Bioaccumulation of vanadium (V), niobium (Nb) and tantalum (Ta) in diverse mangroves of the Indian Sundarbans

Abstract

Vanadium (V), niobium (Nb), and tantalum (Ta), recognized as Technology-Critical Element (TCE), are highly growing in demand for industrial development. Despite their economic relevance, little is known about their environmental concentrations, especially in marine ecosystems like mangroves. This paper describes concentrations and distribution patterns of Group Va elements (V, Nb and Ta) in plant organs and sediments from diverse mangroves of the Indian Sundarbans. Sediment cores and plant organs of eight dominant mangrove species were sampled and analyzed for V, Nb and Ta by ICP-MS. Stable carbon isotope (δ13C) in mangrove leaves were analyzed by EA-IRMS. Mean concentrations (mg kg−1) of V, Nb and Ta decreased in the order V (84.7 ± 12.5) > Nb (37.5 ± 4) > Ta (3 ± 0.8) in the sediment and V (0.6 ± 0.6) > Nb (0.02) > Ta (0.002) in the mangrove plants. Species-specific variability in bioaccumulation factor (V: 0.012–0.035; Nb: 0.001–0.003; Ta: 0.001–0.005), translocation factor (V: 0.5–5.1; Nb: 0.26–7.06; Ta: 0.22–2.56) and enrichment factor (V: 0.008–0.027; Nb: 0.0002–0.001; Ta: 1.0 × 10−5-3.0 × 10−6) indicated different partitioning of Group Va elements within the plant organs and varying degree of mangrove uptake efficiency. Results showed a general decrease in V, Nb and Ta concentrations with their increasing atomic weight. Their total concentrations in plants were related to the degree of enrichment of substrate sediments. The phytoextraction capacity varied amongst mangrove species depending on their CO2 uptake efficiency. Given increased demand for TCEs, results may have important implications for bioremediation processes.