Investigating the combined effects of pH changes and UV radiation exposure on dissolved metal-humate complexes: an important process in aquatic systems.

An in vitro study was carried out to examine the impact of UV exposure on metal-dissolved humic material (M-DHM) complexes in aqueous systems at different pH. Complexation reactions of dissolved M (Cu, Ni, and Cd) with DHM increased with the increasing pH of the solution. Kinetically inert M-DHM complexes dominated at higher pH in the test solutions. Exposure to UV radiation did affect the chemical speciation of M-DHM complexes at different pH of the systems. The overall observation suggests that exposure to increasing UV radiation increased the lability, mobility, and bioavailability of M-DHM complexes in aquatic environments. The dissociation rate constant of Cu-DHM was found to be slower than Ni-DHM and Cd-DHM complexes (both before and after UV exposure). At a higher pH range, Cd-DHM complexes dissociated after exposure to UV radiation and a part of this dissociated Cd precipitated out from the system. No change in the lability of the produced Cu-DHM and Ni-DHM complexes after UV radiation exposure was observed. They did not appear to form new kinetically inert complexes even after 12 h of exposure. The outcome of this research has important global implications. The results of this study helped to understand DHM leachability from soil and its effect on dissolved metal concentrations in the Northern Hemisphere water bodies. The results of this study also facilitated to comprehend the fate of M-DHM complexes at photic depths (where pH changes are accompanied by high UV radiation exposure) in tropical marine/freshwater systems during summer.

Psychometric validation of the modified Naranjo algorithm used in homeopathy for chronic cases.

OBJECTIVES: The modified Naranjo algorithm assesses the physician assigned cause-effect relationship for homeopathic medicines. It is being adopted in homeopathy researches, but not yet validated systematically. We intended to validate the modified Naranjo algorithm by examining its psychometric properties. METHODS: An online survey sought agreement of 25 experts on the 10 items of the tool on 5-point agreement scale. Next, 285 responses from collected prospectively from chronic cases enrolled under the clinical verification program of the council in 2018 were subjected to testing of construct validity using exploratory principal component analysis (PCA). Confirmatory factor analysis (CFA; n=150) was performed to verify the goodness-of-fit of the model. Reliability was tested using internal consistency, test-retest reliability, and inter-rater reliability by kappa statistics. RESULTS: Experts' responses mean values were 4 or higher (i.e. responses were relevant) and standard deviations were less than 1 (i.e. less heterogeneous). In PCA using varimax, all the items loaded above the pre-specified value of 0.4 and identified 4 components explaining 64.1% of variation. The goodness-of -fit of the 4-component CFA model was acceptable (chi-square 89.253, p<0.001). Internal consistency (Cronbach's alpha 0.7) was borderline; test-retest reliability was acceptable. Kappa statistics was moderate to fair, but poor for few of the items. CONCLUSIONS: Statistical evaluations indicate that the modified Naranjo algorithm is useful, but needs improvement.

A simple technique to mitigate microplastic pollution and its mobility (via ballast water) in the global ocean.

Ballast water transport is considered as one of the major vectors for dispersal of microplastics around the global oceans. In this commentary, a simple, inexpensive solution has been proposed to reduce microplastic pollution and its mobility via ballast water. A screening chamber (with stainless steel three layered mesh) is proposed to be attached to the existing Ballast Water Treatment Systems (BWTSs) in cargo ships to filter back-flushed sea water from BWTSs. The three layered screens (500, 300 and 100 µm) will not only avoid clogging and easy separation of different size groups of microplastic particles but also help in smooth discharge of water to the sea. This technique is expected to remove a large number of microplastic particles (ranging from 0.0015 to 1020 million) from a single voyage. The proposed chamber may help to collect 0.0003-204 metric tons of particles/day, depending upon the geographical location of ballast intake in the global ocean. These estimations were made by considering a daily turnover of 0.033 billion tonnes of ballast water globally. This proposed screening chamber attached to the existing BWTSs in cargo ships, along with other region-specific ocean cleaning initiatives, will help in mitigating microplastic pollution in the global ocean.

Biochemical responses of oysters in evaluating environmental quality of tropical Indian estuarine systems.

Impact of varying concentrations and counts of toxic metals and indigenous bacteria on antioxidative defense system in edible oyster, Saccostrea cucullata, collected from four tropical estuarine systems of Goa (west coast of India), are presented in this study. Relatively high abundance of bacteria was estimated from the oysters especially during monsoon season (June-September). Density of total and fecal coliforms were about 24 times higher in the organism than the surrounding water (average TC: 4360 and FC: 3475 MPN 100 ml-1). Sedimentary Cd, Pb, and Hg concentrations varied from 0.12 to 0.48, 19.28-102.48, and 0.03-0.13 mg kg-1 (dry wt.) while, bioaccumulation of Cd, Pb, and Hg in the oysters ranged from 5.17 to 10.6, 0.18-7.99, and 0.06-0.22 mg kg-1 (dry wt.) respectively. Higher degree of pollution and moderate ecotoxicological risks with increasing toxicity (36-37%) was observed in two of the tropical estuaries. Biomarker response in the oysters was somewhat inconsistent with pollution load in the estuarine systems. Elevated environmental stress was observed during pre-monsoon (March-May) followed by the monsoon period. Sedimentary metals were identified as predominant inducers of antioxidative defence system in oysters from the study areas. This study suggests that, biomarker can be useful in assessing the combined effects of metal and bacterial contaminations on native oysters and in evaluating environmental quality in tropical estuarine systems.

Post depositional changes of sedimentary organic matter influence chromium speciation in continental slope sediments - A case study.

Influences of post depositional changes of sedimentary organic matter (SOM) on chromium (Cr) speciation in continental slope sediments from the east and west coast of India are presented in this study. Average concentrations of total sedimentary Cr (CrT) in the slope areas of both the coasts were not elevated and ranged from 56.8 to 163 mg·kg-1 (avg. 97.3 ± 28.3 mg·kg-1). The geology of adjacent land masses influenced sedimentary Cr concentration in the slope areas. Geochemical fractionation study showed that a major fraction (51.6-159 mg·kg-1; avg. 89.6 ± 24.3 mg·kg-1) of the total sedimentary Cr was present in residual part of the sediments. Prime hosting phase for non-residual sedimentary Cr was oxidizable binding phase (SOM) (1.4-23.9 mg·kg-1; avg. 6.7 ± 6.3 mg·kg-1) followed by reducing binding phase (Fe/Mn-oxyhydroxide phase) (0.1-1.7 mg·kg-1; avg. 0.7 ± 0.3 mg·kg-1). Concentration of Cr (VI) in the slope sediments, varied from 0.2 to 8.3 mg·kg-1 (avg. 1.2 ± 1.0 mg·kg-1), was also predominantly associated with the SOM. The δ13Corg values of the SOM (ranged from -19.4 to -21.4‰; avg. -20.3 ± 0.5‰) suggests that they were derived from marine sources. Based on molar C/N ratio (ranged from 6.3-12.9; avg. 9.0 ± 2.0), the SOM were classified as labile organic matter. Increasing molar C/N ratio in the studied sediments was used as a proxy to reflect post depositional changes of the SOM. Association of normalized Cr (VI) (with respect to CrT) increased with increasing SOM concentration by 0.008 mg·kg-1. One unit increase of sedimentary molar C/N ratio was found to increase normalized Cr (VI) (w.r.t. CrT) by 0.003 mg·kg-1 in the sediments. This study suggests that post-depositional changes of SOM may increase Cr binding capacity and control its speciation and mobility in marine sediment system.

Copper dynamics in a tropical estuarine system during dry season.

This is the first study to comprehend copper (Cu)-dynamics in a monsoon fed Indian estuarine system (the Mandovi estuary from the central west coast of India). Distribution and speciation of Cu in estuarine sediment, pore water, suspended particulate matter (SPM) and water column was used to understand geochemical cycling of Cu in the estuary. Geochemical fractionation study reveals that sedimentary organic carbon (Corg) was the major hosting phase for non-residual Cu in the sediments. Experimental analysis and chemical speciation modelling suggests that leaching of sedimentary Cu2+, CuCO3 and a fraction of Cu-Corg complexes increased Cu-concentrations in the pore water towards the downstream of the estuary. Dissolved Cu concentration in overlying water column was observed to increase with increasing Cu concentrations in the pore water. This study suggests that chemical speciation of sedimentary Cu play key role in controlling its distribution and dynamics in the tropical estuarine system during dry period.

Geochemical fractionation study in combination with equilibrium based chemical speciation modelling of Cd in finer sediments provide a better description of Cd bioavailability in tropical estuarine systems.

Geochemical fractionation study of cadmium (Cd) in combination with equilibrium based chemical speciation modelling (visual MINTEQ) in finer sediment samples (silt and clay portion), provided a better description of Cd bioavailability for sessile organisms (like oysters) in the Zuari estuary, west coast of India. A substantial fraction of total Cd in the finer sediment samples was present as water soluble, exchangeable and carbonate/bicarbonate forms and showed a strong positive relationship with Cd-bioaccumulation in oysters (Magallana sp.) from the study area. Cadmium bioaccumulation (ranged from 2.4-7.9 mg·kg-1) in soft tissues of the edible oyster was high (higher than the maximum permissible limit for human consumption) throughout the study period of one year. Equilibrium based speciation modelling suggest that sedimentary CdCl2, CdCl+ and Cd2+ were responsible for Cd bioaccumulation in the oysters. This study describes that combination of geochemical fractionation study of metals in finer sediments and equilibrium based speciation modelling can be very useful in comprehending link between sedimentary metal speciation and its bioaccumulation in sessile organisms.

Evidence for increasing anthropogenic Pb concentrations in Indian shelf sediments during the last century.

India is industrializing rapidly and with this there comes higher releases of contaminants into the environment. Change in Pb deposition over the last century on the eastern (off Andhra Pradesh) and western (off Karnataka) shelves of India was investigated based on the data extracted from two sediment cores covering the past ~114 and ~145 yrs. The variations of the total Pb content, its enrichment factor, and concentrations of non-residual Pb in both the sediment cores document that there was a gradual increase in anthropogenic Pb input into the coastal sediments of India over the last century. Sediment leachates were used to monitor the increase in anthropogenic Pb input and its Pb isotope composition. The anthropogenic end member composition of the western shelf sediment location (206Pb/207Pb: 1.105; 206Pb/208Pb: 2.149) was significantly less radiogenic than the eastern shelf isotopic composition (206Pb/207Pb: 1.145; 206Pb/208Pb:2.120). A binary mixing model suggests that Pb emitted from the heavy industries (e.g., ore mining, Pb processing and smelting plants) of India has been the major source of anthropogenic Pb to the sediments of western continental shelf. In contrast, the isotopic signatures suggest that coal combustion is responsible for elevated anthropogenic Pb levels in the sediments from the eastern shelf of India.

Exposure to Nitrogen Dioxide (NO2) from Vehicular Emission Could Increase the COVID-19 Pandemic Fatality in India: A Perspective.

The corona virus-2019 (COVID-19) is ravaging the whole world. Scientists have been trying to acquire more knowledge on different aspects of COVID-19. This study attempts to determine the effects of COVID-19, on a large population, which has already been persistently exposed to various atmospheric pollutants in different parts of India. Atmospheric pollutants and COVID-19 data, obtained from online resources, were used in this study. This study has shown strong positive correlation between the concentration of atmospheric nitrogen dioxide (NO2) and both the absolute number of COVID-19 deaths (r = 0.79, p < 0.05) and case fatality rate (r = 0.74, p < 0.05) in India. Statistical analysis of the amount of annual fossil fuels consumption in transportation, and the annual average concentration of the atmospheric PM2.5, PM10, NO2, in the different states of India, suggest that one of the main sources of atmospheric NO2 is from fossil fuels combustion in transportation. It is suggested that homeless, poverty-stricken Indians, hawkers, roadside vendors, and many others who are regularly exposed to vehicular exhaust, may be at a higher risk in the COVID-19 pandemic.

Operationally defined mercury (Hg) species can delineate Hg bioaccumulation in mangrove sediment systems: A case study.

This study investigated the linkage between mercury (Hg) speciation in the surficial sediments from a mangrove ecosystem of the Zuari Estuary, west coast of India, with Hg bioaccumulation in gastropods collected from the same area. Multiple operationally defined protocols and methods were used for determination of Hg speciation study in the mangrove sediments. Moderately low concentrations of Hg were observed in the sediments, ranging from 37.3 ±â€¯1.9 to 79.6 ±â€¯4.0 µg/kg. Geochemical fractionation showed that a significant part of sedimentary Hg was present within the structure of the sediment (residual fraction) and not bioavailable. Non-residual Hg was primarily associated with oxidizable (sedimentary organic matter (SOM) or sulfide) binding phase of the sediments, and ranged from 9.2 ±â€¯0.3 to 78.5 ±â€¯3.9 µg/kg. Concentration of methylmercury (MeHg) (a neurotoxin) in the sediments varied from 1.7 ±â€¯0.1 to 4.4 ±â€¯0.1 µg/kg. l-Cysteine, a suitable complexing ligand, extractable Hg concentration in the sediments ranged from 4.3 ±â€¯0.1 to 15.9 ±â€¯0.3 µg/kg. Statistical analysis suggested that MeHg was adsorbed on Fe/Mn oxyhydroxide phases in the sediments. l-Cysteine was found to extract sedimentary MeHg and thermodynamically less stable Hg-SOM complexes from the sediments. Concentrations of bioaccumulated Hg in soft tissues of the gastropod, Pirenella cingulata, ranged from 57.6 ±â€¯4.4 to 224.4 ±â€¯7.2 µg/kg. Positive correlations existed between the concentration of bioaccumulated Hg in the gastropods and the concentrations of Hg associated with the oxidizable phase, sedimentary MeHg and l-Cysteine extracted Hg in the sediments. This study indicated that operationally defined Hg species can be useful in estimating bioavailable Hg to obligatory deposit feeder in tropical mangrove systems.

Molecular characteristics of sedimentary organic matter in controlling mercury (Hg) and elemental mercury (Hg0) distribution in tropical estuarine sediments.

Sedimentary organic matter (SOM) plays an important role in hosting and reducing HgII in marine/estuarine sediment. This study provides a better understanding on the influence of nature of SOM, in regulating sedimentary mercury (Hg) and elemental mercury (Hg0) distribution, and speciation in the Zuari and Mandovi Estuaries that are representative of monsoon fed tropical estuaries, located in the central west coast of India. Salinity of the overlying water column controlled the physical and chemical characteristics of SOM in the estuarine systems. The high molecular weight (MW) SOM dominated at the mid and upstream (low salinity region) of the estuaries, whereas, the low MW SOM prevailed at the downstream (high salinity region). Sediment Hg showed more affinity towards the SOM of high MW. Increasing MW of SOM increased total sedimentary HgT in both the estuaries. SOM with low MW in the estuarine sediment displayed a negative relationship with the sediment Hg concentration. Distribution of Hg0 concentration in the estuarine sediment suggests that reduction of HgII in presence low MW SOM was a dominant process. It was also found that distribution and speciation of Hg0 in the estuarine sediment depends on the quantity, quality of the SOM, and the total sediment Hg loading. This study demonstrated that the competition between Hg-SOM complexation and HgII reduction by SOM controls HgII/Hg0 distribution in tropical estuarine sediment systems.

Snapshot of environmental condition in different tropical estuarine systems by using S. cucullata (an edible oyster) as bio-indicator.

Accumulation of toxic metals and indigenous bacteria in oyster, (Saccostrea cucullata) and their impact on antioxidant enzyme activities in the biological system was studied and used to provide snapshot of environmental condition in different tropical estuarine systems. The sedimentary Cd, Pb, and Hg concentration varied from 0.1 to 1.8, 22.0 to 98.0, and 0.03 to 0.11 mg kg-1 (dry wt.) respectively. The bioaccumulated Cd, Pb, and Hg concentration in the oysters ranged from 3.6 to 9.0, 0.03 to 8.0, and 0.06 to 0.1 mg kg-1 (dry wt.) respectively. In the oyster, the Cd concentration was well above the safe limit whereas the Pb and Hg concentrations were below the safe limit recommended by the European Commission (EC No. 1881/2006) for human consumption. The MPN value in the raw oyster for fecal coliforms (33-110 × 103/100 g) exceeded the United States Food and Drug Administration (USFDA) approved limits. Increase in antioxidant enzymes (catalase, superoxide dismutase, glutathione-s-transferase, and metallothionein) activities with increasing pollutants loading was observed. The activities of antioxidant enzymes in the oyster were found to be very useful tool for evaluating environmental condition in any tropical estuarine systems.

Seawater intrusion and resuspension of surface sediment control mercury (Hg) distribution and its bioavailability in water column of a monsoonal estuarine system.

There is limited knowledge regarding seawater intrusion on Hg distribution in monsoon fed tropical estuarine systems during dry season (February to May). This study examined the influence of resuspension of estuarine sediment and intrusion of Hg bound SPM (HgSPM) (by the tide) from the outside of an estuary in controlling distribution, mobility, and bioavailability of Hg within the estuarine systems during the dry season. This investigation was carried out in the Mandovi estuary, a monsoon fed tropical estuary from the central west coast of India. Total Hg concentrations in the water column showed an increasing trend from upstream to downstream of the estuary. The concentration of Hg in the water column of the estuary was much below the concentration recommended by the EPA for aquatic life ambient water quality. Dissolved Hg (HgDissolved) was found to associate mainly with the higher molecular weight fraction of dissolved organic matter (DOM). A significant portion of the total Hg in the water column was present as HgSPM. The average bio-accumulated Hg concentration in edible oyster was high (collected from the estuary) during the dry season compared to the wet season (June to September). This study reveals that resuspension of Hg associated finer sediment particles and intrusion of HgSPM from the outside of the estuary may increase bioavailability of Hg in the Mandovi estuarine systems during the dry season. It is suggested that Hg bioaccumulation in commercially important biological species from different tropical estuarine system may increase during the dry season. The outcome of this research can be useful for policy making and to take proper decision to reduce and control Hg/toxic metals pollution (if any) in tropical estuarine system.

Effect of pH on transport and transformation of Cu-sediment complexes in mangrove systems.

Impact of pH variation of overlying water column on transport and transformation of Cu-sediment complexes in the bottom mangrove sediments was investigated by using different metal extraction studies. The total Cu concentration in the studied sediments varied from ~64 ±â€¯1 to 78 ±â€¯2 mg·kg-1. The sequential extraction study showed that a major part of the sedimentary Cu (85-90% of the total sedimentary Cu) was present within the structure of the sediments with minimum mobility and bioavailability. The redistribution of non-residual Cu among the different binding phases of the sediments was observed at different pH. It was found that Cu shifted from the different non-residual binding phases to the organic binding phase of the sediments at higher pH. Partial leaching of sedimentary Cu-SOM complexes (with increasing stability as determined by kinetic extraction study) was observed at higher pH. This study infers that increase in pH of overlying water column may release Cu-SOM complexes and increase the mobility of Cu-complexes in mangrove systems.

Kinetic and equilibrium based fractionation study of Pb in continental shelf sediment of India.

Two independent analytical methods (kinetic and sequential extraction protocols) were used to understand the distribution, stability, and lability of Pb-sediment complexes in Indian continental shelf. The concentrations of sedimentary Pb varied from 12.0±0.6 to 30.4±0.1mg·kg-1 and 15.9±0.3 to 36.7±0.4mg·kg-1 in the western and eastern shelf of India respectively. The kinetic extraction study showed that higher proportion of labile Pb-complexes were present in the eastern shelf sediments (~24% of total Pb) than the western shelf sediments (~14% of total Pb). The sedimentary organic matter was found to regulate lability of sedimentary Pb complexes. The sequential extraction study suggested that Fe/Mn oxyhydroxide were the primary hosting phase for labile Pb complexes. This study showed that water soluble, exchangeable, carbonate/bicarbonate-Pb complexes in the sediments was labile. This study provides a better physicochemical description of stability or lability of Pb complexes in the coastal sediment of India.

An insight into mercury reduction process by humic substances in aqueous medium under dark condition.

Mercury (Hg) reduction by humic substances (HS) in the aquatic medium under the dark condition is a poorly understood but important process in Hg biogeochemical cycling. In this study, an effort was made to provide a better understanding of Hg(II) reduction by well-characterized humic substances under dark condition. Reduction of Hg(II) by dissolved HS in aquatic systems increases with increasing Hg loading. However, Hg(II) reduction gradually decreases with the increasing total S content and oxygen containing functional groups in the dissolved HS under dark condition. Increasing major cation concentration decreases the rate of Hg(II) reduction in aquatic systems. High concentration of Ca2+ ion slows down the intermolecular electron transfer from HS to Hg(II) and inhibits the formation of Hg0 in absence of light. This study indicates that complexation of Hg(II) and HS is essential for Hg reduction under dark condition.

Mercury exposure and Alzheimer's disease in India - An imminent threat?

India is an industrial giant with one of the fastest growing major economies in the world. Primary energy consumption in India is third after China and the USA. Greater energy production brings the burden of increasing emissions of mercury (Hg). India ranks second for Hg emissions. Rising atmospheric Hg release, high Hg evasion processes, and increasing monomethylmercury (highly neurotoxin) accumulations in marine food products increase the potential for human and ecosystem Hg exposure. Hg has been identified to increase the risk of getting Alzheimer's disease (AD). There are increasing reports of AD and dementia in different age groups in India. The relationship between increasing Hg exposure and increasing neurodegenerative disorder in India is not known. This commentary points to the need for better understanding of the relationship between Hg release and AD in India, and other countries, and how to protect human health and the environment from the adverse effects of Hg.

Oyster reef restoration in controlling coastal pollution around India: A viewpoint.

Coastal waters receive large amounts of nutrients and pollutants from different point and nonpoint sources through bays and estuaries. Excess supply of nutrients in coastal waters may have detrimental effects, leading to hypoxia and anoxia from eutrophication. Reduction in concentrations of excess nutrients/pollutants in bays/estuarine system is must for healthy coastal ecosystem functioning. Conservations of bays, estuaries and coastal zones are must for sustainable development in any maritime country. Excellent ability of oyster in removing and controlling the concentrations of nutrients, pollutants, suspended particulate matters from bays and estuarine waters stimulated me to provide a viewpoint on oyster reef restoration in controlling nutrient/heavy metals fluxes and marine coastal pollution around India. Oyster reefs restoration may decrease nutrient and heavy metals fluxes in coastal waters and reduce the intensity of oxygen depletion in the coastal Arabian Sea (seasonal) and Bay of Bengal. However, extensive research is recommended to understand the impact of oyster reef restoration in controlling coastal pollution which is essential for sustainable development around India.

Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India.

This study describes the effect of varying bottom-water oxygen concentration on geochemical fractionation (operational speciation) of Cu and Pb in the underneath sediments across the oxygen minimum zone (Arabian Sea) in the west coast of India. Both, Cu and Pb were redistributed among the different binding phases of the sediments with changing dissolved oxygen level (from oxic to hypoxic and close to suboxic) in the bottom water. The average lability of Cu-sediment complexes gradually decreased (i.e., stability increased) with the decreasing dissolved oxygen concentrations of the bottom water. Decreasing bottom-water oxygen concentration increased Cu association with sedimentary organic matter. However, Pb association with Fe/Mn-oxyhydroxide phases in the sediments gradually decreased with the decreasing dissolved oxygen concentration of the overlying bottom water (due to dissolution of Fe/Mn oxyhydroxide phase). The lability of Pb-sediment complexes increased with the decreasing bottom-water oxygen concentration. This study suggests that bottom-water oxygen concentration is one of the key factors governing stability and lability of Cu and Pb complexes in the underneath sediment. Sedimentary organic matter and Fe/Mn oxyhydroxide binding phases were the major hosting phases for Cu and Pb respectively in the study area. Increasing lability of Pb-complexes in bottom sediments may lead to positive benthic fluxes of Pb at low oxygen environment.