Removal of heavy metals from a contaminated [631711]

Removal of heavy metals from a contaminated
soil using phytoremediation
Georgiana Luiza Arnold Tatu, Nicolae Valentin Vladut , Iulian Voicea, Nicoleta Alexandra
Vanghele, and Mirabela Augustina Pruteanu*
National Research Development Institute for Machines and Installations Designed to Agriculture and
Food Industry, Research Department , 6 Ion Ionescu De La Brad Blv ., Bucharest, Romania
Abstract Environment pollution with heavy metals, can be a cause of the
industrialization activities and technological proce sses, and has become an
important issue. Soil contamination due to natural or anthropogenic causes
(such as mining, smelting, warfare and military training, electronic
industries, fossil fuel consumption, waste disposal, agrochemical use and
irrigation) is a major environmental hazard. Various remediation
techniques have been highlighted to clean or restore soils contaminated
with heavy metals such physical, chemical or biological. Phytoremediation
is a relatively new approach to removing contaminants from the
environmental. It may be defined as the use of plants to remove, destroy or
sequester hazardous substances from environmental.
1 Introduction
Brassicaceae is one of the largest angiosperm families, predominant in the temperate region
and best cultivat ed around the Mediterranean. They belong to a group of natural plants
conduplicate cotyledons (rare acumbent or existing) and the segment (rare lomentaceous or
nucciform) fruit, usually in general, tanks and have flowers with four petals of equal size in
the shape of a cross "crucifer" [1-5].
The Brassicaceae family can have a large number of genres and species: ranging from
338 to 380 genres and from 2500 to ca. 3700 species , and includes several genera like
Camelina, Crambe, Sinapis, Thlaspi and Brassica . The genus Brassica is the most important
one within the tribe Brassiceae , which includes some crops and species of great worldwide
economic importance such as Brassica oleracea L., Brassica napus L. and Brassica rapa L .
Brassica oleracea is a good exampl e with broccoli (Botrytis group), cauliflower (Botrytis
group), cabbage (Capitata group), kale (Acephala group), kohlrabi (Gongylodes group) and
brussels sprouts (Gemmifera group) being varieties or convars of the same polymorphic
species. Other well -known species within the Brassicaceae are Brassica rapa (turnip,
chinese cabbage), Brassica napus (rape, swede/rutabaga), Brassica juncea (indian/brown
mustard), Sinapis alba or Brassica hirta (white mustard), Brassica nigra (black mustard),
Armoracia rusticana (horse -radish), Raphanus sativus (radish, daikon), Barbarea verna

* Corresponding author: [anonimizat]

(land cress), Nasturtium officinale (watercress), Eruca vesicaria subsp.sativa (arugula) and
Wasabi japonica (wasabi) [1, 6-8].
Cruciferous vegetables are a precious source of bioactive co mpounds, such as
polyphenols and antioxidants, and a rich source of glucosinolates and their hydrolysis
products, including indoles and isothiocyanates, which offer more health benefits [ 3, 6, 9-
11]. Although horticultural plants provide a supply of fiber, vitamins and minerals, most
research has focused on the content of secondary metabolites, mainly glucosinolate. Recent
studies have shown that if food is formed, mainly from Brassicaceae, there is an
improvement in human health, can play a role in the pre vention and treatment of
inflammation, various gastrointestinal and digestive diseases and chronic diseases [12 -14].
Heavy metals and metalloids have been a major threat to human health and the
environment due to the lack of biodegradability, toxicity, pe rsistence and bioaccumulation
in the food chain. They are responsible for causing various disorders in humans, including
diseases such as Itai -Itai, Parkinson's, Alzheimer's, Wilson's, Skogholt's, Menkens, can,
also, affect the nervous system, some organs (kidneys, liver, heart), cardiovascular system,
can cause autism [15 -19].
Rapid industrialization and urbanization have contributed to the pollution of soil and
groundwater with various heavy metals, such as: Cd, Pb, Cu, Hg, As, Se, Zn, Ni [20, 21] .
The a nthropogenic causes (such as mining, smelting, warfare and military training,
electronic industries, fossil fuel consumption, waste disposal, agrochemical use and
irrigation) can contaminate the soil, for example : fossil fuels (coal) contain heavy metals
such as Hg, Pb, Cd, Cr, Cu, Co, Zn and Ni in concentrations of 0.1 to 18 mg kg-1; these
heavy metals are released into the environment by vapours , flue gas particles, fly ash and
ash from coal combustion [22, 23]. Another possibility to pollute the soil wit h heavy metals
is waste from construction materials and inappropriate soil storage in industrial mines.
Field application of phosphorus (P) fertilizers, Cu -based pesticides, biosolids and animal
manure and irrigation of wastewater and poorly treated indust rial wastewaters are the main
ways for heavy metals to enter into soils [20, 24] . Globally there are >5 million sites
covering 20 million ha of land in which the soils are contaminated by different heavy
metal(loid)s [25, 26]. A number of physical, chemica l and biological techniques can be
used to remediate metal contaminated soils. A promising, relatively new technology for
heavy metal contaminated sites is phytoremediation. Phytoremediation, which is derived
from the words “phyto” (plant) and “remediation ” (recovery) and has become a term in
1991, can be also defined as “bioremediation,” “botanical remediation” and “green
remediation.” Phytoremediation is a term which is related to ecological remediation
technologies that use plants as the main source. Wit h this technology, organic and inorganic
substances are removed from the contaminated area by using plants. The effects of this
method can be observed in low polluted areas in a short time. The negative aspect is that in
heavy contaminated areas the plants cannot be useful in a period of short time.
Phytoremediation is the use of plants to remove organic and/or inorganic contaminants
from biota (phytoextraction) , uptake and conversion into non -toxic forms
(phytovolatilization), or stabilization of an inorga nic into a less soluble form
(phytostabilization). Unlike the previously mentioned conventional methods,
phytoremediation is inexpensive, effective, can be implemented in situ, and is
environmentally friendly. A special advantage of phytoremediation is tha t soil functioning
is maintained and life is soil reactivated [27]. As such , phytoremediation is often referred to
botanical bioremediation or green remediation [28, 29] . The success of phytoremediation
depends upon the ability of a plant to uptake and tra nslocates heavy metals, a function of
the specific phenotype and genotype . Phytoremediation of heavy metal contaminated soil is
a developing technology that aims to extract or in -activate metals and it has attracted much
attention because it is an environ mentally friendly and relatively cheap technique [30, 31].

There are two basic strategies under develop ment. The first is the uses of hyper
accumulator plants that have the capacity to hyper accumulate heavy metals, and the second
is chemical chelate -enhan ced phytoextraction [32].
Plant species besides hyperaccumulators can also be used, as the heavy metals need not
be translocated to the shoots. Terrestrial plants are widely preferred for rhizofiltration as
they have fibrous root systems with fast growth. The rhizofiltration technique can be
constructed either as floating rafts on ponds or a s tank systems. One of the main
disadvantages of rhizofiltration involves growing plants in a greenhouse first and then
transferring them to the remediation site. Great care must be taken to maintain an optimum
pH in the effluent solution [33, 34] .
The application of other plants, such as Brassica juncea (Indian mustard), which
accumulate target heavy metals to a lesser extent but produce more aboveground biomass
so that overall accumulation is comparable to that of hyper accumulators due to production
of more biomass [35, 36] .According to Chaney et al. (1997), hyperaccumulation and
hypertolerance are more important in phytoremediation than high biomass. Use of
hyperaccumu lators will yield a metal -rich, low -volume biomass, which is economical and
easy to handle in case of both metal recovery and safe disposal. On the other hand use of
non-accumulators will yield a metal -poor, large -volume biomass, which will be
uneconomical to process for recovery of metals and also costly to safely dispose [37].
2 Phytoremediation of soil using vegetables from brassicaceae
family (cruciferous )
Heavy metals can pollute the environment from natural or anthropogenic sources. Lead can
reach th e environment by urban traffic using leaded fuels, pesticides, herbicides,
insecticides, electric batteries, the anthropogenic sources for copper are agriculture,
industrial waste, zinc fertilizers, pesticides and for zinc are mining and metallurgic
operat ions, pesticides and fertilizers [33, 38, 39] .
Phytoremediation process depends on the capacity of a plant to grab heavy metals,
depending on the specific phenotype and genotype. When chelating agents are used, such as
ethylenediamine triacetic acid (EDTA) , N- (2-hydroxyethyl) -ethylenediaminetriacetic acid
acid (HEDTA), citric acid (CA) , etc. , increases the mobility of the metal, thereby enhancing
phytoextraction [39-41].
Brassica juncea (Indian mustard) is one of the most used plants from Brassicaceae
family that can remove different heavy metals from contaminated soil [ 39, 42 -45].
2.1 Lead
Phytoremediation of a soil contaminated with lead using Brassica juncea (Indian mustard)
has good results. Some studies confirm that Brassica juncea can best accumul ate this heavy
metal in roots, followed by fruit and shoot. The higher concentration of P b in root it is due
to deep of roots in soil and roots ability for Pb accumulation . The effect of interaction
between soil and plant organs on lead accumulation in Brassica juncea plant show that the
highest value was in the interactin between contaminated soil and root part, and the lowest
value was in the interaction between uncontaminated soil and shoots [42].
EDTA and Brassica juncea increased the accumulation of l ead from the contamination
soil. Concentration of Pb in shoots of Indian mustard was also increased by EDTA addition
[43].
Ornamental kale ( Brassica oleracea var. Acephala ) is usually planted from early
autumn until late winter. Since most of the plants u sed for phytoremediation cannot be

grown during this time, kale can be a suitable option for phytoremediation and utilized
during autumn and winter in urban landscape, especially in metropolitan areas where high
levels of lead (Pb) pollutions exist. In gen eral, under salinity stress, kale var.acephala was
able to absorb lead [46].
According to Marchiol el all radish s howed a relatively low phytoremediation potential
of multicontaminated soil [48]. The overall results obtained indicate that there exists a n on-
linear positive relationship between the lead concentrations in the soil and that accumulated
in radish ( Raphanus sativus ) roots and shoots. It was also observed that by increasing the
lead concentration in soil, its accumulation in plant tissues increa sed. The major lead
accumulation occurred in the roots rather than shoots [49]. Efficient Pb uptake was
observed in the roots of contaminated radish compared with the control. Accumulation
metal element in the roots was, much higher than in shoot and leaves . Root growth
increased by increa sing the lead ion concentration . Root length of radish contaminated plant
is not affected under the toxicity of all concentration of lead metal, showed susceptibility to
elevated levels of lead metal . Lead exposure infl uenc ed several biochemical and
physiological parameters. Administration of excess amount of lead was followed by an
increase of Pb ions and its associated symptoms of toxicity in leaves [50].
Chinese cabbage can accumulate Pb in shoots [51]. Hamvumba et all s how that
Chinese cabbage ( Brassica chinensis ) has a poor growth pattern as the concentration of lead
in the soil increased among treatments. A good characteristic of Chinese cabbage is that this
plant is appropriate for phytoremediation and should accumula te metals only in the roots
[52].
2.2 Copper
Brassica juncea used soil decontamination with copper has a significant difference between
Cu accumulations in fruits and Cu accumulation in shoots, but there is no significantly
difference between the value of Cu accumulation in fruits and roots. Plant uptake of heavy
metals from soil accurse either passively with the mass flow of waer into the roots, or
through active transport crosses of the plasma membrane of root epiderma cells. From the
interaction between s oil and plant parts it can be seen that the highest value was in the
interaction between contaminated soil and fruits, whereas the lowest value was in the
interaction between control soil and shoots. May this due to pH of soil and the large
biomasses of fr uits in Brassica juncea plant . [42].
Brassica juncea and EDTA increased the accumulation of Cu. Concentration of Cu in
shoots of Indian mustard was also increased by EDTA addition [43]. A study using Chinese
turnip show that copper is accumulated in the plant from a soil contaminated [47].
2.3 Zinc
Brassica juncea plant parts has a significantly effects on Zn accumulation, the highest value
was in shoots and the lowest value was in roots. This plant is able to accumulate unusually
high concentrations o f Zn in their aboveground parts. In the interaction between sol and
plant parts it can be notice some significantly difference on Zn accumulation in plant, the
highest accumulation of Zn was in the interaction between shoots and contaminated soil,
where th e lowest accumulation of Zn was in the interaction between roots and control soil
[42].
Adding EDTA in a soil with Brassica juncea has no effect for Zn decontamination soil .
Chelate -enhanced phytoextraction might not be an adequate technique for a soil from a
paddy field [43]. According to Li et. all Chinese turnips have a strong ability to accumulate
zinc [47]. Zinc can be accumulated in shoots in Chinese cabbage [51].

3 Results
Compared the tolerance of three Brassica species to a multicontaminated soil and, based on
a calculated tolerance index, concluded that the tolerance order was Brassica juncea >
Brassica carina ta > Brassica oleracea [53].
Effect of interaction between soil and Indian mustard shoots on Pb, Cu and Zn
accumulation are presented in table 1 and data on metal s accumulation in different
vegetative parts , metal translocation, polyphenols and total chlorophyll , by three plants of
Brassica juncea in table 2.
Table 1. Pb, Cu and Zn accumulation in shoots Indian mustar d planted in contaminated and
uncontamina ted soil (control)
Method
applied Soil type Concentration metals in
soil, ppm Conce ntration metals
in shoots Indian
mustard , ppm References
Cu Zn Pb Cu Zn Pb
EDTA
and
Indian
mustard control 15.3 460 5.6 0.12 3.68 0.04 [43] contaminated soil 39.8 471 15.8 0.29 3.41 0.12
control 18.6 32.2 8.65 4.2 8.75 3.14 [54]
Indian
mustard control 32.3 106.9 11.1 9.3 28.4 1.5 [51] contaminated soil 114.2 1132.5 271.3 24.7 250.6 18.4
Table 2 . Accumulation of metals in Brassica juncea under pot assay [55]
Meta ls Concen
tration
[mg/kg] Metal uptake [μg/g] in
plant parts Metal
translocation
factor Polyphenols
[μg /ml] Total chlorophyll
[mg% fresh
weight ] Leaf Stem Root
Cu 10 15.27 37.18 43.12 0.61 032 38.7
25 29.28 33.15 47.12 0.66 0.56 40.1
Pb 10 32.11 41.13 58.10 0.63 0.76 56.42
25 38.11 80.31 101.13 0.59 0.35 58.11
Zn 10 19.88 16.68 26.57 0.69 0.68 13.26
25 36.12 21.44 57.49 0.50 0.25 18.0
Lead uptake was highest in leaves and stem where as zinc accumulation was highest in
roots. Copper were lea st preferred metals for ac cumulation by the plants.
4 Conclusion
Increased urbanization and industrialization is responsible for the conta minatin of soil with
metals. The ability of brassicas (these include 87 species from 11 genera ) to bioaccumulate
heavy metals can be used to reduce the level of contaminants in the soil (phytoremediation),
and thus to clean up and prepare soils for cultivation. Brassica juncea plant was able to
grow in heavy metals contaminated soil and also able to accumulate extraordina rily high
concentra tions of some metals in their roots, stems and/or leaves , to far exceeding levels
than present in the soil .
EDTA -enhanced phytoextrac tion would not remove adequate quanities of heavy metals
from soil . EDTA have capacity to reduce the co st and time required for remediation of
heavy -metal -polluted soil by increasing the bioaccumulation index of metal in plants.

Acknowledgements
This paper was financed by s upport of Executive Agency for Higher Education, Research,
Development and Innovation Funding, Exploratory Re search Programme, PN -III-P4-ID-PCE-2016 –

0860, contr. 174/ 08.08.2017, Research on the development of some mathematical models to evaluate
the impac t of soil contamination on fruits and vegetables – CONTAMOD and a grant of the
Romani an Researc h and Innovati on Ministry, through Programme 1 – Development of the national
research -development system, subprogramme 1.2 – Institutional perf ormance – Projects for financing
excellence in RDI, contract no. 16PFE.
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