title: Sediment aluminium content of Lakes Rotorua and Rotoehu: 2020 monitoring survey

authors: Tempero, Grant Wayne

abstract: The application of aluminium sulphate (alum) to freshwater systems is commonly undertaken in order to restrict the availability of dissolved reactive phosphate (DRP), thereby reducing phytoplankton growth. Alum treatment of inflows to Lake Rotorua was initiated in 2006 and to Lake Rotoehu in 2011. As of December 2020, a total of 773 tonnes of aluminium had been dosed to Lake Rotorua and 124 tonnes to Lake Rotoehu. Improvements in water quality have been subsequently observed in Lake Rotorua with values of the Trophic Lake Index (TLI) decreasing from 4.8 to 4.2. In contrast, water quality has not significantly improved in Lake Rotoehu and alum dosing was halted from July 2018 to December 2020 while a review was conducted.
The University of Waikato was contracted by the Bay of Plenty Regional Council to conduct on-going monitoring of sediment aluminium concentrations in lakes Rotorua and Rotoehu as part of their resource consent conditions for alum dosing of inflows to these lakes. In addition to sediment total aluminium content, the proportion of amorphous (non-crystalline) aluminium was assessed. Amorphous aluminium is recognised as the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from the water column. It was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing. 
Fifteen sediment cores were taken from Lake Rotorua in December 2020. Previous surveys had reported little aluminium accumulation in the main basin of Lake Rotorua, with aluminium accumulation primarily occurring near the outlet to the Utuhina Stream and the 45 m deep crater north of Motutara Point. Based on this information, coring locations were modified from previous surveys with seven near-shore and crater sites sampled and the number of main basin sites sampled reduced to eight. The background sediment aluminium content for the main basin of Lake Rotorua is approximately 5 g Al kg-1 dry weight. The current survey supports the findings of previous sediment surveys with the main depositional areas for alum derived aluminium being the surface (1–4 cm depth) sediments of Te Ruapeka Bay, which can reach 12 g Al kg⁻¹ and the crater north of Motutara Point at ~8 g Al kg⁻¹. There was no apparent accumulation of aluminium beyond background levels to the east of Sulphur Bay or in the main basin of Lake Rotorua.
In Lake Rotoehu, seven sites were surveyed in December 2020, extending from the mouth of the Waitangi Stream out into the main basin of the lake. Results were similar to those reported by Tempero and Hamilton (2016), with background sediment aluminium content approximately 5-6 g Al kg⁻¹. Alum derived aluminium was primarily accumulating in Te Wairoa
Bay close to the discharge point of the Waitangi Stream with levels exceeding 25 g Al kg⁻¹ However, the two-year cessation of alum dosing resulted in a small decline of ~5 g Al kg⁻¹ in the surface sediments. Despite a five-fold increase in total aluminium content in Te Wairoa Bay over background levels, amorphous aluminium content appears to have declined due to the 2-year halt in alum dosing and aging of alum floc to the mineral gibbsite. There was no evidence of aluminium accumulation in the main basin of Lake Rotoehu.

text: Sediment aluminium content of Lakes Rotorua and Rotoehu: 2020 monitoring survey The application of aluminium sulphate (alum) to freshwater systems is commonly undertaken in order to restrict the availability of dissolved reactive phosphate (DRP), thereby reducing phytoplankton growth. Alum treatment of inflows to Lake Rotorua was initiated in 2006 and to Lake Rotoehu in 2011. As of December 2020, a total of 773 tonnes of aluminium had been dosed to Lake Rotorua and 124 tonnes to Lake Rotoehu. Improvements in water quality have been subsequently observed in Lake Rotorua with values of the Trophic Lake Index (TLI) decreasing from 4.8 to 4.2. In contrast, water quality has not significantly improved in Lake Rotoehu and alum dosing was halted from July 2018 to December 2020 while a review was conducted.
The University of Waikato was contracted by the Bay of Plenty Regional Council to conduct on-going monitoring of sediment aluminium concentrations in lakes Rotorua and Rotoehu as part of their resource consent conditions for alum dosing of inflows to these lakes. In addition to sediment total aluminium content, the proportion of amorphous (non-crystalline) aluminium was assessed. Amorphous aluminium is recognised as the fraction of total aluminium able to adsorb dissolved phosphorus, sequestering it from the water column. It was assumed that increased proportions of amorphous aluminium were primarily derived from alum dosing. 
Fifteen sediment cores were taken from Lake Rotorua in December 2020. Previous surveys had reported little aluminium accumulation in the main basin of Lake Rotorua, with aluminium accumulation primarily occurring near the outlet to the Utuhina Stream and the 45 m deep crater north of Motutara Point. Based on this information, coring locations were modified from previous surveys with seven near-shore and crater sites sampled and the number of main basin sites sampled reduced to eight. The background sediment aluminium content for the main basin of Lake Rotorua is approximately 5 g Al kg-1 dry weight. The current survey supports the findings of previous sediment surveys with the main depositional areas for alum derived aluminium being the surface (1–4 cm depth) sediments of Te Ruapeka Bay, which can reach 12 g Al kg⁻¹ and the crater north of Motutara Point at ~8 g Al kg⁻¹. There was no apparent accumulation of aluminium beyond background levels to the east of Sulphur Bay or in the main basin of Lake Rotorua.
In Lake Rotoehu, seven sites were surveyed in December 2020, extending from the mouth of the Waitangi Stream out into the main basin of the lake. Results were similar to those reported by Tempero and Hamilton (2016), with background sediment aluminium content approximately 5-6 g Al kg⁻¹. Alum derived aluminium was primarily accumulating in Te Wairoa
Bay close to the discharge point of the Waitangi Stream with levels exceeding 25 g Al kg⁻¹ However, the two-year cessation of alum dosing resulted in a small decline of ~5 g Al kg⁻¹ in the surface sediments. Despite a five-fold increase in total aluminium content in Te Wairoa Bay over background levels, amorphous aluminium content appears to have declined due to the 2-year halt in alum dosing and aging of alum floc to the mineral gibbsite. There was no evidence of aluminium accumulation in the main basin of Lake Rotoehu.

year: 2021

title: Introducing contrast and luminance normalisation to improve the quality of subtractive resolution merge technique

authors: Ashraf, Muhammad Salman

subjects: image fusion

abstract: Subtractive resolution merge (SRM) is a contemporary image fusion method that produces highly preserved spatial and spectral resolution. This method is limited to dual sensor platforms with specific band ratios between the high-resolution panchromatic image (HRPI) and the low-resolution multispectral image (LRMI). An additional problem with SRM is that some bands are over- or under-represented due to the normalisation function applied. This article provides two modifications that resolve these limitations. SRM builds a synthetic low-resolution panchromatic image (LRPISYN) from the weighted sum of the LRMI bands. This image is modified by using a spatially resampled HRPI instead. The second modification is the use of a contrast and luminance index for the normalising function. These two modifications are tested on QuickBird images (multispectral and panchromatic), as well as fusing SPOT-5 (Satellite Pour l'Observation de la Terre) multispectral image and an aerial photograph. The results show improved quantitative metrics and unsupervised classification compared with the standard SRM technique and other contemporary image fusion methods. Both of these modifications are grouped into a patent pending technique that is called contrast and luminance normalised fusion.

text: Introducing contrast and luminance normalisation to improve the quality of subtractive resolution merge technique Subtractive resolution merge (SRM) is a contemporary image fusion method that produces highly preserved spatial and spectral resolution. This method is limited to dual sensor platforms with specific band ratios between the high-resolution panchromatic image (HRPI) and the low-resolution multispectral image (LRMI). An additional problem with SRM is that some bands are over- or under-represented due to the normalisation function applied. This article provides two modifications that resolve these limitations. SRM builds a synthetic low-resolution panchromatic image (LRPISYN) from the weighted sum of the LRMI bands. This image is modified by using a spatially resampled HRPI instead. The second modification is the use of a contrast and luminance index for the normalising function. These two modifications are tested on QuickBird images (multispectral and panchromatic), as well as fusing SPOT-5 (Satellite Pour l'Observation de la Terre) multispectral image and an aerial photograph. The results show improved quantitative metrics and unsupervised classification compared with the standard SRM technique and other contemporary image fusion methods. Both of these modifications are grouped into a patent pending technique that is called contrast and luminance normalised fusion.

year: 2013

title: Te Karauna Hou: the senior Ngati Rahiri rangatira

authors: Hart, Philip

abstract: Te Karauna Hou, the principal Ngati Rahiri rangatira living at Te Aroha in 1880, had a distinguished whakapapa linking him to several hapu. Before settling permanently at Te Aroha in the 1870s he lived in several places, especially at Kaitawa, on the southern outskirts of Thames. One of the principal rangatira in Hauraki, he was loyal to the Crown during the Waikato War, and later assisted Pakeha settlement. To emphasize his mana and that of his hapu, he held big festivities at Kaitawa and at Omahu pa at Te Aroha. 
In 1871, when Ngati Haua won a (temporary) victory in the land court over the ownership of the Aroha Block, Karauna took control of it on behalf of the Marutuahu confederation, and subsequently kept Ngati Haua at bay. For a time he opposed road-making on this block, but later agreed to it, for financial reasons. Like all rangatira, he sought to maximize his ownership of as many blocks of land as possible, sometimes having his lies exposed through his contradicting his earlier evidence. He also denied receiving money for land when his denials were easily disproved. Despite leasing and selling land, selling timber and gum, and opening his land to miners, he often struggled financially.  
Karauna claimed to have found gold in Hauraki in 1852, and was willing to open his land at Thames to miners, but did not invest in any claims before the Te Aroha rush, when he attempted to extract a bonus of £1,000 from the government for opening the field. After his death in 1885, Pakeha remembered with gratitude his friendly attitude to them, but they also remembered his drunkenness, which meant he lost the respect of both Maori and Pakeha in his latter years.

text: Te Karauna Hou: the senior Ngati Rahiri rangatira Te Karauna Hou, the principal Ngati Rahiri rangatira living at Te Aroha in 1880, had a distinguished whakapapa linking him to several hapu. Before settling permanently at Te Aroha in the 1870s he lived in several places, especially at Kaitawa, on the southern outskirts of Thames. One of the principal rangatira in Hauraki, he was loyal to the Crown during the Waikato War, and later assisted Pakeha settlement. To emphasize his mana and that of his hapu, he held big festivities at Kaitawa and at Omahu pa at Te Aroha. 
In 1871, when Ngati Haua won a (temporary) victory in the land court over the ownership of the Aroha Block, Karauna took control of it on behalf of the Marutuahu confederation, and subsequently kept Ngati Haua at bay. For a time he opposed road-making on this block, but later agreed to it, for financial reasons. Like all rangatira, he sought to maximize his ownership of as many blocks of land as possible, sometimes having his lies exposed through his contradicting his earlier evidence. He also denied receiving money for land when his denials were easily disproved. Despite leasing and selling land, selling timber and gum, and opening his land to miners, he often struggled financially.  
Karauna claimed to have found gold in Hauraki in 1852, and was willing to open his land at Thames to miners, but did not invest in any claims before the Te Aroha rush, when he attempted to extract a bonus of £1,000 from the government for opening the field. After his death in 1885, Pakeha remembered with gratitude his friendly attitude to them, but they also remembered his drunkenness, which meant he lost the respect of both Maori and Pakeha in his latter years.

year: 2016