The application of HPLC-F and GC-MS to the analysis of selected hydroxy polycyclic hydrocarbons in two certified fish bile reference materials

Four selected hydroxy polycyclic aromatic hydrocarbons (OH-PAHs), 2-hydroxy-naphthalene (2-OH-NPH), 1-hydroxy-phenanthrene (1-OH-PHE), 1-hydroxy-pyrene (1-OH-PYR) and 3-hydroxy-benzo[a]pyrene (3-OH-BaP) have been analysed in two certified fish bile reference materials (CRMs) for exposure monitoring of PAHs in the aquatic environment. The two materials, BCR 720 and BCR 721, consist of bile from fish exposed to contaminated sediment and dispersed crude oil, respectively. Both bile samples have been analysed by two different analytical techniques, gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography-fluorescence detection (HPLC-F), and the separation performance, detection limits, recoveries and reproducibility for the four target compounds were evaluated. HPLC-F requires a simple sample preparation and the separation capacity is adequate for quantification of 1-OH-PYR and 3-OH-BaP. Detection limits are excellent for 1-OH-PYR (6 pg injected) and 3-OH-BaP (3 pg injected) and generally improved with increasing molecular size. Recoveries ranged from 48 to 99% for the four selected compounds, depending on compound and concentration. Sample preparation prior to GC-MS analysis was more demanding, as reflected by the obtained recoveries for 2-OH-NPH, 1-OH-PHE and 1-OH-PYR (35 to 61%). The sensitivity improved with decreasing molecular size, 2-OH-NPH (1.2 pg injected), 1-OH-PHE (2.4 pg injected) and 1-OH-PYR (6 pg injected). Because of the superior separation power of GC and the extra selectivity of MS detection, GC-MS was the method of choice for the determination of 2-OH-NPH and 1-OH-PHE in both CRMs. In fish bile samples these two compounds are more likely to suffer from chromatographic overlap, and HPLC-F was not sufficiently selective. Determination of 1-OH-PYR was performed with success by both methods, but HPLC-F would be preferred because of the simpler and less time-consuming sample preparation. Detectable concentrations of 3-OH-BaP were present in BCR 720 and could only be determined by HPLC-F. The present work aims to present HPLC-F and GC-MS as complementary methods for the quantitative analysis of OH-PAHs in fish bile.     

Temperature-Dependent Persistence of Human Norovirus Within Oysters (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>)

This study characterizes the persistence of human norovirus in Eastern oysters (Crassostrea virginica) held at different seawater temperatures. Oysters were contaminated with human norovirus GI.1 (Norwalk strain 8FIIa) by exposing them to virus-contaminated water at 15 °C, and subsequently holding them at 7, 15, and 25 °C for up to 6 weeks. Viral RNA was extracted from oyster tissue and hemocytes and quantitated by RT-qPCR. Norovirus was detected in hemocytes and oysters held at 7 and 15 °C for 6 weeks and in hemocytes and oysters held at 25 °C for up to 2 and 4 weeks, respectively. Results confirm that NoV is quite persistent within oysters and demonstrate that cooler water temperatures extend norovirus clearance times. This study suggests a need for substantial relay times to remove norovirus from contaminated shellfish and suggests that regulatory authorities should consider the effects of water temperature after a suspected episodic norovirus-contamination event.     

The mediating role of job characteristics in job redesign interventions: A serendipitous quasi‐experiment

The aim of this paper is to examine the mediating role played by five key job characteristics in the relationship between employee participation in a job redesign intervention and employee well‐being. In studies of job redesign interventions, it has been assumed that any effects of employee participation in job redesign on well‐being are a result of changes in job characteristics rather than participation in change per se. It is therefore important to statistically test for mediation in job redesign intervention studies to help establish that the change in job characteristics is the mechanism through which job redesign interventions work. However, this has rarely been tested directly, either because data to allow tests of mediation have not been collected (e.g. assessments of job characteristics) or because data have been collected but mediation has not been tested using accepted procedures. This makes it unclear whether changes in job characteristics explain the effects. Results from multilevel analyses of a longitudinal 9‐month long serendipitous quasi‐experimental participative job redesign intervention showed that changes in job control, participation, skill utilization and feedback, but not task obstacles, were sufficient to account for the relationship between the intervention and employee well‐being. Copyright © 2009 John Wiley & Sons, Ltd.     

Sulfide elimination by intermittent nitrate dosing in sewer sediments

The formation of hydrogen sulfide in biofilms and sediments in sewer systems can cause severe pipe corrosions and health hazards, and requires expensive programs for its prevention. The aim of this study is to propose a new control strategy and the optimal condition for sulfide elimination by intermittent nitrate dosing in sewer sediments. The study was carried out based on lab-scale experiments and batch tests using real sewer sediments. The intermittent nitrate dosing mode and the optimal control condition were investigated. The results indicated that the sulfide-intermittent-elimination strategy by nitrate dosing is advantageous for controlling sulfide accumulation in sewer sediment. The oxidation–reduction potential is a sensitive indicator parameter that can reflect the control effect and the minimum N/S(nitrate/sulfide)ratio with slight excess nitrate is necessary for optimal conditions of efficient sulfide control with lower carbon source loss. The optimal control condition is feasible for the sulfide elimination in sewer systems.     

Air pollutant concentrations near three Texas roadways, part II: Chemical characterization and transformation of pollutants

Spatial gradients of vehicular emitted air pollutants were measured in the vicinity of three roadways in the Austin, Texas area: (1) State Highway 71 (SH-71), a heavily traveled arterial highway dominated by passenger vehicles; (2) Interstate 35 (I-35), a limited access highway north of Austin in Georgetown; and (3) Farm to Market Road 973 (FM-973), a heavily traveled surface roadway with significant truck traffic. A mobile monitoring platform was used to characterize the gradients of CO and NO_x concentrations with increased distance from each roadway, while concentrations of carbonyls in the gas-phase and fine particulate matter mass and composition were measured at stationary sites upwind and at one (I-35 and FM-973) or two (SH-71) downwind sites. Regardless of roadway type or wind direction, concentrations of carbon monoxide (CO), nitric oxide (NO), and oxides of nitrogen (NO_x) returned to background levels within a few hundred meters of the roadway. Under perpendicular wind conditions, CO, NO and NO_x concentrations decreased exponentially with increasing distance perpendicular to the roadways. The decay rate for NO was more than a factor of two greater than for CO, and it comprised a larger fraction of NO_x closer to the roadways than further downwind suggesting the potential significance of near roadway chemical processing as well as atmospheric dilution. Concentrations of most carbonyl species decreased with distance downwind of SH-71. However, concentrations of acetaldehyde and acrolein increased farther downwind of SH-71, suggesting chemical generation from the oxidation of primary vehicular emissions. The behavior of particle-bound organic species was complex and further investigation of the size-segregated chemical composition of particulate matter (PM) at increasing downwind distances from roadways is warranted. Fine particulate matter (PM_2.5) mass concentrations, polycyclic aromatic hydrocarbons (PAHs), hopanes, and elemental carbon (EC) concentrations generally exhibited concentrations that decreased with distance downwind of SH-71. Concentrations of organic carbon (OC) increased from upwind concentrations immediately downwind of SH-71 and continued to increase further downwind from the roadway. This behavior may have primarily resulted from condensation of semi-volatile organic species emitted from vehicle sources with transport downwind of the roadway.     

Cation exchange in a glacial till drumlin at a road salt storage facility

At a former wood preservation plant severely contaminated with coal tar oil, in situ bulk attenuation and biodegradation rate constants for several monoaromatic (BTEX) and polyaromatic hydrocarbons (PAH) were determined using (1) classical first order decay models, (2) Michaelis–Menten degradation kinetics (MM), and (3) stable carbon isotopes, for o-xylene and naphthalene. The first order bulk attenuation rate constant for o-xylene was calculated to be 0.0025 d^− 1 and a novel stable isotope-based first order model, which also accounted for the respective redox conditions, resulted in a slightly smaller biodegradation rate constant of 0.0019 d^− 1. Based on MM-kinetics, the o-xylene concentration decreased with a maximum rate of k_max = 0.1 µg/L/d. The bulk attenuation rate constant of naphthalene retrieved from the classical first order decay model was 0.0038 d^− 1. The stable isotope-based biodegradation rate constant of 0.0027 d^− 1 was smaller in the reduced zone, while residual naphthalene in the oxic part of the plume further downgradient was degraded at a higher rate of 0.0038 d^− 1. With MM-kinetics a maximum degradation rate of k_max = 12 µg/L/d was determined. Although best fits were obtained by MM-kinetics, we consider the carbon stable isotope-based approach more appropriate as it is specific for biodegradation (not overall attenuation) and at the same time accounts for the dominant electron-accepting process. For o-xylene a field based isotope enrichment factor ε_field of − 1.4 could be determined using the Rayleigh model, which closely matched values from laboratory studies of o-xylene degradation under sulfate-reducing conditions.     

The effects of scale and spatial heterogeneities on diffusion in volcanic breccias and basalts: Amchitka Island, Alaska

Knowledge of the factors that influence the diffusion of contaminants, such as the diffusivity and the connected porosity, is crucial to modeling the long-term fate and transport of contaminants in subsurface systems with small or negligible advective flow, such as in fractured crystalline rock. Fractured rock is naturally heterogeneous, and hence, understanding the diffusivity of a molecule through this material (or the formation factor of the medium) becomes a complex problem, with critical concerns about the scale of laboratory measurements and about the spatial variability of these measurements relative to the scale needed for fate and transport modeling. This study employed both electrical and tracer-based laboratory methods to investigate the effects of scale and pore system connectivity on the diffusivity for volcanic matrix rock derived from the study site, a former underground nuclear test site at Amchitka Island, Alaska. The results of these investigations indicate a relatively well-connected pore system with scale effects generally limited to approximately 6 cm lengths and well-correlated to observed heterogeneous features. An important conclusion resulting from this study, however, is that there is a potential for the estimated diffusivity to be misrepresented by an order of magnitude if multiple samples or longer sample lengths are not used. Given the relatively large number of measurements resulting from these investigations, an analysis of the probability density function (PDF) of the diffusivity was possible. The PDF of the diffusivity was shown to generally follow a normal distribution for individual geologic layers. However, when all of the geologic layers are considered together, the distribution of the subsurface as a whole was shown to follow a lognormal distribution due to the order of magnitude differences amongst the layers. An understanding of these distributions is essential for future stochastic modeling efforts.