Polycyclic aromatic hydrocarbons (PAHs) are possible contaminants in some former industrial sites, representing a potential risk to human health if these sites are converted to residential areas. This work was conducted to determine whether PAHs present in contaminated soils are transferred to edible parts of selected vegetables. Soils were sampled from a former gasworks and a private garden, exhibiting a range of PAH concentrations (4 to 53 to 172 to 1263 and 2526 mg PAHs kg-1 of dry soil), and pot experiments were conducted in a greenhouse with lettuce (Lactuca sativa L. var. Reine de Mai), potato (Solanum tuberosum L. var. Belle de Fontenay), and carrot (Daucus carota L. var. Nantaise). At harvest, above- and below ground biomass were determined and the PAH concentrations in soil were measured. In parallel, plates were placed in the greenhouse to estimate the average PAH-dust deposition. Results showed that the presence of PAHs in soils had no detrimental effect on plant growth. Polycyclic aromatic hydrocarbons were detected in all plants grown in contaminated soils. However, their concentration was low compared with the initial soil concentration, and the bioconcentration factors were low (i.e., ranging from 13.4 x 10(-4) in potato and carrot pulp to 2 x 10(-2) in potato and carrot leaves). Except in peeled potatoes, the PAH concentration in vegetables increased with the PAH concentration in soils. The PAH distribution profiles in plant tissues and in soils suggested that root uptake was the main pathway for high molecular weight PAHs. On the opposite, lower molecular weight PAHs were probably taken up from the atmosphere through the leaves as well as by roots.

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Previous sorption/desorption batch experiments have indicated that bentazone is weakly sorbed by soils. In addition, field experiments have shown that 4% of the bentazone sprayed can be leached to drainage water. In order to complete bentazone characterisation, we have assessed the effect of time on its behaviour in contrasting soils. In laboratory studies, bentazone was added to three topsoils (sandy, loamy and clay soils). Bentazone degradation, sorption/desorption kinetics and isotherm measurements were carried out at different times. At 160 days after treatment, bentazone mineralisation amounts varied from 2.1% (sandy soil) to 14% (clay soil). The extractable amounts became lower (from 97% after treatment to 12% after 160 days for the clay soil) and a greater number of desorption series was needed to obtain these products. Nevertheless, at the end of the experiments, a small amount of bentazone was still extracted by water. At the same time, bound residues of bentazone reached 65% in clay soil. Statistical analysis indicated effects of both residence time and soil type on bentazone behaviour.

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-We investigated sulcotrione degradation in a sandy-silty brown soil. The agricultural field was divided into three small plots ten years ago, named plots R for reference, M for manure and CM for compost manure. The degradation experiment was conducted under controlled laboratory conditions using 14 C benzene uniformly ring-labelled sulcotrione. In the first month of the experiment, 80% of the residues was extractable with solvent, 55% of sulcotrione was degraded, including 45% into 2-chloro-4-methylsulfonylbenzoïc acid (CMBA), the most abundant metabolite of sulcotrione. 10% of the residues was mineralised. After two months, 40% of the residues was extractable, including 16% of sulcotrione, 25% was mineralised and 35% formed non-extractable residues. Soil amended with different organic matters favoured transformation of sulcotrione in soil. The fresh manure amendment activated mineralisation of 10%, and the compost manure amendment induced a lower ratio of extractable sulcotrione at a level of 5%.sulcotrione / degradation / persistence / soil / organic amendments / mineralisation Résumé -Dégradation de la sulcotrione dans un sol brun amendé avec différents apports organiques. La dégradation de la sulcotrione dans le sol a été évaluée en conditions de laboratoire à l'aide de la molécule uniformément marquée au 14 C sur le noyau benzénique. Le sol utilisé présente une texture limono-sableuse et est issu d'une parcelle divisée en trois sous parcelles recevant différents apports organiques depuis dix ans. Les terres issues de ces trois sous parcelles sont nommées respectivement terre R (référence), M (fumier) et CM (fumier composté). Lors du premier mois d'expérimentation 80 % des résidus restent extractibles, 55 % de la sulcotrione est dégradée dont 45 % en CMBA (2-chloro-4-methylsulfonylbenzoïc acide) son métabolite majeur. Seul 10 % des résidus sont minéralisés. Au bout de deux mois, 40 % des résidus sont extractibles au solvant dont 16 % de sulcotrione, 25 % sont minéralisés et 35 % forment des résidus non-extractibles. Lors d'amendements organiques, la transformation de la sulcotrione dans le sol est favorisée. L'apport de fumier active de 10 % la minéralisation des résidus et l'apport de fumier composté induit un ratio de sulcotrione extractible faible de l'ordre de 5 %.sulcotrione / dégradation / persistance / sol / amendement organique / minéralisation

A soil column experiment under outdoor conditions was performed to monitor the fate of 14C-ring-labelled sulcotrione, 2-(2-chloro-4-mesylbenzoyl)cyclohexane-1,3-dione and atrazine, 6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine, in water leachates and in the ploughed horizon of a sandy loam soil. Two months after treatment, the cumulative amounts of herbicide residues leached from the soil were 14.5% and 7% of the applied radioactivity for sulcotrione and atrazine, respectively. Maximum leachate concentrations for each herbicide were observed during the first month following application: 120 and 95 microg litre(-1) for sulcotrione and atrazine respectively. After 2 weeks, 78% of the sulcotrione and atrazine was extractable from the soil, whereas after two months only 10 and 4%, respectively, could be extracted. The maximum sulcotrione content in the first 10 cm of soil was identical with that of atrazine. For both molecules, the content of non-extractable residues was low, being around 15%. Sulcotrione seems to be more mobile than atrazine but the consequences for water contamination are similar since lower doses are used.

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