ANTHROPOGENIC IMPACTS ON SEDIMENT DYNAMICS WITHIN SALEM SOUND, MA AS RECONSTRUCTED FROM DATED SEDIMENT CORES

The Salem Sound watershed (MA) is a developed residential area that has experienced human activity since settlement in the early 1600s. It also contains two major point sources of pollution: the Salem Harbor Power station, a coal-burning power plant, as well as the South Essex Sewerage District’s wastewater treatment facility. This study hypothesizes that anthropogenic changes are influencing the sediment dynamics in Salem Sound and that these changes have been preserved in the sediment record. Six cores were taken at three locations within the Sound to test this hypothesis. One core from each location was extruded to create a ²¹⁰Pb and ¹³⁷Cs age model, while the remaining three cores were used for lab analyses. Loss on ignition (LOI) analysis was performed to quantify organic matter. Volume and mass magnetic susceptibility, as well as frequency dependence, was also determined. Based on preliminary age models, a sedimentation rate for each location was calculated. LOI values in the core proximal to the sewage outfall pipe appear to correspond to historic events and changes in sewage treatment. There is a rapid increase in LOI values, from 6.6% to 11.8% at the depth that corresponds to 1905 (~18cm), when the sewage outfall pipe was constructed. Similarly, values decrease at depths that correspond to when sewage treatment was upgraded to primary (~6cm) and later secondary (~2cm) treatment. Volume and mass magnetic susceptibility appears to reflect power plant activity, as values significantly increase at ~10cm, which corresponds to power plant construction (1952). Frequency dependence data suggest that this increase in susceptibility could be associated with fly ash since values in the upper 10cm are almost consistently 0%. These values are significantly lower than the rest of the core. There is also a peak in magnetic susceptibility (5.37x10^-8 m³/kg) at approximately 16cm, which could be due to the Great Salem Fire of 1914. At this depth, LOI values decrease as well, which supports the hypothesis.