The ocean is both a source and a sink for atmospheric methyl bromide (CH3Br) and methyl chloride (CH3Cl). It plays a significant role in their global biogeochemical cycling. In response to the Montreal Protocol, the atmospheric CH3Br is declining and the saturation state of CH3Br in the surface ocean is becoming more positive. Results from two large-scale transect studies in the eastern Pacific and the eastern Atlantic suggest that the ocean became near equilibrium with atmospheric CH3Br in 2010. Results from a "top-down" two-box model indicate that, if the remaining anthropogenic emissions are eliminated, atmospheric CH3Br is likely to drop to the pre-industrial level and the ocean would become a net source to atmospheric CH3Br. This study also represents an effort to improve current understanding of the oceanic and atmospheric budgets of CH3Cl. The global net sea-to-air flux of CH3Cl was estimated at 335 (210 ? 480) Gg yr-1 with improved parameterizations on the solubility, seasonal saturation anomaly ? (sea surface temperature, wind speed) relationships and the use of an updated parameterization on gas transfer velocity. For the first time, we estimated the gross oceanic emission and gross oceanic uptake rates of CH3Cl in the surface ocean, which was 700 (490 to 920) Gg yr^-1 and -370 (-440 to -280) Gg yr^-1, respectively. The ocean accounts for 10 - 19 % in the global CH3Cl emission and 6 - 9 % in its global sinks. Methane (CH4) is a potent greenhouse gas, which has a warming potential 72 times that of carbon dioxide over a 20 year time horizon. Gas hydrates are the largest CH4 reservoir in the planet. How much CH4 is transported from marine gas hydrates to the atmosphere is under debate. In this study, we investigated CH4 fluxes over three deepwater hydrocarbon seeps in the northern Gulf of Mexico using continuous air-sea flux measurements. Extrapolating the highest daily flux from this study to other deepwater seeps in the northern Gulf of Mexico suggests that CH4 fluxes to the atmosphere from the deepwater hydrocarbon seeps in this region are an insignificant source to atmospheric CH4 budget.

LD2668 .T4 1948 A4 / Master of Science

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The depletion of fossil fuel resources, pollution concerns and the challenge of energy security are driving the search for renewable energy sources. The use of lignocellulosic plant biomass as an energy source is increasing in the United Kingdom and worldwide. In the UK, up to 0.35MHa (6% of total arable land) may be planted with perennial bioenergy crops by 2020 in order to meet renewable energy and CO2 reduction targets. Several plant species that produce high biomass from low inputs have been identified. The most promising for the UK climate are the genus Miscanthus, a perennial rhizomatous grass which can grow up to 3.5m in a year, and short rotation coppice (SRC) willow (Salix spp.), plantations of which can remain viable for up to 30 years. Although bioenergy crops are perceived as “carbon neutral”, changes in land use can have a wider impact on atmospheric composition than through CO2 alone. This study compares vegetation fluxes of methyl halides (CH3Br and CH3Cl) and biogenic volatile organic compounds (BVOCs) from perennial bioenergy crops and annual arable crops at three sites in the UK. Methyl halides are the most abundant natural vectors of bromine and chlorine into the stratosphere and play an important role in stratospheric ozone destruction. BVOCs affect atmospheric oxidising capacity and are a major precursor to the formation of ozone and secondary organic aerosols in the troposphere. Although terrestrial vegetation is an important source of these trace gases there are very few previous measurements of these reactive gases from bioenergy crops. This study describes measurements conducted at two SRC willow sites in Scotland, and one site in England planted with adjacent perennial bioenergy crops and annual arable crops, to quantify and characterise natural methyl halide and BVOC fluxes from vegetation. Measurements were conducted with branch chambers, using static enclosure techniques to measure methyl halide fluxes and dynamic enclosures to measure BVOCs such as isoprene and -pinene. Fluxes were calculated from the concentration difference between background/inlet samples and after enclosure/outlet samples. Methyl halide concentrations were determined by sampling gas from static enclosures followed by analysis using an oxygen-doped GC-ECD with a custom-built pre-concentration unit. Samples for BVOC analysis were collected onto adsorbent tubes and a thermal desorption GC-MS was used to determine BVOC concentrations. Potentially influential environmental variables such as photosynthetically active radiation (PAR), total solar radiation, air temperature, soil temperature, internal chamber temperature and soil moisture were recorded in parallel to the enclosures to determine their potential relationships to fluxes. Long-term environmental data was also available from on-site or nearby weather stations. Long-term measurements were carried out for 2 1 2 years at a site in Lincolnshire, England where adjacent fields are planted with Miscanthus, SRC willow and annual arable crops (wheat and oilseed rape crop rotation). Vegetation measurements were made almost every month throughout the period, with more intensive measurements such as full diurnal cycle carried out during the summer. Ten sampling points are sampled in each field and semi-diurnal measurements are taken regularly. Long-term measurements were also carried out at two sites in Scotland planted with SRC willow, one in Arnot, Perth & Kinross which was sampled for a year and one in East Grange, Fife which was sampled for half a year. Up to 30 sampling points were employed in Arnot and another 10 in East Grange. The bioenergy crops and wheat emitted low fluxes of methyl halides in comparison to the oilseed rape. Mean annual net fluxes of CH3Br and CH3Cl from Miscanthus were 1.8 ng g (dry weight)-1 h-1 and 11 ng g-1 h-1, respectively. At the three willow sites, mean annual net fluxes of CH3Br and CH3Cl ranged between 0.6 - 1.7 ng g-1 h-1, and 1.7 - 12 ng g-1 h-1, respectively. Negligible fluxes of methyl halides were measured from wheat but oilseed rape was found to emit large fluxes of methyl halides with mean annual net fluxes of CH3Br and CH3Cl of 20 ng g-1 h-1and 144 ng g-1 h-1, respectively. The largest BVOC fluxes were measured from SRC willow at the Brattleby site, with high mean annual net fluxes of isoprene (77 μ g g-1 h-1), α -pinene (46 g μg-1 h-1), β -pinene (5.5 μ g g-1 h-1), limonene (3.7 μ g g-1 h-1) and δ -3-carene (11 μ g g-1 h-1). However, mean annual net BVOC fluxes measured at Arnot and East Grange were much lower. High fluxes of - pinene were measured from Miscanthus in 2010 (giving a mean annual net flux of 65 μ g g-1 h-1) but no other significant BVOC fluxes were distinguished. Negligible fluxes of isoprene were measured from wheat but fluxes of monoterpenes were high with mean annual net fluxes of 65 μ g g-1 h-1 and 25 μg g-1 h-1 for α -pinene and limonene, respectively. No significant fluxes of BVOCs were measured from the oilseed rape. All fluxes demonstrated a strong seasonal trend with higher emissions during the summer growing season and low to zero emissions over winter. The high spatial variability was captured by sampling from many points in each field. Some diurnal measurements exhibited a clear pattern of higher emissions during the day and low to zero emissions at night. Some positive correlations between fluxes and environmental variables such as PAR and air temperature were observed. An experiment carried out on willow cuttings in the greenhouse found no clear increase or decrease in fluxes of BVOCs in response to N fertiliser treatment, instead fluxes were found to vary significantly with some of the observed environmental variables. UK estimates were derived by extrapolating measured fluxes using the current respective land cover areas for Miscanthus and SRC willow. Estimated UK annual fluxes of CH3Br and CH3Cl from Miscanthus were 0.01Mgy-1 and 0.05Mgy-1, respectively and from SRC willow were 0.06Mgy-1 and 0.4Mgy-1, respectively, accounting for a very small percentage of total global annual turnover of CH3Br and CH3Cl. Estimated UK annual fluxes of the BVOCs isoprene and α -pinene from Miscanthus were 0.01Mgy-1 and 0.4Mgy-1, respectively and from SRC willow were 3Mgy-1 and 1Mgy-1, respectively. Future planting of SRC willow to meet the UKs energy needs could lead to a potential annual isoprene flux of 150 MgMgy-1.

Thesis (Ph.D.) OGI School of Science & Engineering at OHSU, January 2007. / Abstract: leaf x. Includes bibliographical references (leaves 124-138).

Intracellular transportation is an essential cellular event controlling neuronal development, morphology, function and survival. Kinesin-1 is the molecular motor conveying cargo along microtubule by utilizing the chemical energy from ATP hydrolysis. This motor consists of two heavy chains and two light chains. Both heavy and light chains are responsible for cargo bindings. There are three kinesin-1 heavy chains in eukaryotic cells. Kif5a and Kif5c are neuronal specific, while Kif5b is ubiquitously expressed. Kif5b carries various cargos essential for neuronal functions, and the early embryonic death of Kif5b null mice suggests the importance of Kif5b in vivo. N-methyl-d-aspartate receptors (NMDARs) are glutamate elicited channel, which is permeable to calcium and crucial for synaptic plasticity in the central nervous system. NMDARs are heteromeric assemblies consisting of NR1, NR2 and NR3 subunits. These transmembrane subunits contain three parts. Other than the transmembrane domain, the extracellular domain serves as the ligand binding site while the intracellular domain interacts with various partners regulating downstream signaling and receptor trafficking. Synaptic NMDAR activation regulates synaptic plasticity, while extrasynaptic NMDAR activation leads to excitotoxicity. In this project, I find that kinesin-1 directly interacts with NMDAR subunit, NR1, NR2A and NR2B in vivo. NMDAR colocalizes with kinesin-1 in the cell body and neurites. By GST-pull-down assays with different Kif5b fragments, the cytoplasmic domains of NR1, NR2A and NR2B are found to directly bind with Kif5b via a Kif5b C-terminal region independent of kinesin light chains. To examine the role of Kif5b in NMDAR trafficking, dominant negative Kif5b fragments are expressed in cell lines together with NR1-1a and GFP-NR2B. Overexpression of dominant negative Kif5b significantly disrupts GFP-NR2B forward trafficking and prevents it from entering into Golgi apparatus. Furthermore, the surface NR1 and NR2B levels are significantly reduced whilst the NR2A levels are not affected in Kif5b+/- mice in which the Kif5b protein level is reduced by 50% compared with the wild-type littermates. Consistent with this observation, the NR1 and NR2B levels are decreased in fractions containing synaptosomal membrane but not the one containing only postsynaptic densities, suggesting that the extrasynaptic NMDAR levels are affected in Kif5b+/- mice. NMDARs are highly permeable to calcium while activated, thereby activating neuronal nitric oxide synthases (nNOS) to produce nitric oxide (NO). It is found that NMDA triggered calcium influx is perturbed in Kif5b+/- neurons, while the synaptic NMDA receptor mediated calcium influx is normal. In Kif5b+/- slices, the production of NO reduces significantly. Calcium ionophore, A23187, rescue this NO defect, indicating insufficient supply of calcium as the main contribution to this defect. Therefore, Kif5b-dependent extrasynaptic localization of NMDA receptors mediates calcium influx upon NMDA stimulation and controls NO production. In the summary, above results suggest kinesin-1 as a novel motor involving in NMDA receptor trafficking. This interaction may contribute to the extrasynaptic distribution of NMDARs. By regulating NO production through interaction with NMDARs, Kif5b may mediate neuronal survival in cerebral ischemia and certain aggressive behaviors. This provides a novel target for therapy development against stroke and schizophrenia. / published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy