title: The viability of waste copper chromium and arsenic treated timber reinforced polypropylene as a sustainable building material

authors: Nelson, Jacob Martin Bruton

subjects: Natural fibre composites

abstract: The aim of this thesis was to investigate the viability of wood-plastic composites (WPCs) produced from wood flour and fibre derived from waste copper chromium and arsenic (CCA) treated timber for use as a sustainable material in the construction sector.

The research included an assessment of mechanical properties and the leaching of heavy metals from the wood-plastic composites, and the results were compared to material requirements in the building sector provided through literature and New Zealand building standards. Mechanical and chemical methods were used to prepare wood flour and fibre samples from waste CCA treated timber for use in wood-plastic composites. Composites were produced through compounding using a twin screw extruder or a custom sigma blade compounder and then injection moulded for material testing. Composites produced using an extruder with 40 wt.% bleached fibres and 4 wt.% MAPP, increased tensile strength (TM) from 18.5 MPa for the polypropylene used for the matrix to 27.6 MPa; Young's modulus (YM) was increased from 0.84 GPa to 2.33 GPa.

Comparison of mechanical performance with commercial WPC properties suggests that waste CCA treated timber could be used as a raw material to produce WPC for semi-structural applications. The modulus (2.33 GPa, in the highest performing composites) was roughly three times lower than commonly used commercial timbers used in structural applications. The creep performance was not measured for a time frame long enough to be indicative of the 50 years required for structural application. Therefore, further research is required to investigate whether the low modulus and creep performance of the WPC is acceptable for a structural material in the construction sector.

One of the largest concerns with using waste CCA treated timber as a reinforcement material in WPC was the inclusion of heavy metals and the potential for leaching. Arsenic was considered the most toxic of the heavy metals in the CCA treated timber. Processing of the waste CCA treated timber to obtain fibre was found to reduce arsenic concentration by up to 99.94 % in the best scenario. Furthermore, arsenic in leachate from composites was found to decrease from 41.29 to 0.07 ppb when comparing wood flour composites to digested and bleached fibre composites. The concentration of copper, chromium, and arsenic in leachate from composites produced with chemically obtained fibre was found to be significantly lower than the maximum allowable drinking levels in New Zealand. Therefore, indicating the application of composites produced with wood fibre from waste CCA treated timber can be regarded as safe even in scenarios that involve human contact with the material.

A life cycle analysis study found that the use of an alkali digestion process to obtain fibre significantly increased the environmental impact compared to the processing required to obtain wood flour. In a study of a potential commercial scale process, ultrasonic treatment and hydrogen peroxide bleaching as secondary fibre treatments were the largest contributors to environmental impact in the preparation of wood fibre. Thus, the results suggest that chemical treatments should only be employed to produce wood fibre when the highest mechanical performance or lowest leaching levels are required for the application of the wood-plastic composites.

text: The viability of waste copper chromium and arsenic treated timber reinforced polypropylene as a sustainable building material The aim of this thesis was to investigate the viability of wood-plastic composites (WPCs) produced from wood flour and fibre derived from waste copper chromium and arsenic (CCA) treated timber for use as a sustainable material in the construction sector.

The research included an assessment of mechanical properties and the leaching of heavy metals from the wood-plastic composites, and the results were compared to material requirements in the building sector provided through literature and New Zealand building standards. Mechanical and chemical methods were used to prepare wood flour and fibre samples from waste CCA treated timber for use in wood-plastic composites. Composites were produced through compounding using a twin screw extruder or a custom sigma blade compounder and then injection moulded for material testing. Composites produced using an extruder with 40 wt.% bleached fibres and 4 wt.% MAPP, increased tensile strength (TM) from 18.5 MPa for the polypropylene used for the matrix to 27.6 MPa; Young's modulus (YM) was increased from 0.84 GPa to 2.33 GPa.

Comparison of mechanical performance with commercial WPC properties suggests that waste CCA treated timber could be used as a raw material to produce WPC for semi-structural applications. The modulus (2.33 GPa, in the highest performing composites) was roughly three times lower than commonly used commercial timbers used in structural applications. The creep performance was not measured for a time frame long enough to be indicative of the 50 years required for structural application. Therefore, further research is required to investigate whether the low modulus and creep performance of the WPC is acceptable for a structural material in the construction sector.

One of the largest concerns with using waste CCA treated timber as a reinforcement material in WPC was the inclusion of heavy metals and the potential for leaching. Arsenic was considered the most toxic of the heavy metals in the CCA treated timber. Processing of the waste CCA treated timber to obtain fibre was found to reduce arsenic concentration by up to 99.94 % in the best scenario. Furthermore, arsenic in leachate from composites was found to decrease from 41.29 to 0.07 ppb when comparing wood flour composites to digested and bleached fibre composites. The concentration of copper, chromium, and arsenic in leachate from composites produced with chemically obtained fibre was found to be significantly lower than the maximum allowable drinking levels in New Zealand. Therefore, indicating the application of composites produced with wood fibre from waste CCA treated timber can be regarded as safe even in scenarios that involve human contact with the material.

A life cycle analysis study found that the use of an alkali digestion process to obtain fibre significantly increased the environmental impact compared to the processing required to obtain wood flour. In a study of a potential commercial scale process, ultrasonic treatment and hydrogen peroxide bleaching as secondary fibre treatments were the largest contributors to environmental impact in the preparation of wood fibre. Thus, the results suggest that chemical treatments should only be employed to produce wood fibre when the highest mechanical performance or lowest leaching levels are required for the application of the wood-plastic composites.

year: 2022

title: Determining estuarine seagrass density measures from low altitude multispectral imagery flown by remotely piloted aircraft

authors: Martin, Ross David

subjects: Seagrass

abstract: Seagrass is the subject of significant conservation research. Seagrass is ecologically important and of significant value to human interests. Many seagrass species are thought to be in decline.  Degradation of seagrass populations are linked to anthropogenic environmental issues. Effective management requires robust monitoring that is affordable at large scale. Remote sensing methods using satellite and aircraft imagery enable mapping of seagrass populations at landscape scale. 
Aerial monitoring of a seagrass population can require imagery of high spatial and/or spectral resolution for successful feature extraction across all levels of seagrass density. Remotely piloted aircraft (RPA) can operate close to the ground under precise flight control enabling repeated surveys in high detail with accurate revisit-positioning.
This study evaluates a method for assessing intertidal estuarine seagrass (Zostera muelleri) presence/absence and coverage density using multispectral imagery collected by a remotely piloted aircraft (RPA) flying at 30 m above the estuary surface (2.7 cm ground sampling distance). The research was conducted at Wharekawa Harbour on the eastern coast of the Coromandel Peninsula, North Island, New Zealand.
Differential drainage of residual ebb waters from the surface of an estuary at low tide creates a mosaic of drying sediment, draining surface and static shallow pooling that has potential to interfere with spectral observations. The field surveys demonstrated that despite minor shifts in the spectral coordinates of seagrass and other surface material, there was no apparent difference in image classification outcome from the time of bulk tidal water clearance to the time of returning tidal flood.
For the survey specification tested, classification accuracy increased with decreasing segmentation scale. Pixel-based image analysis (PBIA) achieved higher classification accuracy than object-based image analysis (OBIA) assessed at a range of segmentation scales. Contaminating objects such as shells and detritus can become aggregated within polygon objects when OBIA is applied but remain as isolated objects under PBIA at this image resolution. There was clear separability of spectra for seagrass and sediment, but shell and detritus confounded the classification of seagrass density in some situations.  High density seagrass was distinct from sediment, but classification error arose for sparse seagrass.
Three classifiers (linear discriminant analysis, support vector machine and random forest) and three feature selection options (no selection, collinearity reduction and recursive feature elimination) were assessed for effect on classification performance. The random forest classifier yielded the highest classification accuracy, with no accuracy benefit gained from collinearity reduction or recursive feature elimination. Spectral vegetation indices and texture layers substantially improved classification accuracy. Object geometry made a negligible contribution to classification accuracy using mean-shift segmentation at this image-scale.
The method achieved classification of seagrass density with up to 84% accuracy on a three-tier end-member class scale (low, medium, and high density) when using training data formed using visual interpretation of ground reference photography, and up to 93% accuracy using precisely measured seagrass leaf-area. Visual interpretation agreed with precisely measured seagrass leaf area 88% of the time with some misattribution at mid-density. Visual interpretation was substantially faster to apply than measuring the leaf area. A decile class scale for seagrass density correlated with actual leaf area measures more than the three-tier scale, however, was less accurate for absolute class attribution.
The research demonstrates that seagrass feature extraction from RPA-flown imagery is a feasible and repeatable option for seagrass population monitoring and environmental reporting. Further calibration is required for whole- and multi-estuary application.

text: Determining estuarine seagrass density measures from low altitude multispectral imagery flown by remotely piloted aircraft Seagrass is the subject of significant conservation research. Seagrass is ecologically important and of significant value to human interests. Many seagrass species are thought to be in decline.  Degradation of seagrass populations are linked to anthropogenic environmental issues. Effective management requires robust monitoring that is affordable at large scale. Remote sensing methods using satellite and aircraft imagery enable mapping of seagrass populations at landscape scale. 
Aerial monitoring of a seagrass population can require imagery of high spatial and/or spectral resolution for successful feature extraction across all levels of seagrass density. Remotely piloted aircraft (RPA) can operate close to the ground under precise flight control enabling repeated surveys in high detail with accurate revisit-positioning.
This study evaluates a method for assessing intertidal estuarine seagrass (Zostera muelleri) presence/absence and coverage density using multispectral imagery collected by a remotely piloted aircraft (RPA) flying at 30 m above the estuary surface (2.7 cm ground sampling distance). The research was conducted at Wharekawa Harbour on the eastern coast of the Coromandel Peninsula, North Island, New Zealand.
Differential drainage of residual ebb waters from the surface of an estuary at low tide creates a mosaic of drying sediment, draining surface and static shallow pooling that has potential to interfere with spectral observations. The field surveys demonstrated that despite minor shifts in the spectral coordinates of seagrass and other surface material, there was no apparent difference in image classification outcome from the time of bulk tidal water clearance to the time of returning tidal flood.
For the survey specification tested, classification accuracy increased with decreasing segmentation scale. Pixel-based image analysis (PBIA) achieved higher classification accuracy than object-based image analysis (OBIA) assessed at a range of segmentation scales. Contaminating objects such as shells and detritus can become aggregated within polygon objects when OBIA is applied but remain as isolated objects under PBIA at this image resolution. There was clear separability of spectra for seagrass and sediment, but shell and detritus confounded the classification of seagrass density in some situations.  High density seagrass was distinct from sediment, but classification error arose for sparse seagrass.
Three classifiers (linear discriminant analysis, support vector machine and random forest) and three feature selection options (no selection, collinearity reduction and recursive feature elimination) were assessed for effect on classification performance. The random forest classifier yielded the highest classification accuracy, with no accuracy benefit gained from collinearity reduction or recursive feature elimination. Spectral vegetation indices and texture layers substantially improved classification accuracy. Object geometry made a negligible contribution to classification accuracy using mean-shift segmentation at this image-scale.
The method achieved classification of seagrass density with up to 84% accuracy on a three-tier end-member class scale (low, medium, and high density) when using training data formed using visual interpretation of ground reference photography, and up to 93% accuracy using precisely measured seagrass leaf-area. Visual interpretation agreed with precisely measured seagrass leaf area 88% of the time with some misattribution at mid-density. Visual interpretation was substantially faster to apply than measuring the leaf area. A decile class scale for seagrass density correlated with actual leaf area measures more than the three-tier scale, however, was less accurate for absolute class attribution.
The research demonstrates that seagrass feature extraction from RPA-flown imagery is a feasible and repeatable option for seagrass population monitoring and environmental reporting. Further calibration is required for whole- and multi-estuary application.

year: 2020

title: Association of Single Nucleotide Polymorphisms in Surfactant Protein A and D with Otitis Media.

authors: Barnett, Catherine Margaret Eleanor

subjects: otitis media

abstract: Otitis Media is one of the most common childhood diseases. Recurrent acute otitis media RAOM is characterized by repeated episodes of inflammation of the middle ear in conjunction with middle ear fluid, and often with an inflamed or bulging eardrum. Defective clearance by the Eustachian tube results in mucus build-up and is characteristic of otitis media with effusion (OME). Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, respiratory syncytial virus, and rhinovirus are the most common contributors to otitis media pathogenesis. In New Zealand, OME has been implicated with conductive hearing loss in childhood and has been shown to significantly impact on speech and language development. New Zealand Māori and Polynesian children have displayed significantly higher hearing test failure rates than European-Caucasian children.

The collectins, Surfactant Protein (SP)-A and -D are encoded by three genes (SP-A1, SP-A2, and SP-D) and are host defense proteins present in the middle ear and Eustachian tube. Single nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2 have been associated with increased or decreased susceptibility to otitis media, meningococcal disease, and range of respiratory diseases. Using allele-specific primers and real-time PCR with SYBR  Green I melting curve analysis, four groups of individuals were genotyped for eleven SP-A1, SP-A2, and SP-D SNPs: European-Caucasian individuals with RAOM/OME; New Zealand Māori/Polynesian individuals with RAOM/OME; individuals with meningococcal disease; and a control group. The computer program, Haploview, was employed to perform χ2 analyses and identify statistically significant associations of alleles/haplotypes with RAOM/OME or meningococcal disease.

In the European-Caucasian population, two SP-A1 alleles, one SP-A2 allele, and four haplotypes (CGAGC, 1A3, 1A9, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). Conversely, haplotypes 6A2 and 1A2 were found to be protective against susceptibility to RAOM/OME (P lt; 0.05). In New Zealand Māori and Polynesian individuals, two SP-A1 alleles, three SP-A2 alleles, one SP-D allele, and four haplotypes (6A8, 6A10, 1A3, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). An additional four haplotypes (6A2, 1A0, 1A2, and TA) were determined to be protective against susceptibility to RAOM/OME (P lt; 0.05). However, protective SPA1/SPA2/SPD haplotype 6A2-1A0-TA was significantly under-represented in the New Zealand Māori and Polynesian population (P lt; 0.05). A single allele and haplotype were associated with increased risk of meningococcal disease (P lt; 0.05).

The findings of this study confirm that specific genetic variants of SP-A and SP-D are associated with either increased or decreased risk of developing RAOM and/or OME. Furthermore, it was demonstrated that New Zealand Māori and Polynesian individuals appear to exhibit more haplotypes susceptible to RAOM/OME. This may provide a partial explanation for the higher RAOM/OME-related failure rates of hearing tests in New Zealand Māori and Polynesian children. However, there are numerous socio-economic and environmental factors that also contribute to otitis media pathogenesis which were not considered in this study. The effects of the SP-A1, SP-A2, and SP-D alleles and haplotypes on the bacterial/viral binding efficiencies of SP-A and SP-D need to be investigated by further research, using a large population, to confirm the association with susceptibility or resistance with RAOM/OME.

text: Association of Single Nucleotide Polymorphisms in Surfactant Protein A and D with Otitis Media. Otitis Media is one of the most common childhood diseases. Recurrent acute otitis media RAOM is characterized by repeated episodes of inflammation of the middle ear in conjunction with middle ear fluid, and often with an inflamed or bulging eardrum. Defective clearance by the Eustachian tube results in mucus build-up and is characteristic of otitis media with effusion (OME). Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, respiratory syncytial virus, and rhinovirus are the most common contributors to otitis media pathogenesis. In New Zealand, OME has been implicated with conductive hearing loss in childhood and has been shown to significantly impact on speech and language development. New Zealand Māori and Polynesian children have displayed significantly higher hearing test failure rates than European-Caucasian children.

The collectins, Surfactant Protein (SP)-A and -D are encoded by three genes (SP-A1, SP-A2, and SP-D) and are host defense proteins present in the middle ear and Eustachian tube. Single nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2 have been associated with increased or decreased susceptibility to otitis media, meningococcal disease, and range of respiratory diseases. Using allele-specific primers and real-time PCR with SYBR  Green I melting curve analysis, four groups of individuals were genotyped for eleven SP-A1, SP-A2, and SP-D SNPs: European-Caucasian individuals with RAOM/OME; New Zealand Māori/Polynesian individuals with RAOM/OME; individuals with meningococcal disease; and a control group. The computer program, Haploview, was employed to perform χ2 analyses and identify statistically significant associations of alleles/haplotypes with RAOM/OME or meningococcal disease.

In the European-Caucasian population, two SP-A1 alleles, one SP-A2 allele, and four haplotypes (CGAGC, 1A3, 1A9, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). Conversely, haplotypes 6A2 and 1A2 were found to be protective against susceptibility to RAOM/OME (P lt; 0.05). In New Zealand Māori and Polynesian individuals, two SP-A1 alleles, three SP-A2 alleles, one SP-D allele, and four haplotypes (6A8, 6A10, 1A3, and 1A10) were found to be associated with increased risk of RAOM/OME (P lt; 0.05). An additional four haplotypes (6A2, 1A0, 1A2, and TA) were determined to be protective against susceptibility to RAOM/OME (P lt; 0.05). However, protective SPA1/SPA2/SPD haplotype 6A2-1A0-TA was significantly under-represented in the New Zealand Māori and Polynesian population (P lt; 0.05). A single allele and haplotype were associated with increased risk of meningococcal disease (P lt; 0.05).

The findings of this study confirm that specific genetic variants of SP-A and SP-D are associated with either increased or decreased risk of developing RAOM and/or OME. Furthermore, it was demonstrated that New Zealand Māori and Polynesian individuals appear to exhibit more haplotypes susceptible to RAOM/OME. This may provide a partial explanation for the higher RAOM/OME-related failure rates of hearing tests in New Zealand Māori and Polynesian children. However, there are numerous socio-economic and environmental factors that also contribute to otitis media pathogenesis which were not considered in this study. The effects of the SP-A1, SP-A2, and SP-D alleles and haplotypes on the bacterial/viral binding efficiencies of SP-A and SP-D need to be investigated by further research, using a large population, to confirm the association with susceptibility or resistance with RAOM/OME.

year: 2007