Measurements of trace metal species in situ in a softwater river, a hardwater lake, and a hardwater stream were compared to the equilibrium distribution of species calculated using two models, WHAM 6, incorporating humic ion binding model VI and visual MINTEQ incorporating NICA−Donnan. Diffusive gradients in thin films (DGT) and voltammetry at a gel integrated microelectrode (GIME) were used to estimate dynamic species that are both labile and mobile. The Donnan membrane technique (DMT) and hollow fiber permeation liquid membrane (HFPLM) were used to measure free ion activities. Predictions of dominant metal species using the two models agreed reasonably well, even when colloidal oxide components were considered. Concentrations derived using GIME were generally lower than those from DGT, consistent with calculations of the lability criteria that take into account the smaller time window available for the flux to GIME. Model predictions of free ion activities generally did not agree with measurements, highlighting the need for further work and difficulties in obtaining appropriate input data.

Several techniques for speciation analysis of Cu, Zn, Cd, Pb, and Ni are used in freshwater systems and compared with respect to their performance and to the metal species detected. The analytical techniques comprise the following:  (i) diffusion gradients in thin-film gels (DGT); (ii) gel integrated microelectrodes combined to voltammetric in situ profiling system (GIME−VIP); (iii) stripping chronopotentiometry (SCP); (iv) flow-through and hollow fiber permeation liquid membranes (FTPLM and HFPLM); (v) Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE−SV). All methods could be used both under hardwater and under softwater conditions, although in some cases problems with detection limits were encountered at the low total concentrations. The detected Cu, Cd, and Pb concentrations decreased in the order DGT ≥ GIME−VIP ≥ FTPLM ≥ HFPLM ≈ DMT (>CLE−SV for Cd), detected Zn decreased as DGT ≥ GIME−VIP and Ni as DGT > DMT, in agreement with the known dynamic features of these techniques. Techniques involving in situ measurements (GIME−VIP) or in situ exposure (DGT, DMT, and HFPLM) appear to be appropriate in avoiding artifacts which may occur during sampling and sample handling.

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It is widely known that the analysis of trace elements is tricky and that the results obtained often vary according to the analytical technique chosen.The aim of this paper is to compare different analytical techniques, a spectroscopic, an electrochemical and a chromatographic one to determine total heavy metals concentrations in soils and to establish a correlation between these three techniques even though soil solutions are complex matrices providing a lot of interference problems.Atomic emission spectroscopy is the method of reference for heavy metals concentrations analysis. This analytical technique is employed for multi-element analysis and is suitable for a routine measuring out [1]. Polarographic methods are commonly used because of their very low detection limits but still, they are time consuming. Ion chromatographic techniques are generally described in the literature for heavy metals analysis in simple matrix like water but no papers were found for complex matrices like soils or sediments.The first part of this paper presents the apparatus used and the analytical reagents. The second section describes the experimental results obtained with ion chromatography, anodic stripping voltammetry and atomic emission spectroscopy. The last section presents a discussion and a comparison of the results obtained with the different methods for each heavy metal studied. Materials and methods Ion ChromatographyThe measurements are carried out on a DIONEX DX 500 system which is composed of a peristaltic pump GP 40, a pre column CG5A, a CS5A column and a UV-Visible detector AD20. The CS5A column is compatible with pH 0 to 14, allowing the analysis of acid digested soil solutions. Two different Dionex eluents are used, the Met Pac PDCA and the Met Pac Oxalic Acid. The first one is a pyridine-2,6 dicarboxylic acid (PDCA) eluent which is a strong complexing agent that separates the metal ion complexes by anion exchange. The second one is an oxalic acid eluent which is a moderate strength complexing agent that separates the metals by a mixed mode mechanism, anion exchange for metals complexed with oxalic acid and cation exchange for free metals. The detection is accomplished by visible absorbance after post column complexation between heavy metals and a post column reagent. The post column reagent is prepared with 30 mg of 4- (2pyridylazo) Abstract. This work deals with the comparison between three analytical techniques for the total contents analysis of heavy metals in agricultural soils polluted by copper. The soils samples are digested to clear solutions using a mixture of perchloric and hydrofluoric acids. The metals studied are copper, lead, cadmium, nickel, cobalt, zinc and manganese. Soil solutions are complex matrices and the analytical techniques investigated are ion chromatography (IC), Anodic Stripping Voltammetry (ASV) or Adsorptive Stripping Voltammetry (AdSV) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), or graphite furnace atomic absorption spectroscopy (AAS). The use of ion chroma...