Leaf and fruit necroses associated with vanadium-rich ash emitted from a power plant burning fossil fuel

Necrotic brown lesions developing on leaves and fruits of lemon, and other plants, near fossil-fuel-burning power plants emitting vanadium-rich ash, were reproduced experimentally by inoculating leaves with this type of ash, which is strongly acidic. Comparable lesions were formed when drops of vanadium oxide, dissolved in NaOH, were put on leaves and fruits. Neutralizing, or adding excess H₂SO₄ (to pH 3), did not alter lesion formation. The histology of these lesions was similar to that of lesions attributed to vanadium-rich ash.     

Humic fractions of organic wastes

The distribution and composition of humic and fulvic acids have been investigated in the following organic wastes: straw, farmyard manure, sewage sludge, poultry manure, municipal refuse compost and pig slurry. Of the total organic carbon, the proportion present as humic carbon varied from about 13% in the compost to 50% in the pig slurry; the humic compounds extracted are characterized by a variable chemical composition. As compared to the natural humic substances from soil organic matter, these compounds show a lower content of acidic functional groups, lower E₄/E₆ and C/H ratios and can be classified as young forms of humic substances.     

Do the earth's magnetic poles move?

Two distinct types of motion are commonly attributed to the geomagnetic poles — polar wander and dipole wobble. But two or three decades of intensive effort have failed to provide a sound understanding of either. Why? Polar wander is a very slow phenomenon associated with time scales of 10⁷ to 10⁸ years and thus intimately connected with the drift of the continents arising from plate tectonics. While there is no question of the validity of relative movements between the continents and the pole, the possibility of independent polar motion remains debatable. Dipole wobble is a more rapid phenomenon, most likely associated with time scales of 10⁶ years or less. Currently the geomagnetic axis diverges from the Earth's spin axis by 11 1/2°, but paleomagnetic data indicate that, when averaged over a million years or so, the two coincide. Dipole wobble is the supposed mechanism responsible. The main difficulty here is one of isolating any dipole effects from perturbations of similar magnitude arising from the non-dipole fraction of the geomagnetic field — the so-called secular variation. Recent studies have significantly advanced our understanding of the secular variation, but the dipole wobble remains enigmatic.     

Latest precambrian (Cadomian) zircon ages, Nd isotopic systematics and P-T evolution of granitoid orthogneisses of the Erzgebirge, Saxony and Czech Republic

Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a ²⁰⁷Pb/²⁰⁶Pb emplacement age of 550±7 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean ²⁰⁷Pb/²⁰⁶Pb age of 555±7 Ma as well as xenocrysts ranging in age between 850 and 1910 Ma. Red gneisses from the central Erzgebirge contain complex zircon populations, including numerous xenocrysts up to 2464 Ma in age. The youngest, idiomorphic, zircons in all samples yielded uniform ²⁰⁷Pb/²⁰⁶Pb ages between 550±9 and 554±10 Ma. Nd isotopic data support the interpretation of crustal anatexis for the origin of both units. _Nd(t) values for the grey gneisses are –7.5 and –6.0 respectively, (mean crustal residence ages of 1.7–1.8 Ga). The red gneisses have a wider range in _Nd(t) values from –7.7 to –2.8 (T _DM ages of 1.4–1.8 Ga). The zircon ages document a distinct late Proterozoic phase of granitoid magmatism, similar in age to granitoids in the Lusatian block farther north-east. However, Palaeozoic deformation as well as medium pressure metamorphism ( 8 kbar/600–650° C) are identical in both gneiss units and distinguish these rocks from the Lusatian granitoids. The grey and red gneisses were overthrust by units with abundant high-pressure relicts and a contrasting P-T evolution. Zircon xenocryst and Nd model ages in the range 1000–1700 Ma are similar to those in granitoid rocks of Lusatia and the West-Sudetes, and document a pre-Cadomian basement in parts of east-central Europe that, chronologically, has similarities with the Sveconorwegian domain in the Baltic Shield.