광주지역 하천수와 하수처리장 방류수를 대상으로 유기물 분포 특성과 분해 특성을 파악하고자 하였다. 영산강 수계에서 TOC에서 DOC가 차지하는 비율은 평균 73.9% 정도를 보였다. DOC중 RDOC의 평균 농도는 3.7 mg/L였으며, 비율은 80.9%로 나타나 생분해성유기물에 비해 난분해성유기물의 비율이 높은 것으로 나타났다. 유기물 오염도 지표간 산화율을 비교한 결과 하천수에서는 BOD-C/TOC는 45.0%, $COD_{Mn}$-C/TOC는 63.0%, CODcr-C/TOC는 106.5%로 나타났다. 하수처리장 방류수의 경우는 각각 33.6%, 65.7%, 136.1%로 나타나 하천수에 비해 BOD의 산화율이 낮았다. 하천수 중의 DOC의 평균 분해속도($K_d$)는 영산강 본류에서 $0.042;day^{-1}$, 지류하천에서 $0.043;day^{-1}$로 조사되었으며 본류구간과 지류하천간에 유의적인 차이는 없었다(p>0.05). 하수처리장 방류수에서는 $K_d$가 $0.028;day^{-1}$로 하천수에 비해 낮은 분해속도를 나타냈다.
This study was performed to investigate the distribution and decomposition characteristics of organic matter in stream water and sewage effluent located in Gwangju. Average of dissolved organic carbon (DOC) to total organic carbon (TOC) ratio was approximately 73.9% in the Youngsan river system. The concentration of refractory dossolved carbon (RDOC) was 3.7 mg/L corresponding to 80.9% of the DOC. The ratio of recalcitrant organic carbon was relatively higher than that of biodegradable organic carbon in stream. Oxidation efficiencies in the stream were 45.0% for BOD, 63.0% for $COD_{Mn}$ and 106.5% for CODcr. In case of sewage effluent was 33.6%, 65.7% and 136.1% respectively. Mean decomposition rate ($K_d$) of Youngsan river mainstream, its tributary sites and sewage effluent were about $0.042;day^{-1}$, $0.043;day^{-1}$ and $0.028;day^{-1}$, respectively and the difference was not significant between the mainstream and its tributary sites (t-test, p>0.05). $K_d$ of the sewage effluent was lower than that of stream water.
