Efficacy of agricultural waste derived biochar for arsenic removal: Tackling water quality in the Indo-Gangetic plain.

Arsenic (As), a geogenic and extremely toxic metalloid can jeopardize terrestrial and aquatic ecosystems through environmental partitioning in natural soil-water compartment, geothermal and marine environments. Although, many researchers have investigated the decontamination potential of different mesoporous engineered bio sorbents for a suite of contaminants, still the removal efficiency of various pyrolyzed agricultural residues needs special attention. In the present study, rice straw derived biochar (RSBC) produced from slow pyrolysis process at 600 °C was used to remove As (V) from aqueous medium. Batch experiments were conducted at room temperature (25 ± 2 °C) under different initial concentrations (10, 30, 50, 100 µg L-1), adsorbent dosages (0.5-5 µg L-1), pH (4.0-10.0) and contact times (0-180 min). The adsorption equilibrium was established in 120 min. Adsorption process mainly followed pseudo-second order kinetics (R2 ≥ 0.96) and Langmuir isotherm models (R2 ≥ 0.99), and the monolayer sorption capacity of 25.6 µg g-1 for As (V) on RSBC was achieved. Among the different adsorbent dosages and initial concentrations used in the present study, 0.2 g L-1 (14.8 µg g-1) and 100 µg L-1 (13.1 µg g-1) were selected as an optimum parameters. A comparative analysis of RSBC with other pyrolyzed waste materials revealed that RSBC had comparable adsorption ability (per unit area). These acidic groups are responsible for the electron exchange (electrostatic attraction, ion-exchange, π-π/n-πinteractions) with the anionic arsenate, which facilitates optimum removal (>60%) at 7 < pH < pHPZC. The future areas of research will focus on decontamination of real wastewater samples containing mixtures of different emerging contaminants and installation of biofilter beds that contains different spent adsorbents/organic substrates (including biochar) for biopurification study in real case scenario.

A chronicle of SARS-CoV-2: Seasonality, environmental fate, transport, inactivation, and antiviral drug resistance.

In this review, we present the environmental perspectives of the viruses and antiviral drugs related to SARS-CoV-2. The present review paper discusses occurrence, fate, transport, susceptibility, and inactivation mechanisms of viruses in the environment as well as environmental occurrence and fate of antiviral drugs, and prospects (prevalence and occurrence) of antiviral drug resistance (both antiviral drug resistant viruses and antiviral resistance in the human). During winter, the number of viral disease cases and environmental occurrence of antiviral drug surge due to various biotic and abiotic factors such as transmission pathways, human behaviour, susceptibility, and immunity as well as cold climatic conditions. Adsorption and persistence critically determine the fate and transport of viruses in the environment. Inactivation and disinfection of virus include UV, alcohol, and other chemical-base methods but the susceptibility of virus against these methods varies. Wastewater treatment plants (WWTPs) are major reserviors of antiviral drugs and their metabolites and transformation products. Ecotoxicity of antiviral drug residues against aquatic organisms have been reported, however more threatening is the development of antiviral resistance, both in humans and in wild animal reservoirs. In particular, emergence of antiviral drug-resistant viruses via exposure of wild animals to high loads of antiviral residues during the current pandemic needs further evaluation.

A chronicle of SARS-CoV-2: Part-I - Epidemiology, diagnosis, prognosis, transmission and treatment.

In order to benefit the public, community workers and scientific community, we hereby present a chronicle of SARS-CoV-2 that leads to the unseen precedent of social distancing and lockdown owing to coronavirus disease (COVID-19). Information on this life-threatening pandemic of COVID-19 is sparse and discrete; and the urgency is such that the dissemination of information is increasing with numerous daily publications on the topic. Therefore, we developed a comprehensive review on various aspects of SARS-CoV-2 and COVID-19. We scientifically compiled published research, news, and reports from various sources to comprehend and summarize the information and findings on Coronaviruses. The review explicitly covers the aspects like genome and pedigree of SARS-CoV-2; epidemiology, prognosis, pathogenesis, symptoms and diagnosis of COVID-19 in order to catalog the right information on transmission route, and influence of environmental factors on virus transmissions, for the robust understanding of right strategical steps for proper COVID-19 management. We have explicitly highlighted several useful information and facts like: i) No established relationship between progression of SARS-CoV-2 with temperature, humidity and/or both, ii) The underlying mechanism of SARS-CoV-2 is not fully understood, iii) Respiratory droplet size determines drop and airborne-based transmission, iv) Prognosis of COVID-19 can be done by its effects on various body organs, v) Infection can be stopped by restricting the binding of S protein and AE2, vi) Hydroxychloroquine is believed to be better than chloroquine for COVID-19, vii) Ivermectin with Vero-hSLAM cells is able to reduce infection by ~5000 time within 2 days, and viii) Nafamostat mesylate can inhibit SARS-CoV-2 S protein-initiated membrane fusion. We have also suggested future research perspectives, challenges and scope.

Seasonal dynamics of metal phase distributions in the perennial tropical (Brahmaputra) river: Environmental fate and transport perspective.

An evaluation of the seasonal dynamics of metal (Cd, Cr, Cu, Pb and Zn) phase distribution and speciation, along with different hydrogeochemical facies, was conducted along the entire stretch of a perennial tropical (Brahmaputra) River. Water samples were collected from twelve locations during the monsoon, post-monsoon and pre-monsoon seasons. A characteristic trend in bioavailability was observed in the sequence of Zn > Cu > Pb > Cr > Cd, reflecting non-significant seasonal changes in dissolved and particulate phase metal fractions at all twelvelocations. Partition (or distribution) coefficients (Kds) for Cu (5.30-6.50), Zn (4.47-6.44), Pb (3.69-4.97) and Cr (3.25-5.15), reflect the influences of anionic inorganic constitutents (aqua ion complexes), environmental variables, and river hydrology. MINTEQA2 calculations showed that metal forms complexes with other inorganic ions such as Cl-, SO42-, HCO3- and strong binding as organic complexes (for Cu and Pb) reduces their leaching potential to groundwater system. High log Kd values (≥5.3) and significant spatial variations at locations R3 to R8 of Pb, Cu, and Zn during pre-monsoon period may be explained by the formation of complexes with organic ligands in sewage and domestic wastes (humic and fulvic acids). Multivariate statistical analysis revealed multi-metal co-contamination, mainly of Zn, Cu, Cd and Pb and dissolved nutrients, loading in different clusters, emphasizing the importance of climatic, anthropogenic, terrigenous and lithological sources as controlling factors for seasonal metal dynamics in the river water.

Microbes involved in arsenic mobilization and respiration: a review on isolation, identification, isolates and implications.

Microorganisms play an important role in arsenic (As) cycling in the environment. Microbes mobilize As directly or indirectly, and natural/geochemical processes such as sulphate and iron reduction, oxidative sulphide mineral dissolution, arsenite (AsO33-) oxidation and arsenate (AsO43-) respiration further aid in As cycle in the environment. Arsenate serves as an electron donor for the microbes during anaerobic conditions in the sediment. The present work reviews the recent development in As contamination, various As-metabolizing microbes and their phylogenetic diversity, to understand the role of microbial communities in As respiration and mobilization. It also summarizes the contemporary understanding of the intricate biochemistry and molecular biology of natural As metabolisms. Some successful examples of engineered microbes by harnessing these natural mechanisms for effective remediation are also discussed. The study indicates that there is an exigent need to have a clear understanding of environmental aspects of As mobilization and subsequent oxidation-reduction by a suitable microbial consortium.

Efficacy of vermitechnology integration with Upflow Anaerobic Sludge Blanket (UASB) and activated sludge for metal stabilization: A compliance study on fractionation and biosorption.

Efficacy of vermi-transformation for metal partitioning and transformation from Upflow Anaerobic Sludge Blanket (UASB) and Activated Sludge (AS) was investigated. Sludge samples were mixed with cow dung (CD) in two combinations (1:1 (UASB/AS:CD)) & (2:1(UASB/AS: CD)). Fractionation study revealed that Zn, Cd & Pb were associated with reducible fractions, and Cr, Cu with oxidizable fractions. Higher removal efficiency for 1:1 (UASB/AS: CD) combination over 2:1 (UASB/AS: CD) implies the non-significant contribution of cow dung during the metal stabilization process. After vermi-remediation, maximum metal removal was achieved at 1:1 ratio than 2:1 in AS. In UASB, 1:1 ratio worked better for Cr, Zn & Cd, whereas for Cu & Zn 2:1 ratio resulted in efficient removal. Overall for both AS and UASB, efficiency was found to be higher in 1:1 treatment ratio. The value of Kd (Bio sorption) was highest in Cu followed by Cr, which indicates the closer association with the metal bound organic matter (R2 ≥ 0.99). Based on the compliance study between two estimated sorption coefficients Kd (Biosorption & Fractions), vermi-remediation was found to be effective for AS than UASB. Therefore, the obtained results clearly validate the feasibility of integration of vermi-remediation as a potential promising ecological techniques for removing metal contaminant from the wastewater. Further research is required to study the decontamination of emerging contaminants with such integrated technology, which have physico-chemical properties different than metal ions.

Microzonation, ecological risk and attributes of metals in highway road dust traversing through the Kaziranga National Park, Northeast India: implication for confining metal pollution in the national forest.

Despite the abundant literature on metal contamination through road dust (RD) in urban/suburban and residential/highway regions, the RD of highways traversing through the Kaziranga National Park, NE India, has not been studied and lacks baseline data. The objective of the present study was to ascertain the possibility of highway microzonation based on temporal and spatial variability of metal pollution level and ecological risk. It was found that the RD contains an average content of (1.7-33.5 mg/kg) for Cd, Co, Cu and Pb and (121-574 mg/kg) for Ni, Zn, Cr and Mn across the highway passing through the national forest attributed by various sources. The study revealed three possible microzones present in the studied highway NH-37 based on spatial trend of metal as well as human interference. An attempt was made to understand the possible source of metals by principal component analysis, and four sources were identified: Three were of vehicular origin, and another was related to road surface and subsurface condition. The use of noise barrier walls as an effective measure to control the translocation of RD from one place to other was recommended to reduce the hostile effects of metal accumulation in the sensitive ecosystem. Thus, the study suggested and necessitated micronizing the system based on human interference level, ecological risk factors, spatial variability of pollutants and traffic pattern for their efficient management and conservation.

Contemporary distribution and impending mobility of arsenic, copper and zinc in a tropical (Brahmaputra) river bed sediments, Assam, India.

The present study develops a correlationship among different phases of metal for developing an understanding of metal distribution and speciation, which is seldom reported in many studies. Also, the study examines the effect of sediment texture, pH, CEC, organic content and conductivity to understand the metal distribution. Bed sediment (n = 8) samples were collected from Brahmaputra river by grab sampling method to understand the spatial distribution and speciation of Cu, As and Zn. X-ray Diffraction (XRD) analysis strongly indicated the presence of arsenopyrite in Dhansirimukh site (BRS-5) sample as a dominating As containing mineral. It was found that distribution of As was relatively higher in downstream side due to increase in clay content of the sediment. Partition coefficient (kd) indicated higher mobility of Zn and Cu in comparison to As. The presence of organic matter and clay resulted in high metal content due to high CEC values, which is because of negative charge on clay and organic matter. The negative charge in clay and organic matter is due to isomorphous substitution and dissociation of organic acids, respectively. High clay content leads to Cu enrichment at BRS-4, while sandy nature of sediment at BRS-8 and absence highly active mineral leads to low Zn content. Sediment properties like organic matter and grain size were the main controlling parameters for metal concentration and its potential mobility as indicated by correlation and factor analysis. Factor analysis further revealed three probable processes governing metal enrichment and distribution viz. (i) Textural driven (ii) Metal solubility at sediment-water interface and (iii) Carbonate weathering. The study demonstrates that the textural assemblage governs metal mobility in the river sediments. Study developed a conceptual diagram for probable geochemical processes explaining the specific observations in this study, which is essential for environmental safety.