A Field Intercomparison and Fundamental Characterization of Various Dust Samplers with a Reference Sampler

The European Economic Community Council Directive 80/779/EEC¹ describes air quality limit values and guide values for sulfur dioxide and suspended particulates. However, article 10, paragraph 1 does not define well enough the reference method required, amongst others, for the gravimetric measurement of suspended particulates. It is explicity stated in article 10, paragraph 5 of the directive, that “the commission shall, in selected locations in the member states and in cooperation with the latter, carry out studies on the sampling…of suspended particulates. These studies shall be designed in particular to promote the harmonization of methods of sampling and analysis of these pollutants.” Therefore, in a joint research program the Umweltbundesamt (grant #104 02263), the commission of European Communities (grant #84-B-6642-11-017-11-N) and the U.S. EPA (grant #2-43211-3580) funded the development of a reference dust sampler by the Fraunhofer-lnstitute of Toxicology and Aerosol Research (FhITA, in Hannover, Federal Republic of Germany) in order: ? to study the particle size distribution of ambient air aerosol at a number of selected sites;

? to compare the results obtained with the reference dust sampler with those of particle samplers operated in Europe and the United States;

? to verify the applicability of wind tunnel results to sampling behaviour in the free atmosphere.

     

Solar driven nitrous acid formation on building material surfaces containing titanium dioxide: A concern for air quality in urban areas?

The photoenhanced uptake of nitrogen dioxide (NO₂) to the surface of commercially available self-cleaning window glass has been studied under controlled laboratory conditions. This material is one of an array of modern building products which incorporate titanium dioxide (TiO₂) nanoparticles and are finding increasing use in populated urban areas. Amongst the principal drivers for the use of these materials is that they are thought to facilitate the irreversible removal of pollutants such as NO₂ and organic molecules from the atmosphere and thus act to remediate air quality. While it appears that TiO₂ materials do indeed remove organic molecules from built environments, in this study we show that the photoenhanced uptake of NO₂ to one example material, self-cleaning window glass, is in fact accompanied by the substantial formation (50–70%) of gaseous nitrous acid (HONO). This finding has direct and serious implications for the use of these materials in urban areas. Not only is HONO a harmful respiratory irritant, it is also readily photolysed by solar radiation leading to the formation of hydroxyl radicals (OH) together with the re-release of NO_x as NO. The net effect of subsequent OH initiated chemistry can then be the further degradation of air quality through the formation of secondary pollutants such as ozone and VOC oxidation products. In summary, we suggest that a scientifically conceived technical strategy for air quality remediation based on this technology, while widely perceived as universally beneficial, could in fact have effects precisely opposite to those intended.     

Limitations in the determination of maximum residue limits and highest residues of pesticides: Part I

The pesticide usages are controlled by comparing residue concentrations in treated commodities to legally permitted maximum levels (MRLs) determined based on supervised trials designed to reflect likely maximum residues occurring in practice following authorised use. The number of trials available may significantly affect the accuracy of estimated maximum residues. We conducted a study with synthetic lognormal distributions with mean of 1 and standard deviations of 0.8 and 1.0, which reflect the residue distributions observed in practice. The likely residues in samples were modelled by drawing random samples of size 3, 5, 10 and 25 from the synthetic populations. The results indicate that the estimations of highest residues (HR), used for calculation of short-term intake, and the MRLs, serving as legal limits, are very uncertain based on 3–5 trials indicated by the calculated HR_0.975/HR_0.025 and MRL_0.975/MRL_0.025 ratios of 12 and 9, and 13 and 10, respectively, which question the suitability of such trials for the intended purpose. As the 95% range of HR and MRL rapidly decreases with number of trials, ideally ≥15 but minimum 6–8 trials should be used for estimation of HR and MRL according to the current typical practice of Codex Alimentarius.     

Effect of tracer dyes on initial deposits and persistence of bacillus thuringiensis subsp. kurstaki toxin after application of two commercial formulations onto spruce trees

Abstract

The effect of two tracer dyes [Erio Acid Red (EAR) and Acid Black 48 (AB‐48)] on initial deposits and persistence of Bacillus thuringiensis subsp. kurstaki (Btk) toxin (delta‐endotoxin) was studied after spraying two commercial formulations, Foray® 48B and Foray® 76B, over potted white spruce [Picea glauca (Moench) Voss] seedlings, at a dosage rate of 30 billion international units (BIU) per ha. Spray was applied using a spinning disc atomizer calibrated to deliver droplet sizes similar to those utilized in ultra‐low‐volume (ULV) treatments in operational insect control programs. The sprayed seedlings were left outdoors at the Sault Ste. Marie laboratory for 18 days under natural conditions of sunlight, wind and rainfall. Initial deposits and persistence of delta‐endotoxin protein in spruce foliage were determined by immunoassay [enzyme linked immunosorbent assay (ELISA)] quantification of the delta‐endotoxin. The total protein (inactive plus active) and delta‐endotoxin (active protein) concentrations in the two formulations were determined by a gravimetric procedure and by ELISA respectively.

The initial deposit levels of the toxin on foliage were not markedly affected by the addition of either of the two tracer dyes, and showed only a narrow range of 1521 to 1625 ng/g foliage (fresh weight) for Foray 48B, and 1789 to 2056 ng/g for Foray 76B. However, the persistence of the toxin was significantly influenced by the presence of the dyes. The toxin persisted in foliage only for 7 d post‐spray When the EAR dye was added to Foray 48B, compared to 10 d when no dye was added. The average half‐life (DT₅₀) of disappearance was 17.4 h for Foray 48B with EAR, and 20.9 h when no dye was present. In contrast, the situation was reversed in Foray 76B, since the duration of persistence was 10 d when EAR was added to Foray 76B, compared to 7 d when no dye was added. The average DT₅₀ was 27.9 h for Foray 76B with EAR, and 22.2 h without the dye. Persistence was the longest (14 d) when the AB‐48 dye was added to Foray 76B, and the DT₅₀ was 44.9 h.     

The impact of slurry application technique on nitrous oxide emission from agricultural soils

Direct nitrous oxide (N₂O) emissions from fertilized soils are generally estimated using emission factors. However, the emission factors for N₂O emission of applied slurry are not well quantified. The effect of slurry application technique on N₂O emission was quantified in field experiments in the Netherlands in order to derive N₂O emission factors for (shallow) injected and surface-applied cattle and pig slurries. Fluxes of N₂O were measured using a closed flux chamber technique and a photo-acoustic infra-red gasmonitor. Fluxes of N₂O were measured 64–83 times on grassland on sandy and clay soils and maize land on sandy soil, in the period 2007–2009. There were large differences in total N₂O emission between the years, and differences between treatments were not consistent over the years and sites. The average emission factor of all treatments and years (n = 35) was 0.9% of the N applied, which is close to the default IPCC emission factor of 1%. However, the range in emission was large, i.e. from ?0.2% to 7.0%. The average emission factor for grassland was 1.7% of the N applied for calcium ammonium nitrate (CAN), 0.4% for shallow injected cattle slurry, and 0.1% for surface-applied cattle slurry. For maize land, the average emission factor for CAN was 0.1% of the N applied, for injected cattle slurry 0.9% and for surface-applied cattle slurry 0.4%. The emission factors for pig slurry applied to maize land were higher than for cattle slurry; 3.6% for injected pig slurry and 0.9% for surface-applied pig slurry. Increasing the N application rate on maize land resulted in higher emission factors for CAN, injected cattle slurry, and injected pig slurry. Concluding, on both grassland and maize land (shallow) injection of slurry increased the average emission factor of N₂O in comparison to surface application. Differentiation of N₂O emission factors which takes specific factors into account, such as N type and rate and application technique, can improve the quantification of N₂O emission from agricultural soils and is needed to derive most efficient options for mitigation.