Dynamics of plant metal uptake and metal changes in whole soil and soil particle fractions during repeated phytoextraction

Abstract

Aims Phytoextration of metal polluted soils using hyperaccumulators is a promising technology but requires long term successive cropping. This study investigated the dynamics of plant metal uptake and changes in soil metals over a long remediation time. Methods A soil slightly polluted with metals (S1) was mixed with highly polluted soil (S4) to give two intermediate pollution levels (S2, S3). The four resulting soils were repeatedly phyto-extracted using nine successive crops of Cd/Zn-hyperaccumulator Sedum plumbizincicola over a period of 4 years.Results Shoot Cd concentration decreased with harvest time in all soils but shoot Zn declined in S1 only. Similar shoot Zn concentrations were found in S2, S3 and S4 although these soils differed markedly in metal availability, and their available metals decreased during phytoextraction. A possible explanation is that plant active acquisition ability served to maintain plant metal uptake. Plant uptake resulted in the largest decrease in the acid-soluble metal fraction followed by reducible metals. Oxidisable and residual fractions were less available to plants. The coarse soil particle fractions made the major contribution to metal decline overall than the fine fractions. Conclusion Sedum plumbizincicola maintained long term metal uptake and the coarse soil particles played the most important role in phytoextraction.

Elemental distribution by cryo-micro-PIXE in the zinc and cadmium hyperaccumulator Sedum plumbizincicola grown naturally

“…The concentrations in shoots reach a "saturation level" that does not show strong correlation with the concentrations in soil. A similar phenomenon was observed in that Cd and Zn concentrations in the shoots of S. plumbizincicola did not decrease although soil total and available metal concentrations decreased largely at the later stages of repeated phytoextraction (Li et al 2014). In hydroponics experiments 25 and 50 μmol L −1 Cd treatments did not induce significant differences in Cd concentrations in shoots, only in roots.…”

“…During the last two decades there has been a growing interest in metal-hyperaccumulating plants due to their unique physiology of metal tolerance and accumulation as well as their potential for phytoremediation applications (Baker et al 1994;McGrath et al 2006;Li et al 2014). Quantitative studies on the distribution of metals within plant tissues are important for understanding plant metabolism and the mechanisms of metal tolerance and hyperaccumulation.…”

Chemical Fractions and Availability of Zinc in Winter Wheat Soil in Response to Nitrogen and Zinc Combinations

“… Sungur et al (2014) noted that plants can mainly take up Zn in the exchangeable and carbonate-bound fractions. Li et al (2014) showed that exchangeable and organic matter-bound Zn in contaminated soil declined significantly after phytoextraction, which further indicates that the exchangeable and organic matter-bound fractions were more available to the plants than the other fractions. The availability of Zn in soil increased with the enhanced transformation of Zn from tight organic matter-bound to light organic matter-bound ( Li et al, 2006 ).…”

Distance-dependent varieties of microbial community structure and metabolic functions in the rhizosphere of Sedum alfredii Hance during phytoextraction of a cadmium-contaminated soil

“…The metals extracted at the first step were considered as the most available forms (Chlopecka 1996). The decrease of these forms of Cd in the rhizosphere of hyperaccumulators was frequently reported, such as Thlaspi caerulescens (Puschenreiter et al 2003;Dessureault-Rompre et al 2010) and Sedum plumbizincicola (Liu et al 2011;Li et al 2014). In rhizospheric soil, the concentrations of metals rely on the balance between those released from soil and its uptake by plants.…”