Nitrogen budgets for the Republic of Korea and the Yellow Sea region

Growing populations in northeast Asia have greatly altered the nitrogen cycle, with increases in agricultural production to feed the Population, and with increases in N emissions and transboundary air pollution. For example, during the 1900's over 50% of the N deposition over Republic of Korea was imported from abroad. In this paper, we present biogeochemical budgets of N for the South Korean peninsula (the Republic of Korea) and for the Yellow Sea region. We quantify N inputs from atmospheric deposition, fertilizers, biological fixation, and imports of food, feed, and products. We quantify outputs in riverine export, crop uptake, denitrification, volatilization, runoff, sedimentation and sea water exchange. Calculations were conducted using mean values from 1994-1997. All of the nitrogen budgets were positive, with N inputs exceeding outputs. The excess N inputs gave rise to increases in N storage in landfills and in groundwater. Annual accumulation of N in the Yellow sea, including inputs from South Korea and other drainage areas, was 1229 kt yr(-1) with a residence time for N of approximately 1.5 years, thus doubling N content in marine waters every 3 years during 1994-1997. The human derived N inputs leads to excessive eutrophication and pollution of the Yellow Sea.