Physiological Aspects of Absorption, Translocation, and Accumulation of Heavy Metals in Silphium perfoliatum L. Plants Grown in a Mining-Contaminated Soil

Vlad Nescu,Radu Liviu Sumalan,Sorin Ciulca,Renata Maria Sumalan,Giancarla Velicevici,Sorin Gaspar,Adina Berbecea,Petru Negrea

doi:10.3390/min12030334

Abstract

Soil pollution by heavy metals as a result of mining activities is increasingly taking place. Once accumulated in soil, the heavy metals can then be dispersed, with serious effects on the environment and human health. It is therefore necessary to minimize, or even remove, all heavy metals from polluted areas, and one of the environmentally friendly and sustainable methods to do so is phytoremediation. A greenhouse pots experiment was conducted to evaluate the phytoremediation capacity of Silphium perfoliatum L. plants, in the vegetative growth stages, on a soil polluted with Cu, Zn, Cr and Pb, taken from a former mining area compared to an unpolluted soil (Us). The initial heavy metal content of polluted soil (Ps) was 208.3 mg kg−1 Cu; 312.5 mg kg−1 Zn; 186.5 mg kg−1 Cr and 195.2 mg kg−1 Pb. This shows that for Cu and Pb, soil concentrations exceed the intervention threshold, and for Zn and Cr, they are above the alert threshold. The removal efficiency, bioaccumulation factor, translocation factor, metal uptake and contamination factor index of Cu, Zn, Cr and Pb by S. perfoliatum L. were quantified to determine the bioremediation success. The data show that plants grown in Ps accumulated a significantly higher amount of Cu by 189% and Zn by 37.95% compared to Us. The Cr and Pb content of the plants recorded a progressive and significant increase from one developmental stage to another, being more intense between three and five leaves.

Highlights

More than 10 million soil pollution sites have been identified worldwide, more than half of which are contaminated with heavy metals and/or metalloids [1]
According to the values of the contamination factor index (Cfi), much higher contamination with Cr, Cu, Zn and Pb was observed in polluted soil (Ps), and considerable contamination with Cu was observed in unpolluted soil (Us)
Phenophase showed a lower contribution to the variability of Pb and Cr content compared to plant organs

Summary

Introduction

More than 10 million soil pollution sites have been identified worldwide, more than half of which are contaminated with heavy metals and/or metalloids [1]. In the first few years after 1990, around 138 million tons of pollutants were emitted into the environment annually, including significant amounts of particles and compounds of non-ferrous metals with very harmful effects on the ecosystems. The causes of these pollution were primarily due to mismanagement, as well as outdated technologies and operating facilities. These accelerated developments have intensified and caused new industrial pollution phenomena, one of the most important being the pollution of the soil by heavy metals [13]. Pollution manifests itself in the strict location of industrial areas, and in pastoral, agricultural, forestry and rural/urban areas located at smaller or greater distances from the places of exploitation and processing

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Conclusion