Jayanta Kumar Biswas

Applications of biochar in redox-mediated reactions

Biochar is chemically more reduced and reactive than the original feedstock biomass. Graphite regions, functional groups, and redox-active metals in biochar contribute to its redox characteristics. While the functional groups such as phenolic species in biochar are the main electron donating moieties (i.e., reducers), the quinones and polycondensed aromatic functional groups are the components accepting electrons (oxidants). The redox capacity of biochar depends on feedstock properties and pyrolysis conditions. This paper aims to review and summarize the various synthesis techniques for biochars and the methods for probing their redox characteristics. We review the abiotic and microbial applications of biochars as electron donors, electron acceptors, or electron shuttles for pollutant degradation, metal(loid)s (im)mobilization, nutrient transformation, and discuss the underlying mechanisms. Furthermore, knowledge gaps that exist in the exploration and differentiation of the electron transfer mechanisms involving biochars are also identified.

A new pyridoxal based fluorescence chemo-sensor for detection of Zn(II) and its application in bio imaging

This paper describes the activity of a Schiff base ligand, derived from pyridoxal, as a promising fluorescence probe for biologically important Zn(II) ion sensing. A physiologically compatible pyridoxal based chemosensor PydDmen was synthesized and evaluated for its fluorescent response towards metal ions. Chemosensor PydDmen exhibits a selective turn-on type response in the presence of Zn2+ in ethanol–water mixture. The addition of EDTA quenches the fluorescence of receptor PydDmen-Zn2+, making the chemosensor PydDmen reversible. The response is specific for Zn(II) ions, and remains almost unaffected by the presence of alkali and alkaline earth metals but is suppressed to varying degrees by transition metal ions. The selectivity mechanism of PydDmen for Zn2+ is the combined effects of proton transfer between the prevailing tautomeric forms, CN isomerization and CHEF. The DFT optimized structure of the complex is compatible with elemental analysis, mass spectrometry, FT-IR, electronic and NMR spectra. The experimental and theoretical support in terms of NMR spectroscopy and DFT are provided to establish the existence of Zn2+ induced transformation of PydDmen to a 3-pyridone tautomeric form.

Fabrication of magnetic biochar as a treatment medium for As(V) via pyrolysis of FeCl3-pretreated spent coffee ground☆

This study investigated the preparation of magnetic biochar from N2- and CO2-assisted pyrolysis of spent coffee ground (SCG) for use as an adsorption medium for As(V), and the effects of FeCl3 pretreatment of SCG on the material properties and adsorption capability of the produced biochar. Pyrolysis of FeCl3-pretreated SCG in CO2 atmosphere produced highly porous biochar with its surface area ∼70 times greater than that produced in N2 condition. However, despite the small surface area, biochar produced in N2 showed greater As(V) adsorption capability. X-ray diffraction and X-ray photoelectron spectrometer analyses identified Fe3C and Fe3O4 as dominant mineral phases in N2 and CO2 conditions, with the former being much more adsorptive toward As(V). The overall results suggest functional biochar can be facilely fabricated by necessary pretreatment to expand the applicability of biochar for specific purposes.

Assessing the potential ecological risk of Co, Cr, Cu, Fe and Zn in the sediments of Hooghly–Matla estuarine system, India

Hooghly–Matla estuarine system along with the Sundarbans mangroves forms one of the most diverse and vulnerable ecosystems in the world. We have investigated the distribution of Co, Cr, Cu, Fe and Zn along with sediment properties at six locations [Shamshernagar (S1), Kumirmari (S2 and S3), Petuaghat (S4), Tapoban (S5) and Chemaguri (S6)] in the Hooghly estuary and reclaimed islands of the Sundarbans for assessing the degree of contamination and potential ecological risks. Enrichment factor values (0.9–21.6) show enrichment of Co, Cu and Zn in the intertidal sediments considering all sampling locations and depth profiles. Geo-accumulation index values irrespective of sampling locations and depth revealed that Co and Cu are under class II and class III level indicating a moderate contamination of sediments. The pollution load index was higher than unity (1.6–2.1), and Co and Cu were the major contributors to the sediment pollution followed by Zn, Cr and Fe with the minimum values at S1 and the maximum values at S5. The sediments of the Hooghly–Matla estuarine region (S4, S5 and S6) showed considerable ecological risks, when compared with effect range low/effect range median and threshold effect level/probable effect level values. The variation in the distribution of the studied elements may be due to variation in discharge pattern and exposure to industrial effluent and domestic sewage, storm water and agricultural run-off and fluvial dynamics of the region. The study illuminates the necessity for the proper management of vulnerable coastal estuarine ecosystem by stringent pollution control measures along with regular monitoring and checking program.

The Flop Side of Using Heavy Metal(oids)s in the Traditional Medicine: Toxic Insults and Injury to Human Health

Traditional medicine is the earliest healthcare system of humanity, which relies on the revered traditional legacy of healing powers hidden in the natural objects like medicinal plants, animals, etc. It encompasses the Indian Ayurveda, traditional Chinese medicine, Arabic Unani medicine, and other forms of indigenous medicine. The Ayurveda is the most commonly practised system of traditional medicine in the Indian subcontinent and has been carving niche in the Western countries. It is based on the Vedic hypothesis that there are some common cardinal premises underlying the harmony and homeostasis maintained in the microcosm (individual body) and macrocosm (nature/universe). Both man and the universe are composed of the same basic elements, and disease manifests when the balance is destabilized. Some heavy metal(oid)s are added intentionally in Ayurvedic products as it is thought that the equilibrium of lead, copper, gold, iron, mercury, silver, tin, zinc thallium, and arsenic is essential for normal functioning of the human body. Similarly, traditional Chinese medicine believes that the human body has an organic unity based on the opposing and complementary relationships of yin and yang. Such medicine also contains heavy metals which come from contaminated soil source or are deliberately added as ingredients for specific curative cause. Traditional medicine focuses on causes, not the symptoms, heal the “whole”, not the “part” by only correcting the symptoms, like the modern medicine. These low-cost medicines are thought of treating diseases and disorders without posing any risk of side effects. But it is wrong in reality, raising human health concerns and side effects due to their pharmaceutically non-validated nature and indiscriminate and irrational use. The quality, safety, and toxicity of herbal medicines have become a major concern for public health, health authorities, and pharmaceutical industries. Herbal medicines and products may contain highly active pharmacological components or contaminants including several toxic metals and metaloids. The metal(oid) contaminants or additives may be introduced during different phases such as cultivation, harvesting, collecting, cleaning, and drying of the medicinal plants in contaminated environment and/or during the processing and formulation of the herbal products. The objective of the present chapter is to show how through traditional medicine humans may be exposed to a cocktail of heavy metal(oid)s—the nonbiodegradable toxic group of environmental chemicals. Citing selected priority heavy metal(oid)s like lead, cadmium, chromium, arsenic, and mercury, it presents the spectra of vast array of toxic insults and injuries inflicted by them, ranging from cell to system levels, as well as the unique biochemical/molecular fingerprints the toxicants leave on human body.

Seasonal assessment of trace element contamination in intertidal sediments of the meso-macrotidal Hooghly (Ganges) River Estuary with a note on mercury speciation

The spatial and seasonal distribution of trace elements (TEs) (n=16) in surficial sediment were examined along the Hooghly River Estuary (~175km), India. A synchronous elevation of majority of TEs concentration (mgkg-1) was encountered during monsoon with the following descending order: Al (67070); Fe (31300); Cd (5.73); Cr (71.17); Cu (29.09); Mn (658.74); Ni (35.89). An overall low and homogeneous concentration of total Hg (THg=17.85±4.98ngg-1) was recorded in which methyl mercury (MeHg) shared minor fraction (8-31%) of the THg. Sediment pollution indices, viz. geo-accumulation index (Igeo) and enrichment factor (EF) for Cd (Igeo=1.92-3.67; EF=13.83-31.17) and Ba (Igeo=0.79-5.03; EF=5.79-108.94) suggested high contamination from anthropogenic sources. From factor analysis it was inferred that TEs primarily originated from lithogenic sources. This study would provide the latest benchmark of TE pollution along with the first record of MeHg in this fluvial system which recommends reliable monitoring to safeguard geochemical health of this stressed environment.

Electrophoresis-staining apparatus for DNA agarose gels with solution exchange and image acquisition

ABSTRACT Agarose gel electrophoresis is routinely used for the separation of nucleic acids. Gels are developed, stained, and visualized using dedicated equipment and reagents. Manufacturers have developed instrumentation with advanced features that provide good safety and user-friendly operation. However, the process of size fractionation of nucleic acids by horizontal gel electrophoresis by dye staining may be cumbersome and unsafe due to many steps and harmful chemicals. Here is reported a safe, inexpensive, time-saving, and comprehensive apparatus for gel electrophoresis, staining, and imaging. This newly modified apparatus has simple operation and uses existing equipment and off-the-shelf components for easy construction in the laboratory. The apparatus has been shown to perform agarose horizontal gel electrophoresis and associated techniques with ease and simplicity.

Impact of raking and bioturbation-mediated ecological manipulation on sediment–water phosphorus diagenesis: a mesocosm study supported with radioactive signature

The study examined the impact of raking and fish bioturbation on modulating phosphorus (P) concentrations in the water and sediment under different trophic conditions. An outdoor experiment was set to monitor physicochemical and microbiological parameters of water and sediment influencing P diagenesis. A pilot study with radioactive 32P was also performed under the agency of raking and bacteria (Bacillus sp.). Raking was more effective in release of P under unfertilized conditions by significantly enhancing orthophosphate (35%) and soluble reactive phosphate (31.8%) over respective controls. Bioturbation increased total and available P in sediments significantly as compared to control. The rates of increase were higher in the unfertilized conditions (17.6–28.4% for total P and 12.2 to 23.2% for available P) than the fertilized ones (6.5–12.4% for total P and 9.1 to 15% for available P). The combined effects of raking and bioturbation on orthophosphate and soluble reactive phosphate were also stronger under unfertilized state (54.5 and 81.8%) than fertilized ones (50 and 70%). The tracer signature showed that coupled action of introduced bacteria and repeated raking resulted in 59.2, 23 and 16% higher counts of radioactive P than the treatments receiving raking once, repeated raking and bacteria inoculation, respectively. Raking alone or in sync with bioturbation exerted pronounced impact on P diagenesis through induction of coupled mineralization and nutrient release. It has significant implication for performing regular raking of fish-farm sediments and manipulation of bottom-grazing fish to regulate mineralization of organic matter and release of obnoxious gases from the system. Further, they synergistically can enhance the buffering capacity against organic overload and help to maintain aquatic ecosystem health.

Impact of Jute Retting on Native Fish Diversity and Aquatic Health of Roadside Transitory Water Bodies: an Assessment in Eastern India

Roadside transitory water bodies being manmade depressions have a great ecological and socio-economic importance from years. The effects of agricultural runoffs, jute retting, macro-phytes infestations and inadequate rainfall in changed climate often degrade transitory water bodies’ environment while the biodiversity have impacted severely because of population pressure, over exploitation and indiscriminate use of fine meshed fishing gears as a whole. Physico-chemical and biological analysis with fish species composition, relative abundance, diversity indices like species richness, evenness and Shannon-Wiener index were carried out for pre-, during and post-jute retting season and for year mean as a whole to assess impact of jute retting on the roadside transitory water body’s environmental health and indigenous fish diversity at Sahebnagar village in Nadia District, India. All the physico-chemical parameters barring biochemical oxygen demand and water transparency remained more or less same or marginally got little changed during those three seasons. As much as 19 native fish species with varied relative abundances and dominances were identified. Jute retting impacted lower native fish diversity indices like Shannon-Wiener index values (1.94 to 2.68) clearly indicated poor to moderate pollution status of the transitory water body in that area during monsoon in particular and throughout the year in general. So we opined there should be some control over the intense jute retting in the road side transitory water bodies for sustainable management of these manmade resources.

IMPACT OF JUTE RETTING ON PHYTOPLANKTON DIVERSITY AND AQUATIC HEALTH: BIOMONITORING IN A TROPICAL OXBOW LAKE

Phytoplankton acts as a primary producer and biological filter of aquatic ecosystem. Jute retting during monsoon is a common anthropological activity in the rural Bengal. Quantitative seasonal bio-monitoring of phytoplankton community composition with relative abundance and its diversity indices was carried out in this study from April 2013 to March 2014 to assess water quality and the impact of jute retting on phytoplankton diversity of a tropical fresh water oxbow lake in Nadia district of India. We recorded a total of 34 genera of 5 distinct classes, Chlorophyceae (15), Bacillariophyceae (13), Cyanophyceae (4), Dinophyceae (1) and Euglenophyceae (1). Members of Chlorophyceae dominated throughout the year. Unlike Cyanophyceae, Bacillariophyceae was found to be significantly increased during monsoon when compared to the rest of the year. Average phytoplankton density was highest in post-monsoon (8760/L) followed by monsoon (4680/L) and pre-monsoon (3650/L). Owing to the dominance of class Chlorophyceae and Bacillariophyceae we found this lake to be oligotrophic to mesotrophic. Indices values of genera richness, Shannon-Wiener, evenness and Simpson’s diversity reached their lowest 14, 1.61, 0.61 and 0.68 in monsoon and highest 23, 2.42, 0.77 and 0.86 in post monsoon respectively. The lowest diversity values during monsoon clearly suggested that the selected lake has highest anthropogenic pollution due to jute retting which impacted significantly on phytoplankton diversity. Therefore, the lake is not conducive for fish growth especially during monsoon and we opine that there is a need to regulate jute retting process, intensity and its density in the lake during the monsoon to ensure enhanced biodiversity for sustainable management and conservation of aquatic environment of this Oxbow lake.