Stephan Sittig - Academia.edu (original) (raw)

Papers by Stephan Sittig

Research paper thumbnail of Runoff mitigation via micro‐dams and conservation tillage – numerical modelling of runoff and erosion from maize field trials

Integrated Environmental Assessment and Management

Research paper thumbnail of Long-term batch study of sorption, transformation and extractability to characterize the fate of the veterinary antibiotic sulfadiazine

The occurrence of veterinary antibiotic substances in various environmental compartments is of gr... more The occurrence of veterinary antibiotic substances in various environmental compartments is of growing concern. Once released into the environment (e.g. via manure), these organic substances can cause changes in the composition of microbial populations, provoke the development and spreading of resistance genes and finally reach the food chain. The substance under study is the veterinary antibiotic sulfadiazine (SDZ), which belongs

Research paper thumbnail of Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations

Journal of contaminant hydrology, Jan 14, 2015

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegrad... more Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, th...

Research paper thumbnail of Long-Term Sorption and Sequestration Dynamics of the Antibiotic Sulfadiazine: A Batch Study

Journal of Environment Quality, 2012

Understanding the long-term sequestration of veterinary antibiotics into soil fractions with diff... more Understanding the long-term sequestration of veterinary antibiotics into soil fractions with diff erent bioavailability is important in terms of assessing their eco-toxicological impact. We performed 60-d batch sorption experiments with radiolabeled sulfadiazine (SDZ) using samples from two agricultural soils. Sequential extraction with CaCl 2 /MeOH (easily accessible fraction), microwave (residual fraction, RES), and combustion (nonextractable residues, NER) was used to quantify the sequestration dynamics of the 14 C-derived SDZ-equivalent concentration. Multiple harsh extractions allowed us to mathematically extrapolate to the amount of SDZ equivalents that can be potentially extracted, resulting in halving the NER fraction aft er 60 d. A modifi ed two-stage model with irreversible sorption combined with global parameter optimization was able to display the sequestration dynamics. We demonstrated this with sterilized samples in which no transformation of the parent compound was observed. Th is also showed that transformation was primarily biologically driven. Th ese modeling results verifi ed the procedure, which was then applied to nontreated samples from both soils to estimate eff ective parameter values for SDZ-derived equivalents. Observed initial sorption, to which up to 20% of the kinetic sorption sites attributed, was included in the model. Both the RES and NER fractions reached a sorption plateau, with NER occupying about 30% of the kinetic fraction (RES+NER) for all soils. Th e sorption and sequestration of SDZ were soil-specifi c and dominated by kinetics. Sequestration in the RES fraction was much slower (characteristic time: 60 d) than the redistribution in the NER fraction (characteristic time: <6 d). Th e work presented here contributes to the prediction of the dynamics of (bio-)availability.

Research paper thumbnail of Dynamics of transformation of the veterinary antibiotic sulfadiazine in two soils

Chemosphere, 2014

We show transformation and sequestration of the antibiotic sulfadiazine in two soils. Transformat... more We show transformation and sequestration of the antibiotic sulfadiazine in two soils. Transformation products were found in liquid phase and extracts from the sorbed phase. We used a compartment model including all species and did global optimization. Sorption and transformation are concentration dependent.

Research paper thumbnail of Laboratory transport experiments with antibiotic sulfadiazine: Experimental results and parameter uncertainty analysis

AGU Fall Meeting Abstracts, Dec 1, 2011

Persistent antibiotics in the soil potentially contaminate the groundwater and affect the quality... more Persistent antibiotics in the soil potentially contaminate the groundwater and affect the quality of drinking water. To improve our understanding of antibiotic transport in soils, we performed laboratory transport experiments in soil columns under constant irrigation conditions with repeated applications of chloride and radio-labeled SDZ. The tracers were incorporated in the first centimeter, either with pig manure or with solution. Breakthrough curves and concentration profiles of the parent compound and the main transformation ...

Research paper thumbnail of Runoff mitigation via micro‐dams and conservation tillage – numerical modelling of runoff and erosion from maize field trials

Integrated Environmental Assessment and Management

Research paper thumbnail of Long-term batch study of sorption, transformation and extractability to characterize the fate of the veterinary antibiotic sulfadiazine

The occurrence of veterinary antibiotic substances in various environmental compartments is of gr... more The occurrence of veterinary antibiotic substances in various environmental compartments is of growing concern. Once released into the environment (e.g. via manure), these organic substances can cause changes in the composition of microbial populations, provoke the development and spreading of resistance genes and finally reach the food chain. The substance under study is the veterinary antibiotic sulfadiazine (SDZ), which belongs

Research paper thumbnail of Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations

Journal of contaminant hydrology, Jan 14, 2015

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegrad... more Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, th...

Research paper thumbnail of Long-Term Sorption and Sequestration Dynamics of the Antibiotic Sulfadiazine: A Batch Study

Journal of Environment Quality, 2012

Understanding the long-term sequestration of veterinary antibiotics into soil fractions with diff... more Understanding the long-term sequestration of veterinary antibiotics into soil fractions with diff erent bioavailability is important in terms of assessing their eco-toxicological impact. We performed 60-d batch sorption experiments with radiolabeled sulfadiazine (SDZ) using samples from two agricultural soils. Sequential extraction with CaCl 2 /MeOH (easily accessible fraction), microwave (residual fraction, RES), and combustion (nonextractable residues, NER) was used to quantify the sequestration dynamics of the 14 C-derived SDZ-equivalent concentration. Multiple harsh extractions allowed us to mathematically extrapolate to the amount of SDZ equivalents that can be potentially extracted, resulting in halving the NER fraction aft er 60 d. A modifi ed two-stage model with irreversible sorption combined with global parameter optimization was able to display the sequestration dynamics. We demonstrated this with sterilized samples in which no transformation of the parent compound was observed. Th is also showed that transformation was primarily biologically driven. Th ese modeling results verifi ed the procedure, which was then applied to nontreated samples from both soils to estimate eff ective parameter values for SDZ-derived equivalents. Observed initial sorption, to which up to 20% of the kinetic sorption sites attributed, was included in the model. Both the RES and NER fractions reached a sorption plateau, with NER occupying about 30% of the kinetic fraction (RES+NER) for all soils. Th e sorption and sequestration of SDZ were soil-specifi c and dominated by kinetics. Sequestration in the RES fraction was much slower (characteristic time: 60 d) than the redistribution in the NER fraction (characteristic time: <6 d). Th e work presented here contributes to the prediction of the dynamics of (bio-)availability.

Research paper thumbnail of Dynamics of transformation of the veterinary antibiotic sulfadiazine in two soils

Chemosphere, 2014

We show transformation and sequestration of the antibiotic sulfadiazine in two soils. Transformat... more We show transformation and sequestration of the antibiotic sulfadiazine in two soils. Transformation products were found in liquid phase and extracts from the sorbed phase. We used a compartment model including all species and did global optimization. Sorption and transformation are concentration dependent.

Research paper thumbnail of Laboratory transport experiments with antibiotic sulfadiazine: Experimental results and parameter uncertainty analysis

AGU Fall Meeting Abstracts, Dec 1, 2011

Persistent antibiotics in the soil potentially contaminate the groundwater and affect the quality... more Persistent antibiotics in the soil potentially contaminate the groundwater and affect the quality of drinking water. To improve our understanding of antibiotic transport in soils, we performed laboratory transport experiments in soil columns under constant irrigation conditions with repeated applications of chloride and radio-labeled SDZ. The tracers were incorporated in the first centimeter, either with pig manure or with solution. Breakthrough curves and concentration profiles of the parent compound and the main transformation ...