Variation of trace element accumulation by iron-manganese nodules from Dystric Cambisols with and without contamination

Abstract

The aim of this study was to characterize the influence of soil contamination on the trace element accumulation in nodules, inter-element relationships inside the nodules, and mobility of trace elements incorporated in nodules. We collected nodules sized 2–4 mm from pollution-free areas and areas significantly contaminated by Pb, Cd, and Zn with Dystric Cambisols on the west coast of the Pacific Ocean and studied them using a combination of advanced analytical methods and noninvasive techniques. The accumulation of trace elements by nodules was accompanied by a decrease of element mobility compared to surrounding soils. Nodules from uncontaminated soils can be highlighted as follows: (1) significant enrichment by Co and moderate enrichment by Ni, Cu, and Pb in the absence of Zn and Cd accumulation; (2) the strong affinities of Co and Cu towards Mn, association of Pb and Ni with both Mn and Fe; and (3) higher levels of Mn accumulation than in the nodules from contaminated soils. The main peculiarities of the nodules from contaminated soils were the increase in accumulation levels of Fe, Pb, Zn, and Cd, with the exception of Co; elements that were bound to Fe predominantly; and an increased trace element mobility compared to the nodules from the uncontaminated field. Nodules of two experimental fields had different composition of iron minerals. Iron-Mn nodules act as barriers that limit the input of elements in soil solution. Increases in the Fe-containing compounds (both pedogenic and anthropogenic origin) in nodules enhanced the trace elements removed from the host-contaminated soils.