Sonnichsen Frederick

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Sonnichsen
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Frederick
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  • Preprint
    Laser induced breakdown spectroscopy for heavy metal detection in a sand matrix
    ( 2016-09-21) Michel, Anna P. M. ; Sonnichsen, Frederick
    Sediments in many locations, including harbors and coastal areas, can become contaminated and polluted, for example, from anthropogenic inputs, shipping, human activities, and poor waste management. Sampling followed by laboratory analysis has been the traditional methodology for such analysis. In order to develop rapid methodologies for eld analysis of sediment samples, especially for metals analyses, we look to Laser Induced Breakdown Spectroscopy as an option. Here through laboratory experiments, we demonstrate that dry sand samples can be rapidly analyzed for the detection of the heavy metals chromium, zinc, lead, and copper. We also demonstrate that cadmium and nickel are detectable in sand matrices at high concentrations.
  • Article
    Development of the channelized optical system II for in situ, high-frequency measurements of dissolved inorganic carbon in seawater
    (American Chemical Society, 2024-03-25) Ringham, Mallory C. ; Wang, Zhaohui Aleck ; Sonnichsen, Frederick ; Lerner, Steven A. ; McDonald, Glenn ; Pfeifer, Jonathan A.
    This study describes the development of the CHANnelized Optical System II (CHANOS II), an autonomous, in situ sensor capable of measuring seawater dissolved inorganic carbon (DIC) at high frequency (up to ∼1 Hz). In this sensor, CO2 from acidified seawater is dynamically equilibrated with a pH-sensitive indicator dye encapsulated in gas-permeable Teflon AF 2400 tubing. The pH in the CO2 equilibrated indicator is measured spectrophotometrically and can be quantitatively correlated to the sample DIC. Ground-truthed field data demonstrate the sensor’s capabilities in both time-series measurements and surface mapping in two coastal sites across tidal cycles. CHANOS II achieved an accuracy and precision of ±5.9 and ±5.5 μmol kg–1. The mean difference between traditional bottle and sensor measurements was −3.7 ± 10.0 (1σ) μmol kg–1. The sensor can perform calibration in situ using Certified Reference Materials (CRMs) to ensure measurement quality. The coastal time-series measurements highlight high-frequency variability and episodic biogeochemical shifts that are difficult to capture by traditional methods. Surface DIC mapping shows multiple endmembers in an estuary and highlights fine-scale spatial variabilities of DIC. The development of CHANOS II demonstrates a significant technological advance in seawater CO2 system sensing, which enables high-resolution, subsurface time-series, and profiling deployments.