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Resume L'utilisation d'une culture de chlorelles dans des conditions experimentales bien definies permet le dosage de I'atrazine bioactive du sol sans extraction prealable. La mise au point a ete effectuee avec un materiau non adsorbant (sable). Des concentrations d'atrazine de 0.10μg g−1 de sable peuvent ainsi etre detectees. et dosees avec precision a partir de 0.45 μg g−1 de sable. Des exemples d'application sont donnes pour des terres de composition tres differentes. La comparaison avec la methode utilisant les plantules d'avoine montre que la methode proposee conduit a des resultats du meme ordre de grandeur. Summary The use of Chlorella for biological estimation of atrazine in soil The use of a Chlorella culture in well-defined experimental conditions permits the estimation of atrazine bioactivity in soil without preliminary extraction. The determination was made with a non-absorbant material (sand). In this way, atrazine concentrations of 0.10 μg g−1 of sand could be detected and from 0.45 μg g−1 of sand determined accurately. Examples of applications are given for soils of very different composition. Comparison with the oat-seedling method shows that the method proposed gives results of similar magnitude. Zusammenfassung Die Verwendung von Chlorella zum biologischen Nachweis von Artazin im Baden Unter kontrollierten Bedingungen kann die biologische Aktivitat von Atrazin im Boden mit einer Chlorella-Kultur ohne vorherige Extraktion bestimmt werden, Der Nachweis wurde mit einem nicht-adsorbierenden Material (Sand) durchgefuhrt, Alrazinkonzentrationen von 0.10 μg/g−1 Sand lassen sich auf diese Weise erfassen und ab 0.45 μg g−1 quantitativ nachweisen. Es werden Beispiele mit sehr unterschiedlichen Boden beschrieben. Der Vergleich mit einem Haferbiotest ergab eine gute Ubereinstimmung der Ergebnisse.

Volatilization may represent a major dissipation pathway for pesticides applied to soils or crops, accounting for up to 90% of the application dose in some cases. This paper collects and discusses recent data in the literature about this process. On the day of appli- cation, pesticide volatilization rates ranged from 0.1 g .ha -1.h -1 for prometton compound to 80 g.ha -1.h -1 for fonofos, for example. In ge- neral, pesticides are volatilized from plant surfaces to a greater extent and faster than from the soil. Volatilization continues for from a few days to several weeks (or sometimes even more), occasionally displaying a diurnal cycle. According to the experimental studies re- ported in the literature, the main factors affecting this process during the first few days after treatment have been identified as follows: the physico-chemical characteristics of the compound and the environmental conditions (temperature, soil moisture, nature of the soil or the crop) are key parameters, along with management practices. pesticides / volatilization rate / physico-chemical factors / environmental factors / agricultural practices

The sorption behaviour of a new wheat hybridising agent (clofencet, 2-4-(chlorophenyl)-3-ethyl-2,5-dihydro-5-oxopyridazine-4-carboxylic acid) was investigated in batch equilibrium experiments and compared to that of two other organic acids (2,4-D and salicylic acid). Sorption coefficients K d for the three compounds were determined in 18 Cambisols and Ferralsols. K d values for clofencet were 0.3–9.4 l/kg for Cambisols and 2.1–68 l/kg for Ferralsols. Sorption of clofencet was strongly related statistically to that of salicylic acid. Sorption of clofencet and salicylic acid decreased exponentially with increasing solution pH in Cambisols whereas a bell-shaped curve was obtained for the sorption of salicylic acid in Ferralsols. Sorption of 2,4-D (2,4-dichlorophenoxyacetic acid) was not statistically related to the pH of the different soils. Positively charged oxide surfaces were shown to play a significant role in the sorption of clofencet and salicylic acid. The use of simple correlation and multiple linear regressions suggested that the main sorption mechanisms of clofencet in soils were likely to be ligand exchange on oxide surfaces and, to a lesser extent, cation bridging. Differences in the sorption behaviour of clofencet/salicylic acid and 2,4-D might be attributed to the possibility of the two former compounds forming bidentate complexes with metals.

The sorption of two anionic surfactants and a series of seven nonionic alkylphenolethoxylate surfactants of increasing hydrophilic/lipophilic balance (HLB) in a loamy clay soil was evaluated. The effect of low doses of these surfactants on the sorption characteristics of the fungicide triticonazole was investigated. The critical micellar concentration (CMC) of the surfactants in pure water and soil–water systems, and surfactant sorption were estimated by surface tension measurements using a batch equilibration technique. Triticonazole sorption, alone and in the presence of low doses of surfactants, was also measured by batch equilibration. CMC of the alkylphenol surfactants increased with their HLB. The sorption of surfactants increased with their lipophilicity. CMC in the soil–water systems were considerably higher than in pure water. Sorption of the most lipophilic alkylphenol surfactants at the higher doses significantly increased triticonazole sorption. Proposed mechanisms are modifications of soil surface properties, and increase of soil organic carbon content. Sorption of the other nonionic and anionic surfactants only resulted in monomeric surfactant concentrations in pore water, and did not affect triticonazole sorption. © 1998 Society of Chemical Industry

Summary The sorption–desorption properties of three organic pollutants, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) and the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on soil organic matter (SOM) were studied using kinetic and equilibrium measurements in aqueous suspensions. Chestnut wood, wheat straw, Kraft lignin, composted straw and a soil humic acid were chosen as sorbents to model different states of humification. Physico–chemical characterization using chemical fractionation, potentiometric titration and IR spectroscopy was done on all sorbents. The microbial biomass, sizes of total bacterial and fungal microflora and phenoloxidases activities were determined for the plant materials. The irreversibility of sorption was revealed by the desorption isotherms. Only a small proportion of 2,4-D, which has little affinity for the fresh organic materials, was desorbed. Sorption of 2,4-DCP was strong on straw but was reversible to a large extent, indicating weaker interactions. By comparison, the sorption of 4-CP was significantly less reversible. Thus, the nature of SOM and the properties of the chemicals strongly influenced the extent of sorption and the type of interactions, and it controlled subsequent desorption and possible transformation of the sorbed species. Resume Les proprietes de sorption et de desorption de la matiere organique du sol (MOS) vis a vis de trois polluants organiques, 4-chlorophenol(4-CP), 2,4-dichlorophenol (2,4-DCP), et acide 2,4-dichlorophenoxyacetique (2,4-D) ont eteetudiees en suspensions aqueuses lors d'experimentations cinetiques et a I'equilibre. Plusieurs matieres organiques ont ete choisies comme adsorbants pour modeliser differents etats d'humification: bois de châtaignier, paille de ble, lignine, paille de ble compostee et acide humique extrait d'un sol. Les proprietes physicochimiques des differents adsorbants ont ete caracterisees en utilisant des techniques de fractionnement chimique, titration potentiometrique et spectroscopie IR. Une caracterisation biologique des residus vegetaux a ete menee en effectuant des mesures de biomasse microbienne, de la taille des populations bacterienne et fongique ainsi que d'activites exoenzymatiques (phenoloxydases). Pour la plupart des associations polluant-matiere organique adsorbante, les cinetiques d'adsorption ont une allure identique, montrant un equilibre d'adsorption atteint apres les premieres heures de contact. Cependant, les cinetiques d'adsorption des chlorophenols sur la paille compostee suggerent que des transformations microbiennes ou exoenzymatiques peuvent modifier la retention lorsque une activite microbienne importante est associee aux matieres organiques en cours de decomposition. Certains constituants vegetaux comme les lignines ou les composes phenoliques solubles influencent les proprietes de sorption et de desorption. Les plus grandes capacites d'adsorption sont observees avec la lignine et la paille compostee pour les chlorophenols et avec I'acide humique pour le 2,4-D. L'irreversibilite de la retention est revelee par les isothermes de desorption. Le 2,4-D est desorbe en faible proportion malgre une affinite peu elevee sur les matitres organiques fraiches. La plus forte retention du 2,4-DCP sur les matieres organiques fraiches et humifiees est caracterisee par une reversibilite plus importante, traduisant I'intervention d'interactions de plus faibles energie. Par comparaison, la retention du 4-CP est beaucoup plus irreversible. La nature de la matiere organique du sol et les proprietes des molecules influencent donc les quantites adsorbees et la nature des interactions, et elles sont egalement determinantes pour la desorption et les transformations possibles des polluants adsorbes.

Summary: Retention by a glass fibre filter of the liquid phase of a clay loam soil treated with 14C-diuron provides a novel method for analysis of the herbicide in soil solution. At 26.3% (w/w) soil moisture content, less than 10% of the applied diuron was found in solution, and this percentage decreased slightly with diuron dose. The herbicide was rapidly adsorbed on soil during the first day, but adsorption continued and the concentration of diuron in solution could be further reduced by 36–50% during the following 6 days. Drying the soil after treatment, with possible crystallization of herbicide applied at high doses, tended to fix the solution concentrations. Ethanol (3% v/v) in soil water favoured herbicide dissolution. Increasing soil moisture to 36.3% (w/w) slightly decreased the concentration of the herbicide in solution, but increased the percentage held in solution. Frost and a drying-rewetting cycle had little or no subsequent effect on diuron concentration in soil solution. Resume: La retention de la phase liquide d'une sol argilo limoneux traiteau diuron 14C, par un filtre en fibres de verre, permet l'analyse de l'herbicide dans la solution du sol. A 26,3% (m/m) d'humidite, moins de 10% de l'herbicide est en solution et ce pourcentage diminue avec la dose. L'herbicide est rapidement adsorbe pendant le premier jour mais I'adsorption se poursuit et la concentration du diuron dans la solution du sol peut diminuer de 36 a 50% en 6 jours. Un desseAchement du sol apres le traitement peut favoriser la cristallisation de l'herbicide applique a forte dose ce qui tend a stabiliser la concentration de la solution. La presence d'ethanol (3% v/v) favorise la forme dissoute de l'herbicide. Une augmentation de l'humidite du sol jusqu'a 36,3% (m/m) diminue legerement la concentration de l'herbicide en solution mais accroit le pourcentage d'herbicide dissous. Le gel et un cycle dessechement rVhumidification ont peu ou pas d'effet ulter ieur sur la concentration du diuron dans la solution du sol. Zusammenfassung: Die Retention der Bodenlosung eines tonigen Lehmbodens, der mil 14C-Diuron behandelt worden war, in einem Glasfaserfilter stellt eine neue Methode zur Untersuchung des Herbi zidgehalts in der Bodenlosung dar. Bei einem Gehalt von 26,3 Gew.-% in der Bodenlosung wurden weniger als 10% des applizierten Diurons gefunden, und dieser Prozentsatz nahm mil der Herbiziddosis etwas ab. Das Herbizid wurde am ersten Tag schnell im Boden adsorbiert, aber die Adsorption schritt in den nachsten 6 Tagen weiter fort, so das die Diuronkonzentration in der Losung um 36 bis 50% abnahm. Durch Trocknen des Bodens nach der Behandlung, mil moglicher Auskristal lisation des Herbizids bei hohen Dosen, zeigte sich eine zunehmende Fixierung des Wirkstoffs. Die Zugade von Ethanol (3 Vol.-%) Zur Bodenlosung forderte die Losung des Herbizids. Bei Erhohung der Bodenfeuchtigkeit auf 36,3 Gew.-% nahm die Herbizid-konzentration leicht ab, doch der Losungsgrad nahm zu. Gefrieren und wiederholtes Trocknen und Befeuchten hatten geringe oder keine Wirkung auf die Diuronkonzentration in der Bodenlosung.

Summary The description of adsorption of organic acids by soil with models requires many parameters. It is often difficult to obtain their values, and so we might try to test the application of models with published data on soil characteristics. We used two models in our trials, namely the constant capacitance model and the variable surface charge–variable surface potential model. We modelled the sorption data for three weak organic acids [2,4-D, 2–4-dichloro-phenoxy acetic acid; salicylic acid, 2-hydroxybenzoic acid; and clofencet, 2–4-(chlorophenyl)-3-ethyl-2,5-dihydro-5-oxopyridazine-4-carboxylic acid] in three Cambisols and two Ferralsols. We adopt an additive approach where the five soils were considered to behave as mixtures of goethite and gibbsite. This was done with values taken from the literature on the assumption that the compounds formed monodentate complexes. Variations given by the two models in adsorbed amounts as a result of pH changes were well described for clofencet and 2,4-D but were less successful for salicylic acid. Simulations of sorption isotherms at various pHs ranging from 5 to 8 matched the experimental data closely for clofencet. Prediction of the adsorption of clofencet and 2,4-D in a range of Cambisols and Ferralsols at their native pH was generally good. We attribute the somewhat poorer fit observed for salicylic acid to the formation of bidendate complexes. Further improvement to the modelling should involve the formation of bidentate complexes between organic acids and oxide material and the effects of organic matter, particularly in relation to adsorption of non-ionized compounds.

The transfer of pesticides to the atmosphere leads to a contamination of all atmospheric phases: gaseous, aerosol particles, fog droplets or rainwater. This paper makes a review of observations of pesticides in the atmosphere in France, which started at the end of the 80s. Measured concentrations in rainwater were very high, with maximum values reaching 60 µg.l -1 . Concentrations in fog were much higher than in rainwater. Regarding the gaseous and particulate phases, the measured concentrations range from not detected to 185 ng.m -3 . Very high values (2.6 µg.m -3 ) have been measured locally. This contamination is observed throughout the year, sometimes displaying a seasonal pattern and spatial variability. Compounds which have been banned are still present in the atmosphere. It is also striking that pesticides which could be expected to be not very volatile based on their physico-chemical characteristics are found in the atmosphere.

The surface runoff of a number of pesticides (diuron, isoproturon, atrazine, alachlor, aclonifen, trifluralin, lindane and simazine), chosen for their range of adsorption behaviours, was studied using simulated rainfall applied to small plots over a short time (one hour). Pesticides were applied together onto bare soil using two different sandy loam soils from La Jaillière and Coët Dan sites in France. The surface runoff samples were collected throughout the running of the event and concentrations of pesticides were measured in both liquid and solid phases. Sorption isotherms for isoproturon and diuron on La Jaillière soil as well as eroded particles were measured under equilibrium conditions and compared to their partinioning during surface runoff. At the rainfall intensity used, both soils generated a large load of eroded particles. The average runoff flow rate increased with time for La Jaillière soil while it remained relatively constant at a higher level for the Coët Dan soil. The concentrations of each pesticide in the runoff samples decreased as the experiment proceeded. The pesticides were classified into two types by their partinioning between the liquid and solid phases. Atrazine, simazine, diuron, isoproturon and alachlor were mainly transported in surface runoff water. By contrast 90% of trifluralin and aclonifen was adsorbed onto eroded particles. Lindane was intermediate with a 37% adsorption level. When the contribution of eroded particles was minor, the agronomical concentrations were inversely proportional to the water flow rate. We have proposed a model that describes the mass of chemicals extracted from the soil into surface water during a surface runoff event of a given average duration and flow rate. This model takes into account the dilution of the soil solution and the desorption of chemicals through two parameters called respectively the dilution factor and the extraction retardation factor. The desorption kinetic was the limiting step in the surface runoff of weakly sorbed chemicals such as isoproturon., Le transfert de surface du diuron, de l'isoproturon, de l'atrazine de l'alachlore, de l'aclonifen, de la trifluraline, du lindane, et de la simazine est étudié à l'aide d'une pluie simulée appliquée sur une micro-parcelle de 1 m². Les pesticides ont été épandus ensemble sur une microparcelle contenant un sol reconstitué nu et ce pour deux types de sols limono-sableux provenant des sites de la Jaillière et Coët Dan dans l'ouest de la France. Les échantillons de ruissellement ont été recueillis au cours de la simulation de pluie et les concentrations en pesticides dissous et particulaires ont été mesurées. Parallèlement on a établi les isothermes d'adsorption pour le diuron et l'isoproturon dans les conditions normalisées à la fois sur le sol La Jaillière et des matières en suspension issues de son érosion à la suite d'une simulation de pluie sans produits. On observe que les concentrations en pesticides diminuent avec le temps. On peut classer les produits en deux catégories selon leur répartition entre les phases solide et liquide : l'atrazine, le diuron, l'isoproturon, la simazine et l'alachlore sont principalement transportés dans l'eau du ruissellement tandis que l'aclonifen et la trifluraline sont à plus de 90% transportés sur les particules érodées. Le lindane est intermédiaire avec une fraction de 37% sur les éléments solides du ruissellement. Pour les produits transférés de préférence avec l'eau on observe que les concentrations sont inversement proportionnelles au débit. On propose un modèle pour décrire la quantité de produit extraite du sol dans le ruissellement lors d'une simulation de pluie caractérisée par une intensité et une durée données. Ce modèle prend en compte la dilution de la solution du sol et la desorption des produits à travers deux paramètres qui sont nommés respectivement le facteur de dilution et le facteur de retard d'extraction. Il semblerait que pour les produits à faible adsorption, la cinétique de desorption soit un facteur limitant du transfert en solution.

Biosorption of the 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) and 2-chloro-ethylamino-6-isopropylamino-1,3,5-triazine (atrazine) has been studied on the mycelium of Emericella nidulans and Penicillium miczynskii, isolated from composted wheat straw and a soil respectively. Results obtained with inactivated fungal biomass showed that a rapid adsorption on fungal cell walls surfaces was the main sorption phenomenon for the more hydrophobic molecules. This sorption was only partially reversible. With active living mycelia, additional phenomena were responsible for an increased sorption of all chemicals. This process was slow and depended on the chemical concentration. For 4-CP, it was attributed to biodegradation as demonstrated by the presence of degradation products in solution. Bioaccumulation inside the mycelium could also partially explained the results observed with living biomass for 4-CP, 2,4-DCP and 2,4-D.

The surface runoff of isoproturon and diuron is studied using a simulated rainfall applied to a small 1 m² plot of soil. Isoproturon was less adsorbed by soil than diuron and eroded particles did not contribute a lot to pesticide transfer. A model is then proposed to describe such transfer of pesticide. This model introduces (i) a dilution factor a, which seems proportional to the concentration of the soil solution before applying the artificial rainfall and (ii) an extraction retardation factor b, which is inversely proportional to the partition coefficient between the solid and liquid phases of soil., Le transfert de surface du diuron et de l'isoproturon est étudié à l'aide d'une pluie simulée appliquée sur une micro-parcelle de 1 m². L'isoproturon est moins adsorbé sur le sol que le diuron, et les particules érodées contribuent peu au trans fert des deux pesticides. Un modèle est proposé pour décrire ce transfert. Il introduit un facteur de dilution a, proportionnel à la concentration du pesticide dans la solution du sol avant le ruissellement, et un facteur de retard à l'extraction b, inversement proportionnel au coefficient de partage entre les phases solide et liquide du sol.

We consider as a pollutant any chemical of natural or anthropogenic origin which accumulates in the soil medium and changes the natural soil equilibrium, as a result of human activity. A modern society, however, cannot be developed without the use of natural and synthetic compounds which may be added to the various ecosystems. The art of safeguarding the environment consists of minimizing the amount of out-system compounds reaching the land surface and restraining as much as possible the pollution-generating sites by controlling their disposal habits.

After reaching the soil-solid surfaces, before, while, or after being subjected to biologically or chemically induced transformation, or retained by the soil constituents as sorbed or bound residues, the pollutants are redistributed in the soil profile as solutes and/or water-liquids immiscible, in gaseous form or adsorbed on colloids and other fine particles. The extent of this redistribution and the kinetics of redistribution are controlled by both soil and pollutant properties, by the environmental conditions, and by the management of the polluted lands.

Pollutants retained in the soil may be released into the soil solution, displaced as water-immiscible liquids, or transported into the gaseous phase. The form and rate of release are controlled by the properties of both the pollutants and the medium, as well as by environmental conditions. Nonadsorbed pollutants may be released from the soil through dissolution and volatilization, processes which have been described in Chaps. 3 and 4.

Many activities lead to the introduction of various chemicals into natural media: industrial operations, waste disposal, pesticide and fertilizer applications, irrigation with secondary effluents, etc. To these must be added accidents such as fires, tank leakages, and spills, which locally add large amounts of chemicals. The cumulative result is a growing threat to soils and waters which makes the prediction of the fate of pollutants necessary. Modeling may be a rather efficient tool for making this prediction, so that a very great number of models can be found in the literature. In a survey recently published, Johnson (1994) listed more than 1000 environmental software products. However, models do not constitute a universal or perfect way to achieve this prediction, because they are only more or less simplified representations of the real world, and their application encounters many difficulties which need to be well known by users. Nevertheless, the modelling approach has been shown to be very useful in many instances: research, management, regulatory purposes, and teaching.

After reaching the soil medium, the pollutants are partitioned among the solid, liquid, and gaseous phases. Part of the chemical fraction is transported into the gaseous phase and is lost in the atmosphere. The remaining portion may be dissolved in the soil solution or retained within the soil solid phase as adsorbed molecules, entrapped ganglia, or precipitates. These chemicals are submitted to chemical, photochemical, and surface-induced reactions, leading to their transformation in the course of time. As a result of pollutant transformation, various metabolites — which may be more or less toxic than the parent material — are introduced into the soil medium.

Solubility equilibrium is the final state to be reached by a toxic chemical and the soil water phase under well-defined environmental conditions. Equilibrium provides a valuable reference point that is useful for ascertaining the chemical reaction.

Soil remediation has to be considered when potentially toxic elements or substances present in soils may have adverse effects on biodiversity or human health. The choice of the most suitable treatment is based mainly on the assessment of the risk to the environment imposed by the presence of toxic substances in the soil.

Volatilization is defined as the transition of chemicals from the solid or liquid phase into the vapor phase. Each chemical has a characteristic saturation vapor pressure or vapor density, that varies with temperature. The potential volatility of a chemical is related to its inherent vapor pressure, but actual vaporization rates depend on the environmental conditions and all the other factors that control the behavior of the chemical at the solid-air-water interface. For surface deposits, the actual rates of loss, or the proportionality constants relating vapor pressure to volatilization rates, are dependent upon external conditions that affect movement away from the evaporating surface, such as turbulence, surface roughness, wind speed, etc. The rate at which a pollutant moves away from the surface is diffusion-controlled. Close to the evaporating surface there is relatively little movement of air, and the vaporized substance is transported from the surface through this stagnant air layer only by molecular diffusion. Since the thickness of the stagnant boundary layer depends on air flow rate and turbulence, vapor loss is influenced strongly by the type of soil cover and the atmospheric conditions, e.g., wind in the vicinity of the soil surface. In general, under a given set of conditions, as air turbulence increases, the volatilization rate increases.

The soil is the upper layer of the unsaturated zone of the earth. Soils are very diverse in composition and behavior. The solid phase consists of mineral particles of various sizes and shapes and organic matter in various stages of degradation. Plant roots and the living soil population complete the system.

Pollutants retained on and within the soil solid phase have reached the soil directly as solute, water-immiscible liquid, suspended particles, or in the gaseous phase. Pollutant retention is controlled by the physicochemical and physical properties of the soil solid phase by the properties of the pollutants themselves, and by environmental factors such as temperature and soil moisture content. Since, under natural conditions, we are dealing, in general, not with a single pollutant but with a mixture of pollutants and natural organic and inorganic compounds, the competition between the compounds for the soil adsorption sites will control their retention on or in the soil solid phase. For quantifying the retention of pollutants in the soil solid phase, an equilibrium should be determined; consequently, major attention should be given to the kinetics of the process.

Resume: L'adsorption de plusieurs phcnylure (diuron, linuron. mtox- uron, isoproturon) par des acides humiques augmente lorsque le pH diminue, Letablissement de liaisons hydrogene entre les molecules herbicides el les groupements fonctionnels non disso- cies des acides humiques pourrait expliquer cet effet, Compars au calcium, au meme pH, les cations Fe3+, Al3+, Cu2+ ne modifient pas l'intensite de l'adsorption mais, compte tenu de la composition ionique des acides humiques, on peut supposer l'existence d'interactions entre les molcules herbicides et ces cations fixs sur les acides humiques. Resume: The absorption of certain phcnyl ureas by humie acids The absorption of certain phenylureas (diuron, linuron, metox- uron, isoproturon) by bumic acid increased as the pH diminished. The establishment of hydrogen bonds between herbicide molecules and functional groups, not dissociated with humic acids, could explain this effect as compared with calcium.At the same pH the cations Fe3+, Al3+ and Cu2+ did not modify the intensity of absorption, but taking account of the ionic composition of the humic acids, it can be supposed that there arc interactions between the herbicide molecules and the cations fixed on humic acid. Zusammenfassung die Adsorption mehrerer Phenylharnstoffe (Diuron, Linuron, Metoxuron, Isoproturon) durch Huminsauren steigt bei a bneh- mendem pH, Das Zustandekommen von Wasserstoffbrucken zwischen Hcrbizidmolekulen und den funktionellen. nicht di- soziiertcn Gruppen der Huminsauren knnte diesen Effekt er- klaren, Die Kationen Fe3+, AI3+ and Cu2+ verandern die Intensiai der Adsorption bei demselben pH im Vergleich zu Calcium nieht. Vergegenwartigt man sich aber den ionisehen Aufbau der Huminsauren. so kann die Existenz von Interaktionen zwischen den Hcrhiridmolekulen und den auf den Huminsaurcn fixierten Kanonen vermutet werden

Resume: Une methode est decrite pour la mesure du coefficient de diffusion. Elle est simple a mettre en oeuvre et ne necessite pas de molecules marquees par un isotope radioactif. Appliquee a l'atrazine en solution aqueuse, elle indique un coefficient d'autodiffusion d'environ 5,6. 10−6 cm2 s−1, legerement inferieur a celui mentionne dans la litterature. Summary: A rapid measurement of atrazine diffusion coefficients in aqueous solutions A method is outlined for measuring diffusion coefficients. Its use is simple and does not require radioactive labelling. Applied to atrazine in aqueous solutions, it leads to a coefficient of self-diffusion in the order of 5–6. 10−6 cm2 s−1, slightly less than has been indicated up to now. Zusammenfassung Zur Schnellen Bestimmung von Atrazin Diffusionskoeffizienten in wassriger Losung Eine Methode wird beschrieben, um DiffusionskoefRzienten zu messcn. Ihre Anwendung ist einfach und braucht keine radioaktive Molekule. Fur Atrazin in wassriger Losung leitet diese Mehtode zu einem Werte von 5, 6. 10−6 cm2 s−1, etwa weniger als bisher bekannt.

Resume: L' effet du pH sur l'adsorption de la terbutryne par des acides humiques, une montmorillonite-Ca ou leurs melanges montre une certaine similitude de comportement entre ces derniers et l'argile seule. Au voisinage de la neutralite, seuls les acides humiques adsorbent la terbutryne. En milieu acide, les isothermes d'adsorption de la terbutryne par les acides humiques et la montmorillonite sont respectivement de type L et S et traduisent une affinite adsorbat-adsorbant differente; les isothermes d'adsorption correspondant aux melanges ont une forme differente et font apparaitre un effet de synergie, en particulier dans le cas des melanges pauvres en acides humiques. La dsorption saccompagne d'un phenomene d'hysteresis lieA a la presence des acides humiques. Les proprietes particulieres des associations argiles-matieres organiques sont susceptibles de mieux expliquer l'effet des sols sur l'activite des herbicides.

Resume En fractionnant prealablement deux substrats organiques (une paille de ble et im fpom de luzerne broyes) nous avons tente d'evaluer le pouvoir adsorbant, dans le sol, de leurs composants (substances hydrosolubles et lipidiques, heicelluloses, cellulose et lignine). La terbutryne et le diuron n'ont pas la meme affinite pour les composants des substrats. La lignine est plus adsorbante que les autres composants. Auregard de l'adsorption, les composants isoles constituent des classes heterogenes et interagissent. Par suite il apparait difficile de decrore le pouvoir adsorbant des matieres organiques non decomposees a partir de leur composition. La mineralisation, en modifiant la composition des substrats pourrait expliquer au moins partiellement les variations du pouvoir adsorbant des residus carbones provenant de la decomposition des substrats dans le sol. Summary Effect of orgunic matter added to soil on the adsrption of herhicides. Inffneuce of the composition of the organic matter By preliminary fractionation of two organic substrates (a wheat straw and a crushed lucerne hay) we tried to evaluate the adsorption capacity of their constituents (water-soluble and lipidic substances, hemicelluloses, cellulose and lignin) in soil. Terbutryne and diuron have different affinities with the constituents of the substrates. Lignin is more adsorbent than the other constituents. With regard to adsorption, isolated constitucents form heterogeneous and interacting classes. Consequently it is difficult to define the absorption capacity of non-decomposed organic materials on the basis of their composition. Mineralization, by modifying the composition, the variations in adsorptive power of carbon residues resulting from decomposition of the substrates in the soil. Zusammenfassung Effekte des dem Bodem heigefugten Ilumus auf llerbizidsorption. Einfluss der Zusammensetzung des Humus Durch Vorfraktionierung zweier organischen Substraten (eines Getreidestrohs und eines zermalmten Luzernheus) wurde die Adsorptionsfahigkeit ihrer Bestandteile (wasserlosliche und Lipoidsubstanzen. Jemozellulosen. Zellulosen und Lignin) im Boden ausgewertet. Terbutryn und Diuron zeigen verschiedliche Affinitaten gegenuber den Substratsbestandteilen. Lignin zeigt mehr Adsorptionsvermogen als die anderen Bestandteile. Was die Adsorption betrifft, bilden die abgetrennten Bestandteile heterogenc und wechselwirkende Klassen. Deshalb ist es schwierig die Adsorptionsfahigkeit unzersetzter organischer Stoffe auf Grund ihrer Zusammensetzung zu bestimmen. Die Mineralisierung, indem sie die Zusammensctzung der Substraten verandert. konnte die Schwankungen in der Fahigkeit aus der Zersetzung der Substraten entstehende Kohlstoffruckstande zu adsorbieren teilweise erklaren.

Summary: The detection and estimatinn of herbicides uith ihe aid of Chtorelta: investigation of optimum conditions and iheir applicalion to the analysis of several herbicides The use of a uniform culture of Chlorella as yn inoculum at a given density under known conditions of temperature, light and nutrition in a gaseous mixture has allowed an improvement in the technique and given highly reproducible results. Tests with atrazine have shown that it can be detected at a dose or 0.012 ppm and estimated to an accuracy of 0.04 ppm. Other herbicides have been tested and their sensitivity was found to be in lhe following descending order: lerbutryne > lenacil = isoproturon > atrazine > chlortoluron > methabenzthiazuron = metoxuron.

Summary A study was made of hydrodynamic dispersion in columns of pumice particles of different equivalent diameters and over a range of flow velocities. Dispersion is described by the first and second order moments of the elution curves. Two models are used to give a numerical analysis of the dispersion: a model using an apparent hydrodynamic dispersion coefficient and one using mixing cells with exchange (MCE). The part played by the stationary phase is described, and the molecular diffusion coefficient within the porous particles is calculated.

Composting is a process of biological treatment of organic wastes which reproduces the natural process of organic matter humification in soil. Today in France, only 7 % of the urban wastes are composted, although the organic part represents 50 % of the 47 million tons produced annually. Composts are mainly used in agriculture to increase or to maintain soil organic matter concentration. Their behavior after soil incorporation depends on the stability of their organic matter (OM). In this work, we studied the evolution of compost OM characteristics during composting, in relation with their origin (nature of the composted wastes and process of composting) and evaluated the potential storage of OM in soil with their use. The relation between the residual biodegradability of compost OM and the potential availability of nitrogen in soil was also studied. Ten urban composts made from municipal solid wastes, biowastes, green wastes or sewage sludge, coming from industrial composting plants were sampled after three, four and six months of composting. To avoid the influence of composting process, eight composts elaborated in laboratory reactors from variable proportions of green wastes, biowastes, and papers-cardboards, were followed during three months. A range of five classes of compost OM stability was defined on the basis of mineralization kinetics of compost carbon during incubations in a reference soil. Compost OM was characterized by chemical (humic substances) and biochemical (lignin, cellulose, hemicellulose and soluble fraction) fractionation and by analysis in infrared spectrometry (FTIR). The degree of compost maturity was defined from the level of compost OM stability and the range of stability previously defined was used as reference for the validation of various indicators of maturity. During the composting process, all composts evolved towards products with similar characteristics and independent from the composted waste and process that only influenced the rates of stabilization. In most cases, the cellulose fraction rapidly decreased when nitrogen was not limiting. The slower degradation of lignin as compared to total organic matter led to its relative enrichment in compost OM. The IR spectra confirmed the increase of aromaticity during composting. When greenwastes were dominant in the composted wastes, their initial high lignin concentration explained the fast stabilization of OM during composting and little evolution was observed between three and six months of composting. On the contrary, composts made from municipal solid wastes, initially richer in cellulose materials (papers-cardboards) with a relative lack of nitrogen, were not stabilised after three months of composting, and required at least six months of composting, with turning, to be stabilized. The influence of biowastes on compost OM stabilization was not pointed out, probably because they only represent a weak proportion of the dry mass of the initial mixtures. From the biochemical fractionation results, an indicator of the proportion of stable OM in compost was calculated (Biological Stability Index, BSI). This stable fraction of compost OM contributes to soil OM upkeep or increase after compost application. For greenwaste composts, BSI little increased during maturation and the simultaneous decrease of total compost OM made lightly decreased their efficiency to soil OM upkeep. The reverse was observed for municipal solid waste composts. Their important stabilization during maturation made increase their BSI. Of this important stabilization resulted a relative increase of their efficiency for soil OM upkeeping between three and six months of composting. A small potential availability of compost nitrogen was estimated from incubations of soil-compost mixtures. The organic fraction of nitrogen of stabilized compost mineralized slowly. On the contrary, a strong immobilization of soil nitrogen occurred after incorporation of unstable compost, followed by a faster mineralization than observed with stable compost. Among the tested indicators of maturity, the humification ratio (RH=CHA / CFA) was the more reliable chemical indicator. RH values smaller than 1 indicated a lack of maturity, and RH larger than 1.3 corresponded to stabilized composts with high maturity levels. The self-heating test was the most relevant to be used on composting platforms. These two indicators allowed a correct estimation of compost OM stabilization level, from which recommendations could be made on the optimal period for soil incorporation, taking into account the risks of nitrogen immoblization.; Le compostage est un procédé de traitement et de valorisation des déchets organiques qui reproduit en accéléré le processus d'humification de la matière organique (Mo) dans les sols. Actuellement en France, seulement 7 % des déchets urbains sont compostés, alors que la part organique représente 50 % des 47 millions de tonnes produites annuellement. Les composts sont avant tout utilisés en agriculture pour augmenter ou entretenir les teneurs en MO des sols, et le niveau de stabilité de leur MO conditionne leur comportement après incorporation au sol. Notre projet se proposait d'étudier l'évolution des caractéristiques de la MO de composts au cours du compostage, en la reliant à leur origine (nature des déchets compostés et procédé de compostage), et d'en déduire leur aptitude à entretenir le stock de MO d'un sol (valeur amendante). Les conséquences de la biodégradabilité résiduelle des composts sur la disponibilité potentielle de l'azote ont été également étudiées. Une dizaine de composts issus de plates-formes de compostage industrielles, comprenant des composts de déchets verts. des co-composts de déchets verts et boues, des composts de biodéchets (fraction fermentescible des ordures ménagères collectée sélectivement), et des composts d'ordures ménagères résiduelles (après collecte sélective des emballages propres et secs), ont été échantillonnés après trois, quatre et six mois de compostage. Afin de s'affranchir de la variable procédé de compostage, des composts ont également été élaborés en réacteurs de laboratoire à partir d'un procédé unique de compostage d'une durée de 3 mois et des proportions variables de déchets verts, biodéchets, et papiers-cartons. Une gamme de cinq classes de stabilité de la MO des composts a été définie sur la base de la minéralisation résiduelle du carbone des composts étudiés au cours d'incubations dans un sol de référence. La caractérisation de la Mo des composts a été réalisée à partir de fractionnement chimique (extraction des acides humiques et fulviques) et biochimique (composition en lignine, cellulose, hémicellulose, substances solubles), et par analyse en spectrométrie infrarouge à transformée de Fourier (IRTF), et a permis d'interpréter les différences de vitesse de stabilisation. Le degré de maturité étant défini par le niveau de stabilisation de la MO des composts, le classement de stabilité défini précédemment a servi de référence pour la validation d'indicateurs de maturité. Au cours du compostage, les composts évoluent vers des produits aux caractéristiques de plus en plus proches, indépendantes de leur origine, mais les vitesses de stabilisation dépendent de l'origine des composts. On observe généralement une disparition rapide de la cellulose quand l'azote n'est pas facteur limitant. La dégradation plus lente de la lignine par rapport à la MO totale conduit à son enrichissement relatif au cours du compostage. Les mesures IRTF confirment l'augmentation du rapport d'aromaticité au cours du compostage. La prédominance dans les déchets initiaux, de déchets verts par nature riches en lignine, entraîne la stabilisation rapide de la MO des composts, que le procédé soit accéléré ou non. Les caractéristiques de la MO de ces composts évoluent peu entre trois et six mois de compostage. A l'opposé, la prédominance dans les déchets initiaux, de papiers par nature riches en cellulose, requiert une durée de compostage plus longue pour arriver à des composts stabilisés, sans doute en raison d'un déficit en azote. De ce fait, les composts d'ordures ménagères, plus riches en papiers -cartons, sont encore instables au bout de trois mois, et nécessitent au moins six mois de compostage, avec retournements réguliers, pour se stabiliser. L'influence des biodéchets sur la vitesse de stabilisation des composts n'a pas pu être mise en évidence, car ils ne représentent qu'une faible proportion de la masse sèche des mélanges initiaux. A partir du fractionnement biochimique, on définit l'indice de stabilité biologique (ISB) des composts, indicateur de la proportion de matière organique susceptible d'entretenir la MO des sols. Pour les composts de déchets verts, la faible augmentation de leur ISB couplée à la minéralisation de leur MO au cours du compostage, se traduit par une légère diminution de leur valeur amendante en fin de compostage. En revanche, l'importante stabilisation de la MO des composts d'ordures ménagères au cours du compostage entraîne une augmentation de leur valeur amendante entre trois et six mois qui reste toutefois plus faible que celle des composts de déchets verts. La biodisponibilité potentielle de l'azote des composts, évaluée à partir d'incubations de mélanges sol-compost apparaît faible. L'azote des composts stabilisés se minéralise lentement. L'incorporation au sol des composts instables provoque une forte immobilisation de l'azote du sol, suivi d'une phase de minéralisation à des vitesses supérieures à celles observées avec les composts stables. Parmi les indicateurs de maturité étudiés, le rapport d'humidification (RH=CAH/CAF) est le seul indicateur chimique fiable, un RH inférieur à 1 désignant un degré de maturité faible, et un RH supérieur à 1.3 désignant un degré de maturité élevé. Le test d'auto-échauffement est le test de terrain le plus pertinent. Ces deux indicateurs permettent d'évaluer de façon fiable le degré de stabilisation des composts, et d'en déduire des conseils sur leur période d'apport, en tenant compte des risques d'immobilisation de l'azote dans les sols liés à leur utilisation