한국의 강을 통한 탄소 유출

Abstract

Since the Industrial Revolution, atmospheric CO2 concentration has rapidly increased and this trend is expected to continue in this century, thus, many scientists focus on the global carbon cycles. Rivers play an important role as a connector of the two carbon storage, land and ocean. Although the absolute amount of carbon transported by rivers is relatively small compared to the other carbon pools and fluxes, it is comparable to the amount of Net Ecosystem Production (NEP). The objectives of this study are to quantify riverine carbon exports (loads and yields) of the 5 major rivers (the Han River, Nakdong River, Geum River, Youngsan River, and Sumjin River) in Korea and to understand what factors influence the riverine carbon exports. The water quality data such as total organic carbon (TOC) concentration and riverine discharge data collected from 30 water stations were used. Also, water samples were collected in the lower reaches of each river from February 2012 to October 2012. The concentration of dissolved organic carbon (DOC), alkalinity, and pH were measured in laboratory. Temporally, the TOC concentration was at the highest in summer, followed by spring, fall, and winter. Spatially, the TOC concentration was the largest in the Geum River. TOC yields ranged approximately 0.02~6.6 g m-2 yr-1 in the entire watersheds of the 5 major rivers. The amount of carbon released from watersheds was influenced by precipitation, land-use (urban, agriculture, and forest), and soil characteristics. The riverine carbon exports were positively correlated with precipitation and the percentages covered by urban or agricultural land use, and negatively correlated with the percentage covered by forests. DIC is the dominant form of carbon that was released by the 5 major rivers. DIC yield was 8.2 g m-2 yr-1, and DOC and POC accounted for approximately 24.5% of total carbon yield, 1.8 g m-2 yr-1, and 0.9 g m-2 yr-1, respectively. In sum, these rivers released 499 Gg C to the ocean annually. However, the data of North Han River and downstream of South Han River watersheds were not included in the study, and particulate inorganic carbon (PIC) was excluded. Thus, it is expected that more than 499 Gg carbon is annually exported by rivers to the ocean.