Priority organic micropollutants in water sources in Flanders and the Netherlands and assessment of removal possibilities with nanofiltration

The occurrence of organic micropollutants in ground- and surface waters has become an important concern for the drinking water industry, mainly because of possible related health effects. Due to the polar nature of some of these pollutants, they are not completely removed by traditional water treatment barriers. This paper offers an overview of priority organic micropollutants and their occurrence in Flemish and Dutch water sources. Furthermore, rejection by nanofiltration is qualitatively predicted for the selected priority micropollutants. The qualitative prediction is based on the values of key solute and membrane parameters in nanofiltration. Predicted values are then compared with experimental values obtained from literature. Overall, the qualitative predictions are roughly in agreement with literature values. Prediction based on key parameters may thus prove to be a very quick and useful technique to assess the implementation of nanofiltration as a treatment step for organic micropollutants in drinking water plant design.     

Soil Aquifer Treatment (SAT) as a Natural and Sustainable Wastewater Reclamation/Reuse Technology: Fate of Wastewater Effluent Organic Matter (EfOM) and Trace Organic Compounds

Through the use of innovative analytical tools, the removal/transformation of wastewater effluent organic matter (EfOM) have been tracked through soil aquifer treatment (SAT). While the total amount of EfOM is significantly reduced by SAT, there are trends of shorter term versus longer term removals of specific EfOM fractions. The preferential removal of non-humic components (e.g., proteins, polysaccharides) of EfOM occurs over shorter travel times/distances while humic components (i.e., humic substances) are removed over longer travel times/distances, with the removal of both by sustainable biodegradation. Dissolved organic nitrogen (DON), a surrogate for protein-like EfOM, is also effectively removed over shorter term SAT. There is some background humic-like natural organic matter (NOM), associated with the drinking water source within the watershed, that persists through SAT. While most effluent-derived trace organic compounds are removed to varying degrees as a function of travel time and redox conditions, a few persist even through longer term SAT.     

Alternative prey and the dynamics of intraguild predation: theoretical perspectives

A rich body of theoretical literature now exists focused on the three-species module of intraguild predation (IGP), in which a top predator both attacks and competes with an intermediate predator. Simple models of intraguild predation are often unstable, either because one consumer is excluded, or because sustained oscillations emerge from long feedback loops. Yet, many natural IGP systems robustly persist. Standard models of intraguild predation simplify natural systems in crucial ways that could influence persistence; in particular, many empirical IGP systems are embedded in communities with alternative prey species. We briefly review the key conclusions of standard three-species IGP theory, and then present results of theoretical explorations of how alternative prey can influence the persistence and stability of a focal intraguild predation interaction.     

Manipulating decay time for efficient large-mammal density estimation: gorillas and dung height

Large-mammal surveys often rely on indirect signs such as dung or nests. Sign density is usually translated into animal density using sign production and decay rates. In principle, such auxiliary variable estimates should be made in a spatially unbiased manner. However, traditional decay rate estimation methods entail following many signs from production to disappearance, which, in large study areas, requires extensive travel effort. Consequently, decay rate estimates have tended to be made instead at some convenient but unrepresentative location. In this study we evaluated how much bias might be induced by extrapolating decay rates from unrepresentative locations, how much effort would be required to implement current methods in a spatially unbiased manner, and what alternate approaches might be used to improve precision. To evaluate the extent of bias induced by unrepresentative sampling, we collected data on gorilla dung at several central African sites. Variation in gorilla dung decay rate was enormous, varying by up to an order of magnitude within and between survey zones. We then estimated what the effort-precision relationship would be for a previously suggested "retrospective" decay rate (RDR) method, if it were implemented in a spatially unbiased manner. We also evaluated precision for a marked sign count (MSC) approach that does not use a decay rate. Because they require repeat visits to remote locations, both RDR and MSC require enormous effort levels in order to gain precise density estimates. Finally, we examined an objective criterion for decay (i.e., dung height). This showed great potential for improving RDR efficiency because choosing a high threshold height for decay reduces decay time and, consequently, the number of visits that need to be made to remote areas. The ability to adjust decay time using an objective decay criterion also opens up the potential for a "prospective" decay rate (PDR) approach. Further research is necessary to evaluate whether the temporal bias inherent in such an approach is small enough to ignore, given the 10-20-fold increases in precision promised by a PDR approach.     

The effects of proximal and distal goals on performance on a moderately complex task

The effect of a proximal plus a distal goal was investigated relative to setting only a distal goal or urging participants to do their best. Young adults (N=39) were paid on a piece rate basis to make toys. An analysis of variance revealed that the amount of money earned by the participants who were urged to ‘do your best’ was significantly greater than the amount of money earned by the participants who were assigned a distal goal. However, the amount of money earned by the participants who were assigned proximal goals, in addition to a distal goal, was significantly greater than the amount of money earned by the participants in the ‘do your best’ condition. The correlation between perceived self‐efficacy and the amount of money earned was 0.45 (p<0.01). Perceived self‐efficacy significantly increased only for those participants in the proximal plus distal goal condition. Proximal goals, through self‐efficacy and performance feedback, appear to have focused attention on task appropriate strategies. The results suggest an informational explanation of proximal goals as opposed to a motivational one through goal commitment. Implications of these findings for mentoring and training are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Phylogeny of Opsanus spp. (Batrachoididae) inferred from multiple mitochondrial-DNA sequences

 Species of the toadfish genus Opsanus are increasingly used as experimental organisms in biomedicine and evolutionary/ecological physiology. Despite their importance, little is known of the phylogenetic relationships among Opsanus species. DNA sequence data for portions of the mitochondrial 12S rRNA, cytochrome oxidase I and cytochrome b genes were generated and analyzed from the four recognized Opsanus species and three outgroup taxa. Results of these analyses indicate an evolutionarily rapid divergence of three lineages within the genus. O. beta and O. pardus were resolved within the same lineage, and could not be distinguished with these mitochondrial sequence data. These data and paleoclimatic theory support a hypothesis of speciation based on the formation of allopatric populations during periods of elevated water temperature in the northern Caribbean. Received: 6 July 1999 / Accepted: 15 March 2000     

Multifoci effects of injustice on counterproductive work behaviors and the moderating roles of symbolization and victim sensitivity

Past research suggests that employees, in response to workplace experiences, selectively engage in targeted counterproductive work behaviors (CWBs). Taking a retributive justice and target similarity perspective, we predict that employee perceptions of unfairness from the organization uniquely predict CWB specifically targeted at the organization whereas employee perceptions of supervisory unfairness uniquely predict CWB specifically targeted at the supervisor. We further hypothesized that moral identity‐symbolization would strengthen these target‐similar relationships. Finally, drawing from the sensitivity to mean intentions model, we hypothesized that victim sensitivity would not only strengthen these target‐similar relationships but also lead to cross‐foci effects of multifoci fairness perceptions on targets of CWB. Results from 3 field studies of full‐time employees provided support for most of our hypothesized relationships.     

Probabilistic assessment of the potential indoor air impacts of vent-free gas heating appliances in energy-efficient homes in the United States

Use of vent-free gas heating appliances for supplemental heating in U.S. homes is increasing. However, there is currently a lack of information on the potential impact of these appliances on indoor air quality for homes constructed according to energy-efficient and green building standards. A probabilistic analysis was conducted to estimate the impact of vent-free gas heating appliances on indoor air concentrations of carbon monoxide (CO), nitrogen dioxide (NO₂), carbon dioxide (CO₂), water vapor, and oxygen in “tight” energy-efficient homes in the United States. A total of 20,000 simulations were conducted for each Department of Energy (DOE) heating region to capture a wide range of home sizes, appliance features, and conditions, by varying a number of parameters, e.g., room volume, house volume, outdoor humidity, air exchange rates, appliance input rates (Btu/hr), and house heat loss factors. Predicted airborne levels of CO were below the U.S. Environmental Protection Agency (EPA) standard of 9 ppm for all modeled cases. The airborne concentrations of NO₂ were below the U.S. Consumer Product Safety Commission (CPSC) guideline of 0.3 ppm and the Health Canada benchmark of 0.25 ppm in all cases and were below the World Health Organization (WHO) standard of 0.11 ppm in 99–100% of all cases. Predicted levels of CO₂ were below the Health Canada standard of 3500 ppm for all simulated cases. Oxygen levels in the room of vent-free heating appliance use were not significantly reduced. The great majority of cases in all DOE regions were associated with relative humidity (RH) levels from all indoor water vapor sources that were less than the EPA-recommended 70% RH maximum to avoid active mold and mildew growth. The conclusion of this investigation is that when installed in accordance with the manufacturer’s instructions, vent-free gas heating appliances maintain acceptable indoor air quality in tight energy-efficient homes, as defined by the standards referenced in this report.

Implications: Probabilistic modeling of indoor air concentrations of carbon monoxide (CO), nitrogen dioxide (NO₂), carbon dioxide (CO₂), water vapor, and oxygen associated with use of vent-free gas heating appliances provides new data indicating that uses of these devices are consistent with acceptable indoor air quality in “tight” energy-efficient homes in the United States. This study will provide authoritative bodies such as the International Code Council with definitive information that will assist in the development of future versions of national building codes, and will provide evaluation of the performance of unvented gas heating products in energy conservation homes.