Browsing by Subject "Pesticide"

Now showing 1 - 4 of 4
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    Abiotic transformations of pesticides in prairie potholes
    (2012-08) Zeng, Teng
    The prairie pothole region (PPR) is among the most extensively altered ecosystems on Earth. This region covers approximately 780,000 km2 of central North America, and contains numerous glacially formed wetlands embedded in an agricultural landscape. These wetlands, commonly known as prairie pothole lakes (PPLs), provide essential ecosystem services. Over the last 150 years, agricultural drainage has resulted in severe loss of native prairie wetlands. The remaining PPLs continue to be threatened by nonpoint source pesticide pollution from agriculture. Currently, little is known about the fate and persistence of pesticides in PPLs. In this work, the abiotic transformations of commonly used pesticides in PPL sediment porewaters and surface water were explored. Chloroacetanilide and dinitroaniline pesticides were found to react rapidly with naturally abundant reduced sulfur species (i.e., hydrogen sulfide and polysulfides) in sediment porewaters via nucleophilic substitution and reduction reactions, respectively. Dissolved organic matter (DOM) was also found to play a vital role in the reductive transformation. Next, the photodegradation of a suite of pesticides was investigated in PPL surface water under both simulated and natural sunlight. Enhanced pesticide removal rates pointed to the importance of indirect photolysis pathways involving photochemically produced reactive intermediates such as singlet oxygen and triplet excited-state DOM. Finally, the sedimentary sulfur speciation was examined by sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Sulfur species in PPL sediments were found to consist of organic (di)sulfides, sulfonate, sulfate, and the mineral pyrite. Notably, the fractional abundances of reduced and oxidized sulfur species fluctuate on a seasonal basis.
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    Biochar as a sorbent for naturally occurring and synthetic agricultural chemicals
    (2018-06) Hall, Kathleen
    The idea of adding biochar to soil to sequester carbon and improve fertility has soared in popularity over the past few decades; however, a strong scientific understanding of this material and its environmental effects is still lacking. This body of work explores biochar's interactions with chemicals, both naturally occurring (i.e., allelochemicals) and anthropogenically applied (i.e., herbicides), and sheds light on the mechanisms involved and our ability to predict and optimize its sorptive behavior. The first chapter investigates how the feedstock material from which a biochar is produced impacts its sorptive behavior toward allelochemicals. Mixing different feedstocks, such as pine chips and poultry litter, is thought to be a way to create “designer biochars” that combine the beneficial properties of each feedstock. However, results from this study revealed that mixing feedstock materials did not have predictable effects on organic compound sorption. The second chapter begins to evaluate biochar-chemical interactions in soil to better understand realistic applications of biochar as a sorbent. Here, the leaching potentials of six different herbicides were assessed in vulnerable Hawaiian soils, and biochar was tested as a tool to reduce the transport of the most mobile herbicide, aminocyclopyrachlor. It was found that none of the four biochar amendments tested significantly altered the leaching potential of aminocyclopyrachlor in these soils based on fate and transport models. In the third chapter, the focus shifts more towards understanding the mechanisms of biochar-herbicide interactions. Here we specifically looked at glyphosate, the world’s most widely used herbicide, and found that biochar macroporosity and specific surface functionality influenced glyphosate sorption. Additionally, pre-pyrolysis addition of Fe and Cu had no significant effect on sorption. Results from this work also demonstrated the reversibility of glyphosate sorption on biochar in the presence of phosphate, suggesting similar binding mechanisms and potential interferences from phosphate fertilizers. The fourth chapter continues to investigate the sorption mechanisms responsible for the observed biochar-herbicide interactions and simultaneously assesses our ability to optimize biochars for sorption through activation treatments. It was found that activation of a low-temperature biochar by hydrogen peroxide can improve the removal of organic acid herbicides from aqueous solution, but was of little value in optimizing the removal of non-ionizable herbicides. The improved removal efficiency was attributed to pH effects and charge-based interactions with biochar. Collectively, the research presented in this dissertation highlights the variability of biochar's sorptive behavior and illustrates the challenges in predicting this behavior, particularly when feedstocks are combined. While the sorptive applications in soil initially appear limited, there is potential to improve the sorption capacity of these materials through activation, and more targeted improvements will be possible once sorption mechanisms are better understood.
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    Detection of pesticide residues on apples using surface-enhanced Raman spectroscopy
    (2014-06) Chen, Tuo
    Pesticides are an integral part of agriculture, while increasing use leads to residues in/on agricultural products. Federal monitoring and enforcement action is dependent on the technical capability to detect pesticides. However, current methods are elaborate, time-consuming and not cost-effective. In the first part of this work, a rapid and simple surface-enhanced Raman spectroscopy (SERS) method coupled with a surface swab method for recovery and quantitative detection of thiabendazole (TBZ) on apple surfaces was developed, optimized and validated. The whole apple surface was swabbed and the swab was vortexed to release the pesticides. After that, silver dendrites (AgD) were used to bind the pesticide for Raman measurement. The limit of detection of TBZ in methanol was 0.01µg/mL, (10ppb), while the Environmental Protection Agency (EPA) limit is 5µg/gram apple-weight (5 ppm). The concentration of the recovered TBZ was predicted using a partial least square model. The recovery from the surface swab method was calculated to be 59.7% to 76.6% for intentional contamination at 0.1, 0.3, 3 and 5 ppm (µg/g apple-weight) level, respectively. The final accuracy of the swab-SERS method was calculated to be between 90.0% and 115.4%, after corrected by the releasing factor (66.6%). In the second part, a new approach was proposed to detect acetamiprid using an aptamer-based SERS method. The acetamiprid aptamer was chosen from the literature, thoilated and conjugated onto AgD. To block the unbounded surface on the substrate surface after aptamer immobilization, bovine serum albumin (BSA), 2-mercaptoethanol (ME) 6-mercaptohexanol (MCH) and were investigated as blocking agents. MCH and ME cannot fully block the surface when encountered with interference. The typical peaks from acetamiprid did not show on the aptamer-blocking agent-acetampired spectra when using BSA as blocking agents. The aptamer and blocking agent immobility on AgD should be further investigated and the method should be further modified. Last, the swab method was further developed and validated using UV-visible spectroscopy as a reference method. A standard curve was established based on the absorbance at 245 nm at different concentrations from 0 ppm to 1000 ppm. The assay standard curve well fit the five-parameter logistic model (r2 =0.995). The concentration of acetamiprid in the extracts was determined using this standard curve. The recovery rate of refined surface swab method is 90.6 % ± 1.4 % (n=5). This assay has a low intra- and inter-assay coefficient of variation (CV < 5 %).
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    The secondary exposure to pesticides among infants, children and adolescents study (ESPINA: Estudio de la exposición secundaria a plaguicidas en infantes, Niños y adolescentes)
    (2012-03) Suarez, Jose Ricardo
    INTRODUCTION: Children of agricultural workers are at risk of pesticide contamination through secondary routes (e.g. take-home pathway). Animal and human studies suggest that organophosphate and carbamate pesticide intoxication in early childhood can affect childhood development but it is not clear whether secondary pesticide exposures, which tend to be chronic but in low amounts, are sufficient to affect physiologic processes and development in children. Objectives: The Secondary Exposure to Pesticides among Infants, Children and Adolescents (ESPINA) study (Spanish: Estudio de la Exposición Secundaria a Plaguicidas en Infantes,Niños y Adolescentes) evaluated the effects of secondary pesticide exposure on childhood growth and neurobehavioral development among children living in Pedro Moncayo County, Ecuador, a county with an active fresh-cut flower industry. The following hypotheses were addressed: compared to children without secondary pesticide exposure (operationalized as flower plantation worker (flower worker) cohabitation), exposed children have: 1) lower acetylcholinesterase (AChE) activity, 2) lower neurobehavioral development scores, 3) lower systolic blood pressure, 4) lower resting heart rate and 5) slower growth. METHODS: ESPINA included socio-economic, demographic and anthropometric (height and weight) information of children from 0 to 5 years of age who participated in 2004 in the Survey of Access and Demand of Health Services in the County of Pedro Moncayo (SAHS-PM 2004). Pedro Moncayo County, Pichincha, Ecuador, has one of the highest concentrations of flower plantations per capita worldwide and the flower industry employs 21% of adults of Pedro Moncayo. In 2008, ESPINA examined children, 4 to 10 years of age, who participated in the SAHS-PM 2004 and new volunteers living in the County to obtain anthropometric measurements, a neurobehavioral developmental assessment and hemoglobin concentration and AChE activity. Study Design: This study is composed of: 1) a cross-section of 2004 to assess growth, 2) a cross-section of 2008 to assess neurobehavioral development, growth, heart rate, blood pressure and blood AChE levels; and 3) a longitudinal component (2004-2008) to assess growth. RESULTS: a) Participant Characteristics: From the SAHS-PM 2004, 922 (51% female) children were included. The mean age was 2.3 y (standard deviation (SD): 1.4 y), 63% cohabited with ≥1 flower worker with a mean of 2.0 flower workers at home. In ESPINA (2008), 313 (49% female, 78% mestizo) children participated; the mean age was 6.6y (SD=1.6 y), and 55% of participants cohabited with ≥1 flower worker. Flower worker cohabitants had a mean duration of cohabitation of 5.3 years and a mean of 1.5 flower workers at home. A total of 230 (49% female, 74% mestizo) children were examined in 2004 and 2008; the mean age was 6.4 years (SD=1.4 y) and 59% cohabited with at least one flower worker. Flower worker cohabitants had a mean duration of cohabitation of 5.1 years and a mean of 1.5 flower workers at home in 2008. b) Flower worker cohabitation and AChE activity: Mean acetylcholinesterase activity was 3.14 U/ml, standard deviation (SD): 0.49. It was lower by 0.09 U/ml (95% confidence interval (CI) -0.19, -0.001) in children of flower workers (57% of participants) than non-flower workers’ children, after adjustment for gender, age, height-for-age, hemoglobin concentration, income, pesticide use within household lot, pesticide use by contiguous neighbors, examination date and residence distance to nearest flower plantation. Using a 4 level polychotomous acetylcholinesterase activity dependent variable, flower worker cohabitation (vs. not) had odds ratio 3.39 (95% CI 1.19, 9.64) for being <15th percentile compared to the highest tertile. Children cohabitating for ≥5 years (vs. never) had OR of 4.11 (95% CI: 1.17, 14.38) of AChE activity within <15th percentile compared to the highest tertile. c) Secondary Pesticide Exposure and Neurobehavioral Development: The range of scores among 13 NEPSY-II subtests was 5.9-10.9 units (SD: 2.8-4.9). Boys with AChE activity in the lowest vs. the highest tertile had adjusted odds ratios (OR) of 7.40 (95%CI 1.71-32.05), 9.39 (95%CI 2.36-37.38) and 2.35 (95%CI 1.03-5.34) of low scores (<9th percentile) of Attention and Executive Functioning Domain, inhibitory control and long term memory, respectively, after adjusting for age, gender, race, height-for-age z-score, household income, flower worker cohabitation status, maternal education, hemoglobin concentration. Children’s cohabitation with a FW (vs. not) was associated with OR of low auditory attention score of 1.63 (95%CI 0.79,-3.37). AChE and FW cohabitation were not associated with other measures of neurobehavioral development. d) Secondary Pesticide Exposure and Blood Pressure (and Heart Rate) among Children living in Agricultural Communities in Ecuador: AChE activity was directly associated with blood pressure: every U/ml decrease was associated with a mean decrease in SBP of 1.54 mmHg (95%CI -2.68, -0.40) and DBP of 1.52 mmHg (95% CI -2.55, -0.50), after adjustment for age, gender, race, height-for-age z-score, heart rate, hemoglobin concentration, income, residence distance to nearest flower plantation edge, pesticide use within household lot, pesticide use by contiguous neighbors and examination date. Flower worker cohabitation was associated with lower systolic blood pressure (SBP) by 1.79 mmHg (95%CI -3.57, -0.01). Every year of cohabitation was associated with an adjusted decrease of SBP of 0.32 mmHg (95%CI 0.02, 0.64). Further adjustment for AChE weakened these associations. Cohabitation with a flower worker was not related to diastolic blood pressure (DBP); resting heart rate was not associated with flower worker cohabitation or AChE activity. e) Secondary Pesticide Exposure and Growth Cross-sectionally in 2004 (n=853), flower worker cohabitation was not associated with growth after adjusting for demographic and socio-economic factors. Longitudinally, child cohabitation with a flower worker was associated with decreased mean BMI-for-age (-0.36 standard deviations (SD), 95% CI: -0.66, -0.06) and weight-for-age (-0.33 SD, 95% CI: -0.61, -0.05). In 2008, flower worker cohabitation and lower AChE activity (per U/ml, mean=3.13 U/ml, SD=0.49) were both associated with larger head circumference (0.37 cm, 95% CI: 0.003, 0.74 and 0.75 cm, 95% CI: 0.30, 1.19, respectively). CONCLUSIONS: a) Cohabitation with a flower worker was related to lower AChE activity in children; this supports the hypothesis that indirect pesticide exposure from flower workers suffices to depress AChE activity, with greater suppression due to longer exposure. b) Low AChE activity was associated with deficits on tasks reflecting memory, attention and inhibitory control in boys. These are critical cognitive skills that affect learning and academic performance c) Our findings reflect physiologic reactivity in children with subclinical secondary exposures to pesticides and suggest vasodilation as an important mechanism of decreased blood pressure of cholinesterase inhibitors in this population. Although lower BP in isolation might be a beneficial effect of secondary pesticide exposure, the finding needs to be viewed with caution, as part of a pattern of generally adverse physiologic responses to pesticides. d) Our findings suggest that indirect pesticide exposures (estimated by AChE activity and cohabitation with a flower worker) can affect growth and head circumference in children living in agricultural communities. RECOMMENDATIONS: Our findings support the hypothesis that take-home pesticide exposures have physiologic effects in children of flower plantations workers. This investigation reinforces the importance of reducing the amounts of pesticides introduced into the homes by agricultural workers. Interventions to reduce secondary exposures targeting flower plantation workers and their families are needed. It is important to not only educate agricultural workers to adequately handle pesticides to reduce their contamination and that of their families, but also to provide adequate infrastructure to promote healthy practices including providing sufficient showers or and washing work clothes in the plantation.