Pb uptake, accumulation, and translocation in plants: Plant physiological, biochemical, and molecular response: A review.

Lead (Pb) is a highly toxic contaminant that is ubiquitously present in the ecosystem and poses severe environmental issues, including hazards to soil-plant systems. This review focuses on the uptake, accumulation, and translocation of Pb metallic ions and their toxicological effects on plant morpho-physiological and biochemical attributes. We highlight that the uptake of Pb metal is controlled by cation exchange capacity, pH, size of soil particles, root nature, and other physio-chemical limitations. Pb toxicity obstructs seed germination, root/shoot length, plant growth, and final crop-yield. Pb disrupts the nutrient uptake through roots, alters plasma membrane permeability, and disturbs chloroplast ultrastructure that triggers changes in respiration as well as transpiration activities, creates the reactive oxygen species (ROS), and activates some enzymatic and non-enzymatic antioxidants. Pb also impairs photosynthesis, disrupts water balance and mineral nutrients, changes hormonal status, and alters membrane structure and permeability. This review provides consolidated information concentrating on the current studies associated with Pb-induced oxidative stress and toxic conditions in various plants, highlighting the roles of different antioxidants in plants mitigating Pb-stress. Additionally, we discussed detoxification and tolerance responses in plants by regulating different gene expressions, protein, and glutathione metabolisms to resist Pb-induced phytotoxicity. Overall, various approaches to tackle Pb toxicity have been addressed; the phytoremediation techniques and biochar amendments are economical and eco-friendly remedies for improving Pb-contaminated soils.

Assessment and computational bioevaluation of heavy metals from selected cosmetic products.

Heavy metal toxicity in environment has been an increasing issue for last decades, though now the attention has diverted to presence of heavy metals in cosmetic products. The aim of this study was to determine the concentration of selected heavy metals in cosmetic products (lipsticks and foundations) using ICP-OES. Health risk assessment was done by using hazard quotient (HQ) and hazard index (HI). HQ for lipsticks was below the safe limit (HQ = < 1) while for foundations it exceeded the safe limit (HQ = >1). Mostly, mercury (Hg) and iron (Fe) were found to be exceeding the permissible limit, the allowed limits are Hg, 1 ppm; Fe, 10 ppm; Cd, 0.3 ppm; and Cr, 1 ppm. Iron was found to be highest in lipsticks (123.86 ± 1.05 ppm) as well as in foundations (34.52 ± 0.08 ppm). Health risk assessment was done by using hazard quotient (HQ) and hazard index (HI). HQ for lipsticks was below the safe limit (HQ = < 1) while for foundations it exceeded the safe limit (HQ = >1). To understand the binding pattern of heavy metals to skin targets, molecular docking studies were carried out. This revealed the potentially harmful behavior of these heavy metals on the skin. This will provide new direction for the structural changes of consistence and activity of macromolecules in our body. Research proved that prolonged use of cosmetic products containing heavy metals can be harmful and sometimes fatal to human life as these heavy metals can penetrate through the skin and target the skin enzymes, disrupting their normal function leading to various skin related issues such as dermatitis (itching, redness, burning) hence the monitoring of cosmetic products is necessary for safety of human being.

Abiogenic silicon: Interaction with potentially toxic elements and its ecological significance in soil and plant systems.

Abiogenic silicon (Si), though deemed a quasi-nutrient, remains largely inaccessible to plants due to its prevalence within mineral ores. Nevertheless, the influence of Si extends across a spectrum of pivotal plant processes. Si emerges as a versatile boon for plants, conferring a plethora of advantages. Notably, it engenders substantial enhancements in biomass, yield, and overall plant developmental attributes. Beyond these effects, Si augments the activities of vital antioxidant enzymes, encompassing glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), among others. It achieves through the augmentation of reactive oxygen species (ROS) scavenging gene expression, thus curbing the injurious impact of free radicals. In addition to its effects on plants, Si profoundly ameliorates soil health indicators. Si tangibly enhances soil vitality by elevating soil pH and fostering microbial community proliferation. Furthermore, it exerts inhibitory control over ions that could inflict harm upon delicate plant cells. During interactions within the soil matrix, Si readily forms complexes with potentially toxic metals (PTEs), encapsulating them through Si-PTEs interactions, precipitative mechanisms, and integration within colloidal Si and mineral strata. The amalgamation of Si with other soil amendments, such as biochar, nanoparticles, zeolites, and composts, extends its capacity to thwart PTEs. This synergistic approach enhances soil organic matter content and bolsters overall soil quality parameters. The utilization of Si-based fertilizers and nanomaterials holds promise for further increasing food production and fortifying global food security. Besides, gaps in our scientific discourse persist concerning Si speciation and fractionation within soils, as well as its intricate interplay with PTEs. Nonetheless, future investigations must delve into the precise functions of abiogenic Si within the physiological and biochemical realms of both soil and plants, especially at the critical juncture of the soil-plant interface. This review seeks to comprehensively address the multifaceted roles of Si in plant and soil systems during interactions with PTEs.

Improved Calculations of Heavy Metal Toxicity Coefficients for Evaluating Potential Ecological Risk in Sediments Based on Seven Major Chinese Water Systems.

Several methods have been used to assess heavy metal contamination in sediments. However, an assessment that considers both composite heavy metal speciation and concentration is necessary to accurately study ecological risks. This study improved the potential ecological risk index method and calculated the toxicity coefficients of seven heavy metals: Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), and Zinc (Zn). The newly calculated toxicity coefficients were validated by using previously published heavy metal distribution data of the Henan section of the Yellow River. The calculation procedure is based on the principle that the abundance of heavy metals in the environment and their bioavailable forms affect the toxicity of heavy metals. The toxicity coefficients for the seven heavy metals were calculated as follows: As = 10, Cd = 20, Cr = 5, Cu = 2, Ni = 5, Pb = 5, Zn = 1. Ecological risk assessment of the Henan section of the Yellow River using the improved toxicity coefficients revealed that the ecological risk of Cd and total heavy metals is higher than previous calculations, reaching the strength and moderate risk levels, respectively. The improved potential ecological risk index method is more sensitive to heavy metal pollution and thus provides a better indication of ecological risk. This is a necessary improvement to provide more accurate pollution assessments.

Relationship between reactive group chemistry and printing properties of heterofunctional reactive dyes via screen printing.

Screen printing of cotton fabric using newly synthesized azo reactive dyes was carried out in the present study. Functional group chemistry and its effect on the printing properties of cotton fabric by varying the nature, number and position of reactive groups of synthesized azo reactive dyes (D1-D6) was studied. Different printing parameters (Temperature, alkali and urea) and their effect was explored on the physicochemical printing properties e.g., fixation, color yield, and penetration of the dyed cotton fabric. Data revealed that dyes with more reactive groups and having linear and planar structures (D-6) showed enhanced printing properties. Spectraflash spectrophotometer was used to evaluate the colorimetric properties of screen-printed cotton fabric and results showed superb color buildup. Printed cotton samples displayed excellent to very good ultraviolet protection factor (UPF). Presence of sulphonate groups and excellent fastness properties may entitle these reactive dyes as commercially viable for urea free printing of cotton fabric.

Aluminum phytotoxicity induced structural and ultrastructural changes in submerged plant Vallisneria natans.

Aluminum (Al) is a concentration-dependent toxic metal found in the crust of earth that has no recognized biological use. Nonetheless, the mechanism of Al toxicity to submerged plants remains obscure, especially from a cell/subcellular structure and functional group perspective. Therefore, multiple dosages of Al3+ (0, 0.3, 0.6, 1.2, and 1.5 mg/L) were applied hydroponically to the submerged plant Vallisneria natans in order to determine the accumulation potential of Al at the subcellular level and their ultrastructural toxicity. More severe structural and ultrastructural damage was determined when V. natans exposed to ≥ 0.6 mg/L Al3+. In 1.2 and 1.5 mg/L Al3+ treatment groups, the total chlorophyll content of leaves significantly reduced 3.342, 3.838 mg/g FW, some leaves even exhibited chlorosis and fragility. Under 0.3 mg/L Al3+ exposure, the middle-age and young leaves were potent phytoexcluders, whereas at 1.5 mg/L Al3+, a large amount of Al could be transferred from the roots to other parts, among which the aged leaves were the most receptive tissues (7.306 mg/g). Scanning/Transmission electron microscopy analysis displayed the Al-mediated disruption of vascular bundle structure in leaf cells, intercellular space and several vegetative tissues, and demonstrated that Al in vacuole and chloroplast subcellular segregation into electron dense deposition. Al and P accumulation in the roots, stolons and leaves varied significantly among treatments and different tissues (P < 0.05). Fourier transform infrared spectroscopy of plant biomass also indicated possible metabolites (amine, unsaturated hydrocarbon, etc.) of V. natans that may bind Al3+. Conclusively, results revealed that Al3+ disrupts the cellular structure of leaves and roots or binds to functional groups of biological tissues, thereby affecting plant nutrient uptake and photosynthesis. Findings might have scientific and practical significance for the restoration of submerged vegetation in Al-contaminated lakes.

Cow bone-derived biochar enhances microbial biomass and alters bacterial community composition and diversity in a smelter contaminated soil.

Bone waste could be utilized as a potential amendment for remediation of smelter-contaminated soils. Nevertheless, the influences of cow bone-derived biochar (CB) on soil microbial biomass and microbial community composition in multi-metal contaminated mining soils are still not clearly documented. Hence, the cow bone was used as feedstock material for biochar preparation and pyrolyzed at two temperatures such as 500 °C (CB500) and 800 °C (CB800), and added to a smelter soil at the dosage of 0 (unamended control), 2.5, 5, and 10% (w/w); then, the soil treatments were cultivated by maize. The CB effect on soil biochemical attributes and response of soil microbial biomass, bacterial communities, and diversity indices were examined after harvesting maize. Addition of CB enhanced total nutrient contents (i.e., total nitrogen up to 26% and total phosphorus P up to 27%) and the nutrients availability (i.e., NH4 up to 50%; NO3 up to 31%; Olsen P up to 48%; extractable K up to 18%; dissolved organic carbon up to 74%) in the treated soil, as compared to the control. The CB500 application revealed higher microbial biomass C (up to 66%), P (up to 41%), and bacterial gene abundance (up to 76%) than the control. However, comparatively a lower microbial biomass nitrogen and diversity indices were observed in the biochar (both with CB500 and CB800) treated soils than in the unamended soils. At the phylum level, the highest dose (10% of CB500 and CB800 resulted in contrasting effects on the Proteobacteria diversity. The CB50010 favored the Pseudomonas abundance (up to 793%), Saccharibacteria (583%), Parcubacteria (138%), Actinobacteria (65%), and Firmicutes (48%) microbial communities, while CB80010 favored the Saccharibacteria (386%), Proteobacteria (12%) and Acidobacteria (11%), as compared to the control. These results imply that CB500 and CB800 have a remarkable impact on microbial biomass and bacterial diversity in smelter contaminated soils. Particularly, CB500 was found to be suitable for enhancing microbial biomass, bacterial growth of specific phylum, and diversity, which can be useful for bioremediation of mining soils.

Multi-omics provide mechanistic insight into the Pb-induced changes in tadpole fitness-related traits and environmental water quality.

Water pollution from lead/Pb2+ poses a significant threat to aquatic ecosystems, and its repercussions on aquatic animals have received considerable attention. Although Pb2+ has been found to affect numerous aspects of animals, including individual fitness, metabolic status, and symbiotic microbiota, few studies have focused on the associations between Pb2+-induced variations in fitness, metabolome, symbiotic microbiome, and environmental parameters in the same system, limiting a comprehensive understanding of ecotoxicological mechanisms from a holistic perspective. Moreover, most ecotoxicological studies neglected the potential contributions of anions to the consequences generated by inorganic lead compounds. We investigated the effects of Pb(NO3)2 at environmentally relevant concentrations on the Rana omeimontis tadpoles and the water quality around them, using blank and NaNO3-treated groups as control. Results showed that Pb(NO3)2 not only induced a rise in water nitrite level, but exposure to this chemical also impaired tadpole fitness-related traits (e.g., growth and development). The impacts on tadpoles were most likely a combination of Pb2+ and NO3-. Tissue metabolomics revealed that Pb(NO3)2 exposure influenced animal substrate (i.e., carbohydrate, lipid, and amino acid) and prostaglandin metabolism. Pb(NO3)2 produced profound shifts in gut microbiota, with increased Proteobacteria impairing Firmicutes, resulting in higher aerobic and possibly pathogenic bacteria. NaNO3 also influenced tadpole metabolome and gut microbiome, in a manner different to that of Pb(NO3)2. The presence of NO3- seemed to counteract some changes caused by Pb2+, particularly on the microbiota. Piecewise structural equation model and correlation analyses demonstrated connections between tissue metabolome and gut microbiome, and the variations in tadpole phenotypic traits and water quality were linked to changes in tissue metabolome and gut microbiome. These findings emphasized the important roles of gut microbiome in mediating the effects of toxin on aquatic ecosystem. Moreover, it is suggested to consider the influences of anions in the risk assessment of heavy metal pollutions.

Evaluation of heavy metal phytoremediation potential of six tree species of Faisalabad city of Pakistan during summer and winter seasons.

Environmental pollution induced by heavy metals has been identified as a leading threat in the modern era. Woody tree species may play a crucial role in the removal of heavy metals from soil and air, thus minimizing pollution potential. The present study was designed to evaluate the phytoremediation potential of six tree species; Azadirachta indica, Cassia fistula, Conocarpus erectus, Eucalyptus camaldulensis, Morus alba, and Populus deltoids, respectively, in the industrial and residential areas of Faisalabad based on the concentrations of lead (Pb), zinc (Zn), cadmium (Cd), and copper (Cu) in their leaves and barks in winter (2018) and summer (2019) seasons. The seasonal contents of heavy metals in both the leaves and barks of these trees decreased in the order of: Zn > Pb > Cu > Cd at both study sites. The highest heavy metal contents were recorded in the leaves and barks of trees grown in the industrial areas as compared to residential areas, with leaves and barks having higher contents of heavy metals in the summer than winter. The tree species exhibited significantly different capacity for heavy metal accumulation, with the accumulation of Cd decreased in the order of: E. camaldulensis > M. alba > C. erectus > A. indica > P. deltoids > C. fistula, and while the order varied for different heavy metals. Overall, M. alba, E. camaldulensis and A. indica performed well in accumulating the targeted heavy metals from the ambient environment. Among the six tree species grown commonly in Faisalabad city, M. alba, E. camaldulensis, and A. indica are recommended for the industrial and residential areas due to their phytoremediation capacity for heavy metals.

Iron Oxide and Silicon Nanoparticles Modulate Mineral Nutrient Homeostasis and Metabolism in Cadmium-Stressed Phaseolus vulgaris.

The application of nanoparticles (NPs) has been proved as an efficient and promising technique for mitigating a wide range of stressors in plants. The present study elucidates the synergistic effect of iron oxide nanoparticles (IONPs) and silicon nanoparticles (SiNPs) in the attenuation of Cd toxicity in Phaseolus vulgaris. Seeds of P. vulgaris were treated with IONPs (10 mg/L) and SiNPs (20 mg/L). Seedlings of uniform size were transplanted to pots for 40 days. The results demonstrated that nanoparticles (NPs) enhanced growth, net photosynthetic rate, and gas exchange attributes in P. vulgaris plants grown in Cd-contaminated soil. Synergistic application of IONPs and SiNPs raised not only K+ content, but also biosynthesis of polyamines (PAs), which alleviated Cd stress in P. vulgaris seedlings. Additionally, NPs decreased malondialdehyde (MDA) content and electrolyte leakage (EL) in P. vulgaris plants exposed to Cd stress. These findings suggest that stress alleviation was mainly attributed to the enhanced accumulation of K+ content, improved antioxidant defense system, and higher spermidine (Spd) and putrescine (Put) levels. It is suggested that various forms of NPs can be applied synergistically to minimize heavy metal stress, thus increasing crop production under stressed conditions.

Spermine-mediated polyamine metabolism enhances arsenic-stress tolerance in Phaseolus vulgaris by expression of zinc-finger proteins related genes and modulation of mineral nutrient homeostasis and antioxidative system.

The contamination of groundwater and agricultural land by metalloids especially arsenic (As) is one of the most serious threats to people and plants worldwide. Therefore, the present study was design to explore the role of spermine (Spm)- mediated polyamine metabolism in the alleviation of arsenic (As) toxicity in common bean (Phaseolus vulgaris L.). It was noted that As stress caused reduction in the intracellular CO2 concentration, stomatal conductivity and transpiration rate as compared to the control treatment and also impairedplant growth attributes and mineral nutrient homeostasis (sulfur, phosphorus, potassium and calcium). However, the exogenous application of Spm resulted in a considerable enhance in the content of glutathione and nitric oxide, and the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione-reductase (GR), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) in P. vulgaris seedlings grown As-contaminated soil. In addition, Spm application significantly improved the endogenous production of putrescine and spermidine accompanied along with reduction in malondialdehyde, electrolyte leakage, hydrogen peroxide, superoxide level besides enhanced methylglyoxal (MG) detoxification. Moreover, Spm treatment elevated the expression level of zinc-finger proteins related genes (PvC3H24, PvC3H25, PvC3H26 and PvC3H27) involved in abiotic stress response. The study concluded that Spm acted as an enhancing agent and improved tolerance to As-toxicity by upregulating the expression of zinc-finger proteins related genes, polyamine metabolism, Mg detoxification and antioxidant system in P. vulgaris.

Phyto-mediated photocatalysis: a critical review of in-depth base to reactive radical generation for erythromycin degradation.

Erythromycin (ERY), designated as a risk-prioritized macrolide antibiotic on the 2015 European Union watch list, is the third most commonly used antibiotic, most likely due to its ability to inhibit the protein. ERY has revealed record-high aquatic concentrations threatening the entire ecosystem and hence demands priority remedial measures. The inefficiency of various conventional ERY degradation methodologies opened up a gateway to advanced technologies. The conventional approach comprising of a chemically formulated, single photocatalyst has a major drawback of creating multiple environmental stresses. In this context, photocatalysis is grabbing tremendous attention as an efficient and cost-effective antibiotic treatment approach. Several studies have ascertained that ZnO, TiO2, Fe3O4, and rGO nanoparticles possess remarkable pollution minimizing operational capabilities. Additionally, composites are found much more effective in antibiotic removal than single nanoparticles. In this review, an attempt has been made to provide a comprehensive baseline for efficient reactive radical production by a phyto-mediated composite kept under a certain source of irradiation. Considerable efforts have been directed towards the in-depth investigation of rGO-embedded, phyto-mediated ZnO/TiO2/Fe3O4 photocatalyst fabrication for efficient ERY degradation, undergoing green photocatalysis. This detailed review provides photocatalytic nanocomposite individualities along with a hypothetical ERY degradation mechanism. It is assumed that derived information presented here will provoke innovative ideas for water purification incorporating green photocatalysis, initiating the construction of high-performance biogenic hierarchical nanocatalysts.

Role of magnesium oxide nanoparticles in the mitigation of lead-induced stress in Daucus carota: modulation in polyamines and antioxidant enzymes.

During the current study, the effects of magnesium oxide nanoparticles (5 mmol/L) were observed on the growth and mineral nutrients of Daucus carota under lead (Pb) stress. The results demonstrated that Pb stress decreased the growth and photosynthetic rate of D. carota plants. Furthermore, Pb stressed plants showed decreased uptake of mineral nutrients including Zn, Na, Fe, K, Ca, Mg, K, and Cu. Similarly, Pb stressed plants showed enhanced electrolyte leakage (EL) and malondialdehyde (MDA) content. However, magnesium oxide nanoparticles detoxified ROS to mitigate Pb stress and improved the growth of plants. Magnesium oxide nanoparticles also escalated the activity of antioxidant enzymes including superoxide dismutase (SOD) and Catalase (CAT). A higher amount of Pb content was observed in the roots as compared to the shoot of plants. Lead toxicity reduced manganese accumulation in D. carota plants. The increased concentration of iron, manganese, copper, and zinc advocates stress the ameliorative role of Pb stress in plants. Novelty statementThe role of MgONPs in the alleviation of Pb-toxicity in Daucus carota has never been exploited. In addition, the potential of MgONPs to enhance nutritional content in D. carota via modulation in antioxidant system and polyamines have never been reported.

Effects and mechanisms of land-types conversion on greenhouse gas emissions in the Yellow River floodplain wetland.

The mechanism and extent of changes in greenhouse gas (GHG) emissions from seasonal river-floodplain wetlands subjected to land-type conversion are unknown. We monitored GHG fluxes and characterized soil microbial communities in four types of wetland (Riverside lower-beach wetland (RLW), Riverside higher-beach wetland (RHW), Cultivated wetland (CW), Mesophytic wetland (MW)) in the Yellow River flood land. Results revealed that land reclamation activities altered the distribution patterns of carbon (C) and nitrogen (N) in soil, as well as the structure and activities of microbial communities, leading to changes in the GHG emissions. Cumulative CO2 and N2O emissions were highest in CW, which were 2.10-10.71 times and 3.19-8.61 times greater than the other three wetlands, respectively, whereas cumulative CH4 emissions were highest in RLW (1850.192 mg·m-2). CW exhibited the highest 100-years-scale Global Warming Potential (GWP100-CO2-eq) (81.175 t CO2-eq·ha-1), which was 9.93, 3.12, and 2.11 times greater than RLW, RHW, and MW. Moreover, reclaiming riverside wetland as farmland will increase CO2 and N2O emission fluxes by 54.546-72.684 t·ha-1 and 2.615-2.988 kg·ha-1, respectively. 16S rRNA high throughput sequencing revealed that bacterial community composition changed significantly overtime and seasons. GHG fluxes showed a significant positive linear correlation with bacterial OTUs (y = 0.71x-319.4, R2 = 0.304) and Shannon index (y = 228.62x-796.6, R2 = 0.336). Structure equation models indicated that soil C, N and moisture content were the primary factors influencing bacterial community evolution, which had an impact on GHG fluxes. Actinomycetes were significantly affected by total carbon (TC) content, dissolved organic carbon (DOC), and C/N, while ammonia oxidizing and nitrifying bacteria were greatly influenced by NO3--N rather than TN and NH4+-N content. Opportunities exist to reduce GHG emissions and mitigate climate change by maintaining the original state of riverside wetland or restoring cultivated land to wetland in the Yellow River floodplain wetland.

Distribution of antibiotic resistance genes from human and animal origins to their receiving environments: A regional scale survey of urban settings.

Antibiotic resistance is a growing problem for ecosystem health and public healthcare. Hence, the transmission of antibiotic resistance from human and animal origins to natural environments requires careful investigation. In this study, nine antibiotic resistance genes (ARGs), three mobile genetic elements (MGEs), and their relations with antibiotics, heavy metals, and microbiota were investigated in 16 sample sites (Xinxiang, China). Fluoroquinolones (0.13-14.22 µg/L) were most abundant in hospital effluent and oxytetracycline (251.86-5817.47 µg/kg) in animal manure. Animal manure showed the highest levels of zinc (80.79-2597.14 mg/kg) and copper (32.47-85.22 mg/kg), possibly affecting the prevalence of intI1 and aac(6')-Ib genes. Aminoglycoside and sulfonamide resistance genes (aac(6')-Ib, aadA, and sul1) were the main ARGs in this area. In addition, the detected ARGs and MGEs were higher in animal manure than in hospital effluent, except for the sul1 gene. On the other hand, the incomplete removal of antibiotics (29.76-100%), heavy metals (31.25-100%), and ARGs (1-3 orders of magnitude) in MWWTPs resulted in the accumulation of these contaminants in the receiving river. Network analysis suggested that the potential hosts (Jeotgalibaca, Atopostipes, Corynebacterium_1, etc.) of ARGs were more predominant in animal manure rather than hospital effluent, indicating a higher ARG transfer potential in animal manure compared with hospital sources. These results provide useful insights into the different migration and dissemination routes of antibiotics, heavy metals, ARGs, and microbiota from anthropogenic and animal origins to their receiving environments via MWWTP discharge and manure fertilization.

The interactive effect of pH variation and cadmium stress on wheat (Triticum aestivum L.) growth, physiological and biochemical parameters.

Anthropogenic activities such as mining, manufacturing, and application of fertilizers release substantial quantities of cadmium (Cd) into the environment. In the natural environment, varying pH may play an important role in the absorption and accumulation of Cd in plants, which can cause toxicity and increase the risk to humans. We conducted a hydroponic experiment to examine the impact of pH on cadmium (Cd) solubility and bioavailability in winter wheat (Triticum aestivum L.) under controlled environmental conditions. The results showed that Cd concentration was significantly reduced in wheat with an increase in pH from 5 to 7, while it was dramatically increased at pH ranging from 7 to 9. However, in both cases, a significant reduction in physiological traits was observed. The addition of Cd (20, 50, and 200 µmol L-1) at all pH levels caused a substantial decline in wheat growth, chlorophyll and carotenoids contents, nutrient availability, while elevated cell membrane damage was observed in terms of electrolytic leakage (EL), osmoprotectants, and antioxidants activity. In our findings, the negative effects of acidic pH (5) on wheat growth and development were more pronounced in the presence of Cd toxicities. For instance, Cd concentration with 20, 50, and 200 µmol L-1 at acidic pH (5) reduced shoot dry biomass by 45%, 53%, and 79%, total chlorophyll contents by 26%, 41%, 56% while increased CAT activity in shoot by 109%, 175%, and 221%, SOD activity in shoot by 122%, 135%, and 167%, POD activity in shoot by 137%, 250%, and 265%, MDA contents in shoot by 51%, 83%, and 150%, H2O2 contents in shoot by 175%, 219%, and 292%, EL in shoot by 108%, 165%, and 230%, proline contents in shoot by 235%, 280%, and 393%, respectively as compared to neutral pH without Cd toxicities. On the other hand, neutral pH with Cd toxicities alleviated the negative effects of Cd toxicity on wheat plants by limiting Cd uptake, reduced reactive oxygen species (ROS) formation, and increased nutrient availability. In conclusion, neutral pH minimized the adverse effects of Cd stress by minimizing its uptake and accumulation in wheat plants.

Silicon elevated cadmium tolerance in wheat (Triticum aestivum L.) by endorsing nutrients uptake and antioxidative defense mechanisms in the leaves.

Numerous abiotic stressors including heavy metal stresses, specifically cadmium (Cd) stress in agricultural bio-system hinder the plant adequate growth. The present study was aimed to reveal the protective role of silicon (Si) application with two levels and to recognize the optimum level of Si for wheat plants grown hydroponically under three different levels of Cd toxicities. In methodology, we used nine treatments with three levels of Si (0, 1, and 3 mmol L-1; Na2SiO3) against three levels of Cd (0, 50, 200 µmol L-1; CdCl2) with three biological replicates. The results of our study demonstrated that Si incorporation with the advantage of 3 mmol L-1 in cultured media with Cd50 and Cd200 demolished the toxic effects of Cd on the leaves of wheat plants by increasing plant dry biomass by 88% and 262%, leaf area by 48% and 57%, total chlorophyll contents by 120% and 74%, catalase (CAT) activity by 92% and 110%, superoxide dismutase (SOD) activity by 62% and 78%, peroxidase (POD) activity by 66% and 40%, ascorbic acid (AsA) contents by 33% and 34%, glutathione (GHS) contents by 39% and 30% and reduced MDA contents by 56% and 50%, H2O2 contents by 61% and 66%, and EL contents by 56% and 47% as parallel to Cd corresponding levels. In addition, Si incorporation with the advantage of 3 mmol L-1 significantly increased relative water contents (RWC) to maintain the cell turgor pressure and protect the plant from wilting and cells flaccid and enhanced membrane stability index (MSI) to protect the plant from logging under damaging effects of Cd toxicities. Based on the present findings, Si can be considered a quasi-essential element that enhanced wheat tolerance against Cd toxicity by limiting uptake, accumulation, and translocation of Cd and through regulating antioxidative defense mechanisms.

Hexachlorocyclohexane toxicity in water bodies of Pakistan: challenges and possible reclamation technologies.

Pakistan is an agro-economy country where hexachlorocyclohexane (HCH) pesticides are being used to improve crop productivity, as a result the risk of contamination of soil and sediment has been increased. HCH exhibits all the characteristics of persistent organic pollutants (POP), and was therefore added to the list of 'new POPs' in 2009. This review report revealed that the major rivers of Pakistan such as the Indus Basin, River Ravi, River Chenab and their tributaries all are contaminated with HCH and the highest residual concentration (4,090 ng/g) was detected in a pesticide burial ground in Hyderabad city. Major sources of HCH contamination were identified as agricultural runoff, discharge of untreated industrial effluents and surface runoff. In order to manage HCH pollution, various ex-situ and in-situ remediation techniques along with their merits and demerits are thoroughly reviewed. Among these, microbial bioremediation is a low cost, environment friendly, effective in-situ remediation technique for remediation of HCH. Overall, the information provided in this manuscript will provide a future reference to the scientific community and bridge the knowledge gap between HCH release in the environment and their mitigation through proper treatment methods.

Biotreatment potential of co-contaminants hexavalent chromium and polychlorinated biphenyls in industrial wastewater: Individual and simultaneous prospects.

Co-existence of polychlorinated biphenyls (PCBs) and hexavalent chromium (Cr(VI)) in the environment due to effluent from industries has aggravated the pollution problem. Both contaminants can alter chemical interactions, processes and impair enzymatic activities in the ecosystem that results in negative impacts on aquatic and terrestrial life. Previously, research has been performed for the fate and transfer of these contaminants individually, but simultaneous removal approaches have not received much attention. Cr(VI) exists in a highly toxic form in the environment once released, whereas location of chlorine atoms in the ring determines PCBs toxicity. Lower chlorinated compounds are easily degradable whereas as high chlorinated compounds require sequential strategy for transformation. Microorganisms can develop different mechanism to detoxify both pollutants. However, occurrence of multiple contaminants in single system can alter the bioremediation efficiency of bacteria. Use of metal resistance bacterial for the degradation of organic compounds has been widely used bioaugmentation strategy. Along with that use of sorbents/bio sorbents, biosurfactants and phytoremediation approaches have already been well reported. Bioremediation strategy with dual potential to detoxify the Cr(VI) and PCBs would be a probable option for simultaneous biotreatment. Application of bioreactors and biofilms covered organic particles can be utilized as efficient bioaugmentation approach. In this review, biotreatment systems and bacterial oxidative and reductive enzymes/processes are explained and possible biotransformation pathway has been purposed for bioremediation of co-contaminated waters.

Resistance of multidrug resistant Escherichia coli to environmental nanoscale TiO2 and ZnO.

Excessive production and utilization of nanoparticles (NPs) at industrial and household levels releases substantial quantities of NPs into the environment. These can be harmful to different types of organisms and cause adverse effects on ecosystems. Purchased TiO2 and ZnO NPs were characterized via XRD, XPS, FESEM, and Zeta potential. This study elucidates how multidrug resistant Escherichia coli LM13, which was recovered from livestock manure, counteracts the antibacterial activities of TiO2 and ZnO NPs to survive in the environment. E. coli ATCC25922, which is susceptible to antibiotics, was used as control. A dose-response experiment showed that the antibacterial activity of TiO2 was lower than that of ZnO NPs and, LM13 was more resistant to NPs than ATCC25922. An AcrAB-TolC efflux pump along with its regulation genes helped LM13 to minimize NP toxicity. Flow cytometry findings also indicated that the intensity of the side-scatter light parameter increased with TiO2 and ZnO NPs in a dose dependent manner, suggesting NP uptake by the both strains. The generation of reactive oxygen species in LM13 was several-fold lower than in ATCC25922, suggesting that reactive oxygen species mainly contribute to the toxicity mechanism. These results illustrate the necessity to evaluate the impacts of NPs on the survival capacity of bacteria and on the resistance genes in bacteria with higher NP resistance than NP susceptible bacteria.