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Article

Study on the Effect of the Copper Tailing Substrate with Different Treatments on the Growth of Tall Fescue (Festuca arundinacea)

by
Jinchun Xue
1,
Weiwei Wang
1,
Min He
2,*,
Jiajia You
1 and
Huaqin Han
1
1
School of Energy and Mechanical Engineering, Jiangxi University of Science and Technology, Nanchang 330013, China
2
School of Software Engineering, Jiangxi University of Science and Technology, Nanchang 330013, China
*
Author to whom correspondence should be addressed.
Sustainability 2022, 14(22), 15387; https://doi.org/10.3390/su142215387
Submission received: 23 October 2022 / Revised: 10 November 2022 / Accepted: 16 November 2022 / Published: 18 November 2022
(This article belongs to the Section Environmental Sustainability and Applications)
Browse Figures
Versions Notes

Abstract

:
The copper sulphide mining process would produce a large number of copper tailings that can be treated with different substrates so as to act as guest soil in the ecological reclamation of the mine. In order to reveal the influence of different copper tailing treatment substrates on plant growth, in this experiment, tall fescue (Festuca arundinacea) was planted under potted conditions for the purpose of exploring the effect of different exogenous substrates such as conditioning agents, sulfurized modified straw, effective microorganisms (EM), and high-density sludge (HDS) sediment on tall fescue height, biomass, chlorophyll, catalase (CAT) activity and Cu2+ transport under copper tailings substrate. Then, the results showed that the combined application of different exogenous substrates (conditioning agents, EM, sulfurized modified straw, and HDS sediment) reduced the pH of the copper tailing substrate to varying degrees, with a decrease of 5–21%. Moreover, compared with the control group and other treatments, the combined treatment of conditioning agents, sulfurized modified straw, and EM has a significant impact on the biomass, plant height, chlorophyll content, CAT activity, and other physiological indicators of tall fescue and can effectively reduce Cu2+ that is toxic to tall fescue in copper tailing.

1. Introduction

With the rapid development of society and economy, the demand for copper resources is increasing. However, the mining of copper resources will inevitably cause a large number of copper tailing discharge problems. According to statistics, the output of tailings in China alone was about 1.211 billion tons, of which the annual output of copper tailings was about 302 million tons in 2018. Whereas the utilization rate of copper tailings was less than 10% [1,2]. Copper tailings piled up in quantity not only caused serious waste and imbalance of land resources, but also resulted in serious pollution and harm to the ecological environment. To be specific, first of all, copper tailings contain a huge number of pollutants such as heavy metals and beneficiation agents that will pass physical, chemical, and biological migration into the atmosphere, water bodies, and soil, thus causing environmental pollution. Apart from that, dust and fine sand will negatively affect the environment of the surrounding areas, and sandstorms often occur in arid and windy areas [3]. Second, the large accumulation of copper tailings leads to land degradation, desertification, and salinization, thus arousing a series of ecological problems such as the destruction of vegetation and even threatening the safety of humans and animals in the mining area [4,5]. Other than that, the copper tailings occupy a large amount of agricultural and forest land, causing the land resources in the area to be out of balance [6]. In addition, the unsafe hidden dangers caused by the continuous accumulation of copper tailings are also increasing. Especially when a large amount of rainwater enters, the rainwater runoff may form a landslide. If rainwater is improperly intercepted and discharged in the dump, it is easy to induce landslides, mudslides, and other geological disasters in the case of rainstorms and flood infiltration [7]. Therefore, the rational utilization of copper tailing resources is imperative.
Considering copper tailings are featured with poor structure, extremely poor nutrients, and high content of heavy metals, there are few plants that can grow naturally there, which restricts its restoration and management to a great extent [8]. Vegetation reconstruction is the most effective and economic way, which includes the use of appropriate organic or inorganic added and the selection of appropriate plant species. Therefore, determining the plant species is essential to ensure sustainable vegetation cover. Fischer et al. suggested plant tolerance to heavy metal is the result of natural selection rather than innate physiological inheritance [9]. In recent studies, tall fescue shows high tolerance as well as enrichment ability to various heavy metals, including Cd, Cu, Pb, and Zn [10]. Lou et al. pointed out that compared with most herbal plants, tall fescue demonstrates excellent growth potential under saline-alkali and high-temperature environments, with great advantages in saline-alkali tolerance and drought resistance and they usually grow well in soils with pH of 4.7 to 9.0. Furthermore, tall fescue can normally live on heavy metal-contaminated soil and uptake of a certain quantity of heavy metal [11]. Lan and Ye et al. have investigated reclamation of lead-zinc mines in southern China by applying tolerant plants (e.g., Cynodo dactyldon) and organic additives (e.g., manure and garbage compost) and achieved success [12,13]. Moreover, the research conducted by Fellet et al. showed that adding biochar to the tailings can enhance the substrate’s nutrition and water retention properties and reduce the bioavailability of certain pollutants. The use of biochar in mine wastes helps plants build the green covering layer in the process of plant stabilization [14]. In addition, Juwarkar et al. added ETP sludge, biological fertilizer, and mycorrhizal fungi to the planting substrate, which increased the organic matter of the substrate while reducing the toxicity of heavy metals and provided better anchorage and growth of the selected plants on the coal gangue pile [15]. The available concentration of plants helps promote the initial restoration of vegetation in the contaminated soil of wasteland [16]. Apart from that, Kumar and others used different organic modifiers such as biological sludge, dairy sludge, and biological fertilizers to conduct greenhouse experiments on plant substrates. Appropriate measures provide nutrients for plant growth and reduce the metal toxicity of plants while supporting plant growth, thereby promoting the growth of jatropha (Jatropha curcas) [17]. At present, there are many studies on the improvement of contaminated soil in mining areas and the screening of tolerant plants. However, single material has limited effectiveness and the cost is high. The growth status of higher plants was used for detection of pollution degree in soil, which was one of the most important approaches to measure soil health and evaluate soil quality from an ecological perspective [18].
Conditioner is a new type of fertilizer, mainly to improve the physical, chemical, and biological properties of soil, making it more suitable for plant growth [19]. Straw is mainly used as crop base fertilizer and EM is mainly used to improve soil structure and soil fertility [20,21]. On the other hand, according to statistics, almost one million tons of sediments are generated annually during the HDS process in Jiangxi Province [22]. The trend is still increasing, which has seriously threatened the mines’ ecological safety. Meanwhile, HDS sediment are classified as class I general industrial solid wastes, it is safe, reliable, and low-cost, and can be widely used in mine ecological restoration projects to achieve the purpose of waste treatment waste [23]. Different from previous studies, in this study, straw, conditioner, EM and HDS sediment were utilized as composite amendments for copper tailing remediation, and copper tailings replaced guest soil as the plant growth substrate for mine ecological remediation. Considering that, in this paper, the perennial herbaceous tall fescue is taken as the research object. Moreover, an 8-week outdoor pot experiment is performed to explore the effect of different treatments concerning exogenous substrates such as conditioning agents, sulfurized modified straw, EM and HDS sediment on tall fescue in copper tailings. Then, physical and chemical indicators such as plant height, biomass, chlorophyll content, CAT enzyme activity, Cu2+ transport coefficients of the surviving plants were analyzed and discussed in order to screen out the effect for improving plant growth.

2. Materials and Methods

2.1. Materials

2.1.1. Plants Materials

The fresh samples of seeds of tall fescue used in the study were obtained commercially from Muyangdou Seed Research Industry Co., LTD. The initial germination percentage of the seeds was over 95%. The plant was identified and authenticated in the Herbarium, Biology Department, Nanjing University, with voucher number 19103042.

2.1.2. Other Materials

Test copper tailings: as shown in Figure 1, copper tailings were collected from the 4# tailing reservoir of DeXing Copper Mine in JiangXi Province (29°0′3″ N 117°43′33″ E). Using the grid point method, tailings of 0–20 cm surface layer samples were collected with a small shovel at each sampling point, and used for the pot experiment. As for copper tailings, the particle size is extremely small, while the bulk density is 1.6 g cm−3, and the pH value is between 8.5 and 9.0. Moreover, the conditioning agent was made by mixing peat soil, medical stone, calcite, frankincense, oil cake, and compound fertilizer in proportion. Here, it should be mentioned that the pH value of the tested HDS sediment is between 7.5 and 9.0. In addition, the phosphorus and potassium required for plant growth in the HDS sediment are within the normal range, while the nitrogen content is very small. Furthermore, the tested EM is a microbial inoculum composed of more than 80 species of 10 genera, mainly photosynthetic bacteria, lactic acid bacteria, yeasts, and actinomycetes. After drying, the test straw was cut into 5–8 cm sections and modified with 10% ammonium sulfate solution.

2.2. Experimental Design and Treatments

There were five experimental groups in the experiment, denoted as CK, T1, T2, T3 and T4, and three parallel groups for each group. In detail, in CK group, only 1500 g pure tailings were added; T1 group was 1600 g pure tailings + 60 g conditioning agents; T2 group was 1500 g pure tailings + 60 g conditioning agents + 250 g EM + 10 g sulfurized modified straw; T3 group was 1500 g pure tailing sand + 60 g conditioning agents + 250 g EM; the T4 group is 1000 g pure tailings + 500 g HDS sediment + 60 g conditioning agents + 10 g sulfurized modified straw + 250 g EM. Then, flower pots with a diameter of 235 mm were chosen, and 20 reed-shaped tall fescue seeds were sowed in each pot featured with the depth of 2 cm, and compacted by hand. After that, the seeds were watered for less than once three days before emergence to avoid lowering the temperature, and the same amount of water was used every two days after emergence. In the first week after sowing, the number of seed germination was recorded, and the growth height of the plant was recorded once every two weeks. After 8 weeks, samples were taken for analysis.

2.3. Plant Analysis and Statistical Analysis

The biomass and morphology tests were performed in quintuplicate, and the remaining tests were performed in triplicate. Ten tall fescue seedlings were randomly taken out from the five pots of the respective treatment group and then rinsed with tap water twice to prevent residual copper tailings from causing errors in the test results. Afterward, the fresh samples were placed in an electric heating blast drying box (DHG-2200B, Zhengzhou Shengyuan instrument Co. LTD., Zhengzhou, China) at 105 °C for 30 min and then kept at 80 °C for 6 h. Then, the dry weight was measured. Beyond that, the ethanol extraction method was adopted to measure the content of chlorophyll a, chlorophyll b in this study [24], while catalase activity was determined using UV spectrophotometry [25], and the Cu2+ content was determined using inductively coupled plasma atomic emission spectroscopy [26]. Furthermore, the pH value of the substrate was determined by the water extraction potential method (the ratio of water to soil was 2.5:1) [27]. SPSS 20 software was adopted for the one-way analysis of variance (ANOVA), and statistical differences between treatments were conducted by performing Duncan’s multiple range test (p < 0.05), Microsoft Excel 2016 and Origin 9.1 software were employed for drawing.

3. Results

3.1. Influence of Different Exogenous Substrates on the pH Value of Copper Tailings

It can be seen from Table 1 that the original copper tailings are alkaline, and the pH of each substrate dealt with different treatments is significantly different (p < 0.05), considering they are all between 7 and 8.55. When a conditioning agent is added to the copper tailings (T1 treatment), the pH of the copper tailings drops by 0.39 units. When conditioning agent and EM (T3 treatment) are added to the copper tailings, the pH of the copper tailings experiences a significant drop; it becomes neutral, which is related to the acidity of the EM and conditioning agent itself. Compared with T3 treatment, T2 treatment had a smaller drop in pH of copper tailings by 1.38 units, while compared with the T2 treatment, the pH decrease of the copper tailing substrate was even smaller. Although there was no significant difference in the pH of the copper tailing substrate accepting the T1, T3, T2, and T4 treatments after planting tall fescue for 2 months (p > 0.05), each treatment did not cause a fundamental change in the pH of the substrate. However, for the copper dealt with different treatments, the pH of the tailing sand substrate was higher than that of the copper tailing sand without planting tall fescue, which reflected that the copper tailing sand experiencing different treatments planted with tall fescue tended to be alkaline.

3.2. Effects of Different Exogenous Substrates on the Biomass and Plant Height of Tall Fescue

It can be shown from Figure 2 that the tall fescue treated with CK withered, turned yellow, grew short, and had low coverage, which was typical characteristics of malnutrition and heavy metal poisoning. On the contrary, the tall fescue treated with conditioners, microorganisms, sulfurized modified straw and bottom mud grew well. Compared with the CK group, the growth status of tall fescue was improved after the copper tailing matrix was added with a conditioning agent (T1 treatment), while in comparison with the T3 treatment, in the T1 treated copper tailing matrix after the addition of microbial inoculants, the reed, the coverage and growth of fescue have not improved. After covering the surface of the copper tailing matrix with the conditioning agent and EM with a layer of sulfurized modified straw (T2 treatment), the tall fescue grew luxuriantly. Moreover, when T4 was compared with T2, the survival rate and coverage of tall fescue decreased significantly after the addition of HDS sediment, indicating that HDS sediment is not suitable as an exogenous additive substrate for the green reclamation of copper tailings.
Plant biomass and height can directly reflect plant growth and development. Figure 3a shows the effect of different exogenous substrates on the biomass of tall fescue, while Figure 3b displays the effect of different exogenous substrates on the height of tall fescue. It can be seen from Figure 2 that after 8 weeks of tall fescue growth, the biomass of the CK group was the lowest compared with that of other treatment groups, with a value of 0.24 g, and the combination of different exogenous substrates increased its biomass to varying degrees. Apart from that, the effect of T2 treatment was the most obvious, and its biomass increase was 3.75 times that of the CK group, reaching a significant difference level (p < 0.05). In contrast, T1, T3, and T4 treatments had similar effects on tall fescue biomass. Among these 3 species, there was no significant difference between the two treatments of tall fescue biomass (p > 0.05), and the increase was 1.96 times, 2.00 times, and 1.88 times that of the CK group respectively, demonstrating that the combined application treatment (T2 treatment) can better improve the growth environment of tall fescue on the copper tailing sand substrate and promote the growth of tall fescue.
For the same plant, the higher the plant height, the greater the coverage, while the better the prevention of wind erosion and water erosion of tailings, the better the return of organic matter after plant death. The plant height changes of plants growing on different substrates during the same growth period can reflect the adaptability of plants to the substrate. Furthermore, it can be seen from Figure 3 that due to the lack of nutrients required for plant growth in the CK group, plant growth was inhibited, and the plant height increased slightly. Besides, the tall fescue did not change from the 2nd week to the 8th week, while T1, in the copper tailing sand substrate treated with T2 and T4, the plant height of tall fescue increased in different degrees. Compared with T1 and T4, the plant height of tall fescue after T2 treatment increased significantly, while compared with the CK group, the height of tall fescue after T3 treatment decreased, which reflects that tall fescue is more adaptable to the growth environment of the copper tailing substrate treated with conditioning agents, EM, and sulfurized modified straw (T2 treatment).

3.3. Effects of Different Exogenous Substrates on the Content of Chlorophyll and CAT Activity in Tall Fescue

Figure 4a,b respectively present the effect of different exogenous substrates on the chlorophyll and the CAT activity of tall fescue. It can be known from Figure 3a that the combined application of different exogenous substrates has different degrees of influence on the chlorophyll content of tall fescue. There are significant differences in the chlorophyll content of tall fescue between T2 and T4 treatments and the CK group. The increase in the chlorophyll content of tall fescue is the most obvious, with an increase of 141% and 150%, respectively. In terms of the treatment groups T1, T3 and CK, there was no significant difference between the two groups. The chlorophyll content of tall fescue increased by 81% and 40%, respectively. Compared with the CK group, the increase of chlorophyll b in the T1 to T4 treatment groups was 46%, 99%, 18%, and 106% accordingly, and there was no significant difference in the chlorophyll b content of tall fescue among the copper tailing sands treated with different treatments.
From Figure 4b, it can be found that the combination of different exogenous substrates effectively increased CAT activity. Compared with the control group CK, the treatment groups T1, T2, T3, and T4 increased by 230%, 287%, 487%, and 528%, respectively. Whereas the difference between treatments was significant (p < 0.05). Under the copper tailing matrix, when the treatment group T1 was compared with the control group CK, the single application of the conditioning agent could significantly increase the CAT activity, and when the treatment group T3 was compared with T1, the addition of EM could increase the CAT activity of the conditioning agent alone. When T2 and T3 were compared, as well as T4 and T2, the effect of treatment group T2 and T3, T4 and T2 were not significant. The addition of sulfurized modified straw improved the effect of treatment group T3 to a great extent, while the addition of HDS sediment failed to largely increase CAT activity in treatment group T3.

3.4. Effects of Different Exogenous Substrates on Cu2+ Transport in Tall Fescue

Transport coefficients are generally used to analyze the ability of plants to transport heavy metals above the ground, which is of great significance to the removal of heavy metals from the soil. As shown in Figure 5, the copper content of the underground and above-ground parts of the CK group was 590.12 mg/kg and 34.04 mg/kg, respectively, while that of the underground parts of the plants in the T1, T2, T3, and T4 groups decreased compared with the control group. Regarding copper content in the above-ground parts of plants, the T1 group increased by 20.0% compared with the CK group, whereas the T2, T3, and T4 groups decreased by 41.6%, 3.9%, and 75.1% separately, compared with the CK group. Moreover, the Cu content of tall fescue grown in copper tailing substrates with different exogenous substrates is quite different. To be specific, the Cu content of the above-ground part of the tall fescue in each treatment of the copper tailing sand matrix is T1 > CK > T3 > T2 > T4, while that of the underground part is CK > T1 > T3 > T4 > T2, which may be due to the effect of microorganisms on dissolved Cu. It has a strong complexing ability, and the porous surface of sulfurized modified straw possesses a certain adsorption capacity for Cu. Therefore, the Cu content of tall fescue under the substrate of copper tailings treated with T2, T3, and T4 is significantly lower than that in the ground and underground. Control group CK. Under different treatments, the transport coefficients of tall fescue in the copper tailing substrate were all less than 1. In addition, the difference was not significant, meaning that the tall fescue was mainly enriched in the underground part of Cu.

4. Discussion

The measurement results concerning main physiological indexes of tall fescue under different copper tailing substrate treatments showed that the pH, biomass, plant height, chlorophyll, CAT activity and Cu2+ transport coefficient of tall fescue undertake various influence of different exogenous substrates, such as conditioning agents, EM, sulfurized modified straw and HDS sediment.
The pH of copper tailings is its most basic physical and chemical property. It interacts with the activities of microorganisms in copper tailings, the synthesis and decomposition of organic matter, the transformation, release and effectiveness of various nutrients, and the ability of copper tailings to retain nutrients [28]. Other than that, it has an important influence on the element ions that plant roots absorb minerals. After adding the conditioning agents alone (T1 treatment), the pH of the copper tailing was between 8.37 and 8.51, which is mainly because the conditioning agents contains a large amount of peat, and the pH of peat is acidic, which can effectively neutralize the alkaline degree of copper tailing [29]. Furthermore, the pH of the copper tailing matrix decreased to different degrees after the application of different exogenous substrates. On the one hand, the pH of the conditioning agents and EM were 5.0–6.0. In addition, adding sulfurized modified straw could enhance the exchangeability of copper tailings, whereas the content of calcium, exchangeable magnesium, and exchangeable potassium increases the base saturation of the copper tailings [30]. Therefore, the pH of the copper tailing matrix treated with T2 is higher than that with T3. Apart from that, the copper tailing matrix treated with T4 may result from the sediment containing a large amount of Ca2+. When the Ca2+ in the sediment starts to become saturated, the external Na+ infiltrates into the soil along with rainfall, resulting in a balance of charges in the sediment. Besides that, the sediment colloid has a strong adsorption capacity for Na+, which leads to the release of Ca2+, which is even higher than the pH of the copper tailing matrix treated with T2 [31]. With regard to applying amendments and planting plants, the pH value of all experimental groups showed an increasing trend, which may result from NO3-N is the available nutrient of plants and the main component of soil solution. The absorption of NO3-N by plants requires the OH− secreted by the roots to maintain the charge balance inside and outside the cell membrane, which also makes a large amount of OH- enter the soil colloid, resulting in the rise of soil pH in the root region of plants [32]. According to observations, the tall fescue planted on copper tailings is short, with withered stems and leaves, mainly due to the poor nutrients of the copper tailing matrix, low water holding capacity, and lack of key soil microbial diversity, which is not conducive to the normal growth of plants [33]. As for the growth of tall fescue, it was obviously different after different exogenous substrates were treated with copper tailings. Among them, the combined application of conditioning agents, EM and sulfurized modified straw (T2 treatment) could further promote the growth of tall fescue. It is a conditioning agent that provides nutrients for the microorganisms in the copper tailing matrix to improve the biological fertility of the copper tailing matrix and enhance the structure of the copper tailings matrix [34]. On the other hand, sulfurized modified straw strengthens the water retention of the copper tailings. In addition to that, performance and hyphae appear on the contact surface between sulfurized modified straw and the copper tailings, thus improving the living environment of microorganisms, and further effectively enhancing the plant suitability of the copper tailings and the suitable environment for the growth of tall fescue. Moreover, the change of chlorophyll content is an adaptive change of plants to adversity conditions [35]. Compared with the copper tailing substrates treated with different treatments, the chlorophyll content of tall fescue grown on the original copper tailings is lower, maybe because various heavy metal elements in the copper tailing substrate are absorbed and transported to the leaf parts through the roots, forming the plant body. Whereas, the chlorophyll structure is destroyed, and the synthesis of chlorophyll is hindered, which leads to a decrease in the chlorophyll content of plants. First, adding the conditioning agent, EM, and HDS sediment can dilute the heavy metals in the copper tailings [36]. Second, the sulfurized modified straw rebuilds an uncontaminated surface layer on the copper tailings, which effectively alleviates the stress of heavy metals on plants and promotes plant growth [37]. In this case, it is indicated that the lower the content of chlorophyll, the stronger the stress of plants, and the weaker the adaptability and tolerance of plants to copper tailing substrates. Different exogenous substrates can appropriately improve the copper tailing substrate to increase plant chlorophyll content and light. CAT is universally present in plant tissues, and its activity is related to the metabolic strength of plants and the ability of cold resistance and disease resistance. In the process of plant growth and development, its activity is constantly changing. Therefore, CAT activity can be taken as a reference physiological indicator of plant resistance [38]. Compared with the control group, the CAT activity of tall fescue was significantly increased after the copper tailing sand substrate was treated with different treatments, possibly because different treatments improved the growth environment of tall fescue and promoted the growth of tall fescue, whereas the metabolism of plants is strong, and the production of free radicals increases. In order to maintain the normal growth of plants to the utmost extent, the plant will induce the synthesis of more CAT to eliminate the large number of free radicals produced to ensure the normal growth of plants [39]. Therefore, the treatment of different copper tailing sand substrates alleviated the stress of the copper tailing sand substrate on the tall fescue and improved the resistance of the tall fescue to the copper tailing sand substrate. The Cu content of tall fescue in the control group is higher than that in other groups, which may be due to the strong complexing ability of EM to dissolved Cu, while the loose and porous surface of sulfurized modified straw has a certain adsorption capacity for Cu, and the coverage of HDS sediment rebuilds an uncontaminated surface layer for the copper tailings matrix, causing the Cu in the copper tailings to be adsorbed and deposited in HDS sediment by the porous particles when it migrates to the plant roots, effectively reducing the tall fescue Cu absorption [40,41].

5. Conclusions and Outlook

In this study, the experiment of outdoor planting of tall fescue after copper tailings matrix was treated with different treatment methods. Comprehensive comparison of observation and data analysis results showed that, compared with the control group CK and other treatment groups, the combined application of conditioning agents, EM and sulfurized modified straw had the most significant increase in the biomass and plant height of tall fescue, and could improve the fitness performance of plants. And after copper tailings were added with conditioning agents, EM and sulfurized modified straw, the growth of tall fescue was lush, the biomass was the largest, and the chlorophyll content and catalase activity increase significantly, which can further enhance the stress resistance of tall fescue. It shows that the co-application of conditioning agents, EM and sulfur-modified straw (T2 treatment) copper tailings matrix was beneficial to the growth of tall fescue, and T2 treatment can be considered as a treatment measure for in-situ ecological reclamation of tailings vegetative matrix in copper sulfide mine tailings pond. The copper tailings added with conditioning agents and EM can significantly improve the transport ability of tall fescue to Cu2+ and reduce the toxicity of copper tailings. In summary, the amendments promoted the growth and Cu enrichment of tall fescue to different degrees, and the repair effects were as follows: T2 > T1 > T4 > T3 > CK. Therefore, the mixture of conditioning agents, EM and sulfurized modified straw can be used as the amendments of the copper tailings.
Phytoremediation efficiency was related to plant species, amendments ratio, heavy metal species, and planting time. Due to limited time, in order to verify the potential of conditioning agent, EM, sulfurized modified straw, and HDS sediment combined with herbaceous plants in the long-term remediation process of polymetallic contaminated tailings, long-term pilot studies should be conducted in the future, which may achieve better results in mine reclamation applications.

Author Contributions

W.W. performed the data analyses and wrote the manuscript; J.X. contributed to the conception of the study; J.Y. contributed significantly to analysis; M.H. performed the experiment; H.H. helped perform the analysis with constructive discussions. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by Key R&D Program of Jiangxi Province, China (20212BBG73013) and Jiangxi Province Graduate Innovation Special Fund Project, China (YC2022s697).

Institutional Review Board Statement

Experimental research and field studies on plants complies with relevant institutional, national, and international guidelines and legislation.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data included in this study are available upon request by contact with the corresponding author.

Conflicts of Interest

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

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Figure 1. Map of region and the sampling points. (a) Location map of the JiangXi Province within China. (b) Location map of the DeXing within the JiangXi Province. (c) Location map of DeXing Copper Mine. (d) Locations map of the sampling points. (a–d maps were created by ArcGIS 9.3).
Figure 1. Map of region and the sampling points. (a) Location map of the JiangXi Province within China. (b) Location map of the DeXing within the JiangXi Province. (c) Location map of DeXing Copper Mine. (d) Locations map of the sampling points. (a–d maps were created by ArcGIS 9.3).
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Figure 2. The effect of different exogenous substrates on the growth of tall fescue; CK group is 1500 g pure tailings; T1 group is 1500 g pure tailings + 60 g conditioning agents; T2 group is 1500 g pure tailings + 60g conditioning agents + 250 g EM+ 10 g sulfurized modified straw; T3 group is 1500 g pure tailings + 60 g conditioning agents + 250 g EM; T4 group is 1000 g pure tailings + 500 g conditioning agents + 60 g sulfurized modified straw + 250 g EM + 10 g HDS sediment.
Figure 2. The effect of different exogenous substrates on the growth of tall fescue; CK group is 1500 g pure tailings; T1 group is 1500 g pure tailings + 60 g conditioning agents; T2 group is 1500 g pure tailings + 60g conditioning agents + 250 g EM+ 10 g sulfurized modified straw; T3 group is 1500 g pure tailings + 60 g conditioning agents + 250 g EM; T4 group is 1000 g pure tailings + 500 g conditioning agents + 60 g sulfurized modified straw + 250 g EM + 10 g HDS sediment.
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Figure 3. The effect of different exogenous substrates on the biomass (a) and height (b) of tall fescue; samples with the same letters are not significantly different according to the Tukey-Kramer honestly significant difference test (α = 0.05). CK group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents +EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
Figure 3. The effect of different exogenous substrates on the biomass (a) and height (b) of tall fescue; samples with the same letters are not significantly different according to the Tukey-Kramer honestly significant difference test (α = 0.05). CK group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents +EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
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Figure 4. The effect of different exogenous substrates on the chlorophyll (a) and catalase activity (b) of tall fescue; samples with the same letters are not significantly different according to the Tukey-Kramer honestly significant difference test (α = 0.05). CK group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents + EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
Figure 4. The effect of different exogenous substrates on the chlorophyll (a) and catalase activity (b) of tall fescue; samples with the same letters are not significantly different according to the Tukey-Kramer honestly significant difference test (α = 0.05). CK group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents + EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
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Figure 5. The effect of different exogenous substrates on the Cu transport coefficient of tall fescue; samples with the same letters are not significantly different according to the Tukey–Kramer honestly significant difference test (α = 0.05). CK group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents + EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
Figure 5. The effect of different exogenous substrates on the Cu transport coefficient of tall fescue; samples with the same letters are not significantly different according to the Tukey–Kramer honestly significant difference test (α = 0.05). CK group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents + EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
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Table
Table 1. The effect of planting tall fescue on the pH value of copper tailings with different exogenous substrates.
Table 1. The effect of planting tall fescue on the pH value of copper tailings with different exogenous substrates.
Treatment CK T1 T2 T3 T4
pH of unplanted tall fescue substrate 8.83 ± 0.04 a 8.44 ± 0.07 b 7.45 ± 0.05 d 7.01 ± 0.01 e 7.77 ± 0.03 c
Substrate pH after planting tall fescue for 2 months 9.29 ± 0.04 a 8.49 ± 0.13 b 7.95 ± 0.12 c 8.52 ± 0.20 b 7.99 ± 0.03 c
Note: The data in the above table are average values ± standard deviations. The same line of letters in the table indicates no significant difference between the treatments with different substrate pH values. The different letters refer to a significant difference between the treatments with different substrate pH values (p < 0.05). CK Group is pure tailings; T1 group is pure tailings + conditioning agents; T2 group is pure tailings + conditioning agents + EM + sulfurized modified straw; T3 group is pure tailings + conditioning agents + EM; T4 group is pure tailings + conditioning agents + sulfurized modified straw + EM + HDS sediment.
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Xue, J.; Wang, W.; He, M.; You, J.; Han, H. Study on the Effect of the Copper Tailing Substrate with Different Treatments on the Growth of Tall Fescue (Festuca arundinacea). Sustainability 2022, 14, 15387. https://doi.org/10.3390/su142215387

AMA Style

Xue J, Wang W, He M, You J, Han H. Study on the Effect of the Copper Tailing Substrate with Different Treatments on the Growth of Tall Fescue (Festuca arundinacea). Sustainability. 2022; 14(22):15387. https://doi.org/10.3390/su142215387

Chicago/Turabian Style

Xue, Jinchun, Weiwei Wang, Min He, Jiajia You, and Huaqin Han. 2022. "Study on the Effect of the Copper Tailing Substrate with Different Treatments on the Growth of Tall Fescue (Festuca arundinacea)" Sustainability 14, no. 22: 15387. https://doi.org/10.3390/su142215387

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