Factors controlling sorption of prosulfuron by variable-charge soils and model sorbents

Prosulfuron [1-(4-methoxy-6-methyltriazin-2-yl)-3-[2-(3,3,3-trifluoropropyl) phenylsulfonyl]-urea), a relatively new sulfonylurea herbicide, is a weak acid (pK(a) 3.76), and therefore, will undergo pH-dependent speciation and sorption. Understanding prosulfuron sorption in soils is important for predicting its environmental fate. Soil and solution factors controlling sorption were investigated by measuring prosulfuron sorption on five model sorbents (amorphous silica, alpha-alumina, CaSWy1 montmorillonite, commercial humic acid, and anion exchange resin) and 10 variable-charge soils from CaCl(2) and Ca(H(2)PO(4))(2) solutions as a function of pH and ionic strength. Anion exchange of prosulfuron accounted for up to 82% of overall sorption in the pH range from 3 to 7. The relative importance of anion exchange to prosulfuron sorption was positively correlated to the ratio of anion and cation exchange capacities. Comparison between organic carbon (OC)-normalized sorption (K(oc)) versus pH for humic acid and variable-charge soils show similar trends with sorption decreasing with increasing pH. However, K(oc) values estimated from variable-charge soils in the lower pH range where anion exchange has the greatest contribution to sorption was almost one log unit greater than that estimated from humic acid clearly exemplifying the impact of anion exchange. Similarity in K(oc)-pH curves for humic acid and variable-charge soils may result from the fact that (i) cation exchange capacity increases with increasing OC content, thus effective anion exchange capacity is reduced; and (ii) the relative contribution of hydrophobic and hydrophilic sorption mechanisms was fairly constant. Given that both hydrophilic and hydrophobic sorption of prosulfuron decrease with increasing pH, addition of fertilizer and lime amendments may enhance the potential for off-site leaching of recently applied acidic pesticides.     

Flow experiences at work: for high need achievers alone?

Applying Csikszentmihalyi's ( 1990 ) flow theory of optimal experience to the workplace, two studies examined the relationships of employees' perceived skill and challenge at work and need for achievement with their positive mood, intrinsic task interest, and extra‐role performance. Among achievement‐oriented employees only, high skill and challenge was associated with greater positive mood, task interest, and performance than other skill/challenge combinations. Additionally, positive mood mediated the interactive relationship of skill/challenge and need for achievement with performance. Copyright © 2005 John Wiley & Sons, Ltd.     

A horizontal merger in the iron ore industry: An event study approach

The purpose of this paper is to analyse the competitive and efficiency impacts of a large merger in the world iron ore industry, using an event study approach. This method builds on an analysis of stock market reactions of the merging firms as well as close rivals at the time of the merger announcement. The event study method allows for the possibility to assess both the motivations behind as well as the welfare effects of the merger. The event study results for the merger announcement of Rio Tinto and North Ltd. show that, according to the market reactions, the main motive behind the merger was either the market power or the efficiency hypothesis. When adjusting the analysis to include several information releases about the merger, the overall result indicates that efficiency improvements were the predominant motives behind the merger. Thus, the event study results suggest that there are positive welfare effects to expect and the European Commission's decision to allow the merger is supported.     

Social organization and space-use in Gunnison's prairie dog

Summary Social organization of the Gunnison's prairie dog, Cynomys gunnisoni, was studied in two populations in south-central Colorado. Gunnison's prairie dogs live in complex, interactive societies fitting current definitions of highly social ground squirrels. Members of harems (coteries) cooperatively use and defend a common territory. Spatial overlap is extensive between the adult male(s) and adult females, and among adult females within the harem through the active season. Amicable behavioral interactions are frequent within the harem, whereas interactions between members of different harems are primarily agonistic and spatial overlap is minimal. Although their behavioral repertoire is more limited, social organization of the Gunnison's prairie dog most closely resembles that of the black-tailed prairie dog, C. ludovicianus. Although body size, age of first reproduction, and age of emigration differed between the two study populations (Rayor 1985a), a comparison of social traits did not reveal substantial differences.     

Natural factors and human modifications contributing to marsh loss in Louisiana's Mississippi River Deltaic Plain

Natural factors and human modifications contribute to the estimated annual loss of 10,200 ha of coastal land in the Mississippi River Deltaic Plain Region of south Louisiana. This paper combines information on regional geology and human-induced habitat alterations to evaluate the relative importance of human and natural factors to marsh loss. Data on marsh area and habitat type for 139 7.5-min quadrangles were calculated from maps based on aerial photographs from 1955/56 and 1978, and data on regional geology obtained from published maps were used to construct multivariate model relating initial marsh area, change in urban and agricultural area, change in canal and spoil area, canal area in 1978, depth of sediment overlying the Prairie terrace, and subdelta age to marsh loss. The model indicated that between 25.0% and 39.0% of the marsh loss that occurred during the 23-year period was related to canal and spoil construction, and between 9.5% and 12.7% was related to urban and agricultural development. These are minimal estimates of loss because they do not include many secondary effects (for example, canal orientation, saltwater intrusion, and eutrophication) that can also result in indirect loss. Depth of sediment, initial marsh area, delta lobe age by 1978 canal and spoil area interaction, and indirect effects not included in the model accounted for remaining marsh loss.     

The arsenic content of bottled mineral waters

The arsenic levels of 23 mineral waters on sale to the public in the United Kingdom were measured. The arsenic content of most waters was below 1 g L^–1 but the statutory limits of 50 ug L^–1 for natural mineral waters and 100 g L^–1 for non-alcoholic beverages were exceeded by the French mineral water, Vichy Célestins (220 ug L^–1). Regular consumption of mineral water of such elevated concentration could make a significant contribution to the intake of the more toxic inorganic species of arsenic, with possible adverse long-term effects on the health of some individuals. The general need for analytical speciation studies of dietary arsenic is emphasised.     

Distribution and mode of occurrence of selenium in US coals

Selenium excess and deficiency have been established as the cause of various health problems in man and animals. Combustion of fossil fuels, especially coal, may be a major source of the anthropogenic introduction of selenium in the environment. Coal is enriched in selenium relative to selenium's concentration in most other rocks and relative to selenium in the Earth's crust.Data from almost 9,000 coal samples have been used to determine the concentration and distribution of selenium in US coals. The geometric mean concentration of selenium in US coal is 1.7 ppm. The highest mean selenium value (geometric mean 4.7 ppm) is in the Texas Region. Atlantic Coast (Virginia and North Carolina) and Alaska coals have the lowest geometric means (0.2 and 0.42 ppm, respectively). All western coal regions have mean selenium concentrations of less than 2.0 ppm. In contrast, all coal basins east of the Rocky Mountains (except for several small basins in Rhode Island, Virginia, and North Carolina) have mean selenium values of 1.9 or greater.Generally, variations in selenium concentration do not correlate with variations in ash yield, pyritic sulphur, or organic sulphur concentrations. This may be the result of multiple sources of selenium; however, in some non-marine basins with restricted sources of selenium, selenium has positive correlations with other coal quality parameters.Selenium occurs in several forms in coal but appears to be chiefly associated with the organic fraction, probably substituting for organic sulphur. Other important forms of selenium in coal are selenium-bearing pyrite, selenium-bearing galena, and lead selenide (clausthalite). Water-soluble and ion-exchangeable selenium also have been reported.     

Pulling up roots in the 1990s: Who's willing to relocate?

The purpose of this study was to develop a profile of employees in Fortune 500 companies who are willing to relocate. The profile was developed on a demographically diverse random sample of 827 employees from 20 Fortune 500 corporations, all of whom had moved at least once for their current employer. Employees who were most willing to relocate were younger, their incomes were lower, their career ambitions higher, and their spouses more willing than those who were less willing to relocate. These employees could be found in sales/marketing and production functions. Their attitudes toward moving were also favorable. The single most important predictor of willingness to relocate was spouse willingness to relocate. This result suggests strongly that in the 1990s, corporations are going to have to address the concerns of spouses, if married employees are going to remain mobile. The study also cautions corporations about the shortsightedness of thinking of spouse and dual career issues as ’women's issues‘ and assuming that females and minorities are unwilling to relocate.     

POLICY IMPACTS ON AGRICULTURAL IRRIGATION ELECTRICITY DEMAND IN THE COLUMBIA BASIN1

ABSTRACT: Accurately estimating the price elasticity of demand for irrigation electricity is important to major electricity suppliers such as the Bonneville Power Administration (BPA) of the Pacific Northwest. The BPA has a revenue maximization objective, and the elasticity of demand is central to its rate setting process. Several studies have attempted to estimate demand for irrigation electricity, but none has explicitly included federal agricultural policy and program variables. Tins paper discusses how agricultural programs may influence farmers irrigation decisions and thus their demand for irrigation electricity. It suggests that existing programs serve to make farmers more responsive to electricity rate increases than would otherwise be the case. Thus, studies that fail to include them may underestimate the responsiveness of farmers to electricity rate increases.