Studies on nematodes of dune sands

Although nematodes abound in soils little has been discovered about their role in the biology of soils. Dune sands were selected for this study since if this "relatively simple" habitat could be understood it would provide a starting point to an understanding of the vastly more complex biology of agricultural soils. It was thought that the nematode fauna in sand dunes would be depauperate, that the environmental conditions might be simple enough to be understandable, if necessary duplicable, and that their variation might explain variation in the nematode fauna. In an attempt to achieve some understanding of the nematode fauna the following points were considered:- 1. Taxonomic characterisation of the nematode fauna to species level. Although de Man (1880, 1884) described several species of nematodes from the coastal dunes of the Netherlands, the nematode fauna of this environment is poorly known. Clark (1960, 1963) and Killick (1964) have described new species from New Zealand dunes. 2. Examination of the population changes of the species in relation to season, depth and other environmental factors. The majority of population studies have concerned economically important species in agricultural soils. 3. Elucidation of trophic relationships. The trophic relationships of many nematodes are unknown or unsubstantiated. Goodey (1963) gives the essence of the knowledge of the bionomics of each genus. 4. General examination of the biology of "free living" nematodes, aided by comparison between conditions in vivo and in vitro. Because of the supposed simplicity of the biota, physics and chemistry of dune sands comparison of results obtained from cultures with those obtained in the field seem more acceptable than if species from a complex agricultural soil were used

Molecular dynamics simulation of humic substances

© 2014, Orsi. Humic substances (HS) are complex mixtures of natural organic material which are found almost everywhere in the environment, and particularly in soils, sediments, and natural water. HS play key roles in many processes of paramount importance, such as plant growth, carbon storage, and the fate of contaminants in the environment. While most of the research on HS has been traditionally carried out by conventional experimental approaches, over the past 20 years complementary investigations have emerged from the application of computer modeling and simulation techniques. This paper reviews the literature regarding computational studies of HS, with a specific focus on molecular dynamics simulations. Significant achievements, outstanding issues, and future prospects are summarized and discussed

Pilotprojekt zur Entwicklung eines allgemeingültigen Analysenschemas für organische Chemikalien im Boden

Der Umweltschutz beschäftigte sich bis zu Beginn der siebziger Jahre vor allem mit der Problematik der Luft- und Wasserverschmutzung . Dies ist insofern erklärbar, da die Auswirkungen von Luft- und Wasserverunreinigungen in unmittelbarer Umgebung des Menschen schon nach kurzer Zeit erkennbar sind. Der Schutz der Böden wurde dagegen erst mit Verspätung in Angriff genommen . Mit zunehmendem Stand der Forschung wurde deutlich, daß auch der Boden dringend des Schutzes bedarf. Wesentliche Belastungspfade sind unkrontrollierte Industriedeponien und Ablagerungen, die sogenannten Altlasten, ferner die Ausbringung von Klärschlamm in Land- und Forstwirtschaftsowie die Anwendung von Mineraldüngern mit Schadstoffverunreinigungen (z .B . Cadmium in Phosphatdüngern) dar. Die Nebenwirkungen von Pflanzenschutzmitteln im Boden wurden - wenn auch nicht ausreichend - bereits ab Mitte der sechziger Jahre beachtet. So wurde 1985 die "Bodenschutzkonzeption der Bundesregierung" verabschiedet, in der durch eine langfristig angelegte Vorsorgepolitik angestrebt wird, die Belastungen des Bodens zu vermindern und zumindest seine Funktionen unter den an ihn gestellten Nutzungsansprüchen zu schützen. Voraussetzung für einen wirksamen Bodenschutz sind verläßliche Informationsgrundlagen, um Gefährdungen lebensnotwendiger Bodenfunktionen frühzeitig zu erkennen und Veränderungen der Lebensgrundlagen für Menschen, Tiere und Pflanzen abzuschätzen. Deshalb ist ein vorrangiges Ziel die Erarbeitung flächendeckender Aussagen über Eintrag, Abbau und Verbleib von problematischen Stoffen in Böden und Grundwasser Bundestagsdrucksache 11/1625). [...

Pesticide volatilization and exposure of terrestrial ecosystems

Field experiments in cereals were carried out by herbicide and fungicide post emergence application in spring and by insecticide and fungicide treatment of barely before ripeness in summer. The pesticide concentrations in plants and soil of the target area and in the air above the field and concentrations in different distances to the treated field in front of and behind the hedge situated downwind were determined. After treatment in spring fenpropimorph occurred in the air in concentrations up to 1.3 mug/m3; parathion-ethyl reached concentrations up to 3.3 mug/m3 in the air after application in summer. The pesticide discharge in the main wind direction could be estimated assuming a pesticide transport with the average downwind wind speed and an average pesticide concentration at the field edge. While the total amounts of herbicide and fungicide discharges were low during the treatment in spring, the downwind discharge of the insecticide parathion-ethyl was 16-17 per cent of the applied amount in summer 1995. To assess the exposure of terrestrial ecosystems the pesticide uptake by standardized grass cultures and of leaves of the natural hedge situated downwind was determined. It was demonstrated that both, fenpropimorph uptake by plants after application in spring and chlorothalonil uptake by plants after application in summer resulted in high concentrations in non target plants. Here, the climatic parameters play an important role. However a significant accumulation of fenpropimorph and chlorothalonil did not take place in the grass cultures. As fenpropimorph concentrations in the target plants were low and decreased rapidly, 6-10 h after application no significant differences between the fenpropimorph concentrations in the target plants and in the grass cultures were determined