Mario Businelli

Characterization of Spatial Variability Structure in Three Separate Field Trials on Pesticide Dissipation

Experiments were carried out on three Italian farms to assess the degree of spatial variation of pesticide -eld concentration during treatment and during dissipation trials. Test pesticides were chloridazon and metamitron (both sugar-beet herbicides) applied as a tank mix. The classical statistical technique and geostatistics were used to summarize and evaluate variable spatial data. The results show that the actual values of pesticide concentration for applica- tion rate and initial concentration in all three areas are lower than expected, thus indicating that under -eld conditions only a part of the pesticide reaches the soil during the distribution. The actual values for both herbicides in all three areas expressed as percentage of expected values ranged from 44E1% to 64E2% for application rate and from 40E5% to 99E5% for initial concentration. The coeffi- cient of variation was similar for both pesticides and ranged from 23E 8t o 74 E1 for application rate, 24E1 and 58E8 for initial concentration and 11E1 and 110E0 for dissipation half-lives. The high variability in application rate and initial concen- tration could be ascribed to an uneven herbicide distribution, and in dissipation studies to variation in half-lives for the rate of herbicide loss from soil in di†erent parts of the -eld. Geostatistic analysis indicated little spatial correlation, probably because the sampling sites were widely spaced on the -eld. In all cases, the data were not sufficient to estimate the range of inNuence, probably because of the size of the experimental -elds and the sampling strategy.

Complexation capacity of dissolved organic matter from pig slurry: a gel filtration and dialysis study

The purpose of this research was to evaluate the apparent molecular weight distribution of dissolved organic matter (DOM) from pig slurry and the binding ability of its fractions toward copper (Cu2+) ions. In addition, the binding ability (maximum complexing capacity – MCC) of the DOM was compared with that of humic (HA) and fulvic (FA) acids from a clay-loam soil. The study was performed using Cu2+ ions since this metal is widely used as a supplement in pig diets and, consequently, is present in pig slurry. The techniques adopted were gel filtration chromatography (GFC) and dialysis. GFC showed that the DOM from pig slurry is mainly composed of a fraction with an apparent molecular weight higher than 5000 Da and the copper naturally present in the slurry is completely complexed by this fraction. The dialysis procedure enabled MCC to be determined. The MCC of pig slurry DOM and soil HA, which contained a similar concentration of carboxylic groups, were analogous, while MCC of soil FA, which contained double the concentration of carboxylic groups, was higher.

Transport to ground-water of six commonly used herbicides: a prediction for two Italian scenarios

In Italy suitable standard scenarios for pesticide risk assessment based on computer models are lacking. In this paper we examine the use of the VARLEACH model to assess the potential danger of ground-water pollution by six herbicides (alachlor, atrazine, cyanazine, linuron, simazine and terbuthylazine) which are used to protect irrigated (maize) and non-irrigated (sorghum) crops in the Po Plain, one of the most important agricultural lands in Italy. Two extreme scenarios are taken: real worst case (sandy soil) and real best case (clay loam soil). The simulation suggests that cyanazine, linuron and terbuthylazine can be safely used in clay loam soil in both non-irrigated and irrigated crops, while alachlor, atrazine and simazine can be safely used only in non-irrigated crops. On the other hand, the application of all the herbicides tested should be avoided in sandy soil, with the exception of linuron in non-irrigated crops. © 2000 Society of Chemical Industry

An analytical method for the determination of fluazifop-butyl and fluazifop residues in soil

A method is described for the analysis of soils for residues of the herbicide fluazifop-butyl and its breakdown product fluazifop. Fluazifop-butyl undergoes hydrolysis in the soil to fluazifop, which also has herbicidal activity. A procedure initially using dichloromethane and then methanol+aqueous sodium hydroxide for extraction has been developed and gives good recoveries of both fluazifop-butyl and fluazifop in the 0.01–5 mg kg−1 range. After clean-up, high-performance liquid chromatography with u.v. detection at 245 nm or gas-chromatography with mass framentography were used to determine the residue concentrations. The limit of detection was 0.05 mg kg−1 when h.p.l.c. was used and 0.01 mg kg−1 when g.c.-m.s. was used.

Evaluation of a simulation model for prediction of chlorsulfuron fate in an Umbrian soil

A mathematical model described by Nicholls et al. (Pestic. Sci., 12 (1982) 484-494) has been used to simulate the movement and the degradation of chlorsulfuron in an Umbrian soil, following application to the soil surface in autumn. Experiments were also performed on soil columns that had been surface-treated with chlorsulfuron and irrigated daily with water doses corresponding to the pluviometric records

XAS study of lead speciation in a central Italy calcareous soil

Purpose The Pb absorption processes on a heavy textured calcareous soil, typical of central Italy, were studied using synchrotron X-ray absorption spectroscopy (XAS) in order to probe, at molecular scale, the structure and chemical nature of Pb in contaminated soils and achieve precise description of Pb ions localization into these contaminated soils.Materials and methods In order to distinguish the role of the different components of soils in Pb retention, samples were prepared from the original soils removing the carbonate fractions, the organic matter, the metal oxides, or selecting the clay fractions. Then these samples were fortified with Pb simulating the natural interactions processes of heavy metal solutions with soils. The quantitative analysis of near edge (XANES) as well extended (EXAFS) regions of Pb LIII edge absorption spectra, in comparison with Pb XAS data of selected reference compounds, allowed the precise determination of local structure and chemical environment of Pb ions in these soil samples.Results Four components were individuated as the major responsible of Pb retention in calcareous soils: the carbonates, the metal oxide surfaces, the organic matter, and the colloidal inorganic surfaces containing clay components. The structural analysis suggests that, within these experimental conditions, the Pb adsorbed on the soil is generally present as Pb hydroxide with poor crystallization degree. However, the presence of carbonates (CaCO3) induces the co-precipitation of PbCO3-like phases with some degree of crystallinity.