title: Biogeochemical Characterisation of an Alum Dosed Stream: Implications for Phosphate Cycling in Lake Rotoehu

authors: Eager, Christopher Andrews

subjects: Alum

abstract: Lakes are highly valued freshwater ecosystems which provide many goods and services upon which humans are reliant. Eutrophication of waterways, driven by the over-enrichment of nutrients such as phosphorus and nitrogen, is a threat to the future quality of water resources globally. Lake restoration methods are increasingly being employed to improve eutrophic waterways, via numerous catchment derived and in-lake approaches. However, spatio-temporal heterogeneity in physicochemical and biogeochemical conditions within lakes may restrict the efficacy of restoration methods.  This thesis explores in-stream alum dosing as a lake remediation strategy for the purpose of dissolved phosphorus inactivation, and its physicochemical and biogeochemical interaction and fate within Lake Rotoehu, New Zealand.

 Laboratory and field measurements were undertaken at Lake Rotoehu, on New Zealand’s North Island. The shallow, polymictic lake resides in an active volcanic area with geothermal inputs, and is subject to several management issues including elevated nutrient concentrations, invasive macrophytes, and frequent cyanobacteria blooms. The geothermal Waitangi Springs, which discharge into Lake Rotoehu, contribute ~69 % of the lake’s total ionic content, and are responsible for enhanced concentrations of biologically limiting nutrients including phosphorus, silicon, nitrate, ammonium, and iron. In an effort to curb in-lake phosphorus levels, in-stream alum-dosing has been employed in order to floc out dissolved reactive phosphorus (DRP), through chemical adsorption and sedimentation.  

The results presented here, culminate from an investigation of the physicochemical and geochemical dynamics across the mixing zone from the Waitangi Springs geothermal stream outlet across Te Wairoa Bay to the main lake body.  A combination of approaches was used: two field experiments with fixed location and transect measurements, laboratory analysis and geochemical speciation modelling with PHREEQC. 

Results show sharp changes in physicochemical water properties across the mixing zone within the bay: pH, O2 and dissolved reactive phosphorus values increased with distance from the stream outlet, whereas major ion concentrations, temperature and conductivity values decreased.  Initial in-stream phosphorus stripping through alum dosing is effective in reducing the DRP load by ~50 % of background concentration. As alum is introduced to the stream water (~pH 6) it precipitates to form amorphous aluminium hydroxide (Al(OH)3(am)) and adsorbs phosphorus via hydroxyl ligand exchange. However, elevated levels of iron in amorphous hydrous ferric hydroxides Fe(OH)3(am) are also likely to be contributing to natural phosphorus binding capacity. Sediment core data also indicated that settled Al(OH)3(am) floc and Fe(OH)3(am) particulates were primarily concentrated within the inner portion of Te Wairoa Bay near the Waitangi Springs outlet. Surface water physicochemical and geochemical concentrations were spatially resolved and indicated distinct mixing boundaries (pH, DO, temp) and patchiness (Al, Fe, DRP) within Te Wairoa Bay associated with the locations and configuration of dense submerged macrophytes (Ceratophyllum demersum). Geochemical speciation modelling also indicated that the primary dissolved Al species was Al(OH)4- under the observed daytime conditions, and that Fe was primarily in colloidal form Fe(OH)3(am), which was confirmed through diffusive gradients in thin films (DGT) measurements. 

A diel sampling experiment also confirmed that as alum-dosed water enters the lake, daytime biogeochemical conditions driven by C. demersum alter physicochemical water properties from ~pH 6 to ~pH 9, and DO (supersaturation) via increased photosynthesis.  Diel-fluxes in geochemical solubility (Al, Fe, and DRP) responded to physicochemical shifts (pH, O2,) and demonstrate that C. demersum have the capacity to influence Al solubility and DRP availability within Te Wairoa Bay.
 
This work highlights the complexity of biogeochemical processes within aquatic freshwater ecosystems. Moreover, the results emphasise the need to account for the significant spatial and temporal heterogeneity of physicochemical parameters in the development of effective lake remediation strategies.

text: Biogeochemical Characterisation of an Alum Dosed Stream: Implications for Phosphate Cycling in Lake Rotoehu Lakes are highly valued freshwater ecosystems which provide many goods and services upon which humans are reliant. Eutrophication of waterways, driven by the over-enrichment of nutrients such as phosphorus and nitrogen, is a threat to the future quality of water resources globally. Lake restoration methods are increasingly being employed to improve eutrophic waterways, via numerous catchment derived and in-lake approaches. However, spatio-temporal heterogeneity in physicochemical and biogeochemical conditions within lakes may restrict the efficacy of restoration methods.  This thesis explores in-stream alum dosing as a lake remediation strategy for the purpose of dissolved phosphorus inactivation, and its physicochemical and biogeochemical interaction and fate within Lake Rotoehu, New Zealand.

 Laboratory and field measurements were undertaken at Lake Rotoehu, on New Zealand’s North Island. The shallow, polymictic lake resides in an active volcanic area with geothermal inputs, and is subject to several management issues including elevated nutrient concentrations, invasive macrophytes, and frequent cyanobacteria blooms. The geothermal Waitangi Springs, which discharge into Lake Rotoehu, contribute ~69 % of the lake’s total ionic content, and are responsible for enhanced concentrations of biologically limiting nutrients including phosphorus, silicon, nitrate, ammonium, and iron. In an effort to curb in-lake phosphorus levels, in-stream alum-dosing has been employed in order to floc out dissolved reactive phosphorus (DRP), through chemical adsorption and sedimentation.  

The results presented here, culminate from an investigation of the physicochemical and geochemical dynamics across the mixing zone from the Waitangi Springs geothermal stream outlet across Te Wairoa Bay to the main lake body.  A combination of approaches was used: two field experiments with fixed location and transect measurements, laboratory analysis and geochemical speciation modelling with PHREEQC. 

Results show sharp changes in physicochemical water properties across the mixing zone within the bay: pH, O2 and dissolved reactive phosphorus values increased with distance from the stream outlet, whereas major ion concentrations, temperature and conductivity values decreased.  Initial in-stream phosphorus stripping through alum dosing is effective in reducing the DRP load by ~50 % of background concentration. As alum is introduced to the stream water (~pH 6) it precipitates to form amorphous aluminium hydroxide (Al(OH)3(am)) and adsorbs phosphorus via hydroxyl ligand exchange. However, elevated levels of iron in amorphous hydrous ferric hydroxides Fe(OH)3(am) are also likely to be contributing to natural phosphorus binding capacity. Sediment core data also indicated that settled Al(OH)3(am) floc and Fe(OH)3(am) particulates were primarily concentrated within the inner portion of Te Wairoa Bay near the Waitangi Springs outlet. Surface water physicochemical and geochemical concentrations were spatially resolved and indicated distinct mixing boundaries (pH, DO, temp) and patchiness (Al, Fe, DRP) within Te Wairoa Bay associated with the locations and configuration of dense submerged macrophytes (Ceratophyllum demersum). Geochemical speciation modelling also indicated that the primary dissolved Al species was Al(OH)4- under the observed daytime conditions, and that Fe was primarily in colloidal form Fe(OH)3(am), which was confirmed through diffusive gradients in thin films (DGT) measurements. 

A diel sampling experiment also confirmed that as alum-dosed water enters the lake, daytime biogeochemical conditions driven by C. demersum alter physicochemical water properties from ~pH 6 to ~pH 9, and DO (supersaturation) via increased photosynthesis.  Diel-fluxes in geochemical solubility (Al, Fe, and DRP) responded to physicochemical shifts (pH, O2,) and demonstrate that C. demersum have the capacity to influence Al solubility and DRP availability within Te Wairoa Bay.
 
This work highlights the complexity of biogeochemical processes within aquatic freshwater ecosystems. Moreover, the results emphasise the need to account for the significant spatial and temporal heterogeneity of physicochemical parameters in the development of effective lake remediation strategies.

year: 2017

title: On the Benefits of Non-Canonical Filtering in Publish/Subscribe Systems

authors: Bittner, Sven

subjects: computer science

abstract: Current matching approaches in pub/sub systems only allow conjunctive subscriptions. Arbitrary subscriptions have to be transformed into canonical expressions, e.g., DNFs, and need to be treated as several conjunctive subscriptions. This technique is known from database systems and allows us to apply more efficient filtering algorithms. Since pub/sub systems are the contrary to traditional database systems, it is questionable if filtering several canonical subscriptions is the most efficient and scalable way of dealing with arbitrary subscriptions. In this paper we show that our filtering approach supporting arbitrary Boolean subscriptions is more scalable and efficient than current matching algorithms requiring transformations of subscriptions into DNFs.

text: On the Benefits of Non-Canonical Filtering in Publish/Subscribe Systems Current matching approaches in pub/sub systems only allow conjunctive subscriptions. Arbitrary subscriptions have to be transformed into canonical expressions, e.g., DNFs, and need to be treated as several conjunctive subscriptions. This technique is known from database systems and allows us to apply more efficient filtering algorithms. Since pub/sub systems are the contrary to traditional database systems, it is questionable if filtering several canonical subscriptions is the most efficient and scalable way of dealing with arbitrary subscriptions. In this paper we show that our filtering approach supporting arbitrary Boolean subscriptions is more scalable and efficient than current matching algorithms requiring transformations of subscriptions into DNFs.

year: 2005

title: Exploring Inclusion, Support and Culture in the Workplace: A Study of Māori and European Employees

authors: Brougham, David M.

subjects: Inclusion

abstract: New Zealand boasts a wide range of vibrant and contrasting cultures within the workplace. This level of cultural diversity within New Zealand is set to increase substantially over the next 15 years. This increase has already created a need for researchers and human resource managers to understand the importance and benefits of diversity within the workplace. However, recent research has found that the ‘apparent benefits’ of traditional diversity management cannot be fulfilled unless individuals feel included within the organisation. 
Inclusion is defined as “the degree to which an employee perceives that he or she is an esteemed member of the work group through experiencing treatment that satisfies his or her needs for belongingness and uniqueness” (Shore, Randel, Chung, Dean, Ehrhart & Singh, 2011, p. 1265). Despite a realisation that inclusion may be the future of managing diverse workplaces, the literature on inclusion is under developed and lacks empirical testing. The main contribution and focus of this thesis centres on cultural inclusion in the workplace. A secondary focus is on the benefits of other types of support, from various sources (e.g., organisation, supervisor, and family), within New Zealand’s rich cultural context. 
This PhD has been undertaken by publication. Thus, the majority of its chapters are stand-alone (although related) journal articles. Many of the journal articles within this thesis are either under review, or published/in press, and this is signalled at the start of each chapter. Chapters one and two overview the thesis and discuss the research methods used within this PhD by publication. The first journal article (chapter three) details the cultural context of New Zealand and the importance of managing diversity and including all employees. The second journal article (chapter four) focuses on the importance that Māori culture, collectivism and language has in the workplace for Māori well-being. Findings were based on a sample of Māori employees, with the results highlighting the importance of collectivism and cultural identity for Māori employees towards achieving greater well-being. These two published articles build the foundation for the next three journal articles, which discuss the importance of cultural inclusion in the workplace. 
In an endeavour to test the inclusiveness of organisations’ support for cultural values and beliefs, this thesis offers a new measure of perceived cultural inclusion (PCI). The PCI measure is based on perceived organisational support (POS) owing to the parallels between inclusion and POS. POS is also a strong and reliable predictor of employee outcomes. Data was collected from two culturally distinct groups (i.e., Māori n=349 and New Zealand Europeans n=144) within New Zealand. Findings showed that PCI predicted POS, which in turn predicted job outcomes (i.e., job satisfaction, career satisfaction, organisational commitment, turnover intentions) and mental health outcomes (anxiety and depression) for both Māori and New Zealand Europeans (refer to chapters five and six). This thesis also investigated the effects of PCI to POS to work-family related outcomes on the sample of Māori employees, and findings suggested that PCI would predict POS, which would in turn predict work-family related outcomes in the expected direction (refer to chapter seven). These three chapters provide strong empirical evidence for POS mediating the influence of PCI on numerous employee outcomes. 
The literature has also highlighted the importance of supervisor and family support when predicting job and well-being outcomes. The effects that supervisor support for work-family issues and whānau (extended family) support have on job outcomes (chapter eight) and well-being outcomes (chapter nine) for Māori employees were also investigated. Findings from two Māori samples (N=260 and N=466) emphasised the importance that both supervisor and whānau support have on job satisfaction, turnover intentions, life satisfaction, cultural identity, health and well-being (see chapters eight and nine for more details). 
Overall, this thesis draws findings from both New Zealand European and Māori employee samples to provide evidence that supporting and understanding cultural values is highly important for job and well-being outcomes. These findings have many theoretical and managerial implications. The following chapters discuss in-depth, relevant theories, literature, methods and conclusions that form this thesis.

text: Exploring Inclusion, Support and Culture in the Workplace: A Study of Māori and European Employees New Zealand boasts a wide range of vibrant and contrasting cultures within the workplace. This level of cultural diversity within New Zealand is set to increase substantially over the next 15 years. This increase has already created a need for researchers and human resource managers to understand the importance and benefits of diversity within the workplace. However, recent research has found that the ‘apparent benefits’ of traditional diversity management cannot be fulfilled unless individuals feel included within the organisation. 
Inclusion is defined as “the degree to which an employee perceives that he or she is an esteemed member of the work group through experiencing treatment that satisfies his or her needs for belongingness and uniqueness” (Shore, Randel, Chung, Dean, Ehrhart & Singh, 2011, p. 1265). Despite a realisation that inclusion may be the future of managing diverse workplaces, the literature on inclusion is under developed and lacks empirical testing. The main contribution and focus of this thesis centres on cultural inclusion in the workplace. A secondary focus is on the benefits of other types of support, from various sources (e.g., organisation, supervisor, and family), within New Zealand’s rich cultural context. 
This PhD has been undertaken by publication. Thus, the majority of its chapters are stand-alone (although related) journal articles. Many of the journal articles within this thesis are either under review, or published/in press, and this is signalled at the start of each chapter. Chapters one and two overview the thesis and discuss the research methods used within this PhD by publication. The first journal article (chapter three) details the cultural context of New Zealand and the importance of managing diversity and including all employees. The second journal article (chapter four) focuses on the importance that Māori culture, collectivism and language has in the workplace for Māori well-being. Findings were based on a sample of Māori employees, with the results highlighting the importance of collectivism and cultural identity for Māori employees towards achieving greater well-being. These two published articles build the foundation for the next three journal articles, which discuss the importance of cultural inclusion in the workplace. 
In an endeavour to test the inclusiveness of organisations’ support for cultural values and beliefs, this thesis offers a new measure of perceived cultural inclusion (PCI). The PCI measure is based on perceived organisational support (POS) owing to the parallels between inclusion and POS. POS is also a strong and reliable predictor of employee outcomes. Data was collected from two culturally distinct groups (i.e., Māori n=349 and New Zealand Europeans n=144) within New Zealand. Findings showed that PCI predicted POS, which in turn predicted job outcomes (i.e., job satisfaction, career satisfaction, organisational commitment, turnover intentions) and mental health outcomes (anxiety and depression) for both Māori and New Zealand Europeans (refer to chapters five and six). This thesis also investigated the effects of PCI to POS to work-family related outcomes on the sample of Māori employees, and findings suggested that PCI would predict POS, which would in turn predict work-family related outcomes in the expected direction (refer to chapter seven). These three chapters provide strong empirical evidence for POS mediating the influence of PCI on numerous employee outcomes. 
The literature has also highlighted the importance of supervisor and family support when predicting job and well-being outcomes. The effects that supervisor support for work-family issues and whānau (extended family) support have on job outcomes (chapter eight) and well-being outcomes (chapter nine) for Māori employees were also investigated. Findings from two Māori samples (N=260 and N=466) emphasised the importance that both supervisor and whānau support have on job satisfaction, turnover intentions, life satisfaction, cultural identity, health and well-being (see chapters eight and nine for more details). 
Overall, this thesis draws findings from both New Zealand European and Māori employee samples to provide evidence that supporting and understanding cultural values is highly important for job and well-being outcomes. These findings have many theoretical and managerial implications. The following chapters discuss in-depth, relevant theories, literature, methods and conclusions that form this thesis.

year: 2013