title: Oxidation of surface sediment: effects of disturbance depth and seawater flow speed

authors: Vopel, Kay

subjects: cohesive sediment

abstract: Periodic disturbance of surface sediment is a natural feature of marine environments. Following exposure to oxygenated seawater, the disturbed sediment oxidises leading to the recovery of its surface chemistry. Despite its importance for the ecology of the sediment–water interface, the dynamics of this recovery is not well known. We studied the effects of disturbance depth and seawater flow speed on the oxidation of estuarine cohesive sediment in a laboratory flume with microelectrodes. We removed surface sediment to 2 depths (5 and 50 mm) and then observed changes in sediment O₂ distribution and consumption over 1 h under conditions of slow and fast flow (3.5 and 7.5 cm s–1). Measurements were repeated 1 d later. The consumption of O₂ in the treated sediments reached a ‘quasi stable state’ within 7 h (50 mm depth) and 16 h (5 mm depth) characterised by very slow changes due to slow oxidation of reduced solids. Faster flow increased the rate at which sediment from 50 mm depth oxidised but not that of the sediment from 5 mm depth. After 20 to 24 h, sediments disturbed to 50 and 5 mm depths still differed in O₂ distribution and consumption, both from each other and from the pre-treatment sediment. Differences in the response of pore water O₂ distribution to an abrupt increase in flow speed (3.5 to 7.5 cm s–1) were also still evident at this time. Our measurements confirmed the results of previous theoretical analyses in that they indicate that the duration of the recovery of the surface sediment chemistry from disturbance and the chemical properties of the recovering sediment are controlled by the kinetics of solute and solid oxidation. Oxidation of reduced solids in disturbed sediment can result in a characteristic chemical signature at the sediment surface that lasts in the order of at least days.

text: Oxidation of surface sediment: effects of disturbance depth and seawater flow speed Periodic disturbance of surface sediment is a natural feature of marine environments. Following exposure to oxygenated seawater, the disturbed sediment oxidises leading to the recovery of its surface chemistry. Despite its importance for the ecology of the sediment–water interface, the dynamics of this recovery is not well known. We studied the effects of disturbance depth and seawater flow speed on the oxidation of estuarine cohesive sediment in a laboratory flume with microelectrodes. We removed surface sediment to 2 depths (5 and 50 mm) and then observed changes in sediment O₂ distribution and consumption over 1 h under conditions of slow and fast flow (3.5 and 7.5 cm s–1). Measurements were repeated 1 d later. The consumption of O₂ in the treated sediments reached a ‘quasi stable state’ within 7 h (50 mm depth) and 16 h (5 mm depth) characterised by very slow changes due to slow oxidation of reduced solids. Faster flow increased the rate at which sediment from 50 mm depth oxidised but not that of the sediment from 5 mm depth. After 20 to 24 h, sediments disturbed to 50 and 5 mm depths still differed in O₂ distribution and consumption, both from each other and from the pre-treatment sediment. Differences in the response of pore water O₂ distribution to an abrupt increase in flow speed (3.5 to 7.5 cm s–1) were also still evident at this time. Our measurements confirmed the results of previous theoretical analyses in that they indicate that the duration of the recovery of the surface sediment chemistry from disturbance and the chemical properties of the recovering sediment are controlled by the kinetics of solute and solid oxidation. Oxidation of reduced solids in disturbed sediment can result in a characteristic chemical signature at the sediment surface that lasts in the order of at least days.

year: 2010

title: The synthesis and metal ion catalysed hydrolysis of methyl 4,5-diaminopentanoate

authors: Beresford, Geoffrey Derrick

abstract: The diamino acid ester, methyl 4, 5-diaminopentanoate has been prepared for the first time. The successful five step synthesis starting from 4-hydroxybutanoic acid lactone, and two other possible pathways via ethyl 3-formylpropanoate, are described. 
pKₐ values for 4,5-diaminopentanoic acid dihydrochloride and its a methyl ester dihydrochloride (determined by potentiometric titration at 25°C and I= 0.10molℓ⁻¹) are discussed in relation to those for other 1,2-diamines.
Stability constants of Cu(II) complexes of 4,5-diaminopentanoic acid and its methyl ester were evaluated from potentiometric titration data by the program SCOGS on a PDP 11/70 computer. Both compounds form high stability constant 1:1 and 1:2 complexes with Cu(II). (For 4,5-diaminopentanoic acid log K₁ = 10.94, log K₂ = 9.40 and for methyl 4,5-diaminopentanoate log K₁ = 9.84, log K₂ = 8.51, at 25°C and I= 0.10molℓ⁻¹). A variety of protonated complexes were also present at lower pH. 
pH-stat and spectrophotometric investigations showed that in the alkaline hydrolysis of methyl 4,5-diaminopentanoate, the simple Bᴀс2 reaction is slow and masked by a competing, extremely rapid, pair of intramolecular aminolysis (lactamisation) reactions. These involve competition between five and six membered lactam ring closure. Overall constants of the order 10³ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹ are observed.
The Cu(II) catalysed hydrolysis of methyl 4,5-diaminopentanoate was studied at constant pH using a pH-stat. The kinetics of hydrolysis of solutions containing a 1:2 mole ratio of Cu(II): ester are consistent with the two consecutive second order (pseudo-first-order at constant pH) reactions (1) and (2) (where E is the ester and A⁻ the anion, of 4 ,5-diaminopentanoic acid).
CuE₂²⁺ + OH⁻ → CuEA⁺ + CH₃OH 	1
CuEA⁺ + OH⁻ → CUA₂ + CH₃OH 		2
The relative values for the two rate constants obtained (k (CuE₂²⁺) = 2.41ℓmol⁻¹s⁻¹ and k (CuEA⁺) = 0.80ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹) can be explained by charge and statistical effects. The value of k(CuEA⁺) was confirmed independently from studies on solutions containing a 2.5:1:4 mole ratio of Cu(II): ester: acid. The value of k(CuEen²⁺) = 0.96ℓmol⁻¹s⁻¹ obtained from solutions containing Cu(II): ester: 1,2-diaminoethane = 2.5:1:4 is approximately k(CuE₂²⁺)/2 as expected statistically. 1:1 Solutions of Cu(II) and methyl 4,5-diaminopentanoate disproportionate, so no values for k(CuE²⁺) could be measured.
The absolute values for the Cu(II) catalysed rate constants are discussed in comparison with those for methyl 2,3-diaminopropanoate and other diamino acid esters. The results for methyl 4,5-diaminopentanoate can be explained by the attenuation of inductive and positive charge effects of the metal ion by the additional methylene groups of the methyl 4,5-diaminopentanoate alkyl chain. Direct methoxycarbonyl-metal ion interaction, presumably absent in methyl 4,5-diaminopentanoate must, therefore, be unimportant in the Cu(II) catalysed hydrolysis of methyl 2,3-diarninopropanoate.

text: The synthesis and metal ion catalysed hydrolysis of methyl 4,5-diaminopentanoate The diamino acid ester, methyl 4, 5-diaminopentanoate has been prepared for the first time. The successful five step synthesis starting from 4-hydroxybutanoic acid lactone, and two other possible pathways via ethyl 3-formylpropanoate, are described. 
pKₐ values for 4,5-diaminopentanoic acid dihydrochloride and its a methyl ester dihydrochloride (determined by potentiometric titration at 25°C and I= 0.10molℓ⁻¹) are discussed in relation to those for other 1,2-diamines.
Stability constants of Cu(II) complexes of 4,5-diaminopentanoic acid and its methyl ester were evaluated from potentiometric titration data by the program SCOGS on a PDP 11/70 computer. Both compounds form high stability constant 1:1 and 1:2 complexes with Cu(II). (For 4,5-diaminopentanoic acid log K₁ = 10.94, log K₂ = 9.40 and for methyl 4,5-diaminopentanoate log K₁ = 9.84, log K₂ = 8.51, at 25°C and I= 0.10molℓ⁻¹). A variety of protonated complexes were also present at lower pH. 
pH-stat and spectrophotometric investigations showed that in the alkaline hydrolysis of methyl 4,5-diaminopentanoate, the simple Bᴀс2 reaction is slow and masked by a competing, extremely rapid, pair of intramolecular aminolysis (lactamisation) reactions. These involve competition between five and six membered lactam ring closure. Overall constants of the order 10³ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹ are observed.
The Cu(II) catalysed hydrolysis of methyl 4,5-diaminopentanoate was studied at constant pH using a pH-stat. The kinetics of hydrolysis of solutions containing a 1:2 mole ratio of Cu(II): ester are consistent with the two consecutive second order (pseudo-first-order at constant pH) reactions (1) and (2) (where E is the ester and A⁻ the anion, of 4 ,5-diaminopentanoic acid).
CuE₂²⁺ + OH⁻ → CuEA⁺ + CH₃OH 	1
CuEA⁺ + OH⁻ → CUA₂ + CH₃OH 		2
The relative values for the two rate constants obtained (k (CuE₂²⁺) = 2.41ℓmol⁻¹s⁻¹ and k (CuEA⁺) = 0.80ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹) can be explained by charge and statistical effects. The value of k(CuEA⁺) was confirmed independently from studies on solutions containing a 2.5:1:4 mole ratio of Cu(II): ester: acid. The value of k(CuEen²⁺) = 0.96ℓmol⁻¹s⁻¹ obtained from solutions containing Cu(II): ester: 1,2-diaminoethane = 2.5:1:4 is approximately k(CuE₂²⁺)/2 as expected statistically. 1:1 Solutions of Cu(II) and methyl 4,5-diaminopentanoate disproportionate, so no values for k(CuE²⁺) could be measured.
The absolute values for the Cu(II) catalysed rate constants are discussed in comparison with those for methyl 2,3-diaminopropanoate and other diamino acid esters. The results for methyl 4,5-diaminopentanoate can be explained by the attenuation of inductive and positive charge effects of the metal ion by the additional methylene groups of the methyl 4,5-diaminopentanoate alkyl chain. Direct methoxycarbonyl-metal ion interaction, presumably absent in methyl 4,5-diaminopentanoate must, therefore, be unimportant in the Cu(II) catalysed hydrolysis of methyl 2,3-diarninopropanoate.

year: 1977

title: Ora Kainga Rua: Experiences of Kura Kaupapa Māori Graduates

authors: Waller, Arianna Leigh Mana

subjects: indigenous auto ethnography

abstract: There is a wealth of indigenous scholarship examining the impacts of imperialist policies and ideologies on the learning identities of indigenous students. However, within the New Zealand context, there is a lack of literature which focuses solely on the experiences and aspirations of total immersion students to tertiary education settings. 
Using Kaupapa Māori and auto ethnography this thesis privileges the student voice by investigating the transitional experiences of four female kura Kaupapa Māori graduates into mainstream settings particularly their transition to the University of Waikato. 
The thesis argues that there are two main spaces of synergy between an indigenous research paradigm and auto ethnography. The first is the criticality of the “self” in the work, without a sharp separation between the researcher and the subject (dual meaning intended). The second is the shared modality and intentional use of storytelling as a method. By combining insights from in-depth interviews with the researcher’s life story, the thesis identified the coping mechanisms the participants employed and the services The University of Waikato provides that were utilised to help them transition into a new educational setting. 
The participants’ experiences demonstrate that the unique cultural educational experiences of kura Kaupapa Māori differ significantly from the educational and environmental experiences offered at University. The participants’ narratives demonstrated that the clear sense of identity gained from the kura Kaupapa Māori context gave them the inner strength to cope with these differences. In addition to their strong sense of Māori identity, the main coping mechanisms that the students drew on, was the wealth of institutional knowledge that family members and role models provided of the university context as past students and current staff members. The benefits that these students experienced can be strengthened by building stronger relationships between Māori total immersion schools, the wider Māori community and universities ensuring that Māori total immersion students are able to access the academic and institutional knowledge they need to succeed. 
Furthermore, the thesis argues that the kura Kaupapa Māori movement can deliver more for their students if they do not shut out the Pākehā world but rather teach their students to walk between and within the two worlds. In order to better understand this balancing act, the lived experiences of immersion students requires more research, particularly as more and more kura graduates transition into Aotearoa New Zealand tertiary settings.

text: Ora Kainga Rua: Experiences of Kura Kaupapa Māori Graduates There is a wealth of indigenous scholarship examining the impacts of imperialist policies and ideologies on the learning identities of indigenous students. However, within the New Zealand context, there is a lack of literature which focuses solely on the experiences and aspirations of total immersion students to tertiary education settings. 
Using Kaupapa Māori and auto ethnography this thesis privileges the student voice by investigating the transitional experiences of four female kura Kaupapa Māori graduates into mainstream settings particularly their transition to the University of Waikato. 
The thesis argues that there are two main spaces of synergy between an indigenous research paradigm and auto ethnography. The first is the criticality of the “self” in the work, without a sharp separation between the researcher and the subject (dual meaning intended). The second is the shared modality and intentional use of storytelling as a method. By combining insights from in-depth interviews with the researcher’s life story, the thesis identified the coping mechanisms the participants employed and the services The University of Waikato provides that were utilised to help them transition into a new educational setting. 
The participants’ experiences demonstrate that the unique cultural educational experiences of kura Kaupapa Māori differ significantly from the educational and environmental experiences offered at University. The participants’ narratives demonstrated that the clear sense of identity gained from the kura Kaupapa Māori context gave them the inner strength to cope with these differences. In addition to their strong sense of Māori identity, the main coping mechanisms that the students drew on, was the wealth of institutional knowledge that family members and role models provided of the university context as past students and current staff members. The benefits that these students experienced can be strengthened by building stronger relationships between Māori total immersion schools, the wider Māori community and universities ensuring that Māori total immersion students are able to access the academic and institutional knowledge they need to succeed. 
Furthermore, the thesis argues that the kura Kaupapa Māori movement can deliver more for their students if they do not shut out the Pākehā world but rather teach their students to walk between and within the two worlds. In order to better understand this balancing act, the lived experiences of immersion students requires more research, particularly as more and more kura graduates transition into Aotearoa New Zealand tertiary settings.

year: 2016