Speciation and Availability of Heavy Metals On Serpentinized Paddy Soil and Paddy Tissue

Speciation and Availability of Heavy Metals On Serpentinized Paddy Soil and Paddy Tissue

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ScienceDirect Procedia - Social and Behavioral Sciences 195 (2015) 1658 – 1665

World Conference on Technology, Innovation and Entrepreneurship

Speciation and Availability of Heavy Metals On Serpentinized Paddy Soil and Paddy Tissue Roslaili Abdul Aziza,*, Sahibin Abd Rahimb, Ismail Sahidb, Wan Mohd Razi Idrisb a School of Environmental Engineering, Universiti Malaysia Perlis, 02600 Jejawi, Perlis, Malaysia. School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.

b

Abstract There has been increasing concern in recent years regarding toxic elements transfer in the soil-plant system. Soils developed on serpentinitic rocks have serious limitations for agriculture. They have high levels of magnesium (Mg) and heavy metals such as nickel (Ni), chromium (Cr), cobalt (Co), and manganese (Mn) and are deficient in some essential macronutrients. The continuous accumulation of serpentine soil downward in the Ranau Valley paddy field brings by excessive erosion and high rainfalls through the main irrigation systems and overflowing flood streams. The presence of serpentine soil contamination is clearly evidenced by oily water and reddish paddy soil. Therefore the basic objective of this work is to examine the availability and mobility of certain elements by assessing the physicochemical properties of paddy soil and the soil-plant interaction as induced by the effect of serpentine. In this study the transfer of abundant metals (Ni, Cr, Co, Fe, Al and Mn) was investigated from a paddy field soils to different parts of Oryza sativa L. (cultivar YTM Sarawak Merah) tissue (root and shoot) through modified metal speciation procedures; that are available and residual fractions. The analyses in nutrient content and heavy metals accumulation in the paddy soil and tissues are reported at the full crop stage through the translocation factor (TF) and bioaccumulation factor (BAF) for a better understanding of the soil-plant system. The heavy metals in the area where potentially bioavailable since the soils are acidic (pH 5.60 – 6.15) which suggested a medium nutrient availability, have a high silt (33.21-69.02), lower clay (13.55-46.98) and sand (7.41-33.44) contents and higher metal concentrations associated with the residual fractions. © by Elsevier Ltd. by This is an open © 2015 2015Published The Authors. Published Elsevier Ltd.access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul University. Peer-review under responsibility of Istanbul Univeristy. Keywords: Oryza sativa L.; Serpentine; Yield; Grain quality; Metals speciation

* Corresponding author. Tel.: +603-89200403 E-mail address: [email protected]

1877-0428 © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul Univeristy. doi:10.1016/j.sbspro.2015.06.235

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1. Introduction Previous study shows that soil geochemistry in the Ranau Valley is controlled primarily by the transport, weathering or pedogenesis process of serpentine rocks where certain minerals inherit from the parent rocks and form some secondary new minerals (Morrison et al., 2009; Tashakor et al., 2011). The worldwide distribution of serpentine or ultramafic rock shows that weathering processes and resulting metal bearing phases differ from position to position due to varying climatic conditions, in the nature of the parent material and to other factors including topography, biota, and time. The chemical weathering of ultramafic rocks (serpentines) under tropical climates noticeably leads firstly to secondary phyllosilicates enriched in Mg, such as serpentine, where Mg is replaced by Ni (garnierite) (Raous et al., 2013) and finally to Mn and Fe oxides. Nickel and Cr(III) can substitute for Mg or Fe in the octahedral sheet in olivine and pyroxene in serpentine minerals (Oze et al., 2007). The lability of Ni and Cr in rocks and soils derived from ultramafic sources in the study area may be a function of the degree of serpentinization. Enrichment of nickel in serpentines ultimately leads to soil toxicity which affecting the poor vegetation in long term. Morrison et al. (2009) recently identified the poor vegetation on serpentine soil is mostly related to Ni toxicity rather than high contents of Cr and Co. The plant uptake of Cr is usually very low while Ni can be taken up by some native herb and crops to elevated amounts. Thus, studying the effect of heavy metal hyperaccumulation on plant health and yield is of great importance. Contrasting to the elevated heavy metal content, serpentinized ultramafic rocks in Ranau having very poor silica with less than 45% SiO2 (Tashakor et al., 2011). A considerable amount of literature has been published on discussing the uniqueness of serpentine edaphic conditions that recognized as infertile. The major limitations to plant growth are variously imposed due to: a) the high levels of nickel, chromium and cobalt, b) the imbalance Mg:Ca ratio, c) magnesium toxicity, and d) low levels of essential plant nutrients such as nitrogen, phosphorus and potassium in the soils (Shim, 2008; Specht et al., 2001; Tashakor et al., 2013). Soils derived from serpentinite also shows tendency to erosion because of the sparse vegetation, which leads to shallow or moderately deep soils with high rock fragment content, high permeability and reduced its water-holding capacity (Frazell et al., 2009). Distribution of heavy metals in soils can provide researchers with evidence of the anthropogenic impact on ecosystems. The accumulation of trace elements and toxic elements in environmental samples (soils and sewage sludges, sediments, etc.) can cause a potential risk to plant, animals and human health due to the transfer of these elements in aquatic media, their uptake by plants and their introduction into the food chain. The fate and behaviour of trace elements in the soil environment are determined by their presence in various chemical forms and their ability to bind with various soil components (Agnieszka & Barbara, 2012). Thus the basic objective of this work is to examine the availability and mobility of certain elements by assessing the chemical properties of paddy soil and the soil-plant interaction as induced by the effect of serpentine. 2. Methodology

2.1. Soil Physicochemical Analyses Surface soil samples (0-20 cm) were collected, air-dried, ground, and passed through a 2-mm sieve for physicochemical analysis in UKM Soil Laboratory. Paddy samples were sampled from the same location simultaneously. 7KHVRLOVDPSOHVIRUKHDY\PHWDOVGHWHUPLQDWLRQZHUHVLHYHGWKURXJKDȝPVWDLQOHVVVWHHOVLHYH Soil pH, particle size, organic matter (OM), and electrical conductivity (EC) were determined to make an accurate assessment of element reservoirs, mobility and bioavailability. Soil pH was measured following Duddridge and Wainwright (Burt, 2004). A 20 g dried soil sample was taken and added to 50 ml of deionized water and mixed for 30 minutes before pH value was taken. pH was measured using a DELTA 320 pH METER. The percentage of soil particle size was measured according to Badri and Aston (1983) by the sieve and pipette method. Organic matter content was determined by loss on ignition technique. A 10 g of soil was transferred to silica crucible, that was

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previously weighed, the crucible with soil was oven dried at 105°C temperature until constant weight obtained, then the crucible was incinerated at a temperature 400 °C overnight before the crucible was cooled and weighed. The procedure was repeated until a constant weight was observed (Jasim et al., 2014). In EC analysis, 10 g oven-dry soil (<2 mm) was placed in a conicle flask. Then 50 ml of saturated CaSO 4 was added and the suspension was shaken manually at 15 min to allow soluble salts to dissolve and ionic exchange to reach equilibrium prior to EC measurements. All analyses were done in triplicates. 2.2. Heavy Metals Extraction For the determination of the soil heavy metal concentrations, the homogenized sample (about 0.5 g) was digested using 0.5 M ammonium acetate-acetic acid for available fraction and HNO 3 -HClO 4 for residual fraction. The purpose of sequential extraction methods to soil samples provides relevant information about possible toxicity when they are discharged into the soil environment. All glassware used for the experiments was previously soaked in 14% HNO, (v/v) and rinsed with deionized water. The residue (from available fraction) was washed with 50 mL of deionized water and later digested with a HNO 3 -HC10 4 mixture. The extractions were conducted in centrifuge tubes (polypropylene, 50 mL) to minimize losses of solid material. Between each successive extraction, separation was effected by centrifuging (Model Biofuge-Stratos) at 3000 rpm for 15 min. The supernatant was filtered using glass microfiber filters GF/C of 47 mm, transferred into plastic bottles and diluted prior analyzed for trace metals using inductively coupled plasma mass spectrometry (ICP-MS). Throughout all analytical work, ultrapure water 0LOOLSRUH0ȍFP ZDVXVHG 2.3. Plant Analysis Paddy plants of cultivar YTM Sarawak Merah, a local variety was harvested at maturity about 5 months after planting and were separated into aboveground (fronds) and below ground (roots) biomass. Roots and shoots were separated in order to obtain information about the ability to accumulate metals in different biomass, washed free of soil with tap water, and rinsed with deionized water to remove the adhering particles. The plant materials were dried in an oven at 70ºC for 72 hours, and then ground into a powder (60 mesh). Rice grains were separated from the straw which was cut 5 cm above the soil. Rice straw was dried for three days at 60°C and milled afterwards. Rice grains were dried at 40°C over night to reduce moisture content in order to prevent fungi infestation, then grains were processed to white rice. Plant samples were digested on hot sand bath with nitric acid and perchloric acid (3:1 ratio) until becoming clear solutions, cooled, filtered and diluted followed by determination of metals concentrations using ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). 3. Results and Discussions 3.1. Soil Physicochemical Characterizations Soil conditions such as pH, cation exchange capacity and organic matter, can highly influence metal assimilation by plant roots, by affecting root growth and the mobility of the pollutants (Ross, 1994). Characterizations of soil samples can be depicted in Table 1. Soil pH of Ranau Valley ranged from 5.87-6.00 (S1), 5.89-6.00 (S2), 5.96-6.08 (S3) and 5.40-6.16 (S4) with total average 5.89, which indicates slightly acidic with medium nutrient availability. Soil pH is a key parameter controlling heavy metal transfer behaviour in soils. Decreasing pH in soils increases the competition between H+ and dissolved metals for ligands such as CO3í, SO42-, Cl-, OH-, S2- and phosphates (Jiengfeng et al., 2009). This increased competition decreases the metal adsorption capacity of soil particles, leading to increased mobility of heavy metals, which ultimately boosts the bioavailability of the metals in the soil. The potential for metal ion leaching is even greater in acid soils (Dijkstra et al., 2004). However the effects of OM on heavy metal fractionation in soil are pH-dependent. Soil samples from study area found to be OM-rich with high percentage in all samples with mean percentage between 11.95% to 13.28%. The

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source of the elevated OM was probably due to periodically returned to the soil either as plant litter or crop residues due to the use of traditional practices of paddy planting in this area. Eventhough such practices possibly to enhance soil fertility or promote soil rehabilitation, organic resources alone often provide insufficient nutrients to build or maintain the long-term nutrient resource base for agriculture (Palm et al., 2001). The electrical conductivity (EC) determined in laboratory through the profiles was around 3.18 to 3.42 mS/cm. Long-term application of chemical fertilizers may change soil pH and EC as well (Wang et al., 2005). The studied soils were assigned to silty clay loam. Determination of particle size shows the dominance of high silt which is between 33.21-69.02, lower clay (13.55 to 46.98) and sand content (7.41 to 33.44), which suggesting the interference of serpentinites soil brought by erosion and transported through two main rivers from higher area, approaching the valley irrigations and continuously deposited into the paddy field. Table 1. Physicochemical of soil samples. Soil Sampl e

pH

OM (%)

EC (mS/cm)

Mean

Max

Min

SD

Mean

Max

Min

SD

Mean

Max

Min

SD

S1

5.93

6.00

5.87

0.06

13.28

13.67

12.94

0.30

3.18

3.31

3.03

0.14

S2

5.95

6.00

5.89

0.06

12.09

12.74

11.71

0.36

3.23

3.34

3.14

0.11

S3

6.02

6.08

5.96

0.06

12.16

12.89

11.13

0.62

3.30

3.34

3.25

0.05

S4

5.68

6.16

5.40

0.42

11.95

13.76

8.87

2.26

3.42

3.46

3.39

0.04

3.2. Heavy Metals Availability and Speciation Serpentine soils are widely distributed in Ranau Valley, Sabah, and generally exhibit high contents of Ni, Cr, Fe, Mn, Co and Mg. Serpentine soils are derived from igneous ultramafic rocks that have high concentrations of magnesium, iron and other metals such as nickel, chromium and cobalt. They are often lacking in major plant nutrients such as nitrogen, phosphorus and potassium, and biomass production depends on one or few limiting nutrients and heavy metal contents (Brooks, 1987; Baker et al., 1992). Therefore the plant communities they support are distinctive. Serpentine vegetation in general appears more xeric, but not because of differences in moisture availability. Rather, limiting nutrient conditions reduce vegetation structure in ways that simulate the effects of drought. Serpentine vegetation shows lower productivity and biomass, and the plant species composition generally differs widely from that found in nearby non-serpentine soils. Many of the species occurring on both do so as different ecotypes (Proctor, 1999; Brady et al., 2005). Metal-wise analysis revealed high metal levels in the sequence of total mean Fe (218937.5 mg kg-1) > Al (79647.2 mg kg-1) > Mn (43063.8 mg kg-1) > Cr (7332.2 mg kg-1) > Ni (6322.3 mg kg-1) > Co (1004.7 mg kg-1) > Zn (597.0 mg kg-1) > Cu (238.6 mg kg-1) > As (15.5 mg kg-1). The literature reported that pH is an important soil property modulating the availability of Ni (Peijnenburg et al.,1999). Lower soil pH possibly increases Ni toxicity to plants grown in soils; where further analysis explained that more Ni would dissolve at lower soil pH (Dan et al., 2008); thus accessible for plant uptake. Elevated soil Ni can exert direct toxicity through accumulation of Ni in plant tissues, and can also exert indirect toxicity through induced nutrient deficiencies, specifically Fe (Marschner, 1995). Moreover, poor crop growth in acid soils can be directly correlated with the degree of Al saturation in the soil and water. The presence of metals in the residual fraction may reflect the natural process of coagulation in soil (Li et al., 2009). Aluminium, chromium, iron, nickel, and cobalt occurred predominantly in the residual fraction (F2), thus showed low mobility. Based on fraction determinations of those metals in the soil, it was potential to evaluate which elements are more mobile than others and thus can be admitted in the biochemical cycle. Rates of extraction of the residual fraction were much higher in Al, Cr, Fe, and Ni than those of available fraction (F1), as shown in Table 2,

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reflecting the extractability of the solutions used. By relating the total mean concentration of heavy metals to Kabata Pendias (2011), all trace metals except Cu were found to be exceeding the maximum allowable concentration (MAC) in soil. This confirmed the influence of serpentine soils into the paddy field area which characterized by the abundance of heavy metal loads.

Table 2. Chemical speciation of heavy metals (mg kg-1) 1

Sample

2

3

4

Heavy Metal

Av

Re

Av

Re

Av

Re

Av

Re

Al

1207.2

90732.5

1320.7

77810.3

1590.8

85673.9

1930.9

58322.3

Cr

714.7

7863.3

728.8

6950.8

774.8

7422.5

859.1

4014.6

Mn

36459.1

2882.1

41346.3

2352.2

45638.4

2212.4

40314.8

1049.8

Fe

1146.6

259465.3

1276.1

230536.8

1066.5

240500.7

3221.2

138536.4

Co

594.7

330.8

773.4

327.7

805.8

278.2

756.1

152.0

Ni

1970.7

4640.5

2527.3

4164.3

2824.0

4341.6

2494.1

2326.6

Cu

130.8

114.2

142.5

101.7

165.7

105.2

125.2

69.1

Zn

377.0

168.9

375.1

183.4

425.5

184.5

543.8

129.7

As

4.2

6.8

3.7

10.5

4.2

15.3

5.0

12.5

Table 3. Total heavy metals concentration (mg kg-1) in soil samples contaminated with serpentine. Soil Sample

Al

Cr

Mn

Fe

Co

Ni

Cu

Zn

1

91939.7

8578.0

39341.2

260611.9

925.4

6611.2

245.1

546.0

2

79131.0

7679.7

43698.5

231813.0

1101.1

6691.6

244.2

558.5

3

87264.7

8197.3

47850.8

241567.3

1084.1

7165.6

270.9

610.0

4

60253.2

4873.7

41364.6

141757.6

908.1

4820.7

194.3

673.5

Mean

79647.2

7332.2

43063.8

218937.5

1004.7

6322.3

238.6

597.0

SD

13970.5

1679.8

3654.4

52824.8

102.0

1030.5

32.0

58.0

MAC

N/A

50-200

N/A

N/A

20-50

20-60

60-150

100-300

3.3. Translocation Factor (TF)

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Copper, Fe, Mn and Zn are essential minerals for plant growth, but Ni, Cr, Co and As are non-essential but toxic to plants at low level and to humans through a food chain. Therefore, it is imperative to estimate the effect of soil properties on the availability and the uptake of heavy metals by plants to minimize the toxic effects and the translocation to food chains (Li et al., 2014). The concentrations of Al, Cr, Mn, Fe, Co, Ni, Cu and Zn in plant tissues (shoots and roots) collected from polluted area are shown in Table 3. The translocation factor of heavy metals translocation from shoot to root was measured by TF which is given below: TF=Cshoot/Croot

(1)

Where Cshoot and Croot are metals concentration in the shoot (mg kg-1) and root of plant (mg kg-1), respectively. TF >1 represent that translocation of metals effectively was made to the shoot from root (Baker and Brooks, 1989; Zhang et al., 2002; Fayiga and Ma, 2006). TF results as shown in Table 3 measured that only Mn (1.28 = S1) and Zn (2.01 = S1, 1.98 = S2, 2.20 = S3, and 2.48 = S4) were being translocated from the root to shoot.

Table 4 . Translocation factor analysis. S1 Mean

Shoot

S2

Root

TF

Shoot

(mg/kg)

Root

S3 TF

Shoot

(mg/kg)

Root

S4 TF

Shoot

(mg/kg)

Root

TF

(mg/kg)

Al

54.58

6781.14

0.01

94.63

7552.82

0.01

115.47

10425.50

0.01

191.09

8974.23

0.02

Cr

15.24

585.06

0.03

19.00

659.06

0.03

23.52

948.66

0.03

41.93

683.95

0.06

Mn

602.37

477.43

1.28

476.91

843.41

0.58

775.40

795.90

0.97

377.61

567.05

0.73

Fe

356.71

33539.08

0.01

241.66

40667.19

0.01

379.00

56655.63

0.01

668.87

49695.28

0.01

Co

2.68

47.77

0.06

2.67

81.36

0.03

5.44

76.09

0.07

1.68

60.46

0.03

Ni

7.59

430.35

0.02

6.91

546.80

0.01

9.97

694.24

0.01

14.65

508.10

0.03

Cu

0.75

11.99

0.06

1.98

13.71

0.14

7.80

22.37

0.34

0.70

15.38

0.04

Zn

37.08

18.34

2.01

44.38

22.39

1.98

61.82

28.74

2.20

55.17

23.60

2.48

3.4. Bioaccumulation Factor (BAF) The ability of plants to deposit trace metals from anthropogenic sources makes them as passive bio-monitors which increased an attention on inorganic pollution (Monaci et al., 2000). The accumulated heavy metals could be transferred to human via consumption of paddy grains, and the deficiency of essential metals or metal overload is harmful for human health. Therefore BAF was used to investigate the ability of metal bioaccumulation in paddy plants. The bioaccumulation factor of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn and As was calculated by: BAF=Cshoot/Csoil

(2)

Where Cshoot and Csoil are metals concentration in the plant shoot (mg kg-1) and soil (mg kg-1), respectively. BAF was categorized further as hyperaccumulators, accumulator and excluder to those samples which accumulated metals > 1 mg kg-1, and < 1, respectively (Ma et al., 2001; Cluis, 2004). BAF results demonstrated that none of the samples collected was a metal accumulator as all of them showed results < 1. Table 5. Bioaccumulation factor analysis.

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Element

BAF S1

S2

S3

S4

Al

0.00

0.00

0.00

0.00

Cr

0.00

0.00

0.00

0.01

Mn

0.02

0.01

0.02

0.01

Fe

0.00

0.00

0.00

0.00

Co

0.00

0.00

0.01

0.00

Ni

0.00

0.00

0.00

0.00

Cu

0.00

0.01

0.03

0.00

Zn

0.07

0.08

0.10

0.09

As

0.89

0.81

0.27

0.24

Boularbah et al. (2006) points out that plant response to heavy metals in soil depends on the plant species, the total metal concentration and the bioavailability of the actual metal depending on the physical and chemical properties of the soil. The combination of elevated soil pH and high organic matter in the study site may have played a sgnificant role in the limited plant availability of heavy metals in the soil, resulting in low plant uptake of these metals (Rosselli et al., 2003). The plant samples analysed in this study showed high levels of tolerance to elevated concentrations of metals in the soil, since the soil concentration in most of sampling locations fell within the toxic range of the metals. 4. Conclusion It was concluded that HM contamination in the agricultural soils was the highest for Fe followed by Mn > Cr > Ni > Co > Zn > Cu, which significantly increase the concentrations of HMs in paddy roots and shoots. This variation was contributed by proximity to the widely covered serpentinized area and the presence of transportation agents. Metals can be transferred to a nearby site through flowing surface water or by wind action. This waterlogged area such as paddy fields therefore exhibits elevated concentrations of metals (Middelkoop, 2000). However, the risk assessment through TF and BAF revealed that there were no health risks in the area for most heavy metals except for Mn and Zn. Acknowledgment The financial assistance for this research work was provided by the Malaysian Ministry of Higher Education, Universiti Malaysia Perlis, and was partly supported by research grant FRGS/2/2013/stwn01/ukm/01/2 . References Agnieszka, J., & Barbara, G. (2012). Chromium, nickel and vanadium mobility in soils derived from fluvioglacial sands. Journal of Hazardous Materials, 237-238, 315–322. doi:10.1016/j.jhazmat.2012.08.048. Badri, M., & Aston, S. 1983. Environmental Pollution Series B, Chemical And Physical, 6 (3), 181- 193. Baker, A. J. M., & Brooks, R. R. (1989). Terrestrial higher plants which hyperaccumulate metallic elements - A review of their distribution, ecology and phytochemistry, Biorecovery, 1, 81-126. Baker, A. J. M., Proctor, J., & Reeves, R. D. (1992). The vegetation of ultramafic (serpentine) soils. Intercepts Ltd., Andover, UK. Boularbah, A., Schwartz, C., Bitton, B., Aboudrar, W., Ouhammou, A., & Morel, J.M., (2006), Heavy metal contamination from mining sites in South Morocco: 2. Assessment of metal accumulation and toxicity in plants, Chemosphere, 63, 811- 817. Brady K.U., Kruckeberg A. R., & Bradshaw Jr. H. D. (2005). Evolutionary ecology of plant adaptation to serpentine soils. Annual Review of Ecology and Systematics, 36, 243-266. Brooks, R. R. (1987). Serpentine and its vegetation. A multidisciplinary approach. DCroom Helm. London and Sydney. Burt, R. (2004). Soil Survey Laboratory Methods, Soil Survey, United States Department Of Agriculture. Cluis C (2004) Junk-greedy greens: phytoremediation as a new option for soil decontamination. Biotechnology Journal, 2, 60–67.

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