WP049 (RAD-1117-840274) An experimental and modeling investigation of iron(II)-catalyzed arsenic(III) oxidation.
Start time: 8:00 AM
Rader, K¹, Bisceglia, K², Farley, K³, Mahony, J³, Carbonaro, R³, Di Toro, D¹, ¹ University of Delaware, Newark, Delaware, USA² Johns Hopkins, Baltimore, Maryland, USA³ Manhattan College, Riverdale, New York, USA
Understanding the redox cycling of arsenic in sediments is of critical importance when assessing the fate of arsenic in aquatic environments. Though dissolved molecular oxygen is capable of oxidizing inorganic trivalent arsenic, As(III), the reaction has been found to be quite slow. Recently, a chemical pathway for As(III) oxidation has been proposed in which radical species produced during the oxidation of divalent iron, Fe(II), promote the oxidation of As(III). This mechanism was formulated to explain the rapid yet incomplete As(III) oxidation (25 - 30%) observed in batch systems at circumneutral pH. In this research, the Fe(II)-catalyzed oxidation of As(III) is examined in a synthetic sediment system using both experimental and modeling studies. In this sediment environment, Fe(II) diffusive transport creates the potential for increased As(III) oxidation over that observed in the original batch studies. A favorable comparison between the model and experimental data suggests that this mechanism is viable in sediments.

WP050 (AAA-1115-715050) The aging of copper added to soils: factors and models.
Start time: 8:00 AM
Ma, Y.B.^{1, 2}, Lombi, E.¹, Nolan, A. L. ¹, McLaughlin, M.J.¹, ¹ Land and Water, CSIRO, Adelaide, Australia² Institute of Soil and Fertilisers, Chinese Academy of Agricultural Science, Beijing, China
The aging of Cu added to soil refers to the processes by which the mobility and bioavailability/toxicity of the metals in soil decline with time. The short-term (30 days) and long-term (>1 year) aging of Cu added to 19 European soils at two effective concentrations where plant growth was decreased by 10% and 90% was investigated. The isotopic exchangeability, bioavailable pool, free Cu²⁺ in soil pore water, DGT-Cu and NH₄NO₃-extractable Cu were determined. The results showed that the activity, extractability and lability of Cu added to soils rapidly decreased after spiking especially in high pH soils, probably due to precipitation. After the rapid initial reactions, the lability of Cu still decreased with time continually at a slower rate. Soil pH, incubation time and temperature were the principal parameters controlling the aging. The aging of Cu added to soils was modeled on the basis of processes of precipitation/nucleation of Cu on soil surfaces which were related to the formation of Cu(OH)⁺ in soils and diffusion of Cu into micropores. The activation energies and the apparent diffusion rate coefficients for the aging processes were estimated The long-term model was validated by field soils with different contamination history and could be used to predict the isotopic exchangeability of Cu added to soils based only on soil properties and incubation time.

WP051 (JON-1117-825026) Alkalinity effects on metal speciation and toxicity to Ceriodaphnia dubia in waters of varying hardness.
Start time: 8:00 AM
Jones, A¹, Pac, C¹, Carraway, E^{1, 2}, ¹ Clemson University Institute of Environmental Toxicology, Pendleton, SC, USA² Clemson University School of the Environment, Anderson, SC, USA
The protective effects of increasing hardness towards reducing metal toxicity in aquatic systems has been the subject of much investigation and EPA regulatory criteria account for these effects through the use of a log-linear hardness equation. In most natural waters, hardness and alkalinity are strongly correlated, therefore, studies that focus on hardness alone may successfully describe many observed effects. However, neglecting alkalinity can lead to the misinterpretation of underlying mechanistic processes that are independently influenced by hardness and alkalinity. A few relatively recent studies have demonstrated their independent effects both theoretically and experimentally. The results presented focus on the toxicity of copper(II), mercury(II), zinc(II), and cadmium(II) to Ceriodaphnia dubia. The independent yet interrelated effects of alkalinity and hardness on acute toxicity to C. dubia are demonstrated over a range of alkalinity and hardness conditions. The results indicate that alkalinity plays an important and independent role in mitigating metal toxicity and therefore should be included in the development of water quality criteria. The results are interpreted with the aid of equilibrium speciation modeling (Visual MINTEQ) and discussed in terms of metal toxicity models such as the free ion activity model and the Biotic Ligand Model (BLM), as well as from a kinetic or complex lability perspective.

WP052 (CAS-1117-816846) Spatial distribution and chemical fractionation of Cu and Zn in a storm water retention pond.
Start time: 8:00 AM
Camponelli, K¹, Casey, R¹, Lev, S¹, Landa, E², ¹ Towson University, Towson, MD, USA² US Geological Survey, Reston, VA, USA
Runoff from roadways has been identified as a major non-point source for metals to storm water retention ponds. Zn and Cu are found in tires and brake pads and the degradation of these automobile parts is an important source of these metals to roadway surfaces. A retention pond receiving highway runoff in Owings Mills, MD was chosen to study the fate and transport of the metals from an adjacent four-lane roadway. Soil, pond sediment, and road particulates were all sampled at the site. Sequential extractions were done on the clay-sized fraction and bulk samples. All samples were analyzed using ICP-MS. Overall, the metals were found to be most abundant in the clay sized sediments and soils. The pond samples were found to have higher Zn and Cu concentrations than the surrounding soils. This indicates that the input of these metals into the pond is above the natural soil background. Zn and Cu concentrations in pond sediments represent mixing between the roadway particulates, which have the highest concentrations, and soils. It is therefore likely that these particulates are the primary source of metals to the pond. For bulk soils and the clay size fraction in both the sediment and soil samples, the metals are found mainly in the organic fraction. This may mean that the metals are not highly available to the organisms in and around the pond.

WP053 (NEI-1117-786567) Sonoelectrochemical Determination of Some Heavy Metals in Whole Human Blood.
Start time: 8:00 AM
Nei, Lembit¹, Kruusma, Jaanus², ¹ Tallinn University of Technology, Tartu, Estonia² Environmental Protection Institute, Tartu, Estonia
Heavy metals play a vital role in the functioning of a healthy body. However, when the concentrations of these metals become either too high or too low, the effects can be very serious. The quantitative detection of cadmium, lead and zinc in whole human blood is shown to be possible by anodic stripping voltammetry under conditions of insonation. An immersion horn probe is introduced into a thermostatted conventional three-electrode cell opposite a working electrode. The enhanced mass transport associated with power ultrasound yields efficient pre-concentration of the metal ion before it is detected using anodic differential-pulse stripping voltammetry. Insonation further offers the crucial benefits of first surface activation and cleaning, helping to prevent electrode fouling by the organic components and second fully equilibrating free and bound metal ions in the complex matrix. Acoustic streaming and cavitation promote the mass transport to the surface of electrode, facilitating measurements in solutions of low metal concentrations, where silent measurements fail to yield an analytical signal. The system is calibrated using standard micro additions of cadmium, lead or zinc to give the total amount of the detected metal. The values of cadmium (1.10 g/L), lead (1.01 mg/L) or zinc (1.30 mg/L) concentrations obtained using sonoelectroanalytical methodology were compared with the results obtained by independent atomic absorption spectroscopy (AAS) measurements and a good agreement was found. We would like to thank the Wellcome Trust and Estonian Science Foundation for financial support.

WP054 (SUN-1117-766217) Partitioning of Hg, Se, and As in a pilot-scale constructed wetland for wastewater treatment.
Start time: 8:00 AM
Sundberg, S¹, Hassan, S², Rodgers, Jr., J¹, ¹ Clemson University, Clemson, SC, USA² University of Georgia, Athens, GA, USA
Constructed wetland treatment systems (CWTS) designed to treat constituents of flue gas desulfurization wastewater have the ability to concentrate, transfer, and transform Hg, Se, and As. This results in the distribution of these elements in different forms among environmental media, including sediment, detritus, and macrophytes. The objective of this research was to investigate partitioning of Hg, Se, and As in a pilot-scale constructed wetland by measuring the concentrations in sediment, detritus, on root and submerged shoot surfaces of macrophytes, and within roots, submerged shoots, emerged shoots, and seeds of macrophytes collected from the CWTS. Since determining total concentrations of these constituents in the sediment cannot provide some essential information about mobility, bioavailability, and potential impacts, operationally-defined species of Hg, Se, and As associated with sediment in the CWTS were characterized using sequential fractionation procedures. Detritus contained the greatest concentrations of these elements, with an overall increase in Hg and Se and decrease in As from the wastewater inflow to outflow in the constructed wetland. Sediment concentrations of Hg, Se, and As were one to two orders of magnitude less than detritus. Sediment-associated Hg was primarily in its elemental form, whereas As was largely contained in the sediment fraction consisting of crystalline lattice structures of primary minerals and silicates. Selenium was more evenly distributed among sediment fractions. Significantly more Hg, Se, and As was accumulated by macrophyte tissues than adsorbed to macrophyte surfaces exposed to water. Mercury, Se, and As concentrated in the root tissues, with minimal translocation to the aerial portions of the plant. Negligible concentrations of these constituents were found in the seeds. The observed partitioning of Hg, Se, and As in this CWTS will play an important role in designing the full-scale constructed wetland treatment system.

WP055 (TWA-1117-736853) Spatial and temporal alteration of non-point contamination of soils by Potentially Toxic Elements in floodplains.
Start time: 8:00 AM
Twardowska, I.¹, Janta-Koszuta, K.¹, Stefaniak, S.¹, Kyziol, J.¹, ¹ Polish Academy of Sciences, Institute of Environmental Engineering, Zabrze, Silesia, Poland
Contaminated river sediments deposition poses potential risk to the soil quality in floodplain areas. This was exemplified in a screening survey of soils for PTE - Potentially Toxic Elements (Cd, Cr_t, Cu, Ni, Pb, Zn) carried out in 2000 in the Upper Odra River valley, tree years after the catastrophic flood of 1997. Assessment of the post-flood spatial distribution of PTE with use of the Geographical Information System (GIS), along with metal partitioning with respect to major chemical forms and mobilization potential displayed general, though uneven enrichment of PTE in soils that showed no correlation with the background distribution (k = 0.095-0.439). That was due to the effect of contradictory factors, the most important of them were: (i) PTE-rich river sediment deposition in the water stagnation areas in heavy alluvial soils of pH close to 7; (ii)washout of PTE and soil particulates by floodwaters in the turbulent flow areas and in the light acidic soils of high hydraulic conductivity; (iii) metal ions binding in soils of different sorption capacity and onto sorption "pools" of different binding strength; (iv) mobilization of labile forms of metals that caused temporal quantitative transformations of PTE distribution along the soil profile. The spatial reduction/enrichment of the studied PTE generally followed the similar pattern, though occurred with significantly different intensity compared to the background level, depending upon the metal content and mobility in sediments and soils. Maximun PTE elutriation from soils ranged from 0.5 mg Cd to 121 mg Zn per kg of soil. For all the metals, an overall significant increase of total contents in soil in comparison with the background low level occurred, which accounted for 91.0 mg Zn, 42.3 mg Pb, 22.5 mg Ni, 34.2 mg Cr, 13.6 mg Cu and 0.96 mg Cd per kg of soil(dry matter). That resulted locally in exceeding the standards, although mostly fell within permissible contents and was much below the Risk-Based Concentrations for humans.

WP056 (HAM-1117-848648) Molecular Analyses of Cadmium Toxicity in Arabidopsis, Sorghum, and Tobacco.
Start time: 8:00 AM
Dunkerley, Ray¹, Hamissou, Mijitaba¹, ¹ Jacksonville State University, Jacksonville, Alabama, USA
Cadmium is a non essential heavy metal pollutant of the environment, resulting from agricultural practices, mining, and industrial activities. It is also released into the environment by automobile exhaust gases. Because of its high water solubility, Cd is readily available for uptake by plants and aquatic animals. In plants, Cd has been shown to interfere with the uptake, transport, and use of several essential elements causing complex nutrient deficiency symptoms. Cd appears to be absorbed passively and then translocated freely through the rest of the plant body. Several plant species are known to uptake and store Cd in their chloroplast, therefore affecting various aspects of photosynthesis. Like other heavy metals, the toxic actions of Cd are believed to be exerted on metabolic enzymes by altering their active sites. Cd toxicity in plants is also characterized by a rapid increase in reactive oxygen species (ROS) creating therefore conditions for secondary oxidative stress. The objectives of this research are to investigate the effects of Cd on the activities of ROS scavenger molecules, superoxide dismutase (SOD) and peroxidase (PO) enzymes and on the photosynthetic activities of isolated chloroplasts in arabidospsi thaliana, sorghum bicolor, Nicotiana tobacum challenged with elevated concentrations of Cd. Plants were grown in potted soil and Hoagland pH 6.9 and feed with various concentrations of CdCl2 for 14 days. Toxicity index chlorosis was recodered daily. Biomass accumulation, SOD, POD, and chloroplasts activities were determined at the conclusion of the experiments Preliminary data indicated that Cd causes more chlorosis to tobacco than arabidopsis or sorghum. Citrate dehydrogenase activities were higher in sorghum; PO activities were higher in tobacco; and photosynthetic activities declined as Cd concentrations were increased.

WP057 (TIE-1118-774818) Temporal patterns of watershed-based sources of trace metals in urban runoff.
Start time: 8:00 AM
Tiefenthaler, L¹, Stein, E¹, Schiff, K¹, ¹ Southern California Coastal Water Research Project, Westminster, CA, USA
Urban stormwater runoff is a significant source of trace metals that are persistent in the environment and have been observed accumulating in estuarine and marine sediments at the mouths of urbanized watersheds. There are numerous sources of trace metals in urban watersheds that can be washed out during storm events including exhaust emissions and the wear and corrosion of vehicles (Wilber and Hunter 1979), industry, and other mobile or non-mobile sources. In southern CA we now have a total population of nearly 18 million residing in urbanized areas. This population is expected to grow by 6.3 million people in the year 2030. Concern is that the projected growth of major urban centers means that the pressures on our aquatic ecosystems are going to be increasing in the not too distant future. Hence, more urban stormwater runoff means higher contaminant loads for aquatic receiving environments. The goal of this study was to quantify concentrations and mass emissions of trace metals from several urban and non-urban watersheds. The data were further examined to assess intra-storm variability (first flush) and inter-storm variability (seasonal flush) of metals loading. A total of 14 site-events representing a wide range of storm sizes, antecedent conditions, and highly-resolved samples taken throughout the entire storm, were sampled between 2000 and 2005 throughout the Los Angeles region. Trace metals loads from creeks during wet weather ranged from 0.02-2221 kg/storm. Storms sampled from less developed watersheds (i.e. Santa Monica Canyon and Arroyo Sequit) produced trace metals loads that were one to two orders of magnitude lower than comparably-sized storms in urbanized watersheds (i.e. Los Angeles River and Ballona Creek). Within storm concentrations of trace metals indicated a moderate first flush; between 30% and 60% of the trace metals load was discharged in the first 20% of storm volume.

WP060 (SZL-1117-544622) Lanthanum(III) and cerium(III) in in-situ chemical stabilization of metals in soils with low redox potential.
Start time: 8:00 AM
Szlezak, A.¹, Schwab, A.¹, ¹ Purdue University, West Lafayette, IN, USA
In a water system lanthanum and cerium can remove arsenic from solution by forming insoluble LaAsO4 and CeAsO4 phases. Such phases are highly desired in the in-situ chemical stabilization of heavy metals process because they have low bioavailability. Both La(III) and Ce(III) were added in the laboratory as amendments to soil which originally had low redox potential and high As, Cr, Cd and Pb concentrations. Changes in the bioaccessible fraction of the heavy metals before and after the addition of amendments were determined with in vitro tests. While Ce(III) slightly decreased or had no effect on the bioaccessible fraction of heavy metals tested, La(III) additions strongly increases bioaccessibility. With the addition of La(III) arsenic extractability increased 74% and 78% after 24 hours and a week, respectively, of the addition. The chemistry of the soil is examined to explain the behavior of As after the addition of La(III).

WP061 (MCN-1117-760779) Effects of 5-methyl-1H-benzotriazole on the uptake of metals by sunflower (Helianthus annus).
Start time: 8:00 AM
McNeill, K¹, Cancilla, D¹, ¹ Western Washington University, Bellingham, WA, USA
It has been determined that adverse effects can occur following exposure to low-volume additives in aircraft deicing and anti-icing fluids (ADAF), such as 5-methyl-1H-benzotriazole (5-MeBT). This additive functions as a corrosion inhibitor by binding metal ions in the ADAF solution. When these metal-binding molecules enter the environment, they may continue to bind metal ions in surface and subsurface environments. This complexation may affect the bioavailability of metals, specifically in plants used for phytoremediation. Dose-response curves determined for sunflower plants (Helianthus annus) exposed to 5-MeBT and metals commonly found in airport environments are compared with dose-response curves for plants exposed to combinations of 5-MeBT-metal complexes. Potential genotoxic effects of 5-MeBT, metals, and 5-MeBT-metal complexes are also assessed using PCR and comet assay techniques.