Within the next five years the manufacture of large quantities of nanomaterials may lead to unintended contamination of terrestrial and aquatic ecosystems 1 . The unique physical, chemical and electronic properties of nanomaterials allow new modes of interaction with environmental systems that can have unexpected impacts 2,3 . 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 3 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.The transport of contaminants to oceans through estuaries is often mediated by chemical and physical processes associated with mixing fresh water with sea water. As this region is also the habitat for many commercially and ecologically important shellfish and finfish, it could also be a critical point of nanomaterial contaminant entry into the marine food web. For example, salinity gradients, such as those found in tidal mixing zones, typically promote the flocculation and precipitation of organic matter and naturally occurring particulates 4,5 . Organic matter and particulates can be consumed by detritivores or shellfish, and they can also be a sink for anthropogenic material through burial in sediments 6 . At present little is known about the physicochemical behaviour of nanomaterial in the mixing zone, precluding prediction of their eventual environmental distribution. Measurement of nanomaterial distributions in model estuarine systems is a necessary first step towards the evaluation of the effects of nanoparticles on the environment.This study used a series of three replicate estuarine mesocosms as laboratories for measuring the behaviour of nanoparticles in complex environments. These systems are representative of Spartina (cordgrass) dominated estuaries and have been successfully used for estimating the coastal impact of several other contaminants, including atrazine, fipronil, endosulfan and nutrients (Fig. 1) [7][8][9][10] . In this study, three replicates of a complex ecosystem were constructed to model the edge of a tidal marsh creek. The systems were made up from natural, unfiltered sea water from Cherry Point Boat Landing on Wadmalaw Island, South Carolina, USA (salinity determined by conductivity and adjusted to 20‰ by the addition of deionized water) and contained a periodically submerged sediment tray in the primary tank and an attached reservoir for water storage (isolated with a screen) to simulate a tidal cycle [9][10][11] . Sediments were planted with Spartina alterniflora, 100 juvenile Mercenari...

The introduction of Fe(II)(aq) into aerated solutions resulted in net Fe(II) oxidation with concomitant, rapid Fe(II)/Fe(IIII) cycling and concurrent generation of reactive oxygen species. The effect of mixtures of naturally occurring solutes on Fe(II)/Fe(III) cycling and the concurrent oxidation of dissolved organics is reported. The experimental strategy was based on a multivariate, microscale, high-throughput approach for evaluating the effect of covarying concentrations of bromide, iodide, Suwannee River natural organic matter (SRNOM), chloride, and total carbonate species. Superoxide and HO• were evaluated at the center point condition of the experimental design with selective scavengers (superoxide dismutase and benzoic acid). The rate of Fe(II) oxidation decreased in the presence of these scavengers, indicating it is a function of oxygen, superoxide, and HO•. HO• generated during Fe(II)/Fe(III) cycling was quantified with the selective probe 1,3-dicyanotetrachlorobenzene (DCTCB). Through the range of experimental conditions of this design, the ratio of the number of moles of HO• produced to the number of moles of Fe(II) consumed varied from 3 to 750, corresponding to approximately 10 to 2200 Fe(II)/Fe(III) cycles, respectively. The implications of these findings with respect to organic oxidation during the aeration of anoxic Fe(II) rich groundwaters are discussed.

A multifactorial experimental design was employed to quantify and rank the effects of a series of ligands on the rate of Fe(II) (18 microM) oxidation in a system containing chloride, sulfate, carbonate/bicarbonate, fluoride, and natural organic matter (NOM) at pH 8.34 +/- 0.13. Several factors and combinations thereof correlated with the rate of Fe(II) oxidation at the 95% level of confidence. Presented in decreasing order of significance, those factors were carbonate/bicarbonate, NOM, sulfate, chloride, the sulfate/fluoride interaction, and fluoride. The center point of the experimental design was repeated with different organic matters substituted, including Nordic Reservoir NOM, fulvic and humic acids; Suwannee River NOM, fulvic and humic acids; and Pony Lake fulvic acid. Despite the widely differing geographical origins of these organic materials, their overall impact on the oxidation rate of Fe(II) was consistent with the observed rate varying no more than a factor of 2 as a function of different organic matters (on a milligrams of carbon per liter basis). The utility of the pentafactorial response surface model (based on Nordic Lake NOM) to predict Fe(II) oxidation rates was evaluated for different natural water samples, including two seawater and one freshwater.

The determination of sub-ppm concentrations of aqueous perfluoroalkylsulfonate (PFSt) anions, including perfluorooctylsulfonate (PFOS), has been accomplished with a relatively simple mass spectrometric procedure that does not require extraction of the analytes into an organic solvent or a chromatographic separation prior to injection into the negative-ion electrospray ionization mass spectrometer. Sample pretreatment was minimized and consisted of dilution of the aqueous samples of groundwater, surface water, tap water, and distilled water with acetonitrile, addition of dodecylsulfate (DDS) as an internal standard, and, in some cases, addition of known amounts of perfluorobutylsulfonate (PFBS) or PFOS for standard-addition experiments. The linear-response range for PFOS is 25.0 microg L(-1) to 2.5 mg L(-1). The lower limit of this range is three orders of magnitude lower than an equally straightforward chromatographic method. The relative errors for standard aqueous solutions containing only 25.0 microg L(-1) and 2.5 mg L(-1) PFOS are +/- 14% and +/- 7%, respectively, with 133 microg L(-1) DDS as the internal standard. The detection limit and quantification limit for PFOS in these standards are 5.0 microg L(-1) and 25.0 microg L(-1), respectively. Six different PFS anions, containing three to eight carbon atoms, were identified and quantified in an aqueous film-forming foam (AFFF) formulation using the method of standard additions. Two alkylsulfate anions and two perfluoroalkylcarboxylate anions were also identified in the AFFF formulation.