Impact of Brain derived Neurotrophic factor gene polymorphism on its peripheral levels in schizophrenic patients.

Objectives: To determine serum levels of brain-derived neurotrophic factor and its polymorphism rs12291063 in schizophrenic patients. METHODS: The case-control study was conducted from January1, 2020, to May 15, 2021, at Dr Abdul Qadeer Khan Institute of Behavioural Sciences, Dow University of Health Sciences, Karachi, and comprised schizophrenia cases aged 14-60 years who were diagnosed using Diagnostic and Statistical Manual of Mental Disorders-V criteria, and healthy controls without any psychiatric illness. Positive and negative syndrome scale score was used to assess disease severity. The genomic deoxyribonucleic acid of the subjects was isolated from peripheral blood, followed by polymerase chain reaction, gel electrophoresis and sequencing of the amplicons. The sequences were analysed using MEGA X software for genotyping. Serum brain-derived neurotrophic factor levels were assessed using enzyme-linked immunosorbent assay. Data was analysed using SPSS 21. RESULTS: Of the 100 subjects, 50(50%) were cases; 36(72%) males and 14(28%) females (p<0.05) with mean age 34.34±10.32 years. There were 50(50%) controls; 32(64%) males and 18(36%) females (p=0.391) with mean age 30.886±8.88 years. Among the cases, the mean age at schizophrenia diagnosis was 25.14±9.54 years, and there was a significant association with positive family history for psychiatric disorders (p<0.05). Sequencing revealed no T>C substitution. Serum brain-derived neurotrophic factor levels were significantly higher in cases compared to controls (p<0.001). There was a weak negative correlation between brain-derived neurotrophic factor levels and positive and negative syndrome scale score (p<0.05). CONCLUSIONS: Higher brain-derived neurotrophic factor levels were found to be associated with schizophrenia, while no association of rs12291063 T>C was found with schizophrenia.

Role of organic and inorganic amendments on physiological attributes of germinating pea seedlings under arsenic stress.

There are scarce data regarding the effects of soil amendments on biophysicochemical responses of plants at the early stages of growth/germination. This study critically compares the effects of ethylene-diamine-tetra-acetic-acid (EDTA) and calcium (Ca) on biophysicochemical responses of germinating pea seedlings under varied arsenic levels (As, 25, 125, 250 µM). Arsenic alone enhanced hydrogen peroxide (H2O2) level in pea roots (176%) and shoot (89%), which significantly reduced seed germination percentage, pigment contents, and growth parameters. Presence of EDTA and Ca in growth culture minimized the toxic effects of As on pea seedlings, EDTA being more pertinent than Ca. Both the amendments decreased H2O2 levels in pea tissues (16% in shoot and 13% in roots by EDTA, and 7% by Ca in shoot), and maintained seed germination, pigment contents, and growth parameters of peas close to those of the control treatment. The effects of all As-treatments were more pronounced in the pea roots than in the shoot. The presence of organic and inorganic amendments can play a useful role in alleviating As toxicity at the early stages of pea growth. The scarcity of data demands comparing plant biophysicochemical responses at different stages of plant growth (germinating vs mature) in future studies.

Till date, abundant research has focused on plant biophysicochemical responses to different types of pollutants. However, the majority of these studies dealt with pollutant exposure to mature plants (generally after a vegetative growth period of 1­2 weeks). Despite significant research, there are still limited data regarding the biophysicochemical responses of plants at their early stages of germination and growth. In fact, stresses at germination or at an early stage of growth can be highly fatal and may significantly affect the ultimate plant growth and potential to remediate the contaminated sites. Therefore, the current study deals with the exposure of germinating pea seedlings to arsenic (As) stress under varied amendments. This experimental plan helped to understand the initial biophysicochemical changes induced in pea plants under As stress.

The evaluation of bacterial-augmented floating treatment wetlands for concomitant removal of phenol and chromium from contaminated water.

Contamination of aquatic ecosystems with organic and inorganic contaminants is a global threat due to their hazardous effects on the environment and human health. Floating treatment wetland (FTW) technology is a cost-effective and sustainable alternative to existing treatment approaches. It consists of a buoyant mat in which wetland plants can grow and develop their roots in a suspended manner and can be implemented to treat stormwater, municipal wastewater, and industrial effluents. Here we explored the potential of bacterial-augmented FTWs for the concurrent remediation of phenol and hexavalent chromium (Cr6+) contaminated water and evaluated treated water toxicity using Triticum aestivum L. (wheat) as a test plant. The FTWs carrying Phragmites australis L. (common reed) were inoculated with a consortium of four bacterial strains (Burkholderia phytofirmans PsJN, Acinetobacter lwofii ACRH76, Pseudomonas aeruginosa PJRS20, Bacillus sp. PJRS25) and evaluated for their potential to simultaneously remove phenol and chromium (Cr) from contaminated water. Results revealed that the FTWs efficiently improved water quality by removing phenol (86%) and Cr (80%), with combined use of P. australis and bacterial consortium after 50 days. The phytotoxicity assay demonstrated that the germination of wheat seed (96%) was significantly higher where bacterial-augmented FTWs treated water was used compared to untreated water. This pilot-scale study highlights that the combined application of wetland plants and bacterial consortium in FTWs is a promising approach for concomitant abatement of phenol and Cr from contaminated water, especially for developing countries like Pakistan where the application of advanced and expensive technologies is limited.

This pilot-scale research provides new interventions and information required for establishing a large-scale remediation framework for the effective, sustainable and eco-friendly remediation of phenol and Cr co-contaminated aquatic ecosystems, using bacterial augmented floating wetlands technology (FTWs).

A critical review on the separation of heavy metal(loid)s from the contaminated water using various agricultural wastes.

Wastewater contamination with heavy metal(loids)s has become a worldwide environmental and public health problem due to their toxic and non-degradable nature. Different methods and technologies have been applied for water/wastewater treatment to mitigate heavy metal(loid)-induced toxicity threat to humans. Among various treatment methods, adsorption is considered the most attractive method because of its high ability and efficiency to remove contaminants from wastewater. Agricultural waste-based adsorbents have gained great attention because of high efficiency to heavy metal(loids)s removal from contaminated water. Chemically modified biosorbents can significantly enhance the stability and adsorption ability of the sorbents. The two mathematical models of sorption, Freundlich and Langmuir isotherm models, have mostly been studied. In kinetic modeling, pseudo-second-order model proved better in most of the studies compared to pseudo-first-order model. The ion exchange and electrostatic attraction are the main mechanisms for adsorption of heavy metal(loid)s on biosorbents. The regeneration has allowed various biosorbents to be recycled and reused up to 4-5 time. Most effective eluents used for regeneration are dilute acids. For practical perspective, biosorbent removal efficiency has been elucidated using various types of wastewater and economic analysis studies. Economic analysis of adsorption process using agricultural waste-based biosorbents proved this approach cheaper compared to traditional commercial adsorbents, such as chemically activated carbon. The review also highlights key research gaps to advance the scope and application of waste peels for the remediation of heavy metal(loid)s-contaminated wastewater.

This review provides new information and insights on the potential utilization of agriculture-based biosorbents for the removal of contaminants, especially heavy metal(loid)s from toxic water/wastewater, as well as their mechanisms, adsorption efficiency, and regeneration ability. For practical perspective, biosorbent adsorption efficiency was elucidated by using various types of wastewater and economic analysis studies.

Exploring the potential of bacterial-augmented floating treatment wetlands for the remediation of detergent-contaminated water.

Due to industrialization and urbanization, the use of detergents inadvertently led to contamination of aquatic environments, thus posing potential threat to aquatic organisms and human health. One of the main components of detergents is linear alkylbenzene sulfonate (LAS), which can cause toxic effects on living organisms, particularly aquatic life in the environment. In this study, floating treatment wetlands (FTWs) mesocosms were developed and augmented with LAS-degrading bacteria. The plant species, Brachiaria mutica (Para grass), was vegetated to establish FTWs and bacterial consortium (1:1:1:1) of Pseudomonas aeruginosa strain PJRS20, Bacillus sp. BRRH60, Acinetobacter sp. strain CYRH21, and Burkholderia phytofirmans Ps.JN was augmented (free or immobilized) in these mesocosms. Results revealed that the FTWs removed LAS from the contaminated water and their augmentation with bacteria slightly increased LAS removal during course of the experiment. Maximum reduction in LAS concentration (94%), chemical oxygen demand (91%), biochemical oxygen demand (93%), and total organic carbon (91%) was observed in the contaminated water having FTWs augmented with bacterial consortium immobilized on polystyrene sheet. This study highlights that the FTWs supported with immobilized bacteria on polystyrene sheets can provide an eco-friendly and sustainable solution for the remediation of LAS-bearing water, especially for developing countries like Pakistan.

This pilot-scale study provided insights to resolve the detergent-contaminated wastewater issue, using floating treatment wetlands (FTWs) augmented with bacteria. The FTWs augmented with bacteria immobilized on a polystyrene sheet and vegetated with Brachiaria mutica led to high degradation of LAS, a toxic compound of detergent, from the contaminated water.

Unveiling the significance of foliar-applied silicon, selenium and phosphorus for the management and remediation of arsenic in two different rice genotypes.

Under paddy soil conditions, rice plants are vulnerable to arsenic (As) accumulation, thus causing potential threat to human health. Here we investigated the influence of foliar-applied phosphorus (P: 10 and 20 mg L-1), silicon (Si: 0.6 and 1.5 g L-1) and selenium (Se: 5 and 10 mg L-1) on As accumulation, morphological and physiological attributes of two contrasting rice genotypes (KSK-133 and Super Basmati) under As stress (25 mg kg-1 as arsenate). Silicon foliar dressing significantly (p < 0.05) reduced grain As uptake (up to 67%) and improved rice growth and chlorophyll content (28-66%) in both rice genotypes over their controls. Phosphorus foliar application resulted in a notable decrease (17%) in grain As uptake of coarse rice genotype (KSK-133), while it slightly increased grain As uptake in the fine one (Super Basmati; 6%) compared to controls. However, foliar-applied Se did not show significant effects on rice plants growth attributes and As uptake in both genotypes. Similarly, biochemical and enzymatic attributes (i.e., lipid peroxidation, electrolyte leakage, peroxidase and catalase) were improved with Si application in rice plants, except for P treatment that was only effective for coarse one. Foliar-applied Si also resulted in reduced cancer risk and hazard quotient (< 0.10) for both rice genotypes. This study advances our understanding on critical role of different foliar-applied nutrients and rice genotypes, which is imperative to develop effective As remediation and management strategies in coarse and fine rice genotypes and protect human health.

This study provided new insights on the significance of foliar-applied phosphorus, silicon and selenium for the management and remediation of arsenic in fine (Super Basmati) and coarse (KSK-133) rice genotypes. Foliar-applied silicon was the most promising strategy to mitigate arsenic uptake and minimizing health risk in rice grain of both genotypes, while phosphorus was effective only for coarse one, thus showing a genotype dependent response. Interestingly, selenium foliar application had no significant effect on arsenic accumulation in both rice genotypes.

Effect of freshwater and wastewater irrigation on buildup of toxic elements in soil and maize crop.

Untreated wastewater is routinely used for agricultural activities in water-stressed regions, thereby causing severe ecological risks by various pollutants. Hence, management strategies are needed to cope with the environmental issues related to wastewater use in agriculture. This pot study evaluates the effect of mixing either freshwater (FW) or groundwater (GW) with sewage water (SW) on the buildup of potentially toxic elements (PTEs) in soil and maize crop. Results revealed that SW of Vehari contains high levels of Cd (0.08 mg L-1) and Cr (2.3 mg L-1). Mixing of FW and GW with SW increased soil contents of As (22%) and decreased Cd (1%), Cu (1%), Fe (3%), Mn (9%), Ni (9%), Pb (10%), and Zn (4%) than SW "alone" treatment. Risk indices showed high-degree of soil-contamination and very-high ecological risks. Maize accumulated considerable concentrations of PTEs in roots and shoot with bioconcentration factor > 1 for Cd, Cu, and Pb and transfer factor > 1 for As, Fe, Mn, and Ni. Overall, mixed treatments increased plant contents of As (118%), Cu (7%), Mn (8%), Ni (55%), and Zn (1%), while decreased those of Cd (7%), Fe (5%), and Pb (1%) compared to SW "alone" treatments. Risk indices predicted possible carcinogenic risks to cow (CR 0.003 > 0.0001) and sheep (CR 0.0121 > 0.0001) due to consumption of maize fodder containing PTEs. Hence, to minimize possible environmental/health hazards, mixing of FW and GW with SW can be an effective strategy. However, the recommendation greatly depends on the composition of mixing waters.

The role of various ameliorants on geochemical arsenic distribution and CO2-carbon efflux under paddy soil conditions.

Climate change is a global challenge that is accelerated by contamination with hazardous substances like arsenic (As), posing threat to the agriculture, ecosystem and human health. Here, we explored the impact of various ameliorants on geochemical distribution of As in two soils with contrasting textures (sandy clay loam (Khudpur Village) and clay loam (Mattital Village)) under paddy soil conditions and their influence on the CO2-carbon efflux. The exchangeable As pool in clay loam soil increased as: lignite (0.4%) < biogas slurry (6%) < cow dung (9%), and < biochar (20%). However, in the sandy clay loam soil exchangeable soil As pool was found to be maximum with farmyard manure followed by biogas slurry, biochar and cow dung (17%, 14%, 13% and 7%, respectively). Interestingly, in the sandy clay loam soil the percentage As distribution in organic fraction was: biochar (38%) > cow dung (33%) > biogas slurry (23%) > sugarcane bagasse (22%) > farmyard manure (21%) that was higher compared to the clay loam soil (< 6% for all the amendments). In addition to the highest As immobilization by biochar in sandy clay loam soil, it also led to the lowest CO2-carbon efflux (1470 CO2-C mg kg-1) among all the organic/inorganic amendments. Overall, the current study advances our understanding on the pivotal role of organic amendments, notably biochar, in immobilizing As under paddy soil conditions with low (CO2) carbon loss, albeit it is dependent on soil and ameliorant types.

Risk assessment of trace element accumulation in soil and Brassica oleracea after wastewater irrigation.

The risk assessment of trace elements has received substantial attention for the achievement of UN Sustainable Developmental Goals (UN-SDGs). The present study aimed to evaluate health and ecological risks associated with trace element accumulation in Brassica oleracea under wastewater irrigations from three different areas. This study, for the first time, compared the pros and cons of mixed water crop irrigation (wastewater with fresh/groundwater). A pot experiment was conducted to evaluate the buildup of eight trace elements (As, Cu, Cd, Mn, Fe, Pb, Ni and Zn) in soil and B. oleracea plants irrigated with wastewater alone and mixed with fresh/groundwater. Specific ecological [degree of contamination (Cd), potential ecological risk index (PERI), pollution load index (PLI), geo-accumulation index (Igeo)], phytoaccumulation [bioconcentration factor (BCF) and transfer factor (TF)] and health risk models [chronic daily intake (CDI), hazard quotient (HQ), cancer risk (CR)] were applied to assess the overall contamination of trace elements in the soil-plant-human system. Moreover, these indices were compared with the literature data. The concentration of Cd, Fe and Mn exceeded the threshold limits of 10, 500 and 200 mg kg-1, respectively, for agricultural soil. Overall, all the irrigation waters caused significant pollution load in soil indicating high ecological risk (Cd > 24, PERI > 380, Igeo > 5, PLI > 2). Not all the mixing treatments caused a reduction in trace element buildup in soil. The mixing of wastewater-1 with either groundwater or freshwater increased trace element levels in the soil as well as risk indices compared to wastewater alone. The BCF and TF values were > 1, respectively, for 66% and 7% treatments. Trace element concentration in plants and associated health risk were minimized in mixed wastewater treatments. There were 22% and 32% reduction in HQ and CR when wastewater was mixed with freshwater and 29% and 8% when mixed with groundwater. Despite total reduction, a great variation in % change in risk indices was observed with respect to the area of wastewater collection. Therefore, mixed water irrigation may be a good management strategy, but its recommendation depends on soil properties and composition of waters used for mixing. Moreover, it is recommended that the freshwater and wastewater of the particular area may be continuously monitored to avoid potential associated health hazards.

Biochar/nano-zerovalent zinc-based materials for arsenic removal from contaminated water.

In this study, we explored the potential of a newly prepared nano-zero valent zinc (nZVZn), biochar (BC)/nZVZn and BC/hydroxyapatite-alginate (BC/HA-alginate) composites for the removal of inorganic As species from water. Relatively, higher percentage removal of As(III) and As(V) was obtained by nZVZn at pH 3.4 (96% and 94%, respectively) compared to BC/nZVZn (90% and 88%) and BC/HA-alginate (88% and 80%) at pH 7.2. Freundlich model provided the best fit (R2 = up to 0.98) for As(III) and As(V) sorption data of all the sorbents, notably for nZVZn. The pseudo-second order model well-described kinetics of As(III) and As(V) (R2 = 0.99) sorption on all the sorbents. The desorption experiments demonstrated that the As removal efficiency, up to the third sorption/desorption cycle, was in the order of nZVZn ∼ BC/HA-alginate (88%) > BC/nZVZn (84%). The Fourier transform infrared spectroscopy depicted that the -OH, -COOH, Zn-O and Zn-OH surface functional groups were responsible for the sorption of As(III) or As(V) on the sorbents investigated here. This study highlights that removal of As species from water by BC/nZVZn composite can be compared with nZVZn, suggesting that integrating BC with nZVZn could efficiently remove As from As-contaminated drinking water.

This is the first study to explore the potential of a newly prepared sugarcane bagasse biochar/nano-zerovalent zinc (BC/nZVZn) based composite for the removal of inorganic arsenic (As) species from water. The results indicated high percentage removal of As(III) and As(V) from water by BC/nZVZn that were comparable to nZVZn alone.

Biowaste-based sorbents for arsenic removal from aqueous medium and risk assessment.

Water contamination by arsenic (As) is widespread and is posing serious health threats globally. Hence, As removal techniques/adsorbents need to be explored to minimize potentials hazards of drinking As-contaminated waters. A column scale sorption experiment was performed to assess the potential of three biosorbents (tea waste, wheat straw and peanut shells) to remove As (50, 100, 200 and 400 µg L-1) from aqueous medium at a pH range of 5-8. The efficiency of agricultural biosorbents to remove As varies greatly regarding their type, initial As concentration in water and solution pH. It was observed that all of the biosorbents efficiently removed As from water samples. The maximum As removal (up to 92%) was observed for 400 µg L-1 initial As concentration. Noticeably, at high initial As concentrations (200 and 400 µg L-1), low pH (5 and 6) facilitates As removal. Among the three biosorbents, tea waste biosorbent showed substantial ability to minimize health risks by removing As (up to 92%) compared to peanut shells (89%) and wheat straw (88%). Likewise, the values of evaluated risk parameters (carcinogenic and non-carcinogenic risk) were significantly decreased (7-92%: average 66%) after biosorption experiment. The scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray and X-ray diffraction analyses confirmed the potential of biosorbents to remediate As via successful loading of As on their surfaces. Hence, it can be concluded that synthesized biosorbents exhibit efficient and ecofriendly potential for As removal from contaminated water to minimize human health risk.

Accumulation pattern and risk assessment of potentially toxic elements in selected wastewater-irrigated soils and plants in Vehari, Pakistan.

There are scarce data about the accumulation pattern and risk assessment of potentially toxic elements (PTEs) in soil and associated potential ecological risks, especially in less-developed countries. This study aims to assess the pollution levels and potential ecological risks of PTEs (As, Cr, Cd, Cu, Ni, Mn, Pb and Zn) in wastewater-irrigated arable soils and different edible-grown plants in selected areas of Vehari, Pakistan. The results revealed that the values of PTEs in soil samples were higher than their respective limit values by 20% for As, 87% for Cd, 15% for Cu, 2% for Cr, 83% for Mn, 98% for Fe, and 7% for Zn. The values of soil risk indices such as the potential ecological risk (PERI >380 for all samples), pollution load index (PLI >4 for 94% of studied samples), and degree of contamination (Dc > 24 for all samples) showed severe soil contamination in the study area. Some vegetables exhibited a high metal accumulation index (e.g., 8.1 for onion), signifying potential associated health hazards. Thus, long-term wastewater irrigation has led to severe soil contamination, which can pose potential ecological risks via PTE accumulation in crops, particularly Cd. Therefore, to ensure food safety, frequent wastewater irrigation practices need to be minimized and managed in the study area.

Distribution and ecological risk assessment of trace elements in the paddy soil-rice ecosystem of Punjab, Pakistan.

Trace elements (TEs) contamination of agricultural soils requires suitable criteria for regulating their toxicity limits in soil and food crops, which depends on their potential ecological risk spanning regional to global scales. However, no comprehensive study is available that links TE concentrations in paddy soil with ecological and human health risks in less developed regions like Pakistan. Here we evaluated the data set to establish standard guidelines for defining the hazard levels of various potentially toxic TEs (such as As, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Se, Zn) in agricultural paddy soils of Punjab, Pakistan. In total, 100 topsoils (at 0-15 cm depth) and 204 rice plant (shoot and grain) samples were collected from five ecological zones of Punjab (Gujranwala, Hafizabad, Vehari, Mailsi, and Burewala), representing the major rice growing regions in Pakistan. The degree of contamination (Cd) and potential ecological risk index (PERI) established from ecological risk models were substantially higher in 100% and 97% of samples, respectively. The positive matrix factorization (PMF) model revealed that the elevated TEs concentration, notably Cd, As, Cr, Ni, and Pb, in the agricultural paddy soil was attributed to the anthropogenic activities and groundwater irrigation. Moreover, the concentration of these TEs in rice grains was higher than the FAO/WHO's safe limits. This study provided a baseline, albeit critical knowledge, on the impact of TE-allied ecological and human health risks in the paddy soil-rice system in Pakistan; and it opens new avenues for setting TEs guidelines in agro-ecological zones globally, especially in underdeveloped regions.

The significance of eighteen rice genotypes on arsenic accumulation, physiological response and potential health risk.

Rice is an important food crop that is susceptible to arsenic (As) contamination under paddy soil conditions depending on As uptake characteristics of the rice genotypes. Here we unveiled the significance of eighteen (fine and coarse) rice genotypes against As accumulation/tolerance, morphological and physiological response, and antioxidant enzymes-enabled defense pathways. Arsenic significantly affected rice plant morphological and physiological attributes, with relatively more impacts on fine compared to coarse genotypes. Grain, shoot, and root As uptake were lower in fine genotypes (0.002, 0.020, and 0.032 mg pot-1 DW, respectively) than that of coarse (0.031, 0.60, and 1.2 mg pot-1 DW, respectively). Various biochemical (pigment contents, hydrogen peroxide, lipid peroxidation) and defense (antioxidant enzymes) plant parameters indicated that the fine genotypes, notably Kainat and Basmati-385, possessed the highest As tolerance. Arsenic-induced risk indices exhibited greater hazard quotient (up to 1.47) and carcinogenic risk (up to 0.0066) for coarse genotypes compared to the fine ones, with the greatest risk for KSK-282. This study elaborates the pivotal role of genotypic variation among rice plants in As accumulation, which is crucial for mitigating the associated human health risk. Further research is required on molecular aspects, e.g., genetic sequencing, to examine rice genotypes variation in defense mechanisms to As contamination.

Zinc in soil-plant-human system: A data-analysis review.

Zinc (Zn) plays an important role in the physiology and biochemistry of plants due to its established essentiality and toxicity for living beings at certain Zn concentration i.e., deficient or toxic over the optimum range. Being a vital cofactor of important enzymes, Zn participates in plant metabolic processes therefore, alters the biophysicochemical processes mediated by Zn-related enzymes/proteins. Excess Zn can provoke oxidative damage by enhancing the levels of reactive radicals. Hence, it is imperative to monitor Zn levels and associated biophysicochemical roles, essential or toxic, in the soil-plant interactions. This data-analysis review has critically summarized the recent literature of (i) Zn mobility/phytoavailability in soil (ii) molecular understanding of Zn phytouptake, (iii) uptake and distribution in the plants, (iv) essential roles in plants, (v) phyto-deficiency and phytotoxicity, (vi) detoxification processes to scavenge Zn phytotoxicity inside plants, and (vii) associated health hazards. The review especially compares the essential, deficient and toxic roles of Zn in biophysicochemical and detoxification processes inside the plants. To conclude, this review recommends some Zn-related research perspectives. Overall, this review reveals a thorough representation of Zn bio-geo-physicochemical interactions in soil-plant system using recent data.

Constructed wetlands as a sustainable technology for wastewater treatment with emphasis on chromium-rich tannery wastewater.

Water scarcity is a major threat to agriculture and humans due to over abstraction of groundwater, rapid urbanization and improper use in industrial processes. Industrial consumption of water is lower than the abstraction rate, which ultimately produces large amounts of wastewater such as from tannery industry containing high concentration of chromium (Cr). Chromium-contaminated tannery industry wastewater is used for irrigation of food crops, resulting in food safety and public health issues globally. In contrast to conventional treatment technologies, constructed wetlands (CWs) are considered as an eco-friendly technique to treat various types of wastewaters, although their application and potential have not been discussed and elaborated for Cr treatment of tannery wastewater. This review briefly describes Cr occurrence, distribution and speciation in aquatic ecosystems. The significance of wetland plant species, microorganisms, various bedding media and adsorbents have been discussed with a particular emphasis on the removal and detoxification of Cr in CWs. Also, the efficiency of various types of CWs is elaborated for advancing our understanding on Cr removal efficiency and Cr partitioning in various compartments of the CWs. The review covers important aspects to use CWs for treatment of Cr-rich tannery wastewater that are key to meet UN's Sustainable Development Goals.

Arsenic-induced oxidative stress in Brassica oleracea: Multivariate and literature data analyses of physiological parameters, applied levels and plant organ type.

Plant redox homeostasis governs the uptake, toxicity and tolerance mechanism of toxic trace elements and thereby elucidates the remediation potential of a plant. Moreover, plant toxicity/tolerance mechanisms control the trace element compartmentation in edible and non-edible plant organs as well as the associated health hazards. Therefore, it is imperative to unravel the cellular mechanism involved in trace element toxicity and tolerance. The present study investigated the toxicity and tolerance/detoxification mechanisms of four levels of arsenic (As(III): 0, 5, 25 and 125 µM) in Brassica oleracea under hydroponic cultivation. Increasing As levels significantly decreased the pigment contents (up to 68%) of B. oleracea. Plants under As stress showed an increase in H2O2 contents (up to 32%) in roots while a decrease (up to 72%) in leaves because As is mostly retained in plant roots, while less is translocated toward the shoot, as evident from the literature. Arsenic treatments caused lipid peroxidation both in the root and leaf cells. Against As-induced oxidative stress, B. oleracea plants mediated an increase in the activities of peroxidase and catalase. Contradictory, the ascorbate peroxidase and superoxide dismutase activities slightly decreased in the As-stressed plants. In conclusion and as evident from the literature data analysis, As exposure (especially high level, 125 µM) caused pigment toxicity and oxidative burst in B. oleracea. The ability of B. oleracea to tolerate As-induced toxicity greatly varied with applied treatment levels (As-125 being more toxic than lower levels), plant organ type (more toxicity in leaves than roots) and physiological response parameter (pigment contents more sensitive than other response variables). Moreover, the multivariate statistical analysis appeared to be a useful method to estimate plant response under stress and trace significant trends in the data set.

Impact of organic and inorganic amendments on arsenic accumulation by rice genotypes under paddy soil conditions: A pilot-scale investigation to assess health risk.

In this study, we investigated the distinct effects of organic (farmyard manure (FYM), cow dung (CD), biogas slurry (BGS), sugarcane bagasse (SCB)) and inorganic (gypsum and lignite) amendments on arsenic (As) accumulation by two rice genotypes, Kainat (fine) and Basmati-385 (coarse), under As stress. Results showed that shoot As concentration was ~2-time greater in Kainat compared to Basmati-385 (3.1-28 vs. 1.7-16 mg kg-1 DW, respectively), with the minimum shoot As content observed with CD and SCB. In contrast to gypsum and lignite, grain As concentration was significantly reduced with CD and SCB for Kainat (0.29 and 0.24 mg kg-1 DW) and Basmati-385 (0.04 and 0.09 mg kg-1 DW). Data indicated that the CD and SCB also improved chlorophyll a and b contents, reduced lipid peroxidation and hydrogen peroxide production in both rice genotypes. Significantly, the CD and SCB decreased grain As concentration below the FAO safe As limit in rice grain (0.2 mg kg-1 DW), especially in coarse rice genotype (Basmati-385), resulting in negligible As-induced human health risk. This study highlights the significance of amendments and rice genotypes controlling As accumulation in rice grain, which should be considered prior to As remediation program of paddy soils for limiting exposure of humans to As via rice grain.

The potential of microbes and sulfate in reducing arsenic phytoaccumulation by maize (Zea mays L.) plants.

Arsenic (As) contamination in soil-plant system is an important environmental, agricultural and health issue globally. The microbe- and sulfate-mediated As cycling in soil-plant system may depend on soil sulfate levels, and it can be used as a potential strategy to reduce plant As uptake and improve plant growth. Here, we investigated the role of soil microbes (SMs) to examine As phytoaccumulation using maize as a test plant, under varying sulfate levels (S-0, S-5, S-25 mmol kg-1) and As stress. The addition of sulfate and SMs promoted maize plant growth and reduced As concentration in shoots compared to sulfate-treated plants without SMs. Results revealed that the SMs-S-5 treatment proved to be the most promising in reducing As uptake by 27% and 48% in root and shoot of the maize plants, respectively. The SMs-S treatments, primarily with S-5, enhanced plant growth, shoot dry biomass, Chl a, b and total Chl (a + b) contents, and gas exchange attributes of maize plants. Similarly, the antioxidant defense in maize plants was increased significantly in SMs-S-treated plants, notably with SMs-S-5 treatment. Overall, the SMs-S-5-treated plants possessed improved plant growth, dry biomass, physiology and antioxidant defense system and decrease in plant shoot As concentration. The outcomes of this study suggest that sulfate supplementation in soil along with SMs could assist in reducing As accumulation by maize plants, thus providing a sustainable and eco-friendly bioremediation strategy in limiting As exposure.

Arsenic biogeochemical cycling in paddy soil-rice system: Interaction with various factors, amendments and mineral nutrients.

Arsenic (As) contamination is a well-recognized environmental and health issue, threatening over 200 million people worldwide with the prime cases in South and Southeast Asian and Latin American countries. Rice is mostly cultivated under flooded paddy soil conditions, where As speciation and accumulation by rice plants is controlled by various geo-environmental (biotic and abiotic) factors. In contrast to other food crops, As uptake in rice has been found to be substantially higher due to the prevalence of highly mobile and toxic As species, arsenite (As(III)), under paddy soil conditions. In this review, we discussed the biogeochemical cycling of As in paddy soil-rice system, described the influence of critical factors such as pH, iron oxides, organic matter, microbial species, and pathways affecting As transformation and accumulation by rice. Moreover, we elucidated As interaction with organic and inorganic amendments and mineral nutrients. The review also elaborates on As (im)mobilization processes and As uptake by rice under the influence of different mineral nutrients and amendments in paddy soil conditions, as well as their role in mitigating As transfer to rice grain. This review article provides critical information on As contamination in paddy soil-rice system, which is important to develop suitable strategies and mitigation programs for limiting As exposure via rice crop, and meet the UN's key Sustainable Development Goals (SDGs: 2 (zero hunger), 3 (good health and well-being), 12 (responsible consumption and production), and 13 (climate action)).