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Effects of biochar on growth, and heavy metals accumulation of moso bamboo (Phyllostachy pubescens), soil physical properties, and heavy metals solubility in soil
Accepted Manuscript Effects of biochar on growth, and heavy metals accumulation of Moso bamboo ( Phyllostachy pubescens), soil physical properties, and heavy metals solubility in soil
Ying Wang, Bin Zhong, Mohammad Shafi, Jiawei Ma, Jia Guo, Jiasen Wu, Zhengqian Ye, Dan Liu, Hexian Jin PII:
S0045-6535(18)32266-5
DOI:
10.1016/j.chemosphere.2018.11.159
Reference:
CHEM 22643
To appear in:
Chemosphere
Received Date:
11 July 2018
Accepted Date:
25 November 2018
Please cite this article as: Ying Wang, Bin Zhong, Mohammad Shafi, Jiawei Ma, Jia Guo, Jiasen Wu, Zhengqian Ye, Dan Liu, Hexian Jin, Effects of biochar on growth, and heavy metals accumulation of Moso bamboo (Phyllostachy pubescens), soil physical properties, and heavy metals solubility in soil, Chemosphere (2018), doi: 10.1016/j.chemosphere.2018.11.159
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Effects of biochar on growth, and heavy metals accumulation of Moso bamboo
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(Phyllostachy pubescens), soil physical properties, and heavy metals solubility in
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soil
4 5
Ying Wanga, Bin Zhonga, Mohammad Shafib, Jiawei Maa, Jia Guoc, Jiasen Wua,
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Zhengqian Yea, Dan Liua*, Hexian Jina
7 8
a
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Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University,
State Key Laboratory of Subtropical Silviculture, Key Laboratory of Soil
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Hangzhou, Zhejiang, 311300, P. R. China
11
b Department
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c Zhejiang
of Agronomy, The University of Agriculture, Peshawar, Pakistan
Chengbang Landscape Co., Ltd, 311300, P. R. China
13 14
*Corresponding author:
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Dr. Dan liu
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State Key Laboratory of Subtropical Silviculture, Key Laboratory of Soil
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Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University,
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Hangzhou, Zhejiang, 311300, P. R. China
19
Tel & Fax: +86-571-63740889
20
E-mail: [email protected]
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Abstract
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Pot experiment was conducted to investigate the effects of wood biochar (5%),
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bamboo biochar (5%), rice straw biochar (5%) and Chinese walnut shell biochar (5%)
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on growth, accumulation of heavy metals in moso bamboo, soil physical properties,
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and solubility of heavy metals in soil. The results revealed that dry weight of moso
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bamboo was significantly increased in treatments of wood biochar (5%), rice straw
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biochar (5%) and Chinese walnut shell biochar (5%) except bamboo biochar (5%).
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Application of straw biochar (5%) was most effective in enhancing plants biomass,
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with increase of 157%, 113% and 111% in leaves, roots and stems of moso bamboo.
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All treatments of biochar have significantly improved soil electrical conductivity with
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maximum increase of 360% compared to CK. In case of heavy metals accumulation,
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application of 5% bamboo biochar, straw biochar and Chinese walnut shell biochar
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has reduced Cu uptake in roots by 15%, 35% and 26%, respectively. The biochars
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have significantly reduced solubility of soil heavy metals with maximum reduction of
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58.91 mg·kg-1 and 10.59 mg·kg-1 of Cu and Pb with application of rice straw biochar.
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It is concluded that dry weight of moso bamboo was significantly enhanced by all
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treatments of biochar except bamboo biochar.
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Key words: Biochar; Moso bamboo (Phyllostachys pubescens); Phytoremediation;
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Contaminated
soil;
Heavy
metals
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1 Introduction
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The anthropogenic activities such as metalliferous mining and smelting,
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chemical industry, waste incineration, agricultural activities, and atmospheric
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deposition are the major sources of soil contamination in China (Teng et al., 2014;
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Yan et al., 2015; Zhong et al., 2017). The toxicity of heavy metals has adversely
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affected humans, animals and plants (Mazzei et al., 2014; Abtahi et al., 2017). The
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toxicity of heavy metals may lead to many serious diseases such as blood disorders,
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organ damage and progression of cancer in humans and animals (Conti et al, 2018;
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Chandra et al., 2018; Vinceti et al., 2017; Ferrante et al., 2017). In plants, the toxicity
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of heavy metals may cause chlorosis, necrosis, changes in plant’s phenotype, and
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damage to fundamental organs etc. (Benzarti et al., 2008).
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The use of phytoremediation technology for heavy metal contaminated soils has
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been widely studied in recent years (Cristaldi et al., 2017). The phytoremediation
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technology requires plants with high capacity to accumulate and to transfer heavy
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metals to harvestable upper parts of plants (Benzarti et al., 2008). The synthetic
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chelators and organic acids can improve the activity and solubility of heavy metals.
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The synthetic chelators and organic acids are applied to increase capacity of plants for
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accumulation of heavy metals (Zhang et al., 2018; Quartacci et al., 2006; Tai et al.,
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2018). However, application of synthetic chelators and organic acids may cause
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secondary pollution of environment.
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The biochar, which is produced by thermochemical decomposition of organic
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materials in anaerobic, has been the focus of researchers for the past several years
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(Lehmann and Joseph, 2009; Lehmann et al., 2011; Karaosmanoǧlu and Sever, 2012).
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The biochar has large surface area, and high capacity to adsorb heavy metals and
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organic pollutants which can potentially be used to reduce bioavailability and
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leachability of heavy metals (Zhang et al., 2013). The application of biochar in soil
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has often been reported to have positive effects on plant growth and has significantly
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increased crop yields ( Major et al., 2010; Steiner et al., 2007; Zhang et al., 2017;
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Zhang et al., 2019). The further potential benefit of application of biochar include
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adsorption of dissolved organic carbon (Li et al., 2018b), increases in soil pH and key
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soil macro-elements, and reduction of trace metals in leachates (Novak et al., 2009; Li
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et al., 2018a). Beesley and Dickinson (2010) reported 30 fold increase in water
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concentration of soil pores with associated significant increase in dissolved organic
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carbon and pH with application of biochar and green waste in multi-element polluted
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soils with Cu and As. Whereas Zn and Cd was significantly decreased.
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The application of biochar has produced large biomass in plants of moso bamboo
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with quick growth pattern which can reach 82 t·hm-2 of dry weight in its life cycle
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compared to other phytoremediation plants in multi-contaminated soils (Chen et al.,
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1998; Li et al., 2013; Li et al., 2017). The previous studies have indicated growth
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characteristics and tolerance mechanism of moso bamboo due to adverse effects of
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single heavy metals (Cu, Zn, Cd, Pb) in hydroponics and pot experiments (Chen et al.,
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2016; Li et al., 2016; Liu et al., 2015; Peng et al., 2015). This study has selected four
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kinds of biochar burned from wasted wood, bamboo, rice straw and Chinese walnut
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shell which was applied in same quantity to contaminated soils. The aim of this study
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was to investigate the effects of different kinds of biochars on plant growth,
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accumulation of heavy metals in moso bamboo and solubility of heavy metals in soils.
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This study will provide useful reference and basis for field trials in future to reduce
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toxicity of pollutants (heavy metals) in contaminated soils through technology of
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phytoremediation.
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2 Materials and methods
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2.1 Soil and biochar
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The soil samples were collected from Fuyang county of Hangzhou in Zhejiang
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Province, China (119°53'24"E, 29°53'17"N), where soil has been severely co-
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contaminated with Cd, Cu, Pb and Zn due to industrial activities and soil is not
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suitable for crop growth. The topsoil (0-15 cm) was used for pot experiment. The
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samples were thoroughly mixed, air-dried and passed through a 2 mm stainless steel
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sieve before pot experiment. The soil properties were determined according to
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methods of the Agricultural Chemistry Committee of China (1983). The selected
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physicochemical properties of the soil are presented in Table 1.
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The four kinds of biochar samples, wood biochar (WB), bamboo biochar (BB),
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rice straw biochar (RSB) and Chinese walnut shell biochar (CWSB) were used in this
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experiment. The biochars were produced using continuous slow pyrolysis at final
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temperature of 500 oC with a retention time of 2 h. which was passed through a 2 mm
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stainless steel sieve. The selected physicochemical properties of the biochar samples
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are presented in Table 2.
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2.2 Pot experiments
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The mixed soils after grinding and sieving were put in plastic pots containing
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about 2 kg (dry weight) of polluted soil. The four kinds of biochar at 5% (W/W) of
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doses were added and thoroughly blended with soils, keeping control (CK) without
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any biochar. The single plant of moso bamboo was transplanted in each pot and each
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treatment was replicated three times. The soil moisture content was maintained at
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60% (w/w) of the soil water-holding capacity by adding de-ionized water under the
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pot in plate after every 7 d. The plants were harvested after 160 d of growth. The plant
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and soil samples were analyzed for indicators.
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2.3 Plant harvest and sample analysis
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The harvested plants were thoroughly washed with tap and distilled water and
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were separated in leaves, stems and roots, and then oven dried at 65 oC for 72 h. The
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dried plant materials (100 mg) were powdered and wet digested in 10:1 mixture of
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HNO3:HClO4 at 160 oC. The digested material was diluted with deionized water, and
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heavy metal concentrations were determined using (ICP-OES, Optima 2000,
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PerkinElmer Co., USA).
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The soil samples were collected from pots immediately after harvest and
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analyzed for water-soluble heavy metals by extraction with deionized water (soil-to-
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water ratio of 1:5). The tubes were shaken, for 60 min, centrifuged and filtered to
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collect the supernatants, acidified with HNO3 and analyzed for concentration of
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different heavy metals by ICP-OES. The total concentration of Pb, Zn, Cu and Cd in
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contaminated soil were estimated by digesting with mix acid digestion [1:4]
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concentrated HNO3 and HClO4 (v/v), and then analyzed with ICP-OES (Liu et al.
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2014).
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2.4 Statistical analysis
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Statistical analysis were performed using the SPSS statistical package (version
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21.0). All values reported are the means of three independent replications. Data means
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were tested at significance levels of P<0.05 with one way ANOVA and LSD test. The
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graphical work was carried out with Sigma plot software v.12.5.
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3 Results
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3.1 Effects of biochar on plant growth
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The roots, stems and leaves of moso bamboo as affected by different biochar
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treatments in contaminated soils are presented in Fig.1. The dry weight of moso
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bamboo was increased compared to control in all biochar treatments except
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application of bamboo biochar. The plant growth was enhanced by application of 5%
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rice straw biochar with significant increase of 157% in dry weight of leaves of moso
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bamboo. However, roots biomass failed to show any significant raise after application
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of all four biochar. Moso bamboo biochar was least affective among four biochar in
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term of toxicity alleviation in plants of moso bamboo. The roots and shoots of moso
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bamboo biomass were enhanced only by 4% and 2%, respectively compared to
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control.
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3.2 Effect of biochar on soil pH and EC
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Physical properties of soils were changed when biochar were added to heavy
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metals contaminated soils. The changes in soil pH and EC (Electrical conductivity)
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with biochar amendments are shown in Fig.2. Soil pH was significantly (p<0.05)
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declined by 7% with application of 5% biochar of moso bamboo compared to control.
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However, the pH values have not showed significant change when same quantity of
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other three biochars was applied. The electrical conductivity (EC) of soil was
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increased across all biochar treatments. The extent of increase in electrical
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conductivity was approximately proportional to type of biochar application. The soil
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electrical conductivity was 4.6 times of control soil when rice straw biochar was
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applied. It is revealed that other three biochar treatments have non significant impact
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on soil EC. The soil EC has indicated opposite trend with application of different
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biochar treatments compared to variation in soil pH.
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3.3 Effect of biochar on accumulation of heavy metals in moso bamboo
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Application of different types of biochar showed non significant influence on
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copper contents in roots, stems and leaves of moso bamboo compared to control
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(Fig.3-A). Among four types of biochar, 5% of bamboo biochar, straw biochar and
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Chinese walnut shell biochar has reduced Cu uptake of roots by 15%, 35% and 26%,
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respectively. The Chinese walnut shell biochar was most effective in immobilizing
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heavy metals when 5% of biochar was added to soil, achieving 16% and 7% reduction
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in Cu accumulation in shoots of moso bamboo.
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The Zn accumulation in roots of moso bamboo was increased from 24% to 37%
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at 5% application of all biochars except bamboo biochar (Fig.3-B). Application of
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only wood biochar has reduced Zn concentration in shoots. Zinc concentration in
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roots and shoots were not significantly influenced by application quantity of biochar.
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Zinc was evenly distributed in both shoots and roots, but Cu, Cd and Pb were mainly
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accumulated in roots.
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Application of biochar has reduced Cd concentration in roots, stems and leaves
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of moso bamboo and to some extent, the lowest level of Cd was up to 2.50, 0.40, 0.07
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mg kg-1, respectively (Fig.3-C). The most effective biochar addition were Chinese
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walnut shell biochar and rice straw biochar which has significantly (P<0.05) reduced
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Cd in roots by 77% compared with CK.
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The results showed minimal effects of application of biochar for Pb (Fig.3-D).
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After application of biochar at 5% concentration, the Pb removal by roots of moso
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bamboo plants decreased by 29%~33% compared with CK except for bamboo
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biochar. It has been observed that biochar had no significant effects on Pb uptake in
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roots of plants.
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Cd and Pb uptake quantity by moso bamboo was in the following sequence: rice straw
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biochar>Chinese walnut shell biochar>wood biochar>bamboo biochar.
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3.4 Effect of biochar on soil heavy metal solubility
The comparison of different kinds of biochar revealed that Cu, Zn,
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The concentration of TCLP-extractable Cu, Zn, Cd and Pb in soil was decreased
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significantly (p < 0.05) with application of four kinds of biochar (Fig. 4). The rice
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straw biochar was most effective in heavy metal bioavailability and removal which
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has significantly reduced Cu and Pb in soils, up to 58.91 and 10.59 mg kg-1,
194
respectively. The non significant effects of wood biochar, bamboo biochar and
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Chinese walnut shell biochar treatments on extractable Zn and Cd were observed.
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However, it revealed 21.9%~28.7% and 19.3%~28.3% reduction in Zn and Cd
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compared to CK. The reduction of 21.9%~28.7% and 19.3%~28.3% for Zn and Cd
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TCLP-extractable with application of four biochars was observed. The rice straw
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biochar was more effective than Chinese walnut shell biochar in reducing
200
concentration of soil extractable Cu. The non significant effect of bamboo biochar and
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Chinese walnut shell biochar on reduction of extractable Pb was observed.
202 203
4 Discussions
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Biochar has unique porous structure and abundant oxygen-containing functional
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groups on surface which can immobilize, not only absorb pollutants in soils, but also
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can act as soil conditioner enhancing plant growth by supplying nutrients. In addition
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to that, biochar retain nutrients and improve soil physical and biological properties
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(Glaser et al., 2002; Lehmann and Rondon, 2006; Yuan et al., 2011; Wang et al.,
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2014). In this experiment, the dry weight of moso bamboo was increased in all
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biochar treatments except bamboo biochar compared to control. Straw biochar was
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most effective in enhancing plants biomass when 5% of biochar was added to polluted
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soil. It may be because of biochar could adsorb heavy metal ions on its surface. The
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mobility and effectiveness of soil heavy metals were reduced with addition of biochar.
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In previous studies, moso bamboo has showed moderate stimulation in biomass
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production and chlorophyll content when Zn was applied up to 400 mg kg-1. Our
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results are consistent with previous studies. There may be some potential positive
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influence of Zn on plants growth at lower concentration (Peng et al., 2015). However,
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the impact on plant growth is associated with type and amount of biochar. Jin et al.,
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(2011) revealed
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biomass by 353% and 572% for shoot and roots, respectively. Matovic et al (2011)
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reported that optimum biochar addition in agricultural soils ranged between 1%~5%.
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Oak wood-derived biochar has increased lettuce (Lactuca sativa) seed germination by
223
360% and roots length by 189% in Pb contaminated soils (Beesley et al., 2011; Jin et
224
al., 2011).
that chicken manure-derived biochar(1%) has increased plant dry
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The majority of biochars have liming value when applied to acidic soils which
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can help to enhance soil pH (Beesley and Marmiroli, 2011). The hydrogen ions and
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functional groups combining on surface of biochar were dissociated and then removal
228
rate of heavy metals was gradually increased with raising enhancing pH values.
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Zhang et al., 2013 reported that an increase in soil pH would promote adsorption and
230
precipitation of heavy metals, thereby reducing their bioavailability. However, in this
231
study soil was
232
addition of bamboo biochar but the acidity and alkalinity of the soil have not been
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changed. The other three biochars have non significant (p>0.05) change in pH values
234
compared with control. The electrical conductivity of soil used as soil conditioner was
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generally ranged from 0.4 to 3.2 which is consistent with finding of Lu et al. (2014).
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The four kinds of biochar have significantly increased soil electrical conductivity in
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this study with maximum increase was up to 360% compared to CK. However,
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further research regarding mechanism of soil electrical conductivity and biochar
alkaline, even if the pH values was significantly decreased with
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addition will reveal further useful information.
240
The 5% of bamboo biochar, straw biochar and Chinese walnut shell biochar have
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reduced Cu uptake in roots by 15%, 35% and 26%, respectively. The biochar has
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reduced the trend of uptake of Zn and Pb. The reduction could be attributed to
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precipitation or co-precipitation of heavy metals or adsorption of heavy metals to
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biochar (Elliott et al., 1986; Ahmad et al., 2012). The application of straw
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biochar(5%) has caused significant reduction in Cu and Pb concentration in rice
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shoots (Zheng et al., 2012). Karami et al. (2011) reported that biochar has reduced the
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uptake of Cu and Pb in plants of ryegrass. In this experiment, only addition of
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bamboo biochar has enhanced accumulation of heavy metals in moso bamboo. This
249
may be due to reduction in soil pH which has boosted mobility of heavy metals. The
250
previous research studies conducted in hydroponics and soil as growth media have
251
reported good tolerance to heavy metals and accumulation of heavy metals in roots of
252
moso bamboo. It is likely to be an important protection mechanism of plants in order
253
to prevent the spread of heavy metals. Tshewang et al. (2010) reported significant
254
decrease in Cd concentration in maize shoot with 15 g kg−1 of activated wood biochar.
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All four kinds of biochar have reduced the amount of Cd in shoots and roots with
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maximum reduction of 77% in roots with application of 5% of Chinese walnut shell
257
biochar. This may be due to the fact that Cd was existed from hard-to-dissolved
258
hydroxide, carbonate compound or phosphate form which has reduced accumulation
259
of Cd by plants.
260
The enhancing pH after application of biochar can result in precipitation of Cd as
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CdCO3 , Cu as Cu(OH)2 and Pb as Pb5(PO4)3OH to reduce bioavailability of heavy
262
metals in soils (Mousavi et al., 2010; Cao et al., 2011). The TCLP-extractable of Cu,
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Zn, Cd, and Pb were significantly reduced with application of four types of biochars
264
to soil. The reduction of heavy metals with application of rice straw biochar has
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minimum value of 58.91and 10.59 mg·kg-1 of Cu and Pb. Méndez et al. (2012)
266
revealed that biochar derived from sewage sludge has significantly decreased DTPA-
267
and CaCl2-extractable Cd, Pb and Zn in Mediterranean agricultural soil. Therefore,
268
the application of biochar in contaminated soils will decrease solubility of heavy
269
metals to some extent and will reduce toxicity of plants.
270 271
5 Conclusions
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The dry weight of moso bamboo was significantly improved with application of
273
wood biochar (5%), rice straw biochar (5%) and Chinese walnut shell biochar (5%).
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Application of straw biochar (5%) was most effective in increasing plants biomass.
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All treatments of biochar have significantly improved soil electrical conductivity. The
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biochars have significantly reduced solubility of soil heavy metals with maximum
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reduction of Cu and Pb with application of rice straw biochar. Application of biochars
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have potential to repair soil polluted with low concentration of heavy metals. This
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research study will provide theoretical reference for field trials of future studies.
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Furthermore, in future studies, the effectiveness and mechanism of biochar in
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remediation of contaminated soils should be tested and further studied.
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Acknowledgements
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The study was financially supported through a grant by Natural Science Foundation
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of China (31670617), key research and development project of Science Technology
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Department of Zhejiang province (2015C03020-2) and key research and development
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project of Science Technology Department of Zhejiang province (2018C03028).
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455
ACCEPTED MANUSCRIPT 457
Table 1 Physiochemical properties of growth media (soil) Physiochemical properties pH
7.16
Organic C (g kg-1)
64.9
Available N (mg kg-1)
29.26
Available P (mg kg-1)
3.41
Available K (mg kg-1)
94.0
Total metal concentration (mg kg−1)
458
Pb (mg·kg-1)
370.26
Zn(mg·kg-1)
1905.5
Cu(mg·kg-1)
666.98
Cd(mg·kg-1)
3.21
ACCEPTED MANUSCRIPT 460
Table 2 Physicochemical properties of biochars Wood Property
Biochar (WB)
Total P (g kg−1)
Biochar (BB)
Rice Straw
Chinese Walnut
Biochar
Shell Biochar
(RSB)
(CWSB)
2.3
2.4
2.7
1.8
0.39
0.10
0.16
0.08
pH (H2O)
10.43
9.27
9.71
9.12
Total C (g kg−1)
60.1
880
519
69.4
Total N (g kg−1)
1.2
5.1
17.2
1.6
Total H (g kg−1)
3.7
15.7
18.4
4.8
Corg (g kg−1)
58.9
852
491
66.7
Corg/N
47.5
167
28.5
40.9
Ash (%)
11.97
12.4
41.6
2.7
11.8
16.2
46.7
13.5
219
132
159
80.3
362.4
918.7
38.1
271.5
Total Cd (mg kg−1)
Not detected
Not detected
Not detected
Not detected
Total Cu (mg kg−1)
4.82
15.6
42.3
2.37
Total Pb (mg kg−1)
Not detected
Not detected
3.8
Not detected
Total Zn (mg kg−1)
56.6
30
180
12.4
Electrical conductivity (ds m−1)
Cation exchange capacity (cmol kg−1) Surface alkalinity (cmol kg−1) Specific surface area (BET) (m2 g−1)
461
Bamboo
ACCEPTED MANUSCRIPT
3.5 a'' 3.0
root stem leaf
Biomass (g plant-1)
2.5
a''b''
a 2.0 a 1.5 a 1.0
b'' a'b'
b'' a'b'
a'
a' a''b'' a
a b'
.5 0.0
CK
WB
462
BB Biochar
RSB
CWSB
463
Fig.1 Effect of biochar application on roots, stems and leaves of moso bamboo in pots. Data
464
points and error bars represent mean ± S.D. of three replicates (n=3). Different letters indicate
465
significant difference (P<0.05)
ACCEPTED MANUSCRIPT
10
8
pH EC ab
5 a
ab
pH
c 7
4
3
a
6 5
4
bc
b
b
b
467
2 1
b
CK
EC (mS cm-1)
9
6
WB
BB Biochar
RSB
CWSB
0
468
Fig.2 Effects of biochar treatments on soil pH values and electrical conductivity (EC). Data points
469
and error bars represent mean ± S.D. of three replicates (n=3). Different letters indicate significant
470
difference (P<0.05).
ACCEPTED MANUSCRIPT
300
600 [B]
[A] a
ab
200
root stem leaf
ab
root stem leaf
a
ab
150
a
500
Zn conc (mg kg-1)
Cu conc (mg kg-1)
250
b 100
400 a
a'
300
a' 200
a' a'
50 0
a'
a''b''
CK
a'
a''b''
WB
a' b''
a''b''
BB
RSB
[C]
0
CWSB
a''
a''
WB
BB
RSB
CWSB
a [D]
abc
root stem leaf
12
8 6 4 2
a''b''
CK
bc
a'
a' a'
a''
WB
a''b''
a
BB
c a' b'' RSB
root stem leaf
80
Pb conc (mg kg-1)
ab 10
472
CK
100
a
14
0
a'
a''
a''
a' a''
16
Cd conc (mg kg-1)
a''
100 a'
a
a
60 a a
40
a
20 a'
b''
a' 0
CWSB
a''b''
CK
a' b'' WB
a'
a''b''
BB
a'
a''b''
RSB
a'
a''
CWSB
Biochar
473
Fig.3 Effect of biochar on Cu(A), Zn (B), Cd(C) and Pb (D) accumulation of moso
474
bamboo at the time of harvest in pots experiment. Data points and error bars represent
475
mean ± S.D. of three replicates (n=3). Different letters indicate significant difference
476
(P<0.05).
ACCEPTED MANUSCRIPT
180
1200
a 160
a
[A]
140
b
120
b
100
bc cd
80
d
60
Zn conc (mg kg-1)
Cu conc (mg kg-1)
[B]
1000 b
800
b c
600 400
40 200
20 0 3.5
CK
WB
RSB
0
CWSB
25
a
CK
WB
BB
RSB
b
2.5
[D] 20
b
b
b
Pb conc (mg kg-1)
c
2.0 1.5
CWSB
a
[C]
3.0
Cd conc (mg kg-1)
BB
c
c
15
d 10
1.0 5 .5 0.0
477
CK
WB
BB
RSB
CWSB
0
CK
WB
BB
RSB
CWSB
Biochar
478
Fig.4 Effect of biochar on extractable concentration of Cu(A), Zn (B), Cd(C) and Pb
479
(D) in soil using Toxicity Characteristic Leaching Procedure (TCLP). Data points and
480
error bars represent mean ± S.D. of three replicates (n=3). Different letters indicate
481
significant difference (P<0.05).
482
ACCEPTED MANUSCRIPT Highlights 1 Dry weight of moso bamboo was significantly increased in all treatments of biochar except bamboo biochar. Application of 5% straw biochar was most effective in enhancing plants biomass. 2 Comparison of different kinds of biochar revealed that Cu, Zn, Cd and Pb uptake quantity of moso bamboo was in sequence of: rice straw biochar>Chinese walnut shell biochar>wood biochar>bamboo biochar. 3 Applications of biochar has significantly reduced the solubility of soil heavy metals with maximum reduction of 58.91 and 10.59 mg·kg-1 of Cu and Pb with application of rice straw biochar.
Ying Wang, Bin Zhong, Mohammad Shafi, Jiawei Ma, Jia Guo, Jiasen Wu, Zhengqian Ye, Dan Liu, Hexian Jin PII:
S0045-6535(18)32266-5
DOI:
10.1016/j.chemosphere.2018.11.159
Reference:
CHEM 22643
To appear in:
Chemosphere
Received Date:
11 July 2018
Accepted Date:
25 November 2018
Please cite this article as: Ying Wang, Bin Zhong, Mohammad Shafi, Jiawei Ma, Jia Guo, Jiasen Wu, Zhengqian Ye, Dan Liu, Hexian Jin, Effects of biochar on growth, and heavy metals accumulation of Moso bamboo (Phyllostachy pubescens), soil physical properties, and heavy metals solubility in soil, Chemosphere (2018), doi: 10.1016/j.chemosphere.2018.11.159
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ACCEPTED MANUSCRIPT 1
Effects of biochar on growth, and heavy metals accumulation of Moso bamboo
2
(Phyllostachy pubescens), soil physical properties, and heavy metals solubility in
3
soil
4 5
Ying Wanga, Bin Zhonga, Mohammad Shafib, Jiawei Maa, Jia Guoc, Jiasen Wua,
6
Zhengqian Yea, Dan Liua*, Hexian Jina
7 8
a
9
Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University,
State Key Laboratory of Subtropical Silviculture, Key Laboratory of Soil
10
Hangzhou, Zhejiang, 311300, P. R. China
11
b Department
12
c Zhejiang
of Agronomy, The University of Agriculture, Peshawar, Pakistan
Chengbang Landscape Co., Ltd, 311300, P. R. China
13 14
*Corresponding author:
15
Dr. Dan liu
16
State Key Laboratory of Subtropical Silviculture, Key Laboratory of Soil
17
Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University,
18
Hangzhou, Zhejiang, 311300, P. R. China
19
Tel & Fax: +86-571-63740889
20
E-mail: [email protected]
ACCEPTED MANUSCRIPT 22
Abstract
23
Pot experiment was conducted to investigate the effects of wood biochar (5%),
24
bamboo biochar (5%), rice straw biochar (5%) and Chinese walnut shell biochar (5%)
25
on growth, accumulation of heavy metals in moso bamboo, soil physical properties,
26
and solubility of heavy metals in soil. The results revealed that dry weight of moso
27
bamboo was significantly increased in treatments of wood biochar (5%), rice straw
28
biochar (5%) and Chinese walnut shell biochar (5%) except bamboo biochar (5%).
29
Application of straw biochar (5%) was most effective in enhancing plants biomass,
30
with increase of 157%, 113% and 111% in leaves, roots and stems of moso bamboo.
31
All treatments of biochar have significantly improved soil electrical conductivity with
32
maximum increase of 360% compared to CK. In case of heavy metals accumulation,
33
application of 5% bamboo biochar, straw biochar and Chinese walnut shell biochar
34
has reduced Cu uptake in roots by 15%, 35% and 26%, respectively. The biochars
35
have significantly reduced solubility of soil heavy metals with maximum reduction of
36
58.91 mg·kg-1 and 10.59 mg·kg-1 of Cu and Pb with application of rice straw biochar.
37
It is concluded that dry weight of moso bamboo was significantly enhanced by all
38
treatments of biochar except bamboo biochar.
39 40
Key words: Biochar; Moso bamboo (Phyllostachys pubescens); Phytoremediation;
41
Contaminated
soil;
Heavy
metals
ACCEPTED MANUSCRIPT 42
1 Introduction
43
The anthropogenic activities such as metalliferous mining and smelting,
44
chemical industry, waste incineration, agricultural activities, and atmospheric
45
deposition are the major sources of soil contamination in China (Teng et al., 2014;
46
Yan et al., 2015; Zhong et al., 2017). The toxicity of heavy metals has adversely
47
affected humans, animals and plants (Mazzei et al., 2014; Abtahi et al., 2017). The
48
toxicity of heavy metals may lead to many serious diseases such as blood disorders,
49
organ damage and progression of cancer in humans and animals (Conti et al, 2018;
50
Chandra et al., 2018; Vinceti et al., 2017; Ferrante et al., 2017). In plants, the toxicity
51
of heavy metals may cause chlorosis, necrosis, changes in plant’s phenotype, and
52
damage to fundamental organs etc. (Benzarti et al., 2008).
53
The use of phytoremediation technology for heavy metal contaminated soils has
54
been widely studied in recent years (Cristaldi et al., 2017). The phytoremediation
55
technology requires plants with high capacity to accumulate and to transfer heavy
56
metals to harvestable upper parts of plants (Benzarti et al., 2008). The synthetic
57
chelators and organic acids can improve the activity and solubility of heavy metals.
58
The synthetic chelators and organic acids are applied to increase capacity of plants for
59
accumulation of heavy metals (Zhang et al., 2018; Quartacci et al., 2006; Tai et al.,
60
2018). However, application of synthetic chelators and organic acids may cause
61
secondary pollution of environment.
62
The biochar, which is produced by thermochemical decomposition of organic
63
materials in anaerobic, has been the focus of researchers for the past several years
ACCEPTED MANUSCRIPT 64
(Lehmann and Joseph, 2009; Lehmann et al., 2011; Karaosmanoǧlu and Sever, 2012).
65
The biochar has large surface area, and high capacity to adsorb heavy metals and
66
organic pollutants which can potentially be used to reduce bioavailability and
67
leachability of heavy metals (Zhang et al., 2013). The application of biochar in soil
68
has often been reported to have positive effects on plant growth and has significantly
69
increased crop yields ( Major et al., 2010; Steiner et al., 2007; Zhang et al., 2017;
70
Zhang et al., 2019). The further potential benefit of application of biochar include
71
adsorption of dissolved organic carbon (Li et al., 2018b), increases in soil pH and key
72
soil macro-elements, and reduction of trace metals in leachates (Novak et al., 2009; Li
73
et al., 2018a). Beesley and Dickinson (2010) reported 30 fold increase in water
74
concentration of soil pores with associated significant increase in dissolved organic
75
carbon and pH with application of biochar and green waste in multi-element polluted
76
soils with Cu and As. Whereas Zn and Cd was significantly decreased.
77
The application of biochar has produced large biomass in plants of moso bamboo
78
with quick growth pattern which can reach 82 t·hm-2 of dry weight in its life cycle
79
compared to other phytoremediation plants in multi-contaminated soils (Chen et al.,
80
1998; Li et al., 2013; Li et al., 2017). The previous studies have indicated growth
81
characteristics and tolerance mechanism of moso bamboo due to adverse effects of
82
single heavy metals (Cu, Zn, Cd, Pb) in hydroponics and pot experiments (Chen et al.,
83
2016; Li et al., 2016; Liu et al., 2015; Peng et al., 2015). This study has selected four
84
kinds of biochar burned from wasted wood, bamboo, rice straw and Chinese walnut
85
shell which was applied in same quantity to contaminated soils. The aim of this study
ACCEPTED MANUSCRIPT 86
was to investigate the effects of different kinds of biochars on plant growth,
87
accumulation of heavy metals in moso bamboo and solubility of heavy metals in soils.
88
This study will provide useful reference and basis for field trials in future to reduce
89
toxicity of pollutants (heavy metals) in contaminated soils through technology of
90
phytoremediation.
91 92
2 Materials and methods
93
2.1 Soil and biochar
94
The soil samples were collected from Fuyang county of Hangzhou in Zhejiang
95
Province, China (119°53'24"E, 29°53'17"N), where soil has been severely co-
96
contaminated with Cd, Cu, Pb and Zn due to industrial activities and soil is not
97
suitable for crop growth. The topsoil (0-15 cm) was used for pot experiment. The
98
samples were thoroughly mixed, air-dried and passed through a 2 mm stainless steel
99
sieve before pot experiment. The soil properties were determined according to
100
methods of the Agricultural Chemistry Committee of China (1983). The selected
101
physicochemical properties of the soil are presented in Table 1.
102
The four kinds of biochar samples, wood biochar (WB), bamboo biochar (BB),
103
rice straw biochar (RSB) and Chinese walnut shell biochar (CWSB) were used in this
104
experiment. The biochars were produced using continuous slow pyrolysis at final
105
temperature of 500 oC with a retention time of 2 h. which was passed through a 2 mm
106
stainless steel sieve. The selected physicochemical properties of the biochar samples
107
are presented in Table 2.
ACCEPTED MANUSCRIPT 108
2.2 Pot experiments
109
The mixed soils after grinding and sieving were put in plastic pots containing
110
about 2 kg (dry weight) of polluted soil. The four kinds of biochar at 5% (W/W) of
111
doses were added and thoroughly blended with soils, keeping control (CK) without
112
any biochar. The single plant of moso bamboo was transplanted in each pot and each
113
treatment was replicated three times. The soil moisture content was maintained at
114
60% (w/w) of the soil water-holding capacity by adding de-ionized water under the
115
pot in plate after every 7 d. The plants were harvested after 160 d of growth. The plant
116
and soil samples were analyzed for indicators.
117
2.3 Plant harvest and sample analysis
118
The harvested plants were thoroughly washed with tap and distilled water and
119
were separated in leaves, stems and roots, and then oven dried at 65 oC for 72 h. The
120
dried plant materials (100 mg) were powdered and wet digested in 10:1 mixture of
121
HNO3:HClO4 at 160 oC. The digested material was diluted with deionized water, and
122
heavy metal concentrations were determined using (ICP-OES, Optima 2000,
123
PerkinElmer Co., USA).
124
The soil samples were collected from pots immediately after harvest and
125
analyzed for water-soluble heavy metals by extraction with deionized water (soil-to-
126
water ratio of 1:5). The tubes were shaken, for 60 min, centrifuged and filtered to
127
collect the supernatants, acidified with HNO3 and analyzed for concentration of
128
different heavy metals by ICP-OES. The total concentration of Pb, Zn, Cu and Cd in
129
contaminated soil were estimated by digesting with mix acid digestion [1:4]
ACCEPTED MANUSCRIPT 130
concentrated HNO3 and HClO4 (v/v), and then analyzed with ICP-OES (Liu et al.
131
2014).
132
2.4 Statistical analysis
133
Statistical analysis were performed using the SPSS statistical package (version
134
21.0). All values reported are the means of three independent replications. Data means
135
were tested at significance levels of P<0.05 with one way ANOVA and LSD test. The
136
graphical work was carried out with Sigma plot software v.12.5.
137 138
3 Results
139
3.1 Effects of biochar on plant growth
140
The roots, stems and leaves of moso bamboo as affected by different biochar
141
treatments in contaminated soils are presented in Fig.1. The dry weight of moso
142
bamboo was increased compared to control in all biochar treatments except
143
application of bamboo biochar. The plant growth was enhanced by application of 5%
144
rice straw biochar with significant increase of 157% in dry weight of leaves of moso
145
bamboo. However, roots biomass failed to show any significant raise after application
146
of all four biochar. Moso bamboo biochar was least affective among four biochar in
147
term of toxicity alleviation in plants of moso bamboo. The roots and shoots of moso
148
bamboo biomass were enhanced only by 4% and 2%, respectively compared to
149
control.
150
3.2 Effect of biochar on soil pH and EC
ACCEPTED MANUSCRIPT 151
Physical properties of soils were changed when biochar were added to heavy
152
metals contaminated soils. The changes in soil pH and EC (Electrical conductivity)
153
with biochar amendments are shown in Fig.2. Soil pH was significantly (p<0.05)
154
declined by 7% with application of 5% biochar of moso bamboo compared to control.
155
However, the pH values have not showed significant change when same quantity of
156
other three biochars was applied. The electrical conductivity (EC) of soil was
157
increased across all biochar treatments. The extent of increase in electrical
158
conductivity was approximately proportional to type of biochar application. The soil
159
electrical conductivity was 4.6 times of control soil when rice straw biochar was
160
applied. It is revealed that other three biochar treatments have non significant impact
161
on soil EC. The soil EC has indicated opposite trend with application of different
162
biochar treatments compared to variation in soil pH.
163
3.3 Effect of biochar on accumulation of heavy metals in moso bamboo
164
Application of different types of biochar showed non significant influence on
165
copper contents in roots, stems and leaves of moso bamboo compared to control
166
(Fig.3-A). Among four types of biochar, 5% of bamboo biochar, straw biochar and
167
Chinese walnut shell biochar has reduced Cu uptake of roots by 15%, 35% and 26%,
168
respectively. The Chinese walnut shell biochar was most effective in immobilizing
169
heavy metals when 5% of biochar was added to soil, achieving 16% and 7% reduction
170
in Cu accumulation in shoots of moso bamboo.
171
The Zn accumulation in roots of moso bamboo was increased from 24% to 37%
172
at 5% application of all biochars except bamboo biochar (Fig.3-B). Application of
ACCEPTED MANUSCRIPT 173
only wood biochar has reduced Zn concentration in shoots. Zinc concentration in
174
roots and shoots were not significantly influenced by application quantity of biochar.
175
Zinc was evenly distributed in both shoots and roots, but Cu, Cd and Pb were mainly
176
accumulated in roots.
177
Application of biochar has reduced Cd concentration in roots, stems and leaves
178
of moso bamboo and to some extent, the lowest level of Cd was up to 2.50, 0.40, 0.07
179
mg kg-1, respectively (Fig.3-C). The most effective biochar addition were Chinese
180
walnut shell biochar and rice straw biochar which has significantly (P<0.05) reduced
181
Cd in roots by 77% compared with CK.
182
The results showed minimal effects of application of biochar for Pb (Fig.3-D).
183
After application of biochar at 5% concentration, the Pb removal by roots of moso
184
bamboo plants decreased by 29%~33% compared with CK except for bamboo
185
biochar. It has been observed that biochar had no significant effects on Pb uptake in
186
roots of plants.
187
Cd and Pb uptake quantity by moso bamboo was in the following sequence: rice straw
188
biochar>Chinese walnut shell biochar>wood biochar>bamboo biochar.
189
3.4 Effect of biochar on soil heavy metal solubility
The comparison of different kinds of biochar revealed that Cu, Zn,
190
The concentration of TCLP-extractable Cu, Zn, Cd and Pb in soil was decreased
191
significantly (p < 0.05) with application of four kinds of biochar (Fig. 4). The rice
192
straw biochar was most effective in heavy metal bioavailability and removal which
193
has significantly reduced Cu and Pb in soils, up to 58.91 and 10.59 mg kg-1,
194
respectively. The non significant effects of wood biochar, bamboo biochar and
ACCEPTED MANUSCRIPT 195
Chinese walnut shell biochar treatments on extractable Zn and Cd were observed.
196
However, it revealed 21.9%~28.7% and 19.3%~28.3% reduction in Zn and Cd
197
compared to CK. The reduction of 21.9%~28.7% and 19.3%~28.3% for Zn and Cd
198
TCLP-extractable with application of four biochars was observed. The rice straw
199
biochar was more effective than Chinese walnut shell biochar in reducing
200
concentration of soil extractable Cu. The non significant effect of bamboo biochar and
201
Chinese walnut shell biochar on reduction of extractable Pb was observed.
202 203
4 Discussions
204
Biochar has unique porous structure and abundant oxygen-containing functional
205
groups on surface which can immobilize, not only absorb pollutants in soils, but also
206
can act as soil conditioner enhancing plant growth by supplying nutrients. In addition
207
to that, biochar retain nutrients and improve soil physical and biological properties
208
(Glaser et al., 2002; Lehmann and Rondon, 2006; Yuan et al., 2011; Wang et al.,
209
2014). In this experiment, the dry weight of moso bamboo was increased in all
210
biochar treatments except bamboo biochar compared to control. Straw biochar was
211
most effective in enhancing plants biomass when 5% of biochar was added to polluted
212
soil. It may be because of biochar could adsorb heavy metal ions on its surface. The
213
mobility and effectiveness of soil heavy metals were reduced with addition of biochar.
214
In previous studies, moso bamboo has showed moderate stimulation in biomass
215
production and chlorophyll content when Zn was applied up to 400 mg kg-1. Our
216
results are consistent with previous studies. There may be some potential positive
ACCEPTED MANUSCRIPT 217
influence of Zn on plants growth at lower concentration (Peng et al., 2015). However,
218
the impact on plant growth is associated with type and amount of biochar. Jin et al.,
219
(2011) revealed
220
biomass by 353% and 572% for shoot and roots, respectively. Matovic et al (2011)
221
reported that optimum biochar addition in agricultural soils ranged between 1%~5%.
222
Oak wood-derived biochar has increased lettuce (Lactuca sativa) seed germination by
223
360% and roots length by 189% in Pb contaminated soils (Beesley et al., 2011; Jin et
224
al., 2011).
that chicken manure-derived biochar(1%) has increased plant dry
225
The majority of biochars have liming value when applied to acidic soils which
226
can help to enhance soil pH (Beesley and Marmiroli, 2011). The hydrogen ions and
227
functional groups combining on surface of biochar were dissociated and then removal
228
rate of heavy metals was gradually increased with raising enhancing pH values.
229
Zhang et al., 2013 reported that an increase in soil pH would promote adsorption and
230
precipitation of heavy metals, thereby reducing their bioavailability. However, in this
231
study soil was
232
addition of bamboo biochar but the acidity and alkalinity of the soil have not been
233
changed. The other three biochars have non significant (p>0.05) change in pH values
234
compared with control. The electrical conductivity of soil used as soil conditioner was
235
generally ranged from 0.4 to 3.2 which is consistent with finding of Lu et al. (2014).
236
The four kinds of biochar have significantly increased soil electrical conductivity in
237
this study with maximum increase was up to 360% compared to CK. However,
238
further research regarding mechanism of soil electrical conductivity and biochar
alkaline, even if the pH values was significantly decreased with
ACCEPTED MANUSCRIPT 239
addition will reveal further useful information.
240
The 5% of bamboo biochar, straw biochar and Chinese walnut shell biochar have
241
reduced Cu uptake in roots by 15%, 35% and 26%, respectively. The biochar has
242
reduced the trend of uptake of Zn and Pb. The reduction could be attributed to
243
precipitation or co-precipitation of heavy metals or adsorption of heavy metals to
244
biochar (Elliott et al., 1986; Ahmad et al., 2012). The application of straw
245
biochar(5%) has caused significant reduction in Cu and Pb concentration in rice
246
shoots (Zheng et al., 2012). Karami et al. (2011) reported that biochar has reduced the
247
uptake of Cu and Pb in plants of ryegrass. In this experiment, only addition of
248
bamboo biochar has enhanced accumulation of heavy metals in moso bamboo. This
249
may be due to reduction in soil pH which has boosted mobility of heavy metals. The
250
previous research studies conducted in hydroponics and soil as growth media have
251
reported good tolerance to heavy metals and accumulation of heavy metals in roots of
252
moso bamboo. It is likely to be an important protection mechanism of plants in order
253
to prevent the spread of heavy metals. Tshewang et al. (2010) reported significant
254
decrease in Cd concentration in maize shoot with 15 g kg−1 of activated wood biochar.
255
All four kinds of biochar have reduced the amount of Cd in shoots and roots with
256
maximum reduction of 77% in roots with application of 5% of Chinese walnut shell
257
biochar. This may be due to the fact that Cd was existed from hard-to-dissolved
258
hydroxide, carbonate compound or phosphate form which has reduced accumulation
259
of Cd by plants.
260
The enhancing pH after application of biochar can result in precipitation of Cd as
ACCEPTED MANUSCRIPT 261
CdCO3 , Cu as Cu(OH)2 and Pb as Pb5(PO4)3OH to reduce bioavailability of heavy
262
metals in soils (Mousavi et al., 2010; Cao et al., 2011). The TCLP-extractable of Cu,
263
Zn, Cd, and Pb were significantly reduced with application of four types of biochars
264
to soil. The reduction of heavy metals with application of rice straw biochar has
265
minimum value of 58.91and 10.59 mg·kg-1 of Cu and Pb. Méndez et al. (2012)
266
revealed that biochar derived from sewage sludge has significantly decreased DTPA-
267
and CaCl2-extractable Cd, Pb and Zn in Mediterranean agricultural soil. Therefore,
268
the application of biochar in contaminated soils will decrease solubility of heavy
269
metals to some extent and will reduce toxicity of plants.
270 271
5 Conclusions
272
The dry weight of moso bamboo was significantly improved with application of
273
wood biochar (5%), rice straw biochar (5%) and Chinese walnut shell biochar (5%).
274
Application of straw biochar (5%) was most effective in increasing plants biomass.
275
All treatments of biochar have significantly improved soil electrical conductivity. The
276
biochars have significantly reduced solubility of soil heavy metals with maximum
277
reduction of Cu and Pb with application of rice straw biochar. Application of biochars
278
have potential to repair soil polluted with low concentration of heavy metals. This
279
research study will provide theoretical reference for field trials of future studies.
280
Furthermore, in future studies, the effectiveness and mechanism of biochar in
281
remediation of contaminated soils should be tested and further studied.
282 283
Acknowledgements
284
The study was financially supported through a grant by Natural Science Foundation
285
of China (31670617), key research and development project of Science Technology
ACCEPTED MANUSCRIPT 286
Department of Zhejiang province (2015C03020-2) and key research and development
287
project of Science Technology Department of Zhejiang province (2018C03028).
ACCEPTED MANUSCRIPT 289
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Table 1 Physiochemical properties of growth media (soil) Physiochemical properties pH
7.16
Organic C (g kg-1)
64.9
Available N (mg kg-1)
29.26
Available P (mg kg-1)
3.41
Available K (mg kg-1)
94.0
Total metal concentration (mg kg−1)
458
Pb (mg·kg-1)
370.26
Zn(mg·kg-1)
1905.5
Cu(mg·kg-1)
666.98
Cd(mg·kg-1)
3.21
ACCEPTED MANUSCRIPT 460
Table 2 Physicochemical properties of biochars Wood Property
Biochar (WB)
Total P (g kg−1)
Biochar (BB)
Rice Straw
Chinese Walnut
Biochar
Shell Biochar
(RSB)
(CWSB)
2.3
2.4
2.7
1.8
0.39
0.10
0.16
0.08
pH (H2O)
10.43
9.27
9.71
9.12
Total C (g kg−1)
60.1
880
519
69.4
Total N (g kg−1)
1.2
5.1
17.2
1.6
Total H (g kg−1)
3.7
15.7
18.4
4.8
Corg (g kg−1)
58.9
852
491
66.7
Corg/N
47.5
167
28.5
40.9
Ash (%)
11.97
12.4
41.6
2.7
11.8
16.2
46.7
13.5
219
132
159
80.3
362.4
918.7
38.1
271.5
Total Cd (mg kg−1)
Not detected
Not detected
Not detected
Not detected
Total Cu (mg kg−1)
4.82
15.6
42.3
2.37
Total Pb (mg kg−1)
Not detected
Not detected
3.8
Not detected
Total Zn (mg kg−1)
56.6
30
180
12.4
Electrical conductivity (ds m−1)
Cation exchange capacity (cmol kg−1) Surface alkalinity (cmol kg−1) Specific surface area (BET) (m2 g−1)
461
Bamboo
ACCEPTED MANUSCRIPT
3.5 a'' 3.0
root stem leaf
Biomass (g plant-1)
2.5
a''b''
a 2.0 a 1.5 a 1.0
b'' a'b'
b'' a'b'
a'
a' a''b'' a
a b'
.5 0.0
CK
WB
462
BB Biochar
RSB
CWSB
463
Fig.1 Effect of biochar application on roots, stems and leaves of moso bamboo in pots. Data
464
points and error bars represent mean ± S.D. of three replicates (n=3). Different letters indicate
465
significant difference (P<0.05)
ACCEPTED MANUSCRIPT
10
8
pH EC ab
5 a
ab
pH
c 7
4
3
a
6 5
4
bc
b
b
b
467
2 1
b
CK
EC (mS cm-1)
9
6
WB
BB Biochar
RSB
CWSB
0
468
Fig.2 Effects of biochar treatments on soil pH values and electrical conductivity (EC). Data points
469
and error bars represent mean ± S.D. of three replicates (n=3). Different letters indicate significant
470
difference (P<0.05).
ACCEPTED MANUSCRIPT
300
600 [B]
[A] a
ab
200
root stem leaf
ab
root stem leaf
a
ab
150
a
500
Zn conc (mg kg-1)
Cu conc (mg kg-1)
250
b 100
400 a
a'
300
a' 200
a' a'
50 0
a'
a''b''
CK
a'
a''b''
WB
a' b''
a''b''
BB
RSB
[C]
0
CWSB
a''
a''
WB
BB
RSB
CWSB
a [D]
abc
root stem leaf
12
8 6 4 2
a''b''
CK
bc
a'
a' a'
a''
WB
a''b''
a
BB
c a' b'' RSB
root stem leaf
80
Pb conc (mg kg-1)
ab 10
472
CK
100
a
14
0
a'
a''
a''
a' a''
16
Cd conc (mg kg-1)
a''
100 a'
a
a
60 a a
40
a
20 a'
b''
a' 0
CWSB
a''b''
CK
a' b'' WB
a'
a''b''
BB
a'
a''b''
RSB
a'
a''
CWSB
Biochar
473
Fig.3 Effect of biochar on Cu(A), Zn (B), Cd(C) and Pb (D) accumulation of moso
474
bamboo at the time of harvest in pots experiment. Data points and error bars represent
475
mean ± S.D. of three replicates (n=3). Different letters indicate significant difference
476
(P<0.05).
ACCEPTED MANUSCRIPT
180
1200
a 160
a
[A]
140
b
120
b
100
bc cd
80
d
60
Zn conc (mg kg-1)
Cu conc (mg kg-1)
[B]
1000 b
800
b c
600 400
40 200
20 0 3.5
CK
WB
RSB
0
CWSB
25
a
CK
WB
BB
RSB
b
2.5
[D] 20
b
b
b
Pb conc (mg kg-1)
c
2.0 1.5
CWSB
a
[C]
3.0
Cd conc (mg kg-1)
BB
c
c
15
d 10
1.0 5 .5 0.0
477
CK
WB
BB
RSB
CWSB
0
CK
WB
BB
RSB
CWSB
Biochar
478
Fig.4 Effect of biochar on extractable concentration of Cu(A), Zn (B), Cd(C) and Pb
479
(D) in soil using Toxicity Characteristic Leaching Procedure (TCLP). Data points and
480
error bars represent mean ± S.D. of three replicates (n=3). Different letters indicate
481
significant difference (P<0.05).
482
ACCEPTED MANUSCRIPT Highlights 1 Dry weight of moso bamboo was significantly increased in all treatments of biochar except bamboo biochar. Application of 5% straw biochar was most effective in enhancing plants biomass. 2 Comparison of different kinds of biochar revealed that Cu, Zn, Cd and Pb uptake quantity of moso bamboo was in sequence of: rice straw biochar>Chinese walnut shell biochar>wood biochar>bamboo biochar. 3 Applications of biochar has significantly reduced the solubility of soil heavy metals with maximum reduction of 58.91 and 10.59 mg·kg-1 of Cu and Pb with application of rice straw biochar.