The containment of toxic wastes: II. Metal movement in leachate and drainage at Parc lead-zinc mine, North Wales

Nant Gwydyr, a tributary of the River Conwy in North Wales, has been affected by metal wastes, from a lead and zinc mine, Parc Mine, through contaminated mine drainage waters and episodal erosion of an unstable tailings heap. From 1954 when the mining operation was discontinued to 1978 when a reclamation programme aimed to stabilise the tailings was accomplished, 13 000 tonnes of metalliferous spoil, containing 43 tonne Pb, 104 tonne Zn, and 1 tonne Cd was eroded from the main tailings dam. Dispersal and redeposition during flood events caused extensive pollution of the agricultural land of the flood plain. Analysis of the present water quality of the Nant Gwydyr, 14 years after the stabilisation work, shows that although there has been a marked improvement and no particulate matter is released, the Nant Gwydyr is still a polluted stream. Under normal discharge conditions, it contributes approximately 1 tonne of Zn, 0.2 tonne of Pb and 0.05 tonne of Cd per year to the River Conwy. Most of this originates from water issuing from the mine adit which has been impossible to control. There is still, however, a major contribution by the leachate from the tailings heap, because the stabilisation method used does not prevent this. The control of pollution in mine drainage is discussed.     

Applications of GPS-tracked personal and fixed-location PM2.5 continuous exposure monitoring

Continued development of personal air pollution monitors is rapidly improving government and research capabilities for data collection. In this study, we tested the feasibility of using GPS-enabled personal exposure monitors to collect personal exposure readings and short-term daily PM_2.5 measures at 15 fixed locations throughout a community. The goals were to determine the accuracy of fixed-location monitoring for approximating individual exposures compared to a centralized outdoor air pollution monitor, and to test the utility of two different personal monitors, the RTI MicroPEM V3.2 and TSI SidePak AM510. For personal samples, 24-hr mean PM_2.5 concentrations were 6.93 μg/m³ (stderr = 0.15) and 8.47 μg/m³ (stderr = 0.10) for the MicroPEM and SidePak, respectively. Based on time–activity patterns from participant journals, exposures were highest while participants were outdoors (MicroPEM = 7.61 µg/m³, stderr = 1.08, SidePak = 11.85 µg/m³, stderr = 0.83) or in restaurants (MicroPEM = 7.48 µg/m³, stderr = 0.39, SidePak = 24.93 µg/m³, stderr = 0.82), and lowest when participants were exercising indoors (MicroPEM = 4.78 µg/m³, stderr = 0.23, SidePak = 5.63 µg/m³, stderr = 0.08). Mean PM_2.5 at the 15 fixed locations, as measured by the SidePak, ranged from 4.71 µg/m³ (stderr = 0.23) to 12.38 µg/m³ (stderr = 0.45). By comparison, mean 24-h PM_2.5 measured at the centralized outdoor monitor ranged from 2.7 to 6.7 µg/m³ during the study period. The range of average PM_2.5 exposure levels estimated for each participant using the interpolated fixed-location data was 2.83 to 19.26 µg/m³ (mean = 8.3, stderr = 1.4). These estimated levels were compared with average exposure from personal samples. The fixed-location monitoring strategy was useful in identifying high air pollution microclimates throughout the county. For 7 of 10 subjects, the fixed-location monitoring strategy more closely approximated individuals’ 24-hr breathing zone exposures than did the centralized outdoor monitor. Highlights are: Individual PM_2.5 exposure levels vary extensively by activity, location and time of day; fixed-location sampling more closely approximated individual exposures than a centralized outdoor monitor; and small, personal exposure monitors provide added utility for individuals, researchers, and public health professionals seeking to more accurately identify air pollution microclimates.

Implications: Personal air pollution monitoring technology is advancing rapidly. Currently, personal monitors are primarily used in research settings, but could they also support government networks of centralized outdoor monitors? In this study, we found differences in performance and practicality for two personal monitors in different monitoring scenarios. We also found that personal monitors used to collect outdoor area samples were effective at finding pollution microclimates, and more closely approximated actual individual exposure than a central monitor. Though more research is needed, there is strong potential that personal exposure monitors can improve existing monitoring networks.     

Analysis and application of forest fuels data

Recent advances in fire modeling permit quantitative estimations of fire behavior from quantitative inputs that describe the fuel array and conditions, such as weather and site data, under which it will burn. This paper describes the collection, analysis, and stratification of flammable forest fuels data for coniferous forest ecosystems in Montana and then illustrates the resource management application of these data in three areas: the development of the fire behavior model, a determination of the model's sensitivity to input errors as reflected by fire behavior prediction errors, and the development of a fire hazard simulator (TAROT). A new integrated stand simulator, GANDALF, is highlighted.Conclusions center on the need to integrate fire management into the land management planning decision-making process.This work was supported by a USDI National Park Service contract to Gradient Modeling, Inc., a nonprofit research foundation devoted to ecologic research and resource management applications, and by cooperative aid agreements between Gradient Modeling, Inc. and the USDA Forest Service, Intermountain Forest and Range Experiment Station, Northern Forest Fire Laboratory (Fire in Multiple Use Management, R, D, and A Program).     

Why do snakes have eyes? The (non-)effect of blindness in island tiger snakes (Notechis scutatus)

Large (to >1 m), diurnally active tiger snakes (Notechis scutatus) are abundant on Carnac Island, near the coast of Western Australia. Our behavioural and mark-recapture studies provide the first ecological data on this population, and reveal a surprising phenomenon. Many adult tiger snakes have had their eyes destroyed, apparently during nest defence, by silver gulls (Larus novaehollandiae). This loss of vision did not reduce the snakes' body condition (mass relative to length), or their rates of growth or survival (measured over a 12-month period). Blind male snakes trail-followed females, and mated successfully. Thus, destruction of a major sensory modality had no detectable effect on these predators. This result is strongly counter-intuitive, but mirrors an earlier report of congenital blindness (without ill-effects) in American viperid snakes. Similarities between the two systems (island populations, highly venomous snakes, reliance on sessile prey) clarify the circumstances under which the loss of vision does not reduce an organism's viability. These natural experiments support Gans' hypothesis of “momentarily excessive construction” in that the snakes possess a complex organ system that they do not actually require for successful feeding, survival or reproduction. Received: 30 November 1998 / Received in revised form: 24 April 1999 / Accepted: 9 May 1999     

Erosion vs. recovery of coral reefs after 1998 El Niño: Chagos reefs, Indian Ocean

Three years after most corals died on the central Indian Ocean reefs of Chagos, erosion and recovery were studied to 30 m depth. Mortality was near-total to 15 m deep in northern atolls, and to > 35 m in central and southern atolls. Some reef surfaces have 'dropped' 1.5 m due to the loss of dense coral thickets. Coral bioerosion is substantial, reducing 3-D reef 'structure' and forming unconsolidated rubble. Juvenile corals are abundant, though mostly on eroding or unstable substrates, and are of less robust species. Reef fish abundance and diversity at 15 m depth remains high; species dependent on corals have diminished, while some herbivores and detritivores have increased. A new sea surface temperature (SST) data set shows that mean SST has risen 0.65 degree C since 1950. The critical SST causing the mortality in Chagos was 29.9 degrees C.     

Measurement error causes scale-dependent threshold erosion of biological signals in animal movement data.

Recent advances in telemetry technology have created a wealth of tracking data available for many animal species moving over spatial scales from tens of meters to tens of thousands of kilometers. Increasingly, such data sets are being used for quantitative movement analyses aimed at extracting fundamental biological signals such as optimal searching behavior and scale-dependent foraging decisions. We show here that the location error inherent in various tracking technologies reduces the ability to detect patterns of behavior within movements. Our analyses endeavored to set out a series of initial ground rules for ecologists to help ensure that sampling noise is not misinterpreted as a real biological signal. We simulated animal movement tracks using specialized random walks known as Lévy flights at three spatial scales of investigation: 100-km, 10-km, and 1-km maximum daily step lengths. The locations generated in the simulations were then blurred using known error distributions associated with commonly applied tracking methods: the Global Positioning System (GPS), Argos polar-orbiting satellites, and light-level geolocation. Deviations from the idealized Lévy flight pattern were assessed for each track after incrementing levels of location error were applied at each spatial scale, with additional assessments of the effect of error on scale-dependent movement patterns measured using fractal mean dimension and first-passage time (FPT) analyses. The accuracy of parameter estimation (Lévy mu, fractal mean D, and variance in FPT) declined precipitously at threshold errors relative to each spatial scale. At 100-km maximum daily step lengths, error standard deviations of > or = 10 km seriously eroded the biological patterns evident in the simulated tracks, with analogous thresholds at the 10-km and 1-km scales (error SD > or = 1.3 km and 0.07 km, respectively). Temporal subsampling of the simulated tracks maintained some elements of the biological signals depending on error level and spatial scale. Failure to account for large errors relative to the scale of movement can produce substantial biases in the interpretation of movement patterns. This study provides researchers with a framework for understanding the limitations of their data and identifies how temporal subsampling can help to reduce the influence of spatial error on their conclusions.     

Managing an Endangered Asian Bovid in an Australian National Park: The Role and Limitations of Ecological-Economic Models in Decision-Making

Should north Australia’s extensive populations of feral animals be eradicated for conservation, or exploited as a rare opportunity for Indigenous enterprise in remote regions? We examine options for a herd of banteng, a cattle species endangered in its native Asian range but abundant in Garig Gunak Barlu National Park, an Aboriginal land managed jointly by traditional owners and a conservation agency in the Northern Territory of Australia. We reflect on the paradoxes that arise when trying to deal effectively with such complex and contested issues in natural resource management using decision-support tools (ecological-economic models), by identifying the trade-offs inherent in protecting values whilst also providing incomes for Indigenous landowners.     

Using diatoms to assess the impacts of prehistoric, pre-industrial and modern land-use on Danish lakes

The impact of contemporary agriculture on Danish lakes is acknowledged to be extreme. In particular, high loading of nutrients from agricultural soils contributes to the eutrophic conditions found in many of Denmark’s lakes. Palaeolimnological studies have shown that human disturbance of the Danish landscape since the introduction of agriculture around 6,000 years ago has had a major impact on lake ecosystems. The European Union’s Water Framework Directive requires an evaluation of reference conditions for lakes, the conditions expected with only minimal human impact. Monitoring data and palaeolimnological studies of Danish lakes demonstrate that many of the most detrimental effects of eutrophication have been experienced in recent decades. A new study has suggested that the reference status for Danish lakes may be set to the status in ad 1850–1900, probably providing attainable, realistic restoration targets for many sites. The aims of this study were to explore the impacts of past and contemporary land-use on Danish lakes, and to consider how appropriate the use of 1850 as a date to define reference status is for these sites. Catchment land-cover data for ad 1800, taken from historical maps, and sedimentary diatom assemblages of the same age, from dated sediment cores, were used to assess the impact of pre-industrial land-use on 20 Danish lakes. Analysis of contemporary land-cover data and surface-sediment diatom assemblages for the 20 sites was also made. In-lake total phosphorus (TP) concentrations were estimated using the sedimentary diatom assemblages and an existing calibration dataset for Danish lakes. The percentage of the lake catchment that was agricultural land in ad 1800 explained 8.8% of the total variation in the diatom data. The land-cover variables ‘built-up areas’ and ‘plantations’, together explained 16.9% of the variation in the diatom data for the modern samples. Diatom-inferred TP concentrations were high for both ad 1800 (mean 112 μg TP L⁻¹) and the present (mean 122 μg TP L⁻¹), the latter estimates reflecting efforts in recent decades to reduce nutrient loading to Danish lakes following very high levels of nutrient enrichment post-1950. The data presented highlight the impact that human activities 200 years ago, particularly agriculture, had on Danish lake systems. The long cultural history and major anthropogenic disturbance of the Danish landscape mean that true reference conditions for lakes (or ‘baseline’ conditions, those found prior to human impacts) can be found only by considering century to millennial timescales.