Leaching of glyphosate and amino-methylphosphonic acid from Danish agricultural field sites

Pesticide leaching is an important process with respect to contamination risk to the aquatic environment. The risk of leaching was thus evaluated for glyphosate (N-phosphonomethyl-glycine) and its degradation product AMPA (amino-methylphosphonic acid) under field conditions at one sandy and two loamy sites. Over a 2-yr period, tile-drainage water, ground water, and soil water were sampled and analyzed for pesticides. At a sandy site, the strong soil sorption capacity and lack of macropores seemed to prevent leaching of both glyphosate and AMPA. At one loamy site, which received low precipitation with little intensity, the residence time within the root zone seemed sufficient to prevent leaching of glyphosate, probably due to degradation and sorption. Minor leaching of AMPA was observed at this site, although the concentration was generally low, being on the order of 0.05 microg L(-1) or less. At another loamy site, however, glyphosate and AMPA leached from the root zone into the tile drains (1 m below ground surface [BGS]) in average concentrations exceeding 0.1 microg L(-1), which is the EU threshold value for drinking water. The leaching of glyphosate was mainly governed by pronounced macropore flow occurring within the first months after application. AMPA was frequently detected more than 1.5 yr after application, thus indicating a minor release and limited degradation capacity within the soil. Leaching has so far been confined to the depth of the tile drains, and the pesticides have rarely been detected in monitoring screens located at lower depths. This study suggests that as both glyphosate and AMPA can leach through structured soils, they thereby pose a potential risk to the aquatic environment.     

Molecular genetic evidence for probable reticulate speciation in the coral genus Madracis from a Caribbean fringing reef slope

For many corals, the existence of morphologically distinct yet sympatric populations/species implies reproductive isolation. Conversely, the presence of many intermediate and overlapping morphologies combined with synchronous, mass spawning suggests incomplete reproductive isolation. In Madracis (Scleractinia: Astrocoeniina: Pocilloporidae), high levels of morphological plasticity among the five most commonly recognized species (M. mirabilis, M. senaria, M. decactis, M. formosa and M. pharensis) on Caribbean reefs led us to question species boundaries. Phylogenetic relationships were investigated at the intra-individual, inter-individual and inter-specific levels using the ITS1-5.8S-ITS2 region (ca. 613 bp) of the ribosomal DNA cistron. Inter-specific divergence was ca. 6%, while intra-individual and intra-specific divergences ranged from 0% to 4.9% and 3.3% to 3.5%, respectively. M. senaria and M. mirabilis formed monophyletic groups. M. formosa, M. decactis and M. pharensis formed a paraphyletic complex. High levels of intra-individual and intra-specific ITS polymorphism in the decactis-formosa-pharensis cluster may be the result of very recent speciation within the clade (i.e. maintenance of ancestral polymorphism and incomplete lineage sorting), or the result of repeated introgressive hybridization among the three taxa. Polymorphism parsimony of 89 sites, including nine that showed additivity, revealed a phylogenetic topology more consistent with inter-taxal hybridization. Results are discussed in terms of weak reproductive barriers, and phylogenetic fission and fusion under Veron's model of reticulate speciation in corals. Ecological studies involving Madracis should consider M. decactis, M. formosa and M. pharensis as a complex.     

A model for the bioaccumulation of (99)Tc in lobsters (Homarus gammarus) from the West Cumbrian coast

A biokinetic model is presented that simulates the uptake and release of (99)Tc by the European lobster (Homarus gammarus). This organism is of significant radioecological interest since lobsters, in contrast to most other organisms, have a high affinity for (99)Tc. The model is designed to represent annually averaged (99)Tc concentrations in lobsters from the Cumbrian coast, where significant levels of (99)Tc have been released under authorisation by the nuclear fuel reprocessing plant at BNFL Sellafield.This paper describes the construction of the model, how it was calibrated using data from published literature, and preliminary results indicating that model output agrees well with the available monitoring data. Given that this model successfully combines laboratory and field data, this research could potentially make a significant contribution to the field, as, to date, it has been difficult to predict and explain concentrations of (99)Tc in lobsters.     

A constant pressure dust explosion experiment

A new apparatus has been designed for investigating flame propagation in turbulent dust clouds at near constant pressure conditions. The experimental approach is inspired by the classical soap bubble method for measuring burning velocities in gaseous mixtures. Combustible dust is dispersed with pressurised air to form an explosive mixture inside a transparent latex balloon. After a certain delay time, the turbulent dust cloud is ignited by a 40 J chemical igniter. A digital high-speed video camera records the propagating flame and the expansion of the balloon. Experiments were performed with two types of dust, Lycopódium spores and maize starch, as well as with propane–air mixtures under initially quiescent or turbulent conditions. Although the results are primarily qualitative in nature, they nevertheless demonstrate fundamental differences between premixed combustion of gaseous mixtures, and ‘premixed combustion with non-premixed substructures' in mechanical suspensions of solid particles dispersed in air. The discussion highlights some fundamental challenges for future dust explosion research.