New PEC definitions for river basins applicable to GIS-based environmental exposure assessment

By means of GREAT-ER (Geo-Referenced Regional Exposure Assessment Tool for European Rivers) aquatic chemical fate simulations can be performed for river basins. To apply the resulting digital maps with local (river stretch specific) predicted concentrations in regional aquatic exposure and risk assessment, the output has to be aggregated to a (single) value representative of exposure in the catchment. Two spatially aggregated PEC definitions are proposed for this purpose: PECinitial (unweighted aggregation of concentrations just downstream of wastewater emissions) and PECcatchment (weighted aggregation of all average stretch concentrations). These PECs were tested using simulations for two pilot study catchments (Calder and Went, UK). This confirmed the theoretical considerations which led to the definitions, and it illustrated the need for weighting to resolve scale-dependencies.     

Sensory brain areas in three families of deep-sea fish (slickheads, eels and grenadiers): comparison of mesopelagic and demersal species

The sensory brain areas of a sample of <100 deep-sea fish species were studied, and the relative volumes of the olfactory bulb, optic tectum, octavolateral area and gustatory area were determined. In the absence of direct observations on the behaviour of this ichthyofauna these data allow deductions to be made about the kinds of sensory modalities used preferentially in the deep-sea environment. Here, members of three families are compared that have representatives living on or near the sea floor (“demersal”) and in the open water between 200 and 1.000 m (mesopelagic). The findings indicate that both regions present fish with rich and diverse sensory environments. While vision emerges as the dominant sense of the mesopelagic realm, olfaction seems more important on or near the bottom of the sea. However, other sensory modalities supplement these senses in species-specific patterns. Considerations of the phyletic relationships indicate different degrees of pervasiveness. Whilst in slickheads the dominance of vision appears to be a family-related trait, a similar relationship is not found in either eels or grenadiers. By contrast, the common trait in these two families seems to be the greater adaptability to the environment. Published online: 21 August 2002     

Variations in circulating hemocytes are affected by age and caste in the stingless bee <Emphasis Type="Italic">Melipona quadrifasciata</Emphasis>

The insect immune system faces various challenges; particularly in social bees, caste system and age polyethism expose individuals to numerous environmental and working conditions. However, little is known about how cellular defenses in social bees may be organized to respond to a variety of immune challenges. Here, we describe the morphological features and the total and differential counts of hemocytes in different female classes (newly emerged workers, nurses, foragers, and virgin queens) of the eusocial stingless bee Melipona quadrifasciata. Granulocytes and prohemocytes were, respectively, the most and the least abundant cells among all classes of females. Furthermore, there were more prohemocytes in virgin queens than in foragers. The total number of hemocytes was smaller in foragers, whereas the largest number was observed in nurse workers. This reduced amount of hemocytes in foragers might allow energy savings to perform colony activities such as foraging and defense. Foragers also had the biggest hemocytes (either prohemocytes, granulocytes, or plasmatocytes) in comparison to the other classes of females, which might have arisen as a compensation for the reduction in number of these cells during aging. These results suggest that profiles of hemocytes of M. quadrifasciata vary according to the caste and age of this eusocial bee.     

Guidelines for selection and application of fate and exposure models

Guidelines for selection and application of fate and exposure models were developed as an instrument for the user to detect the most appropriate model for his/her special problem. Criteria for evaluating the quality and performance of implemented computer programmes and the underlying theory were defined. A model data bank for exposure models was developed which involves selection and quality characteristics; it was tested with ten randomly selected exposure models.     

Methane Emissions from Landfills and Carbon Dynamics of Harvested Wood Products: The First-Order Decay Revisited

The First-Order decay method for carbon stocks is derived from first principles, and applications in the context of national greenhouse gas inventories are discussed. For methane emissions from landfills a method is developed that in principle is more accurate than the method currently recommended by the IPCC, and systematic errors are estimated numerically. The First-Order decay method is further applied to derive the permanent part of the carbon pool of harvested wood products.