물 교환이 제한적인 시화호 상류 기수역의 부영양화

초록

To understand eutrophication in the upper regions of brackish Lake Sihwa with a limited water exchange, temporal and spatial distributions of pollutants in water and sediment were investigated from March to October in 2005 and 2006. Also, pollution levels of water and sediment were estimated by trophic state index (TSI) and sediment quality guideline (SQG). Total nitrogen (TN), total phosphorus (TP), organic matter (COD), and chlorophyll a (Chl-a) concentrations in the surface waters were largely varied temporally and spatially, and the variations were highest in the middle areas where strong halocline was formed. Chl-a concentrations in the middle area were very high in April (¤900 μgL-1) when algal blooms (red tides) occurred. The relationships between TN and Chl-a (r=0.31), and TP and Chl-a (r=0.65) indicated that the algal growth was primarily affected by phosphorus rather than nitrogen. The distribution of COD was similar to that of Chl-a, indicating that the autochthonous organic matters may be a more important carbon source, especially in the middle areas. The brackish water regions were classified as eutrophic or hypertrophic based on their TSI values (69~76). In addition, the content of nutrients (especially TP) in surface sediments were classified as severe polluted state, except the upper areas. Major causes of the eutrophication observed were probably due to high nutrients loading from watersheds, the phosphorus release from anaerobic sediment, and long retention time by the limited water exchange through the sluice gates.

키워드