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CALCIUM (Ca 2 + ) DETERIORATION UNDER THE
SUBSURFACE RUNOFF IN A FORESTED HEADWATER
CATCHMENT
KASDI SUBAGYONO ∗,‡ , TADASHI TANAKA and MAKI TSUJIMURA
Center for Soil and Agroclimate Research and Development
Jl. Ir. H. Juanda, 98 Bogor 16123, Indonesia
Graduate School of Life and Environmental Sciences, University of Tsukuba
Ibaraki 305-8572, Japan
kasdi s@yahoo.com
The present study deals with the nature of Ca 2+ under both weathering and
transport processes in Kawakami forested headwater catchment, central Japan.
The study showed that Ca 2+ deterioration is prominently occurred from which
the subsurface runoff governing transport of Ca 2+ is dominance, the process
by which the Ca 2+ is leached out. Shallow riparian groundwater (near surface
riparian) is the most dominant source area which releases much concentration
of Ca 2+ .TherateofCa 2+ leach out from this source area has been estimated
about 5.5 mg Ca 2+ ha/day (or 0.002 kg Ca 2+ /ha/year). Ca 2+ deterioration
was much obvious when the input through weathering is lower to that of the
output through the transport process.
1. Introduction
Insucient rate of weathering with respect to the rate of transport under
the subsurface runoff may create Ca 2+ to deteriorate in a forested headwa-
tercatchment.Yet,thestudyonCa 2+ balance between one created from
weathering and its loss through transport process is somewhat rare.
Ca 2+ may deteriorate through several processes in the soil such as
leaching 1 - 3 and vegetation uptake. 3 Mulholland et al. 4 reported that
exports of most solutes (includes Ca 2+ ) from the watershed exceeded pre-
cipitation inputs leading to a negative balance of Ca 2+ in the soil. Ca 2+ is
dominant chemical mixture in the stream channel and it was the product
of weathering in the catchment studied. 5
The present study is focused to (a) elucidate the relationship between
hydrologic flowpath and Ca 2+ pathway, (b) assess Ca 2+ transport with
respect to its weathering, and (c) assess the Ca 2+ depletion rate within
headwater catchment.
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