Interactions of chlorpyrifos with colloidal materials in aqueous systems

An understanding of sorptive processes is key to describing the fate of chlorpyrifos [O,O-diethyl-O-(3, 5, 6-trichloro-2-pyridyl) phosphorothioate] in aquatic environments. The objectives of this study were to evaluate isotherms for adsorption and desorption of chlorpyrifos on colloidal materials and to advance understanding of interaction mechanisms between chlorpyrifos and colloidal materials. Six Ca-saturated reference smectites, one Ca-saturated humic acid (Ca-humate), and one suspended sediment sample, collected from the Upper Cedar River, Iowa, were studied. A batch equilibration technique was employed to quantify adsorption and desorption isotherms for chlorpyrifos over the 0 to 100 microg L(-1) concentration range in a 0.01 M CaCl(2) background. Large differences in sorption affinity and variation in desorption hysteresis were found among the smectites. Neither chlorpyrifos adsorption nor its desorption were correlated with cation exchange capacity, surface area, or surface charge density of the smectites. The evidence suggests that physical interaction between chlorpyrifos and smectites is the dominant mechanism for adsorption of chlorpyrifos in aqueous systems. Chlorpyrifos was very strongly sorbed on Ca-humate and was not desorbed from the Ca-humate back into the aqueous solution. Chlorpyrifos was moderately sorbed on river sediment, and a large adsorption-desorption hysteresis was also found. The study implies that the nature of both organic and inorganic materials in suspended sediment can influence the adsorption-desorption behavior of chlorpyrifos in aqueous systems.     

Riverine Threat Indices to Assess Watershed Condition and Identify Primary Management Capacity of Agriculture Natural Resource Management Agencies

Managers can improve conservation of lotic systems over large geographies if they have tools to assess total watershed conditions for individual stream segments and can identify segments where conservation practices are most likely to be successful (i.e., primary management capacity). The goal of this research was to develop a suite of threat indices to help agriculture resource management agencies select and prioritize watersheds across Missouri River basin in which to implement agriculture conservation practices. We quantified watershed percentages or densities of 17 threat metrics that represent major sources of ecological stress to stream communities into five threat indices: agriculture, urban, point-source pollution, infrastructure, and all non-agriculture threats. We identified stream segments where agriculture management agencies had primary management capacity. Agriculture watershed condition differed by ecoregion and considerable local variation was observed among stream segments in ecoregions of high agriculture threats. Stream segments with high non-agriculture threats were most concentrated near urban areas, but showed high local variability. 60 % of stream segments in the basin were classified as under U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) primary management capacity and most segments were in regions of high agricultural threats. NRCS primary management capacity was locally variable which highlights the importance of assessing total watershed condition for multiple threats. Our threat indices can be used by agriculture resource management agencies to prioritize conservation actions and investments based on: (a) relative severity of all threats, (b) relative severity of agricultural threats, and (c) and degree of primary management capacity.     

Nitrous Oxide in Agricultural Drainage Waters Following Field Fertilisation

Dissolved nitrous oxide (N₂O), nitrate (NO₃ ^-), and ammonium (NH₄ ⁺) concentrations in an agricultural field drain were intensively measured over the period of field nitrogen (N) fertilisation and for several weeks thereafter. Supersaturations of dissolved N₂O were observed in field drain waters throughout the study. On entry to an open drainage ditch, concentrations of dissolved N₂O rapidly decreased and a total N₂O-N emission via this pathway of 13.2 g over the period of study (45 days) was calculated. This compared with a predicted emission of the order of 300 g, based on measured losses of NO₃ ^- and NH₄ ⁺ in the field drainage water, and the default IPCC emission factor of 0.01 kg N₂O-N per kg Nentering rivers and estuaries. In contrast to widespread evidence of a clear relationship between the amount of N applied to agricultural land and subsequent direct N₂O emission from the soil surface, the relationship between the amount of N₂O in soil drainage waters and the amount of N applied was poor. We conclude that the complexity, both spatially and temporally, of the processes ultimately responsible for the amount of N₂O in agricultural drainage waters make a straightforward relationship between N₂O concentration and N application rate unlikely in all but the simplest of systems.     

Polybrominated diphenyl ethers (PBDEs) in leachates from selected landfill sites in South Africa

The last few decades have seen dramatic growth in the scale of production and the use of polybrominated diphenyl ethers (PBDEs) as flame retardants. Consequently, PBDEs such as BDE -28, -47, -66, -71, -75, -77, -85, -99, -100, -119, -138, -153, -154, and -183 have been detected in various environmental matrices. Generally, in South Africa, once the products containing these chemicals have outlived their usefulness, they are discarded into landfill sites. Consequently, the levels of PBDEs in leachates from landfill sites may give an indication of the general exposure and use of these compounds. The present study was aimed at determining the occurrence and concentrations of most common PBDEs in leachates from selected landfill sites. The extraction capacities of the solvents were also tested. Spiked landfill leachate samples were used for the recovery tests. Separation and determination of the PBDE congeners were carried out with a gas chromatograph equipped with Ni63 electron capture detector. The mean percentage recoveries ranged from 63% to 108% (n=3) for landfill leachate samples with petroleum ether giving the highest percentage extraction. The mean concentrations of PBDEs obtained ranged from ND to 2670pgl(-1), ND to 6638pgl(-1), ND to 7230pgl(-1), 41 to 4009pgl(-1), 90 to 9793pgl(-1) for the Garankuwa, Hatherly, Kwaggarsrand, Soshanguve and Temba landfill sites, respectively. Also BDE -28, -47, -71 and BDE-77 were detected in the leachate samples from all the landfill sites; and all the congeners were detected in two of the oldest landfill sites. The peak concentrations were recorded for BDE-47 at three sites and BDE-71 and BDE-75 at two sites. The highest concentration, 9793+/-1.5pgl(-1), was obtained for the Temba landfill site with the highest BOD value. This may suggest some influence of organics on the level of PBDEs. Considering the leaching characteristics of brominated flame retardants, there is a high possibility that with time these compounds may infiltrate into the groundwater around the sites since most of the sites are not adequately lined.     

Dose Assessment for Process Water Tunnels at Hanford Site

The RESRAD‐BUILD and RESRAD computer codes were used for dose assessment of the 105‐C Process Water Tunnels at the Hanford Site. The evaluation assessed three different exposure scenarios: recreational use, tunnel maintenance worker, and residential use. The recreationist and maintenance worker scenarios were evaluated by using RESRAD‐BUILD, a computer model for analyzing the radiological doses resulting from remediation and occupancy of structures contaminated with radioactive material. The recreationist was assumed to use the tunnels as an overnight shelter for eight hours per day for one week. The maintenance worker was assumed to spend 20 hours per year working in the the tunnel. Six exposure pathways were considered for both scenarios in dose assessment. The gradual removal of surface contamination over time and ingrowth of decay products were considered in calculating the dose at different times. The maximum dose would occur immediately after the release and was estimated to be 1.9 mrem/yr for the recreationist and 0.9 mrem/yr for the maintenance worker. The residential scenario was evaluated by using the probabilistic RESRAD code. It was assumed that total activity from the tunnels would be brought into the near‐surface layer by future human activities. Eight exposure pathways were considered. The maximum yearly dose for this very unlikely scenario would occur immediately after the release and was less than 4 mrem/yr for the maximally exposed individual. The assessment demonstrates that both codes are suitable for nuclear facility decontamination and decommissioning sites, where buildings and structures with residual radioactivity must be evaluated to facilitate property transfer or release.     

Case Study and Retrospective: Aerobic Fixed Film Biological Treatment Process for 1,4‐Dioxane at the Lowry Landfill Superfund Site

An aerobic fixed film biological treatment system has been successfully treating recovered groundwater/landfill leachate containing 1,4‐dioxane, tetrahydrofuran (THF), and other constituents since 2003. The most likely mode of 1,4‐dioxane biotransformation is via a cometabolic pathway in the presence of THF. Pilot studies conducted during the process development phase established a design basis process loading factor of 0.6 g 1,4‐dioxane and THF (as chemical oxygen demand [COD])/g total solids per day and proved the efficacy of the process. Full‐scale design includes the use of three parallel moving bed bioreactors with effluent recycle capability. Removal efficiencies in excess of 98 percent have been documented for 1,4‐dioxane. Evolving operational challenges are associated with recent trends in 1,4‐dioxane pretreatment discharge limitations in combination with ongoing process optimization and increased influent flow rate conditions associated with seasonal precipitation patterns. ©2016 Wiley Periodicals, Inc.     

Urban waterfowl population: Ecological evaluation of management and planning

An urban population of ducks in Puyallup, Washington, USA was studied for 14 consecutive months beginning in November 1978. Observations were made weekly from four study sites where ducks would congregate at early morning hours. Factors contributing to the presence of waterfowl in Puyallyup included abundant food supplies and a creek corridor that connected fragmented habitats in the urban area to the larger rural populations of waterfowl. Mallards (Anas platyrhynchos) were the most abundant of the 13 species observed and were the only ducks remaining during the nesting season. Habitat size and complexity were important factors influencing the species diversity of a particular site. Nesting success of mallards was poor due to limited distribution of nesting habitat, intraspecific aggression, and human disturbance. Both site-specific and more broad-based strategies are suggested for managing and planning for duck populations in urban areas.     

Runoff phosphorus losses as related to phosphorus source, application method, and application rate on a Piedmont soil

Land application of animal manures and fertilizers has resulted in an increased potential for excessive P losses in runoff to nutrient-sensitive surface waters. The purpose of this research was to measure P losses in runoff from a bare Piedmont soil in the southeastern United States receiving broiler litter or inorganic P fertilizer either incorporated or surface-applied at varying P application rates (inorganic P, 0-110 kg P ha(-1); broiler litter, 0-82 kg P ha(-1)). Rainfall simulation was applied at a rate of 76 mm h(-1). Runoff samples were collected at 5-min intervals for 30 min and analyzed for reactive phosphorus (RP), algal-available phosphorus (AAP), and total phosphorus (TP). Incorporation of both P sources resulted in P losses not significantly different than the unfertilized control at all application rates. Incorporation of broiler litter decreased flow-weighted concentration of RP in runoff by 97% and mass loss of TP in runoff by 88% compared with surface application. Surface application of broiler litter resulted in runoff containing between 2.3 and 21.8 mg RP L(-1) for application rates of 8 to 82 kg P ha(-1), respectively. Mass loss of TP in runoff from surface-applied broiler litter ranged from 1.3 to 8.5 kg P ha(-1) over the same application rates. Flow-weighted concentrations of RP and mass losses of TP in runoff were not related to application rate when inorganic P fertilizer was applied to the soil surface. Results for this study can be used by P loss assessment tools to fine-tune P source, application rate, and application method site factors, and to estimate extreme-case P loss from cropland receiving broiler litter and inorganic P fertilizers.