Monitoring waste metal pollution at Ganga estuary via the East Calcutta Wetland areas

Heavy metal exposure to a migratory waterfowl, Northern Pintail (Anas acuta), in two peri-urban wetlands

In this study, the heavy metal exposure risk model was employed to assess the exposure risk to a predominantly herbivore waterfowl, Northern Pintail, wintering in two wetland habitats in the Purulia district of West Bengal, located on overlapping Central Asian Flyway (CAF) and East Asian-Australasian Flyway (EAAF). Both wetlands were important staging and roosting grounds for migratory waterfowl for ages. The exposure model was used to quantify the risk of exposure to metals through oral ingestion. Exposure doses of Cu, Zn, Pb, and Cr through food plants ingestion and food-associated sediment consumption pathways were two potent sources of heavy metal exposure in the waterfowl under study. Exposure through water intake was ignored as metals were either of negligible concentrations or below the detection limit in water samples. Heavy metal concentrations showed significant positive correlations between bottom sediment and plant at both sites. At Purulia Sahebbandh (Site 1), the total exposure dose of all four metals was much higher than their conforming tolerable daily intake (TDI), and thereby, the metals might pose threats to the migratory wintering herbivorous waterfowl populations. However, in Adra Sahebbandh (Site 2), total exposure doses of Pb, Zn and Cu were much below their corresponding TDI. The Hazard Quotient (HQ) of Cr was highest followed by nonessential toxic Pb and these two elements could be considered as priority pollutants at Site 1. Prioritize threats were decreased in the following sequence: Cr > Pb > Cu > Zn at Site 1 and Cr > Zn > Pb > Cu at Site 2. Hazard Index was found to be >5 at Site 1 and for much higher metal loads a significant correlation between metal concentrations in plants, bottom sediment and exposure doses were also recorded. Therefore, the peri-urban Purulia Sahebbandh wetland could immediately be considered for risk control and demanded holistic management of important waterfowl habitats.

Assessment of the surface water quality improvement during pandemic lockdown in ecologically stressed Hooghly River(Ganges) Estuary, West Bengal, India

The countrywide COVID-19 pandemic lockdown accomplished what aggressive plans could not do throughout the long-term cleaning of the Ganga River. Here, we illustrated Hooghly River surface water quality [physico-chemical parameters, biological parameters, dissolved heavy metals] improvement by analyzing eight sampling station before and during the lockdown. Because of shutdown of industrial units and individuals staying at home, a complete decrease in industrial wastes, contaminants, and self-purging of the stream improved significantly water quality by about 40% to 50%. Among dissolved heavy metals, the concentrations of Cd (50%), Pb (53%), demonstrated noteworthy variations during the lockdown. Diminishing trends were also observed for TDS (62%), and BOD (52%), with significant reduction in the total coliform (63%), faecal coliform (61%), notably. Principal component analysis and paired t-test signify the alteration of water quality. The study concludes that the aquatic ecosystem can be revived if wastewater, and anthropogenic activities are properly managed by environmental surveillance.

Evaluation of metal contamination and phytoremediation potential of aquatic macrophytes of East Kolkata Wetlands, India

OBJECTIVES

The present study analyzes metal contamination in sediment of the East Kolkata Wetlands, a Ramsar site, which is receiving a huge amount of domestic and industrial wastewater from surrounding areas. The subsequent uptake and accumulation of metals in different macrophytes are also examined in regard to their phytoremediation potential.

METHODS

Metals like cadmium (Cd), copper (Cu), manganese (Mn), and lead (Pb) were estimated in sediment, water and different parts of the macrophytes Colocasia esculenta and Scirpus articulatus.

RESULTS

The concentration of metals in sediment were, from highest to lowest, Mn (205.0±65.5 mg/kg)>Cu (29.9±10.2 mg/kg)>Pb (22.7±10.3 mg/kg)>Cd (3.7±2.2 mg/kg). The phytoaccumulation tendency of these metals showed similar trends in both native aquatic macrophyte species. The rate of accumulation of metals in roots was higher than in shoots. There were strong positive correlations (p<0.001) between soil organic carbon (OC) percentage and Mn (r =0.771), and sediment OC percentage and Pb (r=0.832). Cation exchange capacity (CEC) also showed a positive correlation (p<0.001) with Cu (r=0.721), Mn (r=0.713), and Pb (r=0.788), while correlations between sediment OC percentage and Cu (r=0.628), sediment OC percentage and Cd (r=0.559), and CEC and Cd (r=0.625) were significant at the p<0.05 level.

CONCLUSIONS

Bioaccumulation factor and translocation factors of these two plants revealed that S. articulatus was comparatively more efficient for phytoremediation, whereas phytostabilization potential was higher in C. esculenta.

A study on the waste metal remediation using floriculture at East Calcutta Wetlands, a Ramsar site in India

Use of specific plant species in remediation of heavy metal-contaminated soil and water was a promising eco-friendly technology. The present study indicated the possibilities of phytoremediation of metal-contaminated (namely Ca, Cr, Mn, Fe, Cu, Zn, and Pb) soil by using plant species important for floriculture of East Calcutta Wetlands, a Ramsar site at the eastern fringe of Calcutta city. Plant species like sunflower (Helianthus annuus), marigold (Tagetes patula), and cock's comb (Celocia cristata) grew on soil contaminated by industrial sludge and irrigated regularly with wastewater accumulated different metals in different plant parts in varied concentrations. Pot culture study in the laboratory setup was also done to ascertain the efficiency of these plants for ameliorating contaminated soil. It was found that general accumulation patterns of metals concerned in different plant parts were root > leaf > stem > flower. This work indicated the importance of cultivation of economically important, non-edible, ornamental plant species as an alternative cost-effective practice to remediate heavily contaminated farmlands of East Calcutta Wetlands.