title: Improved determination of nitrate concentrations and flow rates in freshwater using ‘Diffusive Gradients in Thin-films’

authors: Corbett, Thomas D. W.

subjects: DGT

abstract: Nutrient pollution, particularly by nitrate, is a persistent issue in waterways. Numerous mitigation strategies have been developed to address this pollution, such as denitrifying bioreactors. The monitoring, however, of nutrient concentrations and mitigation strategy performance has relied on infrequent grab sampling, or expensive on-site equipment. There are numerous challenges with these techniques, such as sample preservation and transport, operational expense, and the ability to account for temporal changes in concentration. Diffusive Gradients in Thin Films (DGT) are capable of overcoming many of the challenges, however, to date their use has mainly been research based, and they are not widely used by monitoring authorities or communities. Diffusive Gradients in Thin Films are passive accumulative chemical monitoring devices, designed to be analyte specific. This thesis sought, firstly, to establish the efficacy of a modified DGT for the monitoring of nitrate, following deployment in chemically and physically complex denitrifying bioreactors. Secondly, the extension of the DGT methodology through (A) incorporation of colour reagents into the binding layer for rapid in-field analysis of nitrate concentrations, (B) developing a DGT method for the determination of flow rates, and (C) understanding the potential biases inherent in DGT methodology for determining concentrations and loads.
The first study focused on the utility of DGT for the determination of denitrifying bioreactor performance – via deployment in two denitrifying bioreactors. DGT overcame many of the challenges of grab sampling, such as more easily accounting for temporal nitrate concentration variation, and reduced analytical requirements. Diffusive Gradients in Thin Films determined nitrate concentrations and removal rates were in strong agreement with high frequency grab sampling, and data collection via DGT was considerably easier than high frequency grab sampling. The DGT, however, still required in-lab analysis for nitrate.
Development of colourimetric binding layers, as a hydrogel or liquid binding layer, might allow infield determination of analyte concentrations easily and accurately. Here, a chitosan-stabilised AuNP suspension, as a liquid binding layer was developed and tested for the colourimetric determination of nitrite concentrations (0 to 1000 mg L⁻¹) and masses (145 μg) in lab based colour development studies. Nitrate reduction to nitrite was achieved through the development of an Fe(0) impregnated poly-2-acrylamido-2-methyl-1-propanesulfonic acid/acrylamide copolymer hydrogel. The developments lay the foundations for further development of the colourimetric-DGT concept.
A novel bromide selective DGT (Br--DGT) was developed, using the Purolite Bromide Plus anion exchange resin, which provided stream flow rates when combined with the constant rate tracer-injection method. The Br--DGT flow method was tested infield at the Mangaharakeke Stream. Flow rates determined by DGT were between -14.7 and 6.5 % of the flow independently monitored weir flow rate. In comparison, grab sample flow rates diverged by 5.5 to 58.9 % from the weir flow rate.
Dynamic and coordinated changes in temperature, flow, and concentration, as potential sources of bias in concentration and load calculations using DGT and grab sampling were modelled. Large, dynamic, and highly correlated to concentration, temperature changes have minimal effect on the calculated DGT concentration. In contrast, as the correlation between concentration and flow increases the bias in calculated DGT loads becomes significant. This means that in systems where there is a high correlation of concentration and flow DGT may not be appropriate for determining loadings.
This thesis had important implications for the use of DGT for determining nutrient concentrations and loads, and stream flow rates – and the monitoring of nutrient pollution. Firstly, it demonstrated that DGT were a useful tool for the determination of nitrate removal rates in the chemically and physically challenging denitrifying bioreactor systems. Secondly, it established the foundation for the in-field determination of nitrate concentrations. Lastly, it extended the DGT methodology for the determination of bromide concentrations and stream flow rates, and provided a greater understanding of the issues when using DGT to determine nitrate loads. This research opened the possibility of DGT for large-scale nutrient monitoring and determination of nutrient mitigation strategy performance, given the quality of DGT data and ease-of-use compared to grab sampling.

text: Improved determination of nitrate concentrations and flow rates in freshwater using ‘Diffusive Gradients in Thin-films’ Nutrient pollution, particularly by nitrate, is a persistent issue in waterways. Numerous mitigation strategies have been developed to address this pollution, such as denitrifying bioreactors. The monitoring, however, of nutrient concentrations and mitigation strategy performance has relied on infrequent grab sampling, or expensive on-site equipment. There are numerous challenges with these techniques, such as sample preservation and transport, operational expense, and the ability to account for temporal changes in concentration. Diffusive Gradients in Thin Films (DGT) are capable of overcoming many of the challenges, however, to date their use has mainly been research based, and they are not widely used by monitoring authorities or communities. Diffusive Gradients in Thin Films are passive accumulative chemical monitoring devices, designed to be analyte specific. This thesis sought, firstly, to establish the efficacy of a modified DGT for the monitoring of nitrate, following deployment in chemically and physically complex denitrifying bioreactors. Secondly, the extension of the DGT methodology through (A) incorporation of colour reagents into the binding layer for rapid in-field analysis of nitrate concentrations, (B) developing a DGT method for the determination of flow rates, and (C) understanding the potential biases inherent in DGT methodology for determining concentrations and loads.
The first study focused on the utility of DGT for the determination of denitrifying bioreactor performance – via deployment in two denitrifying bioreactors. DGT overcame many of the challenges of grab sampling, such as more easily accounting for temporal nitrate concentration variation, and reduced analytical requirements. Diffusive Gradients in Thin Films determined nitrate concentrations and removal rates were in strong agreement with high frequency grab sampling, and data collection via DGT was considerably easier than high frequency grab sampling. The DGT, however, still required in-lab analysis for nitrate.
Development of colourimetric binding layers, as a hydrogel or liquid binding layer, might allow infield determination of analyte concentrations easily and accurately. Here, a chitosan-stabilised AuNP suspension, as a liquid binding layer was developed and tested for the colourimetric determination of nitrite concentrations (0 to 1000 mg L⁻¹) and masses (145 μg) in lab based colour development studies. Nitrate reduction to nitrite was achieved through the development of an Fe(0) impregnated poly-2-acrylamido-2-methyl-1-propanesulfonic acid/acrylamide copolymer hydrogel. The developments lay the foundations for further development of the colourimetric-DGT concept.
A novel bromide selective DGT (Br--DGT) was developed, using the Purolite Bromide Plus anion exchange resin, which provided stream flow rates when combined with the constant rate tracer-injection method. The Br--DGT flow method was tested infield at the Mangaharakeke Stream. Flow rates determined by DGT were between -14.7 and 6.5 % of the flow independently monitored weir flow rate. In comparison, grab sample flow rates diverged by 5.5 to 58.9 % from the weir flow rate.
Dynamic and coordinated changes in temperature, flow, and concentration, as potential sources of bias in concentration and load calculations using DGT and grab sampling were modelled. Large, dynamic, and highly correlated to concentration, temperature changes have minimal effect on the calculated DGT concentration. In contrast, as the correlation between concentration and flow increases the bias in calculated DGT loads becomes significant. This means that in systems where there is a high correlation of concentration and flow DGT may not be appropriate for determining loadings.
This thesis had important implications for the use of DGT for determining nutrient concentrations and loads, and stream flow rates – and the monitoring of nutrient pollution. Firstly, it demonstrated that DGT were a useful tool for the determination of nitrate removal rates in the chemically and physically challenging denitrifying bioreactor systems. Secondly, it established the foundation for the in-field determination of nitrate concentrations. Lastly, it extended the DGT methodology for the determination of bromide concentrations and stream flow rates, and provided a greater understanding of the issues when using DGT to determine nitrate loads. This research opened the possibility of DGT for large-scale nutrient monitoring and determination of nutrient mitigation strategy performance, given the quality of DGT data and ease-of-use compared to grab sampling.

year: 2021

title: Attraction of migratory inanga (galaxias maculatus) and koaro (galaxias brevipinnis) juveniles to adult galaxiid odours

authors: Baker, Cindy F.

subjects: biology

abstract: The response of migratory galaxiid juveniles, inanga (Galaxias maculatus) and koaro (G. brevipinnis), to the odours of adult galaxiids was tested in a two-choice chamber apparatus. Both conspecific and heterospecific odours were tested.  Inanga juveniles were attracted to adult inanga (G.  maculatus), banded kokopu (G. fasciatus), and koaro (G. brevipinnis) odours. However, they were not attracted to odours from common bullies (Gobiomorphus cotidianus). Koaro juveniles exhibited a species-specific attraction to adult koaro odours only. These results demonstrate inanga  uveniles can discriminate and are attracted to adult galaxiids during their migratory phase, whilst migratory koaro juveniles exhibit a species-specific attraction to adult
odours similar to the pheromonal attraction previously described for juvenile banded kokopu. This strengthens the hypothesis for the use of pheromonal cues in stream and habitat selection by amphidromous galaxiids.

text: Attraction of migratory inanga (galaxias maculatus) and koaro (galaxias brevipinnis) juveniles to adult galaxiid odours The response of migratory galaxiid juveniles, inanga (Galaxias maculatus) and koaro (G. brevipinnis), to the odours of adult galaxiids was tested in a two-choice chamber apparatus. Both conspecific and heterospecific odours were tested.  Inanga juveniles were attracted to adult inanga (G.  maculatus), banded kokopu (G. fasciatus), and koaro (G. brevipinnis) odours. However, they were not attracted to odours from common bullies (Gobiomorphus cotidianus). Koaro juveniles exhibited a species-specific attraction to adult koaro odours only. These results demonstrate inanga  uveniles can discriminate and are attracted to adult galaxiids during their migratory phase, whilst migratory koaro juveniles exhibit a species-specific attraction to adult
odours similar to the pheromonal attraction previously described for juvenile banded kokopu. This strengthens the hypothesis for the use of pheromonal cues in stream and habitat selection by amphidromous galaxiids.

year: 2003

title: The Application of the "Best Interests" Principle to Maori Children's Collective Cultural Rights: A Conceptual Shift for the New Zealand Family Court?

authors: Macbeth, Steven Alexander

subjects: "collective cultural rights"

abstract: Indigenous Peoples assert their collective rights in a world where Western liberal theory and individual rights dominate. International human rights law, however, increasingly recognises Indigenous Peoples collective rights in addition to their members’ individual rights. In 2007 the United Nations General Assembly adopted the United Nations Declaration on the Rights of Indigenous Peoples, which represents the most comprehensive acknowledgement of Indigenous Peoples collective rights within international law. In 2009 the Committee on the Rights of the Child issued under the United Nations Convention on the Rights of the Child General Comment No. 11 “Indigenous children and their rights under the Convention”. The Comment references the United Nations Declaration on the Rights of Indigenous Peoples as providing important guidance on the rights of indigenous children. The Comment provides authoritative guidance to State Parties that the application of the “best interests” principle to indigenous children under the Convention requires the assessment of indigenous children’s collective cultural rights and their need to exercise such rights collectively with members of their group, in addition to the indigenous children’s individual rights. Only then can the best interests of indigenous children be determined. 
As a State Party, New Zealand is obliged to implement the United Nations Convention on the Rights of the Child through legislation, judicial determinations and administrative processes. The best interests principle is already the paramount consideration and touchstone for judicial decision-making under the Children, Young Persons, and Their Families Act 1989 and Care of Children Act 2004. The Family Court of New Zealand (while making some inroads in the 1980s and 90s) has yet, however, to develop a coherent and robust approach to the assessment of Maori children’s collective cultural rights when applying the best interests principle as it is obliged to do. General Comment No. 11 and the United Nations Declaration on the Rights of Indigenous Peoples assist by providing authoritative guidance. They augment New Zealand’s family legislation, common law and social policy, which already acknowledge cultural rights and the collective nature of Maori familial relationships.
This paper looks beyond children’s individual rights and the universal application of such rights. It considers the assessment of Maori children’s collective cultural rights in addition to their individual rights under the best interests principle. Further, it analyses the relevant international and domestic authority the Family Court of New Zealand must consider when applying the best interests principle to Maori children, and the practical realities the recognition of Maori children’s collective cultural rights present. A conceptual shift by the Family Court and counsel is required. This paper urges the Family Court to develop the application of the best interests principle under the Care of Children Act 2004 and the Children Young Persons and Their Families Act 1989 to include the assessment of Maori children’s collective cultural rights in addition to their individual rights. In so doing the common law will reflect New Zealand’s unique history and circumstances, and comply with the United Nations Convention on the Rights of the Child. If it fails to do so, the Family Court risks being the subject of criticism for breaching the Convention, being out of sync with international human rights law, domestic legislation and social policy, and increasingly losing relevancy.

text: The Application of the "Best Interests" Principle to Maori Children's Collective Cultural Rights: A Conceptual Shift for the New Zealand Family Court? Indigenous Peoples assert their collective rights in a world where Western liberal theory and individual rights dominate. International human rights law, however, increasingly recognises Indigenous Peoples collective rights in addition to their members’ individual rights. In 2007 the United Nations General Assembly adopted the United Nations Declaration on the Rights of Indigenous Peoples, which represents the most comprehensive acknowledgement of Indigenous Peoples collective rights within international law. In 2009 the Committee on the Rights of the Child issued under the United Nations Convention on the Rights of the Child General Comment No. 11 “Indigenous children and their rights under the Convention”. The Comment references the United Nations Declaration on the Rights of Indigenous Peoples as providing important guidance on the rights of indigenous children. The Comment provides authoritative guidance to State Parties that the application of the “best interests” principle to indigenous children under the Convention requires the assessment of indigenous children’s collective cultural rights and their need to exercise such rights collectively with members of their group, in addition to the indigenous children’s individual rights. Only then can the best interests of indigenous children be determined. 
As a State Party, New Zealand is obliged to implement the United Nations Convention on the Rights of the Child through legislation, judicial determinations and administrative processes. The best interests principle is already the paramount consideration and touchstone for judicial decision-making under the Children, Young Persons, and Their Families Act 1989 and Care of Children Act 2004. The Family Court of New Zealand (while making some inroads in the 1980s and 90s) has yet, however, to develop a coherent and robust approach to the assessment of Maori children’s collective cultural rights when applying the best interests principle as it is obliged to do. General Comment No. 11 and the United Nations Declaration on the Rights of Indigenous Peoples assist by providing authoritative guidance. They augment New Zealand’s family legislation, common law and social policy, which already acknowledge cultural rights and the collective nature of Maori familial relationships.
This paper looks beyond children’s individual rights and the universal application of such rights. It considers the assessment of Maori children’s collective cultural rights in addition to their individual rights under the best interests principle. Further, it analyses the relevant international and domestic authority the Family Court of New Zealand must consider when applying the best interests principle to Maori children, and the practical realities the recognition of Maori children’s collective cultural rights present. A conceptual shift by the Family Court and counsel is required. This paper urges the Family Court to develop the application of the best interests principle under the Care of Children Act 2004 and the Children Young Persons and Their Families Act 1989 to include the assessment of Maori children’s collective cultural rights in addition to their individual rights. In so doing the common law will reflect New Zealand’s unique history and circumstances, and comply with the United Nations Convention on the Rights of the Child. If it fails to do so, the Family Court risks being the subject of criticism for breaching the Convention, being out of sync with international human rights law, domestic legislation and social policy, and increasingly losing relevancy.

year: 2015