Simultaneous measurement of multiple labile heavy metals in soils by diffusive gradients in thin film technique.

Purpose: Development of new binding gels for rapid and simultaneous quantification of bioavailability concentrations of various heavy metals in soils by diffusive gradients in thin film technique. Methods: Four binding gels including zinc-aluminum hydrogel (ZnAl-LDH), ethylenediaminetetraacetic acid intercalated zinc-aluminum hydrogel (ZnAl-EDTA-LDHs), polyglutamic acid (PGA), and polyglutamic acid–sodium alginate resin (SA-PGA) were prepared and used for the simultaneous measurement of Cr, Ni, Cu, Cd, and Pb. Results: The adsorption process reached equilibrium in 2 h, which could be considered a pseudo-second-order reaction. Three mol L⁻¹ nitric acid was the best eluent with elution efficiency over 91% for the five heavy metals. Then, SA-PGA gel was assembled into DGT device (SA-PGA-DGT). Its performance was virtually unaffected by pH (5–9), ionic strength (1–50 mM), and soil properties with adsorption capacities 5.02 μg cm⁻², 11.38 μg cm⁻², 8.16 μg cm⁻², 17.11 μg cm⁻², and 89.43 μg cm⁻² for Cr, Ni, Cu, Cd, and Pb, respectively. A good linear correlation was observed between the concentrations of Cr, Ni, Cu, Cd, and Pb determined by SA-PGA-DGT in soil samples from Tanggu District in China and the exchangeable contents of the five metals determined by the Tessier method, with R values of 0.64, 0.63, 0.59, 0.72, and 0.64 (p < 0.01). Conclusion: SA-PGA gel exhibited the best adsorption properties among the four gels. SA-PGA-DGT can be used as a reliable tool for rapid and simultaneous quantification of bioavailability concentrations of multiple heavy metals. [ABSTRACT FROM AUTHOR]