Long Island Sound interface

Aller RC. 1980a. Diagenesis near the sediment water interface of Long Island Sound. I. Decomposition and nutrient element geochemistry (S,N,P). Advances in Geophysics 22 235-348. 

One major paper attacking the problem of the relationship between the preservation of calcium carbonate in shallow anoxic marine sediments and their chemistry was by Aller (1982). The study was conducted at sites in Long Island Sound. The calcium carbonate content of the sediments decreased with increasing water depth. At the shallow FOAM (Friends of Anaerobic Muds) site shell layers associated with storms resulted in irregular variations in the carbonate content of the sediment. Ca2+ loss from the pore waters, indicative of calcium carbonate precipitation, was found only at the FOAM site below -20 cm depth. During the winter, elevated Ca2+ to CL ratios were observed near the sediment-water interface... 

Fig. 13. Photograph of the cross section of the muddy bottom of Long Island Sound taken with the interface camera developed by Rhoads and Cande (1971). The length of the sediment-water interface spanned in the picture is 0.15 m. 

They are greater in the winter months because of the broadening of the distributions of and v under storm conditions ( and v are E-W and N-S velocity components). In Long Island Sound the pellets at the sediment-water interface undergo frequent resuspension before their incorporation into the permanent sediment. Dispersion of resuspended pellets by both advection and diffusion is rapid. New silt-clay-size mineral matter Introduced into the Sound will be rapidly distributed throughout the layer of pellets mantling the mud buttom. Chemical species adsorbed on silt-clay particles will be similarly dispersed. 

This estimate is compared to the specific activity of likely sources (upland and marine) in Table XIII. It appears that neither material scoured from the mud-water interface of Long Island Sound nor material eroded from the upland surface is an allowable source, since only material from beneath these surfaces is of sufficiently low activity. It is relatively difficult to effect deep (18-20 cm) erosion of submarine sediment in Long Island Sound, but common for upland soil to erode deeply, especially when land is disturbed by agriculture or construction. This indicates that the source of low-specific-activity inorganic matter is the eroding subsurface material of the watershed. 

DIAGENETIC PROCESSES NEAR THE SEDIMENT-WATER INTERFACE OF LONG ISLAND SOUND. I. Decomposition and Nutrient Element Geochemistry... 

Pore-water profiles of Fe and from three stations in Long Island Sound have general depth-dependent concentration distributions similar to those reported from other sedimentary basins concentrations rise above seawater values to a maximum below the interface and then decrease again or remain constant deeper in the deposit. Beyond these general features, specific features of the profiles reflect the internal transport-reaction regime effective at each station. 

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