Densities of Huanghe River estuary and Bohai Bay waters

The densities of 36 water samples from the Huanghe River estuary and Bohai Bay were determined by a magnetic float densimeter under three temperatures from 15°C to 25°C. All the measured densities of samples were greater than that of the values calculated from the International Equation of State of Seawater. The differences between the measured and calculated densities increased with the decrease of salinities. The differences appeared exponentially correlated with Ca²⁺]/s, Mg²⁺]/s and SO ₄ ²⁻ ]/s, and had “s” type curve relationship with the alkalinity in all salinity range. But in the salinity ranging from 25.72 to 31.57, the relationships were all linear. The density difference can be estimated from the equation Δρ(10³kg · m⁻³). It was the high alkalinity and Ca²⁺]/s that resulted in the measured densities of seawaters being higher than the calculated densities in the Huanghe estuary and Bohai Bay. This project was supported by the Natural Science Foundation of China.