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The real-time detection of trace species is key to a wide range of applications such as on-line chemical process analysis, medical diagnostics, identification of environmentally toxic species and atmospheric pollutant sensing. There is a growing demand for suitable techniques that are not only sensitive, but also simple to operate, fast and versatile. Most currently available techniques, such as spectrophotometry, are neither sensitive enough nor fast enough for kinetic studies, whilst other techniques are too complex to be operated by the non-specialist. This thesis presents two techniques that have been developed for and applied to liquid-phase analysis, with supercontinuum (SC) radiation used for liquid-phase absorption for the first time. Firstly, supercontinuum cavity enhanced absorption spectroscopy (SC-CEAS) was used for the kinetic measurement of chemical species in the liquid phase using a linear optical cavity. This technique is simple to implement, robust and achieves a sensitivity of 9.1 × 10−7 cm−1 Hz−1/2 at a wavelength of 550nm for dye species dissolved in water. SC-CEAS is not calibration-free and for this purpose a second technique, a time-resolved variant called broadband cavity ring-down spectroscopy (BB-CRDS), was successfully developed. Use of a novel single-photon avalanche diode (SPAD) array enabled the simultaneous detection of ring-down events at multiple spectral positions for BB-CRDS measurements. The performance of both techniques is demonstrated through a number of applications that included the monitoring of an oscillating (Belousov-Zhabotinsky) reaction, detection of commercially important photoluminescent metal complexes (europium(III)) at trace level concentration, and the analysis of biomedical species (whole and lysed blood) and proteins (amyloids). Absorption spectra covering the entire visible wavelength range can be acquired in fractions of a second using sample volumes measuring only 1.0mL. Most alternative devices capable of achieving similar sensitivity have, up until now, been restricted to single wavelength measurements. This has limited speed and number of species that can be measured at once. The work presented here exemplifies the potential of these techniques as analytical tools for research scientists, healthcare practitioners and process engineers alike.

Air pollution and global climate change are important environmental issues that affect our society. Deeper understanding of atmospheric chemistry is required to understand these problems and to develop effective control strategies. Environmental chambers have been used for the past few decades to study atmospheric chemistry and investigate processes leading to secondary pollutant formation. This thesis work provides two different high sensitivity real time cavity enhance absorption spectroscopy (CEAS) instruments to detect NO3 radical and NO2/ glyoxal for environmental chamber study. These CEAS instruments can monitor these species with high sensitivity (in sub-ppb concentrations), with good selectivity, and with high spatial resolution in real time and in situ.Environmental chamber studies using CEAS instruments include NO3 behavior and reaction kinetics between NO3 and amine; sources and sinks for oxides of nitrogen (NOx) in the atmospheric photooxidation reactions; glyoxal uptake by secondary organic aerosol (SOA) under dry and humid conditions and glyoxal formation from the photooxidation of aromatic and isoprene. These studies provide insightful data in atmospheric processes and lead to a better understanding of the atmospheric system, which will eventually extend to environmental policy. This thesis is only a part of my research work. For more information about my other work, including cavity ring down spectroscopy studies for peroxy radical, aerosol optical extinction, transparent thin and time of flight mass spectrometry studies for the initial steps of ozone and alkenes reaactions, please refer to my PhD thesis in Chemistry department, UC-Riverside.

Background. Large-scale agricultural industry is estimated to account for about half of the increase in pesticide use in developing countries. Few data exist regarding the effects of pesticide exposure in corporate agriculture on neurobehavioral development in young children. This preliminary study assesses the association between risk factors for pesticide exposure and neurobehavioral development of young children in a major cut-flower growing region of Ecuador. Methods. Children aged 3--61 months residing in three communities were administered the Ages and Stages Questionnaire, and height, weight and hemoglobin measures were obtained. Targeted developmental tests were administered to a sub-set of children. Information was collected on maternal health, maternal work, home environment, and child health and behavior characteristics. Multiple linear and logistic regressions were conducted to assess the impact of community-level, prenatal, and early childhood exposure. Results. Overall, 263 children were included in the analyses. High frequencies of developmental delay were observed in the population. Residence in high exposure communities was associated with lower scores on gross motor, fine motor, and socio-individual skills. Maternal employment in the flower industry during pregnancy was negatively associated with communication and fine motor skills and was also associated with poor visual acuity in infants. Among older children, contact with irrigation water was negatively associated with fine motor, problem solving, and visual motor integration skills. Longer time spent playing outdoors was associated with worse gross and fine motor and problem solving skills. In contrast, current maternal employment in the flower industry was associated with higher communication and problem solving skills. Conclusions. We found differences in neurobehavioral development based on the community of residence of the child. Results suggest an association between prenatal exposure to pesticides through maternal employment in the flower industry and delayed development in infants. Results also suggest that risk factors for pesticide exposure in the residential environment affect development in older children, with contact with irrigation water of particular concern. Corporate agriculture may increase risk of neurodevelopmental delay through prenatal pesticide exposure and environmental contamination while indirectly promoting healthy development, perhaps by providing health care to workers' families, relatively higher salaries, and daycare options.