title: The sequestration of phosphate by iron phases in the sediments from Lake Rotorua, New Zealand

authors: Mangan, Carmel Mary

subjects: sediments

abstract: A sequential extraction method was used to determine which dominant sedimentary mineral phase was involved in phosphorus retention in the sediments of Lake Rotorua and to verify the importance of iron phases in the role as a phosphorus sink. The observed influence of the experimental conditions upon the extent of phosphate adsorption to various iron phases shows a considerable quantity of phosphorus is present in the reducible phase and in the residual mineral phase. The phosphorus associated with iron(III) oxide phases was released into solution under reducing conditions when ferric iron oxide/oxyhydroxides, including amorphous and poorly crystalline Fe(III) phases, were solubilized. The residual primary and secondary mineral phases remained stable in the sediments until they were exposed to extremely acidic media analogous to strongly reducing conditions. Manganese is not involved in phosphorus retention to the same extent as iron. Aluminium phases present were released from surface complexes with relative ease and also from mineral structures under the prevailing conditions. The results show a strong agreement between aluminium and phosphorus suggesting it is associated with various aluminium phases to some extent. The sediments of Lake Rotorua are rich in organic-bound P which is released when organic material is oxidized under conditions analogous to anaerobic degradation. The degradation of refractory organic material represents a significant source of phosphorus for incorporation into diagenetic minerals forming in oxic and anoxic layers of the sediment.
Heavy liquid separation of the sediments concentrated the small quantities of dense minerals into a separate fraction and the presence of iron sulfides could be verified. Three density fractions obtained by this method separated the diatoms (d less than 2.6 g cm-3), the silicates (d greater than 2.6 less than 3.7 g cm-3) and the heavy minerals (d greater than 3.7 g cm-3) present in the sediment sample. In the heavy mineral phase spherulitic framboidal pyrite and rhombohedrial siderite were observed by scanning electron microscopy (SEM).
Energy dispersive x-ray fluorescence (XRF) analysis of the framboidal pyrite detected significant fluorescence's for sulphur and iron. The elemental analysis of siderite characterised it as an iron-rich, non-sulfidic particle with no phosphorus fluorescence. Particles were also observed that had a variable morphology to the framboidal pyrite minerals but similar ratio of Fe to S in the XRF spectrum. It is likely they are other stable forms of iron sulfides or pyrites in various stages of diagenetic dissolution. Digestion of the three density fractions shows the heavy mineral phase is significantly enriched in sulfur and in iron confirming the presence of sulfides. The sulfide-forming trace metals are concentrating in the heavy mineral phase but a progressive enrichment of trace metals down core is not found in the results. Many of the trace elements show maximum concentrations in the Tarawera tephra.
There is a good agreement between iron and phosphorus in both treatments that implies iron phases are the predominant phosphorus fixers in the sediments of Lake Rotorua. However the identity of the phosphorus sink could not be confirmed by SEM or XRF analysis of the heavy minerals. The most likely explanations for the observed concentrations of iron and phosphorus and enrichment in the heavy mineral fraction are the persistence of the highly insoluble crystalline iron oxyhydroxides (goethite) in reducing sediments or the formation of the reduced iron mineral vivianite. Considering the density of vivianite it would have being taken into the heavy fraction by default which would account for the enrichment demonstrated by the solution analysis.

text: The sequestration of phosphate by iron phases in the sediments from Lake Rotorua, New Zealand A sequential extraction method was used to determine which dominant sedimentary mineral phase was involved in phosphorus retention in the sediments of Lake Rotorua and to verify the importance of iron phases in the role as a phosphorus sink. The observed influence of the experimental conditions upon the extent of phosphate adsorption to various iron phases shows a considerable quantity of phosphorus is present in the reducible phase and in the residual mineral phase. The phosphorus associated with iron(III) oxide phases was released into solution under reducing conditions when ferric iron oxide/oxyhydroxides, including amorphous and poorly crystalline Fe(III) phases, were solubilized. The residual primary and secondary mineral phases remained stable in the sediments until they were exposed to extremely acidic media analogous to strongly reducing conditions. Manganese is not involved in phosphorus retention to the same extent as iron. Aluminium phases present were released from surface complexes with relative ease and also from mineral structures under the prevailing conditions. The results show a strong agreement between aluminium and phosphorus suggesting it is associated with various aluminium phases to some extent. The sediments of Lake Rotorua are rich in organic-bound P which is released when organic material is oxidized under conditions analogous to anaerobic degradation. The degradation of refractory organic material represents a significant source of phosphorus for incorporation into diagenetic minerals forming in oxic and anoxic layers of the sediment.
Heavy liquid separation of the sediments concentrated the small quantities of dense minerals into a separate fraction and the presence of iron sulfides could be verified. Three density fractions obtained by this method separated the diatoms (d less than 2.6 g cm-3), the silicates (d greater than 2.6 less than 3.7 g cm-3) and the heavy minerals (d greater than 3.7 g cm-3) present in the sediment sample. In the heavy mineral phase spherulitic framboidal pyrite and rhombohedrial siderite were observed by scanning electron microscopy (SEM).
Energy dispersive x-ray fluorescence (XRF) analysis of the framboidal pyrite detected significant fluorescence's for sulphur and iron. The elemental analysis of siderite characterised it as an iron-rich, non-sulfidic particle with no phosphorus fluorescence. Particles were also observed that had a variable morphology to the framboidal pyrite minerals but similar ratio of Fe to S in the XRF spectrum. It is likely they are other stable forms of iron sulfides or pyrites in various stages of diagenetic dissolution. Digestion of the three density fractions shows the heavy mineral phase is significantly enriched in sulfur and in iron confirming the presence of sulfides. The sulfide-forming trace metals are concentrating in the heavy mineral phase but a progressive enrichment of trace metals down core is not found in the results. Many of the trace elements show maximum concentrations in the Tarawera tephra.
There is a good agreement between iron and phosphorus in both treatments that implies iron phases are the predominant phosphorus fixers in the sediments of Lake Rotorua. However the identity of the phosphorus sink could not be confirmed by SEM or XRF analysis of the heavy minerals. The most likely explanations for the observed concentrations of iron and phosphorus and enrichment in the heavy mineral fraction are the persistence of the highly insoluble crystalline iron oxyhydroxides (goethite) in reducing sediments or the formation of the reduced iron mineral vivianite. Considering the density of vivianite it would have being taken into the heavy fraction by default which would account for the enrichment demonstrated by the solution analysis.

year: 2007

title: Virtual bioprocess simulation laboratory for teaching and learning

authors: Berenjian, Aydin

abstract: There is great potential in applying virtual technology to support teaching and learning. A 3D virtual bioprocess simulation will enable users to learn about both basics of laboratory safety and fermentation principles. Once procedures and exercises within the simulator have been carried out, users will have a deeper understanding about fermentation principles, common lab procedures, experiment design and analysis of data. This software would be an efficient, low-cost option to educators and students within fields such as Biotechnology, Biology, Biochemical Engineering, Biochemistry, Genetics, Microbiology and more.

text: Virtual bioprocess simulation laboratory for teaching and learning There is great potential in applying virtual technology to support teaching and learning. A 3D virtual bioprocess simulation will enable users to learn about both basics of laboratory safety and fermentation principles. Once procedures and exercises within the simulator have been carried out, users will have a deeper understanding about fermentation principles, common lab procedures, experiment design and analysis of data. This software would be an efficient, low-cost option to educators and students within fields such as Biotechnology, Biology, Biochemical Engineering, Biochemistry, Genetics, Microbiology and more.

year: 2018

title: Maori Te Aroha before the opening of the goldfield (mostly through Pakeha eyes)

authors: Hart, Philip

abstract: The various names of the peaks of the mountain and the legends concerning it reflected a violent past. As proof, several pa have been located, both at Te Aroha and at Waiorongomai, and the names of some of the streams indicate the nature and consequences of the battles fought in this contested area.
Ngati Rahiri was subdivided into three hapu: Ngati Tumutumu, Hgati Hue, and Ngati Kopirimau, descendents of these ancestors. In the nineteenth century, when the population was small, Hou was the senior rangatira, with Tutuki being the subordinate rangatira of the plains. A pa (later known as Tui pa) was constructed at Omahu, to the north of the hot springs, which were prized by Maori and increasingly enjoyed by Pakeha. Some of the land was cultivated, though visiting Pakeha considered that settlers could do much more to develop the agricultural potential. Most Ngati Rahiri were regarded as being ‘friendly’, welcoming (and benefiting from) visitors. Elaborate welcoming ceremonies were held for officials and rangatira, and a hotel operated by a rangatira’s son provided basic accommodation. Under Maori auspices the first race day was held in January 1878. 
Also in 1878, negotiators obtained an agreement to make a road to Paeroa, using Maori workers, and as the benefits of such improvements became apparent there was increased willingness to permit the construction of more roads, a bridge, and the snagging of the river, over the objections of a minority. Pakeha disapproved of how money raised through land sales in particular were wasted on extravagant displays of mana, which were not possible after the end of the 1870s because of lack of money, necessitating seeking paid employment. Friendly contact increased steadily, apart from occasional worries prompted by such events as the shooting of Daldy McWilliams, and a football match in May 1880 reportedly revealed ‘the utmost friendly feeling’ existing between Maori and Pakeha.

text: Maori Te Aroha before the opening of the goldfield (mostly through Pakeha eyes) The various names of the peaks of the mountain and the legends concerning it reflected a violent past. As proof, several pa have been located, both at Te Aroha and at Waiorongomai, and the names of some of the streams indicate the nature and consequences of the battles fought in this contested area.
Ngati Rahiri was subdivided into three hapu: Ngati Tumutumu, Hgati Hue, and Ngati Kopirimau, descendents of these ancestors. In the nineteenth century, when the population was small, Hou was the senior rangatira, with Tutuki being the subordinate rangatira of the plains. A pa (later known as Tui pa) was constructed at Omahu, to the north of the hot springs, which were prized by Maori and increasingly enjoyed by Pakeha. Some of the land was cultivated, though visiting Pakeha considered that settlers could do much more to develop the agricultural potential. Most Ngati Rahiri were regarded as being ‘friendly’, welcoming (and benefiting from) visitors. Elaborate welcoming ceremonies were held for officials and rangatira, and a hotel operated by a rangatira’s son provided basic accommodation. Under Maori auspices the first race day was held in January 1878. 
Also in 1878, negotiators obtained an agreement to make a road to Paeroa, using Maori workers, and as the benefits of such improvements became apparent there was increased willingness to permit the construction of more roads, a bridge, and the snagging of the river, over the objections of a minority. Pakeha disapproved of how money raised through land sales in particular were wasted on extravagant displays of mana, which were not possible after the end of the 1870s because of lack of money, necessitating seeking paid employment. Friendly contact increased steadily, apart from occasional worries prompted by such events as the shooting of Daldy McWilliams, and a football match in May 1880 reportedly revealed ‘the utmost friendly feeling’ existing between Maori and Pakeha.

year: 2016