Dissolution rates of hydrated lime, Ca(OH) 2 in fresh, oligohaline, mesohaline and euhaline waters and its significance for liming of shrimp culture ponds

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This study aimed at assessing the dissolution rates of hydrated lime, Ca(OH)2 in fresh, oligohaline, mesohaline and euhaline waters and discussing its significance for liming of shrimp culture ponds. Appropriate volumes of seawater and distilled water were mixed to prepare oligohaline (1–4 g/L) and mesohaline waters (4–15 g/L). One gram of analytical grade calcium carbonate, CaCO3, or one gram of analytical grade calcium hydroxide, Ca(OH)2, were applied in 10-L gallons filled with seawater (39.9 g/L), 10.7 g/L, 4.2 g/L and distilled water (0.0 g/L). The final TA of water was significantly higher for Ca(OH)2 than for CaCO3 only at salinities 4.2 and 10.7 g/L. It was concluded that hydrated lime, Ca(OH)2 is a better liming option than agricultural limestone, CaCO3 for moderately saline, hard and/or buffered waters (−4.5 ≤ Langelier saturation index, LSI ≤ −0.7). In poorly saline, hard and/or buffered waters (LSI < −4.5), limestone and lime would increase water TA similarly. Neither limestone nor lime should be applied on highly saline, hard and/or buffered waters (LSI > −0.7) because a TA decrease is expected.