Influence of Temporal Variations in River Discharge, pH, Alkalinity and Ca on the Speciation and Concentration of Heavy Metals in Some Mining Polluted Rivers

Dissolved (dialysis in situ) and total concentrations ofCu, Zn, Cd and Al in eight mining polluted rivers in the Røros area, central Norway, were determinedby atomic absorption spectrometry (flame and graphite furnace) and compared to pH, Caconcentration and alkalinity through seasonal variations in river discharge. Totalconcentrations of the metals were highest during early spring flood and during summer andautumn rain episodes. Dissolved concentrations also increased as the spring floodproceeded, but small discharge peaks within this 2 month period as well as a considerableautumn flood episode appeared to lower rather than to raise the dissolved metal concentrations.Consequently the dissolved fractions of Zn, Cd and Al showed a significant negative correlationwith river discharge, and were low at the discharge peaks. Possibly high sediment concentrationsoccurring at high flood conditions more than counteracted desorption induced by pHdecrease, and led to decreased dissolved fractions through adsorption. Cu speciationon the other hand seemed to be more closely linked to pH. Alkalinity and Ca concentration,both assumed to protect aquatic life from metal pollution, were significantly lowerduring episodes with high Cu and Al total concentrations.     

Simulations of strong ground motion in SW Iberia for the 1969 February 28 (Ms= 8.0) and the 1755 November 1 (M∼ 8.5) earthquakes – II. Strong ground motion simulations

This is the second paper of a series of two concerning strong ground motion in SW Iberia due to earthquakes originating from the adjacent Atlantic area. The aim of this paper is to use the velocity model that was proposed and validated in the companion paper for seismic intensity modelling of the 1969 ( M _s= 8.0) and 1755 ( M = 8.5–8.7) earthquakes.
First, we propose a regression to convert simulated values of Peak Ground Velocity (PGV) into Modified Mercalli Intensity (MMI) in SW Iberia, and using this regression, we build synthetic isoseismal maps for a large ( M _s= 8.0) earthquake that occurred in 1969. Based on information on the seismic source provided by various authors, we show that the velocity model effectively reproduces macroseismic observations in the whole region. We also confirm that seismic intensity distribution is very sensitive to a small number of source parameters: rupture directivity, fault strike and fault dimensions. Then, we extrapolate the method to the case of the great ( M = 8.5–8.7) 1755 earthquake, for a series of hypotheses recently proposed by three authors about the location of the epicentral region. The model involving a subduction-related rupture in the Gulf of Cádiz results in excessive ground motion in northern Morocco, suggesting that the source of the 1755 earthquake should be located further west. A rupture along the western coast of Portugal, compatible with an activation of the passive western Iberian margin, would imply a relatively low average slip, which, alone, would could not account for the large tsunami observed in the whole northern Atlantic ocean. A seismic source located below the Gorringe Bank seems the most likely since it is more efficient in reproducing the distribution of high intensities in SW Iberia due to the 1755 earthquake.     

Remanent magnetism of anorganic and organic substances and its exploitation in treating historical problems

Summary Properties of the thermoremanent magnetization of various archaeological materials (baked-clay objects, samples from old trees, bones and stones) were investigated with the purpose to assess the possibility of their use for the determination of the earth's magnetic field in the historical past and to apply the data for solving some practical problems. It turns out that most of those materials yield magnetic values that can be used for making the radiocarbon dating method more accurate, for determining the degree of burning and for direct archaeomagnetic dating. The new conclusions also contribute to the knowledge of changes in the earth's magnetic field in the past.     

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Hans Benndorf †

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Hans Benndorf

     

Multi-wavelength observations of the onset phase of a coronal mass ejection

The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the emergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the time of the flare. Yohkoh images, taken about 15 min later, show that this cavity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an H surge or small filament eruption occurs about 50 arc sec northwards along the limb from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected by hot loops near their bases. Both jets disappear within a few minutes of one another.Clear evidence of the CME first appeared in the Large Angle Spectrometric Coronagraph (LASCO) and EIT images 40 min after the flare and onset of the filament ejection. It seems to come from a region between the two X-ray jets. This leads to the speculation that magnetic field reconnection near one footpoint of a loop system triggers reconnection near its other footpoint. The loop system is destabilized and ultimately gives rise to the CME. This possibility is supported by magnetic field and H images taken when the active region was at disk center which show that the active region had a double bipole structure with dark H filaments between the bipoles.