Sorption and desorption of benzo(a)pyrene in aquatic systems

The sorptive behaviour of polycyclic aromatic hydrocarbons (PAHs) is critical to controlling their transport, fates and effects in the environment. Experiments are described which detail the behaviour of a model compound (benzo(a)pyrene) under simulated aquatic conditions. The kinetics of sorption were comparable to those of other PAH compounds. The sorption equilibrium was extensively studied and found to be affected by several key parameters, notably sediment concentration. The sorption coefficient decreased substantially with the sediment concentration, from 9580 ml g(-1) at a sediment concentration of 0.067 g l(-1) to 1,110 ml g(-1) at a sediment concentration of 9.8 g l(-1). The results are consistent with previous reports and often explained by the presence of colloids. In this paper the dry weight concentration of colloids was determined and used for deriving the true sorption coefficient, which is up to an order of magnitude higher than the observed partition coefficient. The sorption of benzo(a)pyrene was also dependent on some of the particle properties, and the sorption coefficient was found to increase with the organic carbon content and specific surface area of sediment particles. The desorption of benzo(a)pyrene from sediment was shown to be relatively rapid, with implications for the potential remobilisation of benzo(a)pyrene and similar compounds.     

Regional scale evidence for improvements in surface water chemistry 1990-2001

The main aim of the international UNECE monitoring program ICP Waters under the Convention of Long-range Transboundary Air Pollution (CLRTAP) is to assess, on a regional basis, the degree and geographical extent of the impact of atmospheric pollution, in particular acidification, on surface waters. Regional trends are calculated for 12 geographical regions in Europe and North America, comprising 189 surface waters sites. From 1990-2001 sulphate concentrations decreased in all but one of the investigated regions. Nitrate increased in only one region, and decreased in three North American regions. Improvements in alkalinity and pH are widely observed. Results from the ICP Waters programme clearly show widespread improvement in surface water acid-base chemistry, in response to emissions controls programs and decreasing acidic deposition. Limited site-specific biological data suggest that continued improvement in the chemical status of acid-sensitive lakes and streams will lead to biological recovery in the future.     

Electrokinetic ion transport through unsaturated soil: 2. Application to a heterogeneous field site

Results of a field demonstration of electrokinetic transport of acetate through an unsaturated heterogeneous soil are compared to numerical modeling predictions. The numerical model was based on the groundwater flow and transport codes MODFLOW and MT3D modified to account for electrically induced ion transport. The 6-month field demonstration was conducted in an unsaturated layered soil profile where the soil moisture content ranged from 4% to 28% (m3 m(-3)). Specially designed ceramic-cased electrodes maintained a steady-state moisture content and electric potential field between the electrodes during the field demonstration. Acetate, a byproduct of acetic acid neutralization of the cathode electrolysis reaction, was transported from the cathode to the anode by electromigration. Field demonstration results indicated preferential transport of acetate through soil layers exhibiting higher moisture content/electrical conductivity. These field transport results agree with theoretical predictions that electromigration velocity is proportional to a power function of the effective moisture content. A numerical model using a homogeneous moisture content/electrical conductivity domain did not adequately predict the acetate field results. Numerical model predictions using a three-layer electrical conductivity/moisture content profile agreed qualitatively with the observed acetate distribution. These results suggest that field heterogeneities must be incorporated into electrokinetic models to predict ion transport at the field-scale.     

Niche complementarity due to plasticity in resource use: plant partitioning of chemical N forms

Niche complementarity, in which coexisting species use different forms of a resource, has been widely invoked to explain some of the most debated patterns in ecology, including maintenance of diversity and relationships between diversity and ecosystem function. However, classical models assume resource specialization in the form of distinct niches, which does not obviously apply to the broadly overlapping resource use in plant communities. Here we utilize an experimental framework based on competition theory to test whether plants partition resources via classical niche differentiation or via plasticity in resource use. We explore two alternatives: niche preemption, in which individuals respond to a superior competitor by switching to an alternative, less-used resource, and dominant plasticity, in which superior competitors exhibit high resource use plasticity and shift resource use depending on the competitive environment. We determined competitive ability by measuring growth responses with and without neighbors over a growing season and then used 15N tracer techniques to measure uptake of different nitrogen (N) forms in a field setting. We show that four alpine plant species of differing competitive abilities have statistically indistinguishable uptake patterns (nitrate > ammonium > glycine) in their fundamental niche (without competitors) but differ in whether they shift these uptake patterns in their realized niche (with competitors). Competitively superior species increased their uptake of the most available N form, ammonium, when in competition with the rarer, competitively inferior species. In contrast, the competitively inferior species did not alter its N uptake pattern in competition. The existence of plasticity in resource use among the dominant species provides a mechanism that helps to explain the manner by which plant species with broadly overlapping resource use might coexist.     

Behavioral strategies of American kestrels during mate replacement

Summary To determine the influence of mate replacement on the behavior and reproductive success of wild American kestrels (Falco sparverius) we removed 4 female and 16 male members of breeding pairs during incubation in 1983 and 1984. Eight males and 1 female were replaced within a mean time of 43 h. Widowed females that received a replacement spent less time hunting, but incubated and performed aerial displays more frequently than females that did not receive a replacement. After replacement, widowed females continued to incubate the original clutch, yet copulated and performed other courtship behaviors with the incoming male. Overlapping of normal temporally separate behavioral cues may be a female strategy to gain assistance from a replacement mate. However, none of the original clutches was successfully hatched. Of 8 pairs with replacement males, 2 pairs abandoned their territory, two remained on territory but did not renest, and 4 renested within a mean interval of 18 days. The lone female replacement and her mate copulated and performed nest inspections but then abandoned the territory. Incubation behavior was similar between replacement and control pairs; however, replacement males fed more invertebrate prey to nestling and made many more nest visits. All 3 replacement nests that hatched young failed within 8 days.     

Disaster studies inside out

Disaster studies is faced with a fascinating anomaly: frequently it claims to be critical and innovative, as suggested by the so‐called vulnerability paradigm that emerged more than 40 years ago, yet often it is perpetuating some of the core and problematic tenets of the hazard paradigm that we were asked to challenge initially. This paper interrogates why such an anomaly persists. In so doing, it employs Antonio Gramsci's concept of hegemony to unpack why disaster studies is still dominated by Western epistemologies and scholars that perpetuate an orientalist view of disasters. Ultimately, it suggests a research agenda for the 40 years to come, which builds on the importance of local researchers analysing local disasters using local epistemologies, especially in the non‐Western world. Such subaltern disaster studies are to be fuelled by increasing consciousness of the need to resist the hegemony of Western scholarship and to relocate disaster studies within the realm of its original political agenda.     

FINANCING ABATEMENT OF MINE DRAINAGE POLLUTION: CASE STUDY APPALACHIA1

ABSTRACT A financing program for the prevention, control, and abatement of mine drainage pollution was developed using Appalachia as a case example. The financing program was selected by using three performance criteria in a screening process-applicability of financing program to pollution problem, feasibility of program to unit costs and capturing potential benefits, and feasibility of program to economic and legal consideration. Effluent charges with some modifications are suggested as the appropriate financing mechanism.