淡水河流域主要離子之濃度分布

Abstract

河川中之顆粒態與溶解態物質為河川向外海傳輸物質的主要方式，這些物質將會對周遭海域之海水化學組成有相當程度之影響。本研究藉由分析淡水河流域與蘭陽溪流域之主要離子含量，助以了解兩條東西向河川，傳輸至外海之主要離子濃度是否有其差異性。 研究結果顯示，就淡水河流域而言，新店溪溶解態之平均陽離子含量以Na+佔最高(53%)，Ca2++Mg2+次之(44％)，K+最低(3％)。陰離子含量較為平均，HCO3-佔40％，Cl-佔31％，SO42-佔29％。基隆河與大漢溪平均陽離子濃度也和新店溪類似，皆以Na+及Ca2++Mg2+含量為主，K+最低，陰離子含量較為平均。由結果可判斷出淡水河流域之岩石組成應以鋁矽酸鹽礦物居多。蘭陽溪流域部分，主支流溶解態之平均陽離子含量以Ca2++Mg2+比例佔最高(74％)，Na+次之(23％)，K+最低(3％)。陰離子含量以HCO3-比例佔最高(64％)，SO42-次之(32％)，Cl-最低(4％)。顯示出蘭陽溪流域主要離子以Ca2++Mg2+及HCO3-的組成比例較高，因此可判斷此流域之岩石組成以碳酸鹽礦物較為豐富。 總結而言，雖然發源地不同，所處之地質背景岩石組成結構不同，經風化作用後所溶出之主要離子含量也不盡相同。

Rivers and estuaries are the major source of suspended particles and dissolved loads exported into the ocean. These materials have considerable effect on marine chemistry of offshore areas. To understand the differences of dissolved loads between Danshuei and Lanyang rivers, both tributaries are originated from the Central Range, the concentrations of major ions of the two rivers are analyzed and compared. Of all the dissolved cations of Hsing-Dian stream, Na+ is the most abundant cation(53％), followed by Ca2++Mg2+(44％) and K+(3％). On the other hand, there is no distinct difference among the concentrations of anions, about 40％ of the anions is HCO3-, 31％ is Cl- and 29％ is SO42-. The concentrations of major ions in waters of Keelung River and Dai-Han stream are similar to those of Hsing-Dian stream. The results suggest that the bedrocks of the Danshuei River are mainly composed of aluminosilicate minerals. In Lanyang stream, Ca2++Mg2+ is the most abundant dissolved cation(74％), followed by Na+(23％) and K+(3％). On the other hand, dissolved HCO3- is the most abundant anion(64％)；SO42- is the second(32％) and Cl-(4％) is the least abundant anion. These differences are no doubtly due to the bedrocks of the Lanyang stream are abundant in carbonate minerals. In conclusion, although both Danshuei river and Lanyang stream originated from the Central Range, due to the difference in bedrock geology, the major ions released into rivers or streams are different as well.