Hydrochemical fluxes and bedrock chemistry in three contrasting catchments underlain by felsic, mafic and ultramafic rocks

Abstract

Bedrock chemistry from three drill cores and fluxes of precipitation, throughfall and runoff from the 2015 water year were examined in three forested catchments in the western Czech Republic. The coefficient of alkalinity of rocks at the granitic (felsic) LYS catchment fall in the low chemical reactivity category. Rocks from the amphibolitic (mafic) NAZ catchment have high reactivity and rocks from the serpentinitic (mostly ultramafic) PLB catchment have high or even very high reactivity. Streamwater fluxes reflected the composition of the underlying bedrock lithologies, especially for magnesium, nickel and chromium at PLB, and for calcium, arsenic and sulfur at NAZ. Streamwater at LYS reflected incomplete neutralization of acidic deposition in the catchment and had mostly negative alkalinity and correspondingly very high fluxes of potentially toxic inorganic monomeric aluminum. Internal cycling of magnesium and calcium in spruce canopy throughfall was influenced by substrate chemistry at PLB and NAZ. About half of streamwater nitrogen left the catchments in the organic form