Trends in sulfate, base cations and H+ concentrations in bulk precipitation and throughfall at integrated monitoring sites in Finland 1989-1995

摘要

Temporal trends in sulfate, base cation (Ca2+ + Mg2+ + K+), and H+ ion concentrations in bulk precipitation and throughfall samples collected over a seven year period (1989-95) in four forested catchments in Finland are presented. The catchments are in remote locations and span the boreal zone (61-69 degrees N). The stands represent old, undisturbed forests, and are composed of varying proportions of Scots pine, Norway spruce and deciduous species (mainly Betula spp.). Monthly SO42--S and H+ ion concentrations in bulk precipitation averaged over the study period and catchments were: 18.7 mu mol L-1 and 32.3 mu mol L-1. The corresponding values for throughfall were: 37.4 mu mol L-1 and 32.4 mu mol L-1. Sulfate and H+ ion concentrations in bulk precipitation and throughfall both showed negative linear trends, which were significant (p 0.05). It is concluded that the reported reduction in S emissions over the study period has resulted in a significant reduction in the acidity and SO42- concentration of bulk precipitation, and this reduction has has been reflected in throughfall concentrations. The greatest reduction has taken place in the southern part of the country. References: 25