Chemical Speciation and Toxicity of Nickel Species in Natural Waters from the Sudbury Area (Canada)

Abstract

Metal complexation properties of dissolved organic carbon (DOC) in freshwaters are recognized but poorly understood. Here, we investigated the release of free nickel from Ni-DOC complexes using nickel-polluted freshwaters from Sudbury (Canada). We used the Competing Ligand Exchange Method with Chelex-100 as the competing ligand to measure the rate of free Ni2+ ion released by the dissociation of Ni-DOC complexes. The kinetic studies showed that the fastest kinetically distinguishable component representing approximately 30-95% of the total nickel had a dissociation rate coefficient similar to that reported for [Ni(H20)6]2+. High concentrations of Ca2+ and Mg2+ caused a larger amount of the DOC-bound nickel to be released as free Ni2+ ion. Growth inhibition of the freshwater alga Pseudokirchneriella subcapitata was highly correlated with the Ni/DOC ratio, the free plus labile nickel concentration, and the dissociation rate coefficient. While the levels of metals were not sufficient to kill Daphnia magna, these test organisms were immobilized in the same samples that showed algal growth inhibition. Only one sample caused 22% death of Hydra attenuata. The algal toxicity tests were consistent with the kinetic speciation results and are consistent with the hypothesis that dissolved [Ni(H20)6]2+ plus other labile nickel species are toxic forms of Ni present.

SunCHem: an integrated process for the hydrothermal production of methane from microalgae and CO2 mitigation

“…This is in line with the literature reports showing the toxic effects of nickel on microalgae at micromolar levels (Mandal et al 2002).…”

“…It has been previously reported that at micromolar levels nickel is toxic to a variety of algae, invertebrates, and fish (Mandal et al 2002;Nriagu 1980;Bielmyer et al 2006). Several studies exist on the toxicity of nickel to algae and on the bioconcentration of nickel by brown algae and by cyanobacteria and green algae (Wang and Wood 1984;Bordons and Jafre 1987;Wong et al 2000).…”

“…Exposure of various species of microalgae to nickel was shown to negatively affect cell division resulting in reduced growth rates (Nriagu 1980). A review of the literature showed that nickel toxicity seems to be related to its concentration, speciation, presence of competing ions, but also on the type and physiological characteristics of microalgae (Fezy et al 1979;Spencer and Greene 1981;Lustigman et al 1995;Mandal et al 2002). However, the results reported in the literature on nickel toxicity are inconsistent due to variability in culture conditions.…”

Speciation of nickel in surface waters measured with the Donnan membrane technique

“…Some studies [6][7] used to study Ni speciation. However, in these studies [8][9][10], no attempt was made to 65 measure equilibrium speciation, but information on the lability of the Ni-DOM complexes in 66 surface waters was derived from the rate of dissociation. Fractions of labile Ni in surface 67…”

“…water were found to range from 20 to 80% [8], 40 to 100% [9] and 31 to 88% [10]. The labile 68 fractions are assumed to include free Ni 2+ ion, inorganic Ni complexes and small Ni-DOM 69 complexes that dissociate within the operational conditions.…”