Determination of Labile Cadmium in Soils Using a New Sodium Alginate‐Polyglutamic Acid‐Diffusive Gradient in Thin Films

Abstract

Sodium alginate-polyglutamic acid was used to develop a new diffusive gradient in thin films (SA-PGA-DGT) device which was proved to be suitable for the investigation of labile Cd in soil. The adsorption capacity of Cd was calculated to be about 16.8 μg/cm 2 , which was hardly affected by factors including pH (5-9), ionic strength (0.1-100 mM), and the presence of other metals (Pb, Cu, Ni, and Cr). SA-PGA This article is protected by copyright. All rights reserved. Accepted Article gel has dense and uneven pores with large specific surface area, which ensures the adsorption of Cd by functional groups of the gel. Kinetics study indicated that the adsorption rate of Cd by the binding gel can be described as a pseudo-second order reaction. Deployment of the SA-PGA-DGT in the soils of Tang Gu (located in Binhai New District, Tianjin, China), showed a strong positive linear correlation between Cd measured by the device and exchangeable Cd measured by the Tessier method (R = 0.73, p < 0.01). Cd determined by the SA-PGA-DGT device was less affected by soil properties. This new SA-PGA-DGT has obvious advantages over other methods in respect of the labile Cd analysis in soil. The innovative novel device expands the variety of existing DGT technologies and can be utilized to monitor the level of labile Cd in soil effectively.