Untersuchungen des atmosphaerischen Eintrags polychlorierter Dibenzo-p-dioxine und Dibenzofurane in Futterpflanzen. T. 1 Textband. Abschlussbericht

Fuer die Exposition des Menschen gegenueber PCDD/F spielt die landwirtschaftliche Nahrungskette 'Atmosphaere - Futterpflanze - Kuh -Milch/Rindfleisch - Mensch' die entscheidende Rolle. Das uebergreifende Ziel dieses Vorhabens war die Erstellung einer quantitativen Beziehung zwischen der Immissionsbelastung mit PCDDF/F und Futtermittelkonzentrationen. Die Identifizierung der wichtigsten atmosphaerischen Eintragswege von PCDD/F in Gruenlandpflanzen wurde unter naturnahen Bedingungen im Rahmen eines kombinierten Gewaechshaus-Freilandversuches durchgefuehrt. Es wurde deutlich, dass fuer die Cl_4_-_6DD/F die trockene gasfoermige und fuer die Cl_7_/_8DD/F die trockene partikelgebundene Deposition der Hauptaufnahmepfad ist. Aus einem weiteren Gewaechshausversuch ergaben sich deutliche Hinweise auf einen isomerenunspezifischen Photoabbau von PCDD/F auf Pflanzenoberflaechen. Die trockene gasfoermige Deposition, die den Haupteintragsweg fuer die niederchlorierten toxikologisch relevanten PCDD/F darstellt, kann als Verteilung einer Verbindung zwischen der Gasphase der Atmosphaere und der Vegetation angesehen werden. Es wurde eine Reihe von Laborversuchen mit PCT, die als Modellverbindungen fuer die PCDD/F dienten, durchgefuehrt. Es konnten wichtige Erkenntnisse hinsichtlich der Pflanzen/Luft-Verteilung, ihrer Abhaengigkeit von Temperatur und Pflanzenart, ihrer Kinetik und Reversibilitaet gewonnen werden. Fuer die PCDD/F konnte keine Gleichgewichtseinstellung zwischen Pflanze und Atmosphaere beobachtet werden. Die Anreicherung von PCDD/F in Futtermitteln wird folglich durch eine gasfoermige Depositionsgeschwindigkeit bestimmt. An zwei fuer Deutschland typischen landwirtschaftlichen Standorten wurden repraesentative gasfoermige und, analog dazu, partikelgebundene Depositionsgeschwindigkeiten gemessen, die insgesamt unabhaengig von den Standortbedingungen eine relativ geringe Variationsbreite aufwiesen. Die zahlreichen Teilergebnisse dieses Forschungsvorhabens wurden in ein mathematisches Modell der Anreicherung von PCDD/F und PCB in Gruenland integriert. Auf der Basis von Luftbelastung, Artenzusammensetzung und Wachstum des Bestandes, Temperatur und Substanzeigenschaften berechnet dieses Modell die Konzentration einer Verbindung im Gruenlandaufwuchs als Funktion der Zeit. Eine Modellvalidierung konnte fuer die niederchlorierten PCB die gute Uebertragbarkeit der Laborversuche zur Pflanzen/Luft/Verteilung und der entsprechenden Modellkomponenten zeigen. Durch dieses Modell konnten die Teilergebnisse dieses Vorhabens zu einer sinnvollen Einheit zusammengefasst und somit ein wertvolles Werkzeug zum Verstaendnis der Anreicherung von mittelfluechtigen lipophilen organischen Verbindungen in landwirtschaftlichen Nutzpflanzen geschaffen werden. (orig.)Introduction of PCDD/Fs into the agricultural food chain 'atmosphere -fodder - cattle - cows' milk/beef - human' plays a major role in human exposure. The aim of this study was to establish a quantitative relationship between PCDD/Fs immissions and fodder concentrations. The identification of the most important atmospheric pathway of PCDD/F into greenland cultures was conducted under near natural conditions in a combined field/glasshouse experiment. It was found that for the Cl_4_-_6DD/Fs dry gaseous and for the Cl_7_/_8DD/Fs dry particle-bound deposition was the primary mechanism of uptake. A further greenhouse experiment showed that there is an isomere-unspecific photodegradation of PCDD/Fs on plant surfaces. Dry gaseous deposition, which is the major pathway of atmospheric deposition for the less chlorinated toxicological relevant PCDD/Fs, can be understood as a partitioning process between the gas phase of the atmosphere and the vegetation. Experiments investigating this topic were conducted in the laboratory using PCBs as model substances for the PCDD/Fs. Important knowledge was gained with regard to plant/air partitioning, their dependence on temperature and plant species, the kinetics and reversibility of the process. No partitioning equilibrium between the vegetation and the gas phase of the atmosphere was approached for the PCDD/Fs. The accumulation of PCDD/Fs in agricultural greenland was therefore controlled by a gaseous deposition velocity. In two typical German agricultural regions representative gaseous and particle-bound deposition velocities were determined, which were all in all quite constant and independent of the different exposure conditions. All results from this study were incorporated into a mathematical model of the accumulation of PCDD/Fs and PCBs in greenland. Based on air concentration, plant species composition and growth, temperature and physical-chemical properties of the chemical the model is able to predict the concentration of a chemical in the plants as a function of time. A validation of this model for the less chlorinated PCBs showed, that the measured plant/air-partitioning and the corresponding components of the model can be extrapolated to environmental conditions. This model summarizes the results of this study and provides a valuable tool in understanding the enrichment of semivolatile lipophilic organic compounds in agricultural plants. (orig.)Available from TIB Hannover: F98B1421+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Untersuchungen des atmosphaerischen Eintrags polychlorierter Dibenzo-p-dioxine und Dibenzofurane in Futterpflanzen. T. 2 Anhang. Abschlussbericht

Introduction of PCDD/Fs into the agricultural food chain 'atmosphere -fodder - cattle - cows' milk/beef - human' plays a major role in human exposure. The aim of this study was to establish a quantitative relationship between PCDD/Fs immissions and fodder concentrations. The identification of the most important atmospheric pathway of PCDD/F into greenland cultures was conducted under near natural conditions in a combined field/glasshouse experiment. It was found that for the Cl_4_-_6DD/Fs dry gaseous and for the Cl_7_/_8DD/Fs dry particle-bound deposition was the primary mechanism of uptake. A further greenhouse experiment showed that there is an isomere-unspecific photodegradation of PCDD/Fs on plant surfaces. Dry gaseous deposition, which is the major pathway of atmospheric deposition for the less chlorinated toxicological relevant PCDD/Fs, can be understood as a partitioning process between the gas phase of the atmosphere and the vegetation. Experiments investigating this topic were conducted in the laboratory using PCBs as model substances for the PCDD/Fs. Important knowledge was gained with regard to plant/air partitioning, their dependence on temperature and plant species, the kinetics and reversibility of the process. No partitioning equilibrium between the vegetation and the gas phase of the atmosphere was approached for the PCDD/Fs. The accumulation of PCDD/Fs in agricultural greenland was therefore controlled by a gaseous deposition velocity. In two typical German agricultural regions representative gaseous and particle-bound deposition velocities were determined, which were all in all quite constant and independent of the different exposure conditions. All results from this study were incorporated into a mathematical model of the accumulation of PCDD/Fs and PCBs in greenland. Based on air concentration, plant species composition and growth, temperature and physical-chemical properties of the chemical the model is able to predict the concentration of a chemical in the plants as a function of time. A validation of this model for the less chlorinated PCBs showed, that the measured plant/air-partitioning and the corresponding components of the model can be extrapolated to environmental conditions. This model summarizes the results of this study and provides a valuable tool in understanding the enrichment of semivolatile lipophilic organic compounds in agricultural plants. (orig.)SIGLEAvailable from TIB Hannover: F98B1422+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Derivation and field testing of air-milk and feed-milk transfer factors for PCBs.

Detailed field experimental data on the air to herbage transfer of PCBs was combined with data on feed to milk transfers from a detailed feeding trial with lactating cows to derive congener-specific air to milk and feed to milk transfer factors (TFA:M and TFF:M). The variability and uncertainties in these factors are discussed largely with reference to UK field conditions. TFA:M values were 2.4, 54, and 650 m3 of air g-1 of milk fat for congeners 18, 74, and 170, respectively. The usefulness of the transfer factors as predictive tools was tested on (i) data from two milk and feed surveys (in late spring 1996 and winter 1997) of farms in Northwest England; (ii) data from a long-term monitoring study conducted throughout the 1996 growing season; and (iii) data from the literature. TFA:M and TFF:M gave excellent predictions of the milk PCB concentrations for all tested data sets, with milk concentrations of the persistent congeners predicted to within a factor of 2−3 at the local level and to well within an order of magnitude at the regional level. The main requirements of using TFA:M are that (i) pasture is the dominant feed; (ii) winter-fed silage is grown locally, and (iii) there is no local intermittent source. Survey results showed that levels of persistent PCB congeners in silage are directly correlated with milk output fluxes. Bioconcentration factors (BCFs) and carry-over rates (CORs) calculated for both study approaches were very similar to those found in “uncontaminated” feeding studies. Although CORs are theoretically preferable to BCFs the variability found for each showed that there is likely to be little practical advantage in collecting the extra data required for the calculation of CORs

Modeling the plant uptake of organic chemicals, including the soil-air-plant pathway

The soil−air−plant pathway is potentially important in the vegetative accumulation of organic pollutants from contaminated soils. While a number of qualitative frameworks exist for the prediction of plant accumulation of organic chemicals by this pathway, there are few quantitative models that incorporate this pathway. The aim of the present study was to produce a model that included this pathway and could quantify its contribution to the total plant contamination for a range of organic pollutants. A new model was developed from three submodels for the processes controlling plant contamination via this pathway: aerial deposition, soil volatilization, and systemic translocation. Using the combined model, the soil−air−plant pathway was predicted to account for a significant proportion of the total shoot contamination for those compounds with log KOA > 9 and log KAW −3 there was a higher deposition of pollutant via the soil−air−plant pathway than for those chemicals with log KOA > 9 and log KAW 100 mg kg−1