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Safety Utilization and Remediation of Heavy Metal Polluted Farmland
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Safety Utilization and Remediation of Heavy Metal Polluted Farmland

A special issue of Toxics (ISSN 2305-6304). This special issue belongs to the section "Metals and Radioactive Substances".

Deadline for manuscript submissions: closed (15 October 2022) | Viewed by 29305

Special Issue Editor

Prof. Dr. Ying Feng

E-Mail Website
Guest Editor
College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
Interests: heavy metals; plant-microbe interaction; bioavailability; endophytic bacteria; phytoremediation; soil pollution and food safety
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

With the increase in agricultural inputs and rapid industrialization, heavy metal pollution in farmland has become extremely serious, affecting human health through the food chain. Although the area of pollution is very large, the amount of heavy metal in farmland is relatively low. Therefore, identifying ways in which to ensure the safe production of crops in those contaminated soils, reduce the total amount of toxics in soils, and achieve healthy soils is of great significance to promote agricultural sustainable development.

This Special Issue will focus on the whole process of “Safety Utilization and Remediation of Heavy Metal Polluted Farmland”, from pollution source identification to remediation effect evaluation. Authors are invited to submit original research papers, reviews, and short communications. The topics of interest may include, but are not limited to, the following:

1) Contamination source identification;

2) Transfer of heavy metals in the food chain;

3) Safety utilization of polluted farmland;

4) Bioremediation of contaminated soils;

5) Healthy soil cultivation;

6) Health risk assessment.

This Special Issue will provide opportunities to researchers and agricultural environmental professionals to discuss challenges and achievements regarding the remediation of heavy metal polluted farmland. Laboratory and field studies with novel research outcomes are warmly welcomed.

Prof. Dr. Ying Feng
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • heavy metals
  • source, transfer, accumulation
  • bioavailability and chemical speciation
  • immobilization and stabilization
  • intercropping
  • genotypic difference
  • biofertilizer
  • bioremediation
  • phytoremediation
  • plant–microbe interaction

Published Papers (15 papers)

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11 pages, 2103 KiB  
Article
Effect of Soil Washing with an Amino-Acid-Derived Ionic Liquid on the Properties of Cd-Contaminated Paddy Soil
by Yun Deng, Sheng Wang, Ian Beadham, Xin Gao, Mengmeng Ji, Guang Wang, Changbo Zhang and Wenquan Ruan
Toxics 2023, 11(3), 288; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics11030288 - 20 Mar 2023
Viewed by 1202
Abstract
To reduce contamination levels in Cd-contaminated paddy soil while retaining soil characteristics, we have studied the Cd-removing ability of 15 different amino acid-based ionic liquids, which are considered to be green solvents, as soil washing agents and their impact on soil. The results [...] Read more.
To reduce contamination levels in Cd-contaminated paddy soil while retaining soil characteristics, we have studied the Cd-removing ability of 15 different amino acid-based ionic liquids, which are considered to be green solvents, as soil washing agents and their impact on soil. The results indicated that the glycine hydrochloride ([Gly][Cl]) removed the most Cd, and under optimized conditions could remove 82.2% of the total Cd. Encouragingly, the morphology of the soil had not been significantly changed by the washing process. After the soil was rinsed twice with water and the pH was adjusted to 6.2 by adding Ca(OH)2, the germination index of the rice increased by 7.5%. The growth of the rice was also stimulated, with lengths and weights of the rice plants increasing by 56% and 32%, respectively, after two weeks. These experiments demonstrate that amino-acid-derived ionic liquids can be promising soil-washing agents of Cd-contaminated paddy soil. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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11 pages, 971 KiB  
Article
Role of Root Exudates in Cadmium Accumulation of a Low-Cadmium-Accumulating Tobacco Line (Nicotiana tabacum L.)
by Huagang Huang, Runze Lu, Juan Zhan, Jinsong He, Yong Wang and Tingxuan Li
Toxics 2023, 11(2), 141; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics11020141 - 01 Feb 2023
Cited by 4 | Viewed by 1540
Abstract
Root exudates are tightly linked with cadmium (Cd) uptake by the root and thus affect plant Cd accumulation. A hydroponic experiment was carried out to explore the role of root exudates in Cd accumulation of a low-Cd-accumulating tobacco line (RG11) compared with a [...] Read more.
Root exudates are tightly linked with cadmium (Cd) uptake by the root and thus affect plant Cd accumulation. A hydroponic experiment was carried out to explore the role of root exudates in Cd accumulation of a low-Cd-accumulating tobacco line (RG11) compared with a high-Cd- accumulating tobacco line (Yuyan5). Greater secretion of organic acids and amino acids by the roots was induced by an exogenous Cd addition in the two tobacco lines. The concentration of organic acid secreted by RG11 was only 51.1~61.0% of that secreted by Yuyan5. RG11 roots secreted more oxalic acid and acetic acid and less tartaric acid, formic acid, malic acid, lactic acid, and succinic acid than Yuyan5 under Cd stress. Oxalic acid accounted for 26.8~28.8% of the total organic acids, being the most common component among the detected organic acids, and was significantly negatively correlated with Cd accumulation in RG11. Propionic acid was only detected in the root exudates of RG11 under Cd stress. Lactic acid was positively linked with Cd accumulation in Yuyan5, being less accumulated in RG11. Similarly, RG11 secreted more amino acids than Yuyan5 under Cd stress. Aspartic acid, serine, and cysteine appeared in RG11 when it was exposed to Cd. Lysine was the most secreted amino acid in RG11 under Cd stress. RG11 roots secreted less lysine, histidine, and valine, but more phenylalanine and methionine than Yuyan5 under Cd stress. The results show that organic acids and amino acids in root exudates play a key role in Cd uptake by the root, and this contribution varied with cultivar/genotype. However, further research is still needed to explore the mechanisms underlying low Cd translocation to the leaf, which may be the key contribution of low Cd accumulation in RG11 to the security of tobacco leaf. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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11 pages, 1629 KiB  
Article
Effects of Exogenous Chlorinated Amino Acetic Acid on Cadmium and Mineral Elements in Rice Seedlings
by Shuangyue Liu, Lin Fu, Changbo Zhang, Jiawei Deng, Weijie Xue and Yun Deng
Toxics 2023, 11(1), 71; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics11010071 - 12 Jan 2023
Viewed by 1409
Abstract
To explore the effect of exogenous application of chlorinated amino acetic acid on cadmium (Cd) transport characteristics in rice seedlings, X24 and Z35 rice were taken as the research objects to carry out hydroponics experiments, and the changes of Cd content in rice [...] Read more.
To explore the effect of exogenous application of chlorinated amino acetic acid on cadmium (Cd) transport characteristics in rice seedlings, X24 and Z35 rice were taken as the research objects to carry out hydroponics experiments, and the changes of Cd content in rice seedlings, rice mineral elements and amino acid content in rice were analyzed. The results showed that exogenous application of 1.2 mmol·L−1 chlorinated amino acetic acid inhibited cadmium in shoots and roots of rice seedlings; Cd content in shoots and roots were reduced by up to 62.19% and 45.61%, respectively. The majority of cadmium was in the cell wall of shoots and roots; this decreased with the increase of the concentration of chlorinated acetic acid. In addition, the Mn content in shoots and Ca content in roots of rice seedlings increased significantly after the application of chlorinated amino acetic acid. The results of amino acid analysis showed that the contents of aspartic acid, glutamic acid and cystine in rice seedlings were increased. These results indicate that exogenous application of chlorinated amino acetic acid is beneficial to the synthesis of aspartic acid, glutamic acid and cysteine in rice seedlings, increases the content of Mn in shoots and Ca in roots of rice seedlings, and significantly alleviates cadmium stress in seedlings. This provides a theoretical basis for the development of an environmentally friendly Cd-lowering foliar fertilizer for rice. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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15 pages, 1040 KiB  
Article
Chromium Contamination and Health Risk Assessment of Soil and Agricultural Products in a Rural Area in Southern China
by Shun’an Xu, Chao Yu, Qiong Wang, Jiayuan Liao, Chanjuan Liu, Lukuan Huang, Qizhen Liu, Zheyu Wen and Ying Feng
Toxics 2023, 11(1), 27; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics11010027 - 27 Dec 2022
Cited by 6 | Viewed by 2482
Abstract
With the rapid development of industry, chromium (Cr) pollutants accumulate constantly in the soil, causing severe soil Cr pollution problems. Farmland Cr pollution hurts the safety of agricultural production and indirectly affects human health and safety. However, the current situation of Cr pollution [...] Read more.
With the rapid development of industry, chromium (Cr) pollutants accumulate constantly in the soil, causing severe soil Cr pollution problems. Farmland Cr pollution hurts the safety of agricultural production and indirectly affects human health and safety. However, the current situation of Cr pollution in farmland soil and crops has not been detailed enough. In this study, the evaluation of Cr potential risk in soil-crop systems was conducted in a rural area that was affected by industry and historic sewage irrigation. Ten different crops and rhizosphere soils were sampled from four fields. The results showed that Cr contents in farmland soil exceeded the national standard threshold in China (>21.85%), and the Cr content in edible parts of some agricultural products exceeded that too. According to the PCA and relation analysis, the Cr accumulation in edible parts showed a significant correlation with soil Cr contents and available potassium contents. Except for water spinach, the target hazard quotient (THQ) of the other crops was lower than 1.0 but the carcinogenic health risks all exceeded the limits. The carcinogenic risks (CR) of different types of crops are food crops > legume crops > leafy vegetable crops and root-tuber crops. A comprehensive assessment revealed that planting water spinach in this area had the highest potential risk of Cr pollution. This study provided a scientific and reliable approach by integrating soil environmental quality and agricultural product security, which helps evaluate the potential risk of Cr in arable land more efficiently and lays technical guidelines for local agricultural production safety. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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13 pages, 2467 KiB  
Article
In Vitro Bioaccessibility and Health Risk Assessment of Arsenic and Zinc Contaminated Soil Stabilized by Ferrous Sulfate: Effect of Different Dietary Components
by Yi Fang, Yuxue Cui, Xiaoli Mou, Li Lu, Jiali Shentu and Min Zhu
Toxics 2023, 11(1), 23; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics11010023 - 26 Dec 2022
Cited by 3 | Viewed by 2040
Abstract
Iron-based materials have good stability in reducing the mobility and toxicity of heavy metals, but the behavior and human health risks of heavy metals could be affected by dietary components. This study investigated the effect of typical diets (lettuce, cooked rice and apples) [...] Read more.
Iron-based materials have good stability in reducing the mobility and toxicity of heavy metals, but the behavior and human health risks of heavy metals could be affected by dietary components. This study investigated the effect of typical diets (lettuce, cooked rice and apples) on the bioaccessibility and morphological changes of arsenic (As) and zinc (Zn) in contaminated site after stabilization by ferrous sulfate (FeSO4). The results showed that the bioaccessibility of As and Zn were increased in a co-digestion system of food. The augmented effect on As bioaccessibility mainly occurred in the gastric phase: apple > lettuce > cooked rice (p < 0.05), while the augmented effect on Zn bioaccessibility mainly occurred in the intestinal phase: lettuce > apple > cooked rice (p < 0.05). FeSO4 weakened the dissolution effect of dietary components on As bioaccessibility, and reduced As bioaccessibility in the gastric and intestinal phases by 34.0% and 37.9% (p < 0.05), respectively. Dietary components and Fe fractions influenced the speciation and distribution of As and Zn. FeSO4 reduced the hazard quotient (HQ) and carcinogenic risk (CR) values of the contaminated soil by 33.97% and 33.59%, respectively. This study provides a reference for a better understanding of more realistic strategies to modulate exposure risks of heavy metal-contaminated sites. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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10 pages, 261 KiB  
Article
The Effect of “Production during Remediation” of Plants in Cd-Contaminated Soil
by Lankun Li and Huiqing Chang
Toxics 2022, 10(12), 732; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10120732 - 26 Nov 2022
Viewed by 1284
Abstract
In order to find suitable plants for “production during remediation” in wheat fields moderately contaminated by cadmium (Cd), five plants—green amaranth, oil sunflower, broomcorn, maize, and waxy maize—were planted in pots to study their enrichment characteristics and remediation effects in Cd-contaminated soil. The [...] Read more.
In order to find suitable plants for “production during remediation” in wheat fields moderately contaminated by cadmium (Cd), five plants—green amaranth, oil sunflower, broomcorn, maize, and waxy maize—were planted in pots to study their enrichment characteristics and remediation effects in Cd-contaminated soil. The results showed that the highest bioaccumulation and translocation factors were greater than 0.5 for oil sunflower, which had the strongest Cd-enrichment ability in Cd-contaminated soil, but its biomass was small, and the Cd content of the grain exceeded the standard (GB2762-2017). The Cd content in the grains of broomcorn, maize, and waxy maize was less than 0.1 mg∙kg−1, which is lower than the national food safety standard on limiting pollutants in food (GB2762-2017). Broomcorn accumulated 0.429 mg∙pot−1 for Cd, with a Cd-extraction efficiency of 1.73%, which were higher than other plants. Taking the risk-screening values in GB15618-2018 “Soil Environmental Quality Standard” as the target, it will take 80 years to remediate using broomcorn, which has the highest extraction efficiency, based on cultivating remediation plants once per year. However, in view of the scarcity of arable land resources in China and the objective of safe production during remediation, the use of broomcorn can be considered for production during remediation for the given degree of Cd contamination of the soil. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
16 pages, 3072 KiB  
Article
Biofortification Technology for the Remediation of Cadmium-Contaminated Farmland by the Hyperaccumulator Sedum alfredii under Crop Rotation and Relay Cropping Mode
by Haiyun Xie, Jiuzhou Chen, Yabei Qiao, Kuan Xu, Zhi Lin and Shengke Tian
Toxics 2022, 10(11), 691; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10110691 - 15 Nov 2022
Cited by 1 | Viewed by 1365
Abstract
Soil cadmium (Cd) extraction for hyperaccumulators is one of the most important technologies for the remediation of Cd-contaminated farmland soil. However, a phytoremediation model using a single hyperaccumulator cannot guarantee normal agricultural production in contaminated areas. To solve this problem, a combination of [...] Read more.
Soil cadmium (Cd) extraction for hyperaccumulators is one of the most important technologies for the remediation of Cd-contaminated farmland soil. However, a phytoremediation model using a single hyperaccumulator cannot guarantee normal agricultural production in contaminated areas. To solve this problem, a combination of efficient remediation and safe production has been developed. Based on two-period field experiments, this study explored the effect of biofortification on soil Cd remediation using the fruit tree Sedum alfredii Hance and oil sunflower crop rotation and relay cropping mode. BioA and BioB treatments could markedly improve the efficiency of Cd extraction and remediation, and the maximum increase in Cd accumulation was 243.29%. When BioB treatment was combined with papaya–S. alfredii and oil sunflower crop rotation and relay cropping mode, the highest soil Cd removal rate in the two periods was 40.84%, whereas the Cd concentration of papaya fruit was lower than safety production standards (0.05 mg/kg). These results demonstrate that biofortification measures can significantly improve the Cd extraction effect of S. alfredii crop rotation and relay cropping restoration modes, which has guiding significance for Cd pollution remediation and safe production in farmland. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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11 pages, 918 KiB  
Article
Assessing Pb-Cr Pollution Thresholds for Ecological Risk and Potential Health Risk in Selected Several Kinds of Rice
by Mengzhuo Cao, Weijing Zhu, Leidong Hong, Weiping Wang, Yanlai Yao, Fengxiang Zhu, Chunlai Hong and Shanying He
Toxics 2022, 10(11), 645; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10110645 - 27 Oct 2022
Cited by 1 | Viewed by 1120
Abstract
The expected typical gley moist paddy soil was collected in Zhejiang Province, China, and conventional (XS 134 and JH 218) and varieties of hybrid (YY 538 and CY 84) rices were used for a pot experiment. The effects of exogenous heavy metals lead [...] Read more.
The expected typical gley moist paddy soil was collected in Zhejiang Province, China, and conventional (XS 134 and JH 218) and varieties of hybrid (YY 538 and CY 84) rices were used for a pot experiment. The effects of exogenous heavy metals lead (Pb) and chromium (Cr) on rice growth and the accumulation of heavy metals in the grains were studied. The results show that heavy metal concentrations in soil and rice grains have significant correlations, and Pb and Cr significantly (p < 0.05) inhibited the rice growth (plant height and panicle weight). The potential ecological hazard index (RI) of heavy metals in the soil was 4.88–6.76, which belongs to the grade of “slight ecological hazard”, and Pb provides a larger potential ecological hazard than Cr in the studied region. The thresholds for potential health risks and ecological risks for Pb and Cr were lower than the “Control Standards for Soil Pollution Risk of Agricultural Land (Trial)” (GB15618-2018, China). This work provides the basis for soil pollution control for Pb and Cr and the selection of rice cultivars from Pb and Cr accumulated soils. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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16 pages, 10973 KiB  
Article
Contamination and Health Risk Assessment of Heavy Metals in Soil and Ditch Sediments in Long-Term Mine Wastes Area
by Bo Li, Jiangdi Deng, Zuran Li, Jianjun Chen, Fangdong Zhan, Yongmei He, Lu He and Yuan Li
Toxics 2022, 10(10), 607; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10100607 - 13 Oct 2022
Cited by 8 | Viewed by 1652
Abstract
The ecological and health risks posed by wastes discharged from mining areas to the environment and human health has aroused concern. 114 soil samples were collected from nine areas of long-term mine waste land in northwestern Yunnan to assess the pollution characteristics, ecological [...] Read more.
The ecological and health risks posed by wastes discharged from mining areas to the environment and human health has aroused concern. 114 soil samples were collected from nine areas of long-term mine waste land in northwestern Yunnan to assess the pollution characteristics, ecological and health risks of heavy metals. The result revealed that the geo-accumulation indexes were Cd (4.00) > Pb (3.18) > Zn (1.87) > Cu (0.25). Semi-variance analysis revealed that Cd and Cu showed moderate spatial dependency, whereas Pb and Zn showed strong spatial dependency. Cd posed an extreme potential ecological risk. Slopes and ditches were extreme potential ecological risk areas. Non-carcinogenic risk to children from Pb and Carcinogenic risk to adult and children from Cd was non-negligible and direct ingestion was the major source. This study provided a scientific basis for policymakers in management and exposure reduction. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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13 pages, 1926 KiB  
Article
Arbuscular Mycorrhizal Fungal Inoculation Increases Organic Selenium Accumulation in Soybean (Glycine max (Linn.) Merr.) Growing in Selenite-Spiked Soils
by Zengyu Zhang, Bei Li, Yongxian Liu, Lixin He, Ting Pang, Zongdao Chen, Md. Jahidul Islam Shohag, Xiuyan Miao, Xi Li, Minghua Gu and Yanyan Wei
Toxics 2022, 10(10), 565; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10100565 - 26 Sep 2022
Cited by 2 | Viewed by 1480
Abstract
Selenium (Se) is an essential trace element for humans. Arbuscular mycorrhizal fungi (AMF) play a crucial role in increasing plant micronutrient acquisition. Soybean (Glycine max (Linn.) Merr.) is a staple food for most people around the world and a source of Se. [...] Read more.
Selenium (Se) is an essential trace element for humans. Arbuscular mycorrhizal fungi (AMF) play a crucial role in increasing plant micronutrient acquisition. Soybean (Glycine max (Linn.) Merr.) is a staple food for most people around the world and a source of Se. Therefore, it is necessary to study the mechanism of Se intake in soybean under the influence of AMF. In this study, the effects of fertilization with selenite and inoculation with different AMF strains (Claroideoglomus etunicatum (Ce), Funneliformis mosseae (Fm)) on the accumulation and speciation of Se in common soybean plants were discussed. We carried out a pot experiment at the soil for 90 days to investigate the impact of fertilization with selenite and inoculation with Ce and Fm on the Se fractions in soil, soybean biomass, accumulation and speciation of Se in common soybean plants. The daily dietary intake of the Se (DDI) formula was used to estimate the risk threshold of human intake of Se from soybean seeds. The results showed that combined use of both AMF and Se fertilizer could boost total Se and organic Se amounts in soyabean seeds than that of single Se application and that it could increase the proportion of available Se in soil. Soybean inoculated with Fm and grown in soil fertilized with selenite had the highest organic Se. The results suggest that AMF inoculation could promote root growth, more soil water-soluble Se and higher Se uptake. The maximum Se intake of soybean for adults was 93.15 μg/d when treated with Se fertilizer and Fm, which satisfies the needs of Se intake recommended by the WHO. Combined use of AMF inoculation and Se fertilizer increases the bioavailable Se in soil and promotes the total Se concentration and organic Se accumulation in soybean. In conclusion, AMF inoculation combined with Se fertilization can be a promising strategy for Se biofortification in soybean. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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11 pages, 2306 KiB  
Article
Combined Plant Growth-Promoting Bacteria Inoculants Were More Beneficial than Single Agents for Plant Growth and Cd Phytoextraction of Brassica juncea L. during Field Application
by Qiong Wang, Shun’an Xu, Zheyu Wen, Qizhen Liu, Lukuan Huang, Guosheng Shao, Ying Feng and Xiaoe Yang
Toxics 2022, 10(7), 396; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10070396 - 17 Jul 2022
Viewed by 2569
Abstract
Single or combined plant growth-promoting bacteria (PGPB) strains were widely applied as microbial agents in cadmium (Cd) phytoextraction since they could promote plant growth and facilitate Cd uptake. However, the distinct functional effects between single and combined inoculants have not yet been elucidated. [...] Read more.
Single or combined plant growth-promoting bacteria (PGPB) strains were widely applied as microbial agents in cadmium (Cd) phytoextraction since they could promote plant growth and facilitate Cd uptake. However, the distinct functional effects between single and combined inoculants have not yet been elucidated. In this study, a field experiment was conducted with single, double and triple inoculants to clarify their divergent impacts on plant growth, Cd uptake and accumulation at different growth stages of Brassica juncea L. by three different PGPB strains (Cupriavidus SaCR1, Burkholdria SaMR10 and Sphingomonas SaMR12). The results show that SaCR1 + SaMR10 + SaMR12 combined inoculants were more effective for growth promotion at the bud stage, flowering stage, and mature stage. Single/combined PGPB agents of SaMR12 and SaMR10 were more efficient for Cd uptake promotion. In addition, SaMR10 + SaMR12 combined the inoculants greatly facilitated Cd uptake and accumulation in shoots, and enhanced the straw Cd extraction rates by 156%. Therefore, it is concluded that the application of PGPB inoculants elevated Cd phytoextraction efficiency, and the combined inoculants were more conductive than single inoculants. These results enriched the existing understanding of PGPB agents and provided technical support for the further exploration of PGPB interacting mechanisms strains on plant growth and Cd phytoextraction, which helped establish an efficient plant–microbe combined phytoremediation system and augment the phytoextraction efficiency in Cd-contaminated farmlands. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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12 pages, 987 KiB  
Article
Effect of Hypoxic Stress and Levels of Mn on the Physiology and Biochemistry of Phyllostachys praecox
by Jiawei Ma, Gul Rukh, Zhengqian Ye, Xiaocui Xie, Zhongqiang Ruan and Dan Liu
Toxics 2022, 10(6), 290; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10060290 - 27 May 2022
Viewed by 1466
Abstract
Hypoxic environments have an adverse effect on the growth and development of P. praecox, and this is accompanied by the production of reducing substances such as Fe and Mn. In this study, the effect of hypoxic stress and Mn concentrations on leaf [...] Read more.
Hypoxic environments have an adverse effect on the growth and development of P. praecox, and this is accompanied by the production of reducing substances such as Fe and Mn. In this study, the effect of hypoxic stress and Mn concentrations on leaf chlorophyll contents, root morphology, root activity, element absorption, antioxidant enzymes, and respiratory enzyme system of P. praecox were evaluated in a hydroponics environment. The results revealed that application of Mn2+ during hypoxic stress enhanced leaf chlorophyll contents and boosted up the indexes of the root system. The root activity of P. praecox was reduced with stresses of hypoxia. The treatment of Mn2+ initially improved and then decreased the root activity of P. praecox, and attained its maximum with application of 300 μmol/L Mn2+ compared with control. The indexes of antioxidant enzymes of P. praecox were higher than that of 8 mg/L oxygen concentrations except for variable superoxide dismutase (SOD) in the treatment of 300 μmol/L Mn2+ with hypoxia stress. The application of Mn had inhibited the absorption of mineral elements in P. praecox. The activities of pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), and lactic dehydrogenase (LDH) were initially improved and then diminished with hypoxia stress. It is concluded that hypoxia is a key factor affecting the growth and degradation of P. praecox, while combining it with the increase of Mn concentration enhances the damage to Phyllostachys pubescens. Our research is helpful for the sustainable management and scientific fertilization management of Phyllostachys praecox. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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14 pages, 1101 KiB  
Article
Enhanced Cd Phytoextraction by Solanum nigrum L. from Contaminated Soils Combined with the Application of N Fertilizers and Double Harvests
by Wei Yang, Huiping Dai, Lidia Skuza and Shuhe Wei
Toxics 2022, 10(5), 266; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10050266 - 19 May 2022
Cited by 1 | Viewed by 1511
Abstract
It is very important to increase phytoremediation efficiency in practice in suitable climatic conditions for plant growth through multiple harvests. Solanum nigrum L. is a Cd hyperaccumulator. In the present experiment, after applying different types of N fertilizers (NH4HCO3, [...] Read more.
It is very important to increase phytoremediation efficiency in practice in suitable climatic conditions for plant growth through multiple harvests. Solanum nigrum L. is a Cd hyperaccumulator. In the present experiment, after applying different types of N fertilizers (NH4HCO3, NH4Cl, (NH4)2SO4, CH4N2O), root and shoot biomasses and Cd phytoextraction efficiency of S. nigrum effectively improved (p < 0.05). Shoot biomasses of S. nigrum harvested at the first florescence stage plus the amounts at the second florescence stage were higher than those harvested at the maturation stage, which indicates that S. nigrum Cd phytoaccumulation efficiency was higher in the former compared to the latter as there was no clear change in Cd concentration (p < 0.05). The pH value and extractable Cd contents showed no changes, regardless of whether N fertilizer was added or not at different growth stages. In addition, after N fertilizer was applied, H2O2 and malondialdehyde (MDA) contents in S. nigrum in vivo were lower compared to those that had not received N addition (CK); similarly, the concentration of proline was decreased as well (p < 0.05). The activity of the antioxidant enzyme catalase (CAT), harvested at different growth periods after four types of N fertilizer applications, obviously decreased in S. nigrum shoots, while peroxidase (POD) and superoxide dismutase) (SOD) activities increased (p < 0.05). Our study demonstrated that (NH4)2SO4 treatment exerted the most positive effect and CH4N2O the second most positive effect on S. nigrum Cd phytoremediation efficiency in double harvests at florescence stages, and the growth conditions were better than others. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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15 pages, 1033 KiB  
Article
Multi-Component Passivators Regulate Heavy Metal Accumulation in Paddy Soil and Rice: A Three-Site Field Experiment in South China
by Shouping Zhao, Xuezhu Ye, De Chen, Qi Zhang, Wendan Xiao, Shaofu Wu, Jing Hu, Na Gao and Miaojie Huang
Toxics 2022, 10(5), 259; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10050259 - 18 May 2022
Cited by 2 | Viewed by 1665
Abstract
To fulfill sustainability principles, a three-site field experiment was conducted to screen suitably mixed passivators from lime + biochar (L + C, 9000 kgha−1 with a rate of 1:1) and lime + biochar + sepiolite (L + C + S, 9000 kg [...] Read more.
To fulfill sustainability principles, a three-site field experiment was conducted to screen suitably mixed passivators from lime + biochar (L + C, 9000 kgha−1 with a rate of 1:1) and lime + biochar + sepiolite (L + C + S, 9000 kg ha−1 with a rate of 1:1:1), in Yuecheng (YC), Zhuji (ZJ), and Fuyang (FY), where there are typical contaminated soils, in South China. Treated with passivators in soil, DTPA-extractable Cd, Crand Pb in soil were decreased by 9.87–26.3%, 37.2–67.5%, and 19.0–54.2%, respectively; Cd, Cr, and Pb in rice were decreased by 85.9–91.5%, 40.0–76.5%, and 16.4–45.4%, respectively; and these were followed by slightly higher efficacy of L + C + S than L + C. The differences between L + C and L + C + S mainly lie in soil microbial communities, enzymes, and fertility. In YC, treatment with L + C + S increased microbial carbon and activities of urease (EC3.5.1.5) and phosphatase (EC3.1.3.1) by 21.0%, 85.5%, and 22.3%; while treatment with L + C decreased microbial carbon and activities of phosphatase and sucrose (EC3.2.1.26) by 1.31%, 34.9%, and 43.4%, respectively. Moreover, the treatment of FY soils with L + C + S increased microbial carbon and activities of urease, phosphatase, and sucrase by 35.4%, 41.6%, 27.9%, and 7.37%; and L + C treatment only increased the microbial carbon and the activity of phosphatase by 3.14% and 30.3%, respectively. Furthermore, the organic matter and available nitrogen were also increased by 8.8–19.0% and 7.4–14.6% with L + C + S treatments, respectively. These suggested that the combination of L + C + S stimulated the growth of soil microbial communities and increased the activity of soil enzymes. Therefore, the L + C + S strategy can be a practical and effective measure for safe rice production as it was more suitable for the remediation of heavy metals in our experimental sites. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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17 pages, 727 KiB  
Review
Advances in Genes-Encoding Transporters for Cadmium Uptake, Translocation, and Accumulation in Plants
by Jingyu Tao and Lingli Lu
Toxics 2022, 10(8), 411; https://0-doi-org.brum.beds.ac.uk/10.3390/toxics10080411 - 22 Jul 2022
Cited by 41 | Viewed by 5287
Abstract
Cadmium (Cd) is a heavy metal that is highly toxic for plants, animals, and human beings. A better understanding of the mechanisms involved in Cd accumulation in plants is beneficial for developing strategies for either the remediation of Cd-polluted soils using hyperaccumulator plants [...] Read more.
Cadmium (Cd) is a heavy metal that is highly toxic for plants, animals, and human beings. A better understanding of the mechanisms involved in Cd accumulation in plants is beneficial for developing strategies for either the remediation of Cd-polluted soils using hyperaccumulator plants or preventing excess Cd accumulation in the edible parts of crops and vegetables. As a ubiquitous heavy metal, the transport of Cd in plant cells is suggested to be mediated by transporters for essential elements such as Ca, Zn, K, and Mn. Identification of the genes encoding Cd transporters is important for understanding the mechanisms underlying Cd uptake, translocation, and accumulation in either crop or hyperaccumulator plants. Recent studies have shown that the transporters that mediate the uptake, transport, and accumulation of Cd in plants mainly include members of the natural resistance-associated macrophage protein (Nramp), heavy metal-transporting ATPase (HMA), zinc and iron regulated transporter protein (ZIP), ATP-binding cassette (ABC), and yellow stripe-like (YSL) families. Here, we review the latest advances in the research of these Cd transporters and lay the foundation for a systematic understanding underlying the molecular mechanisms of Cd uptake, transport, and accumulation in plants. Full article
(This article belongs to the Special Issue Safety Utilization and Remediation of Heavy Metal Polluted Farmland)
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