Investigation of Contaminant Transport and Dispersion in New York Harbor by a High Resolution SF6 Tracer Study
Abstract
Sulfur hexafluoride (SF6) has been used successfully as a deliberate tracer for rivers, estuaries, and coastal areas, due to its inert nature, non-toxicity, and extremely low detection limit. An automated, high-resolution SF6 measurement system mounted on a boat was recently developed for several projects on the Hudson River. The system has a sampling interval of two minutes and a detection limit of 1 x 10-14 mol L-1. Real-time data visualization enables revisions of sampling strategy during the experiment. A single injection has allowed observation of advection rates, dispersion processes, and air-water gas exchange for up to two weeks, and longer experiments are possible. This equipment, with minor modifications, was applied to New York Harbor in July 2002. New York Harbor is one of the busiest seaports in the United States, processing nearly \100 billion in cargo each year. Most of the shipping facilities are located in Newark Bay (approximately 15 km^{2}) or in two adjacent channels: the Kill van Kull (6 km long) and the Arthur Kill (20 km long). Newark Bay, which is mostly saline, is fed by the Hackensack and Passaic Rivers, both of which flow through heavily industrialized areas. Ultimately, these waters drain through the Kills to Raritan Bay and the Atlantic Ocean. Due to a combination of point sources, runoff, wastewater treatment plants, and emissions from the shipping industry, Newark Bay and the Kills receive a large volume and variety of contaminants, including petroleum, heavy metals, PCBs, and dioxins. In addition, much of the area is subject to ongoing and extensive navigational dredging, causing widespread re-suspension of previously deposited contaminants. A small quantity (ca. 2 mols) of SF_{6}$ was injected into northern Newark Bay to investigate the spreading of water throughout the Bay, the Kills, and the tidal portions of the Passaic and Hackensack Rivers. The tracer was successfully monitored across most of this area for 12 consecutive days. Most measurements were taken at a depth of 1 m, with deeper profiles at certain locations. Numerous CTD casts were made to examine the halocline and thermocline at different points. The study period coincided with relatively dry and calm conditions. The data suggest rapid initial dispersion, both laterally and vertically, driven by the tides. However, flushing of the area as a whole was slow during the study period. After two weeks, the tracer persisted throughout Newark Bay, the Kills, and the lower reaches of the rivers. Bulk seaward advection was weak, although a considerable quantity of tracer found its way out of the Kills due to tidal action, whereupon it was heavily diluted in Raritan Bay or Upper New York Bay. Overall, the study enables prediction of available response time for certain contamination events, while also providing critical validation data for computational fluid dynamics models of this area.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMOS22B0274C
- Keywords:
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- 4235 Estuarine processes;
- 4251 Marine pollution;
- 4568 Turbulence;
- diffusion;
- and mixing processes