국내 담수퇴적물의 CODsed 분석방법 평가: CODMn법과 CODCr법의 신뢰성 및 상관성 비교

In Korea, the chemical oxygen demand(COD(sed)) in freshwater sediments has been measured by the potassium permanganate method used for marine sediment because of the absence of authorized analytical method. However, this method has not been fully verified for the freshwater sediment. Therefore, the use or modification of the potassium permanganate method or the development of the new COD(sed) analytical method may be necessary. In this study, two modified COD(sed) analytical methods such as the modified potassium permanganate method for COD(Mn) and the modified closed reflux method using potassium dichromate for COD(Cr) were compared. In the preliminary experiment to estimate the capability of the two oxidants for glucose oxidation, COD(Mn) and COD(Cr) were about 70% and 100% of theoretical oxygen demand(ThOD), respectively, indicating that COD(Cr) was very close to the ThOD. The effective titration ranges in COD(Mn) and COD(Cr) were 3.2 to 7.5 mL and 1.0 to 5.0 mL for glucose, 4.3 to 7.5 mL and 1.4 to 4.3 mL for lake sediment, and 2.5 to 5.8 mL and 3.6 to 4.5 mL for river sediment, respectively, within 10% errors. For estimating COD(sed) recovery(%) in glucose-spiked sediment after aging for 1 day, the mass balances of the COD(Mn) and COD(Cr) among glucose, sediments and glucose-spiked sediments were compared. The recoveries of COD(Mn) and COD(Cr) were 78% and 78% in glucose-spiked river sediments, 91% and 86% in glucose-spiked lake sediments, 97% and 104% in glucose-spiked sand, and 134% and 107% in glucose-spiked clay, respectively. In conclusion, both methods have high confidence levels in terms of analytical methodology but show significant different COD(sed) concentrations due to difference in the oxidation powers of the oxidants.