PNNL

Abstract

Nickel (Ni) is a bio-essential trace metal that is required for several geochemically relevant metabolisms. These include the cellular defense mechanism against reactive oxygen species, the production of ammonia from urea, the interconversion of di-hydrogen and protons, and the microbially mediated production of greenhouse gasses such as methane and carbon monoxide (Ragsdale, 2009). Nickel concentrations are low in the modern ocean with a range from 2 to 12 nM, and aqueous Ni shows a nutrient-like distribution with water depth due to depletion in the photic zone as a result of biological uptake (Sclater et al., 1976; Bruland et al., 2013). However, elevated concentrations up to 2 mM can be found in streams draining nickel-bearing minerals such as pyrite (FeS2) and millerite (trigonal NiS), as well as streams receiving industrial and mining wastes (reviewed in Rinklebe and Shaheen, 2017). High concentrations of Ni can adversely affect human health and the ecosystem; therefore, the World Health Organization recommended an upper limit of 0.001 mM (1 mM) for Ni concentrations in drinking water (WHO, 2007). Consequently, the removal mechanism of aqueous Ni from natural waters is of great interest both in terms of improving understanding of natural biogeochemical processes and in applying that information to improve water treatment quality.