Fate of seven pesticides in an aerobic aquifer studied in column experiments

The fate of selected pesticides (bentazone, isoproturon, DNOC, MCPP, dichlorprop and 2,4-D) and a metabolite (2,6-dichlorobenzamide (BAM)) was investigated under aerobic conditions in column experiments using aquifer material and low concentrations of pesticides (approximately 25 microg/l). A solute transport model accounting for kinetic sorption and degradation was used to estimate sorption and degradation parameters. Isoproturon and DNOC were significantly retarded by sorption, whereas the retardation of the phenoxy acids (MCPP, 2,4-D and dichlorprop), BAM and bentazone was very low. After lag periods of 16-33 days for the phenoxy acids and 80 days for DNOC, these pesticides were degraded quickly with 0.-order rate constants of 1.3-2.6 microg/l/day. None of the most probable degradation products were detected.     

Mycotoxins of Aspergillus fumigatus in pure culture and in native bioaerosols from compost facilities

Exposure to secondary metabolites of airborne fungi in waste handling facilities is discussed in regard to potential toxic impacts on human health. The relevance of mycotoxins has been intensely studied in connection with contamination of food and feed. Toxic secondary metabolites are expected to be present in airborne spores, but exposure to mycotoxins in bioaerosols has not been studied sufficiently. Aspergillus fumigatus is one of the most frequent species in the air of compost plants. A wide range of secondary metabolites was found in pure cultures of freshly isolated strains of A. fumigatus. Tryptoquivaline, a compound with tremorgenic properties, and trypacidin, for which no toxic properties are described, were found in native bioaerosols in a compost facility. The highly toxic metabolites gliotoxin and verruculogen were not found in the bioaerosols.     

Identifikation der kfz-bürtigen Schadstoffbelastung mit Hilfe der Verh?ltnisse der stabilen Isotope von Kohlenstoff und Schwefel

Zusammenfassung  Reifen-, Ru?-, Motoren?l-, Asphalt-, Plastik- und Lackproben aus dem Stra?enverkehr wurden auf ihre Kohlenstoff- und Schwefel-isotopenverh?ltnisse mit dem Ziel untersucht, die Frage zu beant-worten, ob diese Isotopenverh?ltnisse als Indikatoren für die Belastungssituation und die Schadstoffquellen bei der Untersuchung von stra?ennahen B?den eingesetzt werden k?nnen. Die δ¹¹C-Werte der technischen Substrate lagen zwischen-30‰ und-18‰ relativ zum PDB-Standard, Dabei zeigte sich aufgrund der unterschiedlichen Herstellungsverfahren eine deutliche Abgrenzung der Substrate untereinander. Asphalt hatte Werte zwischen-23 und-18‰, Ru? zwischen -27 und -22‰ Die Ru?proben unterschieden sich je nach Art des verwendeten Kraftstoffs. Plastik, Lack und Motor?le zeigten ?hnliche δ¹³C-Werte, die zwischen-30 und-27‰ lagen. Reifen haben relativ konstante δ¹³C-Werte um -26‰ Der Einflu? des Stra?enverkehrs auf die δ¹³C-Werte im Stra?ensediment und in stra?ennahen B?den konnte anhand verschiedener Kohlenstoffspezies an einem Transekt an einer Landstra?e aufgezeigt werden. Ein Vergleich mit verkehrstypischen Schwermetallemissionen ergab bei einzelnen Kohlenstoffspezies einen ?hnlichen Verlauf der Schwermetallkonzentrationen und der δ¹³C-Werte. Die δ³⁴S-Werte lagen zwischen -6 und +8‰ relativ zum CDT-Standard. Eine Abgrenzung der Substrate in ihren δ¹⁴S-Werten war hierbei nicht m?glich.      

Absch?tzung der Quecksilberexposition

Zusammenfassung  Ein quecksilberkontaminierter Altstandort dient als Beispiel für eine umweltmedizinische Beurteilung der Belastung der im Umfeld wohnenden Personen durch Quecksilberimmissionen. Dabei wird die innere Exposition für sieben verschiedene Altersgruppen bezüglich der KontaktmedienBoden, Luft undNahrungsmittel anhand von konventionell festgelegten Szenarien abgesch?tzt und ein Vergleich mit den epidemiologischen Ergebnissen eines Humanmonitorings angestrebt. Die standortspezifisch und pfadspezifisch durchgeführte Expositionsabsch?tzung stützt sich auf cine Vielzahl von unterschiedlichen Probenehmern sowie auf über mehrere Jahre durchgeführte Konzentrationsmessungen in den aufnahmerelevanten Kompartimenten. Sowohl die Berechnungen als auch die epidemiologischen Untersuchungen zeigen eine leichte Erh?hung der Quecksilberexposition, gemessen an strengen Richtwerten.      

Modelling stomatal responses of spring wheat (Triticum aestivum L. cv. Turbo) to ozone and different levels of water supply

Spring wheat (Triticum aestivum L. cv. Turbo) was exposed to different levels of ozone and water supply in open-top chambers in 1991. Air was charcoal filtered (CF), non-filtered (NF) and CF plus proportional addition of ambient or twice ambient ozone (CF1, CF2). Seasonal means of O(3), taken over 24 h, were 2.3, 20.6, 17.3, and 34.5 nl litre(-1) for CF, NF, CF1 and CF2 treatments, respectively. A split-plot design was used to obtain two levels of water supply: one-half of the pots was irrigated sufficiently not to show any symptoms of drought stress; the others were exposed to low water supply and received 50% of these amounts. Using a steady-state porometer approximately 800 measurements of stomatal conductance (g(s)) were made on flag leaves from 68 to 106 days after sowing. The measurements yielded only small differences of maximum conductance between the two levels of water supply. Therefore, low water supply did not protect wheat plants against ozone injury via reduced stomatal uptake in this experiment. To describe the effects of environmental variables on the stomatal behaviour, boundary-line analysis and non-linear regression analysis were used. Besides microclimatic parameters, the ozone dose of flag leaves was introduced as an independent variable affecting stomatal aperture. A well-defined boundary line for ozone dose was found, suggesting that increasing ozone dose caused stomatal closure in wheat flag leaves. But at high ozone doses, co-acting senescence seems also responsible for the decrease in stomatal conductance. A multiplicative boundary-line model was used to predict stomatal conductance from combinations of environmental variables. In the test carried out with the measurements of stomatal conductance, the model accounted only for 40% of the variation of g(s). Generalized stomatal response patterns of the herbaceous growth form, the dependence of the variables' age and ozone dose and the lack of an important factor influencing stomatal response (water status of the plant) in the model, are suggested as explanations of the poor results of the test.     

Einsatz der Hasse-Diagrammtechnik zur vergleichenden Datenanalyse von Biomarkerantworten und ?kotoxikologischen Tests

Die ?kotoxikologie mu? sich mit biologischen Systemen und ihren Antworten auf schadstoffinduzierten Stre? auseinandersetzen. Die hierzu verwendete experimentelle Technik eilt dabei den M?glichkeiten dynamischer, proze?orientierter mathematischer Modellierung weit voraus. In dieser methodisch orientierten Arbeit werden Techniken aus der mathematischen Disziplin der Verbandstheorie vorgestellt, die eine Datenanalyse unter den Aspekten vergleichender Bewertung erlauben. Wichtige Ergebnisse sind dabei

?kotoxikologische Risikoanalyse der Cadmium-Belastung im Ackerboden der Industrieregion Leipzig-Halle

Die Cadmium-Belastung im Ackerboden der Region Leipzig-Halle wurde an 63 terrestrischen Standorten über einer Fl?che von etwa 7 000 km² bestimmt. Die Verteilung der durch Normierung auf einheitlichen Gehalt an Ton und organischem Material erhaltenen effektiven Expositionswerte wurde mit Literaturangaben über NOEC-Werte verglichen. Die Risikoanalyse ergibt, da? an 9% der untersuchten Standorte eine potentielle Gef?hrdung der Bodenorganismen durch Cadmium vorliegt. Cadmium contamination in the agricultural soil of the region Leipzig-Halle was determined at 63 sites covering an area of ca. 7 000 km². Normalization according to lutum and organic matter lead to effective exposure values; their distribution was compared with NOEC data taken from literature. The risk analysis reveals that the soil fauna is potentially affected by cadmium contamination at 9% of the investigated sites.     

Determination of microbial activity in activated sewage sludge by dimethyl sulphoxide reduction

A method was developed to determine the dimethyl sulphoxide (DMSO) reduction rate in activated sewage sludge at nearly natural conditions. Linearity of microbially produced dimethyl sulphide with incubation time and sample size was shown. Apart from a fast, sensitive and highly reproducible automatic analysis of dimethyl sulphide, simultaneous determination of mineralisation, respiration and phenol degradation rates was possible. The DMSO reduction rate of samples taken from a municipal sewage plant ranged between 2 and 3 μmol/(g dry matter · h), respiration and mineralisation rates between 30 and 80 μmol/(g · h). Added¹³C₆-phenol was completely degradated after 96 h of incubation. A half-life of 14 h was calculated assuming first order decay. Dose response curves were obtained by incubating samples for 2, 6, 25, and 96 hours after addition of pentachlorophenol. At an incubation time of 6 h, the EC₅₀ values ranged from 20 mg/L (DMSO reduction) to 30 mg/L (phenol degradation) up to 180 mg/L (respiration and mineralisation). Increasing the incubation time to 96 h resulted in a lower EC₅₀ of 9 mg/L for DMSO reduction, whereas it increased to 500 mg/L for respiration and mineralisation.     

The SeKT joint research project: definition of reference conditions, control sediments and toxicity thresholds for limnic sediment contact tests

- In current biotest approaches, intact organisms or in vitro systems are exposed to sediments using different exposure scenarios. The most important issue in sediment toxicity testing protocols is the question which test phase (solid or liquid) should be used. Whole-sediment exposure protocols represent the most realistic scenario to simulate in situ exposure conditions in the laboratory. However, until now there is no agreement in how to acquire and to evaluate the data of the various available sediment contact assays. The SeKT joint research project was initiated with the aim to compare recently developed sediment contact assays by addressing reference conditions, control sediments and toxicity thresholds for limnic sediment contact tests.