title: Phosphorus and arsenic distributions in a seasonally-stratified, iron- and manganese-rich lake: microbiological and geochemical controls

authors: Hartland, Adam

abstract: Seasonal stratification in temperate lakes greater than a few metres deep provides conditions amenable to pronounced vertical zonation of redox chemistry. Such changes are particularly evident in eutrophic systems where high phytoplankton biomass often leads to seasonally-established anoxic hypolimnia and profound changes in geochemical conditions. In this study, we investigated the behaviour of trace elements in the water column of a seasonally-stratified, eutrophic lake. Two consecutive years of data from Lake Ngapouri, North Island, New Zealand, demonstrate the occurrence of highly correlated profiles of phosphorus (P), arsenic (As), iron (Fe) and manganese (Mn), all of which increased in concentration by 1-2 orders of magnitude within the anoxic hypolimnion. Stoichiometric and mass-balance considerations demonstrate that increases in alkalinity in hypolimnetic waters were consistent with observed changes in sulfate, Fe and Mn concentrations with depth, corresponding to dissimilatory reduction of sulfate, Fe(III) and Mn(IV) hydroxides. Thermodynamic constraints on Fe, Mn and Al solubility indicate that amorphous Fe(III), Mn(IV) hydroxides most probably controlled Fe and Mn in the surface mixed layer (~0 to 8 m) while Al(III) hydroxides were supersaturated throughout the entire system. Surface complexation modelling indicated that iron hydroxides (HFO) potentially dominated As speciation in the lake. It is likely that other colloidal phases such as allophanic clays also limited HPO42- activity, reducing competition for HAsO42- adsorption to iron hydroxides. This research highlights the coupling of P, As, Fe and Mn in Lake Ngapouri, and the apparent role of multiple colloidal phases in affecting P and As activity within overarching microbiological and geochemical processes.

text: Phosphorus and arsenic distributions in a seasonally-stratified, iron- and manganese-rich lake: microbiological and geochemical controls Seasonal stratification in temperate lakes greater than a few metres deep provides conditions amenable to pronounced vertical zonation of redox chemistry. Such changes are particularly evident in eutrophic systems where high phytoplankton biomass often leads to seasonally-established anoxic hypolimnia and profound changes in geochemical conditions. In this study, we investigated the behaviour of trace elements in the water column of a seasonally-stratified, eutrophic lake. Two consecutive years of data from Lake Ngapouri, North Island, New Zealand, demonstrate the occurrence of highly correlated profiles of phosphorus (P), arsenic (As), iron (Fe) and manganese (Mn), all of which increased in concentration by 1-2 orders of magnitude within the anoxic hypolimnion. Stoichiometric and mass-balance considerations demonstrate that increases in alkalinity in hypolimnetic waters were consistent with observed changes in sulfate, Fe and Mn concentrations with depth, corresponding to dissimilatory reduction of sulfate, Fe(III) and Mn(IV) hydroxides. Thermodynamic constraints on Fe, Mn and Al solubility indicate that amorphous Fe(III), Mn(IV) hydroxides most probably controlled Fe and Mn in the surface mixed layer (~0 to 8 m) while Al(III) hydroxides were supersaturated throughout the entire system. Surface complexation modelling indicated that iron hydroxides (HFO) potentially dominated As speciation in the lake. It is likely that other colloidal phases such as allophanic clays also limited HPO42- activity, reducing competition for HAsO42- adsorption to iron hydroxides. This research highlights the coupling of P, As, Fe and Mn in Lake Ngapouri, and the apparent role of multiple colloidal phases in affecting P and As activity within overarching microbiological and geochemical processes.

year: 2015

title: Case-based research in community and social psychology: Introduction to the special issue

authors: Hodgetts, Darrin

subjects: Homelessness

abstract: Cases are highly prevalent in teaching and practice in psychology. Case-based research is crucial for engaged and relevant community and applied social psychologies, but is often subject to critique. This editorial responds to such critiques, clarifies various misconceptions regarding this research strategy, and argues for the utility of case-based research. We explore the theoretical basis and implications of case-based research for community action and participative interventions. This special issue offers a collection of articles that showcase the use of a range of methods in case-based research. Contributions include: (i) a conceptual argument regarding the logic of case studies; (ii) a single-person case study; (iii) a group-level case study; (iv) a multi-site case study, (v) a reflection on challenges of participative research, using the action-researcher as the case. These contributions demonstrate how the use of exemplars is crucial for community and applied social psychologists developing knowledge about social issues in complex and diverse societies, with a view to improving the human condition.

text: Case-based research in community and social psychology: Introduction to the special issue Cases are highly prevalent in teaching and practice in psychology. Case-based research is crucial for engaged and relevant community and applied social psychologies, but is often subject to critique. This editorial responds to such critiques, clarifies various misconceptions regarding this research strategy, and argues for the utility of case-based research. We explore the theoretical basis and implications of case-based research for community action and participative interventions. This special issue offers a collection of articles that showcase the use of a range of methods in case-based research. Contributions include: (i) a conceptual argument regarding the logic of case studies; (ii) a single-person case study; (iii) a group-level case study; (iv) a multi-site case study, (v) a reflection on challenges of participative research, using the action-researcher as the case. These contributions demonstrate how the use of exemplars is crucial for community and applied social psychologists developing knowledge about social issues in complex and diverse societies, with a view to improving the human condition.

year: 2012

title: Recognition and indigenizing official statistics: Reflections from Aotearoa New Zealand and Australia

authors: Kukutai, Tahu

subjects: Indigenou

abstract: In First World colonised nations such as Aotearoa New Zealand and Australia, population statistics form the evidentiary base for how Indigenous peoples are known and `managed' through state policy approaches. Yet, population statistics are not a neutral counting. Decisions of what and how to count reflect particular assumptions about Indigenous identity, ways of life and wellbeing. More often than not, the requirements and priorities of government take precedence over the informational needs and priorities of Indigenous communities. Whereas National Statistics Offices (NSOs) once rendered Indigenous peoples invisible in official statistics through non-recognition, the more pressing problem in the 21st century is that of misrecognition. In seeking to move beyond statistical misrecognition, we propose a set of guiding principles for bringing government reporting frameworks and Indigenous concepts of identity and wellbeing into closer proximity. We argue that a principled approach to collecting, disseminating and analysing Indigenous data not only avoids misrecognising Indigenous peoples but enhances the functionality of official statistics for Indigenous peoples and NSOs alike.

text: Recognition and indigenizing official statistics: Reflections from Aotearoa New Zealand and Australia In First World colonised nations such as Aotearoa New Zealand and Australia, population statistics form the evidentiary base for how Indigenous peoples are known and `managed' through state policy approaches. Yet, population statistics are not a neutral counting. Decisions of what and how to count reflect particular assumptions about Indigenous identity, ways of life and wellbeing. More often than not, the requirements and priorities of government take precedence over the informational needs and priorities of Indigenous communities. Whereas National Statistics Offices (NSOs) once rendered Indigenous peoples invisible in official statistics through non-recognition, the more pressing problem in the 21st century is that of misrecognition. In seeking to move beyond statistical misrecognition, we propose a set of guiding principles for bringing government reporting frameworks and Indigenous concepts of identity and wellbeing into closer proximity. We argue that a principled approach to collecting, disseminating and analysing Indigenous data not only avoids misrecognising Indigenous peoples but enhances the functionality of official statistics for Indigenous peoples and NSOs alike.

year: 2015