Wehrhan, Anne: Fate of veterinary pharmaceuticals in soil : An experimental and numerical study on the mobility, sorption and transformation of sulfadiazine. - Bonn, 2006. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5N-08951
@phdthesis{handle:20.500.11811/2387,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5N-08951,
author = {{Anne Wehrhan}},
title = {Fate of veterinary pharmaceuticals in soil : An experimental and numerical study on the mobility, sorption and transformation of sulfadiazine},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2006,
note = {Among other sulfonamides sulfadiazine (SDZ) is a widely used antimicrobial substance in intensive livestock production to prevent and treat diseases. Up to 40 % of the administered sulfonamides are eliminated as microbial active substances with the excretions. Antibiotics reach agricultural soils directly through grazing livestock or indirectly through the spreading of manure or sewage sludge on the field. Knowledge about the fate of antibiotics in soil is crucial to assess the environmental risk of these compounds, including possible transport to groundwater. Sorption, transport and transformation of 14C-labelled SDZ in a silty loam were investigated using batch-type and column experiments.
The batch sorption/desorption experiments were conducted at various concentration levels (0.044 to 13 mg L-1 initial solute concentration) and time-scales (0.75 to 272 days). Sorption of SDZ in the investigated soil was time-dependent and strongly non-linear with regard to the concentration. The time to reach apparent sorption equilibrium was about 20 days. However, 41 days were insufficient to reach the desorption equilibrium.
Transport of 14C-labelled SDZ was investigated in disturbed soil columns at a constant flow rate (0.26 cm h-1) near saturation. 14C-SDZ was applied in different concentrations (0.57 or 5.7 mg L-1) for either short or long pulse duration (7 or 70 hours). Breakthrough curves (BTCs) of 14C-SDZ and the non-reactive tracer chloride were measured. At the end of the leaching period the soil concentration profiles were determined. The decreasing limbs of all BTCs are characterized by an extended tailing. The eluted mass fractions varied from 18 to 83 % after 500 hours of leaching.
Inverse modeling techniques were used to identify relevant sorption processes of SDZ and its transformation products during the batch and column experiments. A three-site sorption model that exhibits fast and slow equilibrium sorption as well as irreversible sorption was required for the description of the batch and transport experiments. Despite the high flexibility of the proposed model concept, the description of the soil concentration profiles in the soil columns failed. The optimal parameter set differed among the three transport experiments and were also different from the set describing the sorption experiments best.
In soil-water systems SDZ was transformed into N4-acetylsulfadiazine, hydroxysulfadiazine and an unidentified, polar transformation product. In the peak of the BTCs, 12 to 43 % of the leached radioactivity was composed of the transformation products.
A model that considers reversible and irreversible kinetic sorption of SDZ with subsequent transformation of the reversibly bound species into a reversibly sorbing transformation product was able to describe the characteristic features of the BTCs and soil concentrations profiles. However, BTCs and soil concentration profiles could not be described simultaneously. Despite this incomplete process description, the obtained results are relevant to assess the transport behavior of sulfadiazine in the field.},

url = {http://hdl.handle.net/20.500.11811/2387}
}

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