As part of a larger occupational exposure study in which the concentrations of 18 elements were measured in head hair and toenail collected from steel plant workers, a number of factors associated with interpreting the data obtained were examined. In this paper, some of the limitations and complications associated with hair and nail analysis that were thereby recognised are discussed. Data obtained from the occupational study demonstrated the potential for misinterpreting hair or nail analysis data either through describing results averaged over a group by arithmetic instead of geometric means or through not accounting for the age range of subjects in groups to be compared. Examples that arose from the study indicated that differences between hair from the same subjects grown at different times can both complicate and assist in interpreting hair analysis results. In an investigation into the addition and removal of metallic powders, it was found that both hair and nail can directly incorporate elements through contact with dust.
The behaviour of iodine in the environment is of interest both in relation to radioecology and human nutrition. Radiochemical techniques were used to evaluate various aspects of the behaviour of iodine in the environment. The natural iodine content of plant, water and soil samples collected from three sites was determined using preconcentration neutron activation analysis (PNAA). The effect of initial chemical speciation on the distribution of iodine between various soils, sediments and waters was evaluated using I-131 tracer. Iodide was found to adsorb more extensively than iodate, although for most of the solid/water systems examined, a substantial portion of the iodate was slowly reduced to iodide. Experiments involving gamma irradiation suggest that much of the sorption of iodide and reduction of iodate involved microbial processes. Distribution coefficients measured using I-131 were comparable with values based on the natural I-127 content.
Radiochemical methods are quite suitable for studying the behaviour of radioiodine under the dilute conditions relevant to nuclear reactor accidents. Species selective adsorbents are able to distinguish between various inorganic and organic gas-phase iodine species. A solvent extraction procedure for determining aqueous phase organic iodide, free iodine, I– and IO
fractions has been investigated and found to be valuable, although large inaccuracies in the separation of I– and IO
can occur for solutions of pH above 10. The extraction of potentially-volatile species in the aqueous phase gives a measure of iodine species volatility consistent with observed values of the partition coefficient. Indirect measurement suggest that the partition coefficient of HOI at room temperature exceeds 30,000.
The effect of organic compounds on the production of volatile species of iodine was examined. The first step has been to identify candidates for detailed study through a series of scoping experiments, in which the chemical environment existing in CANDU reactor containment is simulated. These experiments have involved the irradiation of 10–5M CsI solutions labelled with131I containing a dilute concentration of a particular organic compound (8.5·10–3 to 1.4·10–1M). A total of 20 compounds and polymers have been tested to date. Results have shown that many of these compounds do enhance iodine volatility, and that the degree of volatility is related to system pH. Using the iodine partition coefficient (H=iodine concentration in the liquid phase/iodine concentration in the gas phase) as a basis, values as low as 300 have been observed for chloroform solutions. Conversely some compounds, such as phenol, have produced low volatility, with values of 1·105. As a reference, a partition coefficient of 104 has often been used in safety analysis.
A method for quench correction of samples with double radioactive labelling is described. Each nuclide makes a contribution
to the counting rate of three channels of a liquid scintillation counter. This channel overlap is an essential requirement
of the calibration procedure rather than a limitation, and allows more freedom in the choice of counting conditions. After
calibration with suitable standards the method will tolerate wide variations in the ratio of one isotope to the other extending
to single label samples of either isotope. This is the outstanding advantage over the channel ratio method which requires
a statistically significant counting rate for the higher energy isotope. The method takes advantage of the facilities offered
by a computer which may be on line or remote.14C and tritium are used to demonstrate the utility of the method.
The family Encyrtidae is one of the largest families among the Chalcidoidea with over 3000 nominal species known throughout the world of which thirty-eight have been recorded in Egypt (Abd-Rabou, 2006). It represents the largest group of natural enemies of soft scales (Coccidae: Hemiptera) with several hundred species in 45 genera. Prinsloo (1997) provided an excellent review and key to the genera of encyrtids associated with soft scale insects. The following represents the results of a survey of encyrtid parasitoids associated with scale insects in Egypt (Hemiptera: Cocciodea) conducted in 2009.
Species of the family Aphelinidae (Hymenoptera: Chalcidoidea) comprise many of the most widely used and successful entomophagous biological control agents. An annotated list of the 11 genera and 81 species of the family Aphelinidae known to occur in Egypt and a key to genera of Aphelinidae in Egypt are provided.
During an investigation of the whitefly fauna in Egypt, Pealius mori (Takahashi) was discovered infesting Euphorbia sp. in Giza, Egypt. This is the first record of the presence of this whitefly species in Egypt and on this host plant. The taxonomy, distribution, host plants, parasitoids as well as comments regarding this whitefly species are presented.
In recent years, Aleuroclava psidii (Singh) (Hemiptera: Aleyrodidae) has been extending its geographic range due to the international movement of plant material. In October 2013, it was discovered on Psidium sp. (Myrtaceae) in Egypt and represents the first record of this species in Egypt and the Western Palearctic region.