A microcosm system to evaluate the toxicity of the triazine herbicide simazine on aquatic macrophytes

This study evaluates the effects of the triazine herbicide simazine in an outdoor pond microcosm test system that contained two submerged rooted species (Myriophyllum spicatum and Elodea canadensis) and two emergent rooted species (Persicaria amphibia and Glyceria maxima) over a period of 84 days. Simazine was applied to the microcosms at nominal concentrations of 0.05, 0.5 and 5 mg/L. General biological endpoints and physiological endpoints were used to evaluate herbicide toxicity on macrophytes and the algae developing naturally in the system.Concentration-related responses of macrophytes and algae were obtained for the endpoints selected, resulting in a no observed ecologically adverse effect concentration (NOEAEC) at simazine concentrations of 0.05 mg active ingredient/L after 84 days. E. canadensis was the most negatively affected species based on length increase, which was consistently a very sensitive parameter for all macrophytes. The experimental design presented might constitute a suitable alternative to conventional laboratory single-species testing.     

Predicting diffuse-source transfers of surfactants to surface waters using SWAT

Chemicals present in domestic wastewater can adsorb to solid phase materials during sewage treatment. If biosolids (or sewage sludge) are applied to land, these chemicals can be transferred to soil. Under some circumstances they can also be transferred to surface waters during storm events either in solution or attached to sediment. In this paper we describe the utility of the SWAT 2000 model to estimate diffuse-source surface water exposure to "down-the-drain" chemicals. The model was applied hypothetically to predict the behaviour of linear alkylbenzene sulphonate (LAS), an anionic surfactant commonly used in household detergents, in a small catchment in Bedfordshire, UK, where it has previously been successfully validated for stream flow, sediments and pesticides. LAS transfers were estimated for two scenarios: (1) realistic and (2) reasonable worst case, based on assumptions on sludge application rates and the concentration of LAS in sludge. In addition, the sensitivity of the model output to the proportion of the catchment to which sludge is applied was established. Soil wetness and the total quantity of biosolids applied were the biggest determinants of chemical transport from the catchment. The potential of SWAT as a higher-tier tool in environmental risk assessments is discussed.     

Formation of artefacts while sampling emissions of PCDD/PCDF from open burning of biomass

Emission factors for PCDD/PCDF determined from open combustion are used to estimate national emission budgets; therefore, it is important to have confidence in their accuracy. It has been suspected that artefacts may form due to the presence of hot metal surfaces of sampling equipment, thus skewing emission factors. In this study, emissions of PCDD/PCDF from open burning of forest biomass over a brick hearth were sampled. Five experiments were carried out using a portable sampler. Experiments were designed where the key variable, sample hood and inlet temperatures were manipulated. Other variables such as fuel origin, type and density were consistent. The measured concentration of PCDD/PCDF in the smoke samples ranged from 0.01 μg TEQ (t fuel)⁻¹ at the lowest maximum hood temperature (185 °C) to 15 μg TEQ (t fuel)⁻¹ at the highest maximum hood temperature (598 °C). when hood inlet temperatures exceeded 400 °C emission factors were significantly elevated and this is attributed to the formation of artefacts that can cause the over estimation of emission factors. The increase in hood temperature also resulted in a change in the PCDD/PCDF congener and homologue profile of the emissions. For example at the lowest temperature (Fire 1) the PCDD/PCDF ratio measured was 50:1, whereas at the highest temperature (Fire 5) this ratio was about 0.53:1. When the sampler hood and inlet temperatures were kept in the normal operating range of <200 °C, emission factors were comparable to those observed in many previous studies in Australia with emissions dominated by PCDD.     

The Great Lakes Hydrography Dataset: Consistent,Binational Watersheds for the Laurentian Great Lakes Basin

Ecosystem‐based management of the Laurentian Great Lakes, which spans both the United States and Canada, is hampered by the lack of consistent binational watersheds for the entire Basin. Using comparable data sources and consistent methods, we developed spatially equivalent watershed boundaries for the binational extent of the Basin to create the Great Lakes Hydrography Dataset (GLHD). The GLHD consists of 5,589 watersheds for the entire Basin, covering a total area of approximately 547,967 km², or about twice the 247,003 km² surface water area of the Great Lakes. The GLHD improves upon existing watershed efforts by delineating watersheds for the entire Basin using consistent methods; enhancing the precision of watershed delineation using recently developed flow direction grids that have been hydrologically enforced and vetted by provincial and federal water resource agencies; and increasing the accuracy of watershed boundaries by enforcing embayments, delineating watersheds on islands, and delineating watersheds for all tributaries draining to connecting channels. In addition, the GLHD is packaged in a publically available geodatabase that includes synthetic stream networks, reach catchments, watershed boundaries, a broad set of attribute data for each tributary, and metadata documenting methodology. The GLHD provides a common set of watersheds and associated hydrography data for the Basin that will enhance binational efforts to protect and restore the Great Lakes.     

Exposure to bushfire smoke during prescribed burns and wildfires: firefighters' exposure risks and options

Firefighters are exposed to known health-damaging air pollutants present in bushfire smoke and poorly managed exposure can result in serious health issues. A better understanding of exposure levels and the major factors influencing exposures is crucial for the development of mitigation strategies to minimise exposure risks and adverse health impacts. This study monitored air toxics within the breathing zone of firefighters at prescribed burns and at wildfires in Australia. The results showed that exposure levels were highly variable, with higher exposures (sometimes exceeding occupational exposure standards) associated with particular work tasks (such as patrol and suppression) and with certain burn conditions. The majority of firefighter's exposures were at low and moderate levels (~60%), however considerable attention should be given to the high (~30%) and very high (6%) exposure risk situations for which acute and chronic health risks are very likely and for which control strategies should be developed and implemented to minimise health risks.     

Source-term development for a contaminant plume for use by multimedia risk assessment models

Multimedia modelers from the US Environmental Protection Agency (EPA) and US Department of Energy (DOE) are collaborating to conduct a comprehensive and quantitative benchmarking analysis of four intermedia models: MEPAS, MMSOILS, PRESTO, and RESRAD. These models represent typical analytically based tools that are used in human-risk and endangerment assessments at installations containing radioactive and hazardous contaminants. The objective is to demonstrate an approach for developing an adequate source term by simplifying an existing, real-world, ⁹⁰Sr plume at DOE's Hanford installation in Richland, WA, for use in a multimedia benchmarking exercise between MEPAS, MMSOILS, PRESTO, and RESRAD. Source characteristics and a release mechanism are developed and described; also described is a typical process and procedure that an analyst would follow in developing a source term for using this class of analytical tool in a preliminary assessment.     

The (un)common good: diverging justifications for wilderness making in a modified landscape

ABSTRACT

Wilderness is most often conceived as comprising large remote areas where evidence of human influence is slight. Little attention has been afforded to the study of wilderness ‘making’ in smaller landscapes that have been heavily modified by human activity. This paper addresses this knowledge deficit by employing the pragmatic sociology of Boltanski and Thévenot to analyse a case study of wilderness making in the west of Ireland. The application of this framework illustrates how contending positions on ‘why’ wilderness making should occur and ‘how’ it should be conducted reflect ethical frameworks rooted in different conceptions of the ‘common good’ presented by the idea of wilderness. The paper demonstrates the difficulties with developing such a new nature-based concept in the absence of conventional (received) ideas of wilderness by revealing how the diverging justifications used suggest incommensurability in the competing notions of wilderness that are formulated and advanced.     

The statistical merits of various methods of calculating transfer coefficients between environmental media--development of the ideal formula for data-sets with a log-normal distribution

The statistical treatment of data-sets from environmental pollutant studies in which different measurements are combined to produce averages or comparative factors (e.g., transfer coefficients (TCs), input-output balance values) are considered here, with particular reference to the analysis of data from input-output balance studies of pollutants such as PCBs in animals and humans. Many methods of statistical analysis ignore the fact that all measurements are subject to error, and generally assume that the normal distribution applies to all data-sets, which is commonly inappropriate for environmental (and particularly biological system) data. Considerably different estimations can be obtained by applying different, commonly used, statistical methods, as shown in a simulation study presented here and when applied to data from an input-output balance study of PCBs in humans. Alternative average and combined factor estimators for the treatment of data from these types of studies that give considerable advantages in terms of bias and the ease of assessment of accuracy are proposed.     

Trace metal partitioning in Thalassia testudinum and sediments in the Lower Laguna Madre, Texas

Seagrass communities dominate the Laguna Madre, which accounts for 25% of the coastal region of Texas. Seagrasses are essential to the health of the Laguna Madre (LM) and have experienced an overall decline in coverage in the Lower Laguna Madre (LLM) since 1967. Little is known on the existing environmental status of the LLM. This study focuses on the trace metal chemistry of four micronutrient metals, Fe, Mn, Cu, and Zn, and two non-essential metals, Pb and As, in the globally important seagrass Thalassia testudinum. Seasonal trends show that concentrations of most essential trace metals increase in the tissue during the summer months. With the exception of (1) Cu in the vertical shoot and root, and (2) Mn in the roots, no significant positive correlation exists between the rhizosphere sediment and T. testudinum tissue. Iron indicates a negative correlation between the morphological units and the rhizosphere sediments. No other significant relationship was found between the sediments and the T. testudinum tissue. Mn was enriched up to 10-fold in the leaf tissue relative to the other morphological units and also enriched relative to the rhizosphere sediments. Both Cu and Mn appear to be enriched in leaf tissue compared to other morphological units and also enriched relative to the Cu and Mn in the rhizoshpere sediments. Sediments cores taken in barren areas were slightly elevated in Zn relative to the rhizosphere sediments, whereas no other metals showed statistical differences between barren sediment cores and rhizosphere sediments. However, no correlation was measured in T. testudinum tissue and Zn in rhizosphere sediments. Previous studies suggested that Fe/Mn ratios could indicate differences between seagrass environments. Our results indicate that there is an influence from the Rio Grande in the Fe/Mn signature in sediments, and that ratio is not reflected in the T. testudinum tissue. The results from this study show that the LLM contains trace metal concentrations less than or equal to values for uncontaminated locations worldwide. In addition, there appears to be a complex partitioning in the trace metals in the morphological units of T. testudinum tissue and that analysis only of the leaf may not be indicative of the trace metal levels in this important seagrass species.