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Abstract  

Thermal and epithermal neutron activation analysis techniques were used to analyze 27 Teflon air filters which were exposed to ambient air in Lisbon, Portugal, in February 2007. Tin was detected which is strongly suggestive of an anthropogenic source. Arsenic, antimony and copper were shown to be highly correlated, which is also suggestive of anthropogenic pollution. Trace element analysis of short- and medium-lived isotopes was performed yielding concentration information of various elements. Analytical sensitivities were enhanced using a Compton suppression system. Enrichment factor analysis shows that arsenic, tin, zinc, copper and antimony are at elevated concentrations in the Lisbon atmosphere.

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Fusarium head blight (FHB) is a disease of small-grain cereals that has a proven negative impact on crop yield, quality and food safety. In this regard, it is one of the most studied diseases of small-grain cereals worldwide. This paper reports the commonly used artificial sources of inoculum and inoculation techniques employed in the study of FHB epidemiology. Spore suspensions and grain spawn are the most popular forms of artificial inoculums. Spray inoculation technique is more commonly used than the point inoculation technique for delivering the inocula to the target sites. Spray inoculation has an advantage over point inoculation in that it can be used to detect both Type I and II resistances to FHB, point inoculation can only detect Type II resistance to FHB. Grain spawn is the commonest soil-surface inoculum used in the study of FHB. Its advantage lies in the fact that it is capable of propagating inoculum over a long period of time compared to other methods. It can also detect the five types of resistances reported (Types I, II, III, IV and V). In order to gain further information regarding the epidemiology of FHB, researchers need to explore other potential sources of artificial inoculum.

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The effect of different timings of fungicide applications on Fusarium head blight severity and mycotoxin accumulation in wheat grain was investigated in two field experiments. The fungicides metconazole, tebuconazole, azoxystrobin and mixtures of metconazole + azoxystrobin and tebuconazole + azoxystrobin were applied either, 5 days pre-, 2 days pre-, 2 days post-or 5 days post-inoculation of wheat ears with Fusarium spp. and Microdochium spp. at GS 65. Fungicides applied 2 days pre-or 2 days post-inoculation were most effective at reducing Fusarium head blight severity and DON concentration in grain. Metconazole and tebuconazole applied alone within two days of inoculation were most consistent in their effects on Tri5 DNA and DON in harvested grain.

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Saprophytic microflora and non-toxin producing Microdochium spp. capable of causing Fusarium head blight (FHB) have been suggested to affect the development of FHB caused by Fusarium spp., the occurrence of mycotoxins and the efficacy of fungicides for the control of the disease. The effects of metconazole and azoxystrobin on the interactions between Fusarium culmorum and Microdochium spp., Alternaria tenuissima or Cladosporium herbarum on FHB symptom development, Tri5 DNA concentration and deoxynivalenol (DON) production were studied under glasshouse conditions. Results indicated that the sequence of infection of wheat heads and the relative timing of fungicide application can significantly affect FHB severity and the resulting mycotoxin contamination of harvested grain. Introduction of A. tenuissima, C. herbarum or Microdochium spp. to wheat heads at GS 57 before inoculation with F. culmorum at GS 65 generally resulted in increased FHB severity, Tri5 DNA and DON concentration in harvested grain. The greatest increases of FHB severity (266%), Tri5 DNA (79%) and DON (152%) were observed when Microdochium spp. were introduced first at GS 57 and F. culmorum inoculation followed at GS 65. Metconazole generally reduced FHB severity, Tri5 DNA and DON concentration in grain but azoxystrobin was most efficient at reducing DNA of Microdochium spp. in grain.

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Fusarium langsethiae, a toxigenic fungus known to contaminate small-grain cereals with type A trichothecene mycotoxins, HT-2 and T-2 was described as a new species in 2004. HT-2 and T-2 are some of the most potent Fusarium toxins in eukaryotes, capable of inhibiting protein synthesis. The epidemiology of F. langsethiae is not well understood and with the intent of the European Commission to set maximum levels of contamination of cereals with these toxins, importance is currently placed in trying to understand the fungal infection process and its favorable growth conditions. A field study was carried out to investigate the effect of artificially inoculated oats straw, ploughing and minimum tillage with and without incorporated crop debris (straw) on infection and mycotoxin production by F. langsethiae on oats cultivar Gerald. The results indicated that cultural field practices had effects on the infection of oats by F. langsethiae. Fusarium langsethiae DNA was quantified in significantly larger amounts (p<0.05) in minimum tilled with incorporated straw plot samples than in other plot samples. It was also shown that inoculated straw had no significant effect (p>0.05) on oat infection by F. langsethiae as quantified by DNA concentration. HT-2+T-2 quantification and analysis, gave no good evidence that either inoculation or cultural practice had any significant influence on the concentration of mycotoxins in the samples (p>0.05), but samples from minimum tillage with incorporated straw plots resulted in 2.5 times more HT-2+T-2 toxins than samples from ploughed with removed straw. These findings indicate the importance of tillage and crop debris management in the mitigation in an effort to prevent F. langsethiae infection, colonization and possible contamination of oats with HT-2 and T-2 toxins.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Goheen, B. McVeety, T. Clauss, R. Lucke, M. Ligotke, J. Edwards, and J. Fruchter

Abstract  

Organic species from the headspace of one Hanford radioactive waste tank are described. Samples were collected either using a sorbent trap or a SUMMATM canister and were analyzed by gas chromatograph and mass spectrometry. The headspace contained several organic components, including alkanes, alkenes, ketones, aldehydes, organic nitriles, and chlorinated hydrocarbons. Sorbent trap samples were designed to collect only normal paraffin hydrocarbons (NPHs). A comparison of NPH data from sorbent traps and SUMMATM cans revealed results of 693 and 1320 mg/m3, NPH respectively. Significant differences were observed in NPH values when samples were collected at different times, or at different locations in the tank. These data suggest either the time of collection, or the position of the sampling device are important variables in the analysis of organic species from Hanford tanks.

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Fusarium langsethiae is a fungus that has recently been implicated in the contamination of small-grain cereal crops such as oats, wheat and barley with high levels of HT-2 and T-2 toxins in many European countries. The epidemiology of this fungus is not well known and may therefore be a bigger problem than currently thought to be. A study was carried out investigating the in vitro growth characteristics of F. langsethiae isolates from contaminated oats and wheat at various temperatures; 15, 20, 25 and 30 °C. Results indicated similar growth trends of oats and wheat isolates of F. langsethiae. Wheat isolates grew significantly (p<0.001) faster than oat isolates although this difference may have been confounded by the age of cultures, with oat isolates collected one year earlier. The estimated optimum growth temperature for all isolates was 24 °C. Isolates were macro-morphologically categorized as having lobed or entire colony margins, and either possessing one of the following colony colours: white, orange or purple. Since the estimated optimum growth temperature of F. langsethiae is typical in temperate summers when small-grain cereals are flowering, it is possible that this species can infect, colonise and possibly contaminate the developing grains with HT-2 and T-2 toxins which are of food safety concern.

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