Phosphorus leaching at cold temperatures as affected by wastewater application and soil phosphorus levels

Land application of wastewater in the northern-tier United States during winter months has been suggested as a means to reduce cost of building storage lagoons. A study was initiated in 1996 to assess land application of potato-processing wastewater on a 120-ha field at Park Rapids, MN. One objective of this study was to evaluate the effects of soil P levels and temperature on P leaching in soil columns. In this paper, we report the P sorption, desorption, and leaching characteristics of a high-P (>200 mg kg(-1)) and a low-P (<25 mg kg(-1)) surface soil from the wastewater irrigation site. The leaching experiment was done with wastewater at 4 +/- 2 or 10 +/- 2 degrees C. The high-P soil resulted in an equilibrium P concentration of 8.0 mg L(-1) compared with 0.14 mg L(-1) for the low-P soil. When low-P wastewater was applied to the high-P soil, the soil acted as a P source, and the total phosphorus (TP) concentration in the leachate was 3.5 times higher than the input TP concentration (C0). When high-P wastewater was applied to the high-P soil, the soil acted as a P sink retarding the TP concentration in the leachate by 80%. Phosphorus desorption was higher at 10 degrees C compared with 4 degrees C. The results showed that depending on P levels of the soil and the wastewater, reduction or increase in leachate P will occur below the surface soil. However, further mobility of this P under field conditions will depend on the volume and rate of percolating water as well as the sorption-desorption characteristics of the subsoil.     

Evaluation of a System to Automatically Sample Zooplankton From the Discharge of Dams1

ABSTRACT: Automatic plankton samplers installed at two dams on the Connecticut River Continuously monitored crustacean zooplankton from October 1977 through 1979 and allowed a significant reduction in man-hours involved in an extensive sampling program. Automatic samplers efficiently sampled most species and size classes of crustacean zooplankton in a similar, but not consistently identical manner as a commonly used towed-net plankton sampler. The smallest sized zooplankton were captured more efficiently than the largest. Mesh selection and sampler avoidance exerted different influences on automatic samplers and towed nets. Future use of the samplers and direct comparison of results to results obtained by other methods was supported.     

South Korean managerial reactions to voicing discontent: The effects of employee attitude and employee communication styles

Using a scenario‐based experiment, this study examined how employee attitude and employee communication styles affected managers' reactions to employees' objections to a company policy. In the experiment, employee attitude (cynical versus trusting) and employee communication styles (aggressive versus diplomatic) were manipulated, and managers' reactions to voicing discontent were assessed through a questionnaire. Based on a sample of 185 middle managers working in various organizations in South Korea, the results showed that managers were more likely to engage in social undermining and were less likely to provide social support when cynical (rather than trusting) employees objected to a company policy. Also, attributed motives (i.e., personal attack and health concern) fully mediated the relationship between employee attitude and social support and social undermining. In addition, managers more likely attributed the objection to moral concerns when trusting (rather than cynical) employees communicated in an aggressive manner. Copyright © 2009 John Wiley & Sons, Ltd.     

Individual Measurements of the Emission Factor of Aerosol Black Carbon in Automobile Plumes

As automobiles passed a measuring point, we recorded the concentrations of carbon dioxide and aerosol black carbon (BC) in their dispersing exhaust plumes. After subtraction of background levels, the ratio of the increments of these species allows us to calculate the emission factor of BC per unit mass of fuel from each individual vehicle. These factors spanned a range of greater than two orders of magnitude, representing the emission of from 4 × 10^?6 to 10^?3 grams of aerosol black carbon per gram of carbon consumed in the fuel. Their distribution showed that 20 percent of the vehicles accounted for 65 percent of the emissions. The real-time measurement methodology allows for a determination of the distribution of emission factors across the actual population of sources. These results are similar to the wide range of carbon monoxide emission factors reported recently.     

Risk-based evaluation of Escherichia coli monitoring data from undisinfected drinking water

Drinking water regulations in the United States and elsewhere are based on the occurrence of fecal indicator bacteria. Though not meeting all the criteria of an ideal indicator, nonpathogenic strains of Escherichia coli (E. coli) are used worldwide as an indicator of potential fecal contamination for drinking water and for distribution systems. This is, in part, because real illnesses are related to human pathogens, such as E. coli O157:H7, whose presence may be predicted better by E. coli than by total coliform bacteria. Our objective was to estimate the number of E. coli O157:H7 illnesses attributable to drinking water exposures in the United States and the feasible relationships between positive occurrences of the indicator bacteria E. coli and E. coli O157:H7 in drinking water. Results of the modeling indicate that in undisinfected drinking water systems, the ratio of bacterial indicator E. coli positives to E. coli O157:H7 organisms is estimated to be between 6:1 and 90:1 with few model parameters accounting for the vast majority of the uncertainty. These results provide context for considering the potential public health implications of a positive E. coli result from routine monitoring of undisinfected drinking water.     

Transport pathways for arsenic and selenium: a minireview

Arsenic and selenium are metalloids found in the environment. Arsenic is considered to pose the most significant potential threat to human health based on frequency of occurrence, toxicity and human exposure. Selenium, on the other hand, ranks only 147th in toxicity but, in contrast to arsenic, is a required micronutrient. Whether a toxin or micronutrient, their metabolism requires that cells to accumulate these metalloids. In this review we discuss the membrane proteins that transport arsenic and selenium into cells, from bacteria to humans, as well as some of the efflux proteins involved in detoxification.     

The Black Carbon Story: Early History and New Perspectives

A number of recent studies have suggested that black carbon (BC), the light-absorbing fraction of soot, is next to CO₂ one of the strongest contributors to the global climate change. BC heats the air, darkens the snow and ice surfaces and could contribute to the melting of Arctic ice, snowpacks, and glaciers. Although soot is the oldest known pollutant its importance in climate modification has only been recently recognized. In this article, we trace the historical developments over about three decades that changed the view of the role of BC in the environment, from a pollutant of marginal importance to one of the main climate change agents. We also discuss some of the reasons for the initial lack of interest in BC and the subsequent rigorous research activity on the role of aerosols in climate change.     

Bottom sediment as a source of organic contaminants in Lake Mead, Nevada, USA

Treated wastewater effluent from Las Vegas, Nevada and surrounding communities’ flow through Las Vegas Wash (LVW) into the Lake Mead National Recreational Area at Las Vegas Bay (LVB). Lake sediment is a likely sink for many hydrophobic synthetic organic compounds (SOCs); however, partitioning between the sediment and the overlying water could result in the sediment acting as a secondary contaminant source. Locating the chemical plumes may be important to understanding possible chemical stressors to aquatic organisms. Passive sampling devices (SPMDs and POCIS) were suspended in LVB at depths of 3.0, 4.7, and 6.7 (lake bottom) meters in June of 2008 to determine the vertical distribution of SOCs in the water column. A custom sediment probe was used to also bury the samplers in the sediment at depths of 0-10, 10-20, and 20-30 cm. The greatest number of detections in samplers buried in the sediment was at the 0-10 cm depth. Concentrations of many hydrophobic SOCs were twice as high at the sediment-water interface than in the mid and upper water column. Many SOCs related to wastewater effluents, including fragrances, insect repellants, sun block agents, and phosphate flame retardants, were found at highest concentrations in the middle and upper water column. There was evidence to suggest that the water infiltrated into the sediment had a different chemical composition than the rest of the water column and could be a potential risk exposure to bottom-dwelling aquatic organisms.