Potential Phytoremediator of Native Species in Soils Contaminated by Heavy Metals in the Garbage Dump Quitasol-Imponeda Abancay
Abstract
One of the problems that affects the city of Abancay is the final disposal of solid waste in the garbage dump of Quitasol-Imponeda, located only six kilometers from the city. There is an average garbage accumulation of fifty tons per day for the entire city and the district of Tamburco involving large concentration of heavy metals, with the inhabitants of this area being the most affected as well as the flora, fauna and the environment.
Heavy metals are one of the groups of environmental pollutants subject to further investigation and concern, mainly due to their persistence and the low concentrations at which they can manifest their toxic effects [1].
Regarding its toxic effects, the most problematic heavy metals are mercury (Hg), cadmium (Cd), lead (Pb), arsenic (As), copper (Cu), zinc (Zn), tin (Sn) and chromium (Cr) [2]. Faced with the problem described, it is necessary to find alternatives that allow the recovery and remediation of contamination by heavy metals produced by solid waste in the dump.
Currently, for the recovery of soils contaminated with heavy metals there are several technologies [3], which often resort to the use of metal-phytate plants that can be used in the processes of phytorestoration and phytoremediation to recover sediments and waters contaminated by heavy metals, eliminating pollutants from the environment or making them harmless [4]. Phytoremediation is often considered as an alternative for conventional remediation technologies because it is an economically sustainable, efficient and environmentally friendly activity [5].
Phytoremediation is an emerging technology for the remediation of contaminated sites due to its profitability, aesthetic advantages and long-term applicability.
Conventional remediation technologies are based on biological, physical and chemical methods, which can be used together to reduce pollution to a safe and acceptable level [6]. Despite being efficient, these methods are expensive, timeconsuming and environmentally destructive [7], [8]. At the same time, they are often detrimental to the natural environment of the soil and generate large amounts of waste [9]. Phytoremediation is an emerging technology for the remediation of contaminated sites due to its profitability, aesthetic advantages and long-term applicability [10], [11].
The phytoextraction or phytoaccumulation consists of the absorption of polluting metals by the roots of the plants and their accumulation in stems and leaves. The first step for the application of this technique is the selection of the most suitable plant species for the metals present and the characteristics of the site. Once the vegetative development of the plant is complete, the next step is to cut them and proceed to their incineration and transfer of the ashes to a sanitary landfill. Phytoaccumulation can be repeated indefinitely until the remaining concentration of metals in the soil is within the limits considered acceptable [12]. Phytoremediation is based on the use of plants and their associated microbiota to eliminate, retain or reduce contaminants present in the environment and can operate through various mechanisms that involve different parts of plants [13], [14]. A wide diversity of species that are used for this purpose has been identified. Some of them, due to their great capacity to accumulate heavy metals, are called hyperaccumulators.
Phytoremediation is attractive to improve soil due to its low cost, and because it is aesthetically pleasing and respectful with the environment [15], [16]. Conventional methods are often expensive and can irreversibly affect the properties of soil, water and the living beings that inhabit them [17].
There are so-called metallofilic plants, which have developed physiological mechanisms to resist, tolerate and survive in soils degraded by mining activities [18]. The use of autochthonous plant species is generally favored because they show tolerance to imposed stress conditions, require less maintenance and present less environmental and human risks than non-native or genetically altered species [19].
Phytoremediation processes are most effective when contaminants are present at low to medium levels, since high levels of contaminants can inhibit the growth and activity of plants and microbes [20].
For the phytoremediation of heavy metals (and phytoextraction in particular), the bioavailability of metals in contaminated soils is a crucial factor that regulates the absorption of heavy metals by the roots of plants [21], [22].
Species of plant differ widely in their ability to accumulate heavy metals. Many authors [23], [24] concluded that the concentrations of metals in plants that grow in the same soil vary between species and even between genotypes of a species. Three native plant species from the Abancay area with phytoremediation capacity were selected.
In general, metals with greater bioavailability for absorption by storage plants are: Cd, nickel (Ni), Zn, As, selenium (Se) and Cu. With moderate behavior are cobalt (Co), manganese (Mn) and iron (Fe), while Pb, Chrome (Cr) and uranium (U) are practically not bioavailable [25].
Some trace elements are essential for the nutrition and growth of plants [boron (B), Cu, Fe, Mn, molybdenum (Mo) and Zn] and animals [As, Cu, Co, Fe, Mn, Mo, Zn, Cr, fluorine (F), Ni, Sn, Se and vanadium (V)]. The toxicity of these elements depends on the concentration, the chemical form and its persistence [26].
The purpose of the work is to evaluate the phytoremediating potential of three native plant species: Amaranthus spinosus, Amaranthus hybridus and Brassica rapa in soils contaminated with heavy metals, having selected five heavy metals: Zn, Cd, Pb, Cr and Ni in the garbage dump of Quitasol-Imposed as an alternative to recover the contaminated area.
The experimental part of the work was carried out under field conditions measuring plant growth, dry matter production and the absorption of heavy metals in roots, stems and leaves of the three native plant species. These results show the phytoremediation potential of these species that have rapid growth, resistance, and do not require chemical controls because they are native to the area, being an alternative to the recovery of soils contaminated by heavy metals in the garbage dump.
The general purpose of the present research is to determine the phytoremediation potential of Amaranthus spinosus, Brassica rapa and Amaranthus hybridus in soils contaminated by heavy metals in the garbage dump of Quitasol-Imponeda, Abancay.
The specific objectives of the present study are as follows: determine the concentration of Heavy Metals (HM): Pb, Cd, Ni, Cr and Zn in the waste matrix, in the samples of roots, stems, leaves of three native species (Amaranthus hybridus, Amaranthus spinosus, Brassica rapa) in the garbage dump of Quitasol-Imponeda Abancay, evaluate the phytoremediation potential in three native species (Brassica rapa, Amaranthus hybridus and Amaranthus spinosus) as heavy metals extractors in the garbage dump of the sector of Quitasol-Imponeda Abancay.
Phytoremediation involves the use of plants to eliminate or reduce the toxicity of environmental pollutants. The main technologies for the phytoremediation of metals are: phytoextraction ‒ the use of plants to extract metals from the soil, transport them and accumulate them in the organs of the aerial part, and phytostabilization ‒ the use of plants to minimize the mobility of metals through their accumulation in the root or their precipitation in the rhizosphere [26].
The experimental unit was the garbage dump of Quitasol-Imponeda located 6 km from the city of Abancay, with an area of land with heavy metals of all the waste accumulated by the residents of the city of Abancay and the district of Tamburco.
Three parcels were selected and identified: plot A (1, 2, 3), plot B (1, 2, 3) and plot C (1, 2, 3) in three different places within the garbage dump of Quitasol-Imponeda. Three native species were planted. The soil of the selected plots were removed, prepared and demarcated, each measuring two meters by four meters each. The plots were protected with screens to prevent the entry of foreign objects.
The seeds of the native species were collected from the zone of the Yanaca district as well as the buffer zone of the national Santuary Ampay especially clean of metals. All of them were planted in the garbage dump of Quitasol-Imponeda whose characteristics are summarized in Table 1-3 (Figure 1-3).
Water analysis | ||||
---|---|---|---|---|
Place 1* | Place 2** | |||
Samples | ||||
Source No. | 1.1 | 1.2 | 2.1 | 2.2 |
Water temperature [°C] | 6.1 | 5.6 | 5.2 | 6.0 |
Potential of hydrogen ions [pH] | 8.1 | 7.92 | 8.27 | 8.28 |
Electrical conductivity [microsiemens] | 467 | 487 | 211.6 | 229.4 |
Characteristics | Value | Assignment |
---|---|---|
Ph | 7.49 | Slightly alkaline |
O.M.% | 1.48 | |
Texture | ||
Clay% | Sandy loam soil | |
Plot A | 18 | |
Plot B | 14 | |
Plot C | 14 | |
Silt% | Sandy loam soil | |
Plot A | 18 | |
Plot B | 18 | |
Plot C | 20 | |
Sand% | Sandy loam soil | |
Plot A | 64 | |
Plot B | 68 | |
Plot C | 66 |
Characteristics | Value | Assignment |
---|---|---|
CEC | mEq/100 g | |
Plot A | 18.6 | |
Plot B | 16.8 | |
Plot C | 16.1 |
Characteristics | Value [mg/kg] | Assignment [mg/kg DLM] |
---|---|---|
Cd Plot A Plot B Plot C |
1.48 1.48 3.11 |
0.04 |
Cr Plot A Plot B Plot C |
22.64 13.07 19.74 |
0.04 |
Ni Plot A Plot B Plot C |
39.39 23.16 27.52 |
0.06 |
Pb Plot A Plot B Plot C |
9.94 10.38 20.45 |
0.06 |
Zn Plot A Plot B Plot C |
50.01 46.03 97.20 |
0.2 |
Amaranthus hybridus | Brassica rapa | Amaranthus spinosus | Detection limit of the method [mg/kg] | ||
---|---|---|---|---|---|
Ni | A B C |
1.77 1.79 4.98 |
1.30 4.10 3.70 |
1.50 1.42 3.90 |
0.06 |
Zn | A B C |
19.2 54.1 168.6 |
50.5 48.3 94.8 |
21.4 60.1 138.6 |
0.20 |
Cd | A B C |
0.24 0.13 0.66 |
0.44 0.39 0.42 |
0.25 0.16 0.70 |
0.40 |
Pb | A B C |
1.11 0.90 5.30 |
0.68 1.29 2.77 |
1.2 0.97 4.90 |
0.06 |
Cr | A B C |
2.49 1.58 8.48 |
1.91 4.22 5.24 |
1.80 1.60 8.80 |
0.04 |
Amaranthus spinosus | Amaranthus spinosus | Brassica rapa | Brassica rapa | Amaranthus hybridus | Amaranthus hybridus | ||
---|---|---|---|---|---|---|---|
Repetition 1 | Repetition 2 | Repetition 1 | Repetition 2 | Repetition 1 | Repetition 2 | ||
Ni | A B C |
0.097 0.50 MLD* |
0.04 MLD* 3.77 |
0.35 0.34 0.04 |
0.46 MLD* 0.18 |
1.73 3.08 1.68 |
0.89 0.84 0.39 |
Zn | A B C |
1.96 10.75 18.73 |
9.05 12.88 24.28 |
22.56 39.97 22.46 |
7.98 34.53 8.06 |
18.52 20.69 15.49 |
23.03 18.39 12.15 |
Cd | A B C |
0.17 0.33 0.55 |
0.18 0.31 0.58 |
0.14 0.33 0.190 |
0.14 0.42 0.08 |
0.27 0.28 0.18 |
0.22 0.09 0.24 |
Pb | A B C |
0.21 0.13 1.03 |
1.05 1.74 0.59 |
0.709 0.451 0.709 |
0.27 0.92 1.29 |
0.93 0.65 0.98 |
0.88 1.37 0.93 |
Cr | A B C |
0.74 0.52 2.38 |
3.23 3.66 0.55 |
1.905 0.699 0.735 |
0.59 1.48 0.43 |
1.91 0.69 0.74 |
0.59 1.48 0.43 |
Amaranthus spinosus | Amaranthus spinosus | Brassica rapa | Brassica rapa | Amaranthus hybridus | Amaranthus hybridus | ||
---|---|---|---|---|---|---|---|
Repetition 1 | Repetition 2 | Repetition 1 | Repetition 2 | Repetition 1 | Repetition 2 | ||
Ni | A B C |
MLD 0.67 0.09 |
0.10 MLD* MLD |
MLD* 0.67 0.08 |
MLD* 0.14 0.01 |
0.03 0.01 0.37 |
MLD* 0.06 0.08 |
Zn | A B C |
2.13 7.16 8.89 |
7.58 4.28 4.04 |
5.80 13.97 10.81 |
3.11 10.61 0.73 |
2.29 3.21 5.07 |
5.87 5.79 2.68 |
Cd | A B C |
0.02 0.60 0.45 |
0.44 0.17 0.27 |
0.08 0.30 0.31 |
0.18 0.35 0.001 |
0.16 0.01 0.12 |
0.09 0.05 0.09 |
Pb | A B C |
0.33 1.97 0.95 |
0.51 0.01 0.68 |
0.56 0.14 0.38 |
0.13 0.24 0.12 |
0.14 0.07 0.54 |
0.09 0.15 0.22 |
Cr | A B C |
0.38 1.43 0.70 |
0.17 0.14 0.08 |
0.05 0.05 0.28 |
MLD* 0.18 0.05 |
0.25 0.72 0.60 |
MLD* 0.06 0.08 |
Amaranthus spinosus | Amaranthus spinosus | Brassica rapa | Brassica rapa | Amaranthus hybridus | Amaranthus hybridus | ||
---|---|---|---|---|---|---|---|
Repetition 1 | Repetition 2 | Repetition 1 | Repetition 2 | Repetition 1 | Repetition 2 | ||
Ni | A B C |
0.09 0.49 MLD* |
0.038 MLD* 3.77 |
0.42 MLD* 0.13 |
1.08 0.92 0.53 |
1.55 1.34 0.73 |
0.56 0.34 0.47 |
Zn | A B C |
4.69 6.68 4.17 |
4.77 11.63 5.63 |
3.53 4.71 10.32 |
4.26 2.41 7.35 |
2.71 4.57 6.05 |
3.81 4.34 8.83 |
Cd | A B C |
0.089 0.37 0.19 |
0.86 0.21 0.27 |
0.24 0.21 0.37 |
0.59 0.30 0.21 |
0.24 0.21 0.48 |
0.59 0.13 0.22 |
Pb | A B C |
0.99 1.15 1.76 |
2.12 1.65 0.53 |
0.57 0.35 1.14 |
1.81 1.59 1.76 |
1.21 1.51 2.07 |
0.65 0.74 0.76 |
Cr | A B C |
0.80 0.85 0.64 |
0.29 0.65 1.41 |
0.45 0.61 0.58 |
0.68 0.81 0.70 |
2.01 0.99 1.56 |
0.59 1.14 0.91 |