The variation in the cation exchange capacity (CEC) of suspended sediment entering the Delaware Bay was determined as a function of salinity. Cation exchange capacity is based on Ca, Mg, Na, and K, the four commonest exchangeable ions. A comparison of the CEC (units in meq/100 g) of suspended sediment with salinity shows a sharp initial decrease from 73 meq/100 g at 0% salinity to a minimum value of 29 meq/100 g at 2.44% salinity, then a gradual rise to 48 meq/100g at 15.03% salinity. The observed trends between CEC and salinity were correlated with sampling conditions (depth, temperature, pH), mineralogy, iron III hydroxide and organic coatings, and the degree of particle flocculation. A very good (> .90) linear correlation exists between the degree of flocculation, e pressed as the proportion of primary (individual, < 2µ) particles, and the CEC's of the overall suspended sediment. The other variables do not show any significant correlation with the CEC-salinity trend. It is evident, therefore, that the process of flocculation leads to a decrease in CEC values. It is speculated that the process of flocculation is a function of the ionic strength of the water. The attraction or repulsion of suspended particles is a surface-charge phenomenon which is controlled by the ionic strength of the water.

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