IJERD – International Journal of Environmental and Rural Development (2022) 13-2

Research article
erd

Cadmium Bioaccumulation in Amaranthus spinosus L.
Grown in Contaminated Soil of Benguet Province,
Philippines
ELIZABETH T. DOM-OGEN*
Benguet State University, La Trinidad, Benguet, Philippines
Email: e.dom-ogen@bsu.edu.ph

ROMEO A. GOMEZ, JR.
Benguet State University, La Trinidad, Benguet, Philippines
Received 3 February 2022

Accepted 13 June 2022(*Corresponding Author)

Abstract Phytoremediation has become an alternative technology for cleaning up
contaminated areas by accumulation in the root and shoot systems. The study conducted a
98-day pot experiment to determine Cd accumulation and its morphological andphysiological effects on Amaranthus spinosus L. grown in the non contaminated forest (S1)and mine contaminated (S2) soils of Benguet. Soil and plant tissue analysis were done using
AAS method; quantitative descriptive method for morphological analysis; titration method
for vitamin C analysis; and Kjeldahl method for protein analysis. Amaranthus spinosus L.
grown in S1 accumulated 0.52 mg/kg Cd in the root and 0.88 mg/kg Cd in the shoot withsoil Cd concentration of 3.70 mg/kg at 7.43 pH. In S2, A. spinosus L. had taken up
0.000012 mg/kg Cd in the roots and in the shoot systems with 0.90 mg/kg Cd soil
concentration at 4.19 pH. Biological Accumulation Coefficient (BAC = 0.24) was generally
weak since the equivalent is less than 1 (BAC < 1, 0.24) while translocation factor (TF =1.69) is greater than 1 (TF>1, 1.69). For morphological characteristics comparing S1 and S2
results are the following: root length (372.33 mm and 284.70 mm); shoot length (399.33
mm and 132.33 mm); and, biomass (22.53 grams and 9.27 grams). Highly significant
differences were also noted for S1 and S2 on root length, shoot length, and biomass at α =0.01 with p – values of 0.002, 0.000, and 0.002, respectively. For the vitamin C and protein
content, both (S1 and S2) were not affected. From these results, it can be concluded that
Amaranthus spinosus L. can accumulate significant concentration of Cd in its root andshoot systems and allows Cd mobility in its system. It is then recommended that thecapability of Amaranthus spinosus L. for Cd tolerance requires further studies.
Keywords Amaranthus spinosus L., bioaccumulation, phytoremediation, physiological,
morphological characteristics

INTRODUCTION
Environmental sustainability issues are pressuring global concerns at present because of increasing
population and industrialization. It had been realized that anthropogenic activities such as mining
despite its substantial contribution to economic growth and development resulted towards
environmental problems (Castillo et al., 2010). In the Philippines, it had established mining
industries but problems with proper tailings disposal and policies for mitigation are not yet in placecausing leakage of hazardous chemicals like cadmium, lead and copper (CPA, 2007). The presenceof such contaminants in excess can lead to the reduction and inhibition of growth in plants
inflicting serious morphological, metabolic, and physiological anomalies. Correspondingly, thesecontaminants cannot be mineralized or degraded to less toxic forms; can be leached to nearby
farmlands and accumulated through the food chain; thus, requiring suitable methods for theirelimination (Chen et al., 2014).

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Addressing these, phytoremediation has become an alternative technology for cleaning up
contaminated areas. Amaranthus spinosus L. (Amaranthaceae) commonly called pigweed canbioconcentrate Cd, Zn and Fe invariably high in leaf tissues (Prasad and Freitas, 2003), and shows
best morphological and anatomical structure adaptation to stressful environments (Gharge andMenon, 2017).
Correspondingly, Amaranthus spinosus L. is a potential agent for heavy metal accumulationand translocation for Cu, Pb and Cd (Chinmayee et al., 2012) and among the dominant species
growing in some mine sites in the Philippines (Malik et al., 2010).
OBJECTIVE
The study concerns the investigation of the potential ability of Amaranthus spinosus L. toaccumulate Cd in the root and shoot system and how it responds morphologically andphysiologically.
METHODOLOGY
Sample Sites
The soil sampling sites were located at Alno, La Trinidad and Antamok, Itogon, Benguet (Fig. 1).
La Trinidad and Itogon are two of the 13 municipalities that comprise Benguet which, together
with five other provinces, make up the Cordillera Administrative Region.Alno has an estimatedland area of 958.35 ha. It is the third largest village in this municipality of La Trinidad. An area of
30.8 ha of forest and brushlands is classified as the Alno communal forest (Lumbres et al., 2014).
The municipality of Itogon is the core of the Baguio Mining District. Before the World War II,
large-scale mines operated, small-scale mining thrived. For Antamok, Itogon decommissioned
tailings dam had been abandoned for 22 years during the collection but still a basin of mine waste
for small scale miners since the tailing dam used for the study had operated for 7 years and wasshut down last April 1998 (Chaloping-March, 2019).

Fig. 1 Location map of Alno, La Trinidad, Benguet and of Antamok, Itogon, Benguet
Soil Sample Characteristic, pH and Cadmium Analysis
The identification of non-contaminated and contaminated soil was based on Pfeiffer et al. (1988)
and the US EPA (1994) for standard maximum concentration of contaminants for toxicity
characteristics. Soil samples were collected using composite soil sampling (Brady and Weil, 2000).
For soil pH determination the potentiometric method was employed. The concentrations of heavy
metals in soil samples were determined using Atomic Absorption Spectroscopy (AAS).

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Plant Morphological Observation on the 98th Day
Plants were carefully uprooted from the plastic pots then washed properly. The plants were cut
separating the root and shoot system for length measurement, and were air dried. Also, it was ovendried at 60 degrees Centigrade for biomass.
Determination of Vitamin C and Protein Content of the Plant on the 98th Day
The plants used in the morphological study were processed and analyzed separately. The vitamin C
content from the plant samples was measured based on the redox titration. The total protein content
from the plant samples was measured based on the Kjeldahl method.
Bioaccumulation Evaluation
Bioaccumulation and phytoextraction were evaluated in terms of Biological Accumulation
Coefficient (BAC), Biological Coefficient Factor (BCF) and Trans-location Factor (TF) whereby;
BAC = [metal] shoot / [metal] soil
BCF = [metal] root and shoot / [metal] soil
TF = [metal] shoot / [metal] root
Treatment of Data
The data were tabulated, interpreted, and analyzed using comparative experimental research design.
The t-test was used to determine the differences in the soil pH and soil Cd content of noncontaminated and contaminated soil; plant tissue Cd content analysis of each plant systems (rootand shoot); and the plant morphological and physiological changes in Amaranthus spinosus L. on
the 98th day.
RESULTS AND DISCUSSION
Cadmium Bioaccumulation in the Root and Shoot System of Amaranthus spinosus Linn
Table 1 shows the mean Cd concentration in the root and shoot systems of Amaranthus spinosus L.
planted on non-contaminated (S1) and contaminated (S2) soils. The mean Cd content for the S1 in
the root and shoot systems was non-detectable as represented by the value of 0.000012 mg/kg dryweight while for S2 in the root and shoot systems were 0.520000 and 0.880000 mg/kg dry weight,
respectively.
Table 1 Mean cadmium concentration on the root and shoot of Amaranthu spinosus L.

Root

Non-contaminated soil (S1)mean (mg/kg)
0.000012

Contaminated soil (S2) mean
(mg/kg)0.520000

Shoot

0.000012

0.880000

Plant organs

P - value
0.002**
0.003**

Legend:** highly significant at α = 0.01

Using t- test at α = 0.01, the accumulation of cadmium in the root and shoot systems of A.
spinosus L. comparing S1 and S2 is highly significant with a p = value of 0.002 and 0.003,
respectively. This suggests that with 0.90 mg/kg in S1 mean Cd concentration, absorption andaccumulation from the soil to the roots and translocation to the shoot system did not occur while at
3.70 mg/kg mean Cd concentration in S2 allows to some limited extent of Cd absorption andaccumulation by the root from the soil then translocated to the shoot system.
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According to Pantazis et al. (2007), the uptake of Cd by root from the soil depends on the soil
properties like Cd concentration and level of organic matter aside from pH. Dada (2019) reported
that A. spinosus L. accumulated 5.24 mg/kg in the root and 3.03 mg/kg in the shoot in soil of pH of
8.4 and 16.10 mg/kg soil Cd concentration. Moreover, Carrion and Mendoza (2019) result showsthat A. spinosus L. accumulated 0.55 mg/kg Cd in the shoot system with 7.49 soil pH and 2.02
mg/kg Cd soil concentration.
Bioaccumulation Evaluation of Amaranthus spinosus L.
Bioaccumulation evaluation of Amaranthus spinosus L. were based from the computed value of
Biological Accumulation Coefficient (BAC), Biological Coefficient Factor (BCF) andTranslocation Factor (TF). The BAC value is 0.24, BCF is 0.14 and TF value is 1.69. The BAC(0.24) and BCF (0.38) values were generally weak in A. spinosus L. (Table 2) since theirequivalents are less than 1 (BAC & BCF <1) while Translocation Factor (TF) is greater than 1 (TF> 1 = 1.69). The TF value (TF > 1) indicates capability to accumulate and transport cadmium in its
organs at 3.70 mg/kg soil Cd concentration and 7.43 soil pH. With the value of 1.69 TFCd, it could
be deduced that the translocation of Cd from the roots to the shoot system of Amaranthus spinosus
L. was relatively efficient but it cannot be identified as an excluder, accumulator or extractor.
Table 2 BAC; TF; and BCF of Amaranthus spinosus L.
Accumulation characteristics

Equivalent

BAC

0.24

TF

1.69

BCF

0.38

Cadmium Bioaccumulation Effect on Morphological Characteristics ofAmaranthus spinosus L.
The morphological characteristics of Amaranthus spinosus L. measured after 98 days of growth aresummarized in Table 3. These characteristics, with the paired mean measurements obtained fromthose planted in S1 and S2 soils respectively, include: root length (372.33 mm and 284.70 mm);shoot length (399.33 mm and 132.33 mm); and, biomass (22.53 grams and 9.27 grams).
Table 3 Morphological characteristics of the Amaranthus spinosus L. on the two sites
Characteristics

Non-contaminated soil (s1) mean

Contaminated soil (s2) mean

P - value

Root length (mm)372.33284.700.002**

Shoot length (mm)399.33132.330.000**

Biomass (grams)
22.53
Legend: ** highly significant at α = 0.01

9.27

0.002**

Highly significant differences were noted for S1 and S2 on root length, shoot length, andbiomass at α = 0.01 with p – values of 0.002, 0.000, and 0.002, respectively. Amaranthus spinosus
L. planted at 0.90 mg/kg in S1 are longer in root and shoot length and had higher biomass ascompared to Amaranthus spinosus L. at 3.70 mg/kg soil concentration of S2; the latter had shortroot and shoot length and had less biomass.
The morphological results of Amaranthus spinosus L. in S1 having longer root and shootlength and higher biomass as compared to S2 having short root and shoot length and less biomass
can be due to the nil and greater amounts of Cd root and shoot accumulation after the 98-day
growth, respectively. Other observations for S2 that are not found in S1 were thicker stem diameter,
delayed development, and leaf chlorosis.
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These morphological observations in S2 are the results of plants ability to adjust to its
contaminated environment by delaying or arresting mitotic division (Baran et al., 2010) affecting
the length development of the root. The short roots will be deprived of nutrient demand and supply
because its source is limited only to its immediate surroundings resulting to short shoot systembecause of plant nutrient deficiency. Moreover, the presence of Cd in the plant system inhibits
photosynthesis hampering growth and development resulting to plant decreased biomass (He et al.,2015).
Effect on the Vitamin C and Protein Content of Amaranthus spinosus L.
The vitamin C content in organs of Amaranthus spinosus L. planted in both S1 and S2 soils is
2.40%. The plant protein content, on the other hand, is at 5.18% (S1) and 4.73% (S2). Statistically,
there were no significant differences in the vitamin C (2.40% at 0.90 mg/kg – S1 and 2.40% at 3.70
mg/kg – S2) and protein (5.18% at 0.90 mg/kg – S1 and 4.73% at 3.70 mg/kg – S2) contents ofAmaranthus spinosus L. in both soil samples were noted. This is supported by the p-values
obtained comparing S1 and S2 for the physiological characteristics at 1.000 and 0.684 respectively(Table 4). The highly significant differences of the soil Cd concentrations of S1 and S2 apparently
did not at all affect the vitamin C and protein contents of plants grown in both S1 and S2. The
result may be due to the plants ability to maintain its metabolic activities by storing Cd in the cellwall and vacuole of the root and the shoot systems, thereby continuing growth and development.
Table 4 Mean vitamin C and protein content of the Amaranthus spinosus L.
plant organs on the two sample sites
Mean (%)

Physiological characteristics

P - valueNon-contaminated soil (s1)Contaminated soil (s2)Vitamin C content

2.40

2.40

1.000ns

Protein content

5.18

4.73

0.684ns

Legend: ns - not significant at α = 0.01

Vitamin C and protein are important factors for growth and development since protein
responds to a wide variety of stresses within the plant body while vitamin C plays an important rolein the adaptation and ultimate survival of plants (Dinakar et al., 2008). The result of the study was
similar to the study of Jibril et al. (2017) on lettuce where soil Cd concentrations of 0, 3, 6, 9 and
12 mg/kg have no significant effect in flavonoids, vitamin C and proline. This was confirmed by
Wang et al. (2009) on Cd toxicity on N metabolism in leaves of Solanum nigrum in 6.5 soil pH
where the concentration did not decrease significantly in soil Cd concentration at 6, 12 and 24
mg/kg.
CONCLUSION
Phytoremediation is a low cost and environmental friendly method to eliminate soil contaminants.
Amaranthus spinosus L. had been used since literatures suggest that it has the capability to extract
heavy metals and can survive to adverse conditions. The findings of the study shows that there is asignificant accumulation of Cd in Amaranthus spinosus L. on contaminated soil (root-0.52 mg/kg
and shoot-0.88mg/kg) and non-detectable Cd accumulation in non-contaminated soil. Amaranthus
spinosus L. plants in non-contaminated soil are taller compared to those in contaminated soils
which are short. Given the morphological characteristics of the plants, it follows that those in S1
have higher biomass as those in S2 having lower biomass. Also, vitamin C and protein content are
not affected by the amount of Cd in two sample sites. Therefore, Amaranthus spinosus L. cansurvive in the environment with 3.70 mg/kg soil Cd concentration at 4.19 pH.

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