title: Aging of nickel added to soils as predicted by soil pH and time.
abstract: Although aging processes are important in risk assessment for metals in soils, the aging of Ni added to soils has not been studied in detail. In this study, after addition of water soluble Ni to soils, the changes over time in isotopic exchangeability, total concentrations and free Ni(2+) activity in soil pore water, were investigated in 16 European soils incubated outdoors for 18 months. The results showed that after Ni addition, concentrations of Ni in soil pore water and isotopic exchangeability of Ni in soils initially decreased rapidly. This phase was followed by further decreases in the parameters measured but these occurred at slower rates. Increasing soil pH increased the rate and extent of aging reactions. Semi-mechanistic models, based on Ni precipitation/nucleation on soil surfaces and micropore diffusion, were developed and calibrated. The initial fast processes, which were attributed to precipitation/nucleation, occurred over a short time (e.g. 1h), afterwards the slow processes were most likely controlled by micropore diffusion processes. The models were validated by comparing predicted and measured Ni aging in three additional, widely differing soils aged outdoors for periods up to 15 months in different conditions. These models could be used to scale ecotoxicological data generated in short-term studies to longer aging times.
authors.affiliation: Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China. ybma@caas.ac.cn
authors.forename: Yibing
authors.initials: Y
authors.lastname: Ma
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
authors.forename: Mike J
authors.initials: MJ
authors.lastname: McLaughlin
authors.forename: Ian W
authors.initials: IW
authors.lastname: Oliver
authors.forename: Annette L
authors.initials: AL
authors.lastname: Nolan
authors.forename: Koen
authors.initials: K
authors.lastname: Oorts
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
mesh_terms: D001315:Australia; D004058:Diffusion; D004784:Environmental Monitoring / Q000379:methods*; D005060:Europe; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D009532:Nickel / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D013997:Time Factors
chemical_list: D012987:Soil; D012989:Soil Pollutants; D009532:Nickel
keywords: Aging; E value; Labile metal; Nickel; Soil