The cup plant (Silphium perfoliatum L.) – a viable solution for bioremediating soils polluted with heavy metals

Abstract

Heavy metal pollution, manifested by the accumulation, toxicity and persistence in soil, water, air, and living organisms, is a major environmental problem that requires energetic resolution. Mining tailing areas contain metal minerals such as Cu, Zn, Pb, Cr and Cd in high concentrations that pollute the environment and pose threats to human health. Phytoremediation represents a sustainable, long-term, and relatively inexpensive strategy, thus proving to be convenient for stabilizing and improving the environment in former heavy metal-polluted mining sites. This study presents the bioremediation potential of Silphium perfoliatum L. plants, in the vegetative stages of leaf rosette formation, grown on soil polluted with heavy metals from mining dumps in Moldova-Noua, in the Western part of Romania. The bioaccumulation factor (BAF), translocation factor (TF), metal uptake (MU) and removal efficiency (RE) of Cu, Zn, Cr and Pb by S. perfoliatum plants were determined in a potted experiment in controlled environmental conditions. The reference quantities of heavy metals have been determined in the studied soil sample. The experiment followed the dynamics of the translocation and accumulation of heavy metals in the soil, in the various organs of the silphium plants, during the formation of the leaf rosette (13-18 BBCH). The determination of the amount of heavy metals in soil and plants was achieved by the method of digestion with hydrochloric and nitric acid 3/1 (v/v) quantified by atomic absorption spectroscopy (AAS). The obtained experimental results demonstrate that the substrate has a high heavy metal content being at the alert threshold for Zn (260.01 mg kg-1 in substrate compared with alert threshold 300 mg kg-1) and at intervention thresholds for other metals (Cu -234.66 mg kg-1/200 mg kg-1; 299.08 mg kg-1/300 mg kg-1 and Pb-175.18 mg kg-1/100 mg kg-1). The average concentration of the metals determined in dynamics in the dry biomass of plants varied between roots, petioles, and laminas. The root is the main accumulator for Cu and Cr (Cu – 37.32 mg kg-1 -13 BBCH to 43.89 mg kg-1-15 BBCH and 80.71 mg kg-1 – 18 BBCH; Cr – 57.43 mg kg-1 – 13 BBCH to 93.36 mg kg-1 -18 BBCH), and for Zn and Pb the lamina seems to carry the same function. Preliminary results show that Silphium perfoliatum may be a viable alternative in the bioremediation and treatment of heavy metal-contaminated area.

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

“…There are a limited number of studies in the literature on the tolerance of the species S. perfoliatum to stress caused by excess heavy metals. Our previous studies [14] that determined the BAF of S. Perfoliatum on heavy metal-polluted soils revealed values ranging from 1.04 in the petioles to 5.17 in the roots; in the same context, the bioaccumulation variation of Zn was between 1.01 in the petioles and 2.53 in the lamina. Additionally, values of the ability to concentrate in plants between 119 and 1056 mg kg −1 have been determined for Zn, which are directly dependent on the amount of metal existing in the soil [61].…”

“…2.1. Biological Material-Silphium perfoliatum L. Plants Silphium perfoliatum belongs to the Asteraceae family, a species native to the North American prairies [59], which is used for decorative purposes [60], is cultivated as a fodder plant [61], and is used for the production of biofuels [62][63][64][65], but also for the phytoremediation of heavy metals in Ps [14,[66][67][68][69]. The growth rate is intense due to the deep root system, the aerial part formed by stems up to 3 m high [70], with large leaves of 85-120 cm 2 , which are numerous and oppositely arranged on the stems [71].…”

“…The metal ion content was determined by means of the atomic absorption spectrometry (AAS) method (Varian SpectrAA 280FS, Agilent Technologies Inc., Santa Clara County, CA, USA) according to ISO 11047/1998 [75]. A detailed description of the procedure used to treat plant and soil samples, from drying and calcination (plant samples) to obtaining the final sample, was provided by Sumalan et al [14].…”

“…Unfortunately, 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]. With the identification of new, sustainable, and less polluting energy sources, after 2000, the exploitation activity was drastically reduced, generating depopulation, abandoned mines, tailings dams, unmanaged tailings dumps and implicitly widespread pollution with heavy metals of the related ecosystems [14]. Pollution manifests itself not only in the strict location of industrial areas, but also in pastoral, agricultural, forestry and rural/urban areas located at smaller or greater distances from the places of exploitation and processing.…”

Assessment of Quality Indicators of Pressed Biofuel Produced from Coarse Herbaceous Plants and Determination of the Influence of Moisture on the Properties of Pellets

“…Biomass can be used to produce high calorific synthetic gas, a promising advanced fuel that can be produced by thermochemical gasification [21]. According to Romanian researchers, the potential for bioremediation of vegetation leaves of plants of Silphium perfoliatum L. growing in heavy metal-contaminated soil is quite high [22]. Lithuanian researchers also studied cup plants and found that in many cases growth conditions and nitrogen fertilization were two decisive factors for all studied parameters: number of stems per plant, stem height, green and dry masses, and yield [23].…”