Effects of equipment loadings on geosynthetic-lined slope behaviour.

When combined in the lining and covering of waste-containment facilities, soil and geosynthetic components protect the environment by acting as a hydraulic barrier. Equipment loading may significantly increase the tensile stress induced in geosynthetic components, leading to a potential stability problem. Large equipment loadings may also result in a localized circular slip surface during construction operations. New analytical method based on discrete element modelling is proposed for estimating the distribution of tensile force developed in the individual geosynthetic components of the lining system and for evaluating the safety factor of slope failure due to equipment loading. The analytical results of an example are presented to demonstrate the applicability of the analytical method for the lining system of a waste landfill. The analyses of the example show that equipment loading provide a substantial increase in the tensile forces of the geosynthetic components of a lining system and that the possibility of shallow failure due to equipment loading increases as the slope becomes steeper. This method is a useful tool for analysing the lining system of waste landfills with complex lining components.     

Workplace deviance,organizational citizenship behavior,and business unit performance: the bad apples do spoil the whole barrel

The influences of organizational citizenship behavior (OCB) and workplace deviant behavior (WDB) on business unit performance were investigated using data from branches of a fast food organization. Data included measures of WDB and OCB obtained from staff, ratings of performance provided by supervisors, and objective measures of performance. It was found that WDB was negatively and significantly associated with business unit performance measured both subjectively and objectively. OCB, however, failed to contribute to the prediction of business unit performance beyond the level that was achieved by WDB. It appeared, therefore, that the presence of deviant employees among business units impinges upon the performance of the business unit as a whole, whereas OCBs had comparatively little effect. Copyright © 2004 John Wiley & Sons, Ltd.     

Unreliability of co‐occurrence‐based sediment quality guidelines for contaminated sediment evaluations at Superfund/hazardous chemical sites

Many Superfund/hazardous chemical sites include waterbodies whose sediments contain hazardous chemicals. With the need to assess, rank, and remediate contaminated sediments at such sites, as well as in other waterways, regulators seek a simple, quantitative assessment approach that feeds easily into a decision‐making scheme. Numeric, co‐occurrence‐based “sediment quality guidelines” have emerged with the appearance of administrative simplicity. However, the very foundation of the co‐occurrence approach, based on the total concentrations of a chemical(s) in sediment, is technically invalid; its application relies on additional technically invalid presumptions. Use of technically invalid evaluation approaches renders any assessment of the significance of sediment contamination unreliable. This article reviews the technical roots and assumptions of the co‐occurrence‐based SQGs, the fundamental flaws in the rationale behind their development and application, and their misapplication for sediment quality evaluation. It also reviews concepts and approaches for the more reliable evaluation, ranking, and cleanup assessment of contaminated sediments at Superfund sites and elsewhere. © 2005 Wiley Periodicals, Inc.     

Influence of ozone stress on growth processes, yields and grain quality characteristics among soybean cultivars

Field studies were conducted at USDA Beltsville Agricultural Research Center, Beltsville, Maryland, in 1984 and 1985 using open-top chambers to acquire information on the responses of 12 soybean (Glycine max L. Merr.) cultivars to O3 stress and to examine the interactions between maturity groups and O3 stress. Cultivars representing Groups III, IV, and V were exposed for approximately 3 months to charcoal-filtered air (CF) and nonfiltered air plus 40 nl litre(-1) O3 (NF + O3). Ozone was added 6 h d(-1), 5 d week(-1) for 13 weeks. The CF effectively reduced the accumulative oxidant exposure (AOX) to less than 1.0 microl litre(-1) h and the NF + O3 treatment approximately doubled the ambient AOX (16.7 microl litre(-1) h) to about 30 microl litre(-1) h. The AOX estimates the total O3 exposure above 30 nl litre(-1) during an entire growing season. Plant growth rates and relative growth rates were reduced by 17.0 and 14.4%, respectively, when averaged over cultivars. Based on growth rates, the Group III cultivars were the most affected by O3 stress. Averaged over cultivars, leaf expansion rates, leaf conductance, and transpiration rates were lower in the NF + O3 treatment compared to the CF control; however, wide variation was found with the stomatal results from field observations. Combined over years and cultivars, grain yield was reduced by an average of 12.5% by O3 stress with 3 of 12 cultivars showing significant reductions. Grain protein content was increased by 0.7% by O3 stress, but cultivar differences were equal to the differences caused by the O3 treatments. Grain oil content was unchanged by the O3 treatments. Group IV cultivars showed the greatest decrease in grain yield due to O3 stress. Multiple regression analyses were calculated using the difference between the CF and NF + O3 treatment as a measure of O3 stress. Significant positive relationships were found among net assimilation rates, plant growth rates, relative growth rates, and leaf expansion rates, which suggest that growth analysis characteristics would be useful in addition to yield in air pollution tolerance improvement studies with soybeans.     

An Approach for Evaluating the Effectiveness of Various Ozone Air Quality Standards for Protecting Trees

We demonstrate an approach for evaluating the level of protection attained using a variety of forms and levels of past, current, and proposed Air Quality Standards (AQSs). The U.S. Clean Air Act requires the establishment of ambient air quality standards to protect health and public welfare. However, determination of attainment of these standards is based on ambient pollutant concentrations rather than prevention of adverse effects. To determine if a given AQS protected against adverse effects on vegetation, hourly ozone concentrations were adjusted to create exposure levels that “just attain” a given standard. These exposures were used in combination with a physiologically-based tree growth model to account for the interactions of climate and ozone. In the evaluation, we used ozone concentrations from two 6-year time periods from the San Bernardino Mountains in California. There were clear differences in the level of vegetation protection achieved with the various AQSs. Based on modeled plant growth, the most effective standards were the California 8-hr average maximum of 70 ppb and a seasonal, cumulative, concentration-weighted index (SUM06), which if attained, resulted in annual growth reductions of 1% or less. Least effective was the 1-hr maximum of 120 ppb which resulted in a 7% annual reduction. We conclude that combining climate, exposure scenarios, and a process-based plant growth simulator was a useful approach for evaluating effectiveness of current or proposed air quality standards, or evaluating the form and/or level of a standard based on preventing adverse growth effects.     

In situ iron activated persulfate oxidative fluid sparging treatment of TCE contamination--a proof of concept study

In situ chemical oxidation (ISCO) is considered a reliable technology to treat groundwater contaminated with high concentrations of organic contaminants. An ISCO oxidant, persulfate anion (S(2)O(8)(2-)) can be activated by ferrous ion (Fe(2+)) to generate sulfate radicals (E(o)=2.6 V), which are capable of destroying trichloroethylene (TCE). The property of polarity inhibits S(2)O(8)(2-) or sulfate radical (SO(4)(-)) from effectively oxidizing separate phase TCE, a dense non-aqueous phase liquid (DNAPL). Thus the oxidation primarily takes place in the aqueous phase where TCE is dissolved. A bench column study was conducted to demonstrate a conceptual remediation method by flushing either S(2)O(8)(2-) or Fe(2+) through a soil column, where the TCE DNAPL was present, and passing the dissolved mixture through either a Fe(2+) or S(2)O(8)(2-) fluid sparging curtain. Also, the effect of a solubility enhancing chemical, hydroxypropyl-beta-cyclodextrin (HPCD), was tested to evaluate its ability to increase the aqueous TCE concentration. Both flushing arrangements may result in similar TCE degradation efficiencies of 35% to 42% estimated by the ratio of TCE degraded/(TCE degraded+TCE remained in effluent) and degradation byproduct chloride generation rates of 4.9 to 7.6 mg Cl(-) per soil column pore volume. The addition of HPCD did greatly increase the aqueous TCE concentration. However, the TCE degradation efficiency decreased because the TCE degradation was a lower percentage of the relatively greater amount of dissolved TCE by HPCD. This conceptual treatment may serve as a reference for potential on-site application.     

Major and trace elements of selected pedons in the USA

Few studies of soil geochemistry over large geographic areas exist, especially studies encompassing data from major pedogenic horizons that evaluate both native concentrations of elements and anthropogenically contaminated soils. In this study, pedons (n = 486) were analyzed for trace (Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) and major (Al, Ca, Fe, K, Mg, Na, P, Si, Ti, Zr) elements, as well as other soil properties. The objectives were to (i) determine the concentration range of selected elements in a variety of U.S. soils with and without known anthropogenic additions, (ii) illustrate the association of elemental source and content by assessing trace elemental content for several selected pedons, and (iii) evaluate relationships among and between elements and other soil properties. Trace element concentrations in the non-anthropogenic dataset (NAD) were in the order Mn > (Zn, Cr, Ni, Cu) > (Pb, Co) > (Cd, Hg), with greatest mean total concentrations for the Andisol order. Geometric means by horizon indicate that trace elements are concentrated in surface and/or B horizons over C horizons. Median values for trace elements are significantly higher in surface horizons of the anthropogenic dataset (AD) over the NAD. Total Al, Fe, cation exchange capacity (CEC), organic C, pH, and clay exhibit significant correlations (0.56, 0.74, 0.50, 0.31, 0.16, and 0.30, respectively) with total trace element concentrations of all horizons of the NAD. Manganese shows the best inter-element correlation (0.33) with these associated total concentrations. Total Fe has one of the strongest relationships, explaining 55 and 30% of the variation in total trace element concentrations for all horizons in the NAD and AD, respectively.