu mobile, il peut y avoir un stockage du produit dans le sol, qui entretient la pollution des eaux souterraines.The pollution of water by pesticides: state and origin. In Europe, monitoring campaigns of surface and groundwaters used for drinking water frequently show pollution by pesticides, above the EU specification. This situation is due to intensive agriculture, non-respect of good agricultural practices, non-agricultural uses and the existence of especially vulnerable sites (eg, thick and diffuse hydrological system, broken relief, filtering or cracked soils, water table lying near the surface). The assessment of the pollution can be conducted at different levels. However, local study appears to be the only satisfactory method. Indeed, it allowed us to focus on some pesticides, sampling dates and water supplies, in relation to the local characteristics. In France, few pesticides are involved in water pollution: atrazine, simazine, lindane, carbofuran and phenylureas. However, this list would be different if practices carried out locally or degradation products (deethylatrazine) were taken into account. The pollution of surface water can reach a high level but for a small time. It is closely related to the ability of pesticides to be transported by runoff, and the dilution with water from untreated areas. In contrast, groundwater is weakly but, in some instances, continuously polluted. This depends on the leaching processes, and, hence, on the availability of pesticides and the water dynamics. In the case of pesticides with high persistance and relatively good mobility, the storage of pesticides in soil sustains the groundwater pollution

Direct link between fluoranthene biodegradation and the mobility and sequestration of its residues during aging

International audienceThe aim of this study was to assess the influence of the polycyclic aromatic hydrocarbons (PAH)-degrading activity in the fate of fluoranthene in soils. Three soil samples with different degrading activities (an industrial sod, the same industrial soil after biostimulation, and an agricultural sod) were spiked with C-14-fluoranthene and incubated for 6 mo, with monitoring of biodegradation and mineralization. To follow the distribution C-14-fluoranthene residues (i.e., C-14-fluoranthene and its degradation products) among the soil compartments, we performed successively leaching, centrifiigation (to collect intraaggregate pore water), solvent extraction, and combustion of the soil columns. In the industrial soil, no mineralization of C-14-fluoranthyene was observed, and only 3% of the initial C-14-activity was non-extractable (with acetone:dichloromethane) after 165 d of incubation. The biostimulation (addition of unlabeled polycyclic aromatic hydrocarbons) increased the degrading activity in this soil (59% of 14 C-fluoranthene was mineralized) and increased the residues sequestration (13% of 14 C-activity was non-extractable). The microflora of the agricultural soil mineralized C-14-fluoranthene more slowly and to a lesser extent (25%) than the biostimulated soil, but a higher amount of C-14-activity was sequestered (41 %). Thus, the rate and extent of 14C-fluoranthene mineralization seemed to be related to the C-14-activity sequestration by controlling the accumulation of degradation products in the soil. C-14-Fluoranthene biodegradation enhanced the concentration of C-14-polar compounds in the intra-aggregate pore water. Our results point out the close link between fluoranthene biodegradation and two key aging processes, diffusion and sequestration, in soils. biodegradation controls the mobility and sequestration of residues by transforming fluoranthene into more polar molecules that can diffuse into the intra-aggregate pore water and then might become bound to the matrix or entrapped in the microporosity

Certification of the European Reference Soil Set (IRMM-443 - EUROSOILS). Part 2: Soil-pH in Suspensions of Water and CaCl2.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Certification of the European Reference Soil Set (IRMM-443 - EUROSOILS). Part 1: Adsorption Coefficients for Atrazine, 2.4-D and Lindane.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Interactions of Water Quality and Integrated Groundwater Management: Examples from the United States and Europe

Groundwater is available in many parts of the world, but the quality of the water may limit its use. Contaminants can limit the use of groundwater through concerns associated with human health, aquatic health, economic costs, or even societal perception. Given this broad range of concerns, this chapter focuses on examples of how water quality issues influence integrated groundwater management. One example evaluates the importance of a naturally occurring contaminant Arsenic (As) for drinking water supply, one explores issues resulting from agricultural activities on the land surface and factors that influence related groundwater management, and the last examines unique issues that result from human-introduced viral pathogens for groundwater-derived drinking water vulnerability. The examples underscore how integrated groundwater management lies at the intersections of environmental characterization, engineering constraints, societal needs, and human perception of acceptable water quality. As such, water quality factors can be a key driver for societal decision making