Vanadium Stable Isotopes in Biota of Terrestrial and Aquatic Food Chains

Abstract

Vanadium, a potentially toxic metal, is enriched in the environment from anthropogenic releases, particularly during fossil fuel production and use and steel manufacturing. Metal stable isotopes are sophisticated tools to trace pollution; however, only recent analytical advances have allowed for the accurate and precise measurement of vanadium isotope ratios (δ51V). To examine its potential as a tracer in terrestrial and aquatic ecosystems, δ51V was measured in soil, plant, lichen, marten, and lake sediment from sites near vanadium emissions at oil sands mines (Alberta, Canada) and in the sediment and biota (algae, zooplankton, fish) from a remote subarctic lake (Northwest Territories, Canada). Samples from Alberta had distinct δ51V values with marten liver the lowest (−1.7 ± 0.3‰), followed by lichen (−0.9 ± 0.1‰), soil (−0.7 ± 0.1‰), sediment (−0.5 ± 0.2‰), and plant root (−0.3 ± 0.2‰). Average values were lower than Alberta bitumen and petroleum coke (−0.1 ± 0.1‰). Plant roots had systematically higher δ51V than the soil from which they grew (Δ51Vplant‑soil = 0.4 ± 0.1‰), while δ51V of lichen and aquatic biota were lower (0.1–0.3‰) than likely crustal sources. These δ51V measurements in terrestrial and aquatic biota demonstrate promise for tracer applications, although further study of its biological fractionation is needed.

Theoretical and Experimental Study on Vanadium Isotope Fractionation among Species Relevant to Geochemistry

“…River sediment samples show negative δ 51 V of −0.5 to −1.7‰. 11 Schuth et al also reported δ 51 V = −0.1 to −0.76‰ for river water samples. 10 The industrially released V migrates in soils by weathering and creates −0.67 to −0.52‰ δ 51 V. 10 These isotopic variations could be explained by considering the calculated ln β for V(III) and V(IV) hydroxides (Figures 2b and 3b,c and Tables 2 and 3).…”

“…This may be a potential cause of the negative δ 51 V found in the aquatic food chain. 11 Since the functional groups of amino acids are categorized into O-, N-, and S-donors, 77 complexation of V with carboxylate ions may be helpful to understand the V isotope fractionation in the complexation of V with O-donor amino acids. Molecules of V(IV) oxalates are computed, and their optimized structures are shown in Figure 3o,p, and their ln β values are shown in Table 4.…”

“…For example, plant roots are ∼0.4‰ heavier than the soil from which they grew and are more than 1‰ heavier compared to animal organs. 11 However, there is presently only a limited theoretical framework 7 to assess the isotopic fractionation occurring during these processes. Although the kinetic isotope fractionation 14 occurs naturally, it is important to evaluate isotope fractionations under chemical equilibrium to gain a deeper understanding of V isotope geochemistry.…”

Nickel Isotope Fractionation As an Indicator of Ni Sulfide Precipitation Associated with Microbially Mediated Sulfate Reduction

“…Parallel batch tests using the same conditions as adopted in the main experiment were conducted to evaluate the bacterial viability. After the exposure of SRB to the various Ni concentrations (10,15,20,25,30, and 40 mM) at the selected time intervals (1 h, 1 day, and 1 week), 1 mL of solution was injected into a fresh Postgate B medium to assess the toxicity of Ni to the microorganisms. The SRB viability was assessed by biomass production (turbidity), and inhibition of SRB growth was assessed by relatively lower (or absent) turbidity.…”

“…Metal-stable isotope analysis has become a valuable tool in the field of environmental geochemistry with applications focusing on tracing the source and cycling of metals in the environment. − …”