International Journal of Scientific Research in Environmental Sciences (IJSRES), 1(3), pp. 44-49, 2013 Available online at http://www.ijsrpub.com/ijsres

©2013 IJSRPUB

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Full Length Research Paper

Comparative Phytoremediation of Chromium-Contaminated Soils by Alfalfa

(Medicago sativa) and Sorghum bicolor (L) Moench

Nooshin Karimi

Department of Soil Science, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran;

Email: nkarimi777@gmail.com

Received 15 January 2013; Accepted 20 February 2013

Abstract. A study was carried out to investigate the potential of alfalfa and sorghum for phytoremediation of soil contaminated

chromium. Soil samplings of 0-10 cm depths were taken. The experiment consisted of five treatments in which chromium

concentration varied from 0 to 10 mg/kg soil (blank (T1), soil contaminated with 2 mg/kg concentration of chromium (T2), soil

contaminated with 4 mg/kg concentration of chromium (T3), soil contaminated with 8 mg/kg concentration of chromium (T4),

soil contaminated with 10 mg/kg concentration of chromium (T5). Alfalfa and sorghum were grown for 50 days after seeding

in pots containing 5 kg of these soils. Chromium concentrations in soil after phytoremediation by alfalfa were 0.74, 1.16, 2.08,

and 4.00 in T2, T3, T4, and T5, respectively. Chromium concentrations in soil after phytoremediation by sorghum were 0.84,

1.36, 2.44, and 5.12 in T2, T3, T4, and T5, respectively. Concentration of chromium in soil in all treatments after

phytoremediation by alfalfa was decreased between 60-74%, and after phytoremediation by sorghum was decreased between

51.2-69.5%. The evidence provided by this experiment indicated that alfalfa and sorghum are effective accumulator plants for

phytoremediation of chromium, but the potential of alfalfa was more than sorghum for phytoremediation of chromium polluted

soils.

Key words: Alfalfa, Chromium, Phytoremediation, Soil contaminated, Sorghum

1. INTRODUCTION

Contaminated soils and waters pose a major

environmental and human health problem, which may

be partially solved by the emerging phytoremediation

technology. The use of plants for the removal of

xenobiotics and heavy metals from spillage sites,

sewage waters, sludges, soils and polluted areas has

become an important experimental and practical

approach over the last 15 years (Mojiri, 2012).

Remediation of heavy metals polluted soil could be

carried out using physico-chemicals processes such as

ion-exchange, precipitation, reverse osmosis,

evaporation and chemical reduction; however, the

measures required external man-made resources and

costly. Attention was given to phytoremediation by

which plant is applied to absorb, transform and

detoxify heavy metals. The phytoremediation method

was simple, efficient, cost effective and environmental

friendly (Mangkoedihardjo and Surahmaida, 2008).

The phytoremediation of metal-contaminated soils

offers a low cost method for soil remediation, and

some extracted metals may be recycled for value.

Plants that accumulate metals to high concentrations

are sometimes referred to as „„hyperaccumulators‟‟

(Mojiri, 2011).

Chromium (Cr) is an environmental pollutant

element and ranks seventh in abundance in the earth

crust. The major contributors of Cr contamination are

the leather tanning, electroplating, and stainless steel

industries (Dheri et al., 2007). Many investigations

were conducted about phytoremediation of chromium

contaminated soils (Mangkoedihardjo et al., 2008; Su

et al., 2005; Sudha and Kanmani, 2009). Dheri et al.

(2007) investigated comparative phytoremediation of

chromium-contaminated soils by fenugreek, spinach,

and raya. These results showed fenugreek, spinach,

and raya are affective for phytoremediation of

chromium contaminated soil.

Medicago sativa (alfalfa) is a flowering plant in the

pea family Fabaceae. It is a cool season perennial

legume from three to twelve years, depending upon

climate and variety. The plants grow to a height of up

to 1 metre (3 ft), and have a deep root system

sometimes stretching to 4.5 meters (15 ft), which

makes it very resilient, especially to droughts. It has a

tetraploid genome (Singh et al., 2009). Sorghum is a

genus of numerous species of grasses, one of which is

raised for grain and many of which are used

as fodder plants either cultivated or as part of pasture.

The plants are cultivated in warmer climates

worldwide. Species are native to tropical and

subtropical regions of all continents in addition to the

southwest Pacific and Australasia. Sorghum is in the

subfamily Panicoideae and the

tribe Andropogoneae (the tribe of big

bluestem and sugar cane) (Wikipedia, 2012).

Some researchers were reported that alfalfa, and

sorghum could be used for phytoremediation of heavy

metals from contaminated soils (Fellet and Marchiol,

Karimi

Comparative Phytoremediation of Chromium-Contaminated Soils by Alfalfa (Medicago sativa) and Sorghum bicolor (L)

Moench

45

2011; Vamerali et al., 2010; Singh et al., 2009; Kaimi

et al., 2007).

The objectives of this study were to investigate the

potential of alfalfa and sorghum for chromium-

contaminated soil.

2. MATERIALS AND METHODS

2.1. Site description, Sample preparation

The experiment was carried out at green house in

2011. Five kilograms of soil per treatment in earthen

pots was treated with five levels of chromium (0 (T1),

2 (T2), 4 (T3), 8 (T4), and 10.0 (T5) mg Cr kg-1

soil

through dipotassium chromate (K2Cr2O7), equilibrated

for 21 days at field-capacity moisture content (Dheri

et al., 2007), and then alfalfa (Medicago sativa) and

Sorghum bicolor (L.) Moench were grown for 50 days

after seeding.

Soil samples were air dried in a green house at a

temperature between 25ºC and 30ºC and sifted

through a 2- mm mesh sieve for preparation of soil

samples (Mojiri and Jalalian, 2011). The plant tissues

were prepared for laboratory analysis by Wet

Digestion method (Campbell and Plank, 1998).

2.2. Laboratory determinations

Soil pH was measured on saturated soil paste, the

electrical conductivity (EC) was measured on

saturation extracts (Richards, 1954); Soil texture was

determined by the Bouyoucos hydrometer method

(Gee and Bauder 1986).

Concentration of extractable chromium is soil and

plant samples were carried out in accordance the

Standard Methods (APHA, 2005). Soil properties

before phytoremediation are shown in Table 1.

Table 1: Soil properties before phytoremediation

pH EC (dSm-1) Clay (%) Sand (%) Cr (ppm)

7.00 1.00 14.00 41.42 0.000

2.3. Statistical analysis

Data will be analyzed using SPSS software.

Comparison between the average levels treatments

will be performed by Duncan‟s test.

3. RESULTS AND DISCUSSION

The comparing the extractable chromium in soil after

phytoremediation can be seen in Table 2 and Figure 1

and 2.

According to Table 2, Cr (ppm) was recorded in

order of 0.74, 1.16, 2.08, and 4.0 in soil after

phytoremediation by alfalfa, and it was found in order

of 0.84, 1.36, 2.44, and 5.12 after phytoremediation

by sorghum in T2, T3, T4 and T5, respectively.

Based on Table 2 and Figures 1 and 2, the

chromium concentration was reduced after

phytoremediation by alfalfa in order of 74%, 71%,

63%, and 60% in T4, T3, T3, and T5, respectively. It

was clear that maximum reduction of chromium

concentration was in T8.

Table 2: Comparing the extractable chromium in soil after phytoremediation by alfalfa and sorghum

Chromium (ppm) in soil after phytoremediation by

alfalfa

Chromium (ppm) in soil after phytoremediation by

sorghum

T2 (soil contaminated with 2 mg/kg concentration of chromium)

0.74a+ 0.84e

T3 (soil contaminated with 4 mg/kg concentration of chromium)

1.16b 1.36f

T4 (soil contaminated with 8 mg/kg concentration of chromium)

2.08c 2.44g

T5(soil contaminated with 10 mg/kg concentration of chromium)

4.00d 5.12h

+ Numbers followed by same letters in each column are not significantly (P<0.05) different according to the DMR test.

According to Table 2 and Figures 1 and 2, the

chromium concentration reduced after

phytoremediation by sorghum in order of 69.5%,

66%, 58%, and 51.2% in T4, T3, T3, and T5,

respectively. It was clear that maximum reduction of

chromium concentration was in T8.

International Journal of Scientific Research in Environmental Sciences (IJSRES), 1(3), pp. 44-49, 2013

46

Fig. 1: Extractable chromium in soil after phytoremediation by alfalfa

*p index showed chromium concentration in soil after phytoremediation

Fig. 2: Extractable chromium in soil after phytoremediation by sorghum

*p index showed chromium concentration in soil after phytoremediation

Data on the extractable concentration of chromium

in alfalfa and sorghum in the applied treatments can

be seen in Table 3.

Based on table 3, accumulation of chromium is

roots of alfalfa were more than in shoots of alfalfa.

Peralta-Videa et al. (2002) reported that uptake and

accumulation heavy metals by roots of alfalfa plant

were more than by shoots.

According to table 3, accumulation of chromium is

roots of sorghum were more than in shoots of

sorghum. Jadia and Fulekar (2009) reported heavy

metals were efficiently taken up mainly by roots of

sorghum plant at all the evaluated concentrations of 5,

10, 20, 40 and 50 ppm.

Based on Tables 2, and 3, it was clear that the

potential of alfalfa was more than sorghum for

phytoremediation of chromium polluted soils. The

accumulation of heavy metals in roots was more

important in shoots this is in line with findings of

Revathi et al. (2011), Mojiri (2011), Dheri et al.

(2007), and Abou-Shanab et al. (2007).

According to this study, alfalfa and sorghum are

effective accumulator plants for phytoremediation of

chromium. Shahriari et al. (2006) investigated the

effect of mixed plants alfalfa (Medicago sativa) and

fescue (Festuca arundinacea) on the

phytoremediation of contaminated soil. They reported

that alfalfa is an effective plant for phytoremediation

of soil contaminated. Revathi et al. (2011)

investigated phytoremediation of chromium

contaminated soil using sorghum plant. They reported

that sorghum is one of the best “Hyperaccumulators”

for the phytoremediation of metal polluted sites.

4. CONCLUSION

The phytoremediation of metal-contaminated soils

offers a low cost method for soil remediation, and

some extracted metals may be recycled for value. This

study showed that alfalfa and sorghum could be

effective for phytoremediation of chromium from soil.

In the studies for phytoremediation of chromium must

be mentioned that accumulation of chromium in the

roots is more important than in the shoots.

Karimi

Comparative Phytoremediation of Chromium-Contaminated Soils by Alfalfa (Medicago sativa) and Sorghum bicolor (L)

Moench

47

Table 3: Comparing the extractable chromium in alfalfa and sorghum tissues

Chromium (ppm) in alfalfa Chromium (ppm) in sorghum

T1 (Blank)

Root

0.00a 0.00a

Shoot

0.00a 0.00a

T2 (soil contaminated with 2 mg/kg concentration of chromium)

Root

0.98b 0.86b

Shoot

0.18c 0.15c

T3 (soil contaminated with 4 mg/kg concentration of chromium)

Root

2.73d 2.51d

Shoot

0.92e 0.86e

T4 (soil contaminated with 8 mg/kg concentration of chromium)

Root

4.39f 4.00f

Shoot

1.98g 1.76g

T5 (soil contaminated with 10 mg/kg concentration of chromium)

Root

6.08h 5.71h

Shoot

3.22i 2.91i

+ Numbers followed by same letters in each column are not significantly (P<0.05) different according to the DMR test.

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Karimi

Comparative Phytoremediation of Chromium-Contaminated Soils by Alfalfa (Medicago sativa) and Sorghum bicolor (L)

Moench

49

Nooshin Karimi is a MSc student in soil science, Isfahan (Khorasgan) Branch Islamic Azad University.

Her area of specialization is phytoremediation, bioremediation, and soil pollutions.