| In two Czech catchments covered by Norway spruce forests, the MAGIC model was
used to simulate annual stream water and soil chemistry for the period 1851–2030. These
two sites represent geochemical end-members of ecosystem sensitivity to acidification
(acid-sensitive granitic Lysina catchment vs. acid-resistant serpentinitic Pluhuv Bor
catchment). Although the total deposition of sulphur to the catchments declined by 75%
between 1990 and 2002, the recovery of stream water pH was relatively small over this
period. At Lysina, the annual discharge-weighted mean pH of stream water increased only
from 3.92 to 4.01, although SO4 concentration declined very sharply from
570 μeq L–1 in 1990 to 150 μeq L–1 in 2002. Stream
water buffering was caused mainly by
dissociation of organic acids. At Pluhuv Bor, the annual mean pH varied inversely with
the annual discharge. Stream water concentrations of SO4 declined dramatically
at Pluhuv Bor, from 1040 μeq L–1 in 1992 to 220 μeq L–1
in 2002. Using atmospheric
deposition as specified in the Gothenburg Protocol, the model predicts that, at Lysina,
stream water pH will increase to 4.3 and soil base saturation will increase to 6.0% by
2030 (from 5.6% in 2002); corresponding pre-industrial stream water pH was simulated
to be 5.5 and soil base saturation to be 25%. At Pluhuv Bor, the pre-industrial pH
was estimated to be 7.2 and the corresponding base saturation was 94%. Large
anthropogenic acidification in the 20th century caused only a small decline in pH
(to 6.9) and base saturation (to 88%). Simulations in accordance with the Gothenburg
Protocol predict that the pH should increase by 0.2 pH units and the base saturation
by 1% by 2030. Under this protocol, critical loads of atmospheric deposition for
SO4 and NO3 will not be exceeded at Pluhuv Bor but will be
exceeded at Lysina.
Keywords: MAGIC model, catchment, critical loads, Gothenburg Protocol, soil and water
acidification, granite, serpentinite, Czech Republic |