Weathering rates in the Hietajärvi Integrated Monitoring catchment

Rates of Ca and Mg release by weathering were calculated for four soil profiles (Haplic Podzols) in a small forested catchment in eastern Finland (63°10´N, 30°43´E). Three of the profiles were developed on glacifluvial fine sand and one on till, and all derived from granodiorites. Soil weathering rates (mmolc m–2 a–1) were calculated using three methods: Zr depletion, Ca + Mg\temperature sum regression, and the PROFILE model. The first two methods give long-term average rates while the latter gives the current rate. According to the Zr depletion method, the weathering rate of Ca was 7–32 (mean = 19) and that of Mg, 3–16 (mean = 9). According to the regression method, the weathering rate of Ca was 14–19 (mean = 15) and that of Mg, 5–9 (mean = 7). The mean values using the PROFILE model were 10 (Ca) and 3 (Mg). Values were corrected for stone content. Catchment input-output budgets gave values of 18 (Ca) and 8 (Mg).