title: Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy

authors: Huang, Doreen Yu-Tuan

subjects: Science & Technology

abstract: Allophanic tephra-derived soils can sequester sizable quantities of soil organic matter (SOM). However, no studies have visualized the fine internal porous structure of allophanic soil microaggregates, nor studied the carbon structure preserved in such soils or paleosols. We used synchrotron radiation-based transmission X-ray microscopy (TXM) to perform 3D-tomography of the internal porous structure of dominantly allophanic soil microaggregates, and carbon near-edge X-ray absorption fine-structure (C NEXAFS) spectroscopy to characterize SOM in ≤ 12,000-year-old tephra-derived allophane-rich (with minor ferrihydrite) paleosols. The TXM tomography showed a vast network of internal, tortuous nano-pores within an allophanic microaggregate comprising nanoaggregates. SOM in the allophanic paleosols at four sites was dominated by carboxylic/carbonyl functional groups with subordinate quinonic, aromatic, and aliphatic groups. All samples exhibited similar compositions despite differences between the sites. That the SOM does not comprise specific types of functional groups through time implies that the functional groups are relict. The SOM originated at the land/soil surface: ongoing tephra deposition (intermittently or abruptly) then caused the land-surface to rise so that the once-surface horizons were buried more deeply and hence became increasingly isolated from inputs by the surficial/modern organic cycle. The presence of quinonic carbon, from biological processes but vulnerable to oxygen and light, indicates the exceptional protection of SOM and bio-signals in allophanic paleosols, attributable both to the porous allophane (with ferrihydrite) aggregates that occlude the relict SOM from degradation, and to rapid burial by successive tephra-fallout, as well as strong Al-organic chemical bonding. TXM and C NEXAFS spectroscopy help to unravel the fine structure of soils and SOM and are of great potential for soil science studies.

text: Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy Allophanic tephra-derived soils can sequester sizable quantities of soil organic matter (SOM). However, no studies have visualized the fine internal porous structure of allophanic soil microaggregates, nor studied the carbon structure preserved in such soils or paleosols. We used synchrotron radiation-based transmission X-ray microscopy (TXM) to perform 3D-tomography of the internal porous structure of dominantly allophanic soil microaggregates, and carbon near-edge X-ray absorption fine-structure (C NEXAFS) spectroscopy to characterize SOM in ≤ 12,000-year-old tephra-derived allophane-rich (with minor ferrihydrite) paleosols. The TXM tomography showed a vast network of internal, tortuous nano-pores within an allophanic microaggregate comprising nanoaggregates. SOM in the allophanic paleosols at four sites was dominated by carboxylic/carbonyl functional groups with subordinate quinonic, aromatic, and aliphatic groups. All samples exhibited similar compositions despite differences between the sites. That the SOM does not comprise specific types of functional groups through time implies that the functional groups are relict. The SOM originated at the land/soil surface: ongoing tephra deposition (intermittently or abruptly) then caused the land-surface to rise so that the once-surface horizons were buried more deeply and hence became increasingly isolated from inputs by the surficial/modern organic cycle. The presence of quinonic carbon, from biological processes but vulnerable to oxygen and light, indicates the exceptional protection of SOM and bio-signals in allophanic paleosols, attributable both to the porous allophane (with ferrihydrite) aggregates that occlude the relict SOM from degradation, and to rapid burial by successive tephra-fallout, as well as strong Al-organic chemical bonding. TXM and C NEXAFS spectroscopy help to unravel the fine structure of soils and SOM and are of great potential for soil science studies.

year: 2021

title: Identifying and classifying broader scale of disaster impacts to better inform disaster management policies and practice

authors: Tennakoon, Kishani

abstract: Disasters are often assessed by factors such as their magnitude, severity and impact on affected communities. Typically, disaster management policies are largely informed by learnings from large-scale disasters. Many studies, however, have shown that cumulative smaller scale disaster impacts have similar outcomes comparable to larger scale disasters. This indirectly contributes to a lack of consistency in and paucity of data related to both smaller-scale disasters and their associated cumulative impacts. This paper argues that greater attention needs to be paid to collecting disaster impact data on a range of disaster-scale events along with their cumulative impacts to better inform disaster management policies and practice. The paper aims to test the hypothesis that a better understanding of a wide range of disaster scale types and their impacts on communities, including small-scale disasters, enables the development of more just, consistent and equitable disaster management policies and practice. Analysing economic costs, evacuation and rainfall data from past flood events that affected Aotearoa-New Zealand over the last three decades, the paper found discrepancies and lack of coherence in disaster data collection and reporting, along with a predominant reliance on rainfall intensity data for disaster risk reduction and planning. The findings also confirmed the importance of identifying economic damages for a range of disaster scales, including those from small-scale disasters. This highlights the need for developing a spectrum to better classify and identify disaster impacts based on various spatial and temporal contexts. The paper concludes by affirming that such database would provide much needed evidence for developing a methodology that enables the identification of the level of disaster impacts; thereby guiding the implementation of more just, consistent and equitable disaster management policies and practice.

text: Identifying and classifying broader scale of disaster impacts to better inform disaster management policies and practice Disasters are often assessed by factors such as their magnitude, severity and impact on affected communities. Typically, disaster management policies are largely informed by learnings from large-scale disasters. Many studies, however, have shown that cumulative smaller scale disaster impacts have similar outcomes comparable to larger scale disasters. This indirectly contributes to a lack of consistency in and paucity of data related to both smaller-scale disasters and their associated cumulative impacts. This paper argues that greater attention needs to be paid to collecting disaster impact data on a range of disaster-scale events along with their cumulative impacts to better inform disaster management policies and practice. The paper aims to test the hypothesis that a better understanding of a wide range of disaster scale types and their impacts on communities, including small-scale disasters, enables the development of more just, consistent and equitable disaster management policies and practice. Analysing economic costs, evacuation and rainfall data from past flood events that affected Aotearoa-New Zealand over the last three decades, the paper found discrepancies and lack of coherence in disaster data collection and reporting, along with a predominant reliance on rainfall intensity data for disaster risk reduction and planning. The findings also confirmed the importance of identifying economic damages for a range of disaster scales, including those from small-scale disasters. This highlights the need for developing a spectrum to better classify and identify disaster impacts based on various spatial and temporal contexts. The paper concludes by affirming that such database would provide much needed evidence for developing a methodology that enables the identification of the level of disaster impacts; thereby guiding the implementation of more just, consistent and equitable disaster management policies and practice.

year: 2024

title: Microbiological quality of Toroi:  A Māori food delicacy

authors: Dixon, Lorraine Louise

subjects: Maori

abstract: A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

text: Microbiological quality of Toroi:  A Māori food delicacy A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

year: 2007