Recent organic matter accumulation in relation to some climatic factors in ombrotrophic peat bogs near heavy metal emission sources in Finland

Accumulation of organic matter (OM) was studied in four ombrotrophic peat bogs in Finland: Haijavalta. (vicinity of a Cu-Ni smelter), Outok-umpu (near a closed Cu-Ni mine), Alkkia (Ni-treated site) and Hietajarvi (a pristine site). At each sampling site, two peat cores (15 x 15 x 100 cm) were taken. Age-dating of peat was determined using Pb-210\ method (CRS model). The local annual temperature sum and precipitation for the past 125 years were modeled. The objective was to compare recent net accumulation rates of heavy metal polluted ombrotrophic peat bogs with those of a pristine bog, and to study the relationship between weather and net accumulation rates. Based on Pb-210 age-dating, the upper 16-cm peat layer at Harjavalta, 35 cm at Outokumpu and 25 cm at Hietajarvi represents 125 years of peat formation, yielding the following average peat accumulation rates: Harjavalta 1.3 mm year(-1), Outokumpu 2.8 mm year(-1) and Hietajarvi 2.0 mm year(-1). At the Alkkia site, the Ni treatment in 1962 had completely stopped the peat accumulation. Net accumulation rates were related to precipitation at Outokumpu, Harjavalta and Hietajarvi sites. In addition, emissions released from the nearby located Cu-Ni smelter could have affected negatively net OM accumulation rate at Harjavalta site. (C) 2006 Elsevier B.V. All rights reserved.