We investigated the effects of low molecular weight organic acids (LMWOAs) on pH value of coastal seawater in the Jiaozhou Bay, China. The results showed that the average concentration of total LMWOAs was 13.67±11.64 μmol/kg and LMWOAs contributed an average value of 1.50±1.41% in total alkalinity. High concentrations of LMWOAs had remarkable effects on lowering pH value of coastal seawater. Currently, CO2 SYS program is widely used for pH calculation of seawater. However, systematic error was remarkable in pH calculation of coastal seawater without considering organic acid alkalinity. In our study, a new piece of software was developed to calculate pH value of coastal seawater by separating organic acid alkalinity into two parts: LMWOA alkalinity and humic acid alkalinity in alkalinity definition equation. Compared to CO2SYS program, the pH data from our new software better matched to real pH value of coastal seawater. Therefore, new software could more exactly calculate pH value of costal seawater after considering effects of LMWOAs on the pH value of seawater. This study provided a new approach for further predicting changes of carbon dioxide system in the ocean and would also be helpful for studying ocean acidification, marine carbon cycle and global climate change.

New software for calculating pH value of coastal seawater: Considering the effects of low molecular weight organic acids

254th National Meeting (2017)

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