Gordon T. Wallace

Temporal trends of triclosan contamination in dated sediment cores from four urbanized estuaries: evidence of preservation and accumulation.

Triclosan is an antimicrobial agent added to a wide array of consumer goods and personal care products. Through its use, it is introduced into municipal sewer systems where it is only partially removed during wastewater treatment. In this study, triclosan was measured in dated sediment cores from four urbanized estuaries in order to reconstruct temporal and spatial trends of accumulation. Measurable concentrations of triclosan first appeared in each of the sediment cores near 1964, which corresponds with the US patent issuance date of triclosan. The presence of triclosan at each of the study sites at or near the patent date indicates that long-term preservation is occurring in estuarine sediments. Temporal trends of triclosan at each location are unique, reflecting between site variability. Concentrations at one site climbed to as high as 400ngg(-1), due in part, to local commercial production of triclosan. At two locations, levels of triclosan rise towards the surface of each core, suggesting increasing usage in recent years. One location adjacent to a major combined sewer overflow had high sediment concentrations of triclosan, confirming their potential as a source of triclosan to estuaries.

Gut contents: A significant contaminant of Mytilus edulis whole body metal concentrations

Ingested matter can have a significant effect on whole body metal concentration measurements in Mytilus edulis. Depuration of mussels in clean seawater for 36 h prior to dissection eliminates most of these contaminating gut contents. Depuration followed by metal analyses is the most direct method of determining mussel tissue metal bioburdens. After being transplanted into a plume of primary treated sewage effluent in Salem Harbor, Massachusetts for 32 days, Al, Cr, and Fe concentrations in depurated mussels were significantly lower than those determined for either non-depurated mussels or for depurated mussels to which fecal concentrations of Al, Cr, and Fe were added back in. Although mathematical methods developed by both Ouellette (1978) and Boehm et al. (1988) could be applied to non-depurated mussels in order to correct for errors associated with gut metal contamination, these indirect methods were not as reliable as depuration prior to analysis.

HISTIDINE-RICH GLYCOPROTEIN FROM THE HEMOLYMPH OF THE MARINE MUSSEL MYTILUS EDULIS L. BINDS CLASS A, CLASS B, AND BORDERLINE METALS

Few studies have directly addressed the question of how metals (both essential and nonessential) are transported in the circulatory system of bivalve mollusks. One potential metal-transport protein, histidine-rich glycoprotein (HRG), has previously been isolated and characterized from the blood plasma of the marine mussel Mytilus edulis L. The present study was undertaken to investigate the extent to which mussel HRG can bind a variety of essential and nonessential metals in vitro, using immobilized metal-ion affinity chromatography (IMAC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The equilibrium metal speciation model MINTEQA2 was used to compute the amount of metal that bound to the IMAC packing material during the charging and initial wash steps. Results demonstrated that HRG can bind all seven of the metals tested (Ca, Cd, Hg, Mg, Ni, Pd, and Zn) and that HRG is the only metal-binding protein in IMAC eluents. Because HRG-metal binding strengths (log K(a)) likely correspond with histidine-metal binding strengths, and because HRG is the predominant mussel plasma protein, the majority of each of the seven metals probably would be present in mussel blood as protein-bound metal rather than as free metal ion. The finding that a single mussel plasma protein may be responsible for binding all these metals raises important questions about how these different metals are subsequently transferred from HRG to different tissues of the mussel, where they may exhibit tissue-specific patterns of utilization, sequestration, elimination, and toxicity.

Flux of surface‐active organic complexes of copper to the air‐sea interface in coastal marine waters

Concentrations of surface-active organic complexes of copper in coastal seawater were used to estimate their transport from the water column to the air-sea interface by molecular diffusion and bubble scavenging. Under average wind conditions observed in Massachusetts Bay, molecular diffusion to the air-sea interface was the primary transport mechanism. Estimated diffusion flux rates ranged from 3.8 to 210 x 10 -17 mol Cu cm -2 s -1 , with a mean value of 62 x 10 -17 mol Cu cm -2 s -1 . Temporal variability in the flux rates was directly related to estimated rates of primary production, presumably due to the biological production of surface-active organic matter within the bulk water. Flux rates due to bubble scavenging were generally 3 orders of magnitude less than those observed for diffusion, with a mean value of 2.3 x 10 -19 mol cm -2 s -1 for particulate Cu and 3.7 x 10 -19 mol cm -2 s -1 for dissolved Cu. Temporal variability of the estimated bubble-mediated fluxes reflected sensitivity to changes in wind stress, as well as the variablility in concentration of the surface-active forms of copper. Residence times of copper in the sea-surface microlayer, based on a comprehensive estimate of the flux of copper from bulk water and atmospheric sources, ranged from 2 min during a phytoplankton bloom period to 21 min during the winter months. Estimates of the flux of surface active forms of copper from the water column to the air-sea interface suggest that the entire inventory of copper within the surface mixed layer of Massachusetts Bay can be cycled through the microlayer within approximately 50 days. This is of the same timescale as the residence time of copper within the surface mixed layer of Massachusetts Bay, indicating that a major portion of copper within the surface mixed layer will be transported to the microlayer before removal from the mixed layer. The formation and transport of surface-active forms of copper may significantly influence the biogeochemical behavior of copper and, perhaps, other metals within the surface mixed layer.

Measurement of Free Cu Ion Activity in Seawater Using a Passive-Equilibrium Sonic-Assisted Free Ion Recorder (SAFIR)

A passive equilibrium probe, sonic-assisted free ion recorder (SAFIR), was recently developed to monitor free Cu ion activity ({Cu(2+)}) in aquatic environments. The SAFIR is user-friendly and can be deployed on-site to record the ambient {Cu(2+)} in an accurate and fast manner. It consists of a chemically modified polystyrene disk (Primaria disk) containing metal ion-binding functional groups, coupled with a sonic horn in a flow-through cell. The calibration of the disk was successfully conducted in metal-ion buffered seawater solutions (pH 8.2, salinity = 32) with {Cu(2+)} ranging from 10(-9.0) to 10(-15.0) mol/L. The Cu adsorbed on the surface of the Primaria disk (Cu(ads)) correlated linearly with the ambient {Cu(2+)} through a Frendlich equilibrium adsorption model. The adsorption process was kinetically enhanced by the introduction of ultrasound, allowing equilibrium between the SAFIR and the ambient {Cu(2+)} in 10 min. The SAFIR was deployed in several coastal regions, and the {Cu(2+)} recorded by SAFIR were in good agreement with the results obtained from corresponding electrochemical analysis.