Canada Country Study

human development, climate change

The implications of household greywater treatment and reuse for municipal wastewater flows and micropollutant loads

An increasing worldwide interest in water recycling technologies such as greywater treatment and reuse suggests that additional research to elucidate the fate of xenobiotics during such practices would be beneficial. In this paper, scenario analyses supported by empirical data are used for highlighting the potential fate of a selection of xenobiotic micropollutants in decentralised greywater treatment systems, and for investigation of the possible implications of greywater recycling for the wider urban water cycle. Potential potable water savings of up to 43% are predicted for greywater recycling based on Danish water use statistics and priority substance monitoring at a greywater treatment plant in Denmark. Adsorption represents an important mechanism for the removal of cadmium, nickel, lead and nonylphenol from influent greywater and therefore the disposal route adopted for the generated sludge can exert a major impact on the overall efficiency and environmental sustainability of greywater treatment

Problems in design of stroke treatment trials

Critical evaluation of the literature was use to identify remediable flaws in the design of clinical trials of stroke treatment. Trials of dexamethasone, dextran, and glycerol were reviewed. Available studies have in common major weaknesses in case selection (failure to exclude arteriolar strokes due to hemorrhage or lacunar infarction), and failure to estimate required sample size. Problems of case selection can be avoided with computerized tomography; the sample size required to show superiority of active treatment over placebo can be estimated using standard formulas. Prognostic stratification is suggested as a method of overcoming problems of unbalanced allocation. Further studies with improved design are required to evaluate the prospects for medical limitation of cerebral infarct size. © 1982 American Heart Association, Inc

How climate controls the flux of nitrogen by the Mississippi River and the development of hypoxia in the Gulf of Mexico

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110015/1/lno20075220856.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/110015/2/0856a1.pd

Quasiperiodic graphs: structural design, scaling and entropic properties

A novel class of graphs, here named quasiperiodic, are constructed via application of the Horizontal Visibility algorithm to the time series generated along the quasiperiodic route to chaos. We show how the hierarchy of mode-locked regions represented by the Farey tree is inherited by their associated graphs. We are able to establish, via Renormalization Group (RG) theory, the architecture of the quasiperiodic graphs produced by irrational winding numbers with pure periodic continued fraction. And finally, we demonstrate that the RG fixed-point degree distributions are recovered via optimization of a suitably defined graph entropy

Scientific Advocacy: A Tool for Assessing the Risks of Engagement

Scientists active in the public sphere recognize the importance of broader communications but sometimes have an incomplete or exaggerated view of the risks to both their public and professional reputations as a function of their advocacy. These risks are connected fundamentally to the degree that the advocacy positions they take are based on values that are shared (or not) with their audiences. An encapsulation of the connections between Risks, Advocacy, and Values in Engagement (RAVE) may help inform choices that public scientists must make

Sludge management paradigms: impact of priority substances and priority hazardous substances

As a by-product of treatment processes, municipal wastewater treatment plants (WWTP) generate large quantities of sludge, with sludge treatment focused on sterilisation, volume reduction and biogas production. Whilst the EU Sewage Sludge Directive sets limits on the concentrations of selected metals in sludge applied to agricultural land, the potential impact of many EU Water Framework Directive priority and priority hazardous substances (PS/PHS) on human or environmental health has yet to be fully addressed. Research presented here shows that treated sludge from five urban WWTPs experiencing differing local conditions contain a range of PS/PHS including substances whose use has been banned or heavily restricted. Concentrations reported in this study do not exceed the limit values set for the four PS/PHS currently included in the EU Sewage Sludge Directive. However, more stringent national limits are exceeded. The basis for developing and applying Predicted No Effect Concentration (PNEC) values for the application of sludge to agricultural land is still unclear. However, comparison between PS/PHS sludge concentrations and available PNEC soil values clearly indicate the need for further research. Implications and research priorities arising from these findings in terms of achieving compliance with EU Sewage Sludge and Water Framework Directives are discussed

The relationship between macroalgae taxa and human disturbance on central Pacific coral reefs

Climate change and human disturbance threatens coral reefs across the Pacific, yet there is little consensus on what characterizes a “healthy” reef. Benthic cover, particularly low coral cover and high macroalgae cover, are often used as an indicator of reef degradation, despite uncertainty about the typical algal community compositions associated with either near-pristine or damaged reefs. In this study, we examine differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analysing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands. Our results show that total macroalgae cover indicators of reef degradation may mask the influence of local human disturbance, with different taxa responding to disturbance differently. Identifying macroalgae to a lower taxonomic level (e.g. the genus level) is critical for a more accurate measure of Pacific coral reef health

Power-laws in recurrence networks from dynamical systems

Recurrence networks are a novel tool of nonlinear time series analysis allowing the characterisation of higher-order geometric properties of complex dynamical systems based on recurrences in phase space, which are a fundamental concept in classical mechanics. In this Letter, we demonstrate that recurrence networks obtained from various deterministic model systems as well as experimental data naturally display power-law degree distributions with scaling exponents $\gamma$ that can be derived exclusively from the systems' invariant densities. For one-dimensional maps, we show analytically that $\gamma$ is not related to the fractal dimension. For continuous systems, we find two distinct types of behaviour: power-laws with an exponent $\gamma$ depending on a suitable notion of local dimension, and such with fixed $\gamma=1$.Comment: 6 pages, 7 figure