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1.
A critical review on the effects of zinc at toxic levels of cadmium in plants.
Rizwan, M, Ali, S, Rehman, MZU, Maqbool, A
Environmental science and pollution research international. 2019;(7):6279-6289
Abstract
Increasing cadmium (Cd) pollution in agricultural soils has raised serious concerns worldwide. Several exogenous substances can be used to mitigate the toxic effects of Cd in plants. Zinc (Zn) is one of the essential plant micronutrients and is involved in several physiological functions in plants. Zn may alleviate Cd toxicity in plants owing to the chemical similarity of Zn with Cd. Published reports demonstrated that Zn can alleviate toxic effects of Cd in plants by increasing plant growth, regulating Cd uptake, increasing photosynthesis, and reducing oxidative stress. Literature demonstrated that the role of Zn on Cd accumulation by plants is very controversial and depends upon several factors including concentrations of Cd and Zn in the medium, exposure duration, plant species and genotypes, and growth conditions. This review highlights the role of Zn in reducing Cd toxicity in plants and provides new insight that proper level of Zn in plants may enhance plant resistance to excess Cd.
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2.
Copper environmental toxicology, recent advances, and future outlook: a review.
Rehman, M, Liu, L, Wang, Q, Saleem, MH, Bashir, S, Ullah, S, Peng, D
Environmental science and pollution research international. 2019;(18):18003-18016
Abstract
Copper (Cu) is one of the micronutrients needed by living organisms. In plants, Cu plays key roles in chlorophyll formation, photosynthesis, respiratory electron transport chains, oxidative stress protection as well as protein, carbohydrate, and cell wall metabolism. Therefore, deficiency of Cu can alter various functions of plant metabolism. However, Cu-based agrochemicals have traditionally been used in agriculture and being excessively released into the environment by anthropogenic activities. Continuous and extensive release of Cu is an imperative issue with various documented cases of phytotoxicity by the overproduction of reactive oxygen species (ROS) and damage to carbohydrates, lipids, proteins, and DNA. The mobility of Cu from soil to plant tissues has several concerns including its adverse effects on humans. In this review, we have described about importance and occurrence of Cu in environment, Cu homeostasis and toxicity in plants as well as remediation and progress in research so far done worldwide in the light of previous findings. Furthermore, present review provides a comprehensive ecological risk assessment on Cu in soils and thus provides insights for agricultural soil management and protection.
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3.
Interactive effects between cadmium stabilized by palygorskite and mobilized by siderophores from Pseudomonas fluorescens.
Jiang, JJ, Wang, JF, Yang, P, Xu, ZM, He, T, Gao, Q, Wang, LL, Li, QS
Ecotoxicology and environmental safety. 2019;:265-273
Abstract
The application of palygorskite (PAL) for potentially toxic trace elements (Cd2+, Ni2+, etc.) remediation in polluted soil can substantially reduce the bioavailability and toxicity of these hazard materials. However, the secretion of organic acids and siderophores by microorganisms might result in the re-mobilization of cadmium (Cd) in PAL-bound forms (PAL-Cd). In this study, the interactive effects between Cd stabilized by PAL and mobilized by siderophores from Pseudomonas fluorescens were performed with four flask-shaking experimental treatments, namely, strain with or without an ability of siderophores production respectively associated with or without PAL-Cd. The GC-MS and UHPLC-MS test methods were used to analyze the concentrations of metabolites. Results showed that the Cd mobilized by strain with siderophores production was 22.1% higher than that of strain without the ability of siderophores production (p < 0.05). The mobilization of Cd in PAL in turn significantly reduced the siderophores production of Pseudomonas fluorescens by 25.1% (p < 0.05). The numbers of metabolites significantly up-regulated and down-regulated were 9 and 22 in strain groups with PAL-Cd addition compared with the groups without PAL-Cd, respectively. Metabolomics analysis revealed that the mobilized Cd affects the signal transduction pathway and primary metabolic processes, reduces the metabolic capacity of pentose phosphate pathway, glycolysis and tricarboxylic acid cycle pathway. These changes inhibit the ability of strain to biosynthesize amino acids during the mobilization processes, further reducing the capacity of Pseudomonas fluorescens to produce siderophores. This study provides a useful information on how to select soil Cd-stabilizing materials in a targeted manner and how to avoid Cd re-mobilization by siderophores.
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4.
Chemical Forms and Health Risk of Cadmium in Water Spinach Grown in Contaminated Soil with an Increased Level of Phosphorus.
Lam, CM, Chen, KS, Lai, HY
International journal of environmental research and public health. 2019;(18)
Abstract
(1) Background: Even in croplands with a low concentration of cadmium (Cd), there is still a risk for planting crops because of the high accumulation capacity of some leafy vegetables. (2) Methods: In this study, water spinach was planted in four main soil series (Wa, Eh, Tk, and Yu) in central Taiwan, which were spiked with Cd. The soil available phosphorous content was increased to 10-17 mg/kg, and the accumulation and developed chemical forms of Cd were analyzed. (3) Results: The experimental results showed that addition of phosphorous to Wa and Eh promoted the growth of water spinach. Accumulation and upward translocation of Cd were also increased in the phosphorus treatment compared with the control. The addition of phosphorus increased the percentage of Cd compartmentalized in undissolved Cd phosphate, which revealed that the mobility and toxicity of Cd were reduced in the phosphorus treatment. However, most of the water spinach was not edible because the vegetable-induced hazard quotient, which was calculated using three methods, showed hazardous potential in general.
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5.
Evaluation of the potential of sewage sludge as a valuable fertilizer for wheat (Triticum aestivum L.) crops.
Eid, EM, Alrumman, SA, El-Bebany, AF, Fawy, KF, Taher, MA, Hesham, AE, El-Shaboury, GA, Ahmed, MT
Environmental science and pollution research international. 2019;(1):392-401
Abstract
A greenhouse experiment was performed to assess the soil heavy metal pools, growth, yield, and heavy metal uptake of wheat plants (Triticum aestivum L.) that are grown at different rates in soils supplemented with sewage sludge (SS). The experimental design was completely randomized, with six replicates per treatment. The application of SS significantly increased the soil organic matter content. Generally, most growth parameters, as well as the biomass of treated wheat, were significantly increased with the amendment of SS, up to the addition rate of 40 g kg-1. The content of all heavy metals (except Cr in grains and Pb in spikes) significantly increased in different tissues of treated wheat with the increasing rate of SS application. However, all heavy metal concentrations (except for Al, Cr, Fe, and Mn in the roots) were normal and did not overcome the phytotoxic levels. The wheat was recognized by a bioaccumulation factor < 1.0 for most of the heavy metals. The translocation factor for all of the heavy metals was < 1.0. Therefore, the SS utilized in the present study could be used as a valuable organic fertilizer in wheat cultivation areas in Saudi Arabia and could also act as an eco-friendly method for the recycling of SS.
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6.
Effects of Farming Activities on the Biogeochemistry of Mercury in Rice-Paddy Soil Systems.
Tang, W, Su, Y, Gao, Y, Zhong, H
Bulletin of environmental contamination and toxicology. 2019;(5):635-642
Abstract
The biogeochemistry of mercury (Hg) in rice-paddy soil systems raises concerns, given that (1) the redox potential in paddy soil favors Hg methylation and (2) rice plants have a strong ability to accumulate methylmercury (MeHg), making rice an important source for MeHg exposure to humans. Therefore, all factors affecting the behavior of Hg in rice-paddy soils might impact Hg accumulation in rice, with its subsequent potential risks. As a typical wetland, paddy soils are managed by humans and affected by anthropogenic activities, such as agronomic measures, which would impact soil properties and thus Hg biogeochemistry. In this paper, we reviewed recent advances in the effects of farming activities including water management, fertilizer application and rotation on Hg biogeochemistry, trying to elucidate the factors controlling Hg behavior and thus the ecological risks in rice-paddy soil systems. This review might provide new thoughts on Hg remediation and suggest avenues for further studies.
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7.
Pre-aeration of the rhizosphere offers potential for phytoremediation of heavy metal-contaminated wetlands.
Xin, J, Tang, J, Liu, Y, Zhang, Y, Tian, R
Journal of hazardous materials. 2019;:437-446
Abstract
Two solution cultures with different oxygen pretreatments were used to investigate (ⅰ) the variation in the radial oxygen loss in the roots and root morphology of Triarrhena sacchariflora seedlings and (ii) their tolerance to Cu2+ and Cd2+, as well as both the metal uptake and accumulation by pretreated seedlings. Developed aerenchyma in the roots was induced by the hypoxia pretreatment (HP) and aeration pretreatment (AP), for which root porosity, respectively, increased by 45.76%-53.39% and 84.07%-88.66%. AP altered the natural radial oxygen loss coupled to an enhanced secretion of oxygen in the root tips. AP was found to effectively improve the seedlings' tolerance to Cu2+ and Cd2+, facilitating their growth, thereby increasing their root diameter, dry weight, and number of root tips, as well as promoting shoot growth. AP was capable of promoting the uptake and bioaccumulation in seedlings of Cu2+ and Cd2+; it also induced more Cu2+ and Cd2+ immobilized in roots so that less of either metal was transported from roots to shoots, which may well be a key mechanism for strengthening seedlings' tolerance to metal ions. Our experimental results suggest that AP offers great potential for the remediation of heavy metal-contaminated wetlands.
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8.
Effect of salicylic acid and mycorrhizal symbiosis on improvement of fluoranthene phytoremediation using tall fescue (Festuca arundinacea Schreb).
Rostami, M, Rostami, S
Chemosphere. 2019;:70-75
Abstract
Polycyclic aromatic hydrocarbons are an important group of pollutants that are widely distributed in the environment. The present study aimed to investigate the effect of salicylic acid (a phenolic phytohormone) and mycorrhizal fungi on the growth and phytoremediation ability of tall fescue in the soil contaminated by fluoranthene. The initial concentrations of fluoranthene in this study were 100, 200, and 300 mg kg-1. The experimental treatments were included: T0 uncultivated soil; T1 cultivated soil with tall fescue; T2 cultivated soil with tall fescue + salicylic acid application; T3 cultivated soil with tall fescue + application of mycorrhizal fungi; T4 cultivated soil with tall fescue + salicylic acid and mycorrhizal fungi application; and P planting tall fescue in uncontaminated soil. The removal of fluoranthene was measured after 90 days. Furthermore, at the end of the experiment, the amount of shoot and root biomass, soil bacteria, and dehydrogenase activity were measured. According to the results, in all levels of contamination, removal of fluoranthene in cultivated treatments significantly was higher than uncultivated treatments. Increasing the concentration of fluoranthene had a negative effect on the shoot and root biomass in different treatments. Salicylic acid and mycorrhizal fungi significantly increased the shoot and root biomass and also the number of soil bacteria, dehydrogenase activity, and fluoranthene removal in T2, T3, and T4 treatments compared to T1. At the highest concentration of fluoranthene, as a result of simultaneous application of salicylic acid and mycorrhizal fungi (T4), the fluoranthene removal increased by 63, 21, 13, and 16% in comparison with T0, T1, T2, and T3, respectively. Based on the results, salicylic acid and mycorrhizal fungi, either alone or in combination, have a significant effect on the improvement of phytoremediation potential in tall fescue.
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9.
Accumulation of heavy metals and biochemical responses in Siberian larch needles in urban area.
Vladimirovna Afanasyeva, L, Ayushievna Ayushina, T
Ecotoxicology (London, England). 2019;(5):578-588
Abstract
Active urbanization processes exacerbate environmental problems associated with industrial pollution in cities. Urban greening helps reduce level of air pollution and improve microclimate. Selection sensitive plant species (indicators of pollution), and the resistant species (decrease the level pollution) is acute in many countries. The aim of the present work was to establish concentrations of heavy metals (Fe, Mn, Zn, Cu, Ni, Cr, Pb, Co and Cd) in the Siberian larch needles grown in various urban land-use (functional) zones of Ulan-Ude (Russia), as well as to determinate and compare the levels of some biochemical compounds. Based on index of soil contamination, the highest heavy metal pollution was found in the highway and industrial zones. The index of biogeochemical transformation of the needle elements composition ranged from 5.1 (minimal level) to 32.2 (strong level). The most polluted sites were along highways, where Fe, Zn, Cu, Cr, Ni, Pb, and Cd concentration in the needles were up to 2.5-7.7 times than background values. An important role in the protective system of larch is played by pigments, especially Chl b and carotenoids. Their content in the needles is increased by 1.3-2.2 times. Ratio Chl a/b and ∑Chl/carotenoids decrease as compared to background level; in the first case-due to increase of Chl b content, in the second case-increase of carotenoids level. Highest concentrations of proline, condensed tannins and peroxidase activity were found in needles from urban zones connected with high traffic and industrial emission. Based on the Air Pollution Tolerance Index Siberian larch should be considered sensitive species to air pollution and can be recommended as bioindicator.
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10.
Plant-microbiome assisted and biochar-amended remediation of heavy metals and polyaromatic compounds ─ a microcosmic study.
Sarma, H, Sonowal, S, Prasad, MNV
Ecotoxicology and environmental safety. 2019;:288-299
Abstract
The study has been carried out to develop a plant-microbes assisted remediation technology to accelerate polyaromatic hydrocarbons (PAHs) degradation and heavy metals (HMs) removal in a microcosmic experiment. The quaternary mixture of PAHs (phenanthrene, anthracene, pyrene, and benzo[a] pyrene) and metals (Cr, Ni, and Pb) spiked the soil, constructing a microcosm; the microcosms were bioaugmented with newly developed plant bacterial consortia (Cpm1 and Cpm2). The microcosms were amended with biochar (sieved particle size 0.5-2 mm) as redox regulators to reduce oxidative stress of plant-microbe systems. To formulate the two plant-bacterial consortia, plant species were collected and bacteria were isolated from oil spill soil. The bacterial strains used in two formulated consortia includes ─ Cpm1 (Enterobacter cloacae HS32, Brevibacillus reuszeri HS37, and Stenotrophomonas sp. HS16) and Cpm2 (Acinetobacter junii HS29, Enterobacter aerogenes HS39 and Enterobacter asburiae HS22). The PAHs degradation and metal removal efficacy of the consortia (Cpm1 and Cpm2) were studied after 24 weeks of trial. The physicochemical properties of microcosm's soil (M2 and M3) were assessed after experimentation, which resulted in the finding that the soil exhibits dropped in pH from basic to neutral after application of the plant microbe's consortium. The electrical conductivity was lower in M2 and M3 soils, with a range between 1.60 and 1.80 mS/cm after the treatment. The Gas Chromatography/Mass Spectrometry (GC/MS) results illustrate how metabolites with the different molecular weight (M.W) were found in M2 and M3 soils (184─446), as a result of the plant-microbes mediated rhizodegradation of four spiked PAHs. The metals in microcosm's soil are very low in concentration after 24 weeks of trial when compared to control(M1). The Cr, Ni and Pb removal percentages were found in 45.79, 42.19 and 44.85 in M2. However, the removal percentages were found to be 45.41, 41.47 and 44.25 respectively for these same HMs in M3 soil. Both the consortia that were newly developed showed similar trends of metals removal and PAHs degradation. This study provides a breakthrough in the area of rhizosphere engineering with the goal of maintaining a sustainable application of plant-microbes in ecosystem services.