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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC Riverside Electronic Theses and Dissertations (2019)

Polycyclic aromatic hydrocarbons (PAHs) are a class of compounds of environmental and public health concern because of their toxicity and environmental ubiquity that will be further exacerbated by increasing anthropogenic pollution. In situ bioremediation is a common cleanup technique for PAH-contaminated soils because it is considered to be cost-effective and environmentally-friendly. However, PAHs are often bound to nonpolar soil domains and become resistant to microbial degradation, the primary PAH removal pathway. This dissertation addresses these limitations by evaluating bioremediation-enhancement technologies such as biosurfactant amendment, bioaugmentation, and phytoremediation to increase PAH bioavailability and/or soil microbial activity. The use of biosurfactants to increase PAH bioavailability has the potential to be an environmental alternative to synthetic surfactants. Therefore, rhamnolipid biosurfactant was compared to Brij-35 surfactant in two soils contaminated with 14C-pyrene that were also bioaugmented with a PAH-degrading microbe, Mycobacterium vanbaalenii PYR-1. The effect of the surfactants and bioaugmentation on PAH biodegradation and soil microbial community dynamics was evaluated. The addition of Brij-35 increased 14C-pyrene mineralization in both soils, but the rhamnolipid biosurfactant inhibited PAH degradation in a dose-dependent manner, which was likely due to preferential utilization of the biosurfactant as an easier carbon source by the degrading microorganisms. The bioaugmentation of M. vanbaalenii PYR-1 resulted in efficient 14C-pyrene dissipation. Using 16S rRNA analysis, it was determined that the pyrene biodegradation was associated with changes in the soil microbial communities. The addition of pyrene resulted in a large increase in Bacillus, a genus associated with PAH degradation. However, the addition of rhamnolipid biosurfactant decreased the abundance of Bacillus microorganisms, which was reflected in 14C-pyrene mineralization. These bioremediation-enhancement technologies were further assessed in a phytoremediation setting in PAH-contaminated soil from a shooting range site due to the accumulation of clay target fragments. Bermudagrass and switchgrass enhanced soil enzyme activity and PAH biodegradation. The bioaugmentation of M. vanbaalenii PYR-1 enhanced high-molecular-weight PAH biodegradation. The decrease in PAH concentrations was also reflected in lettuce seed germination toxicity assays. Overall, this research highlights the importance of physical and biological mechanisms in the evaluation and implementation of in situ bioremediation-enhancement technologies for successful PAH remediation of contaminated soils.

    Cover page: Effects of in situ Bioremediation Strategies on the Biodegradation of Polycyclic Aromatic Hydrocarbons and Microbial Community Dynamics in SoilCreative Commons 'BY-NC-SA' version 4.0 license
    • Article
    Working Papers (1999)
      Cover page: Child Care Subsidies and the Employment of Welfare Recipients
      • Article
      • Peer Reviewed
      UC Riverside Previously Published Works (2021)
      Water treatment and reuse initiatives are essential to combat declining water supplies in a changing climate, especially in arid and semi-arid regions. Pollution of water resources intensifies the search for strategies to provide water for potable and non-potable reuse that mitigates detrimental ecological and human health effects. Fipronil and synthetic pyrethroids are common urban-use insecticides that exert aquatic toxicity at trace levels and have been often found in urban surface streams. In this study, samples were collected from the 182 ha Prado Wetlands in Southern California for seven months to assess the occurrence of fipronil and its degradation products as well as pyrethroids (bifenthrin and cyfluthrin) in water, sediment, and plants in a 4.45 ha vegetated surface flow constructed wetland (CW). Concentration-based removal values and changes in mass flux were calculated to determine the efficacy of CW treatment. Observed water concentrations were further used to calculate toxic units for the invertebrates Hyalella azteca and Chironomus dilutus. Pesticide concentrations in water, sediment, and plant samples consistently decreased during passage through the CW at all time points. Removal values for fipronil desulfinyl, fipronil sulfide, fipronil, fipronil sulfone, bifenthrin, and cyfluthrin were 100%, 99.7-100%, 57.8-88.1%, 75.6-100%, 74.7-100%, and 36.6-82.2%, respectively, and there was a general net deposition of pesticides into CW compartments. Toxic unit values decreased in every instance for both aquatic invertebrates. Settling of contaminated particles, adsorption to sediment, plant uptake or adsorption, and subsequent degradation contributed to the effective removal of these urban-use insecticides, which highlights the potential of CWs for protecting urban water quality.
        Cover page: Removal of urban-use insecticides in a large-scale constructed wetland
        • Article
        • Peer Reviewed
        UC Riverside Previously Published Works (2019)
        Urban-use pesticides present a unique risk to non-target organisms in surface aquatic systems because impervious pavement facilitates runoff that may lead to serious contamination and ensuing aquatic toxicity. Fipronil is an insecticide used at high rates in urban environments, especially in regions such as California. This compound and its biologically active degradation products have been detected in urban runoff drainage and downstream surface water bodies at concentrations exceeding toxicity thresholds for sensitive aquatic invertebrates, necessitating a better understanding of the runoff sources and causes of this contamination at sites of application. In this study, we evaluated sorption of fipronil, fipronil desulfinyl, fipronil sulfide, and fipronil sulfone in urban dust, soil, and concrete, matrices commonly associated with the perimeter of a residential home. Samples were also collected from five single family homes treated with fipronil in Riverside, California, for five months to determine the occurrence of fipronil and its degradates in runoff water, urban dust, soil, and on concrete surfaces. Statistical analysis was performed to determine which urban matrices contributed more significantly to the contaminant levels in runoff water. Freundlich sorption coefficients for fipronil and its degradation products in dust were 3- to 9-fold greater than their values in soil. Fipronil and its degradates were detected in 100% of runoff samples and their presence was observed in dust, soil, and concrete wipe samples for 153 d after the treatment. Linear regression analysis showed that concrete surfaces were a primary source of all four compounds to runoff, and loose dust on concrete pavement also served as an important contributor. This study represents the first comprehensive investigation of the sources and causes for surface runoff contamination by fipronil and its degradation products. Findings highlight the importance to reduce fipronil residues on concrete surfaces through improved application methods and other mitigation practices.
          Cover page: Fiproles in urban surface runoff: Understanding sources and causes of contamination
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2024)
          The appropriate use of human biomonitoring data to model population chemical exposures is challenging, especially for rapidly metabolized chemicals, such as agricultural chemicals. The objective of this study is to demonstrate a novel approach integrating model predicted dietary exposures and biomonitoring data to potentially inform regulatory risk assessments. We use lambda-cyhalothrin as a case study, and for the same representative U.S. population in the National Health and Nutrition Examination Survey (NHANES), an integrated exposure and pharmacokinetic model predicted exposures are calibrated to measurements of the urinary metabolite 3-phenoxybenzoic acid (3PBA), using an approximate Bayesian computing (ABC) methodology. We demonstrate that the correlation between modeled urinary 3PBA and the NHANES 3PBA measurements more than doubled as ABC thresholding narrowed the acceptable tolerance range for predicted versus observed urinary measurements. The median predicted urinary concentrations were closer to the median measured value using ABC than using current regulatory Monte Carlo methods.
            Cover page: A Novel Approach to Integrate Human Biomonitoring Data with Model Predicted Dietary Exposures: A Crop Protection Chemical Case Study Using Lambda-Cyhalothrin.
            • Article
            • Peer Reviewed
            UC San Francisco Previously Published Works (2013)

            Background & aims

            Some women with inflammatory bowel disease require therapy with tumor necrosis factor (TNF) antagonists during pregnancy. It is not clear whether these drugs are transferred to the fetus via the placenta and then cleared, or whether structurally different TNF antagonists have different rates of transfer.

            Methods

            We studied 31 pregnant women with inflammatory bowel disease receiving infliximab (IFX, n = 11), adalimumab (ADA, n = 10), or certolizumab (CZP, n = 10). Serum concentrations of the drugs were measured at birth in the mother, infant, and in cord blood, and then monthly in the infant until the drugs were undetectable. Drug concentrations in the cord and the infant at birth were compared with those of the mother.

            Results

            Concentrations of IFX and ADA, but not CZP, were higher in infants at birth and their cords than in their mothers. The levels of CZP in infants and their cords were less than 2 μg/mL. The median level of IFX in the cord was 160% that of the mother, the median level of ADA in the cord was 153% that of the mother, and the median level of CZP in the cord was 3.9% that of the mother. IFX and ADA could be detected in the infants for as long as 6 months. No congenital anomalies or serious complications were reported.

            Conclusions

            The TNF antagonists IFX and ADA are transferred across the placenta and can be detected in infants at birth; the drugs were detected in infants up to 6 months after birth. CZP has the lowest level of placental transfer, based on levels measured in cords and infants at birth, of the drugs tested.
              Cover page: Placental Transfer of Anti–Tumor Necrosis Factor Agents in Pregnant Patients With Inflammatory Bowel Disease
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