The impact of vegetation on sedimentary organic matter composition and PAH desorption

Relationships between sedimentary organic matter (SOM) composition and PAH desorption behavior were determined for vegetated and non-vegetated refinery distillate waste sediments. Sediments were fractionated into size, density, and humin fractions and analyzed for their organic matter content. Bulk sediment and humin fractions differed more in organic matter composition than size/density fractions. Vegetated humin and bulk sediments contained more polar organic carbon, black carbon, and modern (plant) carbon than non-vegetated sediment fractions. Desorption kinetics of phenanthrene, pyrene, chrysene, and C₃-phenanthrene/anthracenes from humin and bulk sediments were investigated using Tenax^® beads and a two-compartment, first-order kinetic model. PAH desorption from distillate waste sediments appeared to be controlled by the slow desorbing fractions of sediment; rate constants were similar to literature values for k_slow and k_{very slow}. After several decades of plant colonization and growth (Phragmites australis), vegetated sediment fractions more extensively desorbed PAHs and had faster desorption kinetics than non-vegetated sediment fractions.     

Water quality impacts on sorbent efficacy for per- and polyfluoroalkyl substances treatment of groundwater

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic compounds that have emerged as chemicals of concern in drinking water and groundwater. Typically, such waters are treated to remove PFAS by passing the water through a bed of sorbent material (e.g., activated carbon and anion exchange resins [AIX]). However, the efficacy of these sorbents varies depending on the types and concentrations of PFAS, in addition to water quality conditions such as organic matter content and conductivity (ionic strength). The choice of sorbent material to effectively treat PFAS in complex natural waters will, therefore, depend upon site water quality and PFAS conditions. To help inform these decisions, a series of evaluations using a rapid small-scale column test approach was conducted with two sorbent materials (a granulated activated carbon [GAC] and an AIX), individually and combined, under conditions where conductivity, pH, and organic carbon concentrations were varied in a semifactorial approach. Artificial groundwater batches were prepared to meet these test conditions and spiked with six PFAS compounds (perfluorobutane sulfonic acid [PFBS], perfluorobutanoic acid [PFBA], perfluorohexane sulfonic acid [PFHxS], perfluorohexanoic acid [PFHxA], perfluorooctane sulfonic acid [PFOS], and perfluorooctanoic acid [PFOA]), passed through small columns packed with ground sorbent material for ∼30,000 bed volumes of water for single sorbent treatments and ∼20,000 bed volumes for combined sorbent treatments, during which samples of effluent were captured and analyzed to quantify breakthrough of PFAS from the sorbent materials over time. AIX was found to be more effective than GAC at removing the tested perfluoroalkyl sulfonic acids (PFBS, PFHxS, and PFOS), but GAC was similarly or more effective than AIX at removing perfluorocarboxylic acids (PFBA, PFHxA, and PFOA) under high conductivity conditions. Overall, the efficacy of AIX at removing PFAS was more strongly impacted by organic carbon and conductivity than GAC, while pH had less of an effect on either sorbent's efficacy compared to the other test conditions.     

An observational case study of ozone and precursors inflow to South East England during an anticyclone

Summertime photochemical air pollution episodes within the United Kingdom have been proposed via modelling studies to be strongly influenced by regional scale inflow of air from the continental European boundary layer. We present a vertically resolved case study using measurements made from the NERC/Met Office BAe 146 research aircraft on 18th August 2005 over the South East of England and the North Sea during a weak anticyclone centred over Northern Europe. The vertical distribution of ozone, CO, NO(x), peroxyacetyl nitrate (PAN) and a wide range of both nonmethane hydrocarbons (NMHC) and oxygenated volatile organic compounds (OVOCs) were determined between 500 ft (approximately 152 m) and 7000 ft (approximately 2134 m) over the East Anglia coastline and 50 km inland. In excess of 80 ppbV ozone was observed within inflowing boundary layer air over the North Sea coast in a broad N-S sloping feature around 60 km wide. The inflowing feature of European origin was also observed further inland within the boundary layer albeit with lower, more variable, ozone mixing ratios. The increased variability in ozone over land was a product of titration by fresh surface emissions of NO via rapid upward transport in thermals, a hypothesis supported by the observed vertical wind speed component. Fast boundary layer mixing over land was further illustrated by a uniform distribution in reactive alkenes. A comparison between aircraft and surface O(3) UK AUN (Automatic Urban Network) measurements showed good agreement with the inland site, Sibton, but marked differences with the coastal monitoring site at Weybourne, potentially due to gradients established by ocean deposition in stably stratified marine air.     

Hierarchical regulation of nitrogen export from urban catchments: interactions of storms and landscapes.

In urban catchments of arid central Arizona, we investigate how the export of mineral and organic nitrogen (N) in storm runoff is regulated by interactions between local landscape characteristics and broader scale storm features. First, we test whether N export is more a function of (1) processes that affect N concentration in runoff or (2) the propensity of the catchment to convey rainfall as runoff. With data pooled across catchments, the mass of N in export (load) is determined by processes regulating runoff N concentration. There are exceptions when catchments are examined individually, where N load from some catchments is determined by the hydrologic responsiveness of the catchment. Second, we investigate the relationship between N export and catchment features. Loads per catchment area were greater from more impervious catchments, probably because impervious catchments held more N in a mobilizable phase and conveyed more rainfall as overland flow. Loads per area were lower from larger catchments, possibly owing to more N-retention hot spots in larger catchments. Catchments with the greatest N exports were those with commercial land use, and loads decreased as development became less prevalent or as residential replaced industrial land use. Third, we investigated how catchment features moderated direct responses of N export to storms. Export was less correlated with storm features in catchments that were larger, more pervious, and less industrial. Results support an "N build and flush" hypothesis, which purports that there is little biotic processing of N deposited to arid, urban surfaces with little organic matter. The rate and duration of deposition determine the size of the mobile N pool. Any amount of rainfall capable of generating overland flow would entrain nearly all mobilizable N and export it from the catchment. Nonetheless, these results suggest that, even with daunting seasonal and interannual variability in storm conditions, material export can be reduced by managing intrinsic catchment features.     

Variation in uptake of serum screening: the role of service delivery

The present study aimed to determine the extent to which variation in the uptake of serum screening for Down syndrome reflects variation in the way the test is offered. A higher uptake of serum screening was seen at hospitals that offered the blood test as part of a routine visit than at those where screening required a separate visit. The type of screening test offered and whether a reminder was sent were not associated with uptake. Given the consensus that undergoing screening should be the result of an informed choice, further research is needed to determine which methods of offering serum screening facilitate and which impede informed choice. Copyright © 2002 John Wiley & Sons, Ltd.     

Curtin industrial safety trial: Managerial behavior and program effectiveness

Behavior-based safety has been found universally efficacious when evaluated under controlled conditions. The Curtin Trial aimed to test the general acceptability of behavior-based safety in Australian industry. A 50% failure rate was observed. This paper presents the results of a qualitative analysis of observed managerial behavior in relation to program effectiveness. Field notes taken in the course of 325 hours of participant observation during implementation of behavior-based safety in 9 work areas were analyzed qualitatively and categorized. These data were compared with statistical results of the safety program's effectiveness on improving safe practices and good housekeeping. Nine dimensions to managerial behavior were identified which were associated with program effectiveness. A relatively small number of studies investigating organizational characteristics and safety have found generally similar social environmental features to those observed in this study. Behavior-based safety appears to be effective only in organizations with recognizable managerial styles.     

ESTIMATING EROSION RISKS ASSOCIATED WITH LOGGING AND FOREST ROADS IN NORTHWESTERN CALIFORNIA1

ABSTRACT: Erosion resulting from logging and road building has long been a concern to forest managers and the general public. An objective methodology was developed to estimate erosion risk on forest roads and in harvest areas on private land in northwestern California. It was based on 260 plots sampled from the area harvested under 415 Timber Harvest Plans completed between November 1978 and October 1979. Results confirmed previous findings that most erosion related to forest management occurs on a small fraction of the managed area. Erosion features larger than the minimum size inventories in this study (> 13 yd³) occupied only 0.2 percent of the area investigated. Linear discriminant analysis was used to develop two equations for identifying critical sites (sites with erosion >100 yd³ac^?1). The equations were based on slope, horizontal curvature (an expression of local topography), and soil color (on road sites) or the strength of the underlying rocks (on harvest sites). The equations can be used in planning to estimate the erosion risk of proposed activities. They can also be used to estimate acceptable risk thresholds based on the value of competing resources.