title: The Applicability of the Distribution Coefficient, KD, Based on Non-Aggregated Particulate Samples from Lakes with Low Suspended Solids Concentrations.
abstract: Separate phases of metal partitioning behaviour in freshwater lakes that receive varying degrees of atmospheric contamination and have low concentrations of suspended solids were investigated to determine the applicability of the distribution coefficient, KD. Concentrations of Pb, Ni, Co, Cu, Cd, Cr, Hg and Mn were determined using a combination of filtration methods, bulk sample collection and digestion and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Phytoplankton biomass, suspended solids concentrations and the organic content of the sediment were also analysed. By distinguishing between the phytoplankton and (inorganic) lake sediment, transient variations in KD were observed. Suspended solids concentrations over the 6-month sampling campaign showed no correlation with the KD (n = 15 for each metal, p > 0.05) for Mn (r2 = 0.0063), Cu (r2 = 0.0002, Cr (r2 = 0.021), Ni (r2 = 0.0023), Cd (r2 = 0.00001), Co (r2 = 0.096), Hg (r2 = 0.116) or Pb (r2 = 0.164). The results implied that colloidal matter had less opportunity to increase the dissolved (filter passing) fraction, which inhibited the spurious lowering of KD. The findings conform to the increasingly documented theory that the use of KD in modelling may mask true information on metal partitioning behaviour. The root mean square error of prediction between the directly measured total metal concentrations and those modelled based on the separate phase fractions were ± 3.40, 0.06, 0.02, 0.03, 0.44, 484.31, 80.97 and 0.1 μg/L for Pb, Cd, Mn, Cu, Hg, Ni, Cr and Co respectively. The magnitude of error suggests that the separate phase models for Mn and Cu can be used in distribution or partitioning models for these metals in lake water.
authors.affiliation: School of Environmental Sciences, University of Ulster, Coleraine, N. Ireland, BT52 1SA, United Kingdom; School of Applied Sciences, Cranfield University, Bedfordshire, MK43 0AL, United Kingdom.
authors.forename: Aine Marie
authors.initials: AM
authors.lastname: Gormley-Gallagher
authors.affiliation: School of Environmental Sciences, University of Ulster, Coleraine, N. Ireland, BT52 1SA, United Kingdom.
authors.forename: Richard William
authors.initials: RW
authors.lastname: Douglas
authors.affiliation: School of Environmental Sciences, University of Ulster, Coleraine, N. Ireland, BT52 1SA, United Kingdom.
authors.forename: Brian
authors.initials: B
authors.lastname: Rippey
mesh_terms: D018533:Biomass; D004784:Environmental Monitoring / Q000379:methods; D005374:Filtration / Q000379:methods; D019015:Geologic Sediments / Q000032:analysis*; D060106:Lakes / Q000737:chemistry*; D019216:Metals, Heavy / Q000032:analysis*; D008962:Models, Theoretical; D010839:Phytoplankton / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D019216:Metals, Heavy; D014874:Water Pollutants, Chemical