The effect of export to the deep sea on the long-range transport potential of persistent organic pollutants

Background

Export to the deep sea has been found to be a relevant pathway for highly hydrophobic chemicals. The objective of this study is to investigate the influence of this process on the potential for long-range transport (LRT) of such chemicals.

Methods

The spatial range as a measure of potential for LRT is calculated for seven PCB congeners with the multimedia fate and transport model ChemRange. Spatial ranges for cases with and without deep sea export are compared.

Results and Discussion

Export to the deep sea leads to increased transfer from the air to the surface ocean and, thereby, to lower spatial ranges for PCB congeners whose net deposition rate constant is similar to or greater than the atmospheric degradation rate constant. This is fulfilled for the PCB congeners 101, 153, 180, and 194. The spatial ranges of the congeners 8, 28, and 52, in contrast, are not affected by deep sea export. With export to the deep sea included in the model, the spatial ranges of the heavier congener are similar to those of the lighter ones, while the intermediate congeners 101 and 153 have the highest potential for long-range transport.

Conclusions

Transfer to the deep ocean affects the mass balance and the potential for LRT of highly hydrophobic chemicals and should be included in multimedia fate models containing a compartment for ocean water.     

Effects of Ceiling-Mounted HEPA-UV Air Filters on Airborne Bacteria Concentrations in an Indoor Therapy Pool Building

Abstract

The purpose of this study was to assess the effectiveness of a new generation of high-volume, ceiling-mounted high-efficiency particulate air (HEPA)-ultraviolet (UV) air filters (HUVAFs) for their ability to remove or inactivate bacterial aerosol. In an environmentally controlled full-scale laboratory chamber (87 m³), and an indoor therapy pool building, the mitigation ability of air filters was assessed by comparing concentrations of total bacteria, culturable bacteria, and airborne endotoxin with and without the air filters operating under otherwise similar conditions. Controlled chamber tests with pure cultures of aerosolized Mycobacterium parafortuitum cells showed that the HUVAF unit tested provided an equivalent air-exchange rate of 11 hr^?1. Using this equivalent air-exchange rate as a design basis, three HUVAFs were installed in an indoor therapy pool building for bioaerosol mitigation, and their effectiveness was studied over a 2-year period. The HUVAFs reduced concentrations of culturable bacteria by 69 and 80% during monitoring periods executed in respective years. The HUVAFs reduced concentrations of total bacteria by 12 and 76% during the same monitoring period, respectively. Airborne endotoxin concentrations were not affected by the HUVAF operation.     

Critical Loads of Acidity for Forest Soils: Tentative Modifications

We reviewed the current methods for calculatingcritical loads of acidity for forest soils. The consequencesof four sets of assumptions concerning the soil modelstructure, parameter values and the critical loads criterionwere explored by comparing the values of the averageaccumulated exceedance (AAE) calculated for Finland withdeposition values for the year 1995. The AAE index is given inthe unit of deposition and is a measure of how far a region isfrom being protected in terms of fulfilling a certaincriterion, taking into account the size of the ecosystem areas.Using a critical limit for the molar ratio of theconcentrations of base cations to aluminium in soil solutiongave the lowest average accumulated exceedance. Assumingorgano-aluminium complexes and leaching of organic anions gaveAAE = 4 eq ha^-1 a^-1, which was close to the valueobtained with the standard approach used in Finland, assuminggibbsite equilibrium and no leaching of organic anions,yielding AAE = 5 eq ha^-1 a^-1. With a critical basesaturation limit, instead of the concentrations criterion, theAAE index was 17 eq ha^-1 a^-1. The highest averageaccumulated exceedance (AAE = 25 eq ha^-1 a^-1),corresponding to the lowest critical load, was obtained whenthe effects-based criterion (critical concentration or criticalbase saturation) was substituted with one restricting thedeterioration of the neutralizing capacity of the soil, ANC _le(crit) = 0. These tests illustrate the variabilityof the critical load values for acidity that can be introducedby changing the criterion or by varying the calculation method,without, however, representing the extreme values of criticalloads that could be derived.     

Dynamic Cost-Effective Reduction Strategies for Acidification in Europe: An Application to Ireland and the United Kingdom

This paper describes the application of an optimisation model for calculating cost-effective abatement strategies for the reduction of acidification in Europe while taking into account the dynamic character of soil acidification in a number of countries. Environmental constraints are defined in terms of soil quality indicators, e.g., pH, base saturation or the aluminium ion concentration in the soil solution within an optimisation model for transboundary air pollution.We present a case study for Ireland and the United Kingdom. Our results indicate that reduction of sulphur dioxide emission is more cost-effective than that of nitrogen oxides or ammonia. The reduction percentages for sulphur dioxide are highest, for two reasons: (i) marginal sulphur dioxide reduction costs are relatively low compared to marginal reduction costs of nitrogen oxides and ammonia and (ii) sulphur dioxide reduction is more effective in reducing acidification in physical terms than nitrogen oxides or ammonia abatement. Our dynamic analysis shows that a (fast) improvement of soil quality requires high emission reduction levels. These reduction levels are often higher than reduction levels that are typically deduced from the static critical loads approach. Once soil quality targets are reached, in our model, less stringent emission reductions are required to maintain the soil quality at a constant and good target level. Static critical load approaches that ignore dynamic aspects therefore may underestimate the emission reductions needed to achieve predefined soil quality targets.     

Weak defence in a tritrophic system: olfactory response to salicylaldehyde reflects prey specialization of potter wasps

Predatory arthropods are attracted to infochemicals emitted by their herbivore prey or by the prey’s host plants. We studied such a tritrophic system measuring the olfactory responses of three potter wasp species (Symmorphus murarius, Symmorphus gracilis, Discoelius zonalis, Hymenoptera: Eumeninae) to salicylaldehyde, sequestered as a defence compound by Chrysomela leaf beetle larvae when feeding on Salicaceae, and volatile organic compounds (VOCs) emitted by aspen (Populus tremula, Salicaceae). In electroantennographic recordings (EAG), the highly specialized S. murarius that almost exclusively feeds on larvae of Salicaceae-feeding Chrysomela species was more sensitive to salicylaldehyde than the less specialized S. gracilis, feeding on such Chrysomela species but also weevil larvae. In contrast the related D. zonalis, foraging for microlepidoptera caterpillars on various host plants, did not respond at all. Furthermore, the three wasp species responded differently to aspen VOCs in GC–MS/EAD measurements. These results indicate that the sense of smell of predatory potter wasps differs for prey and plant volatiles among related wasp species according to their degree of host specialization. The considerable differences in salicylaldehyde perception suggest that its originally defensive function has backfired as it is used by specialist potter wasps for prey location. This is an important clue on adaptive mechanisms of the highest trophic level of the well-studied evolutionary arms race among Chrysomela leaf beetles, their host plants and their enemies.