Phytoremediation Made by Wild Plants

Phytoremediation involves different processes which have been considered as one of the most appropriate technique to encounter the problem of pollutants from the environment (Rastogi and Nandal, 2020). It is believed to be a more efficient method of pollutant removal using plants compared to the traditional methods. Today, in addition to the potential of naturally existing plants, transformed plants are also involved for phytoremediation of different pollutants. The mechanisms used with both plant groups are extraction, stabilization, accumulation, degradation, and detoxification (Bauddh et al., 2017; Vazquez-Nunez et al., 2018). Different techniques that have been used for phytoremediation are discussed next.

Rhizofiltration

Rhizofiltration involves the method of using plant roots, which absorb and sequester toxic pollutants from contaminated land surfaces or groundwater (Tiwari et al.,

2019). The technique of phytofiltration can be of two types: one is through the roots, known as rhizofiltration, and the second type is balstofiltration where the seedling of the plant accumulates the contaminants from the soil or the polluted water (Bauddh et al., 2017). Principally for rhizofiltration, plants must have roots that are fast-growing and more efficient in the accumulation of contaminants over a longer period. The toxic contaminants form a precipitate over the root surface. The performance of this technique depends on different factors such as the genotype of the plant and the types of contaminants. Plants for rhizofiltration should qualify with a high growth rate, high biomass production, ease of cultivation, best uptake, translocation and

Vetiver grass in the field with very dense biomass

FIGURE 8.3 Vetiver grass in the field with very dense biomass. (A) Rapid growing above ground biomass for rapid accumulation of contaminats; (B) very fibrous roots with high surface contact to the contaminated soil to adsorb or translocate pollutants to the above part of the plant. (Adapted with permission from Darajeh el al., 2019.)

accumulation ability, high tolerance to adverse conditions, highly available in the ecosystem, and adaptable to the agro-ecology. One best example for this technique could be Vetiver grass (Figure 8.3) (Darajeh et al., 2019; Siyar el al., 2020).

Several studies have been done to address phytoremediation through phytofiltration using different plant genotypes in different countries. Hence, those research works have been reviewed to better understand phytofiltration and its potential for the removal of heavy metals and other organic pollutants to create a safer environment. Research was carried out in Egypt to remove heavy metal pollutants by the use of the plant, Pistia stratiotes. Using this plant the removal of Cr, Zn, Cu, Pb, Ni, Co, and Fe from polluted soil was evaluated and the removal through rhizofiltration was ordered as, Fe > Mn > Cr > Pb > Zn > Ni > Co > Cu > Cd (Table 8.2). The bioconcentration factor (BCF) of most studied heavy metals, except Cr and Pb, was greater than 1000, while the translocation factor (TF) of most studied metals, except Pb and Cu, did not exceed 1. The rhizofiltration potential (RP) of heavy metals was higher than 1000 for Fe, and 100 for Cr, Pb, and Cu (Galal et al., 2017a). Arundo donax L. root cells blended with other polymers like chitosan (Cs), Gelatin (GP) and polyvinyl pyrrolidone (polymer ratio 3:1:1, respectively) were used to evaluate the efficiency of the fabricated mix for in vitro testing of rhizofiltration of dyes and it has been found effectively adsorbent (El-Aassar et al., 2018).

The University of Huila in Coahuila, Mexico, reported removal of heavy metals like Cr, Hg, and Pb using Zea mays and the results indicated the mortality potential of the heavy metals Cr at lOmg/L and Hg at 4.0mg/L was reported as 40% death rate, while the mortality potential of lead (Pb) at lOmg/L reported the death rate as 20%.Hence, mercury was more toxic at lower concentrations followed by Cr at lOmg/L being more toxic than lead with the same concentration. In the phytofiltration case, Z. mays acted as bioaccumulater to these heavy metals. Zea mays adsorbed

TABLE 8.2

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/% Order of Remediation

Place of

Study

(Country)

Source

Rhizofiltration

P. stratiotes

Mn, Cr. Zn. Cu. Pb. Ni.Co. Fe

Root removal order of heavy metals, Fe > Mn > Cr >

Pb > Zn > Ni >

Co > Cu > Cd

Egypt

Galal et al. (2017a)

A. donax

Heavy metals, toxins, and dyes from the environment

Dye removal

Egypt

El-Aassar et al. (2018)

Z mays

Cr. Hg, and Pb

Absorption of Hg by 88%

(1.758mg/L from 2.0mg/L). Cr 68% (3.42mg/L from 5.0mg/L)but lead absorption was less (30%)

Corhuila

Benavides et al. (2018)

Cattailfr latifolia); sedge (C. blanda,); sunflower (Я. animus); Indian mustard (Й. jtmcea)

Cr, Cu, and Cd

Cattail root had the highest BCF for Cr 1156. and Cu (2911) and Cd (6047)

Mustard roots had a high BCF for Cd (3485)

India

Clay and Pichtel (2019)

Jancus sp., Tamarix sp., and Suaeda sp.

Pb, Cd, Cr, Zn, Fe, Mn, and Cu

Most depletion for Juntas sp. followed by Tamarix sp and Suaeda sp.

Suada sp.( 153.42) sp. (206.10)sp.(258.90), which are much lower than the bare land water (660.27)

Iran

Zare et al. (2020)

Phytostabilization

B. pilosa and P. lanceolata

Cu

Shoot (142 mgkg1) roots (964mgkg1)

Brazil

Andreazza et al. (2015)

TABLE 8.2 (Continued)

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/% Order of Remediation

Place of

Study

(Country)

Source

V. cuspidata

Cr, Pb, Cu. Zn. and Cd

Highest

accumulation Cr, Cu, and Pb in the root

Egypt

Galal el al. (2017b)

R. sceleratus

Cu. Pb. Ni, Cd, and Mn

The high concentration of Cu and Pb (27.7 and 9.9mgkg') while the toxic concentration of Mn (2508mgkg') is in their roots compared to their shoots

Egypt

Farahat and Galal (2017)

Lemongrass (Cymbopogon flexuousus)

Cr*

Increased accumulation of chromium (Cr) from both roots and shoots within 60 days

India

Patra el al. (2018)

Soybean, M. circinelloides and three amendments organic fertilizer, rice husk, biochar, camp site at a combination of 1:1:2:1 ratio

Cu. Zn, Pb, and Mn

Removal of heavy metals from the soil in the order of Pb > Cd > Cu > Zn > Mn

China

Li el al. (2019)

L. stolonifera

Cu. Pb. Zn, Cr, Cd, and Ni

Bioaccumulation factor that exceeded 1, the translocation factor of the investigated metals was <1

Egypt

Galal et al. (2019)

TABLE 8.2 (Continued)

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/% Order of Remediation

Place of

Study

(Country)

Source

Four aquatic macrophytes (E. crassipes (Mart.) Solms, L. stolonifera (Guill. and Perr.) P.H. Raven (E. stagnina [Retz.] P.), Beauv. and (P. australis [Cav.] Trin. ex Steud.)

Cd. Ni. and Cu

The four species had

bioaccumulation factors(BAFs) greater than one, while their translocation factors (TFs) were less than 1

Egypt

Eid et al. (2020)

Л. donax

As

20mg/L when BC or plant growth promoting bacteria are present

Italy

Guarino et al. (2020)

Indigenous weed (S. pumila), energy plant (P. sinese), Cd tolerant Sedum plumbizincicola) and Cu tolerant plant (E. splendens)

Cd. Cu

P. sinese treatments decreased DGT extractable Cu and Cd by 52.1% and 40.5% than S. pumila treatment

China

Cui et al. (2020)

Phytoextraction

Amaranth CAmaranthus paniculatus), Indian mustard(B. juncea),and sunflower (H. annuus)

Pb and Cu

In the shoot, sunflower removed significantly higher Pb(50- 54%) and Cu (34-38%) compared to amaranth and Indian mustard

Malaysia

Rahman et al. (2013)

TABLE 8.2 (Continued)

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/%Order of Remediation

Place of

Study

(Country)

Source

5. vera Forssk. Ex J.F. Gmel

Cu. Cr. Ni. Zn. and Pb

According to biological accumulator coefficient, BAC=Cplant/

Cs(,,!=(), 1 to 1.0:5. vera is moderate accumulator plant for the metals according to the following order Cu>Zn>Ni>Cr

Libya

Bader et al. (2018)

P. ensiformis, B. nivea, A. prorerus, and //.

sibthorpioides

As, Cd, Pb, and Zn

P. ensiformis accumulated 1091 mg kg'1 As in the shoot, and its translocation factor (TF) was greater than 1, suggesting the potential capacity for As

phytoextraction,

B. nivea, A. prorerus, and H. sibthorpioides showed potential for

phytoextraction Cd in shoots (490.3, 175.4. and 128.5 mg kg1, respectively)

China

Pan et al., (2019)

B. juncea, H. annus, and Z mays

As

Additives K,HP04 or (NH4)S,0, for the mobilization of

Asphytoextraction up to 80%

Italy

Franchi et al. (2019)

TABLE 8.2 (Continued)

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/% Order of Remediation

Place of

Study

(Country)

Source

H. scoparia and H. strobilaceum

Cu. Zn. Cr, and Fe

Both plants were found to be the moderate extractor

Libya

Bader et al. (2020)

Napier grasses (P. purpureum 'purple’) and variegated giant reed (A. donax var versicolor)

Cd and Zn

109.3% and 55.4%, respectively

China

Hou et al. (2020)

Poplar plant (P. deltoids X nigra)

Toluene

Peak-season toluene mass removal rate ranging from 313 to 743|ig/day

Canada

Benlsrael et al. (2020)

Three Cardoon caltivars (Sardo, Siciliano, and Spagnolo)

As, Cd, Cu, Pb, and Sb

Pb content in the rhizosphere especially in the Sardo from about

  • 67.000 mg kg'1 pre remediation soil to about
  • 35.000 mgkg'1 after two round growth

Italy

Capozzi et al. (2020)

Phytovolatilization

As

hyperaccumulating plant, P. vittata

As

Percentage of arsenic

component per sample was 37% for arsenite and 63% for arsenate P. vittata is effective

volatilizing of As, it removed about 90% of the total uptake of As from As-contaminated soil

Japan

Sakakibara et al. (2010)

TABLE 8.2 (Continued)

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/% Order of Remediation

Place of

Study

(Country)

Source

Willow (Salix sp.) and hybrid poplar (Populiis sp.)

TCE. PCE

The transpired gases after 7 days of exposure, the fraction of transpired TCE to the TCE taken up by plant was 70-90%

U.S.

Limmer

and

Burken

(2016)

Phytodegradation

Three endophytic bacteria

augmented to two kinds of grass, L. fusca, and 11. mutica

Petroleum

hydrocarbons

Oil-contaminated soil (46.8 oil kg'1 soil) and maximum oil degradation (80%) was achieved with B. mustica plant augmented with the endophytes

Pakistan

Fatima

etal.

(2018)

H. vertuculata (L.F)

Phenol

H. verticillata efficient degraded phenol in solutions with initial

concentration lowers than 200mgL'‘

China

Chang

etal.

(2020)

Phytodetoxification

i The grass, V. zizanioides (L.) Nash

Genotoxicity with heavy metals

In the research report, a significant reduction of the concentration of heavy metals and decreases genotoxic potential was observed

India

Ghosh et al. (2014)

TABLE 8.2 (Continued)

Phytoremediation of Pollutants Using Wild Plants

Techniques Employed by Plants

Plants Name used for

Phytoremediation

Pollutants Targeted to be Removed

Concentration of Pollutants mg/ kg/% Order of Remediation

Place of

Study

(Country)

Source

5. nigrum mediated by endophytic fungi

Cd

RSF-6L inoculation decreased uptake of Cd in roots and above ground parts, as evidenced by a low BCF and improved tolerance index (TI)

Republic of Korea

Khan et al (2017)

Willow tree (5. caprea)

Iron cyanide

Young leaves 15.197% and old leaves

accumulates more due to longer exposure time

Germany

Dimitrova el al. (201S)

mercury and decreased it by 88% (1.758mg/L) compared to the initial concentration (2.0mg/L) (Table 8.2); likewise, the lead metal absorption potential was also found high with a reduction of 68% compared to the initial concentration of 5.0 mg/L. The absorption potential of chromium was not as significant as for the other metals, the reduction percentage was found to be 30% (1.5lmg/L) (Benavides etal., 2018).

There are four plant species evaluated for rhizofiltration of heavy metals available in synthetic produced water including cattail (Typha latifolia), sage (Carex blanda), sunflower (H. animus), and Indian mustard (В. juncea). All plants evaluated for absorption of heavy metals from polluted water and soil from wetlands proved that they accumulated more metals in their roots than their shoots. Cattail root had the highest BCF with Cr (1156), Cu (2911), and Cd (6047), so this plant is proved to be a potential resource for removal of heavy metals. Moreover, Mustard root had a high BCF with Cd (3485) (Table 8.2). Mustard, cattail, and sage had TF values 1, indicating their potential as metal excluders of produced water (Clay and Pichtel, 2019). Another research performed in Iran for the removal of heavy metals (Pb, Cd, Cr, Zn, Fe, Mn, and Cu) using plants Jancus. sp., Tamarix sp., and Suaeda sp.; maximum depletion was reported by Juncus sp., followed by Tamarix sp. It was found Suaeda sp. (153.42) Tamarix sp. (20630)Jancus sp.(258.90), which were much lower than the bare land water (660.27) (Zare et al, 2020). It is concluded from this discussion that mesophytes plants are ideal for rhizofiltration because these plants have extensive and fibrous root systems than hydrophytes. It can be applied for the absorption of radioactive elements from contaminated areas (Patra etal., 2020). The benefit of this technique is to relocate metals from the rhizospheric site and their subsequent translocation to aerial parts of the plants.

 
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