Hydrogen peroxide stabilization in one-dimensional flow columns

Rapid hydrogen peroxide decomposition is the primary limitation of catalyzed H(2)O(2) propagations in situ chemical oxidation (CHP ISCO) remediation of the subsurface. Two stabilizers of hydrogen peroxide, citrate and phytate, were investigated for their effectiveness in one-dimensional columns of iron oxide-coated and manganese oxide-coated sand. Hydrogen peroxide (5%) with and without 25 mM citrate or phytate was applied to the columns and samples were collected at 8 ports spaced 13 cm apart. Citrate was not an effective stabilizer for hydrogen peroxide in iron-coated sand; however, phytate was highly effective, increasing hydrogen peroxide residuals two orders of magnitude over unstabilized hydrogen peroxide. Both citrate and phytate were effective stabilizers for manganese-coated sand, increasing hydrogen peroxide residuals by four-fold over unstabilized hydrogen peroxide. Phytate and citrate did not degrade and were not retarded in the sand columns; furthermore, the addition of the stabilizers increased column flow rates relative to unstabilized columns. These results demonstrate that citrate and phytate are effective stabilizers of hydrogen peroxide under the dynamic conditions of one-dimensional columns, and suggest that citrate and phytate can be added to hydrogen peroxide before injection to the subsurface as an effective means for increasing the radius of influence of CHP ISCO.     

Solid‐phase extraction and GC analyses of select agricultural pesticides and metabolites in stream water

Abstract

The occurrence of agricultural pesticides in surface waters around the USA has created a concern over the status of safe drinking water. Solid‐phase extraction (SPE) or liquid‐liquid extraction (LLE) is usually employed to concentrate trace levels of pesticides in water samples to concentrations that are measurable with advanced chromatographic instruments. We describe here a SPE and capillary gas chromatographic (GC) procedure to extract and concentrate trace levels of select agricultural pesticides and metabolites from stream water. Our SPE and GC method provides high sensitivity, with recoveries between 85% to 95%, and high reproducibility for 9 of the pesticides studied. The described method provided marginal recoveries of 19 and 60% for the atrazine metabolites.     

Dissolved phosphorus retention and release from a coastal plain in-stream wetland

Dissolved phosphorus (DP) can be released from wetlands as a result of flooding or shifts in water column concentrations. Our objectives were to determine the long-term (1460 d) DP retention and release characteristics of an in-stream wetland, and to evaluate how these characteristics respond to flooding, draining, and changes in DP concentrations. The studied in-stream wetland drains an agriculturally intensive subwatershed in the North Carolina Coastal Plain region. The wetland's DP retention and release characteristics were evaluated by measuring inflow and outflow DP concentrations, DP mass balance, and DP movement across the sediment-water column interface. Phosphorus sorption isotherms were measured to determine the sediment's equilibria P concentration (EPCo), and passive samplers were used to measure sediment pore water DP concentrations. Initially, the in-stream wetland was undersized (0.31 ha) and released 1.5 kg of DP. Increasing the in-stream wetland area to 0.67 ha by flooding resulted in more DP retention (28 kg) and low outflow DP concentrations. Draining the in-stream wetland from 0.67 to 0.33 ha caused the release of stored DP (12.1 kg). Shifts both in sediment pore water DP concentrations and sediment EPCo values corroborate the release of stored DP. Reflooding the wetland from 0.33 to 0.85 ha caused additional release of stored DP into the outflowing stream (10.9 kg). We conclude that for a time period, this in-stream wetland did provide DP retention. During other time periods, DP was released due to changes in wetland area, rainfall, and DP concentrations.     

Dissolved phosphorus export from an animal waste impacted in-stream wetland: response to tropical storm and hurricane disturbance

The ability of wetlands to retain P makes them an important landscape feature that buffers P movement. However, their P retention ability can be compromised through hydrologic disturbances caused by hurricanes and tropical storms (TS). This study had three objectives: (i) to determine the effects of hurricanes and TS on dissolved phosphorus (DP) concentrations and loads discharged from a Coastal Plain in-stream wetland (ISW); (ii) to evaluate shifts in P storage pools that would reflect P accretion/removal patterns; and (iii) to determine if relationships exist between storm characteristics with releases of DP and water volume. From January 1996 to October 1999, the ISW's outflow DP concentrations and flow volumes (Q) were measured and they were used to calculate DP mass export loads. In addition, the sediment total phosphorus (TP) concentrations were measured, and both the water column and sediment pore water DP concentrations were examined using passive samplers. In several instances, TS facilitated greater DP releases than a single hurricane event. The largest release of DP occurred in 1999 after Hurricanes Dennis, Floyd, and Irene. The large differences in DP exports among the storms were explained by Q variations. Storm activity also caused changes in sediment pore water DP and sediment TP concentrations. This study revealed that some TS events caused higher DP releases than a single hurricane; however, multiple hurricanes delivering heavy precipitation totals significantly increased DP export.     

Developing markets for recyclate: perspectives from south Wales

This paper introduces the problems of a market-driven waste management strategy in the UK and the momentum towards developing markets for recycled materials. It focuses on the demand side barriers and principally the need for market stimulation in the end uses for recyclables. The important role, which small- and medium-sized manufacturing enterprises (SMEs) have to play in developing existing markets for recyclate, is discussed. SMEs also have the potential to contribute to the radical new approach of identifying and developing a broad range of new, more diverse and higher value uses for recyclate. If these enterprises are to be engaged effectively then regional action is essential. The paper then reports on research work focusing on SMEs that has taken place as a component of the CWMRE (Creating Welsh Markets for REcyclate) market development initiative in Wales. As a foundation for this, a series of semi-structured interviews with SMEs has been conducted with those operating in sectors that are known to have the potential to provide novel applications for secondary materials or to have the potential for material displacement. Some of the barriers and corresponding needs within the case study companies involved are discussed. The implications of these findings for a regional market development programme are considered and in particular how these case studies support the need to engage SMEs in the use of secondary materials.     

Agonistic relationships between female mountain gorillas (Gorilla gorilla beringei)

Females in some mountain gorilla groups can be ranked on the basis of decided, non-aggressive approach-retreat interactions. However, data on four gorilla groups show that females do not form clear agonistic dominance hierarchies. Most aggressive interactions between females were undecided, and most dyads had undecided dominance relationships (Fig. 2). Females ignored aggression or responded to it aggressively more often than they responded submissively (Fig. 3). Moreover, directional inconsistency in aggression (including escalated contests) was high, and in some groups females showed significant bidirectionality in initiation of aggression (i.e., the more often they received aggression from partners, the more often they directed aggression at those partners; Fig. 4). Assigning ranks on the basis of aggressive interactions has limited power to explain variation in rates of initiating aggression and in responses and outcomes to aggression. Aggression was most common during feeding, but usually did not interrupt feeding bouts. It was proportionately more common in contexts that seem to involve competition for access to males (Figs 5, 6). This is consistent with the argument that females depend crucially on male services. As predicted by current models of female primate social relationships, agonistic relationships between gorilla females are unlike those typical in cercopithecine primates. They resemble those of some other primates and some equids in which contest competition for food is relatively unimportant and ecological costs of female transfer are low.     

Uptake of polycyclic aromatic hydrocarbons (PAHs) in salt marsh plants Spartina alterniflora grown in contaminated sediments

Polycyclic aromatic hydrocarbon (PAH) concentrations were measured in Spartina alterniflora plants grown in pots of contaminated sediment, plants grown in native sediment at a marsh contaminated with up to 900 microg/g total PAHs, and from plants grown in uncontaminated control sediment. The roots and leaves of the plants were separated, cleaned, and analyzed for PAHs. PAH compounds were detected at up to 43 microg/g dry weight in the root tissue of plants grown in pots of contaminated soil. PAH compounds were detected at up to 0.2 microg/g in the leaves of plants grown in pots of contaminated soil. Concentrations less than 0.004 microg/g were detected in the leaves of plants grown at a reference site. Root concentration factor (RCF) values ranged from 0.009 to 0.97 in the potted plants, and from 0.004 to 0.31 at the contaminated marsh site. Stem concentration factor (SCF) values ranged from 0.00004 to 0.03 in the potted plants and 0.0002 to 0.04 at the contaminated marsh. No correlation was found between the RCF value and PAH compound or chemical properties such as logKOW. SCF values were higher for the lighter PAHs in the potted plants, but not in the plants collected from the contaminated marsh. PAH concentrations in the roots of the potted plants are strongly correlated with soil concentrations, but there is less correlation for the roots grown in natural sediments. Additional plants were grown directly in PAH-contaminated water and analyzed for alkylated PAH homologs. No difference was found in leaf PAH concentrations between plants grown in contaminated water and control plants.     

The evolution of non-maternal caretaking among anthropoid primates: do helpers help?

Non-maternal infant care among nonhuman primates has frequently been investigated from the perspective of the caretaker. Here we examine whether allocaretaking behavior provides direct reproductive benefits to mothers. Comparative analyses that control for the effects of allometry and phylogeny reveal that allocaretaking behavior correlates with relatively fast infant growth and reproduction, but is not associated with the production of large infants. These results are consistent with those from studies of other taxa; primate helpers appear to increase the reproductive success of female breeders. In addition, our findings contrast with those derived from traditional allometric analyses and underscore the importance of controlling for the potentially confounding effects of phylogeny in comparative analyses. Received: 28 May 1996 / Accepted after revision: 16 November 1996     

In-Situ Fenton-Like Oxidation of Volatile Organics: Laboratory,Pilot, and Full-Scale Demonstrations

Laboratory, pilot, and full-scale experiments were used to evaluate and optimize the ISOTEC^SM remedial process at a warehousing facility in Union, New Jersey. Based on modified Fenton's oxidative chemistry, the ISOTEC^SM process uses a proprietary catalytic agent that delays formation of reactive hydroxyl radicals. This allows adequate dispersion of the hydroxyl radicals, which is an oxidizing agent, throughout a contaminant plume. Ground-water at the site was contaminated with high levels of gasoline and waste oil constituents, principally BTEX and MTBE. Bench scale microcosm studies were used to evaluate the appropriate site-specific stoichiometric relationships between catalyst, stabilizers, and oxidizers; the effect of contaminant type and concentration; and the pH optima. Based on results of the laboratory studies, a pilot-scale study was performed at the site. One injection point for catalyst, stabilizers, and oxidant was installed in the contaminated zone at the site, with one hydraulically connected downgradient well used for monitoring. A single treatment of the reagents in the optimal stoichiometry determined from the laboratory study was injected in-situ over a period of three days. A 98.5 percent reduction in volatile organics was observed in the area treated, with the radial extent of treatment estimated to be approximately 20 feet, based on the presence of hydroxyl radicals detected in hydraulically connected areas and at the surface. The full-scale process employed six injection points and three treatment cycles over a three-month period. Subsequent to treatment, contaminant levels were either nondetectable or were reduced to below applicable New Jersey groundwater standards, with regulatory closure on the site achieved in less than one year.     

The distribution of metals in the forest floor of aged conifer stands at a plantation in Northern England

The distribution of the elements Cd, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn has been examined in the horizons of soils under aged Sitka spruce (Picea sitchensis (Bong.) Carr.) stands at a plantation in Northern England. The stands are under first-generation cultivation and are up to 33 years old. Cadmium, Mn, Pb and Zn concentrations were consistently higher in the organic layers than in the underlying mineral soil. This contrasted with the situation for Sr and V. Cadmium, Pb and Zn all showed an increase in concentration in the L + F horizons with stand age and a corresponding increase in the difference between L + F horizon concentrations. Soil pH declined with increasing stand age. Cadmium, Cr, Pb and Zn were all present at higher concentrations in the F horizon than in any other, while Cu and Ni were relatively constant through all the horizons studied. For all nine elements, the H horizon was the largest store of the three organic layers. Calculated rates of accumulation of Cd, Pb and Zn in the L + F horizons gave good agreement with estimated regional atmospheric deposition rates. In comparison to atmospheric deposition, biological mobilisation and deposition of Cd, Pb and Zn make a relatively minor contribution to the surface soil metal burden. Cadmium appeared to be the most readily leached of these three metals from the forest floor, although some transfer of atmospherically-derived Pb to the H+ soil horizons was indicated.