Effects of Ground Granulated Blast Furnace Slag (GGBS) on · Draft 1 1 Effects of Ground Granulated Blast Furnace Slag (GGBS) on hydrological responses of Cd 2 contaminated soil planted

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Effects of Ground Granulated Blast Furnace Slag (GGBS) on hydrological responses of Cd contaminated soil planted with

a herbal medicinal plant (Pinellia ternata)

Journal: Canadian Geotechnical Journal

Manuscript ID cgj-2018-0868.R2

Manuscript Type: Article

Date Submitted by the Author: 31-May-2019

Complete List of Authors: Ng, C.W.W.; The Hong Kong University of Science and Technology, Civil and Environmental EngineeringChowdhury, Nilufar; The Hong Kong University of Science and Technology, Civil and Environmental EngineeringWong, James Tsz Fung; The Hong Kong University of Science and Technology, Civil and Environmental Engineering

Keyword: plant growth, soil suction, soil contamination, medicinal plant, cadmium

Is the invited manuscript for consideration in a Special

Issue? :Not applicable (regular submission)

https://mc06.manuscriptcentral.com/cgj-pubs

Canadian Geotechnical Journal

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1 Effects of Ground Granulated Blast Furnace Slag (GGBS) on hydrological responses of Cd 2 contaminated soil planted with a herbal medicinal plant (Pinellia ternata)

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4 Charles Wang Wai NG1, Nilufar CHOWDHURY1, James Tsz Fung WONG1, *

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6 1 Department of Civil and Environmental Engineering, The Hong Kong University of Science

7 and Technology, Clear Water Bay, Kowloon, Hong Kong

8

9 Name: Charles Wang Wai NG

10 Affiliation: Chair Professor, CLP Holdings Professor of Sustainability

11 Tel: (852) 2358 8760

12 E-mail: [email protected]

13 Address: Department of Civil and Environmental Engineering, The Hong Kong University of

14 Science and Technology, Clear Water Bay, Kowloon, Hong Kong

15

16 Name: Nilufar CHOWDHURY

17 Affiliation: Research Assistant

18 Tel: (852) 2358 7166




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23 Name: Dr. James Tsz Fung WONG (*Corresponding author)

24 Affiliation: Post-doctoral Fellow

25 Tel: (852) 9601 7059




29

30 *Compliance with Ethical Standards:

31 The authors would like to declare that they have no conflict of interest, and there were no human

32 nor animal participants in this research.

33

34 A manuscript prepared for the submission to:

35 Canadian Geotechnical Journal

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37 Article type:

38 Research Article

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40 Abstract

41 Pinellia ternata is a medicinal herb often contaminated by cadmium (Cd), which inhibits its

42 growth and metabolism. In this study, the ground granulated blast-furnace slag (GGBS) is

43 proposed as a soil amendment to reduce plant Cd availability and therefore increase transpiration

44 induced suction. Field soil (silty gravelly sand) contaminated with 1.5 mg kg-1 of Cd was

45 collected from Guizhou, China. The growth of P. ternata in 0, 3, and 5% GGBS amended soil

46 has been investigated in a temperature and humidity-controlled chamber. Soil amended with 3

47 and 5% GGBS, significantly (P<0.05) increased leaf area index (LAI) by 29 and 30%, root area

48 index (RAI) by 65 and 66%, respectively, compared to untreated soil. Soil suction was

49 significantly (P<0.05) increased by 58% in soils amended with 3 and 5% GGBS. Compared to

50 control, soil amended with 3 and 5% GGBS has exhibited higher AEV and higher water

51 retention ability. It revealed that addition of GGBS increased soil water availability for plant

52 growth. This implies that to achieve statistically significant improvement in P. ternata growth

53 and soil hydrological responses, 3% GGBS should be applied in Cd contaminated soil.

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55 Keywords: soil contamination; cadmium; plant growth; medicinal plant; soil suction

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56 Introduction

57 Plant growth performance is affected by many abiotic and biotic factors, in particular the

58 presence of environmental stresses such as heavy metal. The effects of heavy metals on the

59 growth of different plant species have been widely investigated and reported (Pulford and

60 Watson 2003). However, the relationships between the presence of heavy metal in soil, plant

61 growth performance, and plant-induced soil hydraulic performance, are rarely reported. In this

62 study, Pinellia ternata has been used as the target plant species. It is an herbal plant that has been

63 using in traditional Chinese medicine for more than 1000 years (Hu and Tao 2005). This plant is

64 often found contaminated by Cd (Peng et al. 2007), as in recent days, most of the cultivated lands

65 in China are contaminated with heavy metals such as Cd, Co, Cr, Cu, Hg, Mn, Pb, Ni, and Zn

66 (Man et al. 2010; Zhong et al. 2017). The soil sample was collected from Guizhou province

67 exhibit Cd contamination which has one of the highest P. ternata cultivable lands in China

68 (Zhang et al. 2013). Cd is one of the most toxic heavy metals which enters in agricultural soils

69 mainly through anthropogenic activities such as the addition of phosphate fertilizer (Nagajyoti et

70 al. 2010, Murtaza et al. 2015). It increases stomatal resistance in most plant species and therefore

71 causing a reduction of the transpiration rate (Barceló and Poschenrieder 1990; Benavides et al.

72 2005). Moreover, Cd affects the physiological and biochemical process in plants such as plants

73 growth, photosynthesis, and transpiration system (Bazzaz et al. 1974; Baszyński et al. 1986;

74 Barceló and Poschenrieder 1990; Benavides et al. 2005). Whereas plant transpiration, plant leaf,

75 and root traits influence evapotranspiration induced soil suction and soil water retention ability

76 (Leung et al. 2015). This implies, reducing Cd uptake in the plant should stimulate plant growth

77 and induce corresponding hydrological changes in Cd contaminated soil.

78

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79 Researchers have adopted different soil heavy metal remediation techniques such as soil

80 solidification, ion exchange, soil washing (Kogbara et al. 2011; Dermont et al. 2008; Ok et al.

81 2011). Application of different soil amendments such as fly ash and quicklime (CaO) (Dermatas

82 and Meng, 2003), red mud and lime (Gray et al. 2006), waste oyster shells (WOS) (Ok et al.

83 2011), farmyard manure (FYM), and lignite (LT) (Rehman et al. 2016) are also widely studied.

84 In addition, phytoremediation has also been adopted to reduce the heavy metal concentration in

85 soil (Hu et al. 2014; Li et al. 2018). Ng et al. (2017) investigated that GGBS as a soil amendment

86 can increase soil pH as well as reduce H2S concentration in soil. GGBS is an industrial by-

87 product that has successfully been used in Cd immobilization previously (Kogbara et al. 2011). It

88 was also effective to immobilize heavy metals in soil (Wang et al. 2018). Although plant induced

89 soil hydrological responses have been studied by many researchers (Ng et al. 2016; Boldrin et al.

90 2017; Ng and Menzies 2007; Ng and Leung 2012), change in plant induced soil hydrological

91 responses after application of these heavy metal remediation techniques are not well understood.

92 With the presence of vegetation, Cd immobilization process in soil becomes complicated due to

93 rhizosphere effects of plants, which may rise Cd availability through continuous acidification

94 and organic acid excretions (Loganathan et al. 2012). Therefore, investigation on Cd

95 immobilization in vegetated soil and corresponding change in soil hydrological responses should

96 carry out. In addition, Wang et al. (2018) investigated that steel slag which composition is

97 comparable to GGBS (Ng et al. 2017) is found to be rich in micronutrient, improves soil quality,

98 and increase rice yield. In this study, GGBS is used as a soil amendment to promote the growth

99 of P.ternata by reducing its Cd uptake in a Cd contaminated soil. However, the performance of

100 GGBS in stimulating plant growth by reducing its Cd uptake and subsequent changes in plant

101 induced hydrological responses of soil are yet to be investigated. Therefore, this study aims to

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102 investigate the effects of GGBS on P. ternata growth by reducing its Cd uptake and

103 corresponding change in plant induced hydrological responses of Cd contaminated soil.

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105 Material and Methods

106 Test plan and selection of optimum percentage of GGBS

107 According to Zhang (2013), pH 6-7.5 is suitable for the growth of P. ternata. It was found

108 that soil amended with 3 and 5% GGBS provide pH 6.4 and 7, respectively (Fig. A1) whereas

109 the soil pH of the control set-up was 4.9. Therefore, 3 and 5% GGBS was selected as the GGBS

110 application percentages for the plant test. In this study, P. ternata was planted in 70% compacted

111 Cd contaminated soil amended with 0, 3 and 5% of GGBS. A relatively low soil density (70%)

112 was adopted for plant root development. For three test conditions with the monitoring of plant

113 characteristics, plant digestions and evapotranspiration induced drying cycle was conducted to

114 investigate GGBS effects on Cd uptake by plants and its influence on plant characteristics and

115 soil hydrological responses.

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117 Test set-up and instrumentation

118 Figure 1 shows the schematic setup of a plant pot. Nine test pots were constructed in total,

119 each having a diameter of 240 mm and a height of 160mm. The soil was compacted in boxes up

120 to 130 mm depth. Six drainage holes each with a diameter of 5 mm were made in the bottom of

121 the pots create a free drainage and side boundaries of the pots were impermeable and the top

122 boundary was exposed to the environment. All test pots were placed in a temperature (25 ± 1°C)

123 and humidity-controlled (60 ± 5%) plant room during the testing period. The light was provided

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124 by the cool white fluorescent lamp that placed on the top of each pot and the intensity was set at

125 approximately 120 µmol m2 s-1 within the 400–700 nm waveband (i.e., equivalent to 5.0 MJ

126 m2day-1). This particular range of waves is known to be favorable for plant photosynthesis (Ng et

127 al. 2016). One small tip tensiometer at depth of 10 mm (above the root zone) and two

128 tensiometers at depths of 50 mm and 90 mm (within root depth zone) were installed just directly

129 beneath plant seeds located in the middle of the pot to minimize any boundary effects on

130 measurements. Since there is the possibility of water cavitation, the maximum suction value that

131 can be measured by tensiometer was between 80–90 kPa (Fredlund and Rahardjo 1993). Three

132 moisture sensors (Decagon EC-5) were installed at 10 mm, 50 mm and 90 mm depths right next

133 to the tensiometer to monitor Volumetric Water Content (VWC) of soil. The purposes of

134 installing moisture sensors were to check the measurements of suction against corresponding

135 VWC and to investigate the effects of GGBS on root growth as well as soil water holding

136 capacity.

137

138 Testing materials and pot preparation

139 Cadmium contaminated field soil was used in this study, which was collected from Bijie city,

140 Guizhou province, China (27°24´N, 105°20´E). According to the Unified Soil Classification

141 System (ASTM, 2011), This field soil can be classified as silty gravelly sand. Based on the

142 results from standard proctor tests, the maximum dry density and the corresponding optimum

143 water content (by dry mass) of the soil are 1776 kg m-3 and 30%, respectively. GGBS was

144 collected from K. Wah Construction Materials Company. Index properties of soil and GGBS are

145 summarized in Table 1. The chemical compositions of soil and GGBS are summarized in Table 2.

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146 All soil used for the pot test was thoroughly mixed. The soil in each plant pot was then

147 compacted by moist tamping at a relative compaction (RC) of 70% (corresponding to the dry

148 density of 1243.2 kg m-3). In each pot, the soil was compacted in 7 layers, with 18 mm each.

149 Between each successive layer, the soil surface was scarified to provide better contact. Plant

150 seeds of P. ternata weighted 4 – 7 grams was selected for each plant pot. Seven seeds were

151 sowed in each pot. In order to take natural variations of seeds into account, each condition was

152 prepared with three replicates (n=3), i.e. nine pots in total were studied.

153

154 Test procedures

155 After sowing, all seeds were grown for 2 months in the plant room. To simulate day and

156 night, the lights were turned on for 12 h and then off for 12 h each day. Irrigation frequency was

157 fixed at 200 ml in a 3 days interval which was sufficient to keep the soil moist to help the plant

158 to grow. All test conditions were subjected to two-stage drying test where a ponding head on the

159 surface was applied to all plant pots until (i) suctions at three depths decreased to 0 kPa, and (ii)

160 percolation through the bottom drainage holes was observed. At second stage test,

161 evapotranspiration induced suctions were recorded to quantify the effects of evapotranspiration

162 on suction by GGBS treated and without GGBS treated test conditions. The drainage holes at the

163 bottom of all the pots were open during the monitoring period. In this case, suction recorded by

164 each tensiometer in the three test conditions was induced by evapotranspiration process of the

165 plant-soil system. During the growth period, the leaf area index (LAI) was measured every 7

166 days. The LAI is a dimensionless index and it is defined as the ratio of the total leaf area to the

167 projected area of the canopy of a single plant on the soil surface in the horizontal plane (Watson

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168 1947). The LAI was calculated using the Image J software (Rasband 2011) based on image

169 analysis technique. In brift, the images of single plant leaves were taken by high- resolution

170 camera. Analyzing these images leaf area was calculated by the software.

171

172 Plants were harvested two months after the growth. They were washed with Mili-Q water to

173 remove dust and soil mineral particles. Plants were dissected into different organs including

174 leaves, stems, tuber, and roots. The Relative Water Content (RWC) of leaves was determined,

175 which is a measurement of its hydration status (actual water content) relative to its maximal

176 water holding capacity at full turgidity. The RWC was determined using the procedure described

177 by Smart and Bingham (1974). A fixed diameter of leaf discs was taken, and the fresh weight

178 was determined. Then the leaf disks were submerged in water for 4 hr, and the weight was

179 recorded, which is defined as turgid weight. The dry weight of leaf tissue was measured by oven-

180 drying the leaves disc to a constant weight at about 85° C using an oven. The RWC was

181 calculated following the equation described below:

182

183 (1) RWC (%) = ((fresh weight -dry weight))/ ((turgid weight -dry weight)) * 100

184

185 The root length and root area index (RAI) of all the plants were determined. The RAI is

186 defined as the ratio of total root surface area for a given depth range to the circular cross-

187 sectional area of soil in the horizontal plane (Francour and Semroud 1992). The RAI is a

188 dimensionless index that indicates the water uptake ability of roots within the root zone. The

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189 plant roots were carefully removed from the plant pots. The maximum root length was defined as

190 the deepest soil depth beyond which no root was found. RAI was calculated according to the

191 method adopted by Francour and Semroud (1992). The weight of a selected segment of roots was

192 measured and the diameter of each root was measured through slide calipers to calculate the

193 surface area of that definite segment of roots. Finally, RAI at any depth within a root zone can be

194 determined by dividing the total outside surface area of roots at a given depth by the planar

195 cross-sectional area of soil.

196

197 To determine the Cd concentration in leaves, stems, tubers, and roots, plant samples were

198 oven dried at 60 °C for 24 h (Liang et al. 1989). After drying, nitric acid digestion of plant

199 materials was conducted to analyze the Cd concentration in different plant organs. Plant

200 digestion was conducted according to Park et al. (2011). Plant sample was grounded and kept in

201 a 25 mL digestion tube. 5 mL concentrated nitric acid was added to the digestion tube and kept

202 in the fume cupboard overnight for cold digestion. With a temperature-controlled digestion block,

203 the samples were heated gradually up to 140°C until only 1 mL digest was left. The samples

204 were then brought to room temperature, diluted with Milli-Q water and filtered with filter paper.

205 The cadmium concentration in the filtered solution was analyzed using an Inductively Coupled

206 Plasma Optical Emission Spectroscopy (ICP-OES).

207

208 Statistical analysis

209 The statistical package SPSS Version 20 (2011) was used for statistical analysis. Significant

210 statistical differences between different data were assessed with one-way ANOVA (analysis of

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211 variance) analyses. To determine the significant differences among the means of treatments post-

212 hoc Tukey’s honestly significant difference (HSD) method was used. Results were considered

213 statistically significant when the P value is less than 0.05, which corresponds to a 95%

214 confidence interval.

215

216 Results and discussion

217 Effects of GGBS on plant characteristics

218 Figure 2 shows the LAI of the plants in three different test conditions where Cd

219 contaminated control soil (without GGBS treated soil), 3% and 5% GGBS amended soil

220 represented by CS, 3% GAS and 5% GAS, respectively. In the figure, it is shown that soil

221 amended with 3 and 5% GGBS significantly (P<0.05) increased LAI by 29 and 33%,

222 respectively, compared to CS. Similar observation was found in the leaf of bean plants. Bean leaf

223 cell expansion get hampered after contacting with 3µM cadmium for 48 h (Poschenrieder et al.

224 1989). Baryla et al. (2001) investigated on leaf expansion growth of B. juncea. The experiment

225 was carried out in 25µM Cd2+ in hydroponic culture where it was observed that after 24 h. of Cd

226 exposure leaf growth rate declined. After 48 h. the growth rate was 25% of the control treatment

227 while after 96 h. leaf growth was stopped due to the toxicity of Cd. According to Poschenrieder

228 et al. (1989) leaves of plants grown with Cd have a higher bulk elastic modulus than control

229 leaves, i.e. their cell walls are less elastic. Decreased cell wall extensibility may be a cause of

230 reduced cell expansion. The cd-induced increase of stomatal resistance and decreased cell

231 expansion causes inhibition of leaf growth (Poschenrieder et al. 1989). In addition, severe

232 reduction of the cell size and decreases in the intercellular spaces in Cd-treated plants also affect

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233 the leaf segment area (Barceló et al. 1988, Skórzyńska-Polit and Baszyński 1995). It shown that

234 3 and 5% GGBS significantly (P<0.05) reduced the cadmium concentration of leaf by 48 and

235 53%, respectively, compared to the control test (Table 3). The reason behind the reduction of Cd

236 concentration in P. ternata can be explained by the sorption mechanism of GGBS. Sorption is

237 attributed to coordination through OH-, Si-Al-O- functional groups (Strawn et al. 2000). ATR-

238 FTIR test indicates GGBS possess of OH-, Si-Al-O- functional groups that can potentially sorb

239 cadmium onto its surface. In addition, GGBS increased the soil pH and results in the

240 precipitation of Cd (Xiao et al. 2017). This implies that GGBS was effective to reduce the Cd

241 stress in plant leaves and therefore causing a significant increment of LAI, compared to CS test

242 condition (control). It should be noted that substantial research work has been conducted to

243 investigate the interactions between soil, heavy metal, and plant growth performance. The

244 complexity of parameters included in each single experiment, such as plant species, soil type,

245 type and concentration of the heavy metal(s) makes the comparable literature limited. Especially

246 the target plant species (P. ternata) in this study is rarely investigated.

247

248 Figure 3 shows the effects of GGBS on root length of P. ternata, where Cd contaminated

249 control soil (without GGBS treated soil), 3% and 5% GGBS amended soil represented by CS, 3%

250 GAS and 5% GAS, respectively. It is observed that soil amended with 3 and 5% GGBS

251 significantly (P<0.05) increased the root length by 37.5% compared to CS soil. Whereas,

252 Wiszniewska et al. (2017) observed two different results for two different species where A.

253 montanum species showed longer root length in 2.5 µM CdCl2 treated medium compared to no

254 Cd treated medium. Another plant species, D. jasminea shorter root length was observed in same

255 Cd treated medium compared to no Cd treated medium. Such response is associated with the

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256 detrimental effect of Cd on root growth. Cd reduces root growth more significantly than that of

257 the shoot. Although the quantity of metal uptake and intensity of root development inhibition

258 may differ with the plant species and the growth condition (Breckle 1991). While according to

259 Barceló and Poschenrieder (1990), metal toxicity can alter the plant root hormonal balance. The

260 negative effect on spatial distribution and reduction of root hair surface cause bad root-soil

261 contact and minimize the capacity of roots to uptake water and nutrients (Barceló and

262 Poschenrieder 1990). It is observed that soil amended with 3 and 5% GGBS significantly

263 (P<0.05) reduced the Cd concentration in root by 63 and 64%, respectively, compared with

264 control (Table 3). Thus, it implies that GGBS was effective in increasing root length by reducing

265 Cd uptake by P. ternata.

266

267 Figure 4 shows the distributions of Root Area Index (RAI) of P. ternata with depth in

268 different test conditions where Cd contaminated control soil (without GGBS treated soil), 3%

269 and 5% GGBS amended soil represented by CS, 3% GAS and 5% GAS, respectively. It is

270 observed that the RAI index of this plant is markedly different from those of the tress. RAI

271 reduced with depth almost linearly. The peak root area index was at depth 50mm where the

272 seeds were shown in beginning. Soil amended with 3 and 5% GGBS significantly (P<0.05)

273 increased the peak root area index of P. ternata by 65 and 66%, respectively, compared with

274 control. Cd induced reduction of root densification and root elongation was observed by many

275 researchers while investigating the effects of Cd on plant (Tukendorf and Rauser 1990; Gunse et

276 al. 1992; Wójicik and Tukendorf 1999; Nocito et al. 2002). Roots of wheat seedlings also

277 showed lower root length and lower root surface area due to Cd toxicity. However, in contrast,

278 Breckle (1991) observed that due to cadmium toxicity root length elongation was affected but the

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279 formation of more lateral roots more compact and lateral root system was observed. therefore, it

280 can be summarized that depending on plant type and tissues these types of variation may occur.

281 Although in the current study the Cd contaminated CS soil was acidic (pH 4.9) and soil pH

282 influence the plant growth significantly. According to Robson (1989), the bacteria that live in

283 association with the roots of legumes get less effective in acidic soil and hamper the nitrogen

284 fixation process. Whereas nitrate can stimulate the root primary and lateral growth of roots

285 (Dong et al. 2018). As GGBS amended soil helps to increase the soil pH so the detrimental effect

286 of acidic soil on RAI gets reduced, hence increase the lateral root formation as well as root

287 elongation.

288

289 Effects of GGBS on water retention behavior of soil

290 Figure 5 shows the drying path of the soil water retention curve (SWRC) of three test

291 conditions where Cd contaminated control soil (without GGBS treated soil), 3% and 5% GGBS

292 amended soil represented by CS, 3% GAS and 5% GAS, respectively. The SWRCs were

293 obtained by relating the measured VWC to suction during the test from three replicates at 50 mm

294 depth where highest RAI was found. The van Genuchten (1980) equation was used to fit the

295 SWRCs and the fitting parameters adopted are summarized in Table 5. The air-entry value (AEV)

296 of the soil in CS, 3% GAS and 5% GAS test conditions are 3 kPa, 5 kPa, and 5 kPa, respectively.

297 Although air entry value is the same for 3% and 5% GAS GGBS amended soil showed higher air

298 entry value compared to CS test condition. For any given suction, 3% and 5% GAS test

299 condition showed higher water retention ability than the CS test. According to Scanlan and Hinz

300 (2010) for a given water content root occupancy in soil pore space can reduce the diameter of

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301 soil pore throat which increases suction according to the capillary law. From figures 3 and 4 it

302 has been showed that soil amended with GGBS significantly increase root length and RAI. The

303 observed increased root length and RAI is responsible for such response of AEV and water

304 retention ability of the soil.

305

306 Effects of GGBS on soil suction and VWC of soil

307 Figures 6 (a) and (b) show the measured suction and VWC during six days of

308 evapotranspiration at 50 mm depth. CS represent control soil whereas 3% GAS and 5% GAS

309 represents vegetated soil treated with 3% and 5% GGBS, respectively. The reason for selecting

310 this particular depth of measurement for investigation is to correlate evapotranspiration-induced

311 suction with peak RAI of the plant which will help to understand the soil-water-root interaction.

312 Soil amended with 3 and 5% GGBS significantly (P<0.05) increased the peak ET-induced

313 suction at 50 mm depth by 58% compared to CS soil. The observed greater increase in suction in

314 the 3% and 5% GAS test conditions were attributed to the greater reduction in VWC

315 (0.05<P<0.1) due to root water uptake (Fig. 6b). Regarding GGBS effect during the drying

316 period, the suction difference between 3% and 5% GGBS was 3-7 kPa initially but the peak ET-

317 induced suction was the same for both conditions. A reduction of the root system size clearly

318 affects water relations of plants, especially on soils of less than field water capacity (Barceló and

319 Poschenrieder 1990). However, Cd influenced plant-water relationship. It reduces the water

320 absorption surface by inhibiting the formation of root hairs. Moreover, according to Barceló and

321 Poschenrieder (1990), heavy metal also reduces the membrane permeability and the number and

322 diameter of vascular bundles. Previous studies showed that there is a direct correlation between

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323 the cadmium concentration and the time dependent inhibition of net photosynthesis and

324 transpiration in corn and sunflower (Bazzaz et al. 1974), tomato seedlings (Jing et al. 2005), and

325 cucumber (Sun et al. 2015) which indicates early effects of cadmium was on stomatal resistance

326 (Perfus-Barbeoch et al. 2002). This implies that the 3% and 5% GAS allowed more root water

327 uptake and transpiration which leads to more ET-induced suction compared to CS test conditions.

328

329 Figure 7 shows the suction profile along depth before and after six days of

330 evapotranspiration induced drying. CS represents control soil whereas 3% GAS and 5% GAS

331 represents vegetated soil treated with 3% and 5% GGBS, respectively. It is shown that the peak

332 ET-induced suction at depth 50 mm in the 3% and 5% GGBS amended soil was 58% (P<0.05)

333 higher respectively compared to the peak ET-induced suction in the CS soil. Suction at depth 10

334 and 90 mm has also increased but the difference was not significant (P<0.05) compared to

335 control treatment. Although soil surface was exposed to the atmosphere, the peak ET-induced

336 suction was observed in 50 mm depth where the higher RAI was found where root water uptake

337 is likely to be greater (Garg et al. 2015). Suction magnitude varies with LAI and RAI.

338 Evapotranspiration was found to be proportional to these two plant traits (Garg et al. 2015).

339 Figures 2 and 4 show that LAI and RAI have significantly increased in 3 and 5% GAS test

340 conditions which results in higher suction. In addition, it is observed that soil amended with 3

341 and 5% GGBS significantly increased relative water content (RWC) of leaves by 16 and 27%

342 (P<0.05), respectively compared with control test (Table 4). Such response of RWC might also

343 represent the higher suction mechanism of GGBS amended soil. The reason is that in a

344 transpiring plant a hydraulic gradient developed between the leaves and the soil in contact with

345 the root system. It causes the transportation of water through the xylem of the plant. 3% and 5%

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346 GAS plants stay under low Cd stress compared to CS (Table 3) and which results in higher RWC

347 in leaves of GGBS amended soil compared to leaves of CS soil. That indicates more water

348 transportation from soil to leaves through xylem of the plants in GGBS amended soil compared

349 to CS soil resulting in higher suction in 3 and 5% GAS. However, studies have revealed that Cd

350 inhibits transpiration, with the hindrance in water flow attributed to hydro-active stomatal

351 closure (Leita et al. 1993; Marchiol et al. 1996) which results in less suction in CS soil compared

352 to GGBS treated soil.

353

354 Effects of GGBS on the correlation between plant traits (LAI, RAI) and peak

355 evapotranspiration induced soil suction

356 Figures 8(a) and (b) show the correlation between leaf Cd concentration, LAI, and suction

357 where CS represents control soil whereas 3% GAS and 5% GAS represents vegetated soil treated

358 with 3% and 5% GGBS, respectively. Figure 8(a) shows a strong negative correlation (R2=0.98)

359 between leaf Cd concentration and LAI. It was observed that in control treatment leaf Cd

360 concentration was 0.24-0.33 mg kg-1 and corresponding LAI was 0.96-1.25. Whereas soil

361 amended with 3 and 5% GGBS show leaf Cd concentration 0.10- 0.21 mg kg-1 and

362 corresponding LAI was 1.32-1.62. This revealed that GGBS has reduced the Cd uptake by plant

363 resulting in lower Cd concentration in leaf. Cd induced inhibition in leaf growth was reduced

364 which results in greater LAI in 3 and 5% GGBS amended soil compared with control. Figure 8

365 (b) shows that there is a strong positive correlation (R2=0.97) between LAI and soil suction. It is

366 observed that in control treatment LAI is 0.96-1.25 and corresponding suction is 13-21 kPa.

367 Whereas soil amended with 3 and 5% GGBS show LAI 1.32-1.62 and corresponding suction is

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368 24-33 kPa. The previous study also observed the positive correlation between LAI and peak ET-

369 induced soil suction (Ng et al., 2016). Higher LAI results in the higher evapotranspiration as the

370 plant individual has more leaf surface area and hence more stomata, to receive more energy for

371 transpiration (Kelliher et al. 1995), which results in higher suction.

372

373 Figures 9(a) and (b) show the correlation between root Cd concentration, RAI, and suction

374 where CS represents control soil whereas 3% GAS and 5% GAS represents vegetated soil treated

375 with 3% and 5% GGBS, respectively. Figure 9(a) shows a strong negative correlation (R2=0.98)

376 between root Cd concentration and RAI. It was observed that in control treatment root Cd

377 concentration was 0.60-0.69 mg kg-1 and corresponding RAI was 0.06-0.09. Whereas soil

378 amended with 3 and 5% GGBS show root Cd concentration 0.18- 0.29 mg kg-1 and

379 corresponding RAI was 0.12-0.16. This revealed that GGBS has reduced the Cd uptake by plant

380 resulting in lower Cd concentration in the root. Although GGBS treated soil reduced the Cd

381 concentration in the root, root Cd concentration was found higher compared to leaf. A similar

382 result was observed by Ramos et al. (2002) where root Cd concentration was 139 mg kg-1 and

383 shoot Cd concentration was 15.7 mg kg-1. Huge difference of Cd concentration between leaf and

384 root showed that a significant constraint of the inside Cd transportation from roots to other

385 organs of plants. However, it is observed that Cd induced inhibition in root growth get reduced

386 which results in greater RAI in 3 and 5% GGBS amended soil compared with control. Figure 9

387 (b) shows that there is a strong positive correlation (R2=0.95) between RAI and soil suction. It is

388 observed that in control treatment RAI is 0.06-0.09 and corresponding suction is 13-21 kPa.

389 Whereas soil amended with 3 and 5% GGBS show RAI 0.12-0.16 and corresponding suction is

390 24-33 kPa. However, Cd disturbs plant–water relationships, causing a direct reduction in the

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391 absorption surface by inhibiting the formation of root hairs, and membrane permeability (Barceló

392 and Poschenrieder 1990). GGBS amended soil reduce the toxicity effect of Cd on root formation

393 which results in greater RAI resulting in higher suction.

394

395 Conclusions

396 This study investigates the effects of GGBS on P. ternata growth and corresponding change

397 in hydrological responses of Cd contaminated soil. This study also exhibited the correlation

398 between Cd concentration in plant leaf and LAI, as well as root Cd concentration and RAI.

399 Correlation between plant traits (LAI, RAI) with peak evapotranspiration induced soil suction

400 was also established.

401

402 Compared to control test, soil amended with 3 and 5% GGBS significantly (P<0.05) reduced

403 Cd concentration in leaf, stem, root and tuber, respectively. Due to the reduction of Cd uptake by

404 P. ternata, improved plant characteristics have been observed. Soil amended with 3 and 5%

405 GGBS, significantly (P<0.05) increases LAI, RAI, and maximum root length. Compared to

406 control treatment. significant (P<0.05) increment of soil suction is observed in both soils

407 amended with 3 and 5% GGBS. Peak suction is found at 50mm depth where peak RAI is

408 observed. AEV value of soil amended with 3 and 5% GGBS increases by 2 kPa which indicates

409 higher water retention ability of GGBS amended soil. A good correlation (R2= 0.98) between

410 leaf Cd concentration and LAI as well as root Cd concentration and RAI was also observed.

411 Positive correlation between plant traits (LAI, RAI) and peak evapotranspiration induced soil

412 suction was also exhibited. This implies that plants in GGBS amended soil experienced lower Cd

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413 stress than control soil which promotes P. ternata growth as well as its induced suction and

414 water retention ability of Cd contaminated soil. In addition, the observed result exhibited non-

415 significant (P>0.05) difference between 3 and 5% GGBS amended the soil. This also implies, to

416 achieve statistically significant improvement in P. ternata growth and soil hydrological

417 responses, soil amended with 3% GGBS should be used. Therefore, application of GGBS in Cd

418 contaminated agricultural field may improve the growth of P. ternata and hence will help to

419 promote soil hydrological responses. This paper indicates that plants growth in Cd contaminated

420 soil can be stimulated by using GGBS, as indicated by the increase in both LAI and RAI. It

421 implies that GGBS can be used to improved plant growth performance and therefore the induced

422 soil suction in contaminated soil. However, it should be noted that GGBS may possesses of trace

423 heavy metal and is not recommended to be applied on farmlands alone. Future study on the

424 combined effects of GGBS and other soil amendments such as biochar on plant growth

425 performance and induced soil suction is needed.

426

427 Acknowledgements

428 The author would like to acknowledge research grant 51778166 funded by National Natural

429 Science Foundation of China.

430

431 References

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List of Tables

Table 1. Index properties of soil and GGBS.

Table 2. Chemical compositions of soil and GGBS.

Table 3. Effects of GGBS on Cd concentration in different organs of P. ternate.

Table 4. Effects of GGBS on Relative Water Content of leaf (RWC) of P. ternate.

Table 5. Summary of fitting parameters for van Genuchten (1980) equation.

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Table 1. Index properties of soil and GGBS

Index properties Unit Soil GGBS

Standard compaction tests

Maximum dry density kg m-3 1776 1500

Optimum moisture content 30 24

Particle size distribution

Gravel content (2-5mm) % 10 N. D¶

Sand content (63µm- 2mm) 80 4

Silt content (20µm - 63µm) 8 16

Clay content (< 20µm) 2 80

D10 0.15 N/AϮ

D30 mm 0.42 N/AϮ

D60 1.2 N/AϮ

Coefficient of uniformity (D60/ D10)

8 N/AϮ

Coefficient of curvature ((D30)2/ (D60 D10)

N/AϮ 0.98 N/AϮ

Specific gravity 2.7 2.9

Atterberg limit

Plastic limit 36 N/AϮ

Liquid limit % 60 N/AϮ

Plasticity index 26 N/AϮ

Soil texture* N/AϮSilty gravelly

sandN/AϮ

* ASTM (2011)

Ϯ N/A= Not Applicable

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¶ N. D.= Not Detected

Table 2. Chemical compositions of soil and GGBS

Chemical compositions Unit Soil GGBS

MgO N.D* 7.20

Al2O

3 25.50 13.50

SiO3 50.35 34.10

SO4 2.60 2.60

K2O 0.77 0.80

CaO 0.42 40.50

TiO2 4.40 0.70

MnO N.D* 0.30

Fe2O

3

Mass

Percentage

(%)

18.50 0.30

* N. D.= Not Detected

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Table 3. Effects of GGBS on Cd concentration in different organs of P. ternata

Cd concentration (mg kg-1)Test ID

Leaf Stem Tuber Root

CS 0.30 ± 0.04a 0.41 ± 0.05 a 0.34 ± 0.04 a 0.68 ± 0.05 a

3% GAS 0.16 ± 0.04b 0.15 ± 0.03 b 0.17 ± 0.05 b 0.25 ± 0.05 b

5% GAS 0.15 ± 0.05 b 0.16 ± 0.05 b 0.15 ± 0.03 b 0.24 ± 0.06 b

Values are mean of 3 replicates. Different lower-case letters indicate that values are significantly different from each other at P < 0.05

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Table 4. Effects of GGBS on Relative Water Content of leaf (RWC) of P. ternata

Test ID Relative water content of leaf (%)

CS 75 ± 4a

3% GAS 87 ± 7b

5% GAS 88 ± 8b

Values are mean of 3 replicates. Different lower-case letters indicate that values are significantly different from each other at P < 0.05

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DraftTable 5. Summary of fitting parameters for van Genuchten (1980) equation

Drying SWRCTest ID ϴs (m3/m3) ϴr (m3/m3) α(m-1) n m

CS 0.35 0 0.03 1.8 1

3% GAS 0.35 0 0.035 2 0.61

5% GAS 0.35 0 0.031 2 0.007

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1

List of Figures

Fig. 1. Schematic diagram of the pot experimental set-up at (a) plan view and (b) cross-section view X–X (c) overview of the test set-up in temperature and humidity-controlled plant room

Fig. 2. The effects of GGBS on the Leaf Area Index (LAI) of P. ternata during the growth period.

Fig. 3. The effects of GGBS on the maximum root length of P. ternata after a 2- month of growth period.

Fig. 4. The effects of GGBS on Root Area Index (RAI) of P. ternata after a 2- month of growth period.

Fig. 5. Measured Soil Water Retention Curves (SWRCs) under different test conditions.

Fig. 6. The effects of GGBS on (a) suction and (b) VWC with time at a depth of 50 mm during evapotranspiration.

Fig. 7. The effects of GGBS on suction profiles before and after six days of drying.

Fig. 8. Relationship of Leaf Area Index (LAI) with (a) leaf Cd concentration (mg kg-1) and (b) peak ET-induced suction (kPa) at a depth of 50 mm under different test conditions.

Fig. 9. Relationship of Root Area Index (RAI) with (a) root Cd concentration (mg kg-1) and (b) peak ET-induced suction (kPa) at a depth of 50 mm under different test conditions.

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2

Fig. 1. Schematic diagram of the pot experimental set-up at (a) plan view and (b) cross-section view X–X (c) overview of the test set-up in temperature and humidity-controlled plant room

(a) (b)

(c)

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3

Time (day)

7 14 21 28 35 42 49 60

Leaf

Are

a In

dex

(LA

I)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

CS3% GAS5% GAS

a

b

c

a

bb

a

bb

b

b b

a

b b

a

bb

a

bb

a

bb

Fig. 2. The effects of GGBS on the Leaf Area Index (LAI) of P. ternata during the growth period. [Mean values are reported with standard deviation (n=3)]. Different lower-case letters indicate that values are significantly different from each other at P < 0.05

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4

Time (day)

0 20 40 60 80 100 120 140

Max

imum

root

leng

th (m

m)

0

50

100

150

200

CS3% GAS5% GASD. jasminea (control) D. jasminea ( Cd treated)A. montanum (control)A. montanum (Cd treated)

a

b

Fig. 3. The effects of GGBS on the maximum root length of P. ternata after a 2- month of growth period. Data of D. jasminea and A. montanum were retrieved from Wiszniewska et al. (2017). [Mean values are reported with standard deviation (n=3)]. Different lower-case letters indicate that values are significantly different from each other at P < 0.05

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Draft

5

Root Area Index

0.00 0.04 0.08 0.12 0.16 0.20D

epth

(mm

)40

50

60

70

80

90

100

110

120

CS 3% GAS 5% GAS

a b b

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

aa

Fig. 4. The effects of GGBS on Root Area Index (RAI) of P. ternata after a 2- month of growth period. Mean values are reported with standard deviation (n=3). Different lower-case letters indicate that values are significantly different from each other at P < 0.05.

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Draft

6

Suction (kPa)

0.1 1 10 100

Vol

umet

ric W

ater

Con

tent

(%)

5

10

15

20

25

30

35

40

CS3% GAS5% GAS

Fig. 5. Measured Soil Water Retention Curves (SWRCs) under different test conditions.

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Draft

7

Time (day)

0 1 2 3 4 5 6 7

Suct

ion

(kPa

)

0

5

10

15

20

25

30

35

CS 3% GAS 5% GAS

a

b

a

b

b

a

b

b

a

b

b

aa

b

bb

b

Time (day)

0 1 2 3 4 5 6 7

Vol

umet

ric w

ater

con

tent

(%)

20

25

30

35

40

CS 3% GAS 5% GAS

a

a

aa a

a

a

a

aa

a

a

a

Fig. 6. The effects of GGBS on (a) suction and (b) VWC with time at a depth of 50 mm during evapotranspiration. Mean values are reported with standard deviation (n=3). Different lower-case letters indicate that values are significantly different from each other at P < 0.05.

(a)

(b)

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Draft

8

Suction (kPa)

0 10 20 30 40D

epth

(mm

)0

20

40

60

80

100

CS_ B3% GAS_ B5% GAS_ B CS3% GAS5% GAS

a a a

a

a

b b

a a

Fig. 7. The effects of GGBS on suction profiles before and after six days of drying. Mean values are reported with standard deviation (n=3). Different lower-case letters indicate that values are significantly different from each other at P < 0.05.

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Draft

9

Leaf Cd concentration (mg kg-1)

0.0 0.1 0.2 0.3 0.4

Leaf

Are

a In

dex

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

CS 3% GAS5% GAS

y= -2.49 x + 1.86R2 = 0.98

Leaf Area Index

0.8 1.0 1.2 1.4 1.6 1.8

Peak

ET-

indu

ced

suct

ion

(kPa

)

10

15

20

25

30

35

CS3% GAS5% GAS

y = 26.36 x - 11.65R2 = 0.97

Fig. 8. Relationship of Leaf Area Index (LAI) with (a) leaf Cd concentration (mg kg-1) and (b) peak ET-induced suction (kPa) at a depth of 50 mm under different test conditions.

(a)

(b)

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Draft

10

Root Cd concentration ( mg kg-1)

0.0 0.2 0.4 0.6 0.8 1.0

Root

Are

a In

dex

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

CS3% GAS 5% GAS

y= -0.142 x + 0.174R2 = 0.98

Root Area Index

0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18

Peak

ET-

indu

ced

suct

ion

(kPa

)

10

15

20

25

30

35

CS3% GAS5% GAS

y = 174.62 x + 3.20R2 = 0.95

Fig. 9. Relationship of Root Area Index (RAI) with (a) root Cd concentration (mg kg-1) and (b) peak ET-induced suction (kPa) at a depth of 50 mm under different test conditions.

(a)

(b)

Page 45 of 47



Draft

1

List of Appendix

Fig. A1. Effects of GGBS on soil pH

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Draft

2

Fig. A-1. Effects of GGBS on soil pH. Lower limit and upper limit correspond to pH 6 and 7.5 (suitable pH range for P. ternata growth).

Page 47 of 47



Documents

Effects of Ground Granulated Blast Furnace Slag (GGBS) on · Draft 1 1 Effects of Ground Granulated Blast Furnace Slag (GGBS) on hydrological responses of Cd 2 contaminated soil planted