Comparing deep-sea polymetallic nodule mining technologies and evaluating their probable impacts on deep-sea pollution.

Deep-sea polymetallic nodules (PMN) hold promise as a future resource, with various consortia like MOES, IOM, GSR, KORDI, and COMRA actively exploring mining possibilities. However, current technologies lack environmental sustainability. This study comprehensively compares the technologies proposed by different consortia for deep sea mining (DSM). It evaluates the designs and prototypes of key components like crawlers, conveyor belts, crushers, riser pipes, and slurry tailing discharge mechanisms for their technical feasibility and environmental impact. Environmental concerns regarding sediment disturbances, nodules pick-up methods, crushing, and tailing material filtration are addressed in this article. It is suggested that further research and development efforts are needed to optimize technologies and integrate effective environmental protection measures into DSM operations.

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.

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.

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.

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.