Holling's Figure-Eight Model: A Technical Reevaluation in Relation to Climate Change and Biodiversity

Holling proposed a four-phase conceptual model of ecosystem dynamics that includes exploitation, conservation, and destructive and renewal components to explain the failure of many natural resource management schemes. The model is drawn as a sideways figure-eight i.e. . There are two dimensions in this model, connectivity (abscissa) and the amount of capital stored in the system (ordinate). This conceptual model has been suggested as a guide to thinking about the impact of climate change on biodiversity, but the two dimensions are insufficient and the alignment of the figure-eight model is problematic when compared with actual data. Kay has adjusted the dimensions of the figure-eight model and renamed the abscissa as exergy stored and the ordinate as exergy consumed. We realign the original figure-eight model, labeling the abscissa as carbon stored and the ordinate as nutrients, such that the relative values of both axes are in qualitative agreement with data from four different studies. This new alignment is then shown to fit relatively well with Holling's original labels. This revision of the figure-eight model brings Holling's model into agreement with observations and provides insight into the linkages between biodiversity and climate change.     

Euro Chlor Risk Assessment for the Marine Environment Osparcom Region: North Sea - 1,2-Dichloroethane

This risk assessment on 1,2-dichloroethane (EDC) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 21 studies for fish, 17 studies for invertebrates and 7 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 1100 µg/l. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.5 µg EDC/l and a worst case PEC of 6.4 µg EDC/l. The calculated PEC/PNEC ratios give a safety margin of 170 to 2200 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.     

Euro Chlor Risk Assessment for the Marine Environment Osparcom Region: North Sea - Chloroform

This risk assessment on chloroform was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 23 studies for fish, 17 studies for invertebrates and 10 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a typical PNEC value of 72 µg/l. Due to limitations of the studies evaluated, a worst PNEC of 1 µg/l could also be used. Most of the available monitoring data apply to rivers and estuaries and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.2 µg chloroform per litre of water and a worst case PEC of 5 to 11.5 µg chloroform per litre of water. The calculated PEC/PNEC ratios give a safety margin of 6 to 360 between the predicted no effect concentration and the exposure concentrations. A worst case ratio, however, points to a potential risk for sensitive species. Refinement of the assessment is necessary by looking for more data. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.     

Euro Chlor Risk Assessment for the Marine Environment Osparcom Region: North Sea - Tetrachloroethylene

This risk assessment on tetrachloroethylene (PER) was carried out specifically for the marine environment, according to the methodology laid down in the EU risk assessment Regulation (1488/94) and the Guidance Document of the EU New and Existing Substances Regulation (TGD, 1997). The study consists of the collection and evaluation of data on effects and environmental concentrations from analytical monitoring programs in large rivers and estuaries in the North Sea area. The risk is indicated by the ratio of the "predicted environmental concentrations" (PEC) and the "predicted no effect concentrations" (PNEC) for the marine aquatic environment. In total, 18 studies for fish, 13 studies for invertebrates and 8 studies for algae have been evaluated. Both acute and chronic toxicity studies have been taken into account and the appropriate assessment factors have been used to define a PNEC value of 51 µg/l. Most of the available monitoring data apply to rivers and estuary waters and were used to calculate PECs. The most recent data (1991-1995) support a typical PEC of 0.2 µg PER/l water and a worst case PEC of 2.5 µg PER/l water. The calculated PEC/PNEC ratios give a safety margin of 20 to 250 between the predicted no effect concentration and the exposure concentration. Additional evaluation of environmental fate and bioaccumulation characteristics showed that no concern is expected for food chain accumulation.     

Sampling of epichlorohydrin and ethylene chlorohydrin in workroom air using Amberlite XAD-7 resin

Activated charcoal, Amberlite XAD-2 and Amberlite XAD-7 were evaluated for the adsorption of epichlorohydrin and ethylene chlorohydrin from air followed by desorption with solvent. Ethylene chlorohydrin was found to be unstable on activated charcoal in the presence of carbon disulfide. Recoveries from XAD-2 were low, and XAD-7 was found to be the best adsorbent for the sampling of these compounds from air.     

Detecting river pollution using fluorescence spectrophotometry: case studies from the Ouseburn,NE England

Recent advances in fluorescence spectrophotometry enable the analysis of river dissolved organic matter. We investigate the potential of detecting sewage pollution in a small, urbanised catchment. Downstream sampling highlighted a summer maximum in tryptophan fluorescence intensity during low flow. No correlation is observed between ammonia and tryptophan fluorescence intensity. In contrast, two sewage related point-pollution events had both high tryptophan fluorescence intensity and ammonia, suggesting that the summer tryptophan increase does not original from foul sewage. Sewage inputs to the river were therefore monitored at summer base flow. This demonstrated that > 10% of the rivers' discharge is provided by sewerage inputs and that these inputs could be grouped by their fluorescence and ammonia properties: (1) 'clean' storm waters with low ammonia and tryptophan intensity (2) 'grey' waters with high tryptophan intensity and low ammonia concentration, and (3) 'foul' waters with high tryptophan intensity and ammonia concentration. All three types of sewerage input occurred irrespective of flow conditions,suggesting that sewerage cross connections are occurring.     

Temperature effects on chlorinated-benzene sorption to hydrophobic surfaces

Sorption and desorption of chlorinated benzenes were investigated in a series of column experiments using porous silica that had phenyl groups bonded to the surface; the mass-fraction organic carbon was 0.016. Both sorption and desorption curves were asymmetrical, but they were mirror images of each other for most experiments, indicating good sorption reversibility. The resulting breakthrough curves were fit to an advection-dispersion mathematical model, with sorption as a first-order, reversible reaction. Significantly greater tailing in the chlorinated-benzene breakthrough curves versus the salt-tracer ones was evidence of slow sorption and desorption. ΔH° values for di-, tri- and tetra-chlorobenzene were 13–21 kJ mol₋₁, indicative of strong van der Waals binding. Despite these small values, slow desorption was attributed to slow binding and release rather than diffusion through the bonded organic phase. Desorption rates decreased in going from di- to tri- to tetra- to penta-chlorobenzene. This decrease was significantly more than the decrease in molecular-diffusion coefficients in the same series, suggesting a chemical rather than a physical rate control. There was less difference in sorption rates through the series, suggesting an inverse relation between partition coefficient and desorption rate. ΔG° values were −17 to −23 kJ mol⁻¹, giving TΔS° values of about 4 kJ mol⁻¹. Thus enthalpic contributions to sorption appear to be of greater importance than entropic contributions.     

Comparing estimates of fugitive landfill methane emissions using inverse plume modeling obtained with Surface Emission Monitoring (SEM), Drone Emission Monitoring (DEM), and Downwind Plume Emission Monitoring (DWPEM)

ABSTRACT

As part of the global effort to quantify and manage anthropogenic greenhouse gas emissions, there is considerable interest in quantifying methane emissions in municipal solid waste landfills. A variety of analytical and experimental methods are currently in use for this task. In this paper, an optimization-based estimation method is employed to assess fugitive landfill methane emissions. The method combines inverse plume modeling with ambient air methane concentration measurements. Three different measurement approaches are tested and compared. The method is combined with surface emission monitoring (SEM), above ground drone emission monitoring (DEM), and downwind plume emission monitoring (DWPEM). The methodology is first trialed and validated using synthetic datasets in a hand-generated case study. A field study is also presented where SEM, DEM and DWPEM are tested and compared. Methane flux during two-days measurement campaign was estimated to be between 228 and 350 g/s depending on the type of measurements used. Compared to SEM, using unmanned aerial systems (UAS) allows for a rapid and comprehensive coverage of the site. However, as showed through this work, advancement of DEM-based methane sampling is governed by the advances that could be made in UAS-compatible measurement instrumentations. Downwind plume emission monitoring led to a smaller estimated flux compared with SEM and DEM without information about positions of major leak points in the landfill. Even though, the method is simple and rapid for landfill methane screening. Finally, the optimization-based methodology originally developed for SEM, shows promising results when it is combined with the drone-based collected data and downwind concentration measurements. The studied cases also discovered the limitations of the studied sampling strategies which is exploited to identify improvement strategies and recommendations for a more efficient assessment of fugitive landfill methane emissions.

Implications: Fugitive landfill methane emission estimation is tackled in the present study. An optimization-based method combined with inverse plume modeling is employed to treat data from surface emission monitoring, drone-based emission monitoring and downwind plume emission monitoring. The study helped revealing the advantages and the limitations of the studied sampling strategies. Recommendations for an efficient assessment of landfill methane emissions are formulated. The method trialed in this study for fugitive landfill methane emission could also be appropriate for rapid screening of analogous greenhouse gas emission hotspots.     

Bioremediation of Stranded Oil on an Arctic Shoreline

The application of slow-release and soluble fertilizers proved to be an effective and environmentally benign way of stimulating oil biodegradation on an Arctic shoreline. Fertilizer application to the surface of the beach delivered nutrients to the oiled sediment beneath the beach surface. There was no significant run-off of this fertilizer to either the nearshore water or to unfertilized plots, and there were no adverse toxicological effects of the fertilizer application. The fertilizer application was followed by an increase in oxygen consumption and carbon dioxide evolution from the beach, increased microbial biomass, and significantly greater biodegradation of oil on the plots that had received fertilizer. The rate of oil biodegradation was approximately doubled over the course of a year by fertilizer applications in the first two months after the spill.Simple test kits proved adequate to monitor the fertilizer-application process in the field in a time frame that would allow the application process to be fine-tuned during treatment on a real spill. Simple test kits and portable instrumentation were useful in demonstrating the initial success of the bioremediation strategy.     

SELECTING GROUPS OF FISH TO OPTIMIZE ACQUISITION OF INFORMATION ON THERMAL DISCHARGES1

ABSTRACT: A national trend over the last 25 years has been to require increasing amounts of biological information on industrial waste discharges. Acquisition of this essential information frequently involves complex assessments. In order to optimize the value of information gathered and to minimize the cost of this information, it is essential that analyses of redundancy be accompanied by the determination of which groups of organisms give the most information relative to a particular problem. Studies of the effect of temperature on the fishes of the New River, Glen Lyn, Virginia, provide us with the opportunity to evaluate the redundancy of information relative to the influence of temperature on fish distribution. Information of this type will be useful in selecting groups of organisms for laboratory temperature preference and avoidance tests. It was shown that the distribution of three genera (Notropis, Micropterus, and Etheostoma) had the highest correlation with the distribution of the total fish fauna and, therefore, provided the most information relative to temperature selection of the New River ichthyofauna. The final temperature preferences of the most abundant species of Notropis and Micropterus were representative of the response of the entire fish community based on the distribution of diversity indices relative to temperature.