Role of salinity in the dissolution rates of CaCO 3 and its implications for aquaculture liming

This work aimed at assessing the role of salinity in the dissolution rates of CaCO 3 , discussing its implications for aquaculture liming. A simplified formula of artificial seawater without HCO 3 − was initially prepared. Four batches of 10 L of diluted artificial seawater (salinity = 3.3 g/L) without HCO 3 − were prepared. Sixteen Erlenmeyer flasks were filled up with 2 L each of the diluted artificial seawater without HCO 3 − . Besides, 16 other 2,000‐ml Erlenmeyer flasks were filled up with 2 L of distilled water (freshwater). The experimental treatments were formed by applying increasing amounts of analytical‐grade sodium bicarbonate (NaHCO 3 ) upon brackish water and freshwater. Accordingly, four initial levels of total alkalinity (TA) have been set up as follows: 4–6, 33–35, 62–63 and 120–122 mg/L. Next, approximately one gram of analytical‐grade calcium carbonate (CaCO 3 ) was applied onto each flask. Water's pH, TA and calcium concentration were determined weekly over a 7‐week period, by appropriate methods. For a same initial TA, TA increase over time after CaCO 3 application was lower in the brackish water flasks than in the freshwater ones. This was especially clear for moderate (63 mg/L) and high (120 mg/L) alkalinities. It was concluded that brackish and saline waters used for aquaculture would only benefit from CaCO 3 liming if their alkalinities were lower than 60–80 mg/L.