Sorption and degradation of pesticides in biopurification systems

The increasing use of pesticides in agriculture has given rise to a situation in which countries now have to cope with the problem of residues of these compounds in ground and surface water. 40-90% of surface water contamination is caused by direct losses (e.g. spills during filling operations, leakages of spray equipment, spray leftovers, etc.). Considering the cost of treating water to remove pesticides, contamination should be treated at the source, thus on-farm before discharging. On-farm biopurification systems, developed to treat pesticide contaminated water, consist of a biologically active matrix that retains pesticides into the organic matter and enhances their biodegradation. In order to optimize the efficiency of these systems, the fate of pesticides and the contribution of degradation and retention process needs to be well characterized. In the present work, the intention was to unravel sorption and degradation processes on an increasing spatial scale. The first part of this thesis focused on the sorption of pesticides. The sorption strength of the pesticides appeared to be positively correlated to the Koc-value of the pesticide. Quantification of the sorption capacity with the Freundlich equation led to the following ranking with increasing sorption capacity: sandy loam soil < willow chopping, cow manure < straw, coco chips, compost < peat mix. Finally, it could be observed that the sorption capacity was in this case strongly correlated with the organic carbon content, CaO content and the cation exchange capacity. The second and major part of this thesis was performed with column experiments, thus incorporating transport of pesticides. Sorption and degradation characteristics of linuron, bentazone, metalaxyl and isoproturon were quantified using inverse modeling techniques present in the transport model HYDRUS-1D. The sorption strength of the different pesticides to the organic matrix, increased with decreasing mobility of the pesticides. Concerning increasing degradability of the pesticides, pesticides could be ranked as follows linuron > metalaxyl-isoproturon > bentazone. Delayed degradation could be observed for some pesticides in the micro- and macrocosms and could be fitted by implementing the Monod kinetics into HYDRUS-1D. Moreover, a column study was performed, where metalaxyl or isoproturon primed material was included in the matrix and transport of both pesticides was followed-up. Increased degradation in the presence of metalaxyl primed material was obtained, in contrast to isoproturon. The last part of the studies performed in column experiments were carried out to gain some knowledge on the influence of a variable flux on pesticide degradation and retention. Sorption of pesticides decreased considerably with increasing flux. Degradation of the pesticides was also significantly influenced by the flow in the microcosms. Finally, we explored two strategies to reduce the amount of pesticide residues in the organic matrix after use. Contaminated matrix (bifenthrin, linuron, metalaxyl and bentazone) was treated in an industrial composting plant and in barrel incubation. A decrease in certain pesticide concentrations could be observed in both processes. A removal in extractable pesticide concentration does however not always indicate degradation but could also be attributed to the formation of bound residues. Thus, it could be stated that the treatment of the matrix with the proposed composting process does not offer a decisive solution. In conclusion, the results reported in this thesis have provided insight in the degradation and sorption processes occurring inside the biopurification matrix. These results can be used in future studies to further elaborate the behavior of other pesticides in biopurification systems and to formulate some guidelines for the use of a biopurification system.

Grantor dc:publisher

Ghent University. Faculty of Bioscience Engineering

Year dc:date

2009

Author dc:creator

• De Wilde, Tineke

Contributors dc:contributor

• Steurbaut, Walter

• Agriculture and Food Sciences
• sorption
• contamination
• degradation
• Biopurification system
• pesticide
• organic matrix

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://biblio.ugent.be/publication/708472
urn:isbn:978-90-5989-297-2
https://biblio.ugent.be/publication/708472/file/4334977

OAI identifier oai:identifier

oai:archive.ugent.be:708472