Measuring Ozone Deposition to the Ocean Surface and Assessing its Biogeochemical Controls

Dry deposition of ozone to the sea surface represents a significant portion of global tropospheric ozone loss. It introduces considerable uncertainty in global models due to limited understanding of the reactivity of iodide and organic material in the sea surface towards ozone. This is particularly true of organic material due to its variable composition. This thesis details ozone flux and associated measurements at and around the Penlee Point Atmospheric Observatory (PPAO) on the UK south coast from 2018 until 2021 where coastal ozone flux was calculated via eddy covariance. Monthly median deposition velocity was 0.007 – 0.033 cm s−1 across all fieldwork, similar to the values reported from ship-based measurements: 0.009 – 0.034 cm s−1. Iodide and dissolved organic carbon (DOC) concentrations in the water within the flux footprint were ~50 to ~100 nmol dm−3 and 1.3 – 2.2 mg dm−3. While iodide increased to a peak in July (coinciding with phytoplankton blooms), DOC conversely peaked in November. These measurements were used with a 1-layer and a 2-layer model to compare deposition observations to predictions. The 1-layer model in the absence of DOC reactivity typically gave values closest to observations and showed a similarly strong variation with friction velocity. Inclusion of the DOC-ozone reaction with a rate constant of 3.7 × 10−6 dm3 mol−1 s−1 caused both models to overestimate, but also mimic some variation between months suggesting its contribution was overestimated, but still important. Liquid chromatography-mass spectrometry was used to identify compounds in the water near the PPAO. Double bond equivalence decreased following exposure to 500 ppbv ozone, while dicarboxylic acid concentrations increased, potentially due to unsaturated fatty acid ozonolysis. Several dicarboxylic acid concentrations in PPAO samples fell from November – April, similarly to DOC concentrations. The potential for some introduction of dicarboxylic acids as contaminants from the sampling method remains a possibility

"Pesky gNATs":investigating the feasibility of a novel computerised CBT intervention for adolescents with anxiety and/or depression in a Tier 3 CAMHS setting

AbstractIncreasingly, evidence suggests that computerized Cognitive Behavioural Therapy (cCBT) is effective at reducing adolescent anxiety and depression for young people in the general population or those ‘at risk’. However, less is known about the acceptability, feasibility and effectiveness of cCBT for adolescents with clinically significant levels of impairment. This study aimed to investigate the feasibility of using a novel cCBT intervention, ‘Pesky gNATs’, with adolescents aged between 13–18 years with anxiety and/or depression who met the criteria for specialist mental health services. Eleven participants were recruited from a Tier 3 child and adolescent mental health service (CAMHS). Recruitment, attendance and retention rates were recorded and qualitative feedback about the benefits and disadvantages of completing cCBT were obtained during the final session. In addition, a number of outcome measures were completed pre- and post- intervention to assess reliable and clinically significant change. The intervention was very brief comprising of just seven sessions. Participants showed high recruitment and retention rates. All participants who started the intervention completed it. All described the programme as useful and the majority identified several benefits. Four of 11 participants demonstrated reliable reductions in symptoms of depression and anxiety and six of 11 showed decreases in parent-reported symptoms of anxiety and depression following the seven-session intervention. This study demonstrates the acceptability and feasibility of using cCBT in a Tier 3 CAMHS setting. Further research is required to investigate the effect of Pesky gNATs on anxiety and depression in other Tier 3 settings.</jats:p