Cadmium and zinc accumulation by the hyperaccumulator Thlaspi caerulescens from soils enriched with insoluble metal compounds

Abstract

The clay mineralogy of seven Dystrandepts developed on basalts in Northland (New Zealand), the French Massif Central and Western Oregon (U.S.A.) was determined by selective dissolution—differential infrared spectroscopy in combination with chemical, X-ray diffrac tion, electron microscopic and thermogravimetric analyses. Of 14 soil samples, 6 from Northland and Cantal (French Massif Central) contained allophane and imogolite, whereas the remaining 8 did not. Allophane-like constituents and/or “alumina” were found in all the samples, and opaline silica was present in three A₁ horizons. The contents of 2 : 1–2 : 1 : 1 layer silicates and their intergrades varied somewhat among the samples. Predominant volcanic glass shards in the Northland Dystrandepts and quartz in the Western Oregon Dystrandepts indicated that their parent materials were not restricted to basalt.