title: Regional Assessment of Soil Change in the Southwest Pacific

authors: Baldock, J.A.

abstract: The Southwest Pacific region includes the 22 island nations of the Pacific1, New Zealand and Australia (Figure 15.1). The landscapes of the region are very diverse ranging from a large continental land mass through to tens of thousands of small islands across the enormous expanse of the southwest Pacific Ocean. There are extensive ancient flat lands through to some of the youngest and most tectonically active landscapes on the planet. Temperature and rainfall ranges are large because of the breadth of latitudes and elevations. As a consequence, the soils of the region are also diverse. The strongly weathered soils in humid tropical areas and the vast expanses of old soils across the Australian continent are particularly susceptible to disturbance and this is where some of the more intractable problems of soil management occur today.

text: Regional Assessment of Soil Change in the Southwest Pacific The Southwest Pacific region includes the 22 island nations of the Pacific1, New Zealand and Australia (Figure 15.1). The landscapes of the region are very diverse ranging from a large continental land mass through to tens of thousands of small islands across the enormous expanse of the southwest Pacific Ocean. There are extensive ancient flat lands through to some of the youngest and most tectonically active landscapes on the planet. Temperature and rainfall ranges are large because of the breadth of latitudes and elevations. As a consequence, the soils of the region are also diverse. The strongly weathered soils in humid tropical areas and the vast expanses of old soils across the Australian continent are particularly susceptible to disturbance and this is where some of the more intractable problems of soil management occur today.

year: 2015

title: Biogeochemistry of denitrifying bioreactors to enhance phosphorus removal from agricultural subsurface drainage

authors: Perera, Maddhumage Gimhani Nuwanthika

abstract: Degradation of water quality due to nutrient over-enrichment has become a global environmental concern. In Aotearoa, agricultural pollution of freshwaters by nutrients is increasing. Therefore, strategies need to be implemented to minimize nutrient pollution in surface waters. Denitrifying bioreactors (DBRs) are a prominent edge-of-field treatment technology to mitigate surface water nitrate loadings from agricultural subsurface drainage. Recent studies have identified that subsurface drainage can also contribute to the loss of phosphorus from agricultural soil. Therefore, this thesis investigates the potential of DBRs to incorporate iron-based materials to sequester phosphorus and reduce pollution of waterways.
There is some evidence suggesting low-level phosphorus removal by woodchip bioreactors alone. However, it is inevitable that woodchips alone do not abiotically remove phosphorus due to the incompatibility between the surface charge of wood at neutral-to-acidic pH values. In this study, raw pinus radiata, and, thermally modified pyrolyzed woodchips were employed for surface modification, with view to enhancing P binding in DBRs.
We were mindful in the design of material functionalization to avoid complicated preparation steps, exotic or harmful reagents, and impractical particle sizes to ensure compatibility for large-scale applications in the agricultural landscape. Results indicated that the functionalization of wood media successfully inversed the surface charge, leading to a net positive charge within the favorable range for phosphorus adsorption under reactor-specific conditions (pH 5.5 − 6). The maximum adsorption capacity of functionalized wood and functionalized biochar corresponded to 65.8 mg g-1 and 31.4 mg g-1, respectively, comparing well to values reported in the literature.
DBRs operate under varying hydraulic conditions, which results in variable flow rates, nutrient concentrations, redox status, pH, and many other variables that affect the operation of the bioreactor. The stability of iron hydr(oxide) composites is expected to be sensitive to some of these conditions, especially acidic and anaerobic conditions, which favor dissolution of iron hydr(oxide)s and therefore could adversely affect P removal. Furthermore, there are other likely products of reduced Fe2+ and orthophosphate (HPO42-) that could form under the conditions anticipated. Therefore, the biogeochemical environment in the DBR was characterized to understand the stability of iron hydr(oxide)s and their ability to subsequently remove of phosphorus.
To date, there have been only limited investigations into the stability of iron hydr(oxide)s under real-world bioreactor conditions, and functionalisation studies often neglect the impact of oscillating redox conditions on the stability of Fe-based adsorbents. In light of this, bench-scale woodchip bioreactors were established, both with and without MnO2, to evaluate the redox buffering capacity of MnO2 with view to mitigating the reductive dissolution of iron oxide. This approach aimed to improve the retention of dissolved reactive phosphorus (DRP) on the introduced iron oxide surfaces. It was concluded that iron oxides effectively remove DRP and MnO2 enhances nitrogen (N) removal, with slightly better performance observed in the treatment incorporating Fe oxides and MnO2. Hence, it can be inferred that the addition of manganese and iron oxides proves advantageous as an amendment to the conventional woodchip substrate in DBRs to enhance nutrient removal.
This thesis has demonstrated that Fe-functionalized media can effectively remove DRP in agricultural drainage water. In addition, by incorporating MnO2, Fe oxides can be stabilised under oscillating redox conditions, and therefore the combination of MnO2 and Fe oxides could serve as a practical solution for DBRs to mitigate diffuse pollution in New Zealand. These findings offer insights for redesigning DBRs, providing a clearer understanding of the dynamics of P removal in DBRs, and how functionalized media can be employed in the long term to remove phosphorus from agricultural drainage water, meeting water quality objectives while minimizing P releases.

text: Biogeochemistry of denitrifying bioreactors to enhance phosphorus removal from agricultural subsurface drainage Degradation of water quality due to nutrient over-enrichment has become a global environmental concern. In Aotearoa, agricultural pollution of freshwaters by nutrients is increasing. Therefore, strategies need to be implemented to minimize nutrient pollution in surface waters. Denitrifying bioreactors (DBRs) are a prominent edge-of-field treatment technology to mitigate surface water nitrate loadings from agricultural subsurface drainage. Recent studies have identified that subsurface drainage can also contribute to the loss of phosphorus from agricultural soil. Therefore, this thesis investigates the potential of DBRs to incorporate iron-based materials to sequester phosphorus and reduce pollution of waterways.
There is some evidence suggesting low-level phosphorus removal by woodchip bioreactors alone. However, it is inevitable that woodchips alone do not abiotically remove phosphorus due to the incompatibility between the surface charge of wood at neutral-to-acidic pH values. In this study, raw pinus radiata, and, thermally modified pyrolyzed woodchips were employed for surface modification, with view to enhancing P binding in DBRs.
We were mindful in the design of material functionalization to avoid complicated preparation steps, exotic or harmful reagents, and impractical particle sizes to ensure compatibility for large-scale applications in the agricultural landscape. Results indicated that the functionalization of wood media successfully inversed the surface charge, leading to a net positive charge within the favorable range for phosphorus adsorption under reactor-specific conditions (pH 5.5 − 6). The maximum adsorption capacity of functionalized wood and functionalized biochar corresponded to 65.8 mg g-1 and 31.4 mg g-1, respectively, comparing well to values reported in the literature.
DBRs operate under varying hydraulic conditions, which results in variable flow rates, nutrient concentrations, redox status, pH, and many other variables that affect the operation of the bioreactor. The stability of iron hydr(oxide) composites is expected to be sensitive to some of these conditions, especially acidic and anaerobic conditions, which favor dissolution of iron hydr(oxide)s and therefore could adversely affect P removal. Furthermore, there are other likely products of reduced Fe2+ and orthophosphate (HPO42-) that could form under the conditions anticipated. Therefore, the biogeochemical environment in the DBR was characterized to understand the stability of iron hydr(oxide)s and their ability to subsequently remove of phosphorus.
To date, there have been only limited investigations into the stability of iron hydr(oxide)s under real-world bioreactor conditions, and functionalisation studies often neglect the impact of oscillating redox conditions on the stability of Fe-based adsorbents. In light of this, bench-scale woodchip bioreactors were established, both with and without MnO2, to evaluate the redox buffering capacity of MnO2 with view to mitigating the reductive dissolution of iron oxide. This approach aimed to improve the retention of dissolved reactive phosphorus (DRP) on the introduced iron oxide surfaces. It was concluded that iron oxides effectively remove DRP and MnO2 enhances nitrogen (N) removal, with slightly better performance observed in the treatment incorporating Fe oxides and MnO2. Hence, it can be inferred that the addition of manganese and iron oxides proves advantageous as an amendment to the conventional woodchip substrate in DBRs to enhance nutrient removal.
This thesis has demonstrated that Fe-functionalized media can effectively remove DRP in agricultural drainage water. In addition, by incorporating MnO2, Fe oxides can be stabilised under oscillating redox conditions, and therefore the combination of MnO2 and Fe oxides could serve as a practical solution for DBRs to mitigate diffuse pollution in New Zealand. These findings offer insights for redesigning DBRs, providing a clearer understanding of the dynamics of P removal in DBRs, and how functionalized media can be employed in the long term to remove phosphorus from agricultural drainage water, meeting water quality objectives while minimizing P releases.

year: 2023-12-16

title: Nā Wai Koe? Our tūpuna call us home: Maremare whānau thinking about connections to whenua tupuna

authors: Sampson, Jasmine

subjects: Whenua Tūpuna

abstract: This research focuses on the Maremare whānau from Tiniwaitara Marae, Turakina, in order to explore the importance of our relationship with our whenua tupuna and the related concept of returning home. 

Although many academics have carefully attended to the concept of ‘disconnection’ from whenua tupuna in order to describe the effects of Māori mobility, this term unfortunately reinforces the colonial attempt to detach our people from the things that provide us with our sense of belonging. I argue that thinking about relationship with whenua tupuna through terms like ‘disconnection’ and ‘reconnection’ are unhelpful and problematic; instead, when we understand this relationship in Māori terms, our connection to our whenua tupuna is an everlasting relationship that is woven into the fabric of our whakapapa.

The research combines interviews with three generations of the Maremare whānau, including people with diverse experiences of relationships with Turakina, with critical reflection on relevant concepts from Te Ao Māori. Specifically, mobilising a Kaupapa Māori Theory approach, the thesis draws on an oriori, ‘He Oriori mō Wharaurangi’ as the methodology and foundation of this thesis. In this way, the thesis both argues and demonstrates the value of researchers, and in particular kairangahau Māori, look to mātauranga Māori to guide us in our research about Māori topics. This oriori is iwi specific, it holds kōrero tuku iho that pertains to my whakapapa as an uri of Ngā Wairiki Ngāti Apa and it is very relevant to both my kaupapa and the people participating in the rangahau.

Ultimately, whakapapa rests at the core of connection to whenua tupuna. It is the foundation in which we stand and it connects us as a people to the land that birthed us. This thesis looks at the different ways that our tūpuna call us home, the different ‘returning home’ experiences within the Maremare whānau and how people within the whānau view their connection with our whenua tupuna in Turakina. Nā wai koe? Our tūpuna call us home.

text: Nā Wai Koe? Our tūpuna call us home: Maremare whānau thinking about connections to whenua tupuna This research focuses on the Maremare whānau from Tiniwaitara Marae, Turakina, in order to explore the importance of our relationship with our whenua tupuna and the related concept of returning home. 

Although many academics have carefully attended to the concept of ‘disconnection’ from whenua tupuna in order to describe the effects of Māori mobility, this term unfortunately reinforces the colonial attempt to detach our people from the things that provide us with our sense of belonging. I argue that thinking about relationship with whenua tupuna through terms like ‘disconnection’ and ‘reconnection’ are unhelpful and problematic; instead, when we understand this relationship in Māori terms, our connection to our whenua tupuna is an everlasting relationship that is woven into the fabric of our whakapapa.

The research combines interviews with three generations of the Maremare whānau, including people with diverse experiences of relationships with Turakina, with critical reflection on relevant concepts from Te Ao Māori. Specifically, mobilising a Kaupapa Māori Theory approach, the thesis draws on an oriori, ‘He Oriori mō Wharaurangi’ as the methodology and foundation of this thesis. In this way, the thesis both argues and demonstrates the value of researchers, and in particular kairangahau Māori, look to mātauranga Māori to guide us in our research about Māori topics. This oriori is iwi specific, it holds kōrero tuku iho that pertains to my whakapapa as an uri of Ngā Wairiki Ngāti Apa and it is very relevant to both my kaupapa and the people participating in the rangahau.

Ultimately, whakapapa rests at the core of connection to whenua tupuna. It is the foundation in which we stand and it connects us as a people to the land that birthed us. This thesis looks at the different ways that our tūpuna call us home, the different ‘returning home’ experiences within the Maremare whānau and how people within the whānau view their connection with our whenua tupuna in Turakina. Nā wai koe? Our tūpuna call us home.

year: 2021