Impact of tailings from the Kilembe copper mining district on Lake George, Uganda

The abandoned Kilembe copper mine in western Uganda is a source of contaminants, mobilised from mine tailings into R. Rukoki flowing through a belt of wetlands into Lake George. Water and sediments were investigated on the lakeshore and the lakebed. Metal associations in the sediments reflect the Kilembe sulphide mineralisation. Enrichment of metals was compared between lakebed sediments, both for wet and dry seasons. Total C in a lakebed core shows a general increment, while Cu and Co decrease with depth. The contaminants are predominant (> 65%) in the ≤ 63 μm sediment size range with elevated Cu and Zn (> 28%), while Ni, Pb and Co are low (< 18%) in all the fractions. Sequential extraction of Fe for lakeshore sediment samples reveals low Fe mobility. Relatively higher mobility and biological availability is seen for Co, Cu and S. Heavy metal contents in lake waters are not an immediate risk to the aquatic environment.     

Has urbanization changed ecological streamflow characteristics in Maine (USA)?

Abstract

This paper examines the potential effects of urbanization on streamflow in Maine, USA, from 1950 to 2000. The study contrasts nine watersheds in southern Maine, which has seen steady urban growth over the study period, with nine rural watersheds from northern Maine. Historical population data and current land cover data are used to develop an urbanization score for each watershed. Trends in watershed urbanization over the study period are compared to trends in ecologically relevant streamflow characteristics. The results indicate that trends in northern, rural watersheds are much more consistent than the trends in the southern watersheds. Additionally, trends in the southern watersheds are inconsistent with the hydrological characteristics observed in urban watersheds elsewhere, likely due to the comparatively low level of current urban development in Maine's urban watersheds. Our study suggests that urban areas in Maine have not yet reached an urbanization threshold where streamflow impacts become consistently detectable.

Editor Z.W. Kundzewicz

Citation Martin, E.H., Kelleher, C., and Wagener, T., 2012. Has urbanization changed ecological streamflow characteristics in Maine (USA)? Hydrological Sciences Journal, 57 (7), 1337–1354.     

Solar Cycle Variation in Solar f-Mode Frequencies and Radius

Using data from the Global Oscillation Network Group (GONG) covering the period from 1995 to 1998, we study the change with solar activity in solar f-mode frequencies. The results are compared with similar changes detected from the Michelson Doppler Imager (MDI) data. We find variations in f-mode frequencies which are correlated with solar activity indices. If these changes are due to variation in solar radius then the implications are that the solar radius decreases by about 5 km from minimum to maximum activity.     

Transmission electron microscopy of experimentally deformed chalcopyrite single crystals

Two crystals of natural chalcopyrite, CuFeS₂, experimentally deformed at 200° C have been studied by means of transmission electron microscopy (TEM). The activated glide planes are (001) and {112}. The dislocations in (001) have the Burgers vector [110] and a predominating edge character. They are split into two colinear partials b=1/2[110] and can cross split into {112}. The dislocations in {112} consist of straight segments along low index lattice lines. They are often arranged in dipoles generating trails of loops. Few dislocations with b=1/2[ \(\overline {11} \) 1] and [1 \(\bar 1\) 0] are present and dislocations with b=[0 \(\bar 2\) 1] occur in low angle subgrain boundaries. From weak beam contrasts it is presumed that most of the dislocations gliding in {112} have b=1/2〈3 \(\overline {11} \) 〉. They are dissociated into up to four partials. Microtwins and different types of stacking faults in {112} also occur. Models of the dissociation of dislocations are discussed.     

Mineralogy, 57Fe Mössbauer spectra and magnetization of chalcolithic pottery

Three chalcolithic pottery sherds, paint removed from the surface of each sherd, and an unheated red pigment (Tell-Halaf culture, Turkey) were analysed within the frame of archaeometric studies using mineralogical methods, ⁵⁷Fe Mössbauer spectroscopy, magnetization and rotational hysteresis data. From mineralogical results, the individual minerals forming the cores of the sherds were determined. It was found that the sherds are lime-rich. High temperature X-ray analysis on comparable Ca-rich material showed that the established composition is consistent with a firing temperature of 750-950°C. Apart from the pigment, each Mössbauer spectrum of Fe-bearing components consists of dominating paramagnetic doublets, arising mostly from silicate phases, and of a six-line pattern with reduced intensity, due to ferri- and/or antiferromagnetic Fe-oxide phases. For three samples, an Fe³⁺ silicate component of the spectra is clearly dominating, which points to oxidizing conditions during firing. For the others Fe²⁺ and Fe³⁺ components occur in about equal intensities. For the pigment, the magnetic sextet is of similar intensity to the Fe³⁺ silicate component. From magnetic analysis of ferrimagnetic phases it follows that a low percentage of particles of solid solutions -Fe₂O₃ – Fe₃O₄ exist, probably in part 0.1 m in diameter. The ferrimagnetic particles of at least one paint are probably covered by a thin layer of hematite as found from rotational hysteresis data. An attempt is made to draw conclusions from the experimental results, regarding the firing conditions of the sherds and paints.     

Ultrasonic attenuation of pure tetrahydrofuran hydrate

Improved estimates of the amount of subsurface gas hydrates are needed for natural resource, geohazard, and climate impact assessments. To evaluate gas hydrate saturation from seismic methods, the properties of pure gas hydrates need to be known. Whereas the properties of sediments, specifically sands, and hydrate‐bearing sediments are well studied, the properties of pure hydrates are largely unknown. Hence, we present laboratory ultrasonic P‐wave velocity and attenuation measurements on pure tetrahydrofuran hydrates as they form with reducing temperatures from 25°C to 1°C under atmospheric pressure conditions. Tetrahydrofuran hydrates, with structure II symmetry, are considered as proxies for the structure I methane hydrates because both have similar effects on elastic properties of hydrate‐bearing sediments. We find that although velocity increased, the waveform frequency content and amplitude decreased after the hydrate formation reaction was complete, indicating an increase in P‐wave attenuation after hydrate formation. When the tetrahydrofuran hydrate was cooled below the freezing point of water, velocity and quality factor increased. Nuclear Magnetic Resonance results indicate the presence of water in the “pure hydrate” samples above the water freezing point, but none below. The presence of liquid water between hydrate grains most likely causes heightened attenuation in tetrahydrofuran hydrates above the freezing point of water. In naturally occurring hydrates, a similarly high attenuation might relate to the presence of water.     

Physical parameters measured on cores and cuttings from the pilot well (0 m–4000.1 m) of the German continental deep drilling program (KTB) in the Oberfalz area,Bavaria, Federal Republic of Germany

The project of an ultradeep drill hole (KTB) in the Oberpfalz area at the western margin of the Bohemian Massif has completed a pilot drill hole to a depth of 4000.1 m in April 1989. This well is situated only about 200m away from the main drill hole aimed at 10 km depth where drilling started in September 1990. The cores of the pilot well have a diameter of 9.4 cm or 10.16 cm, respectively. In addition to cores and cuttings there was also mud available for geochemical, petrological and some geophysical measurements. The pilot drill hole has a core recovery length of as much as 3042.6 m (about 76%), among which 193.1 m were obtained by rotary drilling and 2849.5 m by wireline drilling. Several petrophysical parameters were measured in a specially established field laboratory at the drill site immediately after sampling in order to obtain as good as possible in-situ values. Results for the following parameters are reported: density, natural gamma ray activity, velocities of seismic longitudinal and shear waves, thermal conductivity, electrical resistivity, natural remanent magnetization, magnetic susceptibility, porosity and inner surface. The methods of measurement are characterized briefly and the results of the pilot drill hole are presented and discussed in connection with the lithology and the geophysical anomalies, which have been observed on the surface.     

Evaluating the geomorphic channel response to beaver dam analog installation using unoccupied aerial vehicles

Beaver dam analogs (BDAs) are a stream restoration technique that is rapidly gaining popularity in the western United States. These low-cost, stream-spanning structures, designed after natural beaver dams, are being installed to confer the ecologic, hydrologic, and geomorphic benefits of beaver dams in streams that are often too degraded to provide suitable beaver habitat. BDAs are intended to slow streamflow, reduce the erosive power of the stream, and promote aggradation, making them attractive restoration tools in incised channels. Despite increasing adoption of BDAs, few studies to date have monitored the impacts of BDAs on channel form. Here, we examine the geomorphic changes that occurred within the first year of restoration efforts in Wyoming using high-resolution visible light orthomosaics and elevation data collected with unoccupied aerial vehicles (UAVs). By leveraging the advantages of rapidly acquired images from UAV surveys with recent advancements in structure-from-motion photogrammetry, we constructed centimeter-scale digital elevation models (DEMs) of the restoration reach and an upstream control reach. Through DEM differencing, we identified areas of enhanced erosion and deposition near the BDAs, suggesting BDA installation initiated a unique geomorphic response in the channel. Both reaches were characterized by net erosion during the first year of restoration efforts. While erosion around the BDAs may seem counter to the long-term goal of BDA-induced aggradation, short-term net erosion is consistent with high precipitation during the study and with theoretical channel evolution models of beaver-related stream restoration that predict initial channel widening and erosion before net deposition. To better understand the impacts of BDAs on channel morphology and restoration efforts in the western United States, it is imperative that we consistently assess the effects of beaver-inspired restoration projects across a range of hydrologic and geomorphic settings and that we continue this monitoring in the future.     

Monitoring turbidity from above: Deploying small unoccupied aerial vehicles to image in‐stream turbidity

Small unoccupied aerial systems (sUASs) are increasingly applied to study hydrologic processes and water quality. Here, we evaluate a novel application of sUAS to stream turbidity monitoring, with the goal of extending analyses implemented with satellite remote sensing to enable high resolution, rapid collection of turbidity imagery along smaller waterbodies. To accomplish this, we collected multispectral imagery using two sUAS platforms under a range of environmental conditions along a local creek in Syracuse, NY. In addition, we collected in situ turbidity observations immediately after each flight along several transects along the creek, as well as within a clear plume created by a natural spring entering the main channel of the creek. The in situ turbidity values were compared with the mean and standard deviation of several single‐band and multiband indices extracted along similar transects from the sUAS flights. On the basis of data collected across several flights, we found optical metrics obtained from multispectral imagery correlated well with in situ turbidity measurements. Though many optical metrics yielded strong relationships considering only values within the main channel, values associated with the red band were strongly related to turbidity estimates from the main channel as well as lower turbidity values observed in the spring plume. Although there are still limitations of this approach associated with variable field conditions, results from this proof of concept analysis show that sUASs offer a promising avenue for cost‐effective turbidity monitoring.     

Interactions between synoptic, intraseasonal and interannual convective variability over Southern Africa

After removing the annual cycle, a principal component analysis is applied to the daily outgoing longwave radiation anomaly field, used here as a proxy for atmospheric convection. The analysis is carried out over the southern African region (7.5°E–70°E, 10°S–40°S) for austral summer (November through February) for the period 1979–1980 to 2006–2007. The first five principal components (PC) are retained. The first two PCs describe spatial patterns oriented north-west to south-east from tropical southern Africa (SA) to the mid-latitudes. They are interpreted to be different possible locations for synoptic-scale tropical–temperate troughs (TTT), one dominant rainfall-producing synoptic system in the region. The phase relationship between these two PCs describes a tendency for these TTT to propagate eastwards from SA to the Mozambique Channel and southern Madagascar. The next three PCs describe convective fluctuations, respectively, located over the north-west, the south and the centre of SA. Their time series are significantly associated with Madden–Julian oscillation (MJO) activity in the tropics. However, we find that TTT systems are statistically independent of the MJO, i.e. they are equally liable to occur during any phase of the MJO. Three PCs out of five also show a significant association with El Niño southern oscillation, confirming that El Niño years mostly coincide with suppressed convection at the intraseasonal time-scales, a result consistent with its impact on seasonal averages diagnosed in previous studies.