title: Feasibility of storing carbon dioxide on a tectonically active margin: New Zealand

authors: Field, Brad D.

subjects: carbon capture and storage

abstract: Screening of New Zealand's sedimentary basins indicates several gigatonnes of carbon dioxide storage capacity might be available. However, carbon dioxide storage is currently untested in New Zealand and it is likely that most theoretical storage capacity will be discounted once detailed assessments are made. New Zealand's position on an active Neogene plate boundary raises additional key factors that will affect final site selection. Issues specific to New Zealand's setting include 1) rapid facies changes, syndeposition and post-depositional structural events, particularly in regions close to the plate boundary; 2) rapid subsidence and high sedimentation rates leading to overpressured reservoirs and strong water drive in some structures, which will potentially result in injectivity issues, particularly in depleted fields; 3) mineralogically immature reservoir rocks requiring assessment of injected gas-rock reactions; 4) common occurrence of faults of various scales, requiring assessments of their sealing capacity and present stress fields; and 5) distinguishing induced seismicity from common natural seismicity. Some of these risk factors will also influence the relationship between social acceptance and the design of regulations. Despite the risks, hydrocarbon producing fields in Taranaki indicate that viable reservoir-seal pairs are likely to be present. Additionally, injection of small volumes of produced water and significant natural gas storage at the depleted Ahuroa Field, have not led to noticeable induced seismicity, though large volumes expected from a carbon dioxide injection project would likely require careful site assessment for seismic risk in some areas. Natural analogue and laboratory fluid rock experiments are investigating the effects of carbon dioxide injection on reservoir mineralogy and some effects can now be anticipated. Currently produced gas from New Zealand locally contains significant carbon dioxide (up to 44% carbon dioxide in the Taranaki region and up to 30% in the Canterbury Basin) and if new discoveries also have a high carbon dioxide content they may require processing before use, with disposal of carbon dioxide. Such a large gas discovery anywhere in New Zealand could therefore stimulate rapid deployment of CCS. It is highly likely viable storage sites exist, particularly away from the current plate boundary, though the site-specific nature of site assessment is particularly important in New Zealand's geological context.

text: Feasibility of storing carbon dioxide on a tectonically active margin: New Zealand Screening of New Zealand's sedimentary basins indicates several gigatonnes of carbon dioxide storage capacity might be available. However, carbon dioxide storage is currently untested in New Zealand and it is likely that most theoretical storage capacity will be discounted once detailed assessments are made. New Zealand's position on an active Neogene plate boundary raises additional key factors that will affect final site selection. Issues specific to New Zealand's setting include 1) rapid facies changes, syndeposition and post-depositional structural events, particularly in regions close to the plate boundary; 2) rapid subsidence and high sedimentation rates leading to overpressured reservoirs and strong water drive in some structures, which will potentially result in injectivity issues, particularly in depleted fields; 3) mineralogically immature reservoir rocks requiring assessment of injected gas-rock reactions; 4) common occurrence of faults of various scales, requiring assessments of their sealing capacity and present stress fields; and 5) distinguishing induced seismicity from common natural seismicity. Some of these risk factors will also influence the relationship between social acceptance and the design of regulations. Despite the risks, hydrocarbon producing fields in Taranaki indicate that viable reservoir-seal pairs are likely to be present. Additionally, injection of small volumes of produced water and significant natural gas storage at the depleted Ahuroa Field, have not led to noticeable induced seismicity, though large volumes expected from a carbon dioxide injection project would likely require careful site assessment for seismic risk in some areas. Natural analogue and laboratory fluid rock experiments are investigating the effects of carbon dioxide injection on reservoir mineralogy and some effects can now be anticipated. Currently produced gas from New Zealand locally contains significant carbon dioxide (up to 44% carbon dioxide in the Taranaki region and up to 30% in the Canterbury Basin) and if new discoveries also have a high carbon dioxide content they may require processing before use, with disposal of carbon dioxide. Such a large gas discovery anywhere in New Zealand could therefore stimulate rapid deployment of CCS. It is highly likely viable storage sites exist, particularly away from the current plate boundary, though the site-specific nature of site assessment is particularly important in New Zealand's geological context.

year: 2015

title: Physiological effects of aluminium in relation to diel pH changes on fish and kōura

authors: Fensham, Emily

subjects: Physiology

abstract: Alum (aluminium sulphate, Al₂(SO₄)₃) dosing is used to reduce eutrophication of lakes by sequestering phosphorus and preventing its uptake by phytoplankton for growth. When applied to water at circum-neutral pH, alum forms aluminium hydroxide (Al(OH)₃), a precipitate that is benign at environmentally relevant concentrations and moderate concentrations. However, at low and high pH, dissolved ionic aluminium species evolve which are known to be toxic to a range of aquatic organisms. In the Rotorua lakes, alum dosing occurs under circum-neutral pH (6–8) conditions, however, transiently elevated pH (10) conditions may occur due to algal uptake of carbon dioxide (CO₂) for photosynthesis. Under elevated pH, particulate Al(OH)₃ solubilises to form aluminate (Al(OH)₄⁻), which can interfere with osmoregulation and respiration. Similarly, at circumneutral pH, solid Al(OH)₃ predominates and is generally benign, but in high concentrations can irritate and damage gill tissue causing inflammation and excess mucus production which impairs oxygen uptake, CO₂ elimination, and ultimately causing death. The effects of aluminium under intermittent elevated pH on fish gill function, respiration rates, and metabolism have not yet been investigated.

This study investigated the impacts of aluminium on rainbow trout (Oncorhynchus mykiss), common bully (Gobiomorphus cotidianus), and kōura (Paranephrops planifrons) osmoregulation and respiration under diurnal pH cycles, through two experiments. The first being a dose exposure study whereby rainbow trout and kōura were exposed to alum derived aluminium at 2 mg L⁻¹ under diel pH cycling (pH 7–10) over 10 days. Measured parameters included haematocrit, haemoglobin, mean cell haemoglobin concentration (MCHC), and blood plasma osmolarity in rainbow trout and haemolymph osmolarity in kōura. A significant increase (Student’s t-test, P <0.05) in the mean cell haemoglobin concentration (MCHC) in the rainbow trout control group indicated erythrocyte swelling, suggesting a generalised stress induced response. However, other haematological variables such as plasma and haemolymph osmolarity, haematocrit and haemoglobin concentrations were not significantly different (Student’s t-test, P >0.05) between control and treatment groups. Histological examination of kōura and rainbow trout gill tissue was also conducted, with abnormalities observed within both the control and treatment groups for each species. However no significant differences (Kolomogorov-Smirnov, P >0.05) were observed between groups. It was concluded that organisms can physiologically compensate for aluminium induced stress and disturbance at the gills.

A second experiment utilised intermittent flow respirometry to determine mass specific metabolic oxygen consumption rates (MO₂) of rainbow trout, common bully, and kōura exposed to 2 mg Al L⁻¹ and diel pH fluctuations (pH 7–10) over 60 hours. It was expected that precipitation of dissolved aluminium onto the gill surface during pH transitions and/or binding of dissolved aluminium species would inhibit the respiratory gas exchange resulting in increased gill ventilation from hypoxic and hypercapnic conditions. There was a significant negative correlation (Pearson’s, r² = 0.34, P <0.0001) between pH and MO₂ possibly indicating kōura are sensitive to the experimental conditions. However, there were no consistent trends in differences between control and treatment groups for any of the tested species. Data interpretation was hindered by the necessity to exclude samples from the rainbow trout and common bully control groups due to aberrations in the oxygen sensor data. However, mean MO₂ was within expected ranges for rainbow trout and kōura, indicating that significant respiratory impacts were not occurring within the period of exposure. Although definitive conclusions could not be made regarding changes to MO₂ in response to aluminium and diel pH cycling, it is unlikely that acute impacts would result from these conditions in the natural environment.

From this research it is concluded that the combined impacts of aluminium and diel pH cycling are unlikely to cause acute osmoregulatory or respiratory impairment or cause death in kōura, common bully, or rainbow trout.

text: Physiological effects of aluminium in relation to diel pH changes on fish and kōura Alum (aluminium sulphate, Al₂(SO₄)₃) dosing is used to reduce eutrophication of lakes by sequestering phosphorus and preventing its uptake by phytoplankton for growth. When applied to water at circum-neutral pH, alum forms aluminium hydroxide (Al(OH)₃), a precipitate that is benign at environmentally relevant concentrations and moderate concentrations. However, at low and high pH, dissolved ionic aluminium species evolve which are known to be toxic to a range of aquatic organisms. In the Rotorua lakes, alum dosing occurs under circum-neutral pH (6–8) conditions, however, transiently elevated pH (10) conditions may occur due to algal uptake of carbon dioxide (CO₂) for photosynthesis. Under elevated pH, particulate Al(OH)₃ solubilises to form aluminate (Al(OH)₄⁻), which can interfere with osmoregulation and respiration. Similarly, at circumneutral pH, solid Al(OH)₃ predominates and is generally benign, but in high concentrations can irritate and damage gill tissue causing inflammation and excess mucus production which impairs oxygen uptake, CO₂ elimination, and ultimately causing death. The effects of aluminium under intermittent elevated pH on fish gill function, respiration rates, and metabolism have not yet been investigated.

This study investigated the impacts of aluminium on rainbow trout (Oncorhynchus mykiss), common bully (Gobiomorphus cotidianus), and kōura (Paranephrops planifrons) osmoregulation and respiration under diurnal pH cycles, through two experiments. The first being a dose exposure study whereby rainbow trout and kōura were exposed to alum derived aluminium at 2 mg L⁻¹ under diel pH cycling (pH 7–10) over 10 days. Measured parameters included haematocrit, haemoglobin, mean cell haemoglobin concentration (MCHC), and blood plasma osmolarity in rainbow trout and haemolymph osmolarity in kōura. A significant increase (Student’s t-test, P <0.05) in the mean cell haemoglobin concentration (MCHC) in the rainbow trout control group indicated erythrocyte swelling, suggesting a generalised stress induced response. However, other haematological variables such as plasma and haemolymph osmolarity, haematocrit and haemoglobin concentrations were not significantly different (Student’s t-test, P >0.05) between control and treatment groups. Histological examination of kōura and rainbow trout gill tissue was also conducted, with abnormalities observed within both the control and treatment groups for each species. However no significant differences (Kolomogorov-Smirnov, P >0.05) were observed between groups. It was concluded that organisms can physiologically compensate for aluminium induced stress and disturbance at the gills.

A second experiment utilised intermittent flow respirometry to determine mass specific metabolic oxygen consumption rates (MO₂) of rainbow trout, common bully, and kōura exposed to 2 mg Al L⁻¹ and diel pH fluctuations (pH 7–10) over 60 hours. It was expected that precipitation of dissolved aluminium onto the gill surface during pH transitions and/or binding of dissolved aluminium species would inhibit the respiratory gas exchange resulting in increased gill ventilation from hypoxic and hypercapnic conditions. There was a significant negative correlation (Pearson’s, r² = 0.34, P <0.0001) between pH and MO₂ possibly indicating kōura are sensitive to the experimental conditions. However, there were no consistent trends in differences between control and treatment groups for any of the tested species. Data interpretation was hindered by the necessity to exclude samples from the rainbow trout and common bully control groups due to aberrations in the oxygen sensor data. However, mean MO₂ was within expected ranges for rainbow trout and kōura, indicating that significant respiratory impacts were not occurring within the period of exposure. Although definitive conclusions could not be made regarding changes to MO₂ in response to aluminium and diel pH cycling, it is unlikely that acute impacts would result from these conditions in the natural environment.

From this research it is concluded that the combined impacts of aluminium and diel pH cycling are unlikely to cause acute osmoregulatory or respiratory impairment or cause death in kōura, common bully, or rainbow trout.

year: 2022

title: Behind the label: Complexities of identifying Māori whānau in an away from home hospital transfer

authors: Masters-Awatere, Bridgette

subjects: Māori whānau

abstract: This paper highlights two methodological issues that arose for a group of Māori researchers during the first few months of a Māori CoRE funded project. The issues were in relation to defining 1) the evolving construction of Māori whānau in New Zealand, and 2) an away from home hospital transfer. Through the process of reflexive practice about our knowledge constructs the research team highlight some of the complexities that we as indigenous researchers had to navigate when working within a cultural context. We describe the details of the Hospital Transfers project and reflect on the learning experienced during the pilot interview phase of a three year project.

text: Behind the label: Complexities of identifying Māori whānau in an away from home hospital transfer This paper highlights two methodological issues that arose for a group of Māori researchers during the first few months of a Māori CoRE funded project. The issues were in relation to defining 1) the evolving construction of Māori whānau in New Zealand, and 2) an away from home hospital transfer. Through the process of reflexive practice about our knowledge constructs the research team highlight some of the complexities that we as indigenous researchers had to navigate when working within a cultural context. We describe the details of the Hospital Transfers project and reflect on the learning experienced during the pilot interview phase of a three year project.

year: 2017