Sorption, Transformation and Transport of Sulfadiazine in a loess and a sandy Soil

Veterinary antibiotics are unintentionally introduced into the environment and therefore found in ground and surface water, soil and sediments, air, plants etc. They enter these compartments mainly via application of manure or sewage sludge to soils for fertilizing purposes or after application in aquaculture, in form of the parent compound or a transformation product. Generally, sorption, transformation and transport determines the fate of these organic contaminants in soil. Their wide-spread distribution bears several risks, i. e. spreading of resistance genes or occurrence in the food chain. Long-term (60 days) batch studies were conducted applying radiolabelled sulfadiazine to samples from two agricultural soils to investigate the sorption and sequestration behaviour in the plow layers. Sequential extractions at several time-steps served to analyse the dynamics of both processes. A numerical evaluation served to describe instantaneous sorption, the dynamics of sorption and sequestration, and the formation of non-extractable residues. Multiple extractions with the harsh method questioned the concept of non-extractable residues, since with each consecutive extraction step, further sulfadiazine could be extracted. Analysing the liquid phase and the extracts from these batch experiments with Radio-HPLC served to improve the understanding of the transformation behaviour in soils in different degrees of (bio-)availability. Apart from the deduction of rate-parameters for a compartment model, the resemblance of the compositions in the liquid phases and the harsh extracts was demonstrated. The formation of the up to six transformation products showed distinct dynamics, either spontaneous or with a time-lag. Laboratory column experiments with multiple applications of sulfadiazine either together with manure from pig-feeding experiments or in liquid solution served to the improved understanding of the transport processes and the transformation during transport. A numerical description of the breakthrough curves elucidated the processes during movement through undisturbed soil. The composition in the outflow was considerably different in terms of transformation products, as a factor of application mode and soil. This thesis updated the knowledge of the environmental behaviour of sulfadiazine, since we investigated the fate in its most important aspects of sorption, transformation and transport

Risk mitigation measures for pesticide runoff: How effective are they?

BACKGROUND: One of the most important sources of pesticide pollution of surface waters is runoff and erosion from agricultural fields after rainfall. This study analyses the efficacy of different risk mitigation measures to reduce pesticide runoff and erosion inputs into surface waters from arable land excluding rice fields. RESULTS: Three groups of risk mitigation measures were quantitatively analyzed: vegetative filter strips, micro-dams in row crops and soil conservation measures. Their effectiveness was evaluated based on a meta-analysis of available experimental data using statistical methods such as classification and regression trees, and exploratory data analysis. Results confirmed the effectiveness of vegetative filter strips and micro-dams. Contrary to common assumption, the width of vegetative filter strips alone is not sufficient to predict their effectiveness. The effectiveness of soil conservation measures (especially mulch-tillage) varied widely. This was in part due to the heterogeneity of the available experimental data, probably resulting from the inconsistent implementation and the inadequate definitions of these measures. CONCLUSION: Both vegetative filter strips and micro-dams are effective and suitable, and can therefore be recommended for quantitative assessment of environmental pesticide exposure in surface waters.However, the processes of infiltration and sedimentation in vegetative filter strips should be simulated with amechanistic model like Vegetative Filter Strip Modeling System, VFSMOD. The reduction effect ofmicro-dams can be modelled by reducing the runoff curve number, e.g., in the pesticide root zone model, PRZM. Soil conservationmeasures are in principle promising, but further well-documented data are needed to determine under which conditions they are effective

Sorption, Transformation and Transport of Sulfadiazine in a loess and sandy oil

Veterinary antibiotics are unintentionally introduced into the environmentand therefore found in ground and surface water, soil andsediments, air, plants etc. They enter these compartments mainly via application of manure or sewage sludge to soils for fertilizing purposes or after application in aquaculture, in form of the parent compound or a transformation product. Generally, sorption, transformation and transport determines the fate of these organic contaminants in soil. Their wide-spread distribution bears several risks, i. e. spreading of resistance genes or occurrence in the foodchain. Long-term (60 days) batch studies were conducted applying radiolabelled sulfadiazine to samples from two agricultural soils to investigate the sorption and sequestration behavior in the plow layers. Sequential extractions at several time-steps served to analyze the dynamics of both processes. A numerical evaluation served to describe instantaneous sorption, the dynamics of sorption and sequestration, and the formation of non-extractable residues. Multiple extractions with the harsh method questioned the concept of non-extractable residues, since with each consecutive extraction step, further sulfadiazine could be extracted. Analyzing the liquid phase and the extracts from these batch experiments with Radio-HPLC served to improve the understanding of the transformation behavior in soils in different degrees of (bio-)availability. Apart from the deduction of rate-parameters for acompartment model, the resemblance of the compositions in the liquid phases and the harsh extracts was demonstrated. The formation of the up to six transformation products showed distinct dynamics, either spontaneous or with a time-lag. ..

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

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, the sandy, and thus highly permeable, soil was characterized by short half-lives and thus a quick biodegradation of SDZ. For 2-aminopyrimidine, half-lives of only a few days were observed. Increased field-scale biodegradation in the sandy soil resulted from a higher water and air permeability that enhanced oxygen transport and limited oxygen depletion. Furthermore, low pH was more important than the organic matter and clay content for increasing the biodegradation of SDZ. A numerical analysis of breakthrough curves of bromide, SDZ, and its TPs showed that preferential flow pathways strongly affected the solute transport within shallow parts of the soil profile at the field scale. However, this effect was reduced in deeper parts of the soil profile. Due to high field-scale biodegradation in several layers of both soils, neither SDZ nor 2-aminopyrimidine was detected in the discharge of the lysimeter at a depth of 1 m. Synthetic 50 year long simulations, which considered the application of manure with SDZ for general agricultural practices in Germany and humid climate conditions, showed that the concentration of SDZ decreased below 0.1 μg/L in both soils below the depth of 50 cm

Dermal phospho-alpha-synuclein deposits confirm REM sleep behaviour disorder as prodromal Parkinson's disease

Phosphorylated alpha-synuclein (p-alpha-syn) deposits, one of the neuropathological hallmarks of Parkinson's disease (PD), have recently been detected in dermal nerve fibres in PD patients with good specificity and sensitivity. Here, we studied whether p-alpha-syn may serve as a biomarker in patients with a high risk of developing PD, such as those with REM sleep behaviour disorder (RBD). We compared the presence and distribution of p-alpha-syn deposits in dermal nerve fibres in 18 patients with RBD, 25 patients with early PD and 20 normal controls. Skin biopsy was taken at C7, Th10, and the upper and lower leg. Presynaptic dopamine transporter imaging using FP-CIT-SPECT was performed in all patients with RBD and in 11 patients with PD. All RBD patients underwent olfactory function testing. The likelihood ratio (LR) for prodromal PD was calculated for each patient based on published research criteria. Skin serial sections were assessed by double-immunofluorescence labelling with antibodies to pSer129-alpha-syn under blinded conditions. P-alpha-syn was visualized in 10/18 patients with RBD (sensitivity of 55.6%) and in 20/25 early PD patients (sensitivity of 80%) but in none of the controls (specificity of 100%). The percentage of dermal structures innervated by p-alpha-syn-positive fibres was negatively correlated with dopamine transporter binding in the FP-CIT-SPECT (ρ = -0.377, p = 0.048), with olfactory function (ρ = -0.668, p = 0.002), and positively correlated with the total LR for RBD to present prodromal PD (ρ = 0.531, p = 0.023). Dermal p-alpha-syn can be considered a peripheral histopathological marker of synucleinopathy and can be detected in a subgroup of RBD patients presumably representing prodromal PD. Dermal p-alpha-syn is detectable in RBD patients without PD motor symptoms, thereby stratifying a patient group that is of great interest for clinical trials testing disease-modifying drug

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

Understanding the long-term sequestration of veterinary antibiotics into soil fractions with different 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/MeOH (easily accessible fraction), microwave (residual fraction, RES), and combustion (nonextractable residues, NER) was used to quantify the sequestration dynamics of the 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 after 60 d. A modified 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. This also showed that transformation was primarily biologically driven. These modeling results verified the procedure, which was then applied to nontreated samples from both soils to estimate effective 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. The sorption and sequestration of SDZ were soil-specific 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). The work presented here contributes to the prediction of the dynamics of (bio-)availability