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The isotopic composition of molecular hydrogen (H2) contains independent information for constraining the global H2 budget. To explore this, we have implemented hydrogen sources and sinks, including their stable isotopic composition and isotope fractionation constants, into the global chemistry transport model TM5. For the first time, a global model now includes a simplified but explicit isotope reaction scheme for the photochemical production of H2. We present a comparison of modelled results for the H2 mixing ratio and isotope composition with available measurements on seasonal to inter annual time scales for the years 2001-2007. The base model results agree well with observations for H2 mixing ratios. For σD[H2], modelled values are slightly lower than measurements. A detailed sensitivity study is performed to identify the most important parameters for modelling the isotopic composition of H2. The results show that on the global scale, the discrepancy between model and measurements can be closed by adjusting the default values of the isotope effects in deposition, photochemistry and the stratosphere-troposphere exchange within the known range of uncertainty. However, the available isotope data do not provide sufficient information to uniquely constrain the global isotope budget. Therefore, additional studies focussing on the isotopic composition near the tropopause and on the isotope effects in the photochemistry and deposition are recommended. [ABSTRACT FROM AUTHOR]

Inverse modeling techniques used to quantify surface carbon fluxes commonly assume that the uncertainty of fossil fuel CO2 (FFCO2) emissions is negligible and that intra-annual variations can be neglected. To investigate these assumptions, we analyzed the differences between four fossil fuel emission inventories with spatial and temporal differences over Europe and their impact on the model simulated CO2 concentration. Large temporal flux variations characterize the hourly fields (~40% and ~80% for the seasonal and diurnal cycles, peak-to-peak) and annual country totals differ by 10% on average and up to 40% for some countries (i.e., the Netherlands). These emissions have been prescribed to seven different transport models, resulting in 28 different FFCO2 concentrations fields. The modeled FFCO2 concentration time series at surface sites using time-varying emissions show larger seasonal cycles (+2 ppm at the Hungarian tall tower (HUN)) and smaller diurnal cycles in summer (-1 ppm at HUN) than when using constant emissions. The concentration range spanned by all simulations varies between stations, and is generally larger in winter (up to ~10 ppm peak-to-peak at HUN) than in summer (~5 ppm). The contribution of transport model differences to the simulated concentration std-dev is 2-3 times larger than the contribution of emission differences only, at typical European sites used in global inversions. These contributions to the hourly (monthly) std-dev's amount to ~1.2 (0.8) ppm and ~0.4 (0.3) ppm for transport and emissions, respectively. First comparisons of the modeled concentrations with 14C-based fossil fuel CO2 observations show that the large transport differences still hamper a quantitative evaluation/validation of the emission inventories. Changes in the estimated monthly biosphere flux (Fbio) over Europe, using two inverse modeling approaches, are relatively small (less that 5 %) while changes in annual Fbio (up to ~0.15%GtC yr-1) are only slightly smaller than the differences in annual emission totals and around 30% of the mean European ecosystem carbon sink. These results point to an urgent need to improve not only the transport models but also the assumed spatial and temporal distribution of fossil fuel emission inventories. [ABSTRACT FROM AUTHOR]

Despite the potential of isotope measurements to improve our understanding of the global atmospheric molecular hydrogen (H2) cycle, few H2 isotope data have been published so far. Now, within the EUROpean network for atmospheric HYDRogen Observations and Studies project (EUROHYDROS), weekly to monthly air samples from six locations in a global sampling network have been analysed for hydrogen mixing ratio (m(H2)) and the stable hydrogen isotopic composition of H2 (δ(D,H2), hereafter referred to as δ(D)). The time series thus obtained now cover one to five years for all stations. This is the largest set of ground station observations of δ(D) so far. Annual average δ(D) values are higher at the Southern Hemisphere (SH) than at the Northern Hemisphere (NH) stations; the maximum is observed at Neumayer (Antarctica), and the minimum at the NH midlatitude or subtropical stations. The maximum seasonal differences in δ(D) range from ≈18‰ at Neumayer to ≈45‰ at Schauinsland (Southern Germany); in general, seasonal variability is largest at the NH stations. The timing of minima and maxima differs per station as well. In Alert (Arctic Canada), the variations in δ(D) and m(H2) can be approximated as simple harmonic functions with a ≈5-month phase shift. This out-of-phase seasonal behaviour of δ(D) and m(H2) can also be detected, but with a ≈6-month phase shift, at Mace Head and Cape Verde. However, no seasonal δ(D) cycle could be observed at Schauinsland, which likely reflects the larger influence of local sources and sinks at this continental station. At the two SH stations, no seasonal cycle could be detected in the δ(D) data. Assuming that the sink processes are the main drivers of the observed seasonality in m(H2) and δ(D) on the NH, the relative seasonal variations can be used to estimate the relative sink strength of the two major sinks, deposition to soils and atmospheric oxidation by the hydroxyl (OH) radical. For the NH coastal and marine stations this analysis shows that the relative contribution of soil uptake to the total sink processes increases with latitude. [ABSTRACT FROM AUTHOR]

The use of exfoliative cytology as a bio-assessment tool was evaluated to (1) identify and describe different cell types of normal liver cytology of Oreochromis mossambicus, (2) identify and describe changes in the cell types after exposure to cadmium and zinc, and (3) determine if non-imaging-guided fine-needle aspiration (FNA) cytology can be performed without sacrificing the fish. All fish used in the aspiration experiment recovered and survived. Livers of O. mossambicus exposed to cadmium and zinc showed excess numbers of exfoliated red blood cells, loss of cellular cohesion, regenerative hyperplasia, pale and weak cytoplasm staining, pronounced vacuolation and degeneration. Cadmium and zinc exposure induced pathological cellular changes. Exfoliative cytology is thus a safe, cost-effective and reliable bio-assessment tool. [ABSTRACT FROM AUTHOR]

A semi-quantitative histological assessment was used to investigate histological changes in the gills of Clarias gariepinus from Marais Dam and Rietvlei Dam near Pretoria, which receive effluent from sewage treatment plants and industries, as well as runoff from informal settlements. Results were compared to those from a laboratory-bred reference group of fish. Histological alterations were prevalent in fish from both impoundments, including circulatory disturbances such as telangiectasia and epithelial lifting, hyperplasia of mucous cells and epithelial cells between secondary lamellae, structural alterations in the form of fusion and branching of primary and secondary lamellae, and regressive changes in the form of intracellular alterations within gill epithelial cells. Significantly higher histological index values were calculated for fish from Marais Dam compared to those from Rietvlei Dam. [ABSTRACT FROM AUTHOR]

The aims of this study were to determine relative age, growth rate and size at maturity of tigerfish in the Okavango Delta as a basis for the development of a fisheries management plan. A total of 206 tigerfish Hydrocynus vittatus, collected by angling in August 2005, 2006 and 2007, was assessed for sexual maturity and relative ages were estimated from 135 of these, using scales and whole and sectioned otoliths. Sectioned otoliths were the most appropriate method for ageing H. vittatus of up to 20 years old. Males were present in all relative age classes, proving that they do not disappear from the population at a young age, as previously thought. Males matured at 451 mm TL and females at 522 mm TL, corresponding to an approximate relative age of four years for both sexes. Males lived for up to 20 years, females for up to 16 years. [ABSTRACT FROM AUTHOR]

This article discusses research that evaluated the amount of histopathological alterations in the liver of the sharptooth catfish (Clarias gariepinus) sampled from two dams in an urban nature reserve located in Gauteng, South Africa. Such research is pertinent, as biomonitoring tools in ecological toxicology assessment are needed to show the effect of pollutants on fish health in aquatic ecosystems. Water and sediment samples were taken to test for metal pollution and the existence of endocrine disrupting chemicals.

Inverse modeling techniques used to quantify surface carbon fluxes commonly assume that the uncertainty of fossil fuel CO2 (FFCO2) emissions is negligible and that intraannual variations can be neglected. To investigate these assumptions, we analyzed the differences between four fossil fuel emission maps with spatial and temporal differences over Europe and their impact on the model simulated CO2 concentration. Large temporal flux variations characterize the hourly fields (∼40% and ∼80% for the seasonal and diurnal cycles, peak-to-peak) and annual country totals differ by 10% on average and up to 40% for some countries (i.e., The Netherlands). These emissions have been prescribed to seven different transport models, resulting in 28 different FFCO2 concentrations fields. The modeled FFCO2 concentration time series at surface sites using time-varying emissions show larger seasonal cycles (+2 ppm at the Hungarian tall tower (HUN)) and smaller diurnal cycles in summer (-1 ppm at HUN) than when using constant emissions. The concentration range spanned by all simulations varies between stations, and is generally larger in winter (up to ∼10 ppm peak-to-peak at HUN) than in summer (∼5 ppm). The contribution of transport model differences to the simulated concentration std-dev is 2-3 times larger than the contribution of emission differences only, at typical European sites used in global inversions. These contributions to the hourly (monthly) std-dev's amount to ∼1.2 (0.8) ppm and ∼0.4 (0.3) ppm for transport and emissions, respectively. First comparisons of the modeled concentrations with 14C-based fossil fuel CO2 observations show that the large transport differences still hamper a quantitative evaluation/validation of the emission inventories. Changes in the estimated monthly biosphere flux (Fbio) over Europe, using two inverse modeling approaches, are relatively small (less that 5%) while changes in annual Fbio (up to ∼0.15 Gt C/yr) are only slightly smaller than the differences in annual emission totals and around 30% of the mean European ecosystem carbon sink. These results point to an urgent need to improve not only the transport models but also the assumed spatial and temporal distribution of fossil fuel emission maps. [ABSTRACT FROM AUTHOR]

The effects of DDT and its metabolites on the reproductive health of two fish species ( Clarias gariepinus and Oreochromis mossambicus) were studied using the gonadosomatic index (GSI), gonadal histology and computer assisted sperm analysis (CASA). DDT and its metabolites, DDE and DDD are endocrine disrupting chemicals posing estrogenic and anti-androgenic properties, which have detrimental effects on growth and reproduction. Although DDT was banned internationally, it is still used for Malaria vector control in areas of South Africa. Both species were sampled at a reference site, Albasini dam (AD), (outside the DDT-sprayed area, <0.01 μg L−1 of DDT) and at an exposed site, Xikundu weir (XW), in the same river ± 70 km within the DDT-sprayed area, <0.01 μg L−1 of DDT. Gill nets were used to acquire a sample size of 10 male fish per site for each species. Both testes were dissected out and the GSI calculated. Uncontaminated milt was collected and analyzed using a novel CASA system based on open source software for characterization of sperm motility parameters. Testis tissue sampled for histology was fixed in Bouins and processed according to standard methods. The sample size obtained at the reference site (AD) was O. mossambicus n = 6, C. gariepinus n = 9; and at the exposed site (XW) was O. mossambicus n = 10, C. gariepinus n = 3. The GSI results showed a lower value for O. mossambicus at XW (0.06) (n = 13) than AD (0.12) (n = 6); U = 16.0, P = 0.044. However the opposite was true for C. gariepinus. Exposure to various environmental toxicants can result in gonadal changes such as decreased GSI, morphological alterations or both. Histological assessment showed histopathological alterations to testes tissue including intersex (only in O. mossambicus) and detachment of basal membranes. The CASA results showed a decrease in parameters from the reference site (AD) to the exposed site (XW) for both species. The decrease in percent motility (% MOT) for O. mossambicus from the reference site (AD) (n = 6) to the exposed site (XW) (n = 13) was statistically significant; U = 13.0, P = 0.023. C. gariepinus from the exposed site (XW) was most affected in terms of percent motility (10.00%) and velocity (67.94 μm s−1). Detailed assessment of the environmental effects of DDT in this area seems crucial before population impacts become evident. [ABSTRACT FROM AUTHOR]

In this work, the performance of the Framework for Atmosphere-Canopy Exchange Modelling (FACEM: Pieterse et al., 2007) coupled to a Lagrangian atmospheric transport model is evaluated for carbon dioxide. Before incorporating FACEM into the Lagrangian COMET model (Vermeulen et al., 2006), its performance for the European domain is compared with the Simple Biosphere model (SiB3: Sellers et al., 1996). Overall, FACEM is well correlated to SiB3 (R²≥.60), but shows less variability for regions with predominantly bare soil. There is no significant overall bias between the models except for the winter conditions and in general for the Iberian peninsula. When coupled to the COMET transport model, both biosphere models yield similar correlations (R²≥0.60) and bias relative to the 1-hourly concentration measurements for the year 2002, performed at three different sites in Europe; Cabauw (Netherlands), Hegyhatsal (Hungary) and Mace Head (Ireland). The overall results indicate that FACEM is comparable to SiB3 in terms of its applicability for atmospheric modelling studies. [ABSTRACT FROM AUTHOR]

The reactivity of aromatic compounds is of great relevance to pure and applied chemical disciplines, yet existing methods for estimating gas-phase rate coefficients for their reactions with free radicals lack accuracy and universality. Here a novel approach is taken, whereby strong relationships between rate coefficients of aromatic hydrocarbons and a Randić-type topological index are investigated, optimized and developed into a method which requires no specialist software or computing power. Measured gas-phase rate coefficients for the reaction of aromatic hydrocarbons with OH radicals were correlated with a calculated Randić-type index, and optimized by including a term for side chain length. Although this method is exclusively for use with hydrocarbons, it is more diverse than any single existing methodology since it incorporates alkenylbenzenes into correlations, and can be extended towards other radical species such as O(3P) (and tentatively NO3, H and Cl). A comparison (with species common to both techniques) is made between the topological approach advocated here and a popular approach based on electrophilic subsituent constants, where it compares favourably. A modelling study was carried out to assess the impact of using estimated rate coefficients as opposed to measured data in an atmospheric model. The difference in model output was negligible for a range of NOx concentrations, which implies that this method has utility in complex chemical models. Strong relationships (e.g. for OH, R2=0.96) between seemingly diverse compounds including benzene, multisubstituted benzenes with saturated, unsaturated, aliphatic and cyclic substitutions and the nonbenzenoid aromatic, azulene suggests that the Randić-type index presented here represents a new and effective way of describing aromatic reactivity, based on a quantitative structure-activity relationship (QSAR). [ABSTRACT FROM AUTHOR]

A qualitative and quantitative histological assessment was done on the liver, gills and gonads. Focus was placed on reproductive health aspects by staging the gonads according to their reproductive development and assessing the motility of activated sperm using Computer Assisted Sperm Analysis. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the type and severity of histological alterations in selected target organs of Clarias gariepinus and Cyprinus carpio. The results of this study indicate that there are macroscopic and histological alterations in the target organs of both the selected species from the Hartebeespoort Dam. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine if liver tissue obtained through means of core biopsy and FNA was as adequate for analysis as tissue samples obtained through terminal sampling. Clarias gariepinus was the test organism. The objectives were fulfilled as the study was successful. [ABSTRACT FROM AUTHOR]

Cryopreservation of antelope epididymal spermatozoa could play a vital role in future breeding by developing a successful protocol for cryo-conserving them. The aim of this study was to characterize morphology, motility rates and longevity of epididymal spermatozoa from springbok, impala and blesbok. Cauda epididymal spermatozoa were collected post-mortem from both testicles of free-ranging springbok (n=18), impala (n=21) and blesbok (n=21), and divided into two groups (pre- and post-cryopreservation). Spermatozoa were cryopreserved in Biladyl supplemented with 20% egg yolk and 7% glycerol under field conditions. Pre-freeze and post-thaw sperm quality was evaluated. The longevity of thawed spermatozoa was evaluated under culture conditions that support domestic cattle in vitro fertilization. There was a significant difference between pre-freeze and post-thaw sperm motility index (SMI) (p<0.05), plasma membrane integrity (p<0.05) and acrosome integrity (p<0.05) for all species. Post-thaw SMI and plasma membrane integrity were comparable between species (p>0.05). The effects of cryopreservation on sperm cell morphology differed between species and between specific abnormal morphology. Blesbok had the least abnormalities in post-thaw spermatozoa. Cryopreservation substantially reduced the survivability and motility rates of antelope species. Blesbok spermatozoa tolerated cryopreservation and thawing process better than impala and springbok. The antelope cauda epididymal sperm maintained viability and acrosome integrity for at least 4h following incubation under conditions that support domestic cattle in vitro fertilization (IVF) with a decline in longevity over time across species however; species responded differently over time in terms of plasma membrane integrity and acrosome integrity. The antelope species may have different in vitro culture requirements, indicating differences in sperm physiology between the species. This research could contribute species-specific protocol development for IVF thus promoting ex-situ conservation strategies of African antelope species in South Africa., (Copyright © 2011 Elsevier B.V. All rights reserved.)

This study reports on intersex in Oreochromis mossambicus, an indigenous fish species inhabiting most aquatic systems throughout South Africa (SA). Male fish were collected from three sites in the Luvuvhu River, Limpopo Province, SA: Albasini Dam (AD), Nandoni Dam (ND), and Xikundu Weir (XW). The latter two sites are situated in a currently dichloro-diphenyl-trichloroethane (DDT) sprayed area. A laboratory-bred reference group (Aq R) were included for a histological comparison. 48% of the fish at AD were intersex individuals compared with 63% at ND, and 58% at XW. The Aq R fish had no cases of intersex. o,p'- and p,p'-DDT and metabolites dichlorodiphenyldichloroethane (DDD) and -dichlorodiphenyldichloroethylene (DDE) were detected in fat samples, indicative of contamination of the aquatic environment and subsequent exposure of fish to these chemicals. Although some of the fat samples contained levels of DDTs no association could be established between intersex and chemical contaminants in fish., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The toxic effects, of two heavy metals, cadmium (Cd) and zinc (Zn), on the histology of the liver of the southern African freshwater fish Oreochromis mossambicus, were investigated. The goal was to identify whether metal concentrations and exposure period influence the degree and nature of histological changes in the liver of exposed fish. Selected fish were exposed to a mixture of 5% concentrations of the LC(50) of cadmium and zinc and to a mixture of 10% concentrations of the LC(50) of cadmium and zinc, over both short- and long-term exposure periods. Similar histological changes occurred in the livers of specimens exposed to both 5% and 10% concentrations, indicating a definite toxic response to both the metal concentrations. These histological changes included hyalinization, hepatocyte vacuolation, cellular swelling, and congestion of blood vessels. The intensity of these histological changes was, however, influenced by the extent of the exposure period.