Chemical Changes in Interstitial Waters from Sediments of Lagoonal, Deltaic, River, Estuarine, and Salt Water Marsh and Cove Environments

Abstract

ABSTRACT This paper, a continuation of a previous study (Friedman and others, 1968), concerned with the chemical characteristics of interstitial waters of shelf sediments, considers these same characteristics for lagoonal, deltaic, river estuarine, and salt water marsh and cove environments. For each coring station the chemical characteristics are compared for surface, bottom, and interstitial waters; in many cores changes within the sediment profile have also been measured. At each station, the pH and Eh were measured aboard ship on surface and bottom waters and at regular predetermined intervals along the core. In the laboratory ashore, salinity and the concentrations of calcium, magnesium, potassium, sodium, and strontium were measured. Despite the heterogeneity of the sediments in the cores, all cores contained a high mud fraction and most can best be described as muddy and silty sands or sandy and silty muds. Values of pH and Eh are lower in interstitial waters than in the overlying waters. In lagoonal and river delta cores, and in a core taken from the mouth of the river estuary, the chlorinity is higher in interstitial waters than in overlying waters. However four miles upstream, in the river estuary, the changes are reversed, and the chlorinity in the interstitial waters is lower relative to overlying waters. In salt water marsh and cove environments, the chlorinity above and. below the water-sediment interface is for the most part the same. The Ca/Cl ratio is higher and the Mg/Cl, K/Cl, Na/Cl, and Sr/Cl ratios re lower in the interstitial waters than in the overlying waters for all environments studied regardless of increase or decrease of chlorinity below the water-sediment interface. Biological processes are responsible for the decreases in pH and Eh below the water-sediment interface. Increase in the Ca/Cl ratio and decreases in the ratio of cations to Cl depend on the interaction between clay minerals and water, particularly on cation exchange. The K/Cl ratio in the interstitial waters of the continental shelf and open ocean increases, an observation at variance with that in the transitional environments of the present study and that in formation waters from ancient stratigraphic units.