Short-to-medium term sediment accumulation in low-energy subtidal areas of lower Hudson River estuary: Geochemical tracers and applications.

摘要

There is still little understanding of the nature and significance of sediment accumulation in low-energy, non-equilibrium coastal "hot-spots". Investigating seasonal-to-yearly scale fine-grained sediment accumulation in low-energy estuarine sites requires a unique tracers and high-resolution, combined biogeochemical approaches.; A high-resolution, multiple biogeochemical tracer approach was used to investigate fine-grained sediment accumulation at a select low-energy, subtidal harbor slip (Pier 32) in NYH. Results indicate that rapid, meta-stable accumulation of fine-grained sediment occurs at the Pier 32 site over time scales as great as 8--10 years.; Strontium isotope ratio (87Sr/86Sr) profiles in sediment cores collected in 2001 from two subtidal harbor slips (Pier 32 and Pier 40) in the lower Hudson River estuary exhibit regular patterns of variability. The observed variability reflects differences in the relative input and trapping of fine grained sediment from seaward sources vs. landward sources linked to seasonal changes in freshwater flow. Sediment strontium isotope ratios can be used to distinguish sediment sources and constrain seasonal-scale variations in sediment trapping and accumulation in dynamic estuarine environments.; Fission-produced 131I (t1/2 = 8.04 days) was measured in wastewater, surficial sediment, and suspended particulate matter (SPM) samples collected from inner New York Harbor (NYH) between 2001 and 2004. Iodine-131 is introduced into municipal waste streams by medical facilities and/or patients treated with the radiopharmaceutical and is released into local waters via effluent. Sediment 131I inventories can be correlated to 7Be (t1/2 = 53.2 days) inventories and surficial sediment 131I activities can be correlated with know indicators of wastewater input and impact (OCsed, Cu, Zn, Pb). Iodine-131 represents a new, source-specific (wastewater) fine-particle tracer in urbanized estuarine systems on time scales of less than one month.; Strontium isotope ratios (87Sr/86Sr) and 131I are two unique biogeochemical tracers that can be used in a combined biogeochemical approach to investigate sediment dynamics and accumulation in coastal, non-equilibrium sites, specifically in urbanized estuaries. Low-energy, subtidal hot-spots serve as natural recorders of local, sedimentary processes over seasonal-to-yearly time scales. These sites constitute significant short-to-medium term sinks for fine-grained particulate materials and particle associated materials in estuarine systems.