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© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hawco, N. J., Yang, S.-C., Pinedo-Gonzalez, P., Black, E. E., Kenyon, J., Ferron, S., Bian, X., & John, S. G. Recycling of dissolved iron in the North Pacific Subtropical Gyre. Limnology and Oceanography, 67(11), (2022): 2448-2465, https://doi.org/10.1002/lno.12212., The importance of iron as a limiting nutrient in the open ocean is widely recognized, but there is substantial uncertainty about the rate that it cycles in the marine environment. Here, we combine measurements from the water column, sediment traps, and incubations to constrain Fe turnover during summer at Station ALOHA in the North Pacific Subtropical Gyre. Using low levels of 57Fe–58Fe double spike, measured with high precision by multi-collector inductively coupled plasma mass spectrometry, we find Fe uptake rates of 30–60 pM d−1 throughout the euphotic zone. Dissolved Fe turnover times are estimated at 10–15 d in the mixed layer and 1–3 d near the deep chlorophyll maximum. Aerosol Fe supply inferred from a thorium isotope mass balance indicates that the dissolved Fe residence time is approximately 6 months in the upper euphotic zone (0–75 m), relative to external sources, and 2 months in the lower euphotic zone (75–150 m). To reconcile these observations, the average Fe atom must be recycled over 25 times at Station ALOHA in both the upper and lower euphotic zones (an “Fe ratio” equal to 0.04 and 0.03, respectively), a level of conservation that has only been documented in Fe-limited regions thus far. At steady state, this scenario requires an aerosol Fe solubility of 4.5%, which is similar to dissolution experiments from Pacific Ocean aerosols. Our results suggest that the oligotrophic ocean is capable of recycling iron efficiently even when these ecosystems are not demonstrably iron-limited., This work was also supported by the Simons Foundation (602538 and 823167 to N.J.H., 329108 to S.G.J) and National Science Foundation grants 2022969 to N.J.H. and 1911990 to S.F.

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical Oceanography at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2022., Radioactive isotopes act as nuclear clocks that are utilized to trace and measure rates of chemical, biological, physical, and geological oceanographic processes. This thesis seeks to utilize both artificial (e.g., released from anthropogenic sources) and natural radioisotopes as tracers within the Pacific Ocean basin. Artificial radioisotopes released as a result of the 2011 Fukushima Daiichi nuclear power plants accident have the potential to negatively impact human and environmental health. This study evaluates 137Cs, 90Sr, and 129I concentrations in seawater off the coast of Japan, reconciles the sources of contaminated waters, and assesses the application of 137Cs/90Sr, 129I/137Cs, and 129I/90Sr as oceanic tracers. The analysis of activity ratios suggests a variety of sources, including ongoing sporadic and independent releases of radiocontaminants. Though decreasing, concentrations remain elevated compared to preaccident levels. Future planned releases of stored water from the reactor site may affect the surrounding environment; and thus, continued efforts to understand the distribution and fate of these radionuclides are warranted. Naturally-occurring radioisotopes (e.g., the 238U-234Th series used in this thesis) can give insight into surface export and remineralization of particulate organic carbon (POC) and trace metals (TMs). POC and TMs play a vital role in regulating the biological carbon pump (BCP), which in turn helps to moderate atmospheric CO2 levels by transporting carbon to the deep ocean, where it can be sequestered on timescales of centuries to millennia. Through this thesis we utilize the 238U:234Th disequilibrium method throughout the GEOTRACES GP15 Pacific Meridional Transect in order o provide basin-scale estimates of POC export and remineralization. There is only limited, recent use of this method to constrain TM fluxes, and as such this study also seeks to further develop this method for use in understanding TM cycling through comparative, Funding sources for this thesis include the Gordon and Betty Moore Foundation, the Deerbrook Charitable Trust, NSF OCE award no. 1356630 and no. 1735445, and the NSF GRFP.

Dataset: Suspended particles from in situ pumps, Suspended particulate total carbon concentration, organic carbon concentration, inorganic carbon concentration, nitrogen concentration, and bulk isotope composition (C and N) from in situ McLane pumps in June 2019 at station ALOHA during cruise KM1910. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/853048, NSF Division of Ocean Sciences (NSF OCE) OCE-1911831, NSF Division of Ocean Sciences (NSF OCE) OCE-1911990

Dataset: Particulate Th-234 Activities, This dataset includes particulate Th-234 collected using large volume McLane pumps (LVPs) as part of the EAGER chief scientist training cruise at Station ALOHA in the subtropical North Pacific gyre in June 2019. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/854150, NSF Division of Ocean Sciences (NSF OCE) OCE-1911831, NSF Division of Ocean Sciences (NSF OCE) OCE-1911990

Dataset: Particulate Thorium-234 Flux, This dataset includes particulate Th-234 collected with surface-tethered sediment traps at Station ALOHA as part of the EAGER chief scientist training cruise (KM1910) in the subtropical North Pacific gyre in June 2019. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/854241, NSF Division of Ocean Sciences (NSF OCE) OCE-1911831, NSF Division of Ocean Sciences (NSF OCE) OCE-1911990

Dataset: Sinking particles from traps, Phosphorus, carbon (total and organic), and nitrogen flux and bulk isotope composition (C and N) from 3-day pit trap deployments in June 2019 at station ALOHA during cruise KM1910. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/852779, NSF Division of Ocean Sciences (NSF OCE) OCE-1911831, NSF Division of Ocean Sciences (NSF OCE) OCE-1911990

Background: The English National Health Service's (NHS) Stop Smoking Services (SSSs) constitute one of the most highly developed behavioural support programmes in the world. However, there is significant variation in success rates across the approximately 150 services, some of which may be due to variation in practice. This study aimed to assess these differences in practice. Methods: Two online surveys were administered. All commissioners (people who purchase services for the NHS) and managers (those who run the services) of NHS SSSs in England were invited to participate. Items included details of current practices and services provided, what informed the commissioning of SSSs, what targets were included within service specifications and whether the types of treatment model to be delivered were specified. Results: Both surveys had a response rate of 35%, with 50 commissioners and 58 managers participating. There were no significant differences between the characteristics of the Primary Care Trusts (PCTs) from which commissioners and managers responded to this survey and those PCTs from which there was no response. Managers reported that the treatment model most frequently offered by SSSs was one-to-one (98%). A total of 16% of managers reported that some approved medications were not available as first-line treatments. Just over one third (38%) of commissioners reported consulting national guidelines or best evidence to inform local commissioning. Almost one third (30%) of commissioners reported that they specified the types of stop smoking interventions to be delivered by the providers. Conclusions: A substantial part of commissioning of Stop Smoking Services in England appears to take place without adequate consultation of evidence-based guidelines or specification of the service to be provided. This may account for at least some of the variation in success rates.

Kenyon, J. A., Buesseler, K. O., Casacuberta, N., Castrillejo, M., Otosaka, S., Masqué, P., ... Sanial, V. (2020). Distribution and evolution of Fukushima Dai-ichi derived 137Cs, 90Sr, and 129I in surface seawater off the coast of Japan. Environmental Science & Technology, 54(23), 15066-15075. https://doi.org/10.1021/acs.est.0c05321