Browsing by Subject "Pesticide"

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Assessment of hydrology and dynamics of pesticides in a tropical headwater catchment in Northern Thailand
(2013) Hugenschmidt, Cindy; Streck, Thilo
The dissertation deals with assessment of hydrology and the dynamics of pesticides in a tropical headwater catchment in northern Thailand. Rainfall and runoff characteristics are recorded and investigated, pesticide dynamics during single events are monitored and studied. Finally, a hydrological model is applied.
Charakterisierung der Qualität von Blütenpollen in unterschiedlichen Regionen Baden-Württembergs
(2022) Friedle, Carolin Gertrud Maria; Hasselmann, Martin
Honey bees (Apis mellifera) collect nectar and pollen from plants to feed their brood. Pollen provides a wide range of nutrients, such as proteins and lipids, but also carbohydrates, vitamins and enzymes. Because of these ingredients, pollen is also attractive to humans and is used as a dietary supplement. However, honey bees collect pollen not only from wild plants, but also from flowering crops grown in agriculture. Accordingly, contamination from plant protection products can be found in bee pollen and bee bread. In order to get a deeper insight into the occurrence and distribution of pesticide residues during an entire season, a total of 102 daily pollen samples were collected from April to July 2018 using pollen traps in an orchard in southern Germany. Almost 90% of the pollen samples showed detectable levels of pesticide residues. A total of 29 pesticides were detected in the samples, with more than half being fungicides, followed by insecticides and herbicides. Maximum concentrations of up to 4500 ng/g could be measured at the end of April. Samples collected in early May and late June also showed high levels of pesticides. A general risk management was performed to assess the risk of the detected pesticide concentrations for honey bees. The microbial quality of bee pollen is highly dependent on its botanical and geographic origin, as well as climatic conditions and post-harvest processing steps by the beekeeper. If no processing steps such as freezing or drying follow after harvest, the growth of microorganisms can be promoted and the pollen quality can be influenced by negative side effects such as fermentation or the production of mycotoxins. Bacterial and fungal colonies can be determined both by culture-dependent methods such as colony counting on plates and by culture-independent methods such as 16-rRNA amplicon sequencing. Following the hypothesis that storage conditions influence the composition of microorganisms in bee pollen, freshly harvested bee pollen was stored for seven days in June 2018 and 2019 under defined conditions (cold, room temperature, warm) and analyzed by sequencing 16S and 18S PCR amplicons. The bacterial community varied slightly between the sites studied and showed no significant difference between the storage conditions. The fungal community showed significant differences both between the studied sites and between the different storage conditions. The dominant fungal genera in the pollen samples were Cladosporium, Aspergillus and Zygosaccharomyces. While Cladosporium was most dominant in freshly collected pollen and the percentage decreased during storage, Aspergillus and Zygosaccharomyces showed a significant increase especially under warm storage conditions. Other contaminants naturally produced by plants can also have negative impacts on human health. Pyrrolizidine alkaloids belong to a group of phytochemicals, of which more than 600 structures are known in around 3% of all flowering plants worldwide. PA are known to be able to cause both acute poisoning and chronic damage or cancer in animals and humans. In July 2019, pollen was collected at 57 locations in Baden-Württemberg and analyzed for 42 different PAs and their N-oxides in order to expand knowledge about PA contamination in pollen and to be able to estimate the risk of the concentrations. A total of 22 different PAs were detected in over 90% of all samples examined. Only 5% of the PA were obtained as PA from plants of Senecio sp. identified, while 95% of PAs with a botanical background are from Echium sp. and Eupatorium sp. could be identified. The maximum total concentration of PA per sample was determined to be 48,400 ng/g. According to the risk values calculated by the BfR, however, 42% of the samples represented an increased risk to human health.
Effects of chronic pesticide and pathogen exposure on honey bee (Apis mellifera L.) health at the colony level
(2018) Odemer, Richard; Bessei, Werner
During the last decade the increasing number of honey bee colony losses has become a major concern of beekeepers and scientists worldwide. Extensive research and cooperation projects have been established to unravel this phenomenon. Among parasites, pathogens and environmental factors, the use of agrochemicals, most notably the class of neonicotinoid insecticides, are suspected to be a key factor for this collapse. Current approaches not only focus on colony collapse but also on the weakening of honey bees by the exposure to sublethal concentrations of such pesticides. Recently, the EFSA temporarily banned three neonicotinoids including clothianidin, imidacloprid and thiamethoxam, for the use in crops attractive to pollinators. Thiacloprid however, likewise a neonicotinoid insecticide, is still tolerated for agricultural use because it is considered less toxic to bees. Nevertheless, some publications indicate sublethal effects of this agent leading to impairments of the colony. A general problem for the study of such sublethal effects is that they often are measurable in individual bees without eliciting clear impact at the colony level. In addition, such effects might only have a consequence in combination with other stressors like pathogens. This thesis presents two new methodical approaches combining the controlled application of stressors to individual bees with an evaluation of the effects under field realistic conditions of free flying colonies. In all approaches, the bees were treated with a combination of different pesticides and/or a combination of pesticides and a pathogen in order to evaluate synergistic interactions. As pathogen, Nosema ceranae, a novel intracellular gut parasite introduced from Asia, was used. This parasite is considered to contribute to “CCD”-like symptoms (“colony collapse disorder”), particularly in Spain. In Retschnig et al. (2015), observation hives at two study sites (Hohenheim and Bern) were used to clarify possible synergistic effects when honey bees are exposed to pesticides of two different substance classes (thiacloprid and tau-fluvalinate), both in combination with an infection of N. ceranae. Mortality, flight activity and social behaviour of individually marked and treated worker bees were monitored. At the Hohenheim site, no impact from any of the treatments could be confirmed except a slightly higher flight activity of the Nosema treated bees. At the Bern site however, the pesticide treatments elicited a significant reduction of worker bee lifespan, whereas the Nosema infection resulted in higher ratios of motionless periods. Importantly and in contrast to several laboratory studies, in neither of the two sites an interaction among the pesticides and the pathogen could be confirmed. The inconsistency of our results suggests that the effects of both, sublethal application of pesticides and infection with N. ceranae were rather weak and that interaction among them may have been overemphasized. To extend this first approach in small observation colonies, Odemer & Rosenkranz (2018) focused on performance parameters such as colony development and overwintering in honey bee colonies, using the same pesticides as in the observation hives. Here, neither the single exposure to thiacloprid or tau-fluvalinate nor their combination had negative effects on the colony performance. However, the chronic application of the tau-fluvalinate significantly reduced the infestation with Varroa mites. In Odemer et al. (2018), a neonicotinoid (clothianidin) with an extraordinary high toxicity to bees was applied alone and in combination with N. ceranae and N. apis. A novel approach was developed with individually marked bees that were infected after hatching with a certain number of Nosema spores and introduced into mini-hives. In order to simulate worst case field conditions, the pesticide was then applied chronically in sublethal concentrations over the whole lifespan of the bees. Again in contrast to previous laboratory studies, no effect of the clothianidin treatment on mortality or flight activity could be observed. However, the lifespan of Nosema infected bees was significantly reduced compared to non-infected bees, but in agreement with the observation hive experiment, the combination of pesticide and pathogen did not reveal any synergistic effect. The results of the three experiments of this thesis indicate that (i) individual honey bees are less impaired by neonicotinoids if kept within the social environment of the colony and that (ii) sublethal concentrations of neonicotinoids in the field are not the main driver for colony losses. These statements refer exclusively to the honey bee colony as a eusocial superorganism that obviously is more resilient to pesticide exposure through mechanisms of “social buffering”.
High-throughput planar solid phase extraction : a new clean-up concept in multi-residue analysis of pesticides
(2014) Oellig, Claudia; Schwack, Wolfgang
Currently, the most serious problems in pesticide residue analysis by liquid chromatography (LC) or gas chromatography (GC) coupled to mass spectrometry (MS) concern the so-called “matrix effects”. The most common way to avoid these effects is the application of matrix-matched calibration standards. Nevertheless, an efficient clean-up undoubtedly is the best way to prevent matrix effects in multi-residue analysis of pesticides in food by LC–MS or GC–MS. For a totally new powerful clean-up method, called high-throughput planar solid phase extraction (HTpSPE), highly automated planar chromatographic tools were applied to remove co-extracted matrix substances entirely and to eliminate any kind of matrix related effects. For sample extraction, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was used to initially collect pesticides from fruits and vegetables. The received acetonitrile extracts were applied directly for the development of the novel HTpSPE clean-up. Thin-layer chromatography (TLC) was used to completely separate pesticides from matrix compounds and to focus them into a sharp zone. A two-fold development on amino-modified silica gel thin-layers with acetonitrile for the first development, and acetone for the second development in the backwards direction, was evaluated to perform the best clean-up result and collect the pesticides in a sharp, single target zone. To easily locate the pesticide zone, the Sudan II dye was added to the extracts. Following this clean-up, the target zones (pesticides) were eluted by the TLC–MS interface into vials for the LC–MS determination. HTpSPE resulted in extracts which were nearly free of co-extracted matrix and matrix effects, as shown for seven chemically representative pesticides (acetamiprid, azoxystrobin, chlorpyrifos, fenarimol, mepanipyrim, penconazole, and pirimicarb) in four different fruit and vegetable matrices (apples, cucumbers, red grapes, and tomatoes). Thanks to the very clean HTpSPE extracts, calibration can simply be performed with pure solvent standards and the quantitation by LC–MS provided excellent mean recoveries and relative standard deviations. In addition, tea samples as rather challenging matrices were chosen to apply for HTpSPE. The matrix load of tea extracts generally was too high for the available thin-layer capacity and the selectivity of the amino-modified phase was not suitable for the separation of caffeine and further matrix compounds from the target analytes (pesticides). By modifying the sample extraction, adding a pre-cleaning by dispersive solid phase extraction (dSPE) and changing the thin-layer phase to normal phase silica gel, the complete separation of pesticides and tea matrix components was possible, when again a two-fold development was applied. Caffeine and other alkaloids were completely removed. The effectiveness of HTpSPE was demonstrated by LC–MS/MS calibration curves from matrix-matched and solvent standards, which were nearly identical and by very good mean recoveries, calculated against pure solvent standards. Concerning all validation parameters, the new acetonitrile-HTpSPE procedure for tea samples was superior to the QuEChERS-dSPE method and offered highly successful results. In recent years, large-scale screening in pesticide residue analysis has gained more and more importance. Keeping this in mind, a screening strategy for HTpSPE extracts, using a high-resolution MS, was developed to analyze the cleaned extracts directly for pesticide residues without a liquid chromatographic separation. By this hyphenation, a completely new microliter-flow injection analysis–time-of-flight mass spectrometry (µL-FIA–TOFMS) screening was introduced. The novel HTpSPE–µL-FIA–TOFMS approach enabled the detection of all pesticides simultaneously in a single mass spectrum within a few minutes. The obtained mass spectra were nearly free of matrix compounds, which is especially the great benefit of the effective HTpSPE clean-up. Recovery studies by HTpSPE–µL-FIA–TOFMS against solvent standards for the matrices and pesticides under study provided excellent results, using the mass signal intensities under the entire FIA sample peak. HTpSPE clearly showed superior results concerning every tested parameter than dSPE. With the help of a self-constructed mass database searching tool, all spiked pesticides were detected and correctly identified, while only very low numbers of false-positive findings occurred. Furthermore, a non-target screening approach was successfully implemented by slightly changing the database searching process, offering a mass list of all substances, which are present in the injected extracts but not included in the mass database. Finally, the new HTpSPE–µL-FIA–TOFMS screening was successfully applied to several real samples, when the identified pesticides were quite identical compared to results of LC–MS/MS analysis of the QuEChERS-dSPE extracts.
Transport of pesticides in a river of a tropical mountainous watershed in northern Thailand
(2013) Sangchan, Walaya; Streck, Thilo
In the northern region of Thailand, in the upland areas population growth and migration of people from the lowlands have rapidly driven land use changes. The expansion of cultivation to increasingly vulnerable areas such as the slopes of mountainous watersheds has led to increasingly adverse impacts on the environment. In particular, intensive application of pesticides poses a contamination risk for stream water and the aquatic ecosystem. This thesis identified the transport patterns of pesticides with different physico-chemical properties during single runoff events under farmer?s practice conditions on the catchment scale. Moreover, the exposure concentrations of frequently used pesticides in surface water and sediment in the watershed were measured in the frame of long-term monitoring. The data were used to calculate pesticide loads in the Mae Sa watershed (Chiang Mai, Thailand) and to assess the ecological risk of pesticides for the aquatic ecosystems. Prior to start of the monitoring program, methods to extract and analyze pesticides in the surface water and sediment samples were established. The pesticides in water samples were extracted by solid phase extraction with a graphitized carbon black sorbent. The recoveries of pesticides in a simultaneous analysis ranged from 58 % to 117 % for the seven pesticides (dichlorvos, atrazine, dimethoate, chlorothalonil, chlorpyrifos, (α, β) endosulfan, cypermethrin) with a high repeatability of the method (Relative Standard Deviation, (RSD)<20 %), except for chlorothalonil (RSD=27 %). For analysis of sediments, the QuEChERS method was adapted. Extraction conditions such as solvent, partitioning of pesticide due to salt effect and clean up step with dispersive solid phase extraction were optimized. Except for dichlorvos in the bed sediment sample and for dimethoate in bed and suspended sediments, recoveries were between 81 % and 116 %. The results show that the QuEChERS method is a valuable method for extracting pesticides from sediment samples. To identify the transport pathways contributing to pesticide losses from soil to the Mae Sa River, automatic gauging stations were installed at the headwater (HW) and outlet (OL) of the watershed to measure discharge and to collect water samples for pesticide analysis. During three runoff events in May, August and September 2008, water samples were collected in a high temporal resolution (1 hour). The potential transport pathways of pesticides were elucidated by time series analysis. Three different input patterns of pesticides were observed: (a) pesticide peaks during the rainfall events as discharge increased, (b) sporadic high concentrations of pesticides during the falling limb of the runoff peak, and (c) low concentrations but more or less continuous values on a baseline level. A chromatographic effect was observed for many pesticides, for example between dimethoate and chlorpyrifos. Highly mobile pesticides such as atrazine and dimethoate were likely to suffer loss at the beginning of the runoff event, while strongly sorbing pesticides such as chlorpyrifos were slightly delayed. This indicates an interaction with the soil matrix, during transport along a sub-surface pathway. The results obtained in the middle of the rainy season in August and September events showed that antecedent rainfall plays an important role in triggering pesticide transport by preferential interflow. In both events the sporadic appearances of strongly sorbing pesticides such as chlorothalonil and chlorpyrifos after peak flow suggest this transport type. For ecotoxicological risk assessment, the highly dynamic nature of pesticide input to surface waters must be considered in the design of representative monitoring schemes. Not only the periods during rain event and peak runoff, but also the following recession phase, during which short and pulsed concentration peaks might show up, must be captured by a representative sampling scheme. Therefore, a high temporal resolution is advisable. To study the long-term dynamics of seven selected pesticides in the Mae Sa River and to evaluate their environmental impacts to aquatic organisms, the exposure concentrations of the pesticides in water and sediment samples were monitored at three stations (HW, Mae Sa Noi flume (MSN), and OL) in the watershed over a period of one and half year (from July 2007 to November 2008). Aquatic risk assessment concerning the observed pesticide concentrations was performed by using the risk characterization ratio (RCR). Chlorpyrifos was the most frequently detected pesticide in surface water at the HW and OL. Cypermethrin was the most frequently detected pesticide in bed and suspended sediment samples along the Mae Sa Noi tributary and at the HW. Regarding the change of pesticide use in the area (compared with data recored in 2002), the measurements suggest that the use of endosulfan has been reduced in recent years, while the observed concentrations of chlorothalonil and chlorpyrifos were in the same concentration ranges as in 2002. The temporal distribution of pesticides shows that the concentrations are highest during the rainy season. Outstandingly high losses of dichlorvos and atrazine were found at Mae Sa Noi flume. Loads of chlorothalonil and chlorpyrifos in stream water were extremely high in the headwater area. Based on interview data of pesticide use in the Mae Sa watershed, in both years the losses of single pesticides to surface water ranged from 0.004 % (chlorothalonil) to 4.7 % (dimethoate) of the applied pesticide mass. The loss of atrazine could not be included because the data did not contain information on the application rate of atrazine. The risk assessment shows that particularly dichlorvos and endosulfan have a high potential to cause adverse effects to the aquatic ecosystem. The RCRs of endosulfan and cypermethrin show that they are the main stressors in the sediment phase. This reveals that aquatic ecosystem of the Mae Sa watershed is facing adverse effects by the contamination of surface water and sediment with pesticides. Hence, measures are urgently needed to reduce the loss of pesticides from soil to surface waters.