The use of terrestrial plant biomass as a parameter in the fugacity model

A new compartment, the terrestrial plant biomass, is proposed for inclusion in the fugacity model. Two possibilities of calculation have been developed and exemplified: the first considers the plant as a whole, the second takes into account foliage, trunk and roots separately.     

Exposure to polychlorinated biphenyls from an overheated transformer

A Polychlorinated Biphenyl (PCB) containing transformer released approximately 50 gallons of askarel oil. No polychlorinated dibenzofurans (PCDF) or polychlorinated dibenzodioxins (PCDD) were detected in a sample of the askarel (analytical limit of detection of 40 parts per billion per isomer group). Skin irritation, unusual tiredness, and headaches occurred in approximately 20% of the individuals at the scene of the incident. Serum PCB levels, and mean values for blood and urine tests were within normal ranges.     

Reversibility of stemflow-induced soil acidification in Swedish beech forest

Stemwater running down the trunks of beech (Fagus sylvatica L.) has an acidifying effect on soil near the stem. The deposition of acidifying substances may be two to four times higher close to the stem compared to in the stand in general. To study reversibility of soil acidification, 72 stumps of beech trees were chosen from five different year classes of felling (3, 6, 9, 14-15, 25-30), representing the years when stemflow ceased to affect the soil. The H(+) concentration (pH KCl) in the topsoil (0-5 cm) differed between the distances 10-30 cm and 230-250 cm from the stumps, the soil close to the stem being more acid. The longer the time since felling the smaller the differences in H(+) concentration became. This reduction in soil acidity amounted to ca. 50% after 15 years, and only small further changes occurred over the next ten years. This indicates that soil may not recover fully from acidification, or does so at a rather slow rate after the initial 15 years of recovery.     

Field studies of ethoprop movement and degradation in two Florida soils

Unsaturated- and saturated-zone field studies were conducted under two different agricultural conditions in Florida, U.S.A., to measure the movement and degradation of ethoprop.When ethoprop was applied to a sand soil in an orange grove located on the Florida central ridge, soil residues declined with a half-life of 13 days to near the limit of detection (0.01 μg g⁻¹ within 2 months. Ethoprop residues were generally contained in the upper 2 m of soil. Although low levels of ethoprop were found in four groundwater samples within the first 3 months after application, the cause of these isolated and transient residues could not be determined. The data show that there was no widespread plume of ethoprop residues beneath or downgradient from the treated area.On a flatwood soil on the west coast of Florida, ethoprop was incorporated into raised beds and protected by a plastic mulch in which tomatoes were grown. When the plastic mulch was present, ethoprop soil residues declined with a half-life of 40 days and were confined to the upper 0.3 m of soil. After the mulch was removed at crop harvest, the remaining ethoprop dissipated with a half-life of 12 days. Groundwater residues in excess of 1 μg L⁻¹ were confined to a single sample collected after the well had been damaged during a rototilling operation. Resides of < 1 μg L⁻¹ were present in three later samples from this well. At the sampling interval where the highest residues were detected in the damaged well, ethoprop residues of < 1 μg L⁻¹ were also found in three other wells but no residues were detected in these wells in later samples.     

Biotoxizit?tstests mit PAK Die Nodulation in der Leguminosen-Rhizobien-Symbiose als sensibler Wirkungsparameter

Im Zusammenhang mit der Umweltchemikalienprüfung und der Untersuchung und Kontrolle kontaminierter B?den besteht gro?er Bedarf an Testverfahren mit h?heren Pflanzen, die schnell, einfach und preisgünstig durchzuführen sind und bereits bestehende Testverfahren nach OECD- und BBA-Richtlinien sinnvoll erg?nzen k?nnen. Dieser Beitrag stellt einen Biotoxizit?tstest vor, der die Nodulation in der Leguminosen-Kn?llchen-Symbiose als sensiblen Wirkungsparameter für die Belastung mit polyzyklischen aromatischen Kohlenwasserstoffen (PAK) benutzt. Fremdstoff, Pflanze und Mikroorganismus werden dabei auf einer festen Matrix in Kontakt miteinander gebracht; das axenische System erlaubt die Untersuchung der Fremdstoffwirkung sowohl auf den Gesamtorganismus Pflanze, als auch auf die Interaktion von Pflanze und Mikroorganismus (Kn?llchenbildung). In Dose-Response-Versuchen zeigte sich der Wirkungsparameter Nodulation, gemessen als Anzahl Wurzelkn?llchen pro Pflanze, sensibler als andere pflanzliche Wachstumsparameter. There is great need for toxicity tests with higher plants for the investigation and monitoring of chemicals in the environment — especially for tests which are quick, easy, and inexpensive. Such tests should add to and improve current guidelines, e.g., OECD- and BBA-Guidelines. This article describes the nodulation of leguminous plants withRhizobium bacteria used in a bioassay with polycyclic aromatic hydrocarbons (PAH). Plants growing on a solid medium were exposed simultaneously to bacteria and PAH. This axenic culture system allows to observe the impact of PAH on plant growth and the interaction between plant and bacteria (nodulation). Dose-response-experiments indicated that nodulation measured as number of nodules per plant, was more sensitive to the inhibition by PAH than other plant growth parameters.