Effects of Three Soil Amendments on Cr (III) Bioavailability in

Cr (III)-contaminated Soil

Pengzhan Lu

1,2,*

, Youyuan Chen

, Bingbing Dong

and Ping Sun

Departments of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China

No. 92609 Unit of PLA, Beijing 100077, China

Keywords:

Soil Amendments, Bioavailability, Cr (III)-Contaminated Soil.

Abstract:

The effect of soil amendments on the bioavailability of heavy metals has been progressively examined both

in the field and under laboratory conditions. To evaluate the effect of three soil amendments, i.e., chicken

manure (CM), peat (PE) and vermiculite (VE) on Cr bioavailability, we planted Lolium perenne (L.

perenne) and Pharbitis purpurea (P. purpurea) in soils contaminated with 1000 mg•kg-1 Cr (III) in the

laboratory. The results showed that all three amendments decreased the bioavailability of Cr (III). Cr (III)

accumulation in L. perenne was most significantly reduced by CM, leading to a Cr (III) concentration that

was only 54.1% of that of the control. CM alleviated Cr (III) stress on the plants, most obviously. Therefore,

CM have the potential to serve as efficient soil amendments for Cr-contaminated soil.

1 INTRODUCTION

Chromium (Cr) contamination in soil is a global

problem that can enter plants and animals through

the food chain and ultimately affect human health

(Gangwar 2011). Therefore, it is urgent to study the

treatment of Cr-contaminated soil. Cr has several

valence states, but Cr (III) is the most abundant

valence state of Cr in soil (Ashraf 2011). Therefore,

studying Cr (III)-contaminated soil is of

significance.

The use of soil amendments to treat heavy

metal-contaminated soils is currently a popular and

environmentally friendly method (Huang 2018,

Liang 2014). Among them, natural soil conditioners

with cheap price and wide sources have greater

prospect and potential (Abd 2015, Habashy 2011).

In previous studies, various natural amendments

such as red mud, lime, and compost were used to

treat heavy metal-contaminated soils (Reijonen

2016, Zhou 2017). Additionally, natural

amendments can greatly affect Cr (III) concentration

and Cr (III) bioavailability in soil (Ke 2012,

Taghipour 2016). The heavy metals bioavailability is

better controlled by organic amendments in soil.

Diverse types of organic materials, such as compost

from the food industry, municipal waste solids, and

manure and agriculture residues, can be used to

remediate the soils contaminated with metals (Qi

2018). It has been reported that organic materials

can decrease the metal availability by improving the

soil pH and via the complexation of the reactive

groups in organic materials (Abbas 2017). In

addition, the functional groups of organic

amendments provide excellent adsorption sites for

binding metals. Therefore, it is necessary to study

the effect of different organic and inorganic

amendments in Cr-contaminated soil.

Extracting Cr from the soil via roots and

translocating plants is complex. The uptake of Cr by

plants and its bioavailability in the soil can be

influenced by several factors, including the plant

type, its concentration in the soil, the soil organic

matter, the pH and the cation exchange capacity

(CEC)

(Khan 2018). Different types of plants have

differing bioaccumulation capacities with respect to

Cr.

The purpose of this study is to (1) study the

effects of the three soil amendments on the

bioavailability of Cr (III) in soil; (2) explore the

differences in uptake, transport and accumulation of

Cr (III) in plants with the three soil amendments.

374

Lu, P., Chen, Y., Dong, B. and Sun, P.

Effects of Three Soil Amendments on Cr (III) Bioavailability in Cr (III)-contaminated Soil.

DOI: 10.5220/0011210000003443

In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 374-378

ISBN: 978-989-758-595-1

2 MATERIALS AND METHODS

2.1 Soil and Amendments

Soil samples were collected from the 0-20 cm

interval of Chromium Salt Factory in Upper

Loushan River, Licang District, Qingdao, China

(36.21°N, 120.39°E). To homogenize the samples,

each sample was completely mixed; then, each

sample was air dried and passed through a 2-mm

sieve. The three soil amendments examined included

chicken manure (CM), peat (PE) and vermiculite

(VE) in this study. Before addition to the soil, the

amendments were ground and passed through a

2-mm mesh. The basic chemical properties of the

experimental soil and amendments are presented in

Tables 1 and 2.

Table 1. The basic chemical properties of the soils.

Pro-

ject

value

Organic

matter

content

/g·kg

-1

CEC

/cmol·kg

-1

Cr(III)

/mg·kg

-1

Cr(T)

/mg·kg

-1

Soil 7.32 10.47 16.48 9.06 9.58

Table 2. The basic chemical properties of the three

amendments.

Amen-

dments

value

Organic

matter

content

/g·kg

-1

total

nitrogen

Cr(T)

/mg·kg

-1

CM 7.87 45.3 20.4 -

PE 6.10 62.4 15.8 -

VE 7.40 - - -

-: indicates not detected.

2.2 Pot Experiment

The experiments in this study were conducted by

potting Lolium perenne (L. perenne) and Pharbitis

purpurea (P. purpurea) with CM and PE(organic

amendments), and an inorganic amendment (VE) in

Cr (III)-contaminated soils. L. perenne and P.

purpurea are more tolerant to Cr when exposed to

Cr (III) levels no greater than 1000 mg·kg

-1

(Chen

2017). Therefore, the concentrations of Cr (III) in

the soil samples were set at 1000 mg·kg

-1

in this

study. Cr was added uniformly in the form of a

CrCl

·6H

O solution and then equilibrated at 25 ℃

for one week in the laboratory.

The three amendments were added to the soil at a

20 mg·kg

-1

application concentration and thoroughly

mixed. Choose plastic pots of suitable size, each

containing 1 kg soil (dry weight, dw). Each

treatment and one control (no treatment) were

prepared in triplicate. Two copies were prepared for

the treatment group, one for L. perenne and another

one for P. purpurea. Irrigated deionized water was

added to the pots equally when needed.

Seeds of L. perenne and P. purpurea were

obtained from Shangpin Landscaping Engineering

Company, Hefei. The seeds were washed with H

and then with deionized water. Then, the seeds were

sown in the selected pots. The pots were kept in a

greenhouse with a controlled environment. After

germination, there were equal numbers of uniform

and healthy seedlings in each pot. All pots were

adjusted daily to a water content of 75% and a field

capacity (FC) of 100% by weight.

2.3 Analysis

Ten grams of treated soil was sampled after 7, 21,

and 35 days; then, the soil was air dried, gently

homogenized with a mortar and analyzed to

determine its chemical parameters.Ten grams soil

samples were taken after one week, three weeks and

five weeks, then air-dried. After gently homogenized

with a mortar, it was used for the analysis of its

physical and chemical properties. The plants were

harvested after 30 days of growth. After rinsing,

plant roots and shoots were dried and ground.

Flame atomic absorption spectrometry was used

to digest and analyze total Cr and Cr (III) in the soil

samples (with detection limits of 5 mg/kg and 2

mg/kg). Determination of Cr concentration after

digestion with 0.5 g powder sample using

-H

according to a literature method

(Parkinson 1975).

The chemical fraction of Cr in the soil was

assessed according to the BCR protocol, which is a

sequential extraction program involving four

steps(Sahuquillo 1999).

2.4 Bioconcentration Factor and

Translocation Factor

The bioconcentration factor (BCF) and translocation

factor (TF) are key indexs used to assess the ability

of a plant species to remediate metal-contaminated

soil. The BCF and TF for Cr in the studied plants

were determined according to a literature

method(Sidhu 2016). The BCF and TF of the plants

were calculated using equations (1) and (2):

CCBCF = (1)

where

C is the Cr(III) concentration in soil

(mg·kg

-1

) and is the concentration in plants

(mg·kg

-1

), and

Effects of Three Soil Amendments on Cr (III) Bioavailability in Cr (III)-contaminated Soil

375

CCTF =

(2)

where

C and

C are the Cr(III) concentrations in

roots and shoots of the plants (mg·kg

-1

2.5 Statistical Analysis

The Statistical Product and Service Solutions

software package was used in the statistical analysis.

One-way analysis of variance (ANOVA) using

Duncan's multiple range test (P = 0.05) was

conducted to determine the statistical significance of

the differences among samples. The correlations

were analyzed by Pearson’s test (two tailed) using

SPSS 20.0 (P < 0.05).

3 RESULTS AND DISCUSSION

3.1 Cr Fraction in Soil

Although the heavy metals concentration is an

important indicator to express the degree of soil

pollution, the toxicity of heavy metals is associated

with their chemical fraction and bioavailability

(Meng 2017). According to the difficulty of

extracting the different Cr chemical fractions, the

harm and degree of toxicity of Cr to the environment

are expressed as acid-soluble > reducible >

oxidizable > residual fractions. Namely B1 > B2 >

B3 > B4. The sum of B1, B2 and B3 represents the

bioavailability content, which poses a potential

threat to organisms (Qiao 2003). Figure 1 shows the

proportion changes of the Cr (III) fractions after

application of the amendments in Cr-contaminated

soil. In each group, B4 was dominant in the initial

stage (7 days) of the incubation experiment, with the

proportions in the Cr (III) fraction ranging from

79.3% to 71.6%. The three soil amendments had

little effect on the fraction of Cr (III), which changed

slowly over time. Only CM reduced the proportions

of B1 + B2 to 66.7% of that of CK in the later stage

(35 days). The contents of Cr (III) in the soil were

influenced by the organic matter contents of CM and

PE. VE played a similar role in soil containing Cr

(III) but showed less of an effect than CM and PE.

The organic matter content in the amendments plays

a certain role in reducing the bioavailability of heavy

metals in soil.

Figure 1: Effect of amendments on the fraction of Cr(III)

in the soil.

Figure

2:Effect of amendments on Cr(III) accumulation in

two plants.

3.2 Cr Accumulation in Plants

The accumulation of Cr (III) in the shoots and roots

of L. perenne and P. purpurea is shown in Figure 2.

In the plant shoots, CM had the most significant

reduction of Cr (III) in the shoots of L. perenne and

P. purpurea, with values of only 55.6% and 68.0%

of those of CK, respectively (Figure 2a). There was

no significant change in Cr (III) accumulation in the

two plants between the PE and CK groups.

The effect of the amendments on the Cr (III)

accumulation in the roots of the two plants is shown

in Figure 2b. The rank order of the three

amendments in terms of reduced Cr (III)

accumulation in the roots of the two plants was CM

> VE > CK > PE. The decrease in the Cr(III)

concentration upon CM treatment was the most

significant and was less than 60% of that of CK (P <

0.05). PE treatments promoted the accumulation of

Cr(III) in the plant roots; the Cr(III) accumulation in

the roots of L. perenne and P. purpurea was 1.2 and

1.1 times higher than that of CK.

ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics

376

3.3 Cr Uptake and Transport in Plants

Under Cr (III) stress, the effects of the three

amendments on the uptake and transport in L.

perenne and P. purpurea are shown in Table 3. The

transport of Cr (III) to the plant shoots was reduced.

PE had the best inhibitory effect on Cr (III) with P.

purpurea, and the TF decreased by 47.1%. The

application of the amendments did not significantly

enhance the BCF of the shoots of the two plants. In

contrast, PE had a significantly positive effect on

Cr(III) enrichment in the roots of L. perenne and P.

purpurea, and the BCF of Cr (III) reached 1.2 and

1.7 times higher than that of CK, respectively.

Table 3. Effects of amendments on Cr (III) TF and BCF

for two plants under Cr (III) stress.

amendments

P. purpurea

BCF

of shoots

BCF

of roots

0.32 0.06 0.20

CM 0.37 0.04 0.11

PE 0.17 0.06 0.34

VE 0.31 0.05 0.18

amendments

L. perenne

BCF

of shoots

BCF

of roots

CK 0.07 0.03 0.37

CM 0.07 0.02 0.21

PE 0.06 0.03 0.43

VE 0.07 0.02 0.31

3.4 Pearson Correlation Analysis of Cr

in Soil and Plants

As described in the above data, the amendments

significantly reduced the B1 and B3 proportions of

Cr (III) in the soil but had little effect on the B2

proportion. To explore the correlation between the

change in the Cr (III) proportion in the soil and the

Cr (III) accumulation in the plants after application

of the three amendments, Pearson’s correlation

analysis of the Cr proportion and Cr (III)

accumulation was performed, and the results are

shown in Table 4. As seen from the table, the

single-factor results showed Cr (III) accumulation in

the plants in the order of B1 > B3 > B2. Usually,

B1+B2+B3 represents the bioavailable heavy metals

in soil(Wang 1997), but in this study, B1+B3 had a

similar or even greater effect than B1+B2+B3. In

addition, the role of B2 was minimal.

Table 4. Pearson correlation analysis for soil Cr forms and

plant Cr contents.

Cr fraction

L. perenne

Cr content

in shoots

Cr content

in roots

Cr content

in plant

B1 0.722

0.704 0.715

B2 0.218 0.377 0.320

B3 0.518 0.512 0.517

B1+B2 0.693 0.705 0.705

B1+B3 0.933

0.914

0.926

B2+B3 0.594 0.629 0.620

B1+B2+B3 0.924

0.931

0.934

Cr fraction

P. purpurea

Cr content

in shoots

Cr content

in roots

Cr content

in plant

B1 0.750

0.440 0.569

B2 0.205 0.240 0.235

B3 0.492 0.755

0.682

B1+B2 0.717

0.442 0.558

B1+B3 0.940

0.848

0.909

B2+B3 0.563 0.804

0.768

B1+B2+B3 0.929

0.847

0.905

The results showed that the amount of available

heavy metals in the soil directly reflected the

absorption of heavy metals by the plants. The

decrease in Cr (III) accumulation in the plants was

the most obvious in the CM group, followed by the

VE group; meanwhile, the PE group promoted the

accumulation of Cr in the plant roots and had the

same level as that in the shoots of the plants in the

CK group. Therefore, the amendments can reduce

the Cr content in the plants by changing the soil Cr

proportion, and the rank order was CM > VE > PE.

In the Cr-contaminated soil, we found that the

content of organic matter in the soil is not the most

important factor affecting the heavy metal

bioavailability, which is slightly different from the

study of(Xiao 2017). This difference may be

because CM and VE can increase the soil pH, which

enhances the chelating ability of the soil to heavy

metal(Reijonen 2016). The bioavailability of heavy

metals can be reduced by stabilization processes,

including surface complexation, cation exchange,

precipitation, and physical adsorption (Li 2017).

4 CONCLUSIONS

In this study, we found that the three amendments

has the improvement for the Cr (III)-contaminated

soil. In this complicated experimental system, The

positive correlation between the chemically

extractable Cr and the Cr taken up by the plants

Effects of Three Soil Amendments on Cr (III) Bioavailability in Cr (III)-contaminated Soil

377

indicates that chemical extractability is a reliable

indicator to predict the bioavailability of Cr in

amended soil. Among the three amendments, CM

has the strongest effect on reducing the

bioavailability of Cr (III).

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