Arsenite tolerance in rice (Oryza sativa L.) involves coordinated role of metabolic pathways of thiols and amino acids

Thiolic ligands and several amino acids (AAs) are known to build up in plants against heavy metal stress. In the present study, alteration of various AAs in rice and its synchronized role with thiolic ligand was explored for arsenic (As) tolerance and detoxification. To understand the mechanism of As tolerance and stress response, rice seedlings of one tolerant (Triguna) and one sensitive (IET-4786) cultivar were exposed to arsenite (0–25 μM) for 7 days for various biochemical analyses using spectrophotometer, HPLC and ICPMS. Tolerant and sensitive cultivars respond differentially in terms of thiol metabolism, essential amino acids (EEAs) and nonessential amino acids (NEEAs) vis-á-vis As accumulation. Thiol biosynthesis-related enzymes were positively correlated to As accumulation in Triguna. Conversely, these enzymes, cysteine content and GSH/GSSG ratio declined significantly in IET-4786 upon As exposure. The level of identified phytochelatin (PC) species (PC₂, PC₃ and PC₄) and phytochelatin synthase activity were also more pronounced in Triguna than IET-4786. Nearly all EAAs were negatively affected by As-induced oxidative stress (except phenylalanine in Triguna), but more significantly in IET-4786 than Triguna. However, most of the stress-responsive NEAAs like glutamic acid, histidine, alanine, glycine, tyrosine, cysteine and proline were enhanced more prominently in Triguna than IET-4786 upon As exposure. The study suggests that IET-4786 appears sensitive to As due to reduction of AAs and thiol metabolic pathway. However, a coordinated response of thiolic ligands and stress-responsive AAs seems to play role for As tolerance in Triguna to achieve the effective complexation of As by PCs.     

The feasibility study of stabilizing the automotive paint sludge by recycling,to produce green concrete blocks,considering environmental and mechanical factors

Journal of Material Cycles and Waste Management - Managing hazardous waste generated by the industrial sector is a major environmental issue worldwide. In the automotive industry, a considerable...     

Susceptibility mapping of groundwater salinity using machine learning models

Environmental Science and Pollution Research - Increasing groundwater salinity has recently raised severe environmental and health concerns around the world. Advancement of the novel methods for...     

Benzene removal by nano magnetic particles under continuous condition from aqueous solutions

Benzene removal evaluated using Fe304 nano continuous condition. A 44 initial benzene concentration, from aqueous solutions was magnetic particles （NM） in factorial design including NM dose, contact time and pH was investigated in 16 experiments （Taguchi OA design）. The results indicated that all factors were significant and the optimum condition was： pH 8, NM dose of 2000 mg.L-1, benzene concentrations of 100 mg.L-1 and contact time of 14min. The maximum benzene uptake and distribution ratio in the optimum situation were 49.4mg.g-1 and 38.4L.g-1, respectively. The nano particles were shown to capture 98.7% of the benzene in optimum batch condition and 94.5% in continuous condition. The isotherm data proved that the Bmnauer-Emmett-Teller model fit more closely and produced an isotherm constant （b） less than one, indicating favorable adsorption. Regeneration studies verified that the benzene adsorbed by the NM could be easily desorbed by temperature, and thereby, NM can be employed repeatedly in water and wastewater management.     

Sorption-desorption of cadmium in aqueous palygorskite, sepiolite, and calcite suspensions: isotherm hysteresis

Sorption isotherms have been widely used to assess the heavy metal retention characteristics of soil particles. Desorption behavior of the retained metals, however, usually differ from that of sorption, leading to a lack of coincidence in the experimentally obtained sorption and desorption isotherms. In this study, we examine the nonsingularity of cadmium (Cd) sorption–desorption isotherms, to check the possible hysteresis and reversibility phenomena, in aqueous palygorskite, sepiolite and calcite systems. Sorption of Cd was carried out using a 24-h batch equilibration experiment with eight different Cd solution concentrations, equivalent to 20–100% of maximum sorption capacity of each mineral. Immediately after sorption, desorption took place using successive dilution method with five consecutive desorption steps. Both Cd sorption and desorption data were adequately described by Freundlich equation (0.81 < r² < 0.99). The sorption and desorption reactions, however, did not provide the same isotherms, indicating that hysteresis occurred in Cd sorption–desorption processes. The extent of hysteresis was quantified based on the differences obtained from sorption and desorption isotherms regarding the amount of Cd sorbed, the Freundlich exponent, and the Cd distribution coefficient. The results revealed that, sepiolite possessed the most hysteretic behavior among the minerals studied. Calcite showed much smaller hysteresis compared to the other two silicate clays at low Cd surface load, but its hysteresis indices significantly increased, and exceeded that of palygorskite, as the amount of Cd in the systems increased. The average amount of Cd released after five desorption steps, was 13.8%, 2.2% and 3.6% for the palygorskite, sepiolite and calcite, respectively, indicating that a large portion of Cd was irreversibly retained by the minerals.     

Biodegradation of styrene laden waste gas stream using a compost-based biofilter

Biological treatment of waste gas styrene vapor was investigated in a three-stage bench-scale biofilter. Yard waste compost mixed with shredded hard plastics in a 25:75 v/v ratio of plastics:compost was inoculated with thickened municipal activated sludge. Microbial acclimation to styrene was achieved by exposing the system to an inlet concentration (C(In)) of 0.25 gm(-3) styrene and an empty bed retention time (EBRT) of 360 s for 30 days. Under steady-state conditions, maximum elimination capacity (EC) obtained was 45 gm(-3)h(-1) at a loading rate (L) of 60 gm(-3)h(-1) (C(In) of 2 gm(-3) and EBRT of 120 s). Reduction of retention time adversely impacted the performance resulting in the maximum EC of 39 and 27 gm(-3)h(-1) for EBRT of 60 and 30 s, respectively. Evaluation of the concentration profile along the bed height indicated dominance of first-order kinetics at C(In) < or = 0.45 gm(-3) and zero-order for higher concentrations.     

Thermodynamic analysis of metals recycling out of waste printed circuit board through secondary copper smelting

Journal of Material Cycles and Waste Management - In this paper, a detailed thermodynamic analysis of processing of electronic waste (e-waste), particularly printed circuit boards (PCB), through...     

Optimal Design of Ozone Bleaching Parameters to Approach Cellulose Nanofibers Extraction from Sugarcane Bagasse Fibers

Cellulose nanofibers (CNFs) were isolated from sugarcane bagasse (SCB) through the combination of bio-refinery, sulfur-free, and totally chlorine free (TCF) chemo-mechanical pretreatments, with a focus on the optimal design of ozone bleaching parameters based on a response surface methodology (RSM). For this purpose, the most effective parameters in ozone bleaching (temperature, time, and pulp consistency) were set between 40 and 85 °C, 60 and 360 min, and 1–5 wt%, respectively. High-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), Kappa number, and scanning electron microscopy (SEM) were used to chemically and morphologically characterize the SCB fibers. The size distribution and morphology of CNFs were also evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). HPLC analysis revealed that percentage of cellulose increased from 41.5 to 91.39% after chemical pretreatments. FTIR and Kappa number analyses also confirmed the successful isolation of cellulose fibers from the SCB fibers after chemical pretreatments. Furthermore, DLS results showed that the hydrodynamic diameter of the isolated cellulose fibers reduced to 268 nm by dint of ultrasonication. Additionally, TEM images confirmed the isolation of CNFs: the average diameter of cellulose fibers decreased to about 28 nm after mechanical steps and the yield of fibrillation was found to be around 99%. According to the obtained results, the applied chemo-mechanical treatment appears to be promising for green and facile isolation of CNFs.     

Arsenic tolerances in rice (Oryza sativa) have a predominant role in transcriptional regulation of a set of genes including sulphur assimilation pathway and antioxidant system

World wide arsenic (As) contamination of rice has raised much concern as it is the staple crop for millions. Four most commonly cultivated rice cultivars, Triguna, IR-36, PNR-519 and IET-4786, of the West Bengal region were taken for a hydroponic study to examine the effect of arsenate (As^V) and arsenite (As^III) on growth response, expression of genes and antioxidants vis-à-vis As accumulation. The rice genotypes responded differentially under As^V and As^III stress in terms of gene expression and antioxidant defences. Some of the transporters were up-regulated in all rice cultivars at lower doses of As species, except IET-4786. Phytochelatin synthase, GST and γ-ECS showed considerable variation in their expression pattern in all genotypes, however in IET-4786 they were generally down-regulated in higher As^III stress. Similarly, most of antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) increased significantly in Triguna, IR-36 and PNR-519 and decreased in IET-4786. Our study suggests that Triguna, IR-36 and PNR-519 are tolerant rice cultivars accumulating higher arsenic; however IET-4786 is susceptible to As-stress and accumulates less arsenic than other cultivars.     

Modeling of Sediment Yield From Anjeni-Gauged Watershed,Ethiopia Using SWAT Model1

Setegn, Shimelis G., Bijan Dargahi, Ragahavan Srinivasan, and Assefa M. Melesse, 2010. Modeling of Sediment Yield From Anjeni-Gauged Watershed, Ethiopia Using SWAT Model. Journal of the American Water Resources Association (JAWRA) 46(3):514-526. DOI: 10.1111/j.1752-1688.2010.00431.x Abstract: The Soil and Water Assessment Tool (SWAT) was tested for prediction of sediment yield in Anjeni-gauged watershed, Ethiopia. Soil erosion and land degradation is a major problem on the Ethiopian highlands. The objectives of this study were to evaluate the performance and applicability of SWAT model in predicting monthly sediment yield and assess the impacts of subbasin delineation and slope discretization on the prediction of sediment yield. Ten years monthly meteorological, flow and sediment data were used for model calibration and validation. The annual average measured sediment yield was 24.6 tonnes/ha. The annual average simulated sediment yield was 27.8 and 29.5 tones/ha for calibration and validation periods, respectively. The study found that the observed values showed good agreement with the simulated sediment yield with Nash-Sutcliffe efficiency (NSE) = 0.81, percent bias (PBIAS) = 28%, RMSE-observations standard deviation ratio (RSR) = 0.23, and coefficient of determination (R²) = 0.86 for calibration and NSE = 0.79, PBIAS = 30%, RSR = 0.29, and R² = 0.84 for validation periods. The model can be used for further analysis of different management scenarios that could help different stakeholders to plan and implement appropriate soil and water conservation strategies.