Trapping phosphorus in runoff with a phosphorus removal structure

Reduction of phosphorus (P) inputs to surface waters may decrease eutrophication. Some researchers have proposed filtering dissolved P in runoff with P-sorptive byproducts in structures placed in hydrologically active areas with high soil P concentrations. The objectives of this study were to construct and monitor a P removal structure in a suburban watershed and test the ability of empirically developed flow-through equations to predict structure performance. Steel slag was used as the P sorption material in the P removal structure. Water samples were collected before and after the structure using automatic samples and analyzed for total dissolved P. During the first 5 mo of structure operation, 25% of all dissolved P was removed from rainfall and irrigation events. Phosphorus was removed more efficiently during low flow rate irrigation events with a high retention time than during high flow rate rainfall events with a low retention time. The six largest flow events occurred during storm flow and accounted for 75% of the P entering the structure and 54% of the P removed by the structure. Flow-through equations developed for predicting structure performance produced reasonable estimates of structure "lifetime" (16.8 mo). However, the equations overpredicted cumulative P removal. This was likely due to differences in pH, total Ca and Fe, and alkalinity between the slag used in the structure and the slag used for model development. This suggests the need for an overall model that can predict structure performance based on individual material properties.     

Long-term copper partitioning of metal-spiked sediments used in outdoor mesocosms

Understanding the effects of sediment contaminants is pivotal to reducing their impact in aquatic environments. Outdoor mesocosms enable us to decipher the effects of these contaminants in environmentally realistic scenarios, providing a valuable link between laboratory and field experiments. However, because of their scale, mesocosm experiments are often complex to set up and manage. The creation of environmentally realistic conditions, particularly when using artificially contaminated sediment, is one issue. Here, we describe changes in geochemistry over 1.5 years of a sediment spiked with four different concentrations of copper, within a large freshwater mesocosm facility. The spiking procedure included proportional amendments with garden lime to counteract the decreases in pH caused by the copper additions. The majority of copper within the spiked mesocosm sediments partitioned to the particulate phase with low microgram per liter concentrations measured in the pore waters and overlying waters. The minimum partition coefficient following equilibration between pore waters and sediments was 1.5?×?10⁴ L/kg, which is well within the range observed for field-contaminated sediments (1?×?10⁴ to 1?×?10⁶ L/kg). Recommendations are made for the in situ spiking of sediments with metals in large outdoor mesocosms. These include selecting an appropriate sediment type, adjusting the pH, allowing sufficient equilibration time, and regular mixing and monitoring of metal partitioning throughout the experimental period.     

Assessment of lead uptake in reptilian prey species

As part of an investigation determining the trophically available fraction of metals in a model terrestrial food web, i.e., invertebrate prey to Western fence lizards (Sceloporus occidentalis), we evaluated the ability of several invertebrate prey to bioaccumulate lead and to form metals-rich granules, which are hypothesized to be non-available to predators. Crickets (Acheta domestica), tenebroid beetle larvae (Tenebrio molitor), and isopods (Porcellio scaber) were selected as model prey organisms. Lack of standard exposure methodologies for these species has presented a barrier to trophic transfer evaluations, as each species has particular requirements that create challenges for designing exposure conditions. We were able to devise exposure conditions for all three species that allow long-term exposure studies. All prey organisms accumulated lead from contaminated food, and for all species the majority of the accumulated Pb was associated with the exoskeleton (>50%), with metals-rich granules accounting for most of the remaining accumulated lead.     

Managing for Desired Experiences and Site Preferences: The Case of Fee-Fishing Anglers

Fee-fishing involves paying a fee for the privilege of fishing a body of water where fish populations are enhanced by stocking fish. Past literature on this activity has focused more on the operation of the enterprise and management of the fish than the people and site characteristics. The objectives of the study were to profile anglers and describe their site/management preferences. This study utilized an on-site interview and mail-back questionnaire at fee-fishing establishments in West Virginia (n = 212). Factor analysis of desired recreation experiences yielded five factors: Experience nature & adventure, Stress release & relaxation, Trophy fishing, Escape, and Family time. Cluster analysis showed that these anglers can be segmented into two distinct clusters, differing by sociodemographic characteristics, fishing behavior, and site/management preferences. The findings from this study provide baseline data to aid public resource managers and fee-fishing business owners in determining how to provide satisfying outdoor experiences and deliver desired services on-site. Future research will be needed from additional fee-fishing sites to obtain more detail about this outdoor recreation cohort and be able to generalize to a larger population of participants.     

Partitioning of mono- and polycyclic aromatic hydrocarbons in a river sediment adjacent to a former manufactured gas plant site

The equilibrium distributions, between water and coal-tar contaminated sediment, of 16 monocyclic and polycyclic aromatic hydrocarbons were measured and evaluated for consistency with a Raoult's Law-based quantitative relationship. The quantitative relationship calculates the pore water concentration as the product of the aqueous solubility (or for compounds that are solid at room temperature, the aqueous super-cooled liquid solubility) and the mole fraction concentration of the compound within the liquid coal tar. Sediment was collected at five locations at two depths within a 120 m stretch of a river adjacent to a former manufactured gas plant, and all samples contained non-aqueous phase liquid (NAPL) coal tar. Although the amount of coal tar varied between samples by over an order of magnitude, the Raoult's Law-based NAPL-water partition coefficients for each monocyclic or 2- or 3-ring polycyclic aromatic hydrocarbon measured in this study generally varied within a factor of 2 over all sediments.     

Laboratory studies to characterize the efficacy of sand capping a coal tar-contaminated sediment

Placement of a microbial active sand cap on a coal tar-contaminated river sediment has been suggested as a cost effective remediation strategy. This approach assumes that the flux of contaminants from the sediment is sufficiently balanced by oxygen and nutrient fluxes into the sand layer such that microbial activity will reduce contaminant concentrations within the new benthic zone and reduce the contaminant flux to the water column. The dynamics of such a system were evaluated using batch and column studies with microbial communities from tar-contaminated sediment under different aeration and nutrient inputs. In a 30-d batch degradation study on aqueous extracts of coal tar sediment, oxygen and nutrient concentrations were found to be key parameters controlling the degradation rates of polycyclic aromatic hydrocarbons (PAHs). For the five PAHs monitored (naphthalene, fluorene, phenanthrene, anthracene, and pyrene), degradation rates were inversely proportional to molecular size. For the column studies, where three columns were packed with a 20-cm sand layer on the top of a 5 cm of sediment layer, flow was established to sand layers with (1) aerated water, (2) N(2) sparged water, or (3) HgCl(2)-sterilized N(2) sparged water. After steady-state conditions, PAH concentrations in effluents were the lowest in the aerated column, except for pyrene, whose concentration was invariant with all effluents. These laboratory scale studies support that if sufficient aeration can be achieved in the field through either active and passive means, the resulting microbially active sand layer can improve the water quality of the benthic zone and reduce the flux of many, but not all, PAHs to the water column.     

Birnessite mediated debromination of decabromodiphenyl ether

Decabromodiphenyl ether (BDE-209) is a major component of a commercial flame retardant formulation; however, there is limited information on the fate of BDE-209 in the environment, including metal oxide mediated degradation. Laboratory experiments were conducted to investigate the birnessite (delta-MnO(2))-promoted debromination of BDE-209 in tetrahydrofuran (THF)-water systems as well as catechol solutions. Up to 100% (0.1044 micromol initial charge) of BDE-209 disappeared upon reaction with birnessite in THF/H(2)O (4:6-9:1). The formation of aqueous Br(-) from BDE-209 reduction was determined and up to 16 mole% of initial bromine was released over the course of the reaction indicating approximately 1.7 Br-C bonds were reduced per BDE-209 molecule. The distribution of debrominated congeners, however, indicated a much greater extent of debromination for some products than what was inferred from an average bromine mass balance. The produced congeners varied from tetra- to nona-bromodiphenyl ether, including BDE-47 and -99, during the 24 h reaction. Experiments with deuterated water indicated that water was not the major hydrogen donor in the reduction but rather THF provided the reducing power. This conclusion was supported by the presence of succinic acid, which was produced from oxidation of THF. The reactions with aqueous catechol, rather than THF-water mixtures, were performed to assess the possible role that compounds found in natural environments, such a tannin-like phenols, might have on the chemistry. These experiments indicated that birnessite mediated debromination of BDE-209 might occur in natural settings.