Field demonstration of the combined effects of absorption and evapotranspiration on septic system drainfield capacity.

Drainfields for disposal of septic tank effluents are typically designed by considering the loss of water by either upward evapotranspiration into the atmosphere or lateral and downward absorption into the adjacent soil. While this approach is appropriate for evapotranspiration systems, absorption systems allow water loss by both mechanisms. It was proposed that, in areas where high evapotranspiration rates coincide with permeable soils, drainfield sizes could be substantially reduced by accounting for both mechanisms. A two-year field demonstration was conducted to determine appropriate design criteria for areas typical of the Texas High Plains. The study consisted of evaluating the long-term acceptance rates for three different drainfield configurations: evapotranspiration only, absorption only, and combined conditions. A second field demonstration repeated the experiments for additional observation of the combined evapotranspiration and absorption and achieved similar results as the first study. The field tests indicated that the current design loading criteria may be increased by at least a factor of two for the Texas High Plains region and other Texas areas with similar soil composition and evapotranspiration rates, while still retaining a factor of safety of two.     

The Precautionary Principle and the Prevention of Marine Pollution

This paper argues that the environmental changes witnessed in the past decade call for a new approach to environmental management; an approach based not on the principle of the assimilative capacity of the environment but on the precautionary principle, and the emerging preventive environmental paradigm. Uncertainties in scientific knowledge and complexities in ecological systems have presented specific failures of the assimilative capacity methodology. It is argued that these failures are not circumstantial in nature, nor are they the result of misapplication of science by scientists. Rather, they represent inherent problems in the use of the assimilative capacity concept in environmental management. The emergence of the precautionary principle is discussed and a formulation of the principle is presented. In conjunction with the operational approach of clean production, we believe that this principle offers a sounder basis for the prevention of marine pollution in the next decade.     

Evaluating colloidal phosphorus delivery to surface waters from diffuse agricultural sources

Colloid-facilitated phosphorus (P) delivery from agricultural soils in different hydrological pathways was investigated using a series of laboratory and field experiments. A soil colloidal P test was developed that yields information on the propensity of different soils to release P attached to soil colloids. The relationship between turbidity of soil extracts and total phosphorus (TP) was significant (r2 = 0.996, p < 0.001) across a range of agricultural soils, and a strong positive relationship (r2 = 0.86, p < 0.001) was found between "colloidal P" (H2O-CaCl2 extracts) and turbidity. Linear regression of the proportion of fine clay (<2 microm) for each soil type evaluated against the (H2O-CaCl2) colloidal P fraction gave a weak but positive relationship (r2 = 0.38, p = 0.082). The relative contribution of different particle-size fractions in transporting P in agricultural runoff from grassland soils was evaluated using a randomized plot experiment. A significant difference (p = 0.05) in both TP and reactive phosphorus (RP) in subsurface flow was recorded for different particle-size fractions, with most TP transferred either in association with the 2-microm fraction or with the 0.001-microm or smaller fractions. Total P concentrations in runoff were higher from plots receiving P amendments compared with the zero-P plots; however, these differences were only significant for the >0.45-microm particle-size fractions (p = 0.05), and may be evidence of surface applications of organic and inorganic fertilizers being transferred through the soil either as intact organic colloids or attached to mineral particles. Our results highlight the potential for drainage water to mobilize colloids and associated P during rainfall events.     

The measurement of experienced burnout

A scale designed to assess various aspects of the burnout syndrome was administered to a wide range of human services professionals. Three subscales emerged from the data analysis: emotional exhaustion, depersonalization, and personal accomplishment. Various psychometric analyses showed that the scale has both high reliability and validity as a measure of burnout.     

Potential nitrogen constraints on soil carbon sequestration under low and elevated atmospheric CO2

The interaction between nitrogen cycling and carbon sequestration is critical in predicting the consequences of anthropogenic increases in atmospheric CO2 (hereafter, Ca). The progressive N limitation (PNL) theory predicts that carbon sequestration in plants and soils with rising Ca may be constrained by the availability of nitrogen in many ecosystems. Here we report on the interaction between C and N dynamics during a four-year field experiment in which an intact C3/C4 grassland was exposed to a gradient in Ca from 200 to 560 micromol/mol. There were strong species effects on decomposition dynamics, with C loss positively correlated and N mineralization negatively correlated with Ca for litter of the C3 forb Solanum dimidiatum, whereas decomposition of litter from the C4 grass Bothriochloa ischaemum was unresponsive to Ca. Both soil microbial biomass and soil respiration rates exhibited a nonlinear response to Ca, reaching a maximum at approximately 440 micromol/mol Ca. We found a general movement of N out of soil organic matter and into aboveground plant biomass with increased Ca. Within soils we found evidence of C loss from recalcitrant soil C fractions with narrow C:N ratios to more labile soil fractions with broader C:N ratios, potentially due to decreases in N availability. The observed reallocation of N from soil to plants over the last three years of the experiment supports the PNL theory that reductions in N availability with rising Ca could initially be overcome by a transfer of N from low C:N ratio fractions to those with higher C:N ratios. Although the transfer of N allowed plant production to increase with increasing Ca, there was no net soil C sequestration at elevated Ca, presumably because relatively stable C is being decomposed to meet microbial and plant N requirements. Ultimately, if the C gained by increased plant production is rapidly lost through decomposition, the shift in N from older soil organic matter to rapidly decomposing plant tissue may limit net C sequestration with increased plant production.     

Effect of 2,4-D contamination on soil functional stability evaluated using the relative soil stability index (RSSI)

Soil functional stability is the capacity of soil functions to resist and recover from an environmental perturbation and can be used to evaluate soil health. It can be influenced by the presence of xenobiotics such as herbicides. The impact of a fresh 2,4-D contamination (36 mg kg(-1) dry soil) on soil functional stability was evaluated by comparing the capacity of soil enzyme activities to resist and recover from a heat perturbation for both a clean and 2,4-D-contaminated soil. The functional stabilities of the soils (uniform sands, pH 6.9, 7% (w/w) organic matter) were calculated using the relative soil stability index (RSSI). The RSSI scores indicate the proportion of potential enzyme activity the soil retains after a perturbation compared to the potential activity of an unperturbed soil. Six extra-cellular enzyme activities (acid and alkaline phosphatases, arylsulfatase, urease, protease and beta-glucosidase) were monitored in soil microcosms during a 15-day period. During this period, a 60 degrees C heat perturbation was applied to the soil for 24 h. The activities of arylsulfatase and protease were found to be the most stable following heat perturbation obtaining the highest RSSI scores (87% and 77%, respectively). Urease activity showed the lowest RSSI score (38%). Although all enzyme activities were inhibited by the presence of 2,4-D, the RSSI results indicated that contamination lowered the stability of only three enzyme activities (arylsulfatase, beta-glucosidase and urease). The RSSI adequately described resistance, recovery and recovery rate parameters and enabled differentiation between functional stabilities of clean and contaminated soil and between different soil types.     

Making a significant difference with burnout interventions: Researcher and practitioner collaboration

Burnout research over the past 30 years has yielded both knowledge and tools to apply to interventions at unit and organizational levels. Examples of innovative partnerships between researchers and practitioners point to the importance of multi‐level approaches in generating relevant and effective solutions to the burnout problem. Copyright © 2011 John Wiley & Sons, Ltd.     

Realistic evaluation as a new way to design and evaluate occupational safety interventions

Recent debates regarding the criteria for evaluating occupational health and safety interventions have focused on the need for incorporating qualitative elements and process evaluation, in addition to attempting to live up to the Cochrane criteria. Reflecting fundamental epistemological conflicts and shortcomings of the Cochrane criteria in evaluating intervention studies, the debate challenges the traditional (quasi-) experimental design and methodology, which are often used within safety research. This article discusses a revised ‘realistic evaluation’ approach as a way to meet these challenges.Evidence from the literature as well as examples from an integrated (leader-based/worker-based) safety intervention study (2008-2010) in a large wood manufacturing company are presented, with focus on the pros and cons of using randomised-controlled-trials and a revised realistic evaluation model.A revised realistic evaluation model is provided which includes factors such as role behaviour, leader and worker motivation, underreporting of accidents/injuries, production pressure, unplanned organisational change and accounting for multilayer effects. These can be attained through qualitative and/or quantitative methods, allowing for the use of realistic evaluation in both large and small scale studies, as well as in systematic reviews. The revised realistic evaluation model offers a promising new way of designing and evaluating occupational safety research. This model can help safety science move forward in setting qualitative and/or quantitative criteria regarding context, mechanisms and processes for single studies and for reviews. Focus is not limited to whether the expected results appear or not, but include suggestions for what works for whom, under what circumstances, in what respects and how.