Biomedical subjects

Sylvie Dousset

Publications and source records attributed to Sylvie Dousset.

6 recordsLinked to original sources

PubMed2005

Leaching of oryzalin and diuron through undisturbed vineyard soil columns under outdoor conditions.

Field studies monitoring herbicide pollution in the vineyards of Burgundy (France) have revealed that drinking water reservoirs are contaminated with several pre-emergence herbicides. An assessment of the leaching of two such herbicides, diuron and oryzalin, was therefore performed using lysimeters, under outdoor conditions, from May 2001 to May 2002. Four vineyard soils from Vosne-Romanée (Burgundy) were chosen along a topolithosequence: a rendosol and three calcosols. After 673 mm of rainfall, greater amounts of diuron than oryzalin were measured in percolates: respectively 0.10-0.84% and 0.02-0.43% of applied herbicide, depending on soils. Measurements for diuron metabolites detected greater amounts of DCPMU than DCPU in the percolates: respectively 0.05-0.13% and 0-0.04% of the applied diuron. At the end of the monitoring period, more residues of diuron than oryzalin were recovered in the soil profiles: respectively 4.6-9% and 1.4-4.4%. The oryzalin residues were found mainly in the upper 10 cm of soil columns, whereas diuron residues were present in the whole core. The mobility of both oryzalin and diuron seems fairly well-related to soil organic carbon content; the mobility of diuron is also related to soil texture (sand and coarse material contents). Under such experimental conditions, this study confirms that diuron leaching, and therefore potential groundwater contamination, is greater than that of oryzalin.

Agriculture↗

PubMed2005

Diuron mobility through vineyard soils contaminated with copper.

The herbicide diuron is frequently applied to vineyard soils in Burgundy, along with repeated treatments with Bordeaux mixture (a blend of copper sulfate and calcium hydroxide) that result in elevated copper concentrations. Cu could in principle affect the fate and transport of diuron or its metabolites in the soil either directly by complexation or indirectly by altering the populations or activity of microbes involved in their degradation. To assess the effect of high Cu concentrations on diuron transport, an experiment was designed with ten undisturbed columns of calcareous and acidic soils contaminated with 17--509 mg kg(-1) total Cu (field-applied). Grass was planted on three columns. Diuron was applied to the soils in early May and in-ground lysimeters were exposed to outdoor conditions until November. Less than 1.2% of the diuron applied was found in the leachates as diuron or its metabolites. Higher concentrations were found in the effluents from the grass-covered columns (0.1--0.45%) than from the bare-soil columns (0.02--0.14%), and they were correlated with increases in dissolved organic carbon. The highest amounts of herbicide were measured in acidic-soil column leachates (0.98--1.14%) due to the low clay and organic matter contents of these soils. Cu also leached more readily through the acidic soils (32.8--1042 microg) than in the calcareous soils (9.5--63.4 microg). Unlike in the leachates, the amount of diuron remaining in the soils at the end of the experiment was weakly related to the Cu concentrations in the soils.

Agriculture↗

PubMed2005

Leaching of glyphosate and AMPA under two soil management practices in Burgundy vineyards (Vosne-Romanée, 21-France).

Some drinking water reservoirs under the vineyards of Burgundy are contaminated with herbicides. Thus the effectiveness of alternative soil management practices, such as grass cover, for reducing the leaching of glyphosate and its metabolite, AMPA, through soils was studied. The leaching of both molecules was studied in structured soil columns under outdoor conditions for 1 year. The soil was managed under two vineyard soil practices: a chemically treated bare calcosol, and a vegetated calcosol. After 680 mm of rainfall, the vegetated calcosol leachates contained lower amounts of glyphosate and AMPA (0.02% and 0.03%, respectively) than the bare calcosol leachates (0.06% and 0.15%, respectively). No glyphosate and only low amounts of AMPA (<0.01%) were extracted from the soil. Glyphosate, and to a greater extent, AMPA, leach through the soils; thus, both molecules may be potential contaminants of groundwater. However, the alternative soil management practice of grass cover could reduce groundwater contamination by the pesticide.

Agriculture↗

PubMed2004

Laboratory leaching studies of oryzalin and diuron through three undisturbed vineyard soil columns.

The leaching of diuron and oryzalin through undisturbed soil columns was studied in the laboratory using three vineyard soils from Vosne-Romanée (Burgundy): a rendosol, a calcosol and a vegetated calcosol. After 845 mm of simulated rainfall in 15 days, soil leachates contained higher amounts of diuron (3.2%, 11.8% and 18.8% of applied diuron, respectively) than oryzalin (0.2%, 4.9%, 3.7%, respectively). A greater proportion of soil extractable residues was obtained for diuron (42.5%, 26.8% and 32.2%, respectively) than for oryzalin (14.7%, 12% and 15.5%, respectively). The greater mobility of diuron might be related to its higher water solubility (36.4 mgl(-1) compared with 2.6 mgl(-1) for oryzalin) and smaller adsorption coefficient (400 lkg(-1), compared with 700-1100 lkg(-1) for oryzalin). The mobility of the two herbicides was greater in the two calcosols than in the rendosol, not only due to different organic carbon contents but also different soil textures and structures.

Adsorption↗

PubMed2004

Microbial acidification and pH effects on trace element release from sewage sludge.

Leaching of sludge-borne trace elements has been observed in experimental and field studies. The role of microbial processes in the mobilization of trace elements from wastewater sludge is poorly defined. Our objectives were to determine trace element mobilization from sludge subjected to treatments representing microbial acidification, direct chemical acidification and no acidification, and to determine the readsorption potential of mobilized elements using calcareous sand. Triplicate columns (10-cm diameter) for incubation and leaching of sludge had a top layer of digested dewatered sludge (either untreated, acidified with H2SO4, or limed with CaCO3; all mixed with glass beads to prevent ponding) and a lower glass bead support bed. Glass beads in the sludge layer, support layer or both were replaced by calcareous sand in four treatments used for testing the readsorption potential of mobilized elements. Eight sequential 8-day incubation and leaching cycles were operated, each consisting of 7.6 d of incubation at 28 degrees C followed by 8 h of leaching with synthetic acid rain applied at 0.25 cm/h. Leachates were analyzed for trace elements, nitrate and pH, and sludge layer microbial respiration was measured. The largest trace element, nitrate and S losses occurred in treatments with the greatest pH depression and greatest microbial respiration rates. Cumulative leaching losses from both microbial acidification and direct acidification treatments were > 90% of Zn and 64-80% of Cu and Ni. Preventing acidification with sludge layer lime or sand restricted leaching for all trace elements except Mo. Results suggested that the primary microbial role in the rapid leaching of trace elements was acidification, with results from direct acidification being nearly identical to microbial acidification. Microbial activity in the presence of materials that prevented acidification mobilized far lower concentrations of trace elements, with the exception of Mo. Trace elements mobilized by acidification were readsorbed by calcareous sand when present.

Calcium↗

PubMed2003

Comparison of three sequential extraction procedures used to study trace metal distribution in an acidic sandy soil.

On an acid sandy soil contaminated with trace metals (Fe, Mn, Cu, Pb and Zn), three sequential extraction procedures were compared to determine the efficiency of the reagents used and the effects of the step order on the fractionation of metal species. In all cases, a magnesium nitrate solution (MgNIT) was previously used to extract exchangeable forms. In the first procedure (I), the next extraction step was performed with sodium acetate buffer (NaOAc), as used on calcareous soils, to dissolve active calcium carbonate. Then trace metals bound to different forms of oxi-hydroxides (NH(2)OH, TAMOx and TAMAs fractions) were extracted before organic matter/sulfide oxidation with hydrogen peroxide at pH 2.0 in nitric acid medium (OMHyd). Finally, residual bound metals (RESID) in each procedure were extracted with a nitric-hydrofluoric-perchloric acid mixture. The second procedure (II) was the same as I, but without the NaOAc step, because of the absence of carbonate in the study soil. In procedure III, the NaOAc step was omitted and the oxidizable organic/sulfide fraction was extracted with sodium hypochlorite at pH 8.5 (OMOCl) before the reducible fractions. This study first showed that NaOAc may remove considerable amounts of metals (especially Mn and Zn) in other forms than exchangeable ones. Procedures II and III give similar results for Fe, Mn and Zn forms, which were mainly found in fractions of inorganic soil components, but not for Cu and Pb. Copper distribution was affected by the position of the oxidation step in the sequence. In procedure II, where the oxidation step (OMHyd) ended the sequence, Cu was mainly recovered in the TAMOx fraction. However, in procedure III, where the oxidation step (OMOCl) preceded the NH(2)OH, TAMOx and TAMAs steps, Cu was found in both OMOCl and TAMOx fractions. Lead distribution varied with oxidation reagent: it was partly removed in the OMHyd fraction of procedures I and II, and to a much lower extent in the OMOCl fraction of procedure III, probably due to the alkaline pH of the reagent in the latter case.

Acids↗