科研之友
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摘要
The Duman River and the hot springs and streams of Mt. Baekdu were sampled and analyzed for their major elements, (87)Sr/(86)Sr, delta D, delta(18)O, and delta(13)C. The Duman River drains an extensive volcanic plateau in northeast Asia and Mt Baekdu is a volcanic cone on the plateau, and their fluvial geochemistry reflects weathering of volcanic rock. Two different volcanic end-members could be distinguished-basalt and trachyte. Weathering of trachytic rock is characterized by lower Ca/TZ(+) and higher (87)Sr/(86)Sr (>0.7082), while that of basaltic rock contributes higher Ca/TZ(+) and lower (87)Sr/(86)Sr (<0.7050). Carbon isotope analyses (delta(13)C of dissolved inorganic carbon. dissolved organic carbon and particulate organic carbon) along with chemical variations of major elements in the main channel suggest a transition from volcanic rock weathering in the upper reach to carbonate weathering in the lower reach. The (87)Sr/(86)Sr ratio was useful in discerning minor input from granitoid rocks in the lower reach. According to the delta D-delta(18)O data, the source of the river water in August is mostly precipitation supplied from the East Sea/Japan Sea related to the summer monsoon of East Asia. The natural CO(2) uptake rate is estimated to be 22.2 similar to 27.8 x 10(4) mol.km(-2).yr(-1). This is on the lower end of other basaltic regions of the world and is due to lower temperature and runoff and to lack of glaciation. The hot spring samples of Mt Baekdu have high TDS (total dissolved solids, 381 -1431 mg/L) and are of Na-HCO(3) type. Geothermometric calculations and delta D-delta(18)O data indicate that meteoric water infiltrates into the geothermal field but emerges at the surface before attaining equilibrium with the host rock. The hot spring samples affect the chemistry of nearby freshwater streams but are chemically distinct from the Duman River.
- 出版日期2009-6-30
