Alfred K. Hanson

Chemical studies of copper-organic complexes isolated from estuarine waters using C18 reverse-phase liquid chromatography

Dissolved organic matter (DOM) and dissolved copper-organic complexes were isolated from the estuarine waters of Narragansett Bay, RI, using reverse-phase liquid chromatography employing C18 Sep-Pak cartridges (Waters Associates). The cartridges were found to have a constant retention efficiency for processing ⩽ 1-l volumes of seawater. Fractionation of the isolated material, by sequential elution of the Sep-Pak with water: methanol mixtures of increasing organic solvent concentration, yielded a fraction of the organic matter with a specific copper activity six times greater than the overall activity for the isolated DOM. Analysis of this fraction by high performance liquid chromatography suggested that the organic components are of intermediate polarity and have appreciable aromatic character. An investigation of the protonation characteristics of the isolated complexes indicated that most of the copper is associated with a broad range of acidic sites on the DOM. Analysis by electron paramagnetic resonance spectroscopy confirmed the organic association of the isolated copper and also suggested the presence of several types of binding sites which probably involve oxygen donor ligands. Studies of the exchange of 64Cu with these binding sites on the isolated DOM indicated that 70% of the sites undergo rapid exchange with copper in seawater while 20% of these sites did not exchange in a 24-h time period.

Inhibition of PS II photochemistry by PAR and UV radiation in natural phytoplankton communities.

The effects of PAR and UV radiation on PS II photochemistry were examined in natural phytoplankton communities from coastal waters off Rhode Island (USA) and the subtropical Pacific. The photochemical energy conversion efficiency, the functional absorption cross section and the kinetics of electron transfer on the acceptor side of PS II were derived from variable fluorescence parameters using both pump and probe and fast repetition rate techniques. In both environments, the natural phytoplankton communities displayed marked decreases in PS II photochemical energy conversion efficiency that were correlated with increased PAR. In the coastal waters, the changes in photochemical energy conversion efficiency were not statistically different for samples treated with supplementary UV-B radiation or screened to exclude ambient UV-B. Moreover, no significant light-dependent changes in the functional absorption cross section of PS II were observed. The rate of electron transfer between QA- and QB was, however, slightly reduced in photodamaged cells, indicative of damage on the acceptor side. In the subtropical Pacific, the decrease in photochemical energy conversion efficiency was significantly greater for samples exposed to natural levels of UV-A and/or UV-B compared with those exposed to PAR alone. The cells displayed large diurnal changes in the functional absorption cross section of PS II, indicative of non-photochemical quenching in the antenna. The changes in the functional absorption cross section were highly correlated with PAR but independent of UV radiation. The time course of changes in photochemical efficiency reveals that the photoinhibited reaction centers rapidly recover (within an hour or two) to their preillumination values. Thus, while we found definitive evidence for photoinhibition of PS II photochemistry in both coastal and open ocean phytoplankton communities, we did not find any effect of UV-B on the former, but a clear effect on the latter. The results of this study indicate that the effects of UV-B radiation on phytoplankton photosynthesis are as dependent on the radiative transfer properties of the water body and the mixing rate, as on the wavelength and energy distribution of the radiation and the absorption cross sections of the biophysical targets.

Surface-water acidification and extinction at the Cretaceous-Tertiary boundary

If published estimates of SO2 volatilization and NOx generation by the Cretaceous-Tertiary (K-T) impact were atmospherically converted to sulfuric and nitric acid, globally dispersed, and rapidly rained out, the resulting acid concentrations would bracket a critical threshold in surface-ocean chemistry. Rapid and globally uniform deposition of masses corresponding to the lowest estimates would have had no major effect on sea-surface chemistry. However, similar deposition of masses corresponding to the highest estimates would have provided enough acid to destroy the carbonate-buffering capacity of the upper 100 m of the world ocean and catastrophically reduce surface-ocean pH. Despite the possible effect of the highest estimated acid yields, scenarios that rely on acid rain as the primary explanation of global K-T extinctions are not readily compatible with K-T records of terrestrial and marine survival or culturing studies of modern marine plankton. The possibility that acid rain was a primary cause of K-T extinctions can be tested further by analysis of geographic variation in extinction intensity, because such variation was a likely consequence if the impact resulted in global dispersal and rapid globally uniform deposition of more than ∼6 x 1016 mol of H2SO4 or 1.2 x 1017 mol of HNO3.

Copper complexation in sargasso sea and gulf stream warm-core ring waters

Abstract Two techniques for investigating the speciation of dissolved copper, anodic stripping voltammetry (ASV) and reverse-phase liquid chromatography (C 18 -RPLC) were compared for the marine waters associated with Gulf Stream warm-core rings (WCR). Similarly conditional stability constants (log K ML = 10.0 (± 0.1)) and ligand concentrations (6.4 (± 1.5) nmol kg −1 ) for organic complexation of copper were determined by the two techniques, for oligotrophic Sargasso seawater. Using these constants, the equilibrium copper speciation model predicts the proportion of copper organically complexed to range from 40 to 96% and the Cu (II) ion activity to range from 10 −11.6 to 10 −12.8 as the concentration of organic ligands increases from 5 to 160 nmol kg −1 in Sargasso seawater containing 1 nmol Cu kg −1 . WCR 82B was sampled in August, 1982, when the ring was located in the shelf/slope region adjacent to Cape Hatteras. The vertical distributions of organically-complexed copper determined by the ASV and C 18 -RPLC techniques in the central waters of WCR 82B, were qualitatively similar. A relatively higher proportion (70–90%) of the copper was complexed by the organic ligands present in euphotic waters, particularly at the depth of the chlorophyll a maximum. The ASV and C 18 -RPLC estimates of copper complexation did not agree in the euphotic waters of the ring because some hydrophilic copper-organic complexes were ASV non-labile and were not isolated by the C 18 -RPLC method. In the deeper waters beneath the ring, both the C 18 -RPLC and ASV measurements indicated that ∼ 60% of the copper was complexed by organic ligands, whereas C 18 -RPLC measurements in the deep waters of the Sargasso Sea indicated that hydrophobic organic ligands complexed a smaller fraction (∼ 40%) of the dissolved copper.

An Equatorial Pacific rain event: influence on the distribution of iron and hydrogen peroxide in surface waters

The wet deposition of iron and peroxides was monitored during an intense rain squall in the equatorial Pacific Ocean. Iron and hydrogen peroxide were determined at sea using adsorptive cathodic stripping voltammetry (ACSV) and an enzyme-catalyzed flourometric technique, respectively. The equatorial rainwater was enriched in ACSV reactive iron (average 2.7 nmol Fe kg−1) and hydrogen peroxide (average 8.5 μmol kg−1) relative to the concentrations found in surface seawater (0.05–0.07 nmol Fe kg−1; 40–70 nmol peroxides kg−1). Wet depositional fluxes during the squall varied from 70 to 105 nmol Fe m−2 h−1 and from 56 to 880 μmol peroxide m−2 h−1. The input of rainwater into the surface layer was documented by using hydrogen peroxide and iron signals as well as the depression in surface salinity as tracers. The squall created a patch of lower-salinity surface seawater that was relatively enriched in ACSV reactive iron (0.2–0.3 nmol Fe kg−1) and peroxides (200–300 nmol kg−1). The observed concentrations of iron and peroxides in rainwater, their wet-depositional fluxes, and their initial sea surface enrichments, were quantitatively consistent with independent predictions based on applicable iron aerosol and gas-phase peroxide scavenging models for the region.

Explosives detection in the marine environment using UUV-modified immunosensor

Port and harbor security has rapidly become a point of interest and concern with the emergence of new improvised explosive devices (IEDs). The ability to provide physical surveillance and identification of IEDs and unexploded ordnances (UXO) at these entry points has led to an increased effort in the development of unmanned underwater vehicles (UUVs) equipped with sensing devices. Traditional sensors used to identify and locate potential threats are side scan sonar/acoustic methods and magnetometers. At the Naval Research Laboratory (NRL), we have developed an immunosensor capable of detecting trace levels of explosives that has been integrated into a REMUS payload for use in the marine environment. Laboratory tests using a modified PMMA microfluidic device with immobilized monoclonal antibodies specific for TNT and RDX have been conducted yielding detection levels in the low parts-per-billion (ppb) range. New designs and engineered improvements in microfluidic devices, fluorescence signal probes, and UUV internal fluidic and optical components have been investigated and integrated into the unmanned underwater prototype. Results from laboratory and recent field demonstrations using the prototype UUV immunosensor will be discussed. The immunosensor in combination with acoustic and other sensors could serve as a complementary characterization tool for the detection of IEDs, UXOs and other potential chemical or biological threats.

Submerged explosives detection platforms using immunosensing technology

One of the most difficult aspects of maintaining port and maritime security is the detection, localization, and classification of submerged explosive devices, biochemical agents, and contraband including narcotics. The Explosives Ordnance Disposal (EOD) community has expressed the need for improved methods of detection to augment current capabilities. SubChem Systems Inc. and the U.S. Naval Research Laboratory (NRL) has been working to transition displacement-based immunosensing technology to a commercial system with application towards submerged munitions and contraband detection, classification, and localization. Immunosensing is based upon antibody specificity for a desired target. Funded by the Office of Naval Research, the partners have demonstrated using this technology as a means of chemical detection onboard a custom designed payload for an autonomous underwater vehicle (AUV). The NAVY Small Business Innovative Research (SBIR) program enabled SubChem Systems to provide a concept adaptation of the AUV payload to a diver held version for use in high clutter, low visibility, environments that present an added danger to EOD divers.