Wet peroxide degradation of atrazine

The high temperature (150-200 degrees C), high pressure (3.0-6.0 MPa) degradation of atrazine in aqueous solution has been studied. Under these extreme conditions atrazine steadily hydrolyses in the absence of oxidising agents. Additionally, oxygen partial pressure has been shown not to affect atrazine degradation rates. In no case mineralisation of the parent compound was observed. The addition of the free radical generator hydrogen peroxide to the reaction media significantly enhanced the depletion rate of atrazine. Moreover, partial mineralisation of the organics was observed when hydrogen peroxide was used. Again, oxygen presence did not influence the efficiency of the promoted reaction. Consecutive injections of hydrogen peroxide throughout the reaction period brought the total carbon content conversion to a maximum of 65-70% after 40 min of treatment (suggesting the total conversion of atrazine to cyanuric acid). Toxicity of the effluent measured in a luminometer decreased from 93% up to 23% of inhibition percentage. The process has been simulated by means of a semi-empirical model.     

A reflection on collaborative adaptation research in Africa and Asia

Regional Environmental Change - The reality of global climate change demands novel approaches to science that are reflective of the scales at which changes are likely to occur, and of the new forms...     

Site specific factors have an overriding impact on Baltic dune vegetation change under low to moderate N-deposition—a case study from Hiddensee island

At three coastal dune sites at the island of Hiddensee, north-east Germany, vegetation cover was mapped during 2002 and compared to vegetation surveys from the late 1980s and 1930s. Abiotic and biotic factors, which have been identified as being critical for coastal dunes in former studies such as disturbance, salt spray or nutrient availability, were measured. Grazing and land-use history were reviewed by literature and interviews. Tall graminoid communities, mainly Carex arenaria, are a common vegetation unit today. Development, distribution of these dominances and possible causes for its occurrence have not been analysed. Generally, older successional vegetation units increased and pioneer stages decreased from the 1930s until 2002. At the geologically youngest site, the southern dunes, grass encroachment by Carex arenaria was highest (ca. 50% cover in 2002), and age and density of trees lower than at the older, central dunes. Land-use changes such as decrease in grazing pressure, additional feeding of livestock, increase in coastal protection measures and subsequent decrease in shifting sands as well as varying availability of groundwater and amount of salt spray are relevant factors for vegetation changes in coastal dunes over the past 70 years. Site-specific land-use differences such as livestock density and land-use history have a stronger influence than atmospheric N-pollution on the vegetation composition of these acidic, coastal dunes under low to moderate N-deposition loads of 6–8 kg N ha⁻¹ yr⁻¹.     

Gonopore sexing technique allows determination of sex ratios and helper composition in eusocial shrimps

An evaluation of the social organization and sexual system of eusocial species of Synalpheus has been hindered because it has not been possible to determine the sexual composition of colony helpers (workers). The external sexual characters typically used to sex caridean shrimps are lacking in Synalpheus. We used SEM sexing technique to determine the sexual composition of helpers in colonies of Synalpheus regalis, S. rathbunae, S. chacei, S. rathbunae A (see Morrison et al. Mol Phylogen Evol 30:563–568, 2004), and S. filidigitus. Colonies consisted of both sexes and sex ratios of helpers generally conformed to 50:50 female to male. Females were characterized by gonopores with U-shaped slits on the coxae of the third pereopods (first walking legs) while males had oval gonopore openings on the coxae of the fifth pereopods (third or last walking legs). In S. chacei, S. filidigitus, and S. rathbunae A, a few helpers were found that had both male and female gonopores (intersexes). All three reproductive females (queens) of S. filidigitus examined were intersexes. Sexing of helpers allowed us to test some hypotheses about sexual differences in helper morphology that might indicate task specialization (division of labor). Male helpers were not different from female ones in body size (except in S. regalis: males somewhat larger) and in fighting chela size. The lack of sexual dimorphism in these characters suggests no male–female specialization in colony tasks such as defense. The presence of male and female helpers similar in size suggests that the sexual system of these eusocial species is gonochoristic, although protandry of some sort in S. filidigitus can not be ruled out. The intersexuality observed in a few individuals may be due to developmental anomalies, protandry, or even simultaneous hermaphroditism. Finally, the sexing technique allowed us to establish that new colonizers of unoccupied sponges in S. rathbunae are a single male and female of helper size.     

Passive airborne dust sampling to assess mite antigen exposure in farming environments

The aim of this study was to estimate mite antigen exposure in farming environments by passive sampling of airborne dust. Antigen concentrations were measured with enzyme immunoassays specific for three storage mites (SM): Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae and the house dust mite (HDM) Dermatophagoides pteronyssinus. Dust samples were collected with electrostatic dust fall collectors (EDCs) in three different areas of cattle farms. EDCs were placed in cow stables (working area), in changing rooms (transit area) and in different rooms of farmer dwellings (living area). Mite concentrations in the living area of farm homes were compared to those of urban homes. In dust samples from stables, antigens of all four mite species could be detected. The highest exposure level was to L. destructor (median 56.7 μg/m(2)), the lowest to A. siro (median 14.4 μg/m(2)). Mite concentrations of different species showed no correlation within the cow stables. In comparison to stables, the median mite concentrations in farm homes were significantly lower, ranging from below the detection limit to 1.5 μg/m(2). Antigens of SM were predominantly found in changing rooms and kitchens, and HDM antigens were mainly detected in bedrooms. Antigens of all mites were measured the least often in living rooms. T. putrescentiae was the most prevalent mite in all room types, and the exposure levels correlated strongly between different rooms. The number of SM positive samples in farm homes was considerably higher than in urban homes, while the percentage of HDM positive samples did not differ significantly.     

Linking Hydrogeological and Ecological Tools for an Integrated River Catchment Assessment

Ecological (biological and hydrochemical assessment) and hydrogeological (vulnerability and pollution risk mapping) tools have been combined to assess the ecological quality and hydrogeological vulnerability of an agricultural river basin. In addition, the applicability of the recently developed vulnerability assessment approach (COP method) in the particular environmental conditions was tested by comparing its results with hydroecological assessment tools (i.e., pollution metrics). Five sampling sites were selected and sampled for benthic macroinvertebrates and physicochemical variables during summer and spring. Overall, sites ranged from moderate to poor ecological quality. The results illustrated that 26% of the study area was of moderate pollution risk, while 65% was classified as of low and very low risk zones. However, the higher elevation zones where calcareous rock formations are encountered presented moderate to high pollution risk that was accredited by the ecological quality assessment. Pollution metrics facilitated from hydrochemical analysis indicated a significant association with groundwater vulnerability, thus validating vulnerability and risk estimations. This study indicated that the particular groundwater pollution risk mapping methodology and the water quality assessment indices can be well combined to provide an integrated evaluation tool at a catchment scale.     

The role of environmental and spatial processes in structuring lake communities from bacteria to fish

We assessed the relative roles of local environmental conditions and dispersal on community structure in a landscape of lakes for the major trophic groups. We use taxonomic presence-absence and abundance data for bacteria, phytoplankton, zooplankton, and fish from 18 lakes in southern Quebec, Canada. The question of interest was whether communities composed of organisms with more limited dispersal abilities, because of size and life history (zooplankton and fish) would show a different effect of lake distribution than communities composed of good dispersers (bacteria and phytoplankton). We examine the variation in structure attributable to local environmental (i.e., lake chemical and physical variables) vs. dispersal predictors (i.e., overland and watercourse distances between lakes) using variation partitioning techniques. Overall, we show that less motile species (crustacean zooplankton and fish) are better predicted by spatial factors than by local environmental ones. Furthermore, we show that for zooplankton abundances, both overland and watercourse dispersal pathways are equally strong, though they may select for different components of the community, while for fish, only watercourses are relevant dispersal pathways. These results suggest that crustacean zooplankton and fish are more constrained by dispersal and therefore more likely to operate as a metacommunity than are bacteria and phytoplankton within this studied landscape.