Stochastic modelling of landfill leachate and biogas production incorporating waste heterogeneity. Model formulation and uncertainty analysis

A mathematical model simulating the hydrological and biochemical processes occurring in landfilled waste is presented and demonstrated. The model combines biochemical and hydrological models into an integrated representation of the landfill environment. Waste decomposition is modelled using traditional biochemical waste decomposition pathways combined with a simplified methodology for representing the rate of decomposition. Water flow through the waste is represented using a statistical velocity model capable of representing the effects of waste heterogeneity on leachate flow through the waste. Given the limitations in data capture from landfill sites, significant emphasis is placed on improving parameter identification and reducing parameter requirements. A sensitivity analysis is performed, highlighting the model's response to changes in input variables. A model test run is also presented, demonstrating the model capabilities. A parameter perturbation model sensitivity analysis was also performed. This has been able to show that although the model is sensitive to certain key parameters, its overall intuitive response provides a good basis for making reasonable predictions of the future state of the landfill system. Finally, due to the high uncertainty associated with landfill data, a tool for handling input data uncertainty is incorporated in the model's structure. It is concluded that the model can be used as a reasonable tool for modelling landfill processes and that further work should be undertaken to assess the model's performance.     

Ecological implications of anti-pathogen effects of tropical fungal endophytes and mycorrhizae

We discuss studies of foliar endophytic fungi (FEF) and arbuscular mycorrhizal fungi (AMF) associated with Theobroma cacao in Panama. Direct, experimentally controlled comparisons of endophyte free (E-) and endophyte containing (E+) plant tissues in T. cacao show that foliar endophytes (FEF) that commonly occur in healthy host leaves enhance host defenses against foliar damage due to the pathogen (Phytophthora palmivora). Similarly, root inoculations with commonly occurring AMF also reduce foliar damage due to the same pathogen. These results suggest that endophytic fungi can play a potentially important mutualistic role by augmenting host defensive responses against pathogens. There are two broad classes of potential mechanisms by which endophytes could contribute to host protection: (1) inducing or increasing the expression of intrinsic host defense mechanisms and (2) providing additional sources of defense, extrinsic to those of the host (e.g., endophyte-based chemical antibiosis). The degree to which either of these mechanisms predominates holds distinct consequences for the evolutionary ecology of host-endophyte-pathogen relationships. More generally, the growing recognition that plants are composed of a mosaic of plant and fungal tissues holds a series of implications for the study of plant defense, physiology, and genetics.     

Protection of workers’ mental health in Québec: Do general duty clauses allow labour inspectors to do their job?

Given that no specific provisions of the Occupational Health and Safety (OHS) Act explicitly deal with psychosocial risk factors, in Québec, occupational health and safety inspectors employed by the Commission de la santé et de la sécurité du travail (CSST) address psychosocial hazards under the Act’s general duty clause. This general duty clause and related provisions require that all employers eliminate hazards at source and protect the health of workers. More specifically, they are required to ensure that the organisation of work does not adversely affect the safety or health of the worker. Since 2004, Québec minimum standards legislation has also provided for the right of workers to an environment that is free from psychological harassment.Written from both a legal and public health perspective, this paper has two primary objectives: first, to better understand the potential and limits of the current legislative framework for the protection of the mental health of workers and second, to describe how scientific knowledge related to high risk situations for the mental health of workers might inform interventions by inspectors for the protection of workers’ mental health.     

The drivers of greenhouse gas emissions: What do we learn from local case studies?

Abstract

What can local case studies contribute to our understanding of the processes underlying the growth in greenhouse gas emissions? Since much abatement and mitigation are local in character, it is important that policy makers identify the mix of local, national and international processes that contribute to changes in greenhouse gas emissions. Drawing upon the results of case studies in Kansas, North Carolina and Ohio, how patterns of emissions in local areas can be connected analytically to the driving forces of environmental change is demonstrated. Emissions at the local level are empirically associated with the same set of trends found at national and international scale, namely, changes in population, affluence‐consumption and technology.     

Relationship of life-history patterns to depth in deep-water caridean shrimps (Crustacea: Natantia)

Deep-water shrimps, distributed on the steep outer reef slopes of tropical Pacific Islands, were obtained by setting baited traps in depths down to 850 m in the vicinity of Laucala Bay, Fiji, over the period 1979 to 1983. Life-history variables were estimated and interspecific comparisons made between Parapandalus serratifrons, Plesionika longirostris, Heterocarpus ensifer, H. gibbosus, H. sibogae, H. laevigatus (Pandalidae) and Saron marmoratus (Hippolytidae) which have different depth distributions. Results suggested that, interspecifically, reproductive lifespan tended to increase with increasing depth of distribution and that mean egg sizes of each species increased with increasing depth. Brood sizes tended to increase inconsistently with depth, although relative brood size (number of eggs per “standar” 15 g individual) appeared unrelated to depth. Although annual reproductive effort varied inconsistently with depth, reproductive effort totalled over the lifespan of the Heterocarpus species tended to increase with increasing depth. Some of the findings are counter to competition-based ecological theory, and it is proposed that adult predation decreases with increasing depth, allowing deeper-water species to have an extended lifespan, an increased degree of iteroparity, and a corresponding increase in lifetime reproductive effort. Further, we suggest that the probabilities of larval survival, which appear to decrease with increasing depth, are offset by the production of larger eggs by deeper-water species.     

A High Performance Liquid Chromatographic Determination of Free Amino Acids in Natural Waters in the Picomolar (M X 10-12) Range Suitable for Shipboard Use

A reliable method for the determination of amino acids, suitable for routine shipboard use, is presented. Using reverse-phase high-performance liquid chromatography with computer-controlled gradient elution optimization, the amino acids commonly found in sea-water were clearly resolved and determined at the picomole level. A procedure was also developed to enable repeat injections of sea water samples to be made without deterioration of column material or performance. Thus the analysis was made more operator-independent and consequently more suitable for use at sea.     

Amino Acids in Sea Water

Free amino acids in the waters of the English Channel have been measured over a twelve month period using a newly developed field technique. Samples have been taken over a wide area both from the surface and at depth. The results show that the levels of amino acids found in these studies are greater than those previously generally accepted. These findings are of considerable importance in productivity studies since amino nitrogen as a source of nutrient for phytoplankton has been largely neglected. This paper shows that the levels of amino acids in the upper layers of the sea are not insignificant and should not be disregarded as an alternative nitrogen source for phytoplankton.