Field Measurements of Natural and Fertilizer-Induced N2O Release Rates from Soils

The influence of the soil on atmospheric N₂O was studied by In-situ measurements in 1976–1979 at several field stations near Mainz, Germany, where different soil types were located. Measurements were carried out using the closed chamber method and applying stainless steel capillaries allowing soil air sampling down to 60 cm depth. The N2O In soil was found to be produced and consumed simultaneously In the uppermost soil layer resulting In a net flux of N₂O with release rates of 0.5–16 μg N₂O–Nm^?2h^?1 on unfertilized natural as well as agriculturally used soils. After fertilization with mineral fertilizers the N₂O release rates increased to values ≤43 μg N₂O–Nm^?2h^?1. The total amount of fertilizer-N released Into the atmosphere as N₂O was determined to be 0.01–0.05% for nitrate and 0.03–0.09 % for ammonium fertilizer.     

Background levels of heavy metals in surficial sediments of the Gulf of Lions (NW Mediterranean): an approach based on 133Cs normalization and lead isotope measurements

This paper presents an attempt to reach natural background levels of heavy metals in surficial sediments of the Gulf of Lions (NW Mediterranean). To correct for the grain-size effect, normalization procedures based on a clay mineral indicator element are commonly used, after a first grain size separation by sieving. In our study, we tested the applicability of this method with respect to commonly used normalizer elements, and found that stable Cs shows the best ability to reflect the fine sediment fraction. Background levels were successfully reached for Co, Cr, Cu, Ni and Pb, compared to various literature references. Nevertheless, in the case of lead, the normalized data depicted a general enrichment in all samples, and the natural levels could only be reached when concentrations were corrected for the atmospheric contribution by analysing lead isotope ratios. Also for Zn, a general enrichment was found in our samples, although less important.     

Biodiversity and food security: from trade-offs to synergies

Regional Environmental Change -     

Ontogeny of fetal liver glucose-6-phosphatase activity

A reliable and sensitive microassay for the measurement of liver glucose-6-phosphatase is described. Human fetal liver was assayed for glucose-6-phosphatase activity from 7.5 to 24 weeks of gestation and was found to have a mean activity of 2.11 nmol per min per mg of protein. This was approximately 30 per cent of the postnatal controls assayed by the same method, but there was no evidence of a change in activity during the gestational period examined. If fetal liver tissue can be reliably obtained, it may be possible to determine a deficiency of glucose-6-phosphatase in fetuses who are at risk.     

Retinal cryptochrome in a migratory passerine bird: a possible transducer for the avian magnetic compass

The currently discussed model of magnetoreception in birds proposes that the direction of the magnetic field is perceived by radical-pair processes in specialized photoreceptors, with cryptochromes suggested as potential candidate molecules mediating magnetic compass information. Behavioral studies have shown that magnetic compass orientation takes place in the eye and requires light from the blue-green part of the spectrum. Cryptochromes are known to absorb in the same spectral range. Because of this we searched for cryptochrome (CRY) in the retina of European robins, Erithacus rubecula, passerine birds that migrate at night. Here, we report three individually expressed cryptochromes, eCRY1a, eCRY1b, and eCRY2. While eCRY1a and eCRY2 are similar to the cryptochromes found in the retina of the domestic chicken, eCRY1b has a unique carboxy (C)-terminal. In light of the radical-pair model, our findings support a potential role of cryptochromes as transducers for the perception of magnetic compass information in birds.     

Images of the invisible-prospection methods for the documentation of threatened archaeological sites

To understand the development of prehistoric cultural and economic activities, archaeologists try to obtain as much relevant information as possible. For this purpose, large numbers of similar sites must be identified, usually by non-destructive prospection methods such as aerial photography and geophysical prospection. Aerial archaeology is most effective in locating sites and the use of digital photogrammetry provides maps with high accuracy. For geophysical prospection mainly geomagnetic and geoelectrical methods or the ground-penetrating radar method are used. Near-surface measurements of the respective contrasts within physical properties of the archaeological structures and the surrounding material allows detailed mapping of the inner structures of the sites investigated. Applying specially developed wheeled instrumentation, high-resolution magnetic surveys can be carried out in a standard raster of 0.125Ǵ.5 m covering up to 5 ha per day. Measurements of ground resistivity or radar surveys in a raster of 0.5 or 0.5Ǵ.05 m, respectively, are used to gain information on archaeological structures and on the main stratigraphic sequence of sites covering up to 0.5 ha per day. Data on intensities of the Earth's magnetic field, apparent resistivities of the ground or amplitudinal information of radar reflections are processed using a digital image processing technique to visualize the otherwise invisible archaeological structures or monuments buried in the ground. Archaeological interpretation, in the sense of detecting, mapping and describing the archaeological structures, is done using GIS technology by combining all relevant prospection data. As most of the Middle European archaeological heritage is under a massive threat of destruction, dramatically accelerated by intensive agriculture or industrial transformation of the landscape, the prospection techniques presented here represent an approach towards an efficient documentation of the disappearing remains of our ancestors.