Thomas P. Carsey

Farfield Tracing of a Point Source Discharge Plume in the Coastal Ocean Using Sulfur Hexafluoride

Pathways and dilution of a point source ocean discharge in the farfield (approximately to 10-66 km) were measured using the deliberate tracer sulfur hexafluoride (SF6). The injection of SF6 was performed by bubbling the gas over a period of 6 days into an ocean outfall pipe discharging into the southeast Florida coastal ocean. The surface SF6 concentrations show that the discharged water flowed northward parallel to the coast with a broadening of the width of the plume to about 3 km at the farthest point sampled, 66 km from the outfall. The discharge was fully mixed throughout the water column within 13 km of the outfall terminus. In the first 20 km from the outfall, SF6 surface concentrations were highly variable, while beyond this the SF6 concentrations decreased monotonically going northward. The currents were measured during the study with a bottom-mounted acoustic Doppler current profiler (ADCP) located 5.5 km from the outfall. Velocities were variable in magnitude and direction but showed a net northward flow during the 6-day study. Maximum concentrations decreased by about 200-fold per kilometer from the outfall to the northern end of the study area. The study shows that SF6 is an effective method to trace point source releases far from their origin.

Evaluation of Direct-on-Filter Methods for the Determination of Respirable α-Quartz

Abstract Two direct-on-filter methods for the determination of respirable α-quartz in air by X-ray powder diffraction (XRD) were compared with NIOSH Method 7500. The two direct-on-filter methods are direct-on-silver membrane filter and direct-on-mixed cellulose ester (MCE) filter with XRD analysis directly on the collection filter. Both the silver membrane and the mixed cellulose ester methods were subjected to a side-by-side comparison with NIOSH Method 7500 using a laboratory-generated atmosphere of mine dust. The comparison showed with 95 percent confidence that any single measurement by the direct-on-MCE method would produce a result within 25 percent on any single measurement of Method 7500 under the same experimental conditions over the range 200–1200 μg. The comparison also showed the direct-on-silver method would produce a result within 30 percent, with 95 percent confidence over the same range. There is some suggestion of a slight negative bias of the direct-on-silver method with respect to Metho...

An Investigation of the Performance of the 10-mm Nylon Cyclone

Abstract The sampling device recommended by the National Institute for Occupational Safety and Health for the determination of respirable silica is a 10-mm nylon cyclone and 37-mm cassette loaded with a PVC-type filter and operated at 1.7 lpm. The device has been subjected to a statistically rigorous determination of the sampling precision under controlled laboratory conditions using a silica-rich mine dust in a laboratory-built generation system. The statistical design used in the investigation eliminated contributions to the precision estimate from run and position effects. The precision of the device over the deposition range 826–1800 μg/sample was found to be 2.18%. In a follow-up study of air leaks in the device, five possible locations of leaks were selected. A set of sampling devices was made with air leaks of varying magnitude in the selected locations. The devices were tested using a vacuum leak testing apparatus. They were then placed in a generation system and challenged with a uniform concentr...

Acoustic methods for water mass delineation in coastal marine ecosystems

Acoustical methods play an important role in the in the study of nutrient sources for coral reef ecosystems in the south Florida coastal ocean. Many nutrients released into the coastal ocean are released in distinct water masses such as inlet discharge plumes, wastewater outfall discharge plumes, and hurricane‐induced re‐suspensions. Using water column acoustic backscatter profiles, obtained via either ship‐borne instrumentation or in‐situ instrumentation, multidimensional images of nutrient bearing water masses are derived. Said images are of assistance in the design of chemical and biological sampling efforts. Examples of water mass imaging will be presented as well as the use of such images in the design of water quality sampling programs. Using a combination of acoustic backscatter, Doppler current profilers, nutrient (nitrate, nitrite, silica, phosphate, ammonia) samples and microbiological (fecal, protozoa, viruses) samples, flux estimates of said quantities may be made for inlet discharges. Results...