Publikationsserver der RWTH Aachen University
Einfluss von Mikroorganismen und Organo-Ton-Komplexe auf die Bildung von nicht-extrahierbaren Rückständen im Boden unter Verwendung von 14 C-Nonylphenol und 14 C-MCPA als Modellsubstanzen
Abstract
dc:descriptionThe aim of this study was to measure the effect of microorganisms and organo-clay complexes on the formation of non-extractable residues (NER) of soil. For the purpose of these investigations two test chemicals, 4(3’,5’-dimethyl-3’-heptyl)-phenol (p353-NP) and 2-methyl-4-chlorophenoxyacetic acid (MCPA), were used. To understand the fate and behavior of the used test substances, as well as their breakdown products in soil and within the clay fraction of the soil, they were applied as 14C compounds. The use of sterilized soil allowed excluding biotic factors that can have an influence on the formation of NERs. In addition, all soil samples were subjected to a particle size fractionation, in order to study the relevance of the clay fraction and thus the organo-clay complexes for the formation of NER. The results show that, irrespective of the test substance, an elimination of microbial activity by sterilization of the soil caused a significantly higher portion of extractable radioactivity of the clay fraction than in the non-sterilized approaches. This provides supportive evidence for the important role of microorganisms in the formation of NER. In the case of MCPA, the influence of microbial activity on the extractability of radioactivity could also be shown for the non-sterilized approaches. MCPA, with a concentration of 1 mg / g soil, showed a toxic effect on microbial activity, which was reduced significantly compared to the lower concentration (8,42 μg/g). In return, the amount of extractable radioactivity in the clay fraction increased significantly. Subsequently, the microbial activity increased by adaptation, and the portions of extractable radioactivity in the clay fraction decreased. In all approaches with non-sterilized soil the radioactivity extractable from clay fractions decreased with increasing test duration. For both compounds (p353-NP and MCPA) the model of Barraclough et al. can be used to explain the results. According to this model MCPA can probably be classified as an organic compound which shows a rapid decline in the concentration of the parent compound and its metabolites, while at the same time exhibiting a high mineralization. These compounds have the tendency to form lower amounts of NER. p353-NP on the other hand, can probably be classified as a compound with a moderate or slow decline of the parent compound’s concentration and a comparatively low mineralization of the applicable metabolites. These compounds have the tendency to form more significant amounts of NER. By comparing the results of the approaches with sterile and non-sterile soil, the importance of organic carbon in soil for the formation of NER can be shown. In the sand fractions of the sterile p353-NP and MCPA approaches less than 6% of the radioactivity applied could be found. This fraction contained less than 2.10% organic carbon. For both chemicals in question the results of the approaches with sterilized soil differ from those with non-sterilized soil. In case of sterilized soil the sand fraction contained more than 11% organic carbon and more than 40% of the applied radioactivity after 30 days. The influence of the test substances on the microbial diversity of the incubated soils was studied by denaturing gradient gel electrophoresis (DGGE). In the present study an effect of the test substances on bacterial diversity could be detected. On the contrary, the used concentrations of the test substances had no effect on the fungi diversity. CP-MAS NMR (charge polarized magic angle spinning nuclear magnetic resonance) measurements showed that the aromatic ring of p353-NP was probably installed partially in an intact form in the humic acids. 13C-p353-NP was labeled at the phenolic C1 position of the aromatic ring. By sampling MCPA and p353-NP, this paper provides a valuable contribution to answering several questions about the disposition of xenobiotics in soil and the formation of NER. Here, the soil not only acts as a location for higher plants, but also as a filter, cleaning, transportation, buffer and storage system for xenobiotics. Simultaneously, the ground also serves as the location of economic plants such as corn, wheat, potatoes, etc. For this reason, it is of great interest to learn more about the behavior and fate of xenobiotics to find out in the ground to potential hazards such as assess the application of plant protection products and sewage sludge well. The results of this work demonstrate that microorganisms have an important role in the formation of NER. Moreover, evidence is provided that the organo-clay complexes are an important source for binding the test chemicals compared to the silt and sand fraction. In the NMR study of the NER humic acid of p353-NP approach it has been shown that aromatic rings of p353-NP in intact form were incorporated into the humic acid.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2011
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Klausmeyer, Timm
- Contributors dc:contributor
-
- Schäffer, Andreas
Subjects
dc:subject × 10Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger