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Heavy metals and metalloids (HMs) contamination in the environment has heightened recently due to increasing global concern for food safety and human livability. Zinc (Zn2+) is an important nutrient required for the normal development of plants. It is an essential cofactor for the vital enzymes involved in various biological mechanisms of plants. Interestingly, Zn2+ has an additional role in the detoxification of HMs in plants due to its unique biochemical-mediating role in several soil and plant processes. During any exposure to high levels of HMs, the application of Zn2+ would confer greater plant resilience by decreasing oxidative stress, maintaining uptake of nutrients, photosynthesis productivity and optimising osmolytes concentration. Zn2+ also has an important role in ameliorating HMs toxicity by regulating metal uptake through the expression of certain metal transporter genes, targeted chelation and translocation from roots to shoots. This review examined the vital roles of Zn2+ and nano Zn in plants and described their involvement in alleviating HMs toxicity in plants. Moving forward, a broad understanding of uptake, transport, signalling and tolerance mechanisms of Zn2+/zinc and its nanoparticles in alleviating HMs toxicity of plants will be the first step towards a wider incorporation of Zn2+ into agricultural practices. Heavy metals and metalloids pollution in the environment, particularly in soils, has gained increased attention globally. Zn2+ is a crucial nutrient for tolerance against heavy metals. This review illustrates the vital role of Zn2+ and nano Zn in plants and explains the knowledge of their impact in alleviating HMMs toxicity in plants. [ABSTRACT FROM AUTHOR]

Aquatic bodies contaminated by heavy metals (HMs) are one of the leading issues due to rapidly growing industries. The remediation of using algae and hydrophytes acts as an environmentally friendly and cost effective. This study was performed to investigate the pollution load, especially HMs, in the wastewater of the Gadoon Industrial Estate and to utilize the hydrophytes (Typha latifolia (TL) and Eicchornia crassipes (EI)) and algae (Zygnema pectiantum (ZP) and Spyrogyra species (SS)) as bioremediators. The wastewater was obtained and assessed for physiochemical parameters before treating with the selected species. The pot experiment was performed for 40 days. Then the wastewater samples and selected species were obtained from each pot to analyze the metal removal efficiency and assess for metal concentrations using atomic absorption spectrophotometry. The dissolved oxygen (DO; 114 mg/L), total suspended solids (TSS; 89.30 mg/L), electrical conductivity (EC; 6.35 mS/cm), chemical oxygen demand (COD) (236 mg/L), biological oxygen demand (BOD; 143 mg/L), and total dissolved solids (TDS; 559.67 mg/L), pH (6.85) were analyzed. The HMs were noted as Zn (5.73 mg/L) and Cu (7.13 mg/L). The wastewater was then treated with the species, and significant reductions were detected in physicochemical characteristics of the wastewater such as DO (13.15–62.20%), TSS (9.18–67.99%), EC (74.01–91.18%), COD (25.84–73.30%), BOD (21.67–73.42%), and TDS (14.02–95.93%). The hydrophytes and algae removed up to 82.19% of the Zn and 85.13% of the Cu from the wastewater. The study revealed that the hydrophytes and algae significantly decreased the HM levels in the wastewater (p ≤ 0.05). The study found TL, EI, ZP, and SS as the best hyper accumulative species for Zn and Cu removal from wastewater. The HMs were removed in the order of Cu > Zn. The most efficient removal for Cu was found by Typha latifolia and Zn by Zygnema pectiantum. It was concluded that bioremediation is an environmentally friendly and cost-effective technique that can be used for the treatment of wastewater due to the efficiency of algae and hydrophytes species in terms of HM removal. [ABSTRACT FROM AUTHOR]

Aquatic pollution is one of the main problems due to rapid development in industrialization. The remediation of industrial wastewater (IWW) by microorganisms is an environmentally friendly technique. This study was conducted to assess pollution load in IWW and to use Bacillus pakistanensis and Lysinibacillus composti individually and in a consortium for bioremediation. The IWW was obtained from Hayatabad Industrial Estate and evaluated for physicochemical parameters and metal concentration. The pH, color, electrical conductivity (EC), turbidity, temperature, sulfide, fluoride, chloride, biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), calcium hardness, magnesium hardness, and total hardness were noted as 6.82, 440 TCU, 1.195 mS/cm, 54.65 mg/L, 26.8 °C, 5.60 mg/L, 3.6 mg/L, 162 mg/L, 85.5 mg/L, 921 mg/L, 232 mg/L, 794 mg/L, 590 mg/L, 395 mg/L, and 985 mg/L, respectively. The metals such as manganese, copper, chromium, cadmium, cobalt, silver, nickel, calcium, magnesium, and lead were also analyzed as 1.23 mg/L, 0.81 mg/L, 2.12 mg/L, 0.18 mg/L, 0.151 mg/L, 0.24 mg/L, 1.12 mg/L, 0.113 mg/L, 14.5 mg/L, and 0.19 mg/L, respectively. A pot experiment was performed for two weeks to evaluate the efficiency of the selected species. The IWW and tap water (control) were treated with selected species, individually and in a consortium. After treatment, a considerable reduction was noted in the color 87.3%, EC 46.5%, turbidity 84.1%, sulfide 87.5%, fluoride 25.0%, chloride 91.3%, BOD 96.4%, COD 86.5%, TSS 90%, TDS 45.0%, Ca hardness 42.3%, Mg hardness 77.2%, and total hardness 52.2%. After the experiment, samples of water were also analyzed for metal concentrations by atomic absorption spectrophotometry. The selected species removed 99.3% of Mn, 99.6% of Cu, 97.8% of Cr, 94.4% of Cd, 46.3% of Co, 85.1% of Ag, 88.4% of Ni, 98.8% of Ca, 91.5% of Mg, and 90.5% of Pb. The t-test analysis showed that the treatment with the selected species significantly decreased the metal concentrations in the IWW (p ≤ 0.05). [ABSTRACT FROM AUTHOR]

Soil, air and water pollution have become a global problem due to unprocessed emission of toxic heavy metals into the environment. The uncontrolled increase in release of hazardous heavy metals such as arsenic into the soil and water is mainly due to the untreated industrial waste. The accumulation of heavy metals causes damage not only to soil and water flora but also have deleterious effects on human health. The conventional methods such as thermal treatment, excavation and land fill, electro-reclamation and acid leaching used for degradation were time and cost consuming with release of toxic products. In nature, there are microorganisms residing in soil, which are capable of degrading toxic metals through phytoremediation. In phytoremediation, rhizobacteria play an important role. Rhizobacteria not only prevent contaminated soil's fertility but also enhance the growth of plants by release of special plant growth hormones. Phytohormones secreted by plant growth-promoting rhizobacteria (PGPR) are major chemicals involved in metal uptake. This in situ and environment friendly method of bioremediation is cost effective and efficient. The advance techniques such as genetic engineering have been introduced to increase the spectrum and degrading capacity of rhizobacteria. [ABSTRACT FROM AUTHOR]

Contamination of soil and water with metals and metalloids is one of the most serious problems worldwide due to a lack of a healthy diet and food scarcity. Moreover, the cultivation of oilseed crops such as rapeseed (Brassica napus L.) with tannery wastewater could contain a large amount of toxic heavy metals [e.g., chromium (Cr)], which ultimately reduce its yield and directly influence oilseed quality. To overcome Cr toxicity in B. napus, a pot experiment was conducted to enhance plant growth and biomass by using newly introduced role of micronutrient-amino chelates [Zinc-lysine (Zn-lys)], which was irrigated with different levels [0% (control), 33%, 66%, and 100%] of tannery wastewater. According to the results of present findings, very high content of Cr in the wastewater directly affected plant growth and composition as well as gas exchange parameters, while boosting up the production of reactive oxygen species (ROS) and induced oxidative damage in the roots and leaves of B. napus. However, activities of antioxidants initially increased (33% of wastewater), but further addition of tannery wastewater in the soil caused a decrease in antioxidant enzymes, which also manifested by Zn content, while the conscious addition of wastewater significantly increased Cr content in the roots and shoots of B. napus. To reduce Cr toxicity in B. napus plants, exogenous supplementation of Zn-lys (10 mg/L) plays an effective role in increasing morpho-physiological attributes of B. napus and also reduces the oxidative stress in the roots and leaves of the oilseed crop (B. napus). Enhancement in different growth attributes was directly linked with increased in antioxidative enzymes while decreased uptake and accumulation of Cr content in B. napus when cultivated in wastewater with the application of Zn-lys. Zn-lys, therefore, plays a protective role in reducing the Cr toxicity of B. napus through an increase in plant growth and lowering of Cr uptake in various plant organs. However, further studies at field levels are required to explore the mechanisms of Zn–lys mediated reduction of Cr and possibly other heavy metal toxicity in plants. [ABSTRACT FROM AUTHOR]