Abstract

This study was carried to investigate the impact of land pollution on bacteriological water quality in the shellfish growing area northern sea of Samcheok, Korea, after rainfall. Eight stations (L1-L8) for sampling of land pollution source (fresh water) and 11 stations (S1-S11) for sampling of seawater at shellfish growing area were selected and cell numbers of coliform group and fecal coliform were investigated at a day before rainfall, and 1st day, 3rd day and 5th day after rainfall. At a day before the rainfall, the range of amount of discharged water, cell numbers of fecal coliform and radius of half-circle were 4-2,410 L/min, 49-54,000 MPN/100 mL and 8-93 m, respectively. At 1st day after the rainfall, amount of discharged water, cell numbers of fecal coliform and radius of half-circle were 9-3,388 L/min, 170-1,700 MPN/100 mL and 10-98 m, respectively. The radius of half-circle of at 1st day after the rainfall was broader than that of at a day before the rainfall due to increased amount of discharged water although cell numbers of fecal coliform of at 1st day after the rainfall was fewer than that of at a day before the rainfall. At 3rd day after the rainfall, the range of amount of discharged water, cell numbers of fecal coliform and radius of half-circle were 5-2,704 L/min, 94-35,000 MPN/100 mL, and 6-87 m, respectively. The radius of half-circle of at 3rd day after the rainfall was decreased compare to that of at 1st day after the rainfall due to decreased amount of discharged water although cell numbers of fecal coliform of at 3rd day after the rainfall was higher than that of at 1st day after the rainfall. At 5th day after the rainfall, amount of discharged water, the number of fecal coliform, and radius of half-circle were 5-2,475 L/min, 49-22,000 MPN/100 mL and 5-65 m, respectively, and recovered to the level at a day before the rainfall. The range of cell numbers of fecal coliform at a day before the rainfall, 1st day, 3rd day and 5th day after the rainfall at S1 to S11 in shellfish growing area were <1.8-2.0 MPN/100 mL, <1.8-4.5 MPN/100 mL, <1.8-6.8 MPN/100 mL and <1.8-2.0 MPN/100 mL, respectively. On the other hand, the amount of discharged water at station L7 and L8 of land pollution source were increased 2,310 L/min at a day before the rainfall to 3,388 L/min at 1st day after the rainfall, and 4 L/min a day before the rainfall to 9 L/min at 1st day after the rainfall, respectively. The range of cell numbers of fecal coliform at S7, S8 and S11 where are adjacent to station L7 and L8 of land pollution source were increased <1.8-2.0 MPN/100 mL at a day before the rainfall to <1.8-4.5 MPN/100 mL at 1st day after the rainfall due to increased amount of discharged water at station L7 and L8 of land pollution source at 1st day after the rainfall. In addition, The cell numbers of fecal coliform at S11 was increased <1.8 MPN/100 mL 1st day after the rainfall to 6.8 MPN/100 mL at 3rd day after the rainfall due to increased cell numbers of fecal coliform at station L8 whose cell numbers of fecal coliform was increased 1,400 MPN/100 mL at 1st day after the rainfall to 35,000 MPN/100 mL at 3rd day after the rainfall. From above results, the bacteriological quality of sea water in the shellfish growing area at northern sea area of Samcheok was affected mostly by amount of discharge water of land pollution source, and the cell number of fecal coliform of land pollution source was followed. However, the bacteriological quality of sea water in the shellfish growing area at northern sea area of Samcheok was not significantly affected by land pollution source after rainfall and the shellfish growing area at northern sea area of Samcheok was maintained the level of Approved area by KSSP standard. The results in this study were obtained by just an investigation with short-term of an week, and more study about effects of land pollution source (amount of rainfall and study period) should be needed to understand concretely the impact of land pollution on the bacteriological quality of sea water in the shellfish growing area at northern sea area of Samcheok.