title: Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid

authors: Leach, Meto T.

subjects: platinum

abstract: The reactions of cis-[PtCl₂L₂] [L = PPh₃, PMe₂Ph or L₂ = Ph₂P(CH₂)₂PPh₂ (dppe)] with endo-8-camphanylphosphonic acid (CamPO₃H₂) and Ag₂O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O₃PCam)L₂]. The X-ray crystal structure of [Pt(O₃PCam)(PPh₃)₂]•₂CHCl₃ shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh₃ ligands. This allows the O₃P–CH₂ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh₃ and dppe derivatives, which contain inequivalent phosphine ligands in their ³¹P NMR spectra. These findings are backed up by theoretical calculations on the PPh₃ and PPhMe₂ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh₃ and PPhMe₂ complexes. The X-ray crystal structure of CamPO₃H₂ is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.

text: Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid The reactions of cis-[PtCl₂L₂] [L = PPh₃, PMe₂Ph or L₂ = Ph₂P(CH₂)₂PPh₂ (dppe)] with endo-8-camphanylphosphonic acid (CamPO₃H₂) and Ag₂O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O₃PCam)L₂]. The X-ray crystal structure of [Pt(O₃PCam)(PPh₃)₂]•₂CHCl₃ shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh₃ ligands. This allows the O₃P–CH₂ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh₃ and dppe derivatives, which contain inequivalent phosphine ligands in their ³¹P NMR spectra. These findings are backed up by theoretical calculations on the PPh₃ and PPhMe₂ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh₃ and PPhMe₂ complexes. The X-ray crystal structure of CamPO₃H₂ is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.

year: 2011

title: Spatiotemporal variability of hydrology in Moanatuatua drained peatland and its influence on CO₂ emissions and surface oscillations

authors: Glover-Clark, Georgia

abstract: Drained agricultural peatlands can be highly productive but problematic ecosystems, including releasing substantial carbon dioxide (CO₂) emissions to the atmosphere as peat decomposes. The ongoing and permanent loss of soil carbon from drained peatlands worldwide represents approximately 5% of global anthropogenic CO₂ emissions, which are accompanied by long-term irreversible subsidence of the peatland surface, affecting land management. Hydrology, particularly with respect to water table depth and soil moisture content, is seen as an important control on soil physical and hydraulic properties, reversible and irreversible subsidence, and biogeochemical processes including the emission of CO₂. The globally unique peatlands of Aotearoa New Zealand, including in their drained state, have a relatively limited research history when compared to those in the Northern Hemisphere. As such, we lack a comprehensive understanding of hydrological regimes and how they act to influence environmental effects. 

To improve our understanding, I have conducted a spatially and temporally detailed hydrological investigation over a one-year period within Moanatuatua drained peatland in the Waikato region of Aotearoa New Zealand. My primary objective was to determine the controls on spatiotemporal variation in hydrology and its influence on CO₂ emissions and oscillations in peat surface elevation, by comparing and contrasting two dairy farms with similar management practices but different drainage designs and drainage histories. Using a combination of manual and automatic measurement techniques, water table depth (relative water level, RWL) and soil moisture (volumetric moisture content, VMC) were measured, as well as peat physical properties, water vapour and CO₂ fluxes, and peatland surface oscillations (PSO).

Both RWL and VMC were spatially and temporally variable. Spatial patterns of RWL were very similar between sites, indicating limited control of drainage design during a climatically warm and dry year. The deeper drains at Site 2 did, however, appear to increase RWL depth. Temporal patterns of RWL and VMC at both sites responded to water storage changes largely driven by the water balance components of precipitation and evaporation. Evident hydrological differences between sites appeared to be predominantly influenced by soil physical properties, which led to more variable VMC at Site 1 and more variable RWL at Site 2. Lower VMC at Site 1 initiated hydrophobicity in surface peat over an extended drought period, while Site 2 was little affected. Deep capillary zones at both sites indicated subsurface moisture redistribution, the depths of which far exceeded those in published literature. A dependent relationship between RWL and VMC was only apparent when peat was near saturation, otherwise displaying considerable long and short-term hysteresis caused by different and delayed responses of RWL and VMC to rainfall.

CO₂ emissions at both sites were primarily influenced by VMC and were not at all correlated with RWL, raising questions for the continued use of RWL as a proxy to estimate near-surface moisture conditions in carbon studies. Soil temperatures also influenced emissions, and appeared to be the dominant control only when VMC was high. The ability of soil at Site 2 to retain more moisture during an extended summer drought meant that ecosystem respiration (ER) was not constrained by water limitations to the extent it was at Site 1. As gross primary production was very similar at the two sites, the ongoing differences in ER initiated in late January led to accumulated emissions over the full year of 5.6 t C ha-1 greater than at Site 2. 

Over a 10 month period, PSO at both sites were in the upper range of values published in international literature, and were between 2.5 – 3.5 times greater than the annual average irreversible subsidence rate for the Waikato region. PSO was correlated with rainfall, RWL and VMC, each of which had varying influence during the measurement period. Considerable hysteresis was measured in the relationship between surface elevation and RWL, distinctly separating drying and wetting cycles. Short term hysteresis was likely induced by a delay between equilibration of effective stresses within the peat matrix before a change in surface elevation incurred. Higher bulk density at Site 2 acted to reduce the magnitude of PSO, a phenomenon that was also noted at both sites adjacent to drainage channels. 

Overall, this research has revealed the importance of hydrology, drainage history, and their effects on peat physical properties, each of which strongly influenced CO₂ emissions and PSO, raising questions about their continued use for agriculture.

text: Spatiotemporal variability of hydrology in Moanatuatua drained peatland and its influence on CO₂ emissions and surface oscillations Drained agricultural peatlands can be highly productive but problematic ecosystems, including releasing substantial carbon dioxide (CO₂) emissions to the atmosphere as peat decomposes. The ongoing and permanent loss of soil carbon from drained peatlands worldwide represents approximately 5% of global anthropogenic CO₂ emissions, which are accompanied by long-term irreversible subsidence of the peatland surface, affecting land management. Hydrology, particularly with respect to water table depth and soil moisture content, is seen as an important control on soil physical and hydraulic properties, reversible and irreversible subsidence, and biogeochemical processes including the emission of CO₂. The globally unique peatlands of Aotearoa New Zealand, including in their drained state, have a relatively limited research history when compared to those in the Northern Hemisphere. As such, we lack a comprehensive understanding of hydrological regimes and how they act to influence environmental effects. 

To improve our understanding, I have conducted a spatially and temporally detailed hydrological investigation over a one-year period within Moanatuatua drained peatland in the Waikato region of Aotearoa New Zealand. My primary objective was to determine the controls on spatiotemporal variation in hydrology and its influence on CO₂ emissions and oscillations in peat surface elevation, by comparing and contrasting two dairy farms with similar management practices but different drainage designs and drainage histories. Using a combination of manual and automatic measurement techniques, water table depth (relative water level, RWL) and soil moisture (volumetric moisture content, VMC) were measured, as well as peat physical properties, water vapour and CO₂ fluxes, and peatland surface oscillations (PSO).

Both RWL and VMC were spatially and temporally variable. Spatial patterns of RWL were very similar between sites, indicating limited control of drainage design during a climatically warm and dry year. The deeper drains at Site 2 did, however, appear to increase RWL depth. Temporal patterns of RWL and VMC at both sites responded to water storage changes largely driven by the water balance components of precipitation and evaporation. Evident hydrological differences between sites appeared to be predominantly influenced by soil physical properties, which led to more variable VMC at Site 1 and more variable RWL at Site 2. Lower VMC at Site 1 initiated hydrophobicity in surface peat over an extended drought period, while Site 2 was little affected. Deep capillary zones at both sites indicated subsurface moisture redistribution, the depths of which far exceeded those in published literature. A dependent relationship between RWL and VMC was only apparent when peat was near saturation, otherwise displaying considerable long and short-term hysteresis caused by different and delayed responses of RWL and VMC to rainfall.

CO₂ emissions at both sites were primarily influenced by VMC and were not at all correlated with RWL, raising questions for the continued use of RWL as a proxy to estimate near-surface moisture conditions in carbon studies. Soil temperatures also influenced emissions, and appeared to be the dominant control only when VMC was high. The ability of soil at Site 2 to retain more moisture during an extended summer drought meant that ecosystem respiration (ER) was not constrained by water limitations to the extent it was at Site 1. As gross primary production was very similar at the two sites, the ongoing differences in ER initiated in late January led to accumulated emissions over the full year of 5.6 t C ha-1 greater than at Site 2. 

Over a 10 month period, PSO at both sites were in the upper range of values published in international literature, and were between 2.5 – 3.5 times greater than the annual average irreversible subsidence rate for the Waikato region. PSO was correlated with rainfall, RWL and VMC, each of which had varying influence during the measurement period. Considerable hysteresis was measured in the relationship between surface elevation and RWL, distinctly separating drying and wetting cycles. Short term hysteresis was likely induced by a delay between equilibration of effective stresses within the peat matrix before a change in surface elevation incurred. Higher bulk density at Site 2 acted to reduce the magnitude of PSO, a phenomenon that was also noted at both sites adjacent to drainage channels. 

Overall, this research has revealed the importance of hydrology, drainage history, and their effects on peat physical properties, each of which strongly influenced CO₂ emissions and PSO, raising questions about their continued use for agriculture.

year: 2020

title: Moehewa: Death, lifestyle & sexuality in the Maori World

authors: Nikora, Linda Waimarie

abstract: Customary death ritual and traditional practice have continued for the Māori (indigenous) people of Aotearoa/New Zealand, despite intensive missionary incursion and the colonial process. This paper critically considers what occurs when the deceased is different, in a most significant way. What happens when you die – and you are Māori and any one, or a combination, of the following: a queen, takatāpui,[1] butch, like that, gay, she-male, lesbian, transsexual, a dyke, intersex, tomboy, kamp, drag, homosexual, or just queer? Who remembers you and how? Same sex relationships today are still discouraged or denied, although traditional chant and Māori visual narratives record such liaisons and erotic experience as joyously normal (Te Awekotuku, 2005). And yet some people choose to remain in the closet. In this paper, we present three case studies, and invite the reader to reflect with us on mourning rituals or tangi – Māori death rites, in a same sex relationship, or for a gay, lesbian or transsexual family member. In this way, we open up a space for dialogue about such matters in our intimate and kin communities.

text: Moehewa: Death, lifestyle & sexuality in the Maori World Customary death ritual and traditional practice have continued for the Māori (indigenous) people of Aotearoa/New Zealand, despite intensive missionary incursion and the colonial process. This paper critically considers what occurs when the deceased is different, in a most significant way. What happens when you die – and you are Māori and any one, or a combination, of the following: a queen, takatāpui,[1] butch, like that, gay, she-male, lesbian, transsexual, a dyke, intersex, tomboy, kamp, drag, homosexual, or just queer? Who remembers you and how? Same sex relationships today are still discouraged or denied, although traditional chant and Māori visual narratives record such liaisons and erotic experience as joyously normal (Te Awekotuku, 2005). And yet some people choose to remain in the closet. In this paper, we present three case studies, and invite the reader to reflect with us on mourning rituals or tangi – Māori death rites, in a same sex relationship, or for a gay, lesbian or transsexual family member. In this way, we open up a space for dialogue about such matters in our intimate and kin communities.

year: 2016