| Measurement on suspended sediment concentration is one of the most important content in observing hydrographic features. And it is also one of the parameters to calculate suspended sediment flux in the seawater. The increasingly serious coastal erosion leads to the deterioration of the Yellow River Delta growth and the delta economic development environment. The following research was done funded by the National High Technology Research and Development Program of China (863 Program) (Contract No.2008AA09Z109). This study aimed to establish the relationships between suspended sediment concentration and electrical conductivity. This method lays the foundation for developing the in-situ monitoring instrument in storm surge.Sediments in this study were sampled from the Yellow River Delta. This paper focused on the relationships between suspended sediment concentration and electrical conductivity and their influential factors, the applicability of quantitative function and software program. Optimum function between suspended sediment concentration and conductivity was finally achieved.Firstly, the experiments on the relationships between suspended sediment concentration and conductivity were designed. The results showed that good relationships existed between them at the same salinity, temperature and grain size and the conductivity values decreased with suspended sediment concentration. Salinity was the most influencing factor among them, temperature took the second place and the effect of grain size could be neglect in this test. Experimental data were fitted with the method of multiple linear regression analysis and the correlation coefficient of equation is 0.9699. Error analysis shows that when the salinity is less than 10‰, the measuring error is abnormally large. And when the salinity is more than 10%o, average absolute relative error is about 5%. Therefore, the formula is available at that salinity. Influential magnitude of every influencing factor is 72.85%, 27.10% and 0.06% respectively.Secondly, the applicability of the formula between suspended sediment concentration and conductivity was investigated. It was found by in situ flume experiment that the formula was more applicable to measure suspended sediment concentration within 225 g/L. At that time, the relative errors were small between measured conductivity values and the calculated ones using the formula. The experimental relative errors would be increased with increasing concentration, but in the higher salinity seawater, the larger suspended sediment concentrations could not lead to bigger experimental errors. The salinity of Yellow River Delta areas is about the same as standard seawater which salinity is 35‰, therefore, the formula on the relationships between suspended sediment concentration and electrical conductivity can be better applied to automatically determine the suspended sediment concentration in Yellow River Estuary.Finally, the data of developing conductivity probe were calibrated by the difference between WTW PH/Cond340i conductivity sensor data and developing conductivity probe data at different salinities. The formula between suspended sediment concentration and electrical resistivity was written to the data processing software and then suspended sediment concentration in seawater could be automated decided.It is the first time to achieve the measurement of suspended sediment concentration with conductivity sensors in the seawater. Software is produced based on the corrected formula. Combined with the developing in situ monitoring instrument, suspended sediment concentration can be measured in situ during a storm. So it must have a wide application range.
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