Search

The hydrological budget of the Caspian Sea (CS) is investigated using the European Centre for Medium-Range Weather Forecasts interim reanalysis (ERAi) and seasonal forecast (FCST) data with the aim of predicting the Caspian Sea Level (CSL) some months ahead. Precipitation and evaporation are used. After precipitation events over the Volga River, the discharge (Volga River discharge (VRD)) follows with delays, which are parameterized. The components of the water budget from ERAi and FCSTs are integrated to obtain time series of the CSL. Observations of the CSL and the VRD are used for comparison and tuning. The quality of ERAi data is sufficiently good to calculate the time variability of the CSL with a satisfactory accuracy. Already the storage of water within the Volga Basin allows forecasts of the CSL a few months ahead, and using the FCSTs of precipitation improves the CSL forecasts. The evaporation in the seasonal forecasts is deficient due to unrealistic sea surface temperatures over the CS. Impacts of different water budget terms on the CSL variability are shown by a variety of validation tools. The importance of precipitation anomalies over the catchment of the Volga River is confirmed, but also impacts from the two southern rivers (Sefidrud and Kura River) and the evaporation over the CS become obvious for some periods. When pushing the FCSTs beyond the limits of the seasonal FCSTs to 1 year, considerable forecast skill can still be found. Validating only FCSTs by the present approach, which show the same trend as one based on a statistical method, significantly enhances the skill scores. [ABSTRACT FROM AUTHOR]

The Pataz–Parcoy gold-mining area, in the Eastern Andean Cordillera of northern Peru, is located on the western margin of the Amazonia craton, in a transtensional jog on the Cordillera Blanca Fault. Episodic subduction, accretion and rifting have taken place in the Eastern Andean Cordillera since the Mesoproterozoic. In the Pataz district, the Cambrian–Ordovician Vijus and Atahualpa formations comprise dacitic and rhyodacitic volcaniclastic rocks that formed by fractionation and/or crustal assimilation of a regionally more abundant andesitic parent melt. Mississippian magmatism began with enriched tholeiitic magmas that lack a Ti anomaly and formed by melting undepleted metasomatised asthenosphere. These magmas assimilated variable amounts of continental crust and were emplaced as Vista Florida Group volcaniclastic rocks, and dioritic plutons of the Pataz batholith. Ponding of these mantle-derived magmas in andesitic lower crust caused partial melting, which generated the volumetrically dominant, granodioritic component of the calc-alkaline (I-type) Pataz batholith. Within a few million years but following rifting, and uplift of the Pataz batholith, relatively K-rich (A-type) magmas formed by melting of a mid-crustal tonalitic source, and were emplaced in the upper crust as the latitic to rhyolitic Lavasen Volcanics and Esperanza subvolcanic complex. Anatexis in the mid crust was promoted by a second batch of magma derived from the undepleted metasomatised asthenosphere, evidence of which is preserved as mafic components of the Esperanza subvolcanic complex and post-Esperanza dolerite dykes. A K-rich magma chamber, the source of the Lavasen Volcanics and the Esperanza subvolcanic complex, is proposed as a possible source of the ore fluid, which deposited gold in veins hosted by the Pataz batholith. [ABSTRACT FROM AUTHOR]

Gold production in the Pataz district, northern Peru, is derived from mesothermal veins hosted by the Pataz batholith and basement-hosted epithermal and carbonate–base metal veins. At the regional scale, processing of Advanced Spaceborne Thermal Emission and Reflection Radiometer data can be used to delineate district-scale argillic alteration. One such area extends for tens of kilometres NNW of Vijus in the Maranon Valley. At the southern end of this area, basement-hosted quartz–carbonate–sulfide veins in faults support artisanal gold-mining operations. SEM analyses show that the alteration envelopes around these faults are dominated by illitic clays. These artisanal gold workings highlight the economic potential of the largely unexplored parts of the district-scale argillic alteration zone, further north. At the district scale, paleostress modelling maps areas of low minimum stress during Carboniferous ENE–WSW shortening, based on a new 1:25 000 geological map of the Pataz district. The resulting distribution of low minimum stress is used to predict sites of rock fracture under high fluid pressure, and consequent vein formation. These areas of low minimum stress occupy 11% of the modelled area but contain 50% of the known veins in the Pataz district. Some areas of low minimum stress contain no known veins, and where these are poorly explored or poorly exposed, they are proposed as potential targets for gold exploration. In combination with SEM microanalysis, ASD hyperspectral reflectance analysis of drill core samples shows that visible proximal sericitic alteration around batholith-hosted auriferous veins is predominantly phengitic illite. Automated software interpretation of ASD reflectance spectra usingThe Spectral Assistantshows that sericite in cryptic alteration distal from auriferous veins varies from mainly illite adjacent to the phengitic illite zone, to more distal muscovite. Reactivation of faults and mineralised vein contacts during the largely Cenozoic Andean orogeny produced chlorite alteration that locally overprints proximal phengitic illite alteration. ASD spectrometry identifies relict phengitic illite in some chloritic alteration zones and thus indicates proximity to mineralised veins at the deposit scale. Elevated pathfinder element concentrations within proximal phengitic illite alteration zones around batholith-hosted veins do not extend more than a few metres beyond the visible alteration envelope. The alkali alteration index [(Rb + Cs)/Th]Nis elevated above background levels for up to 15 m beyond the visible sericite alteration zone in one of two holes investigated. In the other hole, both [(Rb + Cs)/Th]Nand 3K/Al can be used as a lode-scale vector to gold-bearing veins within broad intersections of visible sericite alteration. [ABSTRACT FROM AUTHOR]

Archean Banded Iron Formation (BIF) hosts high-grade (>55% Fe) iron ore at the Matthew Ridge prospect, in the Jack Hills greenstone belt, of the Narryer terrane, Yilgarn Craton. Theca3000 Ma (SHRIMP U–Pb on zircons) Algoma-type BIF contains magnetite–hematite ore zones that are a product of successive overprinting hydrothermal alteration events. Rock types in the prospect area include Archean gneiss, metasedimentary rocks and BIF that are interlayered with dolerite. All rocks record peak amphibolite metamorphic mineral assemblages that are variably replaced by greenschist facies metamorphic minerals. Hypogene iron ore formed owing to: (1) the replacement of primary silica-rich bands in the quartz–magnetite BIF by Stage 1 hypogene magnesite and magnetite alteration; and (2) subsequent removal of Stage 1 magnesite to concentrate residual Stage 1 magnetite. These magnetite-rich ore bodies define <50 m-long by 20 m-wide lenses that trend NE and coincide with the hinge zones of Z-shaped, tight F1folds, which are most likely parasitic folds to the regional NE-trending, steeply NE-plunging anticline in the Jack Hills greenstone belt. Magnetite-rich ore zones are enriched in Fe and depleted in SiO2, with only minor changes in other major oxides and trace elements, compared with least-altered BIF. Magnetite-rich ore zones are locally cut by shear zone-hosted, talc–magnetite hydrothermal alteration overprinted by talc–microplaty hematite alteration. The shear zones and both talc mineral assemblages formed during a second deformation event that was characterised by NNE–SSE shortening. The third deformation event resulted in at least two generations of NE- to NW-trending extensional veins and strike-slip faults that locally cut the talc-rich shear zones. Supergene goethite–hematite replaces magnetite-rich ore bodies within 80 m of the present surface. The strong structural control and distinct hydrothermal alteration assemblages of the Matthew Ridge prospect are the best exploration indices for high-grade magnetite-rich ore in the region. [ABSTRACT FROM AUTHOR]

Purpose: Tumour-associated macrophages have been shown to promote proliferation, angiogenesis and metastasis in several carcinomas. The effect on colon cancer has not yet been clarified. Furthermore, Kupffer cells in the liver might initiate the formation of metastases by directly binding tumour cells. Methods: An orthotopic syngeneic mouse model of colon cancer as well as a liver metastases model has been studied, using murine CT-26 colon cancer cells in Balb/c-mice. Macrophages were depleted in both models by clodronate liposomes. Tumour sizes and metastases were determined using 7-Tesla MRI. The macrophage and vascular density in the orthotopic tumours as well as the Kupffer cell density in the livers were evaluated using immunohistochemistry. Results: Animals in the macrophage-depleted group displayed significantly smaller primary tumours (37 ± 20 mm) compared to the control group (683 ± 389 mm, p = 0.0072). None of the mice in the depleted group showed liver or peritoneal metastases, whereas four of six control mice displayed liver and five out of six mice peritoneal metastases. The vascular density was significantly lower in the macrophage-depleted group ( p = 0.0043). In the liver metastases model, animals of the Kupffer cell-depleted group (14.3 ± 7.7) showed significantly less liver metastases than mice of the two control groups (PBS liposomes, 118.5 ± 28.2, p = 0.0117; NaCl, 81.7 ± 23.2, p = 0.0266). The number of liver metastases correlated directly with the Kupffer cell density ( p = 0.0221). Conclusion: Macrophages promote tumour growth, angiogenesis and metastases in this orthotopic syngeneic mouse model. Kupffer cells enhance the formation of metastases in the liver. [ABSTRACT FROM AUTHOR]

Future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Intercomparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed for differences between impact models. Projections of change from a baseline period (1981-2010) to the future (2070-2099) from 12 impacts models which contributed to the hydrological and biomes sectors of ISI-MIP were studied. The biome models differed from the hydrological models by the inclusion of CO2 impacts and most also included a dynamic vegetation distribution. The biome and hydrological models agreed on the sign of runoff change for most regions of the world. However, in West Africa, the hydrological models projected drying, and the biome models a moistening. The biome models tended to produce larger increases and smaller decreases in regionally averaged runoff than the hydrological models, although there is large inter-model spread. The timing of runoff change was similar, but there were differences in magnitude, particularly at peak runoff. The impact of vegetation distribution change was much smaller than the projected change over time, while elevated CO2 had an effect as large as the magnitude of change over time projected by some models in some regions. The effect of CO2 on runoff was not consistent across the models, with two models showing increases and two decreases. There was also more spread in projections from the runs with elevated CO2 than with constant CO2. The biome models which gave increased runoff from elevated CO2 were also those which differed most from the hydrological models. Spatially, regions with most difference between model types tended to be projected to have most effect from elevated CO2, and seasonal differences were also similar, so elevated CO2 can partly explain the differences between hydrological and biome model runoff change projections. Therefore, this shows that a range of impact models should be considered to give the full range of uncertainty in impacts studies. [ABSTRACT FROM AUTHOR]

Soil moisture is an essential climate variable of major importance for land-atmosphere interactions and global hydrology. An appropriate representation of soil moisture dynamics in global climate models is therefore important. Recently, a first multidecadal, observational based soil moisture data set has become available that provides information on soil moisture dynamics from satellite observations (ECVSM). The present study investigates the potential and limitations of this new dataset for several applications for climate model evaluation. We compare soil moisture data from satellite observations, reanalysis data and simulation results from a state-of-the-art climate model and analyze relationships between soil moisture and precipitation anomalies in the different datasets. In a detailed regional study, we show that ECVSM is capable to capture well interannual and intraannual soil moisture and precipitation dynamics in the Sahelian region. Current deficits of the new dataset are critically discussed and summarized at the end of the paper to provide guidance for an appropriate usage of the ECVSM dataset for climate studies. [ABSTRACT FROM AUTHOR]

Apatite was separated from four samples of syenite porphyry, taken from the Karari gold deposit, in the Kurnalpi Terrane of the Archean Kalgoorlie-Kurnalpi Rift, Eastern Goldfields Superterrane (EGST). The alkalic composition of the syenitic magmas inhibited zircon crystallisation, so apatite provided the best mineral for geochronological investigations. LA-ICP-MS analysis of U, Th and Pb isotopes in the apatite gave a relatively wide range of lower intercept ages, with large errors, ranging from 1 to 3%, using OD-306 apatite as the primary standard. Cathodoluminescent (CL)-darker cores that comprise the major volume of apatite grains are relatively homogeneous in two samples, with one having clear oscillatory zoning. These samples yielded intercept ages of 2701 ± 34 Ma and 2699 ± 25 Ma, respectively. These ages are interpreted to approximate the magmatic crystallisation age of the apatite. Younger intercept ages were generated by apatite from two other samples, which display more complex and heterogeneous patterns of CL brightness. The apatite ages from these two samples are interpreted to have been produced by integrated analysis of apatite that has been heterogeneously modified by younger events. However, the magnitude of the temporal gap between magma emplacement and closure of the U–Pb system in apatite from these two samples remains unknown. Our best estimate of the age of the magmatic apatite from at least two of the syenitic intrusions at Karari is ca 2.70 Ga, which identifies these as the oldest intrusions of the Syenitic Group of magmas yet identified in the EGST. However, if ages are corrected to offset observed in the 401 apatite secondary standard, the two oldest syenitic intrusions are dated at ca 2660 Ma. Syenite porphyry intrusions are spatially associated with gold mineralisation at Karari, gold deposit, WA. Apatite in the syenite porphyry intrusions has been used to determine the age of the intrusions in these zircon-poor rocks. LA-ICP-MS analysis of U–Pb isotopes from two intrusions produce apatite ages that are interpreted to approximate the age of magmatic crystallisation. The interpreted magmatic dates are older than any previously dated syenitic intrusions in the Kalgoorlie-Kurnalpi Rift. [ABSTRACT FROM AUTHOR]

The article discusses a study on the effect of climate change on available water resources using hydrology and multiple global climate models. It states that a large spread of climate change projection in water resources in the climate-hydrology modeling chain. It concludes that the impact of climate change does not only rely on climate models and emission scenarios.

Many studies have investigated potential climate change impacts on regional hydrology; less attention has been given to the components of uncertainty that affect these scenarios. This study quantifies uncertainties resulting from (I) General Circulation Models (GCMs), (ii) Regional Climate Models (RCMs), (iii) bias-correction of RCMs, and (iv) hydrological model parameterization using a multi model framework. This consists of three GCMs, three RCMs, three bias-correction techniques, and sets of hydrological model parameters. The study is performed for the Lech watershed (~1000 km²), located in the Northern Limestone Alps, Austria. Bias-corrected climate data are used to drive the hydrological model HQsim to simulate runoff under present (1971-2000) and future (2070-2099) climate conditions. Hydrological model parameter uncertainty is assessed by Monte Carlo sampling. The model chain is found to perform well under present climate conditions. However, hydrological projections are associated with large uncertainty, mainly due to the choice of GCM and RCM. Uncertainty due to biascorrection is found to have greatest influence on projections of extreme river flows and the choice of method(s) is an important consideration in snowmelt systems. Overall, hydrological model parameterization is least important. The study also demonstrates how an improved understanding of the physical processes governing future river flows can help focus attention on the scientifically tractable elements of the uncertainty. [ABSTRACT FROM AUTHOR]

In this study we present the development of the dynamical wetland extent scheme (DWES) and its validation against present day wetland observations. The DWES is a simple, global scale hydrological scheme that solves the water balance of wetlands and estimates their extent dynamically. The extent depends on the balance of water flows in the wetlands and the slope distribution within the grid cells. In contrast to most models, the DWES is not directly calibrated against wetland extent observations. Instead, wetland affected river discharge data are used to optimize global parameters of the model. The DWES is not a complete hydrological model by itself but implemented into the Max Planck Institute -- Hydrology Model (MPI-HM). However, it can be transferred into other models as well. For present climate, the model validation reveals a good agreement between the occurrence of simulated and observed wetlands on the global scale. The best result is achieved for the northern hemisphere where not only the wetland distribution pattern but also their extent is simulated reasonably well by the DWES. However, the wetland fraction in the tropical parts of South America and Central Africa is strongly overestimated. The simulated extent dynamics correlate well with monthly inundation variations obtained from satellite for most locations. Also, the simulated river discharge is affected by wetlands resulting in a delay and mitigation of peak flows. Compared to simulations without wetlands, we find locally increased evaporation and decreased river flow into the oceans due to the implemented wetland processes. In summary, the validation analysis demonstrates the DWES' ability to simulate the global distribution of wetlands and their seasonal variations. Thus, the dynamical wetland extent scheme can provide hydrological boundary conditions for wetland related studies. In future applications, the DWES should be implemented into an earth system model to study feedbacks between wetlands and climate. [ABSTRACT FROM AUTHOR]

We investigate the capability of the regional climate model REMO to adequately simulate the mesoscale climate patterns of southern Africa, thereby focusing on South-West Africa (SWA). The simulations are conducted at a horizontal resolution of about 18 km for the period from 1958 to 2007. Boundary forcing is taken from ERA40 reanalysis and subsequent operational analyses data. This study is the first long-term dynamical downscaling study for southern Africa on a very high horizontal resolution. To evaluate the model results, we use a set of different observations to compare with model output data. This analysis indicates that the model results agree rather well with observations for both spatial as well as temporal patterns. Especially along the focus region in SWA, REMO results are very close to observations. For this region we show that dynamical downscaling of the ERA40 reanalysis data with the REMO model leads to an improved description of the seasonal precipitation characteristics. Remaining deficits, which mainly occur in the simulation of the 2-m air temperature, can be explained with the setup of the model's soil routine and will be investigated further. On the basis of the findings of this study we conclude that the model is well suited for the simulation of the regional climate over the southern African region. High-resolution model output implies more detailed climate information and can lead to a significant improvement in the representation of spatial patterns. It is therefore beneficial to use regional climate model data when assessing climate change-induced impacts on a regional scale. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Due to biases in the output of climate models, a bias correction is often needed to make the output suitable for use in hydrological simulations. In most cases only the temperature and precipitation values are bias corrected. However, often there are also biases in other variables such as radiation, humidity and wind speed. In this study we tested to what extent it is also needed to bias correct these variables. Responses to radiation, humidity and wind estimates from two climate models for four large-scale hydrological models are analysed. For the period 1971-2000 these hydrological simulations are compared to simulations using meteorological data based on observations and reanalysis; i.e. the baseline simulation. In both forcing datasets originating from climate models precipitation and temperature are bias corrected to the baseline forcing dataset. Hence, it is only effects of radiation, humidity and wind estimates that are tested here. The direct use of climate model outputs result in substantial different evapotranspiration and runoff estimates, when compared to the baseline simulations. A simple bias correction method is implemented and tested by rerunning the hydrological models using bias corrected radiation, humidity and wind values. The results indicate that bias correction can successfully be used to match the baseline simulations. Finally, historical (1971-2000) and future (2071-2100) model simulations resulting from using bias corrected forcings are compared to the results using non-bias corrected forcings. The relative changes in simulated evapotranspiration and runoff are relatively similar for the bias corrected and non bias corrected hydrological projections, although the absolute evapotranspiration and runoff numbers are often very different. The simulated relative and absolute differences when using bias corrected and non bias corrected climate model radiation, humidity and wind values are, however, smaller than literature reported differences resulting from using bias corrected and non bias corrected climate model precipitation and temperature values. [ABSTRACT FROM AUTHOR]

high-resolution pre-industrial control simulation with the regional climate model REMO is analyzed in detail for different European subregions. To our knowledge, this is the first long pre-industrial control simulation by a regional climate model as well as at comparable resolution. We assess the ability of the climate model to reproduce the observed climate variability in various parts of the continent. In order to investigate the representation of extreme events in the model under pre-industrial greenhouse gas concentrations, selected seasons are examined with regard to the atmospheric circulation and other climatic characteristics that have contributed to the occurrences. A special focus is dedicated to land-atmosphere interactions. Extreme seasons are simulated by the model under various circumstances, some of them strongly resemble observed periods of extraordinary conditions like the summer 2003 or autumn 2006 in parts of Europe. The regional perspective turns out to be of importance when analyzing events that are constituted by meso-scale atmospheric dynamics. Moreover, the predictability of the European climate on seasonal to decadal time scales is examined by relating the statistics of surface variables to large-scale modes of variability impacting the North Atlantic sector like the Meridional Overturning Circulation, the El Niño Southern Oscillation, and the North Atlantic Oscillation. For this purpose, we introduce a measure of tail dependence that quantifies the correlation between extreme values in two variables that describe the state of the climate system. Significant dependence of extreme events can be detected in various situations. [ABSTRACT FROM AUTHOR]

The seasonal variation of snow-free land surface albedo was integrated into the land surface schemes of the global climate model ECHAM5 and the regional climate model REMO to test the sensitivity of climate models to the advanced surface albedo parameterisation. This new albedo parameterisation was developed in previous studies describing the monthly varying surface albedo fields as a function of vegetation phenology derived from MODIS data products. Three model simulations were performed in order to study the sensitivity of the simulated climate to the seasonal background albedo variations: 1. control simulation with the old time-invariant surface background albedo, 2. experiment 1 with the new mean time-invariant surface background albedo field, 3. experiment 2 with the monthly varying surface background albedo as a function of the leaf area index. The analysis of the simulation results demonstrates the influence of the new albedo parameterisation on the model simulations. Strong effects occur over Europe with the regional and the global model simulations responding differently to seasonal background albedo variations. In contrast to the global simulation, where the large-scale conditions are changed by the new albedo parameterisation, in the regional simulations the circulation patterns within the model domain are not influenced. Here, the external forcing via the lateral boundaries of the regional model domain suppress changes in the large-scale circulation that might occur without the external forcing. In the regional model simulations only local effects occur mainly during the summer season, when the vertical energy exchange at the land surface is enhanced compared to the winter season. The comparison of the regional and global simulation results over Europe reveals that the global model shows higher sensitivity to the changed albedo parameterization with respect to the simulated annual temperature and precipitation cycle than the regional model. For both the regional and the global study the temperature and precipitation deviations from the observations are larger than the differences between the three model simulations. [ABSTRACT FROM AUTHOR]

Detailed fluid geochemistry studies on hydrothermal quartz veins from the Rouyn-Noranda and Val-d'Or areas along the transcrustal Cadillac Tectonic Zone (CTZ) indicate that unmineralized (with respect to gold) sections of the CTZ contained a distinct CO2-dominated, H2S-poor hydrothermal fluid. In contrast, both gold mineralized sections of the CTZ (e.g., at Orenada #2) and associated higher order shear zones have a H2O–CO2 ± CH4–NaCl hydrothermal fluid. Their CO2/H2S ratios indicate H2S-rich compositions. The Br/Cl compositions in fluid inclusions trapped in these veins indicate that hydrothermal fluids have been equilibrated with the crust. Oxygen isotope ratios from hydrothermal quartz veins in the CTZ are consistently 2‰ more enriched than those of associated higher order shear zones, which are interpreted to be a function of greater fluid/rock ratios in the CTZ and lower fluid/rock ratios, and more efficient equilibration of the hydrothermal fluid with the wall rock, in higher order shear zones. An implication from this study is that the lower metal endowment of the transcrustal CTZ, when compared with the higher metal endowment in higher order shear zones (ratio of about 1 : 1000), may be the result of the lack of significant amounts of H2O–H2S rich fluids in most of the CTZ. In contrast, gold mineralization in the higher order shear zones appear to be controlled by the high H2S activity of the aqueous fluids, because gold was likely transported in a bisulfide complex and was deposited during sulfidation reactions in the wall rock and phase separation in the quartz veins. [ABSTRACT FROM AUTHOR]

The most recent version of the Max Planck Institute for Meteorology atmospheric general circulation model, ECHAM5, is used to study the impact of changes in horizontal and vertical resolution on seasonal mean climate. In a series of Atmospheric Model Intercomparison Project (AMIP)-style experiments with resolutions ranging between T21L19 and T159L31, the systematic errors and convergence properties are assessed for two vertical resolutions. At low vertical resolution (L19) there is no evidence for convergence to a more realistic climate state for horizontal resolutions higher than T42. At higher vertical resolution (L31), on the other hand, the root-mean-square errors decrease monotonically with increasing horizontal resolution. Furthermore, except for T42, the L31 versions are superior to their L19 counterparts, and the improvements become more evident at increasingly higher horizontal resolutions. This applies, in particular, to the zonal mean climate state and to the stationary wave patterns in boreal winter. As in previous studies, increasing horizontal resolution leads to a warming of the troposphere, most prominently at midlatitudes, and to a poleward shift and intensification of the midlatitude westerlies. Increasing the vertical resolution has the opposite effect, almost independent of horizontal resolution. Whereas the atmosphere is colder at low and middle latitudes, it is warmer at high latitudes and close to the surface. In addition, increased vertical resolution results in a pronounced warming in the polar upper troposphere and lower stratosphere, where the cold bias is reduced by up to 50% compared to L19 simulations. Consistent with these temperature changes is a decrease and equatorward shift of the midlatitude westerlies. The substantial benefits in refining both horizontal and vertical resolution give some support to scaling arguments deduced from quasigeostrophic theory implying that horizontal and vertical resolution ought to be chosen consistently. [ABSTRACT FROM AUTHOR]

In recent years, there has been growing concern that environmental pollutants in general, and organochlorines in particular, adversely affect male fertility. Therefore, we investigated the effects of tris(4-chlorophenyl)methanol (TCPM), non-ortho PCB 77 and γ-hexachlorocyclohexane ( γ-HCH, lindane) on human sperm functions in vitro. Human spermatozoa from healthy donors were washed in human tubular fluid medium containing 1% human serum albumin, filtered through glass wool and exposed to different concentrations of TCPM, PCB 77 or γ-HCH. After incubation for 5 h at 37 °C and 5% CO2, sperm vitality and the percentage of living acrosome-reacted spermatozoa were examined using triple stain technique. Total sperm motility was evaluated by computer-assisted sperm analysis (Stroemberg-Mika) after 5 h. For TCPM, total motility was additionally measured after 18 and 40 h. Different concentrations of PCB 77 and γ-HCH did not alter the percentage of spontaneous living acrosome-reacted spermatozoa, vitality and total motility. TCPM dose-dependently altered sperm motility, vitality and acrosome reaction. The percentage of living acrosome-reacted spermatozoa was increased at overtly toxic concentrations. Therefore, it is suggested that unspecific acrosomal loss has been induced by degenerative processes. In conclusion, even high concentrations of PCB 77 and γ-HCH did not affect human sperm functions in vitro. Only very high cytotoxic TCPM concentrations modulated spontaneous acrosome reaction and total motility. Therefore, in vivo effects on human sperm function seem to be unlikely. However, individual susceptibility has to be considered and little is known about additive and possible synergistic effects as other environmental pollutants with similar potencies have been found in the human male and female reproductive tract. [ABSTRACT FROM AUTHOR]