Caffeine in Boston Harbor past and present, assessing its utility as a tracer of wastewater contamination in an urban estuary.

Sites throughout Boston Harbor were analyzed for caffeine to assess its utility as a tracer in identifying sources of sanitary wastewater. Caffeine ranged from 15ng/L in the outer harbor to a high of 185ng/L in the inner harbor. Inner harbor concentrations were a result of combined sewage overflow (CSO) events as well as illicit discharge of sanitary sewage into municipal storm drains. Comparing current results to data from 1998 to 1999 shows reductions in caffeine levels. Reductions are attributed to termination of effluent discharge to the harbor, declines in the number of CSOs and discharge volume along with efforts to eliminate illicit discharges. Spatial distributions of caffeine identified CSOs as major contemporary sources to the inner harbor. The findings further establish the utility of caffeine as a tracer for sanitary wastewater contamination in urban estuaries and demonstrate the efficacy of pollution reduction strategies undertaken in recent decades in Boston Harbor.

The partitioning of Triclosan between aqueous and particulate bound phases in the Hudson River Estuary.

The distribution of Triclosan within the Hudson River Estuary can be explained by a balance among the overall effluent inputs from municipal sewage treatment facilities, dilution of Triclosan concentrations in the water column with freshwater and seawater inputs, removal of Triclosan from the water column by adsorption to particles, and loss to photodegradation. This study shows that an average water column concentration of 3+/-2 ng/l (in the lower Hudson River Estuary) is consistent with an estimate for dilution of average wastewater concentrations with seawater and calculated rates of adsorption of Triclosan to particles. An average Triclosan sediment concentration of 26+/-11 ng/g would be in equilibrium with the overlying water column if Triclosan has a particle-to-water partitioning coefficient of k(d) approximately 10(4), consistent with laboratory estimates.

Investigating desorption of native pyrene from sediment on minute- to month-timescales by time-gated fluorescence spectroscopy.

We investigated desorption of native pyrene from field-aged sediments using time-gated, laser-induced fluorescence (LIF) spectroscopy. LIF is superior to conventional analytical methods for the measurement of quickly changing dissolved pyrene because it allows observations at minute-scale resolution, has a low detection limit (approximately 1 ng/L), and minimizes sample loss and disturbance since it requires no system subsampling and chemical analysis. The efficacy of LIF was demonstrated in studies of pyrene desorption from Boston Harbor sediment segregated into different size-fractions (38-75, 75-106, and 180-250 microm diameter) and used in varying solid-to-water ratios (20, 70, and 280 mg(solid)/L). The effects of particle size and solid loading on desorption were consistent with diffusion physics. For suspension conditions between 20 and 280 mg(solids)/L, we observed desorption continuing toward an apparent plateau level over the course of weeks to months. This implies that the characteristic desorption time of pyrene from fine sediments and, by inference, other sediment-bound hydrophobic organic compounds (HOCs) of similar hydrophobicity, exceeds the typical characteristic times for pore water flushing and resuspension events. Consequently, the assumption of local sorption equilibrium in modeling efforts would be inappropriate.