Treatment of urban runoff at Lake Tahoe: low-intensity chemical dosing.

A systematic investigation of the effect of coagulant type and dose and temperature, mixing, and water quality on subsequent charge neutralization and removal of phosphorus and fine particles from urban and/or stormwater runoff entering Lake Tahoe (Sierra Nevada mountains, western United States) was conducted. Dosing based on streaming current values resulted in turbidities of less than 10.9 +/- 0.35 NTU and filterable and total phosphorus concentrations of less than 9.83 +/- 0.54 and 25.6 +/- 5.71 microg/L, respectively. Inadequate slow mixing could be partially compensated for by increased settling time; however, such quiescent conditions are difficult to obtain in natural systems. For prehydrolyzed forms of aluminum, high intensity rapid mixing was counterproductive. Several classes of coagulants responded robustly to water quality and temperature changes. However, polyaluminum chlorides modified with silica or sulfate, with low to medium basicity, were consistently the best performers in these tests, in terms of simultaneously removing phosphorus and fine particles under a wide range of operating conditions with low doses.     

Regional Blue and Green Water Balances and Use by Selected Crops in the U.S.

The availability of freshwater is a prerequisite for municipal development and agricultural production, especially in the arid and semiarid portions of the western United States (U.S.). Agriculture is the leading user of water in the U.S. Agricultural water use can be partitioned into green (derived from rainfall) and blue water (irrigation). Blue water can be further subdivided by source. In this research, we develop a hydrologic balance by 8‐Digit Hydrologic Unit Code using a combination of Soil and Water Assessment Tool simulations and available human water use estimates. These data are used to partition agricultural groundwater usage by sustainability and surface water usage by local source or importation. These predictions coupled with reported agricultural yield data are used to predict the virtual water contained in each ton of corn, wheat, sorghum, and soybeans produced and its source. We estimate that these four crops consume 480 km³ of green water annually and 23 km³ of blue water, 12 km³ of which is from groundwater withdrawal. Regional trends in blue water use from groundwater depletion highlight heavy usage in the High Plains, and small pockets throughout the western U.S. This information is presented to inform water resources debate by estimating the cost of agricultural production in terms of water regionally. This research illustrates the variable water content of the crops we consume and export, and the source of that water.     

River Basin Export Reduction Optimization Support Tool; a tool to screen options for reducing nutrient loads while minimizing cost

Excess loading of nitrogen and phosphorus to river networks causes environmental harm, but reducing loads from large river basins is difficult and expensive. We developed a new tool, the River Basin Export Reduction Optimization Support Tool (RBEROST) to identify the least-cost combinations of management practices that will reduce nutrient loading to target levels in downstream and mid-network waterbodies. We demonstrate the utility of the tool in a case study in the Upper Connecticut River Basin in New England, USA. The total project cost of optimized lowest-cost plans ranged from $18.0 million to $41.0 million per year over 15 years depending on user specifications. Plans include both point source and non-point source management practices, and most costs are associated with urban stormwater practices. Adding a 2% margin of safety to loading targets improved the estimated probability of success from 37.5% to 99%. The large spatial scale of RBEROST, and the consideration of both point and non-point source contributions of nutrients, make it well suited as an initial screening tool in watershed planning.     

The Fate of Murine Norovirus and Hepatitis A Virus During Preparation of Fresh Produce by Cutting and Grating

Human noroviruses and hepatitis A virus (HAV) are commonly associated with outbreaks occurring in restaurant establishments and catered events. Food handlers are major contributing factors to foodborne illnesses initiated in the kitchen setting. In this study, transfer of HAV and murine norovirus (MNV-1), a human norovirus surrogate, between produce (cucumbers, strawberries, tomatoes, cantaloupes, carrots, and honeydew melons) and common kitchen utensils (graters and knives) was investigated. The extent of virus transfer to produce during utensil application, in the presence and the absence of food residue, and the impact of knife surface properties (sharp, dull, serrated) was also investigated. Transfer of MNV-1 and HAV from produce items, initially contaminated with ~5.5 log PFU, to knives and graters during application ranged from 0.9 to 5.1 log PFU. MNV-1 transfer to knives was the greatest for cucumbers, strawberries, and tomatoes, and the least for honeydew melons, while transfer of HAV to knives was greater for tomatoes and honeydew melons than strawberries, cantaloupes, and cucumbers. After preparation of a contaminated produce item, knife cross-contamination easily occurred as viruses were detected on almost all of the seven produce items successively prepared. Produce residues on utensils often resulted in less virus transfer when compared to utensils without residue accumulation. Knife surface properties did not impact virus transfer. The ease of virus transfer between produce and utensils demonstrated by the current study highlights the importance of efforts aimed toward preventing cross-contamination in the kitchen environment.     

Prenatal diagnosis of the Klippel-Trenaunay-Weber syndrome

The Klippel-Trenaunay-Weber syndrome is a complex developmental disorder of the vascular and skeletal systems. While many features of the syndrome are congenital, it has not been diagnosed often before birth. This paper describes a case of Klippel-Trenaunay-Weber syndrome diagnosed at 19 weeks' gestation on the basis of sonographic findings and family history. The clinical variability of the syndrome is emphasized and the importance of family history in differential diagnosis is stressed.     

Abusive supervision and feedback avoidance: The mediating role of emotional exhaustion

The occurrence of abusive supervision is steadily rising. Extant literature continues to expand the number of destructive consequences linked to such improper workplace behavior. This study tested a model linking abusive supervision to feedback avoidance through emotional exhaustion. We invoked conservation of resources theory in our examination of the role that the loss of valued resources plays in instances where abuse is perceived. Results from three rounds of matched data from 460 nurses and 220 working adults demonstrated support for our model, suggesting a mediating effect for exhaustion on the relationship between abuse and feedback avoidance. Findings also revealed that feedback avoidance was associated with subsequent exhaustion, representing a loss spiral. These findings are important as they reveal the link between a subordinate's reactions (exhaustion) and coping behavior (feedback avoidance) when supervisory abuse is perceived. Theoretical and practical implications, limitations, and directions for future research are offered. Copyright © 2012 John Wiley & Sons, Ltd.     

Criteria for designing electrostatic precipitators

This paper discusses the concepts of effective migration velocity and specific collector area as derived from the Deutsch equation. These two factors are commonly used as a means of specifying plant size and comparing proposals by different suppliers.It is demonstrated that effective migration velocity is not a constant dependent only on the fuel, being subject to large variations according to various features of the design of the precipitator. It is also shown that specific collector area cannot be used without at the same time considering the contact time of the gases in the electrostatic field.The removal of dust by a precipitator is carried out in two stages. The dust is first deposited on the collecting electrode, and a layer of significant thickness must be allowed to form so that when, in the second stage, it is dislodged by rapping, the layer breaks into agglomerated masses sufficiently large to fall into the hoppers below the collecting electrodes before being carried by the moving gas stream into the outlet flue. This requires that the frequency of rapping of each field of the precipitator shall be set at the correct rate according to the concentration of dust entering the field.Currently much stress is being placed on the intensity of the rapping blow and there is a tendency to specify increasing values of this blow. Due to the necessity of allowing a layer of dust to form, no increase in rapping intensity can overcome the effect of highly resistive dust. While the rapping force must be enough to shear the dust layer, any increase above this level is likely to result in the breakdown of agglomerates with an increase in dust emission and may also cause metal fatigue problems.     

An invader differentially affects leaf physiology of two natives across a gradient in diversity

Little is known about how exotics influence the ecophysiology of co-occurring native plants or how invader impact on plant physiology may be mediated by community diversity or resource levels. We measured the effect of the widespread invasive forb spotted knapweed (Centaurea maculosa) on leaf traits (leaf dry matter content, specific leaf area, leaf nitrogen percentage, leaf C:N ratios, and delta13C as a proxy for water use efficiency) of two co-occurring native perennial grassland species, Monarda fistulosa (bee balm) and Koeleria macrantha (Junegrass). The impact of spotted knapweed was assessed across plots that varied in functional diversity and that either experienced ambient rainfall or received supplemental water. Impact was determined by comparing leaf traits between identical knapweed-invaded and noninvaded assemblages. Virtually all M. fistulosa leaf traits were affected by spotted knapweed. Knapweed impact, however, did not scale with its abundance; the impact of knapweed on M. fistulosa was similar across heavily invaded low-diversity assemblages and lightly invaded high-diversity assemblages. In uninvaded assemblages, M. fistulosa delta13C, leaf nitrogen, and C:N ratios were unaffected by native functional group richness, whereas leaf dry matter content significantly increased and specific leaf area significantly decreased across the diversity gradient. The effects of spotted knapweed on K. macrantha were weak; instead native functional group richness strongly affected K. macrantha leaf C:N ratio, delta13C, and specific leaf area, but not leaf dry matter content. Leaf traits for both species changed in response to spotted knapweed or functional richness, and in a manner that may promote slower biomass accumulation and efficient conservation of resources. Taken together, our results show that an invader can alter native plant physiology, but that these effects are not a simple function of how many invaders exist in the community.