John L. Ferry

Transfer of gold nanoparticles from the water column to the estuarine food web.

Within the next five years the manufacture of large quantities of nanomaterials may lead to unintended contamination of terrestrial and aquatic ecosystems. The unique physical, chemical and electronic properties of nanomaterials allow new modes of interaction with environmental systems that can have unexpected impacts. Here, we show that gold nanorods can readily pass from the water column to the marine food web in three laboratory-constructed estuarine mesocosms containing sea water, sediment, sea grass, microbes, biofilms, snails, clams, shrimp and fish. A single dose of gold nanorods (65 nm length x 15 nm diameter) was added to each mesocosm and their distribution in the aqueous and sediment phases monitored over 12 days. Nanorods partitioned between biofilms, sediments, plants, animals and sea water with a recovery of 84.4%. Clams and biofilms accumulated the most nanoparticles on a per mass basis, suggesting that gold nanorods can readily pass from the water column to the marine food web.

Methods for reactive oxygen species (ROS) detection in aqueous environments

This review summarizes direct and indirect analytical methods for the detection and quantification of the reactive oxygen species (ROS): 1O2, O2·−/HOO·, H2O2, HO·, and CO3·− in aqueous solution. Each section briefly describes the chemical properties of a specific ROS followed by a table (organized alphabetically by detection method, i.e., absorbance, chemiluminescence, etc.) summarizing the nature of the observable (associated analytical signal) for each method, limit of detection, application notes, and reaction of the probe molecule with the particular ROS.

Autoinducers extracted from microbial mats reveal a surprising diversity of N-acylhomoserine lactones (AHLs) and abundance changes that may relate to diel pH.

Microbial mats are highly structured and diverse communities, and one of the earliest-known life assemblages. Mat bacteria interact within an environment marked by strong geochemical gradients and fluctuations. We examined natural mat systems for the presence of autoinducers involved in quorum sensing, a form of cell-cell communication. Our results revealed that a diverse array of N-acylhomoserine lactones (AHLs) including C(4)- to C(14)-AHLs, were identified from mat extracts using mass spectrometry (MS), with further confirmation by MS/MS-collision-induced dissociation (CID), and additions of external standards. Microelectrode measurements showed that mats exhibited diel pH fluctuations, ranging from alkaline (pH 9.4) during daytime (net photosynthesis) to acidic (pH 6.8) during darkness (net respiration/fermentation). Under laboratory conditions, AHLs having shorter acyl-chains were degraded within the time frame that daily alkaline pH (> 8.2) conditions exist in mats. Intensive sampling of mats after full day- or night-time incubations revealed that accumulations of extractable shorter-chain AHLs (e.g. C(8)- and C(10)-AHLs) were significantly (P < 0.001) diminished during daytime. Our study offers evidence that stabilities of AHLs under natural conditions may be influenced by the proximal extracellular environment. We further propose that the ancient periodicity of photosynthesis/respiration in mats may potentially drive a mechanism for diel differences in activities of certain autoinducers, and hence bacterial activities mediated through quorum sensing.

Fipronil effects on estuarine copepod (Amphiascus tenuiremis) development, fertility, and reproduction: a rapid life-cycle assay in 96-well microplate format.

Fipronil is a novel gamma-aminobutyric acid receptor-specific phenylpyrazole insecticide commonly used near estuarine environments for rice production, turf-grass management, and residential insect control. In this study, we evaluated the acute, developmental, and reproductive toxicity of fipronil to the estuarine harpacticoid copepod Amphiascus tenuiremis. Fipronil was highly toxic to A. tenuiremis (adult 96-h median lethal concentration [LC50] = 6.8 microg/L) and was more toxic to male copepods (96-h LC50 = 3.5 microg/L) than to nongravid female copepods (96-h LC50 = 13.0 microg/L). By using a newly developed 96-well microplate-based life-cycle toxicity test, we successfully reared single individuals of A. tenuiremis to adulthood in 200-microl microwells and concurrently assessed developmental and reproductive effects (after paired virginal matings) of environmentally relevant aqueous fipronil concentrations (0.16, 0.22, and 0.42 microg/L measured). Throughout the entire life cycle, copepod survival in all treatments was >90%. However, fipronil at 0.22 microg/L and higher significantly delayed male and female development from stage 1 copepodite to adult by approximately 2 d. More importantly, fipronil significantly halted female egg extrusion by 71% in the 0.22-microg/L fipronil treatment, and nearly eliminated reproduction (94% failure) in the 0.42-microg/L fipronil treatment. A three-generation Leslie matrix-based population growth model of fipronil reproductive and life-cycle impacts predicted a 62% decline in population size of A. tenuiremis relative to controls at only 0.16 microg/L.

Chemical Challenges to Bacterial AHL Signaling in the Environment

Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia,South Carolina 29208, United States, and Department of Chemistry and Biochemistry, College of Arts and Sciences, University of South Carolina,Columbia, South Carolina 29208, United StatesReceived September 16, 2010

Gold nanorods as nanoadmicelles: 1-naphthol partitioning into a nanorod-bound surfactant bilayer

As-prepared gold nanorods, stable in aqueous solution, bear a bilayer of the cationic surfactant cetyltrimethylammonium bromide (CTAB). This bilayer provides a approximately 3 nm thick hydrophobic layer that could be used to sequester hydrophobic organic molecules from aqueous solution. We have investigated the uptake of 1-naphthol as a model hydrophobic compound by CTAB-coated gold nanorods using both ultraviolet-visible spectroscopy and gas chromatography with flame ionization detection. We find the adsorption isotherm of 1-naphthol partitioning into the CTAB bilayer on gold nanorods fits the Langmuir model. The maximum number of bound 1-naphthol molecules is 14.6 +/- 2.2 x 10(3) molecules per gold nanorod, with an equilibrium binding constant of 1.97 +/- 0.79 x 10(4) M(-1) at room temperature.

Mechanisms for naphthalene removal during electrolytic aeration.

Batch tests were performed to investigate chemical and physical processes that may result during electrolytic aeration of a contaminated aquifer using naphthalene as a model contaminant. Naphthalene degradation of 58-66% took place electrolytically and occurred at the same rates at a pH of 4 and 7. 1,4-naphthoquinone was identified as a product of the electrolysis. Stripping due to gases produced at the electrodes did not result in any naphthalene loss. Hydrogen peroxide (which may be produced at the cathode) did not have any effect on naphthalene, but the addition of ferrous iron (which may be present in aquifers) resulted in 67-99% disappearance of naphthalene. Chlorine (which may be produced from the anodic oxidation of chloride) can effectively degrade naphthalene at pH of 4, but not at a pH of 7. Mono-, di- and poly chloronaphthalenes were identified as oxidation products. Ferric iron coagulation (due to the oxidation of ferrous iron) did not significantly contribute to naphthalene loss. Overall, electrolytic oxidation and chemical oxidation due to the electrolytic by-products formed are significant abiotic processes that could occur and should be accounted for if bioremediation of PAH-contaminated sites via electrolytic aeration is considered. Possible undesirable products such as chlorinated compounds may be formed when significant amounts of chlorides are present.

Stereoselective degradation of aqueous endosulfan in modular estuarine mesocosms: formation of endosulfan γ-hydroxycarboxylate

Solutions of alpha-endosulfan, beta-endosulfan, and technical grade endosulfan (70alpha:30beta) were added to modular estuarine mesocosms; the kinetics and degradation products from each mesocosm are reported. The persistent product endosulfan sulfate was generated in all cases; however, its yield was approximately a factor of three higher from alpha-endosulfan relative to beta-endosulfan. Beta-endosulfan hydrolyzed faster than alpha-endosulfan to endosulfan diol, which then rapidly degraded to endosulfan ether, endosulfan alpha-hydroxyether (major product), and endosulfan lactone. The ring-opened form of the lactone, endosulfan gamma-hydroxycarboxylate, is reported for the first time; it appears to be a terminal product, at least over the timescale of the experiment. The equilibrium between endosulfan gamma-hydroxycarboxylate and endosulfan lactone is dependent on pH, as only the protonated form of the gamma-hydroxy acid undergoes ring-closure. The pKa of the gamma-hydroxy acid was determined to be 5.7, implying that the lactone will quickly open and deprontonate under environmentally relevant conditions.

Surface-functionalization effects on uptake of fluorescent polystyrene nanoparticles by model biofilms.

A study was conducted to investigate the role of nanoparticle (NP) surface functionalization/charge on their uptake by biofilms. Biofilms, bacterial colonies attached to surfaces via extracellular polymers, are effective at removing suspended nanomaterials from the aqueous phase. However, the mechanisms regulating particle uptake are unknown. Here, it was shown that the mechanism was strongly dependent on the nanoparticle surface ionization, and not the core composition of the NP. Uptake experiments were conducted using laboratory-cultured biofilms. The biofilms were incubated in the presence of fluorescent polystyrene NPs with either negatively-charged surfaces (i.e. functionalized with sulfated (SO4−-NP) or carboxylated (COO−-NP) groups) or positively-charged surfaces (functionalized with primary amines, Amine-P). Particles with negatively-charged sulfated surfaces associated most strongly to biofilms across all experimental conditions. Associations of positively-charged amine particles with biofilms were greatest at high ionic conditions resembling those of seawater, but were sensitive to changes in ionic strength. Sorption of COO−-NPs was lowest, relative to other particle types, and was not sensitive to ionic strength. The results of this study support an emerging precedent that biofilms may be an effective player in the binding and sequestration of nanoparticles in aqueous systems.

The fate of fipronil in modular estuarine mesocosms

The degradation and corresponding product manifold for the pesticide fipronil was determined in three replicate estuarine mesocosms. Aqueous fipronil concentrations rapidly decreased over the 672 h timescale of the experiment (95% removal). Loss was apparently first-order in fipronil, although there appeared to be a change in the removal mechanism after 96 h that corresponded to a dramatic slowdown in its disappearance. The reduction product of fipronil, fipronil sulfide, was not detected in the water column; however, it formed rapidly in sediments and was identified as the major product of fipronil degradation in the system (20% yield at 672 h, with respect to initial fipronil concentration). Fipronil sulfone is thought to form primarily via biological oxidation; and, although it was generated rapidly in the water column (10% yield), only trace amounts were detected in the sediment (1% yield). The direct photolysis product of fipronil, fipronil desulfinyl, was present in all samples; it formed rapidly in the water column (4% yield) and partitioned into the sediment phase (7% yield) over the course of the experiment. The mass balance on fipronil and associated products was 42% at 672 h.