Phytoremediation Potential of Selected Ornamental Woody Species to Heavy Metal Accumulation in Response to Long-Term Irrigation with Treated Wastewater

Abstract

Arid and semiarid environments of Mediterranean countries suffer from scarcity of water resources, which limits their agriculture productivity. Using treated wastewater (TWW) is considered an alternative strategy for irrigation purposes in such areas. However, TWW contains substantial levels of heavy metals (HMs) and contaminants that pollute the environment and soil. The aim of this study is to evaluate the phytoremediation potential of six selected woody tree species under long-term irrigation with TWW. The concentration, bioaccumulation factor (BFC), translocation factor (TF), and comprehensive bioconcentration index (CBCI) of HMs were measured in the various parts (roots, bark, and leaves) of the studied tree species. The results show a general pattern of mineral accumulation in the roots and low translocation to the areal parts of various species. Cupressus sempervirens, which is a native species in Mediterranean environments, had higher TF values for Fe, Mn, Cu, Cr, Cd, and Pb metals in its areal parts compared to other tree species. The study shows that Ficus nitida has the potential to be a hyperaccumulator for Cd in its bark, with a TF value that exceeds 12. Deciduous trees species (Populus nigra and Robinia pseudoacacia) were found to have high TF values for Ni and Cd toward their areal parts, whereas a higher TF for Cr (1.21) was only found in P. nigra bark. Cupressus sempervirens had, significantly, the highest bark and leaf CBCI values (0.83 and 0.82, respectively), whereas Ficus nitida had the second-highest values in the bark and leaves (0.56 and 0.51, respectively). Therefore, Cupressus sempervirens and Ficus nitida are considered good hyperaccumulators for various HMs, and can be used for phytoremediation activities in polluted areas.

Lead and copper removal from sterile dumps by phytoremediation with Robinia pseudoacacia

“…Other studies identified an exclusion system of Helichrysum tyrrhenicum for Zn since this metal was mainly present in the epidermis of Helichrysum tyrrhenicum roots 38 and a poor Pb bioavailability 39 . Nevertheless, the amount of Pb accumulated in Robinia pseudoacacia leaves was in the range of 69–140 mg kg −1 , while other researchers reported ranges as follows: 7.5–39 mg kg −1 40 ; 30.7 mg kg −1 19 ; 21.66 mg kg −1 15 ; 6–15.5 mg kg −1 41 ; 2.7–4.12 mg kg −1 42 .…”

“…In an attempt to identify the most suitable and appropriate plant for phytoremedia-tion, different researchers have applied and tested the phytoremediation technology on soils contaminated with heavy metals using various plant species 15 – 18 . Thanks to their specific characteristics (frost and drought-resistant, grows well in degraded habitats, tolerance to heavy metals) the Robinia pseudoacacia (black locust) was widely investigated for phytoremediation of heavy metal polluted soils 13 – 15 , 18 , 19 . The results indicated that the leaves of Robinia pseudoacacia can accumulate important quantities of Pb, Zn, and Cu, the quantity increasing with their concentration in the contaminated soil.…”

Cadmium up Taking and Allocation in Wood Species Associated to Cacao Agroforestry Systems and Its Potential Role for Phytoextraction

“…Shoot Cd concentrations reached by T. superba in the present study are very similar to those exhibited by Populus spp. and Salix spp., two important phytoextractor species reported in the literature, under similar contamination conditions [ 24 , 27 , 32 , 33 , 34 , 47 , 48 , 49 ]. Swietenia macrophylla and Morus alba L. are also important phytoextractor tree species previously reported [ 50 , 51 , 52 ].…”

“…and Populus sp. in phytoextraction [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], showing that these species could be used as an efficient and cost-effective method to remove Cd contamination from agricultural soils [ 22 , 36 ]. On the one hand, the benefits associated with accompanying trees in cacao agroforestry systems have been widely studied in terms of carbon capture, water use efficiency and other nutritional benefits [ 18 , 19 , 38 ].…”