Seasonal and spatial variations in water chemistry and nitrate sources in six major Korean rivers

摘要

Seasonal and spatial variations in water chemistry and contaminant sources were investigated in six major rivers in South Korea that vary widely in drainage area and length. The dissolved-load content of the rivers varied seasonally, and some dissolved ions such as Cl~- and NO_3~- showed large spatial differences in all of the rivers. The water type changed from Ca-HCO_3 in the upper reaches to Na-Cl-NO_3 in the lower reaches, indicating anthropogenic contamination in the lower reaches. Compared with two relatively pristine rivers (the Sumjin and Mankyung rivers), the other four rivers, which flow through agricultural and urban areas, registered much higher Cl~-and NO_3~- concentrations. Statistical analysis showed that seasonal and spatial variations in water chemistry occurred in all the rivers. The nitrogen and oxygen isotopes of dissolved nitrate indicated that the rivers flowing through urban and agricultural areas were significantly affected by manure, sewage, or both.