Spray nozzle designs for agricultural aviation applications

Techniques of generating monodisperse sprays and information concerning chemical liquids used in agricultural aviation are surveyed. The periodic dispersion of liquid jet, the spinning disk method, and ultrasonic atomization are the techniques discussed. Conceptually designed spray nozzles for generating monodisperse sprays are assessed. These are based on the classification of the drops using centrifugal force, on using two opposing liquid laden air jets, and on operating a spinning disk at an overloaded flow. Performance requirements for the designs are described and estimates of the operational characteristics are presented

Developing paper-based devices for mapping agricultural pesticides and environmental contaminants

2021 Summer.Includes bibliographical references.The detection of environmental contaminants is important to ensure the health of both humans and the environment. Currently, detection is done by instrumentation like liquid or gas chromatography coupled with mass spectrometry. While sensitive and selective for multiple analytes, these instruments suffer from disadvantages like large size, high sample cost, and the need for a trained analyst to run the samples. As an alternative, microfluidic paper-based analytical devices (µPADs) are becoming more common as inexpensive, fast, easy to use devices to detect and quantify a variety of analytes. My research has been focused on developing µPADs for three different analytes: pesticides, PFAS, and heavy metals. In order to ensure proper crop protection and pest management, it is important to manage and optimize pesticide application. Currently, this is done by water-sensitive papers, which often inaccurately portray the presence of pesticide due to humidity and extraneous water droplets that are not pesticide. In Chapter 2, I have developed a method that uses filter paper to capture a fluorescent tracer dye that has been mixed with the pesticide and then sprayed over the crop. The filter papers are imaged with a lightbox and Raspberry Pi camera system and then analyzed to determine percent coverage. After optimization and validation of the method to WSP, the filter paper method was used to evaluate pesticide distribution in a citrus grove in Florida (Chapter 3). The data from these field studies was used to make recommendations for which application method is best for the different types of pesticides. Paper-based devices are inherently limited by the inability to control fluid properties like mixing. In order to incorporate mixing but also retain a small device that does not require external power to initial flow, a microfluidic device was fabricated out of two glass slides. A staggered herringbone pattern is laser ablated into the slides, and a channel is formed by double-sided adhesive (Chapter 4). Mixing was quantified using blue and yellow dyes. A reaction between horseradish peroxidase and hydrogen peroxide was used as a representative enzymatic reaction and also to determine enzyme kinetics. Since the microfluidic device is made of glass, it is also compatible with non-aqueous solvents. Paper-based devices do not work well with organic solvents because the hydrophobic wax on the paper is dissolved by the solvent. In Chapter 5, the dissertation returns to traditional µPADs for environmental contaminants. Per- and polyfluoroalkyl substances (PFAS) are class of compounds that are highly persistent, toxic, bioaccumulative, and ubiquitous. While multiple instrument-based methods exist for sensitive and selective detection in a variety of matrices, there is a huge need for a fast, inexpensive, and easy-to-use sensor for PFAS detection. This would enable widespread testing of drinking water supplies, ensuring human health. A µPAD was developed for the detection of perfluorooctane sulfonate (PFOS) where the ion-pairing of PFOS and methylene green forms a purple circle. The diameter of the purple circle can be measured by the naked eye with a ruler or with the help of a smartphone to correlate the diameter back to PFOS concentration. At a cost of cents per sample, this µPAD enables fast and inexpensive detection of PFOS to ensure safe drinking water. A common issue with environmental µPADs is the relatively high limits of detection compared to what is needed for regulatory purposes. It can be challenging to lower the limits of detection without incorporating an external pretreatment and/or preconcentration step. As µPADs are small and handle only a small volume of sample (<120 µL), there is the possibility of increasing the sample capacity of the device but without significantly increasing the device size or analysis time. By adding multiple layers of absorbent filter paper underneath radial device for heavy metal detection, the sample volume increased to 1 mL, decreasing the limit of detection for a radial copper detection card from 100 ppb to 5 ppb (Chapter 6). The research presented here achieves the goal of developing µPADs for environmental contaminants. They can be used in different ways to visualize the presence of the contaminant for monitoring and management purposes, ultimately ensuring human and environmental health

Pesticide Applications in Agricultural Systems

The effective and efficient application of PPP in agriculture is a very complex task, involving a lot of aspects ranging from active substance properties to climatic conditions, from target structure to equipment features, from operator awareness to the reference legislative framework. Some of these aspects have been treated in the six papers collected in this Special Issue on “Pesticide Applications in Agricultural Systems”

Optical analytical methods for detection of pesticides

The global pesticide market has grown steadily since the 1940s, with the agricultural sector being the largest user of pesticides. The effect of pesticides on human health is manifested either through direct exposure to the material or indirect exposure to contaminated resources. Farmers and those dwelling near areas where pesticides are used may suffer from direct exposure, while the general population might be exposed indirectly, for example, by drinking contaminated water. Exposure to pesticides may cause a variety of symptoms, including headaches, dizziness, and vomiting, damage the nervous system, and even cause death. The risks involved in pesticide use include air pollution and soil and water contamination. The environmental implications of pesticide use include development of resistance among pests, a decline in biodiversity, interruption of the food chain, and disruption of the ecological balance. Pesticide use may also cause changes in physical parameters of the ecosystem. Effective activity of pesticides requires reaching proper leaf coverage. To prevent pest attacks due to insufficient leaf coverage, farmers tend to apply pesticides in excess. In view of the environmental and health implications of pesticide use, there is a clear need to limit pesticide application. Yet farmers lack the means to perform real-time in situ assessment of leaf coverage. Existing pesticide detection methods are complex, time-consuming, and unsuited to field application. Optical methods have the potential to provide quick assessments and can be used in situ. Several optical methods for detection of pesticides in general and on leaves in particular were developed. The findings indicated that the main problems in pesticide detection using fluorescence are the low autofluorescence of the pesticides and the nonreproducible spectral response of the leaves. These obstacles were solved by employing labeling agents. For example, rhodamine was suggested, mainly due to its excellent surface adhesion and its extremely high fluorescence quantum yield. The labeling agents were sprayed on leaves in the form of aerosols, thus creating a uniform layer of nanocrystals and microcrystals on the surface of the leaves. The effects of pesticides on the spectral characteristics of the labeling agents were examined using laser-induced fluorescence (LIF) spectroscopy. When pesticide droplets were applied to a pretreated leaf, two phenomena were observed. The first was a substantial fluorescence increase. The second was material-specific spectral shifting as a result of interaction between the labeling molecules and organic components in the pesticide droplet. It was possible to utilize these spectral shifts for quantification of the pesticide concentration in the droplet. These spectral shifts enabled detection of pesticides on plants, although they were not sufficient for providing quantitative information on the extent of pesticide coverage. To detect pesticide coverage, several imaging data techniques were applied, such as LIF scanning of the examined plant surface. This method revealed the droplet shape by scanning and recording the fluorescence intensity at many points on a grid. Since application of this method is expensive and time-consuming, a second technique was also developed: it requires only a UV source and a CCD camera and it enables direct imaging of the pesticides on plants. The data obtained included the droplet shape and its location on the plant. When pesticide identification was required, application of a special hyperspectral fluorescence imaging method was introduced. Fourier transform hyperspectral imaging analysis provided simultaneous full spectral resolution at each pixel, enabling identification of the pesticide and its mapping on the plant. In practice, test plants have to be pretreated with labeling material before pesticide application. The changes in the labeling compound fluorescence can then be used for detection of the pesticide on the plant and quantification of the overall coverage. Low-cost mapping of the pesticide microdroplets could be obtained using a CCD camera, while accurate information could be based on Fourier transform hyperspectral imaging. Since these methods provide immediate results, they may allow the farmer to estimate leaf coverage during pesticide application and adjust spraying accordingly. © 2011 by Walter de Gruyter Berlin Boston

Evaluation of low-volume herbicide application technology for no-till soybeans

A study performed at The University of Tennessee Milan Experiment Station during 1983 evaluated and compared preemergence and postemergence herbicide application techniques in no-tillage and conventionally-cultivated soybean plots. The equipment utilized for herbicide application included conventional medium-volume hydraulic flat fan nozzles, low-volume flat fan nozzles, controlled droplet applicators (CDA), and an ultra low-volume electrostatic sprayer. Various application parameters and techniques were compared: low-volume versus medium-volume spray rates, ultra-low versus medium-volume application rates, flat fan nozzles versus controlled droplet applicators (CDA) for low-volume spraying, and water-only carrier versus oil-in-water diluents for low-volume application. Sprayed plots were evaluated for percentage control of selected weed species and for soybean yields. Results showed that spray application volume (5 gal/acre versus 20 gal/acre) applied either preemergence or postemergence did not affect the level of weed control in no-till soybeans. Moreover, low-volume hydraulic nozzles and controlled droplet applicators (CDA) at 5 gal/acre were equally effective in controlling weeds. Roundup plus Lorox plus Lasso applied preemergence in wheat stubble gave significantly better control of Pennsylvania smartweed than a tank mix of paraquat plus Lorox plus Lasso. Both full and half-label rates of Basagran plus Blazer applied postemergence in wheat stubble were significantly more effective in controlling cocklebur than Pennsylvania smartweed. Addition of a crop oil concentrate did not increase weed control in the low-volume treatments. Application of Fusilade in conventionally-cultivated soybeans using an electrostatic spray system at 0.8 pt/acre total spray volume gave similar levels of weed control to applications of the same herbicide rates at 20 gal/acre using conventional hydraulic nozzles. Soybean yields overall in 1983 were much below normal due to drought conditions during the growing season. Crop yields within a given production practice were not significantly affected by spray application techniques

A review of the meteorological parameters which affect aerial application

The ambient wind field and temperature gradient were found to be the most important parameters. Investigation results indicated that the majority of meteorological parameters affecting dispersion were interdependent and the exact mechanism by which these factors influence the particle dispersion was largely unknown. The types and approximately ranges of instrumented capabilities for a systematic study of the significant meteorological parameters influencing aerial applications were defined. Current mathematical dispersion models were also briefly reviewed. Unfortunately, a rigorous dispersion model which could be applied to aerial application was not available

Ecological monitoring methods for the assessment of pesticide impacts in the tropics

The use of agrochemicals in developing countries has increased greatly in recent years and those used in greatest quantities, insecticides and herbicides, tend to have the most severe side-effects on the environment. Following UNCED 1992 and its adoption of Agenda 21, there is now a requirement for all countries to carry out pesticide impact monitoring and assessment to counter environmental degradation. The recent UNCED Summit 2002 has set targets to step up the implementation of this commitment. Ecological Monitoring Methods for the Assessment of Pesticide Impact in the Tropics aims to assist developing countries build their capability in ecotoxicological monitoring. It harnesses the knowledge of pesticide impact and monitoring specialists to provide guidance on the measurement, analysis and interpretation of change in animal populations and key soil functions. This handbook will be of primary interest to those in government, development agencies, donors and non-governmental organizations who carry responsibility for the environment, agricultural and public health. Academics and students of ecotoxicology in developing countries should find both the specialist chapters and the field methodology useful

How does exposure to pesticides vary in space and time for residents living near to treated orchards?

This study investigated changes over 25 years (1987-2012) in pesticide usage in orchards in England and Wales and associated changes to exposure and risk for resident pregnant women living 100 and 1000 m downwind of treated areas. A model was developed to estimate aggregated daily exposure to pesticides via inhaled vapour and indirect dermal contact with contaminated ground, whilst risk was expressed as a hazard quotient (HQ) for reproductive and/or developmental endpoints. Results show the largest changes occurred between 1987 and 1996 with total pesticide usage reduced by ca. 25%, exposure per unit of pesticide applied slightly increased, and a reduction in risk per unit exposure by factors of 1.4 to 5. Thereafter, there were no consistent changes in use between 1996 and 2012, with an increase in number of applications to each crop balanced by a decrease in average application rate. Exposure per unit of pesticide applied decreased consistently over this period such that values in 2012 for this metric were 48-65% of those in 1987, and there were further smaller decreases in risk per unit exposure. All aggregated hazard quotients were two to three orders of magnitude smaller than one, despite the inherent simplifications of assuming co-occurrence of exposure to all pesticides and additivity of effects. Hazard quotients at 1000 m were 5 to 30 times smaller than those at 100 m. There were clear signals of the impact of regulatory intervention in improving the fate and hazard profiles of pesticides over the period investigated