Biosorption of hydrophobic organic pollutants by mixed microbial populations

In recognition of the need to estimate biosorption for natural microbial populations, the variability of partition coefficients for two hydrophobic pollutants to natural populations from a variety of aquatic systems was investigated. Biosorption partition coefficents for pyrene [2.46(±0.6) × 10⁴] and phenanthrene [6.34(±1) × 10³] were nearly constant over 14 different microbial sources, consisting of sediments and soils from eight states. For these condensed ring aromatics, semi-empirical equations were developed relating biosorption partition coefficients to octanol/water partition coefficients and to water solubility and melting point. Concepts and relationships developed for these materials should extend to other families of hydrophobic compounds.     

Weekend–weekday aerosols and geographic variability in cloud-to-ground lightning for the urban region of Atlanta, Georgia, USA

We characterized the differences in warm-season weekday and weekend aerosol conditions and cloud-to-ground (CG) flashes (1995–2008) for an 80,000 square kilometer region around Atlanta, Georgia, a city of 5.5 million in the humid subtropics of the southeastern United States. An integration of distance-based multivariate techniques (hierarchical agglomerative clustering, multiresponse permutation procedures, fuzzy kappa statistics, and Mantel tests) indicated a greater concentration of CG flash activity within a 100 km radius around Atlanta under weekday aerosol concentrations. On weekends, these effects contracted toward the city. This minimized any weekly anthropogenic cycle over the more densely populated urban center even though this location had a higher flash density, a higher percentage of days with flashes, and stronger peak currents over the course of a week compared to the surrounding region. The sharper contrasts in weekday and weekend lightning regime developed outside the perimeter of the city over nonurban land uses. Here, lightning on weekend and weekdays differed more in its density, frequency, polarity, and peak current. Across the full extent of the study region, weekday peak currents were stronger and flash days more frequent, suggesting that weekly CG lightning signals have a regional component not tied to a single city source. We integrate these findings in a conceptual model that illustrates the dependency of weekly anthropogenic weather signals on spatial and temporal extent.     

SIMULATED RELATIONSHIPS BETWEEN SPECTRAL REFLECTANCE,THERMAL EMISSIONS,AND EVAPOTRANSPIRATION OF A SOYBEAN CANOPY1

ABSTRACT: A canopy reflectance model is incorporated into a routine for simulating water and energy flows in the soil-plant-atmosphere system. The reflectance model is structured tocalculate canopy albedo throughout each simulation period and to determine spectral reflectances at a specified time during the day. Spectral vegetation indices are then calculated from the reflectances and related to the evapotranspiration and thermal response of the canopy. The canopy reflectance model is also used to establish the photo-sytheticaily active radiation load at various depths in the canopy. Stomatal resistances are calculated using these radiation values and integrated to give the minimum canopy resistance. Actual canopy resistance is obtained by adjusting minimum canopy resistance for environmental stresses such as leaf water potential and leaf temperature. Using data for a soybean canopy, canopy evapotranspiration and temperatures are simulated for a range of leaf area index values and compared with the corresponding spectral vegetation indices. The resuits indicate that the normalized difference spectral index has an inverse linear relationship with canopy temperature, concurring with results obtained from satellite observations. The possibility of using a spectral vegetation index and thermal observations together to parameterize surface moisture availability for evapotranspiration is considered.     

A PRECIPITATION ESTIMATION TECHNIQUE FOR DEVELOPING ISOHYETS IN AN ARID AREA USING VEGETATION AND TOPOGRAPHIC PARAMETERS1

A technique is presented for developing an isohyet map for the Hualapai Valley, a closed hydrologic basin of about 315 square miles in the northwestern Great Basin in Nevada. In this basin there is practically no climatic data, and in the northwest Great Basin there are too few stations for determination of rainfall on a detailed basis. Using a vegetational typing to represent a range in elevation and precipitation, an initial mean annual rainfall is determined for selected points on a grid pattern. This rainfall is then modified by using topographic parameters of slope, orientation, exposure, and rainfall shadow effect. The resulting point determinations of mean annual rainfall are then smoothed using a trend surface analysis, and an isohyetal map is drawn from the smoothed points. The technique provides an estimated accuracy of one inch of mean annual precipitation and one mile of resolution on isohyets.     

Derivative mine valuation: strategic investment decisions in competitive markets

Successful management in competitive markets requires evaluation methods that respond to global market dynamics and provide investors with relevant information to make strategic investment decisions. These strategic decisions include decisions on investment timing, feasibility study and risk management and mine operating options. Conventional methods do not have the built-in capabilities to help investors handle these strategic issues. Advances in modern finance have had profound impacts on financial markets for options, futures and collaterized securities and offer appropriate tools in solving these problems. In this paper, the authors have extended the Brennan and Schwartz mineral resource model to develop the derivative mine valuation method based on the dynamic arbitrage theory. A copper mining venture has been evaluated using the derivative mine valuation and conventional methods. The results show that the derivative mine valuation method allows investors to maximize the venture's market value by exercising these strategic options.     

Daily rhythm of O2-evolution in the cyanobacterium Trichodesmium thiebautii under natural and constant conditions

The rate of oxygen evolution by the tropical marine cyanobacterium Trichodesmium thiebautii was recorded at different times during the day in samples collected in 1992 from the Bahama Islands and the NE Caribbean Sea. This cyanobacterium is unique in that it is the only non-heterocystous diazotroph capable of N₂-fixation in daylight. Oxygen evolution was measured under conditions of natural day/night (LD, N=50), constant light (LL, N=14), and constant dark (DD, N=2×14). Photosynthesis vs intensity (P-I) relationships were calculated at various times of day, and the following parameters were used for further evaluation: photosynthesic capacity (P _max, 66 to 91 mg O₂ mg chl a ^-1 h^-1), initial slope of the P-I curve (, 0.23 to 0.27), dark respiration (R, 12 to 27 mg O₂ mg chl a ^-1 h^-1), and the intensity at which O₂ consumption is compensated by O₂ production (I _c, 78 to 160 Em^-2 s^-1). All means showed large standard deviations (for some parameters more than 200%). In some cases, these variations could be explained with a sinusoidal 24-h time course, but only the compensation point showed a significant daily variation (p0.001) in both LD and DD. The fact that the time course of I _c typical for natural conditions remains rhythmic under constant dark conditions strongly suggests a circadian regulation. Few circadian rhythms have been observed in prokaryotes, and this appears to be the first observation of such a rhythm in a cyanobacterium which fixes N₂ in daytime.     

Risk characterization, assessment, and management of organic pollutants in beneficially used residual products

A wide array of organic chemicals occur in biosolids and other residuals recycled to land. The extent of our knowledge about the chemicals and the impact on recycling programs varies from high to very low. Two significant challenges in regulating these materials are to accurately determine the concentrations of the organic compounds in residuals and to appropriately estimate the risk that the chemicals present from land application or public distribution. This paper examines both challenges and offers strategies for assessing the risks related to the occurrence of organic compounds in residuals used as soil amendments. Important attributes that must be understood to appropriately characterize and manage the potential risks for organic chemicals in biosolids include toxicity and dose response, transport potential, chemical structure and environmental stability, analytical capability in the matrix of interest, concentrations and persistence in waste streams, plant uptake, availability from surface application versus incorporation, solubility factors, and environmental fate. This information is complete for only a few chemicals. Questions persist about the far greater number of chemicals for which toxicity and environmental behavior are less well understood. This paper provides a synopsis of analytical issues, risk assessment methodologies, and risk management screening alternatives for organic constituents in biosolids. Examples from experience in Wisconsin are emphasized but can be extrapolated for broader application.     

Trust as a mediator of the relationship between organizational justice and work outcomes: test of a social exchange model

Data obtained from full‐time employees of a public sector organization in India were used to test a social exchange model of employee work attitudes and behaviors. LISREL results revealed that whereas the three organizational justice dimensions (distributive, procedural and interactional) were related to trust in organization only interactional justice was related to trust in supervisor. The results further revealed that relative to the hypothesized fully mediated model a partially mediated model better fitted the data. Trust in organization partially mediated the relationship between distributive and procedural justice and the work attitudes of job satisfaction, turnover intentions, and organizational commitment but fully mediated the relationship between interactional justice and these work attitudes. In contrast, trust in supervisor fully mediated the relationship between interactional justice and the work behaviors of task performance and the individually‐ and organizationally‐oriented dimensions of citizenship behavior. Copyright © 2002 John Wiley & Sons, Ltd.