The world’s oceans are witnessing a surge in plastic pollution, a consequence of human activities and the growing urbanization of coastal regions. Urban estuaries are complex habitats that are especially good at trapping sediment, carbon, and pollutants, such as plastics. However, our understanding of the extant of plastic accumulation within estuarine sediments remains limited. I determined the first quantification of the total amount of microplastics (>5 mm) in Puget Sound, WA – a heavily urbanized estuary – and identified deposition hotspots related to current hydrodynamics. To measure plastic concentrations, I collected both shoreline and shipboard sediment samples and density extracted microplastics using an NaI solution. Extracted plastics were counted, sized, and categorized under a microscope. To complement these plastic analyses, energy of the environment was determined using both grain size analysis and extraction of current velocities from LiveOcean, a hydrodynamic model of Puget Sound. I found that plastic concentrations are the highest near land-water interfaces, which are correlated with human population. The dominant source of microplastics came from fibers shed from clothing, giving a well-sorted particle size distribution. Furthermore, using the plastic concentration data I developed a predictive model of plastic distribution that relies on Puget Sound currents and could be adapted for other estuarine systems. Providing a comprehensive analysis of the sources and sinks of microplastics in main basin Puget Sound that can be used to inform preventative management on the negative impacts of urban waste.

Marine sediments are a critical carbon reservoir, locking both inorganic and organic carbon in sediments for thousands to millions of years. This carbon is released in part through the production of methane at methane seeps, places where methane gas is emitted from the seafloor. In this study, I characterized source differences and quantified the amount of inorganic and organic carbon stored in Puget Sound sediments at a methane seep site. A multicorer collected sediment samples at two sites: one at the Alki Point methane vent field and a control site within the Main Basin of Puget Sound. The sediment cores were subsampled in 2 cm sections downcore and stored for later analysis. Analyses included physical parameters (grain size, percent loss on ignition (% LOI), and 210Pb sediment dating) and geochemical parameters (Total Organic Carbon (TOC), Total Carbon (TC), del 13C TOC, del 13C TC). Both sites were silt-dominated (Alki = 37 microns, Control = 30 microns), with a well-mixed layer 15 cm thick. Organic content (% LOI) was high at both sites (Alki = 7.5%, Control = 6.9%). Likewise, TOC and TC showed trends of increased organic material at the methane seep site. Isotope data indicate that methane-influenced sites have lighter del 13C. Given the amount of carbon they store and the potential for these reservoirs to be disturbed by bottom trawling, deep sea mining, and other invasive human activities, understanding how carbon is cycled through marine sediments is critical for preserving these reservoirs and adequately factoring their role in the carbon cycle into global climate models.

Birth asphyxia is the inability of a newborn to begin and maintain breathing. Twenty-three percent of neonatal deaths globally are caused by birth asphyxia. Birth asphyxia results in a neurological injury called hypoxic ischemic encephalopathy (HIE). Rapid HIE screening within six hours after birth is crucial to identify neonates at risk. Unfortunately, the diagnostic equipment is impractical for low resource settings because it is costly ($20/test and $5,000 for equipment) and requires technical staff, that are in short supply, to operate. We hypothesize that a cost-effective device can be developed for HIE analysis. pHast Cam quickly screens for birth asphyxia and HIE in infants via a paper-based blood pH sensor. The device combines an inexpensive pH sensitive dye, a smartphone camera, and a fixture that controls the imaging environment to quickly identify acidosis from samples. A low-cost paper-based strip is made with a water-soluble resin doped with a pH-sensitive dye, bromothymol blue (BTB), and a membrane to filter out red blood cells. The fixture removes lighting variation. The smartphone camera records the pH indicator image, and an algorithm captures, reduces noise, and accesses color change. pHast Cam incorporates four features: 1) accurate assessment of acidity within 0.05 pH units, 2) require only a few microliters of sample, 3) use electrical hardware and software only from the smartphone, and 4) affordability. At this stage, we have achieved a regressive linear model that predicts buffered solution acidity (y=-589.32x+4684.05 R2=0.9857), with 95% confidence interval of 0.04 pH units. In the future, we will transition from measuring buffered solutions to blood-plasma. Ultimately, we expect pHastCam to screen for birth asphyxia, and other acid-base disorders, by quantifying plasma pH in neonates so that timely therapeutic interventions and plans to address long-term complications may occur.