International audienceThe intensive use for over 100 yr of copper sulfate (Bordeaux mixt.) to fight mildew in vineyards has led to a substantial accumulation of copper (Cu) in surface soils. To assess the effects of such large concns., the surface soils of 10 Burgundy vineyards were sampled and analyzed for total org. matter (carbon and nitrogen) and metal (copper and iron) contents. Phys. (i.e. size fractionation) and chem. (sequential extn.) methods were used to det. the distribution of these elements. The most Cu-​contaminated plots showed the largest accumulation of org. carbon and Cu in the coarse sand and fine sand fractions. Copper was strongly correlated with org. carbon and org. nitrogen in the coarse sand fraction and with org. nitrogen in the fine sand fraction. Copper was also highly correlated with both Fe and org. nitrogen in the clay fraction but not significantly with org. carbon. The sequential extn. showed that Cu was bound mainly to the Fe oxides. However, in the most Cu-​contaminated plots, a part of added Cu was bound to org. matter. Apparently, Cu protected indirectly the org. matter present in the coarse fractions against biodegrdn., and therefore modified the distribution of org. carbon among the particle-​size fractions. Iron appeared as the main factor responsible for Cu accumulation in the clay fraction, mainly through inclusion of Cu in Fe oxyhydroxides and possibly in clay-​humus complexes

The electroanalytical technique Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) has been extended by applying stripping chronopotentiometry (SCP) as the re-oxidation stage in the determination of the free concentration of Zn(2+), Cd(2+) and Pb(2+). This new approach, called AGNES-SCP, has been implemented with screen-printed electrodes (SPE) and the standard Hanging Mercury Drop Electrode (HMDE). Clear advantages of this variant have been shown: (i) the easy resolution of the peaks of different metals present in mixtures and (ii) the sparing of blanks. A rigorous computation of the faradaic charge along the SCP stage takes into account the contribution of other oxidants, which can be efficiently measured at the end of the deposition stage of AGNES. The free Cd concentration determined in an oxalate solution at pH 6 with an HMDE as the working electrode agreed well with values obtained with a Cd Ion Selective Electrode. The free metal concentration measured using an SPE for the system Cd and nitrilotriacetic acid (NTA) at pH = 4.8 also conformed well with Visual MINTEQ results.

AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) has been implemented with screen-printed electrodes (SPE) for the determination of the free concentration of Zn 2 + , Cd 2 + and Pb 2 + . For SPE, the stripped charge is a suitable response function which does not require the second stage of AGNES to be under diffusion limited conditions. This property can be used in the avoiding of the interference of Pb on [Cd 2 + ] determination. The proportionality factor between stripped charge and concentration of amalgamated metal depends on the volume of mercury and opens the way to a future calibrationless strategy. Zn and Cd complexation with oxalate at various pH-values confirms the suitability of the developed methodology, which compares favourable with the standard one based on the Hanging Mercury Drop Electrode.