Application of autochthonous extremophilic Bacillus xiamenensis in remediation of groundwater- A sorption-based metal cleaning approach

Surface water and groundwater used for drinking and agricultural purposes are contaminated due to anthropogenic and geogenic activities. Escalated metal concentrations, xenobiotic pollutants, competitive ions, and reusability issues are hindrances to decontamination. Moreover, the expensive purification technology brings obstacles to the underdeveloped community from availing clean water. In this context, the present work offers a sustainable cost-effective approach by providing an effective and sustainable sorption-based purification method by novel polyextremophilic bacteria Bacillus xiamenensis ISIGRM16 isolated from metal-rich industrial waste, red mud. Batch adsorption study revealed that the bacterium can remove Cd2+(>99%), Ni2+(>85%), and Cr6+(>40%) from aqueous solution. The optimum parametric conditions for the removal of Cd2+ and Ni2+ were observed at a temperature of 30 °C and a pH of 6, while for Cr6+ removal, the optimal conditions were a temperature of 45 °C and a pH of 2. The adsorption process of Cd2+ was best explained by Freundlich isotherm (R2 ≥ 0.95), revealing multilayer adsorption. Ni2+ and Cr6+ followed the Langmuir isotherm, indicated adsorption onto the monolayer surface. The interaction mechanism was determined to be 2nd order kinetics, with both exothermic (Cd2+, Ni2+) and endothermic (Cr6+) characteristics. The maximum adsorption capacities were found to be 31.42, 29.30, and 15.21 mg g−1 for Cd2+, Ni2+, and Cr6+ respectively. In the ternary system, the adsorption capacity followed the order Ni2+ > Cd2+ > Cr6+, as confirmed by both their relative adsorption capacity and from analysis visual MINTEQ. Microscopic and spectroscopic analyses revealed, altered cell morphology, metal deposition on the bacterial cell surface, and the involvement of hydroxyl, carboxyl, and amide groups in the elimination of Cd2+, Ni2+, and Cr6+. Further the sequential adsorption-desorption study confirmed a significantly preserved removal efficacy (p < 0.05), indicating the advantageous use of the bacterium as a biosorbent

Zinc and iron enrichment of vermicompost can reduce the arsenic load in rice grain: An investigation through pot and field experiments

The heavy metalloid arsenic (As), occurring in both trivalent and pentavalent is extremely toxic and has detrimental effect on humans through water-soil-crop transfer. Previously organic and inorganic amendments have been used separately for mitigation of As in rice but there exists a research gap regarding use of them simultaneously. In this study, both pot and field scale investigations were undertaken for four consecutive years in As-contaminated locations to assess the efficacy of zinc (Zn) and iron (Fe)-enriched vermicompost in reducing the As uptake in rice grain. Altogether seven types of vermicompost and three application rates were evaluated. The treatment combination V4D1 (enriched vermicompost V4 applied to soil at 3t/ha) recorded the lowest soil available As (2.525mgkg−1) and the highest soil available As (2.982mgkg−1) was observed with V5D3 (enriched vermicompost V5 applied to soil at 1.5t/ha). Application of enriched and non-enriched vermicompost reduced As in grain by 58.14 and 31.40% respectively over no vermicompost (control). The partial dependence plot from stepwise regression modelling of different fractions of As revealed that an increase in organically bound As resulted in a decrease in the availability of As and hence uptake by rice. Further, Zn and Fe-enriched vermicompost resulted in increase of iron plaque formation on the root. A significant positive relationship (r=0.462) was observed between dithionite-citrate-bicarbonate (DCB) extractable -Fe andAs. A significant negative correlation (r=˗0.410) between DCB-Fe and grain As, advocates better root plaque formation resulting a higher capacity to sequester As onto the root surface and reducing its's entry into the rice system. The carcinogenic risk somewhat was benign (TCR of 2.69×10−3 and SAMOE of 0.101) against no vermicompost (TCR of 6.64×10−3 and SAMOE of 0.04). Therefore enriching vermicompost with ZnSO4 and FeSO4 at 10% dry weight basis (V4) of the composting substrate can lower arsenic build-up in rice grains without affecting yield

Spatial variability of groundwater quality of Sabour block, Bhagalpur district (Bihar, India)

This paper examines the quality of groundwater of Sabour block, Bhagalpur district of Bihar state, which lies on the southern region of Indo-Gangetic plains in India. Fifty-nine samples from different sources of water in the block have been collected to determine its suitability for drinking and irrigational purposes. From the samples electrical conductivity (EC), pH and concentrations of Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Potassium (K+), carbonate ion (CO 2−3), Bicarbonate ion (HCO -3), Chloride ion (Cl−), and Fluoride (F−) were determined. Surface maps of all the groundwater quality parameters have been prepared using radial basis function (RBF) method. RBF model was used to interpolate data points in a group of multi-dimensional space. Root Mean Square Error (RMSE) is employed to scrutinize the best fit of the model to compare the obtained value. The mean value of pH, EC, Ca2+, Mg2+, Na+, K+, HCO3 −, Cl−, and F− are found to be 7.26, 0.69, 38.98, 34.20, 16.92, 1.19, 0.02, and 0.28, respectively. Distribution of calcium concentration is increasing to the eastern part and K+ concentrations raise to the downstream area in the southwestern part. Low pH concentrations (less than 6.71) occur in eastern part of the block. Spatial variations of hardness in Sabour block portraying maximum concentration in the western part and maximum SAR (more than 4.23) were recorded in the southern part. These results are not exceeding for drinking and irrigation uses recommended by World Health Organization. Therefore, the majority of groundwater samples are found to be safe for drinking and irrigation management practices

Meta-Analysis of Biochar as an Amendment for Arsenic Mitigation in Paddy Soils

Purpose of Review The purpose of this review is to evaluate the effectiveness of biochar in immobilizing arsenic (As) in contaminated paddy soils and its impact on As availability and bioaccumulation in rice, as well as rice plant biomass. Recent Findings Recent studies have focused on managing As contamination in agricultural fields, with a particular focus on South and Southeast Asia, where rice, a primary food source and As accumulator, is of significant concern. Biochar, a product of biomass pyrolysis, has emerged as a viable solution for environmental remediation due to its effectiveness in immobilizing metal(loid)s in water and soil. The successful implementation of biochar as a soil amendment strategy has led to growing interest in its use as an effective means of reducing the bioaccumulation and availability of metal(loid)s, including As. Summary A meta-analysis of 25 studies revealed that biochar generated from maize and sewage sludge successfully reduced As availability and bioaccumulation in rice grains. In addition, the use of biochar led to higher biomass and yield of rice crops compared to control groups. Modified biochar was more effective in decreasing As availability, likely due to interactions with iron and calcium phases or complexes occurring in or on the biochars. Nevertheless, at elevated biochar dosages, As mobilization was noted in field conditions which warrants further investigation

The distribution, fate, and environmental impacts of food additive nanomaterials in soil and aquatic ecosystems.

Nanomaterials in the food industry are used as food additives, and the main function of these food additives is to improve food qualities including texture, flavor, color, consistency, preservation, and nutrient bioavailability. This review aims to provide an overview of the distribution, fate, and environmental and health impacts of food additive nanomaterials in soil and aquatic ecosystems. Some of the major nanomaterials in food additives include titanium dioxide, silver, gold, silicon dioxide, iron oxide, and zinc oxide. Ingestion of food products containing food additive nanomaterials via dietary intake is considered to be one of the major pathways of human exposure to nanomaterials. Food additive nanomaterials reach the terrestrial and aquatic environments directly through the disposal of food wastes in landfills and the application of food waste-derived soil amendments. A significant amount of ingested food additive nanomaterials (> 90 %) is excreted, and these nanomaterials are not efficiently removed in the wastewater system, thereby reaching the environment indirectly through the disposal of recycled water and sewage sludge in agricultural land. Food additive nanomaterials undergo various transformation and reaction processes, such as adsorption, aggregation-sedimentation, desorption, degradation, dissolution, and bio-mediated reactions in the environment. These processes significantly impact the transport and bioavailability of nanomaterials as well as their behaviour and fate in the environment. These nanomaterials are toxic to soil and aquatic organisms, and reach the food chain through plant uptake and animal transfer. The environmental and health risks of food additive nanomaterials can be overcome by eliminating their emission through recycled water and sewage sludge. [Abstract copyright: Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.

Deriving arsenic concentration guideline values for soil and irrigation water for rice cultivation

Arsenic (As) is a naturally occurring, toxic trace element that can be found in irrigation water, soil, and crops. Rice accumulates higher concentrations of As in its grains than other cereals like wheat and barley. This leads to concern over dietary As exposure, especially in areas of India, Bangladesh, Nepal, Taiwan, Vietnam, and Thailand. This present study has been undertaken to manage the risk posed by rice grown in As-contaminated areas. The objectives of the study were to determine guideline values for total and bioavailable As in soil, as well as As levels in irrigation water, using predictability models. Additionally, the efficacy of biochar as an amendment for As-contaminated soils in rice cultivation was assessed through a meta-analysis. Meta-analysis of a database compiled from an extensive literature review was undertaken using decision tree (DT) and logistic regression (LR) machine learning models to evaluate the relationship between As concentrations in rice grain, soil, and irrigation water. Soil total As was a stronger predictor of As in rice grain than irrigation water As. Both the DT and LR models successfully predicted the soil concentrations above which As in grain would exceed the Codex recommendation. Subsequent field studies in West Bengal, India in 2021 provided validation data, which demonstrated that 14 mg kg-1 of total As in soil was an appropriate guideline value for the safe cultivation of rice. The concentration of bioavailable As in paddy soil was predicted using random forest (RF), gradient boosting machine (GBM), and LR models. The LR model was the better performing, identifying bioavailable As, total As, available iron (Fe), and organic carbon as significant predictors of grain As. Based on the LR model's partial dependence plots and individual conditional expectation plots, 5.70 mg kg−1 was the limit for bioavailable As in soil. An incubation study was conducted using monolithic soil columns collected from 10 As-contaminated sites. Results were analysed using linear discriminant analysis (LDA) and LR, considering the As dose, soil pH, organic carbon, clay, available Fe, phosphorus, and total As. The LR model performed best, predicting 190 L-1 as the guideline value for irrigation water. To support remediation of As-contaminated soil, biochar was evaluated as a potential soil amendment. A meta-analysis indicated that biochar could be an effective tool in the sequestration of As in soil, but further research is required under realistic field conditions. This study has provided the first guideline values for As in soil and irrigation water and identified a potential management option (soil remediation using biochar). The findings have direct relevance to rice farmers and regulators, with the potential to deliver significant public health benefits in As contaminated regions

Assessing equilibria of organo-arsenic complexes and predicting uptake of arsenic by wheat grain from organic matter amended soils

In view of limited information, a laboratory experiment was conducted to study the stability of organo-arsenic complexes as affected by competing anions i.e. phosphate, nitrate and sulphate. For this purpose, humic acid (HA) and fulvic acid (FA) were extracted from farmyard manure (FYM), vermicompost (VC), sugarcane bagasse (SB) and soil. A pot experiment was also conducted with 4 levels each of arsenic (As) (10, 20, 30 and 40  mg  kg−1) and amendments (no amendment, FYM, VC and SB at the rate of 10  t  ha−1 each). Results indicate that stability of FA extracted from sugarcane bagasse have the highest stability constant (log K) as 9.77 and the corresponding mole ratio (x) value of 1.51. The phosphate was the most effective in replacing As from organo-As complexes followed by sulphate and nitrate. Under pot culture study, As content in wheat grain was the lowest in sugarcane bagasse amended soil followed by FYM and VC at all levels of As application. Solubility-free ion activity model was most effective in predicting As uptake by wheat grain based on Olsen extractable As, pH and Walkley & Black organic C. Efficacy of organic amendments in reducing health hazard for intake of As through consumption of wheat grain grown on contaminated soil was also reflected in the values of hazard quotient (HQ)

Effect of potassium solubilizing bacteria and waste mica on potassium uptake and dynamics in maize rhizosphere

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Chemical fractions and response of cauliflower (Brassica oleracea var. botrytis) to soil applied boron

The present study was conducted with an objective to estimate the distribution of boron (B) application in various soil fractions and their plant response for assessing the availability in the soil. Two soils (alluvial and red soil) and five levels of B (0, 0.5, 1, 2 and 3 mg B kg−1 soil) were applied in the pot experiment, and pots were sown with cauliflower (Sabour Agrim) arranged in a completely randomized block design (CRD) with three replications. Result showed that the curd yield of cauliflower increased significantly upto 2 mg B kg−1 soil irrespective of soils. The percent yield increase was 14.78 and 15.01 in alluvial and red soil over the control, respectively. The initial total B content was 35.88 (alluvial soil) and 15.51 (red soil) mg·kg−1. The mean content of Fraction I, II, III, IV and V in alluvial soil was 1.11, 1.54, 0.65, 1.49, and 95.18% and in red soil was 2.68, 4.47, 6.62, 2.50, and 83.59% of the total soil B, respectively. For changes in amount of B fractions due to B applications there was significant effect on all the fractions except Fraction II. The increase in apparent B uptake was 0.43 mg B kg−1 in alluvial soil and 0.25 mg B kg−1 in red soil over the control (0 mg B kg−1 soil). Regression equation of yield and B fractions showed the relationship between first four fractions to the yield. Residual fraction was found to be collinear during calculation. Overall the study predicted the bioavailability and dynamics of B in the two distinct soils

Complexation, retention and release pattern of arsenic from humic/fulvic acid extracted from zinc and iron enriched vermicompost

Arsenic (As) is a highly poisonous heavy metal with major environmental ramifications. Inorganic components such as zinc (Zn) and iron (Fe), as well as organic vermicompost, have been used as management solutions, with limited attempts of using them together. The current study involved preparing non-enriched vermicompost as well as six distinct Zn and Fe enriched vermicomposts and analyzing their chemical composition using the standard procedures. Organic fractions from these seven vermicompost and arsenic polluted soils of West Bengal, India were recovered and separated into humic (HA) and fulvic acid (FA) fractions. Potentiometric titrations, viscometric assays, and visible spectrophotometry were used to characterize the HA and FA samples. In aqueous phase the stability constant (log K) of the complexes formed with As indicates that stability of FA extracted from enriched vermicompost V4 (Zn and Fe sulphate @ 10% w/w dry weight basis of composting substrates before application of vermiworms) was maximum as 10.20 with a mole ratio (x) value of 1.36. Fourier-transform infrared (FT-IR) spectroscopy and Scanning Electron Microscopy (SEM) studies confirmed the complexation of As with HA/FA. The release isotherm of As from the HA/FA complexes in the presence of competitive oxy-anions was found to follow the order of sulphate > nitrate > phosphate