Sustainability

Editorial

7 pages, 180 KiB

Open AccessEditorial

Advancements in Phytoremediation Research for Soil and Water Resources: Harnessing Plant Power for Environmental Cleanup

by Jae K. Park and Kokyo Oh

Sustainability 2023, 15(18), 13901; https://doi.org/10.3390/su151813901 - 19 Sep 2023

Cited by 1 | Viewed by 1362

Abstract

Phytoremediation, an environmentally conscious and sustainable strategy, revolves around harnessing the power of plants to counteract the harmful impacts of pollutants on our ecosystems [...] Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

Research

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18 pages, 5787 KiB

Open AccessArticle

Risk of Heavy Metal Contamination in Vegetables Fertilized with Mushroom Residues and Swine Manure

by Changhe Li, Wenchong Lan, Zhi Jin, Siwen Lu, Jingyu Du, Xindong Wang, Yonghui Chen and Xuefeng Hu

Sustainability 2023, 15(14), 10984; https://doi.org/10.3390/su151410984 - 13 Jul 2023

Cited by 1 | Viewed by 806

Abstract

Mushroom residues and swine manure are two common types of agricultural waste that are often returned to fields as organic fertilizers. However, the environmental risks of their reclamation, such as heavy metal pollution, have been less studied. To investigate the potential risks of [...] Read more.

Mushroom residues and swine manure are two common types of agricultural waste that are often returned to fields as organic fertilizers. However, the environmental risks of their reclamation, such as heavy metal pollution, have been less studied. To investigate the potential risks of heavy metal contamination in soils and vegetables after continuously applying mushroom residues and swine manure, field experiments of four consecutive vegetable rotations were conducted in the Qingpu District of Shanghai, Southeast China, from 2019 to 2021. The concentrations of heavy metals in soils continuously fertilized with mushroom residues and swine manure gradually increased. The organic matter content in the soils exhibited a significant correlation with the concentrations of Cu, Zn, Pb, and Cd (p < 0.01), suggesting that the increase in heavy metals is attributed to the use of organic waste. In particular, the application of swine manure increased Cu, Zn, Pb, and Cd concentrations in the soils by 118.3%, 54.9%, 57.6%, and 122.2%, respectively. Moreover, the application of organic waste raised the risk of the bioaccumulation of toxic metals, such as Cd, in vegetables. The Cd concentration was significantly and positively correlated with Zn in the edible parts of vegetables (p < 0.05). The recycling of swine manure more significantly enhanced Cd concentrations in the edible parts of green pepper (Capsicum annuum), eggplant (Solanum melongena), Brassica chinensis, and lettuce (Lactuca sativa), which were 2.53, 1.55, 1.66, and 1.62 times that of the non-fertilizer control (CK), respectively. Although the increase in heavy metals in the soils and vegetables was still mild when compared with the set thresholds of soil and food safety after the four vegetable rotations, the trend of increase in toxic heavy metals in the food chain with a continuous application of organic waste should be carefully considered. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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9 pages, 1546 KiB

Open AccessCommunication

Using Time-to-Event Model in Seed Germination Test to Evaluate Maturity during Cow Dung Composting

by Yuan Luo, Xiangzhuo Meng, Yuan Liu, Kokyo Oh and Hongyan Cheng

Sustainability 2023, 15(5), 4201; https://doi.org/10.3390/su15054201 - 26 Feb 2023

Cited by 1 | Viewed by 932

Abstract

Maturity is a matter of concern for the utilization of livestock manures after composting because of the phytotoxicity of immature compost. The seed germination test is widely used for evaluating the maturity of compost. However, the process of seed germination was not studied [...] Read more.

Maturity is a matter of concern for the utilization of livestock manures after composting because of the phytotoxicity of immature compost. The seed germination test is widely used for evaluating the maturity of compost. However, the process of seed germination was not studied by establishing a model for evaluating the maturity. Here, we established a time-to-event model for the data of germination proportion over time in a seed germination test with cow dung compost at different composting times. Results show that the profile of the seed germination proportion over time for Chinese cabbage (Brassica rapa L.) and garden cress (Lepidium sativum L.) were both well described by the model. Seed germination was delayed in composts at the early stage of composting from parameter t₅₀ (half germination time) of the model. Parameter t₅₀ was significantly negatively related to radicle length (RL), which indicated that there is an organic relationship between seed germination (i.e., radicle emergence) and radicle elongation. In conclusion, the immature compost can hinder seed radicle elongation by delaying seed germination. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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16 pages, 4091 KiB

Open AccessArticle

Microcosm Study on the Potential of Aquatic Macrophytes for Phytoremediation of Phosphorus-Induced Eutrophication

by Sarah Dean, Muhammad Shahbaz Akhtar, Allah Ditta, Mohammad Valipour and Sohaib Aslam

Sustainability 2022, 14(24), 16415; https://doi.org/10.3390/su142416415 - 08 Dec 2022

Cited by 4 | Viewed by 1495

Abstract

Phosphorous (P) is one of the primary nutrients to cause the eutrophication of water bodies. This process leads to algal blooms and anoxic conditions which have consequences in the form of mortality of aquatic animals, and impaired water quality. Aquatic macrophytes could be [...] Read more.

Phosphorous (P) is one of the primary nutrients to cause the eutrophication of water bodies. This process leads to algal blooms and anoxic conditions which have consequences in the form of mortality of aquatic animals, and impaired water quality. Aquatic macrophytes could be the promising candidates that can filter P from water contaminated with high levels of nutrients. In the present microcosm research, two types of floating macrophytes, i.e., salvinia floater (Salvinia natans) and water lettuce (Pistia stratiotes) were deployed to compare their P-removal rates and efficiency under different incubation times (72, 168, and 264 h intervals). Plants were exposed to different treatments, i.e., (1) P-fed plants, (2) P-starved plants, (3) control treatments, and (4) synthetic wastewater treatment. Both plant species showed substantial P-removal efficiency from P-eutrophicated solutions and removed P-amounts were significantly correlated (R² ≅ 1 at p ≤ 0.05) with P-accumulated in plant biomass. Plants in the P-starved state showed significantly higher P-removal rates and removal efficiency compared to plants without P-starvation. When Salvinia natans was exposed to 10 mg L⁻¹ of P for 264 h of incubation, 21 g of fresh biomass was recorded during the P-starved phase, more than P. stratiotes (14 g) under similar conditions. The P. stratiotes removed 86.04% of P from 5 mg L⁻¹ P solution, 53.76% from 10 mg L⁻¹ P solution and 66.84% from SWW in the P-starved phase whereas, removal efficiency without the P-starvation phase was 33.03% from 5 mg L⁻¹ P solution, 39.66% from 10 mg L⁻¹ P solution, and 31.64% from SWW after 264 h interval. Compared to S. natans, P. stratiotes removed 86.0% P from a 5 mg L⁻¹ P solution, whereas S. natans removed 56.6% when exposed to the same P solution (5 mg L⁻¹ P solution). Bioconcentration factor (BCF) values were higher in Salvinia natans 10.5 (0.5 mg L⁻¹ P solutions) and 1.5 (5 mg L⁻¹ P solutions) compared to 9.9 and 1.3 of Pistia stratiotes under P-starved conditions. The present work highlighted that these aquatic plants can be a potential green sustainable solution for purifying water with excessive nutrients (N and P), especially waters of wetlands, lagoons, and ponds. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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15 pages, 1639 KiB

Open AccessArticle

Seedling Establishment Test for the Comprehensive Evaluation of Compost Phytotoxicity

by Yuan Liu, Jiahui Liu, Hongyan Cheng, Yuan Luo, Kokyo Oh, Xiangzhuo Meng, Haibo Zhang, Na Liu and Mingchang Chang

Sustainability 2022, 14(19), 11920; https://doi.org/10.3390/su141911920 - 21 Sep 2022

Cited by 5 | Viewed by 1278

Abstract

Application of non-phytotoxic compost is important for soil conservation and crop production. In this study, two treatments were set up to compare the effects of compost water extract on the phytotoxicity of compost based on the dry weight and wet weight of samples [...] Read more.

Application of non-phytotoxic compost is important for soil conservation and crop production. In this study, two treatments were set up to compare the effects of compost water extract on the phytotoxicity of compost based on the dry weight and wet weight of samples and explore the feasibility of seedling establishment test in compost phytotoxicity evaluation—without (CM treatment) and with the addition of a microbial agent (ACM treatment)—based on the addition of corn straw and spent mushroom substrate in cow manure composting. The compost water extracts were prepared as per the wet weight (1:10, w/v) and dry weight (1:20, w/v) of fresh samples. The physicochemical characteristics of the compost water extracts, relative radicle growth, and chlorophyll content of the seed cotyledons of Chinese cabbage were determined. The results demonstrated that the highest electrical conductivity value of 3.95 mS∙cm⁻¹ was obtained for the CM treatment, based on the dry weight of the samples. The contents of nitrate-nitrogen, ammonium-nitrogen, total organic carbon, and total nitrogen under different extraction methods were significantly different between the different extraction methods. The addition of microbial agent effectively promoted compost maturity and increased the relative radicle growth and chlorophyll content of the cotyledons. At the end of composting, the relative radicle growth based on the wet weight of samples was higher—74.69% for the ACM treatment and 71.05% for the CM treatment, respectively. The chlorophyll content of the cotyledons demonstrated a similar pattern. Consequently, the phytotoxicity of the compost may be underestimated when the moisture content of the sample is high. The preparation of compost water extract based on the dry weight of the samples can therefore reflect phytotoxicity more accurately. Seedling establishment tests may be used to comprehensively evaluate compost phytotoxicity. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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18 pages, 4605 KiB

Open AccessArticle

Burkholderia cepacia Enhanced Electrokinetic-Permeable Reaction Barrier for the Remediation of Lead Contaminated Soils

by Yun He, Linlin Yang, Chiquan He and Feifei Wang

Sustainability 2022, 14(18), 11440; https://doi.org/10.3390/su141811440 - 13 Sep 2022

Viewed by 1188

Abstract

The combination of electrokinetic (EK) and permeable reactive barrier (PRB) is a potentially effective technology for the remediation of heavy-metal-contaminated soils, but high energy expenditure limits its application in practice. In order to further improve the remediation efficiency and reduce the cost, some [...] Read more.

The combination of electrokinetic (EK) and permeable reactive barrier (PRB) is a potentially effective technology for the remediation of heavy-metal-contaminated soils, but high energy expenditure limits its application in practice. In order to further improve the remediation efficiency and reduce the cost, some improvements were made in this study in terms of new PRB material, the spatial configuration of the rod electrode, and the microbial enhancement. Differently from previous powder PRB materials, six thin-film PRB materials were prepared using cheap natural attapulgite (ATP) and metal salts. PRB is a tough material that can be plugged and pulled out in engineering. The heavy metals adsorbed on it can be extracted from the soil, eliminating the risk of subsequent secondary pollution. Therefore, it has a strong operational ability. Among them, the FeMn-ATP material exhibited the best adsorption performance (2521 ± 377.1 mg/kg) for Pb. The results of the transmission electron microscope, X-ray diffractometer, and Fourier-transform infrared spectroscopy showed that iron and manganese were successfully loaded on the material. The Burkholderia cepacia pre-treatment led to soil pH decrease and the dissolution of Pb, and the morphological composition of Pb in the soil was also changed. In the microbial group, the adsorption amount of Pb by PRB at the anode and cathode increased by 69.1% and 42.1%, respectively. The concentration of the residual lead in the anode soil was significantly lower than that in the control group without microorganisms, and the removal rate of Pb was increased by 26%. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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12 pages, 1692 KiB

Open AccessArticle

Response of Castor Seedling Roots to Combined Pollution of Cd and Zn in Soils

by Feifei Wang, Linlin Yang, Yanping Zhao, Zhenzhen Zhao, Kokyo Oh and Chiquan He

Sustainability 2022, 14(17), 10702; https://doi.org/10.3390/su141710702 - 28 Aug 2022

Viewed by 1194

Abstract

Castors are used to remediate heavy-metal-polluted soils due to their good ability to accumulate heavy metals. However, only limited studies addressed the interaction between heavy metals and castor seedling roots. In this study, the physiological response of castor seedling roots to Cd and [...] Read more.

Castors are used to remediate heavy-metal-polluted soils due to their good ability to accumulate heavy metals. However, only limited studies addressed the interaction between heavy metals and castor seedling roots. In this study, the physiological response of castor seedling roots to Cd and Zn stress, and the change in trace elements in rhizosphere and non-rhizosphere soils were investigated. The results showed that, with an increase in Cd concentration, the accumulation of Zn in roots decreased by 20%, indicating a competition between Cd and Zn accumulation. The increase in Cd content enlarged the difference in nutrient contents at different depths: the amounts of P, Fe, and Mn were more in rhizosphere soils than in non-rhizosphere soils, while the amount of K showed an opposite trend. The addition of Cd and Zn stimulated root growth, but root activity was reduced. The addition of Cd and Zn affected the root cell morphology, including increases in the root cortex thickness and the root xylem area. The contents of the enzymes SOD, POD, and MDA increased with the addition of Cd and Zn, while the activity of CAT first increased and then decreased. There was no significant change in the soluble protein content. The decrease in IAA oxidase content, from 40.1% to 72.7%, was conducive to plant growth. To sum up, high contents of Cd and Zn in soils not only affect the root morphology and increase the gap in the contents of K, P, Fe, and Mn between rhizosphere and non-rhizosphere soils but also change the SOD, POD, MDA, and IAA contents in the root, so as to reduce the amount of root damage caused by the external environment. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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10 pages, 1191 KiB

Open AccessCommunication

Positive Effects and Optimal Ranges of Tea Saponins on Phytoremediation of Cadmium-Contaminated Soil

by Xiao-Lan Yu and Yong He

Sustainability 2022, 14(10), 5941; https://doi.org/10.3390/su14105941 - 13 May 2022

Cited by 2 | Viewed by 1405

Abstract

Confirming positive effects and offering optimal ranges of tea saponins on improving the efficiency of phytoremediation on cadmium is a prerequisite for applying tea saponins in field remediation. Existing studies qualitatively tested the feasibility of tea saponins on promoting the absorption of cadmium [...] Read more.

Confirming positive effects and offering optimal ranges of tea saponins on improving the efficiency of phytoremediation on cadmium is a prerequisite for applying tea saponins in field remediation. Existing studies qualitatively tested the feasibility of tea saponins on promoting the absorption of cadmium by hyperaccumulators in pots experiments, while this study investigated the effects of tea saponins on increasing the proportion of cadmium available fraction in contaminated soil quantitatively and confirmed tea saponins promoted the absorption by Portulaca oleracea in cadmium-contaminated water by independent soil experiments and hydroponic experiments. The results showed that for acquiring a higher proportion of cadmium available fraction, the concentration of tea saponins was negatively correlated with the concentration of cadmium contained in the soil, and the optimal treatment time of tea saponins was between 3–9 days depending on the cadmium concentration in contaminated soil. Using tea saponins could enhance the absorption of cadmium by Portulaca oleracea in a relatively short time to decrease the concentration of cadmium left in the contaminated water. The above findings help to deepen the understanding of tea saponins’ effects and use ranges on phytoremediation of cadmium both in soil and water and conduce studies on phytoremediation of other heavy-metal-contaminated soil and water with the help of tea saponins. Full article

(This article belongs to the Special Issue Phytoremediation Technologies for Soil and Water Resources Conservation)

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