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One hundred forty-eight water samples were collected from in and around Chennai and 222Rn concentrations were measured using radon emanometry method. The average 222Rn concentration was estimated to be 6.88, 2.01, 1.17, 0.19 and 0.10 Bq L−1 for borewell water, openwell water, tank water, metro water and lake water, respectively, which were within the U.S. Environmental Protection Agency's (USEPA) Standard limit of 11.1 Bq L−1 and World Health Organization (WHO) global average 10 Bq L−1. The total effective dose obtained has varied from 0 to 157.57 μSv y−1 with ±10% standard deviation. The mean values were 19.608, 8.092, 4.692, 0.761 and 0.423 μSv y−1 for closed borewell, open well water, tank water, metro water and for lake water, respectively. All these values were below the reference point 0.1 mSv y−1 (100 μSv y−1) set by WHO. [ABSTRACT FROM AUTHOR]

Residential, industrial, commercial, institutional and recreational activities discharge degradable and non-degradable wastes that reach the coastal water through rivers and cause coastal pollution. In the present study, mass transport of pollutants by Adyar and Cooum Rivers to the coastal water as a result of land-based discharges was estimated during low tide. The lowest and the highest flow recorded in Adyar varied from 514.59 to 2,585.08×106 litres/day. Similarly, the flow in Cooum River fluctuated between 266.45 and 709.34×106 litres/day. The present study revealed that the Adyar River transported 53.89–454.11 t/d of suspended solids, 0.06–19.64 t/d of ammonia, 15.95–123.24 t/d of nitrate and 0.4–17.86 t/d of phosphate, 0.004–0.09 kg/d of cadmium, 0.15–1.29 kg/d of lead and 3.03–17.58 kg/d of zinc to the coastal water owing to its high discharge. Similarly, the Cooum River transported 11.87–120.06 t/d of suspended solids, 0.08–58.7 t/d of ammonia, 6.11–29.25 t/d of nitrate and 0.66–10.73 t/d of phosphate, 0.003–0.021 kg/d of cadmium, 0.02–0.44 kg/d of lead and 1.36–3.87 kg/d of zinc. A higher concentration of suspended solids was noticed in post monsoon and summer months. An increase in the mass transport of ammonia, nitrate, phosphate in summer months (April and May) and an increase in the mass transport of cadmium, lead and zinc were observed in monsoon months (October–December) in both the rivers. Thus mass transport of pollutants study reveal that Cooum and Adyar Rivers in Chennai contribute to coastal pollution by transporting inorganic and trace metals significantly through land drainage. [ABSTRACT FROM AUTHOR]

Anthropogenic activities experienced a pause due to the nationwide lockdown, imposed to contain the rapid spread of COVID-19 in the third week of March 2020. The impacts of suspension of industrial activities, vehicular transport and other businesses for three months (25 March-30 June) on the environmental settings of Chennai, a coastal megacity was assessed. A significant reduction in the key urban air pollutants [PM 2.5 (66.5%), PM 10 (39.5%), NO 2 (94.1%), CO (29%), O 3 (45.3%)] was recorded as an immediate consequence of the reduced anthropogenic activities. Comparison of water quality of an urban river Adyar, between pre-lockdown and lockdown, showed a substantial drop in the dissolved inorganic N (47%) and suspended particulate matter (41%) during the latter period. During the pandemic, biomedical wastes in India showed an overall surge of 17%, which were predominantly plastic. FTIR-ATR analysis confirmed the polymers such as polypropylene (25.4%) and polyester (15.4%) in the personal protective equipment. [Display omitted] • The impact of COVID-19 on air, water and biota in the coastal environment were studied. • Lockdown resulted in a significant reduction in key air pollutants which in turn improved the Chennai air quality up to 70%. • An increase in dissolved oxygen decreased dissolved inorganic N and chlorophyll a was recorded in coastal waters. • An overall surge of plastic-based facemasks, gloves and other PPE was recorded. • Blue economy sectors: fishing, tourism and seafood industries severely affected by the restrictions. [ABSTRACT FROM AUTHOR]

In India, scientific investigations of ocean basins have been in progress for more than five decades using indirect and direct measurement devices. These studies were aimed at resource identification, ecological, palaeo-oceanographic and palaeo-climatic research. To cater to the need of the ocean community, Remotely Operated Vehicles (ROV) rated for 6000 m (ROSUB 6000) and 500 m (PROVe-500) operational depths have been developed at the National Institute of Ocean Technology, MoES, Chennai. This article reports the design considerations for unmanned remotely operated underwater vehicles and the outcome of scientific expeditions conducted for deep sea mineral exploration, ocean biodiversity and polar science. [ABSTRACT FROM AUTHOR]

Benthic foraminifera are increasingly used as an indicator of environmental disturbance. Their sensitivities to pollutants can be reflected by changes in assemblage, which can provide useful information about ecosystem health. This study aimed to investigate the impact of organic and inorganic pollutants on the benthic ecology of the Chennai coast, with a focus on the 2017 oil spill caused by the collision of two ships. Sediment samples collected from five distinct zones along the coast were analysed for pollutants such as polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH), heavy metals (Cr, Cd, Pb) and total organic carbon (TOC). The maximum concentrations of Cr (137 μg/g), Cd (6.93 μg/g) and Pb (34.2 μg/g), as well as TPH (84.3 μg/g) and PAHs (227 ng/g), were observed. A total of 47 species of foraminifera were identified in this study, of which 12 were morphologically abnormal. In the low-impact zone, the species diversity index (H′) was higher. TPH and PAH concentrations were positively associated with abnormal species. Pollution-resistant foraminifera species include Ammonia tepida , Elphidium discoidale , and Quinqueloculina lamarckiana , while opportunistic foraminifera include Pararotalia curryi , Nonionella stella , Rosalina globularis , and Spirillina vivipara. PAHs and heavy metals were adversely correlated with foraminiferal abundance, while TPH was positively correlated. To assess the response of the benthic ecosystem to hydrocarbon pollution, indices such as the Foraminiferal Index of Environmental Impact (FIEI), Exponential (H′ bc) index and the Foraminiferal Abnormality Index (FAI) were used as environmental health proxies. FIEI, exp(H′ bc) and FAI values show the impact of hydrocarbon pollution to an extent along the northern Chennai coast. [Display omitted] • Morphological changes of benthic foraminifera to oil spill event was assessed. • An inverse correlation of Polycyclic aromatic hydrocarbon with diversity was noted. • Resistant taxa: Ammonia tepida , Elphidium discoidale , Quinqueloculina lamarckiana. • Opportunistic taxa: Nonionella stella , Rosalina globularis , Spirillina vivipara. • Foraminiferal Index of Environmental Impact & Abnormality Index are used as proxy. [ABSTRACT FROM AUTHOR]