Novel diffusive gradients in thin films technique to assess labile sulfate in soil.

Ondrej Hanousek,Sean Mason,Torsten W. Berger,Thomas Prohaska,Jakob Santner,Md Mobaroqul Ahsan Chowdhury

doi:10.1007/s00216-016-9801-8

Abstract

A novel diffusive gradients in thin films (DGT) technique for sampling labile soil sulfate was developed, based on a strong basic anion exchange resin (Amberlite IRA-400) for sulfate immobilization on the binding gel. For reducing the sulfate background on the resin gels, photopolymerization was applied instead of ammonium persulfate-induced polymerization. Agarose cross-linked polyacrylamide (APA) hydrogels were used as diffusive layer. The sulfate diffusion coefficient in APA gel was determined as 9.83 × 10−6 ± 0.35 × 10-6 cm2 s−1 at 25 °C. The accumulated sulfate was eluted in 1 mol L−1 HNO3 with a recovery of 90.9 ± 1.6 %. The developed method was tested against two standard extraction methods for soil sulfate measurement. The obtained low correlation coefficients indicate that DGT and conventional soil test methods assess differential soil sulfate pools, rendering DGT a potentially important tool for measuring labile soil sulfate.

Highlights

Sulfur (S) is a plant macronutrient as part of e.g. amino acids, proteins, and coenzymes
We present a novel Diffusive gradients in thin films (DGT) technique for the sampling of labile soil SO42−
The background S signals measured in the eluent (1 mol L−1 HNO3), in eluates of the acid-washed membrane, and of the diffusive gel were below the instrument limit of detection of ICP-MS

Summary

Introduction

Sulfur (S) is a plant macronutrient as part of e.g. amino acids, proteins, and coenzymes. It is involved in the plant metabolism as well as in the response to oxidative stress [1]. Common agricultural S testing methods include the KCl-40 test, which uses 0.25 mol L−1 KCl as an extractant [6]. This method was proposed to be more representative for plantavailable soil S than the MCP-S method (using 0.01 mol L−1 Ca(H2PO4)2), as KCl-40 provides a measure of adsorbed and soluble SO42−, including gypsum

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Conclusion