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Article

Unlocking the Saponite Potential in Aided Phytostabilisation of Multi-Metal-Contaminated Soils

by
Barbara Klik
1,*,
Martin Brtnicky
2,
Iwona Jaskulska
3,
Mariusz Zygmunt Gusiatin
4,
Dariusz Jaskulski
3,
Jiri Holatko
2,
Tivadar Baltazar
2,
Ernesta Liniauskiene
5 and
Maja Radziemska
1,2,*
1
Institute of Environmental Engineering, Warsaw University of Life Sciences, 02-787 Warsaw, Poland
2
Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of AgriSciences, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic
3
Faculty of Agriculture and Biotechnology, Bydgoszcz University of Science and Technology, 85-796 Bydgoszcz, Poland
4
Faculty of Geoengineering, University of Warmia and Mazury in Olsztyn, 10-719 Olsztyn, Poland
5
Department of Hydrotechnical Engineering, Faculty Environmental Engineering, Kaunas Forestry and Environmental Engineering University of Applied Sciences, Liepu St. 1, Girionys, LT-53101 Kaunas, Lithuania
*
Authors to whom correspondence should be addressed.
Minerals 2023, 13(11), 1354; https://doi.org/10.3390/min13111354
Submission received: 27 September 2023 / Revised: 16 October 2023 / Accepted: 22 October 2023 / Published: 24 October 2023
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
Browse Figures
Versions Notes

Abstract

:
Human activities have significantly impacted the environment, resulting in a need to restore degraded areas through various remediation techniques. This study aimed to evaluate the effectiveness of saponite in the aided phytostabilisation technique for heavy-metal-contaminated soil. The research was conducted on soil from a post-industrial site characterised by high metal content (Cu, Ni, Cd, Pb, Zn, and Cr) surpassing the established regulatory limits. Saponite was added to the contaminated soil at a ratio of 3% (w/w). The experiment was performed using Lolium perenne L. and Festuca rubra L. due to their adaptability to harsh soil conditions and rapid growth. The results demonstrated that saponite application significantly increased soil pH, which is beneficial for phytostabilisation of heavy metals. Saponite has been found to selectively enhance Ni accumulation in roots while not affecting Pb accumulation in above-ground parts, implying that saponite can effectively regulate heavy metal accumulation in plant biomass. Furthermore, saponite has been observed to significantly decrease soil Cd, Zn, and Cr levels with no impact on Cu, Ni, and Pb levels. Overall, saponite shows promise as an effective and scalable solution for large-scale phytostabilisation projects, contributing to the restoration of degraded soils and the protection of environmental and human health.

1. Introduction

In recent years, there has been significant economic growth worldwide, resulting in the production of a considerable amounts of pollutants in the soil. Heavy metals (HMs) are the most common pollutants found in the environment, and while they are naturally occurring, exceeding acceptable levels can be harmful. Soil contamination with HMs can negatively impact biodiversity and increase the risk of contaminant migration. The existence of hazardous substances in the surroundings poses a threat to both humans and animals [1]. Additionally, contamination of the soil with chemicals, like HMs, can harm the living organisms dwelling in the soil. This can result in the loss of sensitive plant species and an overgrowth of resistant organisms, which can disrupt the natural balance of matter and energy flow, ultimately affecting the soil’s proper functioning [2].
To decontaminate the soil properly, the first step involves determining the level of contamination and then selecting the appropriate method for removing it. While it is ideal to permanently eliminate contaminants from the soil, this can be quite expensive and generate a significant amount of waste. Additionally, it can be challenging to carry out and monitor the cleaning processes [3]. In instances where the uppermost layer of soil is tainted or rapid containment of a contaminated region is imperative, stabilisation techniques that entail the implementation of mineral–organic soil additives are utilised [4,5]. One effective technique for reducing heavy metal mobility in soil is to modify its properties, specifically by adjusting the soil’s pH level and its absorption capabilities. This can be achieved through the addition of materials that possess a high sorption capacity or by maintaining a neutral pH level. During the process of stabilising HMs, various methods are employed, such as sorption, ion exchange, redox reactions, and the formation of stable complexes with organic ligands. These processes lead to a reduction in the amount of available metal. By creating internal or external complexes with reactive groups present in the soil, the metals become immobilised on the soil matrix [6,7]. Notably, this method offers a range of benefits, including minimal environmental impact, ease and efficiency of application, and cost effectiveness. The addition of stabilising material alone may not always result in improved soil quality. Therefore, various methods have been integrated to enhance effectiveness. One such approach gaining recognition is aided phytostabilisation, whereby both soil additives and vegetation are introduced to soil contaminated with metals [8,9,10].
The roots of plants have the ability to release compounds that can effectively immobilise HMs present in the soil, leading to a range of benefits that complement those provided by soil additives. These metals tend to be adsorbed onto the surface of roots, accumulate within the roots themselves, or precipitate in the rhizosphere. In addition, organic compounds and carbon dioxide are also released into the rhizosphere, resulting in alterations to the soil’s pH and oxidation reduction potential, as well as conversion of toxic metal forms into more stable ones. This process, in turn, prevents the metals from moving into deeper soil layers, water sources, and the atmosphere, thereby ensuring a safer and more sustainable ecosystem [11,12].
To effectively execute the process, it is necessary to utilise plants capable of withstanding harsh soil conditions, such as low pH levels or high concentrations of HMs, while also demonstrating a rapid growth rate. Furthermore, these plants must produce a significant amount of biomass to establish complete vegetation coverage across the soil surface, thereby reducing the volume of water penetrating into the soil matrix. This step is crucial for preventing the creation of hazardous leachates [13]. Notably, members of the Poaceae family, such as Festuca rubra L. and Lolium perenne L., have been highly effective in establishing vegetation cover in contaminated areas [6,14,15,16,17].
The process of utilising plant material is further enhanced through the incorporation of soil additives that possess the ability to form stable complexes with HMs. Despite the achievements in using various materials, like silicates, active carbon, zeolite, kaolinite, bentonite, and montmorillonite, for environmental applications [6,18,19,20,21,22], there is still a need to explore and discover new types of materials. This arises from the recognition of certain limitations and drawbacks associated with the current materials, such as their limited efficiency in specific soil conditions, potential environmental concerns, and cost considerations. The search for novel materials is essential to address these challenges and further enhance the effectiveness and sustainability of soil stabilisation and phytostabilisation techniques.
Saponite, classified as a member of the smectite mineral group, is one such material that holds promise in aiding phytostabilisation efforts. Saponite is a phyllosilicate clay mineral known for its lamellar structure, which gives it a high specific surface area and cation exchange capacity [23]. Saponite is often found in hydrothermal alteration environments, as well as in marine sediments and certain weathered volcanic rocks [24,25]. Due to its unique properties, saponite has been widely used in various applications in agriculture [23], where it has been used as an ameliorant [26].
In the context of aided phytostabilisation of heavy-metal-contaminated soils, saponite has the potential to influence soil acidity and the contents of biogenic elements, such as nitrogen, phosphorus, and potassium [23]. Its high specific surface area, combined with active surface groups, make it an ideal substance for absorbing and immobilising HMs commonly found in contaminated soils.
However, despite numerous studies on the application of saponite in agriculture, no studies determining its usefulness in the soil stabilisation process in soils derived from post-industrial sites contaminated with HMs have been carried out so far. From a scientific and practical point of view, it is important to determine the effectiveness of this process as well as the interaction between different soil additives and plants. Additionally, in natural environments, HMs often occur as mixtures rather than individual elements. Therefore, investigating the impact of saponite on a mixture of six HMs provides valuable insights into its potential as an effective remediation agent in real-world scenarios. The evaluation of saponite’s performance on multiple HMs simultaneously enhances the practical applicability of this technology for tackling complex soil pollution challenges. Therefore, this study aims to determine the effectiveness of applying saponite in technologies of aided phytostabilisation, including the influence on crop yield and heavy metal contents (Cu, Ni, Cd, Pb, Zn, and Cr) in the above-ground biomass and roots of the tested plants, as well as in the contaminated soil. To assess the possibility of HMs being absorbed by living organisms, an investigation into the exchangeable types of HMs was also conducted. Our findings will serve as a valuable resource for future research endeavours and aid in the identification and mitigation of potential health and environmental hazards.

2. Materials and Methods

2.1. Soil Characteristics

The soil material used for the experiment was taken from post-industrial sites located in central Poland. The selected research area had a history of industrial activities involving steel, metals, and other types of metal waste. The surface layer of the soil (0–25 cm) was collected from 20 sampling sites in a 200 m2 area in the oldest part of the scrap yard. The sampling sites were selected for equal coverage of the area. At each sampling site, 5 kg of soil was collected with a stainless-steel shovel, following conventional methods in accordance with ISO standards [27]. Upon collection, the samples were mixed to create a representative composite sample that accurately reflected the quality and quantity of the material.
The collected soil material was then transported to the laboratory in a sealed container. In the lab, it was air-dried, ground, and passed through a 2 mm diameter sieve to prepare the samples for analysis of heavy metal contents. The analysed soil material exhibited high concentrations of HMs, with levels exceeding the established standards [28]. Particularly, the concentrations of Pb and Zn significantly deviated from the norm (over 25 times and 8 times higher, respectively). However, the concentration of Ni met the standards for soil quality, though its analysis remained crucial as it could influence the efficiency of removing fewer mobile metals. The concentrations of HMs in the contaminated soil, along with the standard values, have been presented in Table 1.

2.2. Saponite Characteristics

The present study involved the use of saponite, a monoclinic crystal structure clay mineral belonging to the smectite group, as a soil additive. The particular saponite utilised was procured from a reputable Ukrainian company, Veles, situated in the Khmelnitsky region, and marketed under the brand name Saprokorm. The chemical formula of the saponite obtained was Mg3(Si4O10)(OH)2·nH2O. To ensure a consistent structure, the saponite was dried in a laboratory drier at a temperature of 105 °C. The prepared material was then stored in a sealed container until the time of conducting the experiment. The key characteristics of the mineral have been presented in Table 2.

2.3. Experiment Design

The experiment of aided phytostabilisation was conducted with five repetitions in polyethene pots, using the soil described earlier mixed with saponite at a ratio of 3% (w/w). The control group consisted of only the contaminated soil without any additives. The soil–saponite mixture was incubated in the dark for 14 days to ensure a homogeneous blend. Subsequently, the soil was transferred to individual pots, with each pot containing 5 kg of the prepared mixture. Lolium perenne L. and Festuca rubra L. seeds (5 g) were sown in the pots. The seeds used in the experiment were obtained from an authorised Seed Production Center in Olsztyn, Poland (OLZNAS-CN Sp. z o.o.).
The pots were placed in a greenhouse with a temperature of 26 ± 3 °C during the day and 16 ± 2 °C at night, with an average exposure to sunlight lasting 14 h. The experiment was conducted over a 56-day period. After this period, the above-ground biomass (shoots) and roots of the plants were collected and carefully washed with tap water, followed by distilled water. The collected biomass was then dried and divided into separate samples of shoots and roots. Upon completing the experiment, heavy metal analysis was carried out for both the soil and plant biomass to assess the levels of metal accumulation.

2.4. Analytical Methods

The soil was ground using a soil grinder (H-4199.5F, Humboldt Mfg. Co., Elgin, IL, USA) and sieved with a vibrating sifter equipped with an electromagnetic drive (Retsch AS200, Hann, Germany) using a 2 mm diameter sieve. Measurements of soil mass, seeds, and plant biomass were conducted on an analytical scale (Acculab ATL-623-V, Sartorius, Goettingen, Germany).
To determine the concentration of HMs (Cu, Ni, Cd, Pb, Zn, and Cr), flame absorption atomic spectrometry was employed with an AA280FS spectrometer (Varian, AA28OFS, Mulgrave, Australia) equipped with an automatic sample introduction and dissolution system (SIPS). Prior to analysis, the samples underwent mineralisation using a mixture of concentrated HCl and HNO3 acids in a MARS microwave oven (MARSXpress, CEM Corporation, Matthews, NC, USA). The calibration curve was prepared using TraceCERT® heavy metal standards for FAAS (Sigma-Aldrich, Merck KGaA, Darmstadt, Germany). The appraisal of the quality analysis was conducted using CRM 142 R, and the recoveries obtained exhibited a range of 95% to 101%. The limits of detection (LOD) for each metal were 0.34, 0.21, 0.03, 1.30, 0.73, and 0.18 mg/L for Cu, Ni, Cd, Pb, Zn, and Cr, respectively. The limits of quantification (LOQ) were 0.88, 0.61, 0.12, 1.09, 3.14, and 0.45 mg/L for Cu, Ni, Cd, Pb, Zn, and Cr, respectively. The calculation method outlined in Gusiatin et al. [29] and Gusiatin et al. [30] was utilised to determine the overall metal concentration in this study.
For the measurement of metal content in exchangeable forms (exchangeable CaCl2), the methodology developed by Pueyo et al. [31] was employed. Briefly, a soil extractant consisting of a 0.01 M solution of CaCl2 in a 1:10 ratio was added to the soil. The resulting mixture was shaken for 2 h at 20 °C before being centrifuged. The metal content in the resulting supernatant was then measured using flame absorption atomic spectrometry.

2.5. Statistical Analysis

Statistical analyses were carried out using R software (the R Project for Statistical Computing, version 4.2.2.) [32]. The normality of the distribution was established using the Shapiro–Wilk test, though statistically significant differences for average values of HMs prior to and following the experiment were determined using one-way analysis of variance (ANOVA) as well as Tukey’s test, at a level of significance level amounting to 5%.

3. Results and Discussion

3.1. Soil pH and Plant Biomass

The experiment on aided phytostabilisation, using saponite as a soil additive to address metal contamination, led to alterations in soil pH and plant biomass. These findings are illustrated in Figure 1.
The introduction of saponite into the soil resulted in a notable increase in pH levels, rising from a baseline of 7.2 to 8.5. This finding is consistent with prior research indicating that the addition of smectite minerals can lead to a pH increase. In a study conducted by Nikitina et al. [33], saponite served as a useful ameliorant, resulting in a meaningfully higher pH (+0.4–0.6 pH units) compared to the control sample that lacked the additive. Smectite minerals have demonstrated an ability to positively influence soil pH by adsorbing hydrogen ions, which can support the phytostabilisation process of HMs [34]. Furthermore, the resultant higher pH levels may help to reduce the toxicity of HMs in the soil, given that metals are typically more soluble in an acidic environment [35].
The experimental data presented in Figure 1b highlight a notable difference in average biomass between the control series and samples containing saponite, with the latter demonstrating an average biomass of 16.7 g/pot. Saponite has been shown to have a positive impact on plant growth by increasing the availability of essential nutrients, such as nitrogen, phosphorous, and potassium, in the soil [36]. As a result of its catalytic properties, saponite facilitates the conversion of organic nutrients into forms that are more readily absorbed by plants [37]. In addition to its nutrient-enhancing abilities, saponite also improves soil structure by promoting water retention [38]. Its unique porous structure, consisting of both micropores and mesopores, facilitates efficient water retention and absorption [39]. By increasing the surface area available for water absorption and storage, saponite enables the soil to retain water more effectively, ultimately promoting plant growth and overall soil health.
It should, however, be noted that the presence of saponite in the soil can affect the outcomes of heavy metal phytostabilisation. This is because saponite enhances the immobilisation of metals in the soil through pH adjustment and increased biomass, but it can also lead to higher metal accumulation in plants, potentially impacting the overall effectiveness of the phytostabilisation process, depending on the specific goals and strategies of the remediation effort.

3.2. Metals in Plants following Phytostabilisation

The analysis of heavy metal contents in plant roots and above-ground parts were analysed (Figure 2) and revealed an important finding. The concentrations of HMs in the root system were notably higher than those in the above-ground parts of the plants. This is primarily due to the direct contact between plant roots and the soil, which often contains substances, such as heavy metals. Additionally, organic substances released by the roots, such as organic acids and amino acids, can increase the solubility of HM ions, which facilitates their absorption by plants, causing the HM content to be noticeably higher than in the above-ground parts [40]. Due to the limited abilities of plants to transport HMs from the roots to the above-ground parts, higher concentrations are typically found in the roots [41,42].
A comparison of heavy metal concentrations in the above-ground parts of plants between the control groups and those with the addition of saponite was also conducted. It was found that the control groups had higher concentrations of HMs, including Cu, Ni, Cd, Zn, and Cr, than those with the application of saponite. However, the concentration of Pb was insignificantly lower in samples with saponite, measuring at 431.37 mg/kg. Through statistical analysis, it was determined that there were no significant differences, indicating that saponite does not affect the concentration of Pb in above-ground plant parts (Figure 2d). This is due to the ability of plants to limit the absorption of Pb by binding it with organic substances in their tissues, such as lignin, cellulose, or hemicelluloses [43]. Pb particles can bind with functional groups of these substances, creating chelates that make it difficult for Pb to be transported to other parts of the plant [44,45].
The results of this study reveal that the presence of saponite in soil leads to an increase in heavy metal concentration in plant roots, with the exception of Cd, which showed no significant difference (Figure 2c). This finding suggests that saponite may not be a highly effective stabilising agent for plant roots. However, it is important to note that roots are the primary means of heavy metal absorption and translocation in contaminated soil, and, as such, their concentration can be affected by various factors [46]. Furthermore, it is worth emphasising that the application of saponite resulted in a 3.5-fold increase in Ni accumulation in plant roots compared to the control sample (Figure 2b). This is due to the fact that Ni ions share similar size and electric charge characteristics with Mg ions, which are trace elements of saponite and can bond with this mineral [47]. Conversely, other heavy metal ions, such as Cu, Cd, Zn, or Cr, do not share similar characteristics with magnesium, making their bonding with saponite less effective. As a result, saponite has a greater affinity for accumulating Ni in plant roots compared to other HMs.

3.3. Metals in the Soil and Exchangeable Fraction

An experiment was conducted to investigate the efficacy of saponite in phytostabilisation for soil contaminated with HMs, such as Cu, Ni, Cd, Pb, Zn, and Cr. The results of the analysis of HMs in the soil are presented in Figure 3.
The results of the conducted study indicate that the addition of saponite to the soil resulted in significant decreases in the levels of Cd, Zn, and Cr by 3 mg/kg, 2606.8 mg/kg, and 66.8 mg/kg, respectively. However, there were no significant differences observed in the levels of Cu, Ni, or Pb in the samples treated with saponite compared to the control samples. Similar findings have been reported in previous research, indicating that clay minerals from the smectite group may have a positive impact on the stabilisation of HMs in soil [48]. A study conducted by Li et al. [49] discovered that the addition of illite and smectite clay with bone chars from pigs, sheep, and cattle could lead to reduced levels of Cd in the soil through stabilisation compared to soil without clay. Similarly, Klik et al. [8] observed similar results in their study, where the application of bentonite, which primarily consists of smectites, resulted in decreased concentrations of HMs, such as Cu, Ni, Cd, Pb, Zn, and Cr, in the soil, which contributed to enhancing the quality of the soil and crop productivity.
It is worth noting that adding saponite to the soil has a positive impact on the bioactivity of HMs. The analysis of heavy metal content in exchangeable forms (exchangeable CaCl2) revealed a decrease in their content in these forms (Table 3).
The analysis of heavy metal concentration in soil samples is crucial for obtaining a comprehensive understanding of their behaviour and mobility. It is worth noting that the total concentration of HMs may not provide a complete picture, especially when comparing samples with and without additives or before and after a process. However, the concentrations of HMs in the CaCl2 fraction of soil samples containing saponite were found to be lower than those in control samples (between 0.4 and 0.8 times), indicating that saponite can effectively reduce the mobility of HMs in soil and limit their migration risk. Moreover, the conversion of metals into a more stable form, such as the oxidisable or residual fraction, is advantageous as it diminishes their chemical reactivity and lowers the risk of migration. These findings have significant implications for managing heavy metal contamination in soil and mitigating its adverse effects.
Saponite, as a mineral from the smectite group, possesses the unique ability to adsorb heavy metal ions, and it can effectively increase the pH level of the soil [50]. When smectites adsorb heavy metal ions, the exchangeable form of these ions reduces, thereby making them less soluble in water. This reduction in bioavailability can lead to a decrease in their harmful effects [51,52]. Additionally, the increase in soil pH levels can also significantly reduce the availability of HMs. Most HMs tend to form strong complexes with acidic functional groups present in the soil, as explained in the Section 3.1.

4. Conclusions

The research conducted on the utilisation of saponite as a soil amendment for facilitating the phytostabilisation of metal-contaminated soil has yielded valuable insights. The addition of saponite has resulted in an increase in soil pH, which can have a positive impact on the phytostabilisation of HMs. The findings indicate that saponite has diverse effects on the accumulation of HMs in plants, with higher concentrations being observed in plant roots as opposed to the above-ground portions. Furthermore, the application of saponite has been found to increase Ni accumulation in roots while showing no discernible effect on Pb accumulation in above-ground portions, thus suggesting that saponite has a selective effect on heavy metal accumulation in plant biomass. Additionally, saponite has been observed to significantly reduce soil Cd, Zn, and Cr levels while having no impact on Cu, Ni, and Pb levels. Overall, saponite has been shown to be an effective means of decreasing the mobility of specific HMs in the soil, thereby reducing their migration risk and potentially mitigating their harmful effects.
These results highlight the potential of saponite as a soil additive for aided phytostabilisation in metal-contaminated soil. However, the varied effects on metal accumulation in plants call for further investigation into saponite’s mechanisms of action and its impact on phytostabilisation under different soil conditions and metal contaminations. Further research is essential to establish its role as a practical and scalable solution for large-scale phytostabilisation projects.

Author Contributions

Conceptualisation, B.K. and M.R.; methodology, M.R.; software, B.K.; validation, B.K. and M.R.; formal analysis, M.B. and M.Z.G.; investigation, B.K.; resources, I.J., D.J. and E.L.; data curation, J.H. and T.B.; writing—original draft preparation, B.K.; writing—review and editing, M.R.; visualisation, B.K. and. M.B.; supervision, M.R.; project administration, M.R.; funding acquisition, I.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of this study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.

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Minerals 13 01354 g001
Figure 1. The effect of the aided phytostabilisation with saponite on changes in pH (a) and plant biomass (b). Significant differences (p < 0.05) between the control and saponite-stabilised samples are denoted by the different letters on the graph.
Figure 1. The effect of the aided phytostabilisation with saponite on changes in pH (a) and plant biomass (b). Significant differences (p < 0.05) between the control and saponite-stabilised samples are denoted by the different letters on the graph.
Minerals 13 01354 g001
Minerals 13 01354 g002
Figure 2. The changes in heavy metal concentrations within the above-ground parts (AGPs) and roots after the experiment: (a) Cu, (b) Ni, (c) Cd, (d) Pb, (e) Zn, and (f) Cr. Different letters show significant differences (p < 0.05) between the control and saponite-stabilised samples.
Figure 2. The changes in heavy metal concentrations within the above-ground parts (AGPs) and roots after the experiment: (a) Cu, (b) Ni, (c) Cd, (d) Pb, (e) Zn, and (f) Cr. Different letters show significant differences (p < 0.05) between the control and saponite-stabilised samples.
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Figure 3. Concentrations of heavy metals in soil samples following the aided phytostabilisation process: (a) Cu, (b) Ni, (c) Cd, (d) Pb, (e) Zn, and (f) Cr. Different letters show significant differences (p < 0.05) between the control and saponite-stabilised samples.
Figure 3. Concentrations of heavy metals in soil samples following the aided phytostabilisation process: (a) Cu, (b) Ni, (c) Cd, (d) Pb, (e) Zn, and (f) Cr. Different letters show significant differences (p < 0.05) between the control and saponite-stabilised samples.
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Table 1. Total concentrations of heavy metals in contaminated soil (n = 3) with acceptable values according to the soil quality standards in Poland [28].
Table 1. Total concentrations of heavy metals in contaminated soil (n = 3) with acceptable values according to the soil quality standards in Poland [28].
MeasurementCuNiCdPbZnCr
(mg/kg)
Concentration671.0113.322.415,290.08433.4727.4
Standard deviation20.46.82.5138.8244.712.6
Acceptable values6005001560020001000
Table 2. Characteristics of the saponite used in this study as a soil additive provided by the manufacturer.
Table 2. Characteristics of the saponite used in this study as a soil additive provided by the manufacturer.
CharacteristicUnitValue
Colour-White–grey
HardnessMohs scale1.0
Density(g/cm3)2.1
Specific surface(m2/g)600
Cation exchange capacity(cmol(+)/kg)60
Table 3. Heavy metal concentration values in exchangeable forms (CaCl2) in control and saponite-stabilised samples after the process of aided phytostabilisation (n = 3 and 95% confidence interval).
Table 3. Heavy metal concentration values in exchangeable forms (CaCl2) in control and saponite-stabilised samples after the process of aided phytostabilisation (n = 3 and 95% confidence interval).
Soil SampleCuNiCdPbZnCr
(mg/kg)
Control0.13 ± 0.0100.03 ± 0.0010.05 ± 0.0010.08 ± 0.0010.24 ± 0.0060.74 ± 0.020
Saponite0.08 ± 0.0010.02 ± 0.0010.03 ± 0.0010.05 ± 0.0010.17 ± 0.0030.61 ± 0.011
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Klik, B.; Brtnicky, M.; Jaskulska, I.; Gusiatin, M.Z.; Jaskulski, D.; Holatko, J.; Baltazar, T.; Liniauskiene, E.; Radziemska, M. Unlocking the Saponite Potential in Aided Phytostabilisation of Multi-Metal-Contaminated Soils. Minerals 2023, 13, 1354. https://doi.org/10.3390/min13111354

AMA Style

Klik B, Brtnicky M, Jaskulska I, Gusiatin MZ, Jaskulski D, Holatko J, Baltazar T, Liniauskiene E, Radziemska M. Unlocking the Saponite Potential in Aided Phytostabilisation of Multi-Metal-Contaminated Soils. Minerals. 2023; 13(11):1354. https://doi.org/10.3390/min13111354

Chicago/Turabian Style

Klik, Barbara, Martin Brtnicky, Iwona Jaskulska, Mariusz Zygmunt Gusiatin, Dariusz Jaskulski, Jiri Holatko, Tivadar Baltazar, Ernesta Liniauskiene, and Maja Radziemska. 2023. "Unlocking the Saponite Potential in Aided Phytostabilisation of Multi-Metal-Contaminated Soils" Minerals 13, no. 11: 1354. https://doi.org/10.3390/min13111354

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