Escherichia coli strains harvested from springs in Kampala,Uganda: cell characterization and transport in saturated porous media

We hypothesized that the transport of Escherichia coli strains harvested from springs could be characterized by a similar set of cell characteristics and transport parameters. The hypothesis was tested by sampling springs throughout the Lubigi catchment in Kampala, Uganda. Chemo‐physical parameters in addition to total coliform concentrations were determined. Furthermore, E. coli strains were harvested, and cell properties determined. Column experiments in saturated quartz columns of 7 cm height were conducted to determine transport parameters of selected E. coli strains. Using a two‐site non‐equilibrium sorption model, transport was modelled by fitting breakthrough data in HYDRUS 1D. Results indicated faecal contamination of the springs with high concentrations of total coliforms, chloride and nitrate. Furthermore, the maximum relative E. coli concentrations (C/C₀)_max in the column experiments were high. Compared with our previous work on E. coli strains, collected from a pasture and from zoo animals, attachment was low. Modelling revealed that both equilibrium and kinetic sorption were not important under conditions employed in the experiments. These observations are explained by the way in which the strains were harvested: from termination points of flow lines (springs). Such strains may possess characteristics that might have influenced their transport in the subsurface leading to their low attachment efficiency and possibly contributing to the lack of influence of equilibrium and kinetic sorption characteristics. There was no significant correlation between cell properties and transport parameters. Furthermore, 58% of the tested strains were of the O21:H7 serotype, and all definable serotypes identified were associated with diseases. We speculate that this serotype may possess characteristics that allow preferential transport through the aquifers of the area. We demonstrated that bacteria harvested from termination points of flow lines compared with those obtained from pollution sources, which have not undergone transport yet, present a good option for the assessment of bacteria transport characteristics in aquifers. Copyright © 2013 John Wiley & Sons, Ltd.     

Modern and early Holocene mollusc fauna of the Ounianga lakes (northern Chad): implications for the palaeohydrology of the central Sahara

The fresh and saline lakes of Ounianga Kebir and Serir in northeastern Chad are among the very few permanent aquatic ecosystems currently existing in the hyper‐arid core of the Sahara desert. The confirmed modern fauna of aquatic molluscs at Ounianga comprises three widespread species (Melanoides tuberculata, Biomphalaria pfeifferi and Lymnaea natalensis), of which only the first appears to maintain a thriving population. We recovered seven more species of gastropods, among which one is new to science (Gabbiella ouniangaensis), and one bivalve species from early Holocene outcrops of diatomaceous limestone at Ounianga Serir. All species except one are known to be commonly spread between lake and river systems by birds, and in its entirety this species‐rich fossil mollusc fauna of Ounianga Serir resembles that of other Saharan lake sites known to have been hydrologically isolated during the early Holocene. The impoverished modern mollusc fauna, which lacks even the widespread and opportunistic species Bulinus truncatus, may have become established relatively recently through new colonisation events, following eradication of the early Holocene mollusc fauna during a later episode of high salinity or desiccation. Copyright © 2011 John Wiley & Sons, Ltd.     

Occurrence of long chain 1,14-diols in Apedinella radians

Long chain 1,14-diols have been reported in diatoms of the genus Proboscia and applied as specific biomarker lipids for such algae. We report here the presence of saturated C₂₈, C₃₀ and C₃₂ 1,14-diols in a culture of the marine heterokont alga Apedinella radians (Class Dictyochophyceae, order Pedinellales). Apedinella species occur globally, although predominantly in estuarine waters, so the finding has potential implications for the use of long chain 1,14-diols as biomarkers of Proboscia diatoms and as an indicator of upwelling.     

Improved antenna phase center models for GLONASS

Thanks to the increasing number of active GLONASS satellites and the increasing number of multi-GNSS tracking stations in the network of the International GNSS Service (IGS), the quality of the GLONASS orbits has become significantly better over the last few years. By the end of 2008, the orbit RMS error had reached a level of 3–4 cm. Nevertheless, the strategy to process GLONASS observations still has deficiencies: one simplification, as applied within the IGS today, is the use of phase center models for receiver antennas for the GLONASS observations, which were derived from GPS measurements only, by ignoring the different frequency range. Geo++ GmbH calibrates GNSS receiver antennas using a robot in the field. This procedure yields now separate corrections for the receiver antenna phase centers for each navigation satellite system, provided its constellation is sufficiently populated. With a limited set of GLONASS calibrations, it is possible to assess the impact of GNSS-specific receiver antenna corrections that are ignored within the IGS so far. The antenna phase center model for the GLONASS satellites was derived in early 2006, when the multi-GNSS tracking network of the IGS was much sparser than it is today. Furthermore, many satellites of the constellation at that time have in the meantime been replaced by the latest generation of GLONASS-M satellites. For that reason, this paper also provides an update and extension of the presently used correction tables for the GLONASS satellite antenna phase centers for the current constellation of GLONASS satellites. The updated GLONASS antenna phase center model helps to improve the orbit quality.     

Human biometeorological evaluation of heat-related mortality in Vienna

The relationship between heat stress and mortality in the federal state of Vienna (Austria) was analyzed from 1970 to 2007. Long-term trends of mortality data and short-term adaptation to heat stress were considered by two complex approaches. The evaluation is based on the human biometeorological parameter, physiologically equivalent temperature. The results revealed a significant impact of heat stress on the human health, with a significantly higher sensitivity on women compared to men. Additionally, higher risks of deaths due to cardiovascular and respiratory diseases were found. During the long period of 38?years, some significant decreases of the sensitivity were found, especially in the medium heat stress levels. This could indicate active processes of long-term adaptation to the increasing heat stress.     

Simulating the hydrological response to predicted climate change on a watershed in southern Alberta, Canada

The current body of research in western North America indicates that water resources in southern Alberta are vulnerable to climate change impacts. The objective of this research was to parameterize and verify the ACRU agro-hydrological modeling system for a small watershed in southern Alberta and subsequently simulate the change in future hydrological responses over 30-year simulation periods. The ACRU model successfully simulated monthly streamflow volumes (r ²?=?0.78), based on daily simulations over 27 years. The delta downscaling technique was used to perturb the 1961?C1990 baseline climate record from a range of global climate model (GCM) projections to provide the input for future hydrological simulations. Five future hydrological regimes were compared to the 1961?C1990 baseline conditions to determine the average net effect of change scenarios on the hydrological regime of the Beaver Creek watershed over three 30-year time periods (starting in 2010, 2040 and 2070). The annual projections of a warmer and mostly wetter climate in this region resulted in a shift of the seasonal streamflow distribution with an increase in winter and spring streamflow volumes and a reduction of summer and fall streamflow volumes over all time periods, relative to the baseline conditions (1961?C1990), for four of the five scenarios. Simulations of actual evapotranspiration and mean annual runoff showed a slight increase, which was attributed to warmer winters, resulting in more winter runoff and snowmelt events.     

Impact of the Atlantic Warm Pool on precipitation and temperature in Florida during North Atlantic cold spells

Recurrent phases of increased pine at Lake Tulane, Florida have previously been related to strong stadials terminated by so-called Heinrich events. The climatic significance of these pine phases has been interpreted in different ways. Using a pollen?Cclimate inference model, we quantified the climate changes and consistently found that mean summer precipitation (P _JJA) increased (0.5?C0.9?mm/day) and mean November temperature increased (2.0?C3.0°C) during pine phases coeval with Heinrich events and the Younger Dryas. Marine sea surface temperature records indicate that potential sources for these moisture and heat anomalies are in the Gulf of Mexico and the western tropical Atlantic. We explain this low latitude warming by an increased Loop Current facilitated by persistence of the Atlantic Warm Pool during summer. This hypothesis is supported by a climate model sensitivity analysis. A positive heat anomaly in the Gulf of Mexico and equatorial Atlantic best approximates the pollen-inferred climate reconstructions from Lake Tulane during the (stadials around) Heinrich events and the Younger Dryas.     

A method to calculate cloud-free long-wave irradiance at the surface based on radiative transfer modeling and temperature lapse rate estimates

We demonstrate a method to improve the performance of commonly used parameterizations to calculate the cloud-free down-welling long-wave radiation at the surface. The method uses a monthly climatology of the effective radiating temperature of the atmosphere instead of the instantaneous screen-level temperature. The climatology of the effective radiating temperature can be derived from pyrgeometer measurements and was incorporated into two commonly used schemes. We compared the calculated cloud-free down-welling long-wave irradiances to high-quality pyrgeometer measurements from four Swiss sites. The discrepancies between observations and modified schemes can be reduced by up to 35 %, resulting in a model uncertainty close to 5 W m^?2 which corresponds to the measurement uncertainty of pyrgeometers. Furthermore, we introduce a new long-wave model which is based on radiative transfer calculations in the 8–14- $\upmu $ m wavelength range. In the remaining long-wave spectrum, the radiation is calculated using the Planck function with the effective radiating temperature of the atmosphere. The performance of this new model is consistent with the modified parameterizations.     

Lake surface temperatures in a changing climate: a global sensitivity analysis

We estimate the effects of climatic changes, as predicted by six climate models, on lake surface temperatures on a global scale, using the lake surface equilibrium temperature as a proxy. We evaluate interactions between different forcing variables, the sensitivity of lake surface temperatures to these variables, as well as differences between climate zones. Lake surface equilibrium temperatures are predicted to increase by 70 to 85 % of the increase in air temperatures. On average, air temperature is the main driver for changes in lake surface temperatures, and its effect is reduced by ~10 % by changes in other meteorological variables. However, the contribution of these other variables to the variance is ~40 % of that of air temperature, and their effects can be important at specific locations. The warming increases the importance of longwave radiation and evaporation for the lake surface heat balance compared to shortwave radiation and convective heat fluxes. We discuss the consequences of our findings for the design and evaluation of different types of studies on climate change effects on lakes.     

Simulation of groundwater mounding at a West Australian mine site

Few studies exist that investigate the potential impact of groundwater mounding due to mining near an environmentally sensitive area in a real world scenario. This paper presents a case study in which the development and extent of groundwater mounding due to mining near the Shark Bay World Heritage Property (SBWHP) in Western Australia (WA) has been simulated. A numerical model was developed that enabled a detailed simulation of groundwater level response to the discharge of a water saturated sand slurry during mining at the project site near Coburn in WA. The simulations showed that after a mining period of around two and a half years, a groundwater mound of around 2.5 m would develop along the margins of the open pit at the SBWHP boundary. 500 m further into the SBWHP, the groundwater mound is predicted to be around 1 m high. A depth to water analysis showed that the groundwater may come within 4 m of the surface in the area of a sand dune swale that traverses from SW to NE near the SBWHP boundary. The results of these analyses provide a perspective of mine-related impacts in a unique environment. The results have been included in an environmental impact assessment (EIA) and used for mine water balance predictions.