Taking advantage of aerated-anoxic operation in a full-scale University of Cape Town process.

To evaluate the potential benefits or limitations of aeratedanoxic operation in high-rate biological nutrient removal processes, we conducted a full-scale experiment in a University of Cape Town (UCT)-type wastewater treatment plant by reducing oxygen supply and increasing flowrates within one treatment train so that aerated-anoxic conditions (i.e., zones that receive oxygen but maintain dissolved oxygen concentrations below 0.5 mg/L) could be implemented in a section of the aerated zone. With this retrofitted configuration, total nitrogen removal increased from 54 to 65%, but was limited by the organic carbon available for denitrification. Furthermore, the significant reduction in dissolved oxygen concentrations in the aerated zone did not negatively affect enhanced biological phosphorus removal, demonstrating that the implementation of an aerated-anoxic zone within a UCT-type reactor can contribute to a reduction in operational costs and a slight improvement in total nitrogen removal, without compromising the extent of phosphorus removal.     

The effect of thermodynamic data on computer model predictions of uranium speciation in natural water systems

Computer models have found widespread application in order to help elucidate and predict changes in environmental systems. One such application is the prediction of trace metal speciation in aqueous systems. This is achieved by solving a set of non-linear equations involving equilibrium constants for all the components in the system, within mass and charge balance constraints. In this study a comparison of the predicted uranium speciation from two computer programs, WHAM and PHREEQCI, is used to illustrate the effect variations in thermodynamic data can have on the models produced. Using the original thermodynamic data provided with the models, WHAM predicted the UO2(2+) ion as the major species (84%) while PHREEQCI predicted UO2(HPO4)2(2-) as the major species (86%). Substituting uranium data from the Nuclear Energy Agency Thermochemical Database project (NEA-TDB) into both programs produced similar results from each program, with UO2F+ predicted to dominate (68%) in a groundwater sample. Natural water samples often contain humic substances. The possible interaction of such substances with uranium was also modelled. The WHAM program includes a discreet site electrostatic humic substance model, however in order to use the PHREEQCI program to model humic substance interactions, a 'model fulvic acid' dataset was added to the program. These models predicted 85 to 98% uranium-humic substance species at neutral pH. This indicates that humic substances do need to be taken into account when modelling uranium speciation in natural water samples.     

Uranium speciation in moorland river water samples: a comparison of experimental results and computer model predictions

An on-line method has been developed for separating inorganic and organic bound uranium species present in river water samples. The method utilised a small chelating resin (Hyphan) column incorporated into the sample introduction manifold of an ICP-MS instrument. The method was evaluated for samples from rivers on Dartmoor (Devon, UK), an area of granite overlain with peat bogs. The results indicate that organic-uranium species form a major proportion (80%) of the total dissolved uranium present. Further work with synthetic water samples indicated that the level of dissolved organic carbon played a greater role in determining the level of organic-uranium species than did sample pH. Computer models for the water samples were constructed using the WHAM program (incorporating uranium data from the Nuclear Energy Agency Thermochemical Database project) in order to predict the levels of organic-uranium species that would form. By varying the proportion of humic and fulvic acids used in the humic component, predictions within 10% of the experimental results were obtained. The program did exhibit a low bias at higher pH values (7.5) and low organic carbon concentrations (0.5 microg ml(-1)), but under the natural conditions prevalent in the Dartmoor water samples, the model predictions were successful.     

Metals, Boron, and Selenium in Neosho Madtom Habitats in the Neosho River in Kansas, U.S.A.

In 1991 and 1992 we determined the levels of metals, arsenic, boron, and selenium in the Neosho River drainage in southeastern Kansas, the primary habitat for the threatened Neosho madtom (Noturus placidus). We evaluated concentrations in sediments, mussels (Quadrula pustulosa and Q. metanevra), and fish(Percina phoxocephala, Cyprinus carpio,and Ictiobus bubalus) from three sites on theNeosho River and one site on the Cottonwood River. We also evaluated contaminant concentrations in C. carpio composite samples collected by theKansas Department of Health and Environment (KDHE)at two additional locations on the Neosho River in1990–92. Sediments were contaminated by lead. Concentrations of selenium, boron, and most metalsin mussels were low to normal for biota. Arseniclevels in mussels and fish suggest low-levelcontamination of biota. Aluminum, barium, manganeseand strontium concentrations were much higher inmussels than in fish. Five fish composite sampleshad cadmium concentrations that indicate chronicdeleterious effects on biota. Lead concentrationsin six fish samples were elevated. Mercuryconcentrations in most large fish compositesexceeded concentration for protection of animalsthat might consume them. We believe that reductionsin cadmium, lead, and mercury contamination, inparticular, would benefit aquatic life in theriver.     

Airborne emissions of mercury from municipal solid waste. II: potential losses of airborne mercury before landfill

Waste distribution and compaction at the working face of municipal waste landfills releases mercury vapor (Hg(o)) to the atmosphere, as does the flaring of landfill gas. Waste storage and processing before its addition to the landfill also has the potential to release Hg(o) to the air if it is initially present or formed by chemical reduction of Hg(II) to Hg(o) within collected waste. We measured the release of Hg vapor to the atmosphere during dumpster and transfer station activities and waste storage before landfilling at a municipal landfill operation in central Florida. We also quantified the potential contribution of specific Hg-bearing wastes, including mercury (Hg) thermometers and fluorescent bulbs, and searched for primary Hg sources in sorted wastes at three different landfills. Surprisingly large fluxes were estimated for Hg losses at transfer facilities (approximately 100 mg/hr) and from dumpsters in the field (approximately 30 mg/hr for 1000 dumpsters), suggesting that Hg emissions occurring before landfilling may constitute a significant fraction of the total emission from the disposal/landfill cycle and a need for more measurements on these sources. Reducing conditions of landfill burial were obviously not needed to generate strong Hg(o) signals, indicating that much of the Hg was already present in a metallic (Hg(o)) form. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(o), the entire waste mass acts as a source. Broken fluorescent bulbs and thermometers in dumpsters emitted Hg(o) at 10 to >100 microg/hr and continued to act as near constant sources for several days.     

Published case studies of waterborne disease outbreaks--evidence of a recurrent threat.

Residents of affluent nations are remarkably lucky to have high-quality, safe drinking water supplies that most residents of modem cities enjoy, particularly when considered in contrast to the toll of death and misery that unsafe drinking water causes for most of the world's population. Some may presume that drinking-water disease outbreaks are a thing of the past, but complacency can easily arise. A review of drinking water outbreaks in developed countries over the past 3 decades reveals some of the reasons why drinking water outbreaks keep occurring when society clearly has the means to prevent them. Prevention of future outbreaks does not demand perfection, only a commitment to learn from past mistakes and to act on what has been learned.     

Airborne emissions of mercury from municipal solid waste. I: new measurements from six operating landfills in Florida

Mercury-bearing material enters municipal landfills from a wide array of sources, including fluorescent lights, batteries, electrical switches, thermometers, and general waste; however, the fate of mercury (Hg) in landfills has not been widely studied. Using automated flux chambers and downwind atmospheric sampling, we quantified the primary pathways of Hg vapor releases to the atmosphere at six municipal landfill operations in Florida. These pathways included landfill gas (LFG) releases from active vent systems, passive emissions from landfill surface covers, and emissions from daily activities at each working face (WF). We spiked the WF at two sites with known Hg sources; these were readily detected downwind, and were used to test our emission modeling approaches. Gaseous elemental mercury (Hg(O)) was released to the atmosphere at readily detectable rates from all sources measured; rates ranged from approximately 1-10 ng m(-2) hr(-1) over aged landfill cover, from approximately 8-20 mg/hr from LFG flares (LFG included Hg(O) at microg/m3 concentrations), and from approximately 200-400 mg/hr at the WF. These fluxes exceed our earlier published estimates. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(O), the entire waste mass acts as a source. We estimate that atmospheric Hg releases from municipal landfill operations in the state of Florida are on the order of 10-50 kg/yr, substantially larger than our original estimates, but still a small fraction of current overall anthropogenic losses.     

Bird pollination of Canary Island endemic plants

The Canary Islands are home to a guild of endemic, threatened bird-pollinated plants. Previous work has suggested that these plants evolved floral traits as adaptations to pollination by flower specialist sunbirds, but subsequently, they appear to have co-opted generalist passerine birds as sub-optimal pollinators. To test this idea, we carried out a quantitative study of the pollination biology of three of the bird-pollinated plants, Canarina canariensis (Campanulaceae), Isoplexis canariensis (Veronicaceae) and Lotus berthelotii (Fabaceae), on the island of Tenerife. Using colour vision models, we predicted the detectability of flowers to bird and bee pollinators. We measured pollinator visitation rates, nectar standing crops as well as seed-set and pollen removal and deposition. These data showed that the plants are effectively pollinated by non-flower specialist passerine birds that only occasionally visit flowers. The large nectar standing crops and extended flower longevities (>10 days) of Canarina and Isoplexis suggests that they have evolved a bird pollination system that effectively exploits these low frequency non-specialist pollen vectors and is in no way sub-optimal. Seed set in two of the three species was high and was significantly reduced or zero in flowers where pollinator access was restricted. In L. berthelotii, however, no fruit set was observed, probably because the plants were self-incompatible horticultural clones of a single genet. We also show that, while all three species are easily detectable for birds, the orange Canarina and the red Lotus (but less so the yellow-orange Isoplexis) should be difficult to detect for insect pollinators without specialised red receptors, such as bumblebees. Contrary to expectations if we accept that the flowers are primarily adapted to sunbird pollination, the chiffchaff (Phylloscopus canariensis) was an effective pollinator of these species.     

Megafaunal-habitat associations at a deep-sea coral mound off North Carolina,USA

Deep-sea corals provide important habitat for many organisms; however, the extent to which fishes and other invertebrates are affiliated with corals or other physical variables is uncertain. The Cape Fear coral mound off North Carolina, USA (366–463 m depth, 33° 34.4′N, 76° 27.8′W) was surveyed using multibeam sonar and the Johnson-Sea-Link submersible. Multibeam bathymetric data (2006) were coupled with in situ video data (2002–2005) to define habitat associations of 14 dominant megafauna at two spatial scales. Results suggested greater habitat specificity of deep-reef fauna than previously documented, with fishes showing greater affinity for certain habitat characteristics than most invertebrates. High vertical profile, degree of coral coverage, and topographic complexity influenced distributions of several species, including Beryx decadactylus, Conger oceanicus, and Novodinia antillensis on the smaller scale (30 × 30 m). On the broad scale (170 × 170 m), several suspension feeders (e.g., N. antillensis, anemones), detritivores (Echinus spp.), and mesopelagic feeders (e.g., Beryx decadactylus, Eumunida picta) were most often found on the south-southwest facing slope near the top of the mound. Transient reef species, including Laemonema barbatulum and Helicolenus dactylopterus, had limited affiliations to topographic complexity and were most often on the mound slope and base. Megafauna at deep-water reefs behave much like shallow-water reef fauna, with some species strongly associated with certain fine-scale habitat attributes, whereas other species are habitat generalists. Documenting the degree of habitat specialization is important for understanding habitat functionality, predicting faunal distributions, and assessing the impacts of disturbance on deep-reef megafauna.     

Bottoms up: great bustards use the sun to maximise signal efficacy

Visual displays are signals that may be selected to increase visibility. Light is a crucial component in the transmission of visual signals, and white colour is very conspicuous when illuminated by sun and exhibited against darker backgrounds. Here we tested the hypothesis that orientation of sexual displays in male great bustard (Otis tarda) depends upon position of the sun, i.e., males direct their uplifted white tails towards the sun in order to maximise signal detectability to distant females. We recorded the orientation of 405 male displays in relation to the sun and to females at seven leks. Great bustard males signalled towards the sun more often than expected by chance in early morning, although this pattern was not obvious at other times of day, when males displayed more towards females. Our hypothesis was further supported by the fact that displays were more directed towards the sun when the sun was most visible. Males were more likely to direct their displays towards females during the most elaborate components of their courtship display and when there were fewer males on the lek. Pointing white plumage to the sun may be a behaviour selected in species living in steppe-like open landscapes if individuals obtain net fitness benefit by increasing the likelihood of mating.