Nickel diagenesis and partitioning in lake sediments

Arsenic transport between water and sediments

“…Below the mixed layer, the Pb-210 concentrations decline continuously with depth and suggest that the accumulation of Pb-210 and sediment has been continuous . This is further supported by measurements of stable Pb in the cores (Evans et al, 1986) and the analysis of the bulk composition of sediments which is quite uniform with depth in all cores except in core 10 (Cornett et al, 1989). The fluctuations in the Pb-210 exhibit a subsurface maximum and then rapidly decrease (Fig .…”

“…Records suggest that the amount of As entering the lake has decreased since refining operations ceased in 1961 (Ontario Ministry of the Environment, unpublished data) . The surficial concentrations of many trace metals in Moira River sediments and in the lake sediments are higher than background levels and there are significant enrichments of As, Ni and Co (Mudroch & Capobianco, 1980 ;Cornett et al, 1989).…”

“…As an additional precaution against the intrusion of oxygen, the outer ring of core material (0 .5 cm) was separated from the inner ring of each section and the outer ring was not used for redox sensitive analyses . During subsequent sample processing for redox sensitive parameters, a nitrogen atmosphere was always maintained over the samples (see Cornett et al, 1989). Subsamples of sediment were extracted using the sequential extraction procedure of Tessier et al (1979) using the modifications described by Cornett et al (1989) to prevent the intrusion of oxygen .…”

“…During subsequent sample processing for redox sensitive parameters, a nitrogen atmosphere was always maintained over the samples (see Cornett et al, 1989). Subsamples of sediment were extracted using the sequential extraction procedure of Tessier et al (1979) using the modifications described by Cornett et al (1989) to prevent the intrusion of oxygen . The porewaters were separated from the matrix by low speed centrifugation under a nitrogen atmosphere in a glove box .…”

“…In this paper we examine the distribution, fluxes and fate of one trace contaminant, arsenic, in Moira Lake, a small hardwater lake that has received discharges from tailings and milling operations during the past century (Mudroch & Capobianco, 1980 ;Evans et al, 1986 ;Cornett et al, 1989). We have used these measurements to determine the historical chronology of arsenic inputs to the sediments, to determine the mobility of arsenic within the sediments, to construct a mass balance for arsenic in the lake and to test the hypothesis that the internal loading of arsenic from the lake sediments into the water column is, currently, greater than the external loading .…”