title: The fate and effects of JP-5 fuel in Antarctic soil: A controlled experiment at Scott Base, Antarctica

authors: Holmes, David J.

abstract: Hydrocarbon contamination of Antarctic soils is evident in limited areas where accidental fuel spills have occurred, usually near scientific bases or field camps. To understand the short-term fate and effects of fuel spills on Antarctic soils a contained experiment was established at Scott Base, Antarctica. 
Soil cores (105 x 10.5 cm diameter and 30 cm high) were filled with a sieved fraction(< 6.7 mm) of soil (Typic Anhyorthel), buried to the ground surface, and left to equilibrate over winter. Fuel (60 mL of JP-5, an equivalent depth of 7 mm) was applied in droplets, evenly to each of 63 cores. The remaining 42 cores were kept as controls. Ten cores (five control and five JP-5 treated) were weighed daily to monitor changes in moisture and snowfall, and to quantify the volatile loss of JP-5 fuel. In-situ temperatures (2, 5 and 20 cm depth) of both control and JP-5 treated cores were measured in triplicate at hourly intervals. Cores were destructively sampled in triplicate 0.1, 1, 3, 7, 14, 21, 28, 35, 42, 358, 365, 372, 379, and 397 days after fuel application and samples were returned, frozen, to New Zealand for total petroleum hydrocarbon (TPH) and microbial analyses. 
During destructive core sampling fuel penetration was observed to have reached a mean maximum depth of 15 cm ten days after JP-5 application, and 17 cm after one year. A large proportion (between 35% and 60%) of the fuel applied was lost to volatilisation within six weeks following the spill. The volatile loss of JP-5 fuel, as determined by weighing cores after correcting for moisture addition and evaporation of snowfall was about 9% after 18 hours, 26% after one week, and 35% after six weeks. The TPH content of the soil decreased in the 0-2.5 cm depth range from 46 000 mg kg- 1, two hours after fuel application, to 9 000 mg kg-1 after six weeks. In the depth range from 2.5 cm to the mean maximum depth of fuel penetration the TPH content of the soil decreased from 45 000 mg kg-1 two hours after fuel application to 10 000 mg kg-1 after six weeks. The corresponding volatile loss of JP-5 fuel, as determined from TPH concentrations within the total depth of fuel contaminated soil was about 50% after one week, and 60% after six weeks. Differences in the exact total fuel loss as recorded by weighing cores and TPH were attributed to various errors within each technique. The application of fuel had no measurable effect on soil temperature at 2 cm, 5 cm, and 20 cm depth, even though the surfaces of JP-5 treated cores were visibly darker than the control cores. The colour difference however had decreased markedly after three weeks. 
No differences were observed in the mean numbers of culturable heterotrophic bacteria and hydrocarbon-degrading microbes between JP-5 treated and control cores six weeks after the spill. It is, therefore, inferred that the initial application of fuel was non-toxic to culturable heterotrophic bacteria and hydrocarbondegrading microbes. 
Soil surface albedo measurements were also made over three previously contaminated sites in the Ross Sea region, and were found to be lower where the surface remained darkened by hydrocarbons, compared to nearby controls.

text: The fate and effects of JP-5 fuel in Antarctic soil: A controlled experiment at Scott Base, Antarctica Hydrocarbon contamination of Antarctic soils is evident in limited areas where accidental fuel spills have occurred, usually near scientific bases or field camps. To understand the short-term fate and effects of fuel spills on Antarctic soils a contained experiment was established at Scott Base, Antarctica. 
Soil cores (105 x 10.5 cm diameter and 30 cm high) were filled with a sieved fraction(< 6.7 mm) of soil (Typic Anhyorthel), buried to the ground surface, and left to equilibrate over winter. Fuel (60 mL of JP-5, an equivalent depth of 7 mm) was applied in droplets, evenly to each of 63 cores. The remaining 42 cores were kept as controls. Ten cores (five control and five JP-5 treated) were weighed daily to monitor changes in moisture and snowfall, and to quantify the volatile loss of JP-5 fuel. In-situ temperatures (2, 5 and 20 cm depth) of both control and JP-5 treated cores were measured in triplicate at hourly intervals. Cores were destructively sampled in triplicate 0.1, 1, 3, 7, 14, 21, 28, 35, 42, 358, 365, 372, 379, and 397 days after fuel application and samples were returned, frozen, to New Zealand for total petroleum hydrocarbon (TPH) and microbial analyses. 
During destructive core sampling fuel penetration was observed to have reached a mean maximum depth of 15 cm ten days after JP-5 application, and 17 cm after one year. A large proportion (between 35% and 60%) of the fuel applied was lost to volatilisation within six weeks following the spill. The volatile loss of JP-5 fuel, as determined by weighing cores after correcting for moisture addition and evaporation of snowfall was about 9% after 18 hours, 26% after one week, and 35% after six weeks. The TPH content of the soil decreased in the 0-2.5 cm depth range from 46 000 mg kg- 1, two hours after fuel application, to 9 000 mg kg-1 after six weeks. In the depth range from 2.5 cm to the mean maximum depth of fuel penetration the TPH content of the soil decreased from 45 000 mg kg-1 two hours after fuel application to 10 000 mg kg-1 after six weeks. The corresponding volatile loss of JP-5 fuel, as determined from TPH concentrations within the total depth of fuel contaminated soil was about 50% after one week, and 60% after six weeks. Differences in the exact total fuel loss as recorded by weighing cores and TPH were attributed to various errors within each technique. The application of fuel had no measurable effect on soil temperature at 2 cm, 5 cm, and 20 cm depth, even though the surfaces of JP-5 treated cores were visibly darker than the control cores. The colour difference however had decreased markedly after three weeks. 
No differences were observed in the mean numbers of culturable heterotrophic bacteria and hydrocarbon-degrading microbes between JP-5 treated and control cores six weeks after the spill. It is, therefore, inferred that the initial application of fuel was non-toxic to culturable heterotrophic bacteria and hydrocarbondegrading microbes. 
Soil surface albedo measurements were also made over three previously contaminated sites in the Ross Sea region, and were found to be lower where the surface remained darkened by hydrocarbons, compared to nearby controls.

year: 2002

title: Designing similarity functions

authors: Trigg, Leonard E.

abstract: The concept of similarity is important in many areas of cognitive science, computer science, and statistics. In machine learning, functions that measure similarity between two instances form the core of instance-based classifiers. Past similarity measures have been primarily based on simple Euclidean distance. As machine learning has matured, it has become obvious that a simple numeric instance representation is insufficient for most domains. Similarity functions for symbolic attributes have been developed, and simple methods for combining these functions with numeric similarity functions were devised. This sequence of events has revealed three important issues, which this thesis addresses.

The first issue is concerned with combining multiple measures of similarity. There is no equivalence between units of numeric similarity and units of symbolic similarity. Existing similarity functions for numeric and symbolic attributes have no common foundation, and so various schemes have been devised to avoid biasing the overall similarity towards one type of attribute. The similarity function design framework proposed by this thesis produces probability distributions that describe the likelihood of transforming between two attribute values. Because common units of probability are employed, similarities may be combined using standard methods. It is empirically shown that the resulting similarity functions treat different attribute types coherently.

The second issue relates to the instance representation itself. The current choice of numeric and symbolic attribute types is insufficient for many domains, in which more complicated representations are required. For example, a domain may require varying numbers of features, or features with structural information. The framework proposed by this thesis is sufficiently general to permit virtually any type of instance representation-all that is required is that a set of basic transformations that operate on the instances be defined. To illustrate the framework’s applicability to different instance representations, several example similarity functions are developed. 

The third, and perhaps most important, issue concerns the ability to incorporate domain knowledge within similarity functions. Domain information plays an important part in choosing an instance representation. However, even given an adequate instance representation, domain information is often lost. For example, numeric features that are modulo (such as the time of day) can be perfectly represented as a numeric attribute, but simple linear similarity functions ignore the modulo nature of the attribute. Similarly, symbolic attributes may have inter-symbol relationships that should be captured in the similarity function. The design framework proposed by this thesis allows domain information to be captured in the similarity function, both in the transformation model and in the probability assigned to basic transformations. Empirical results indicate that such domain information improves classifier performance, particularly when training data is limited.

text: Designing similarity functions The concept of similarity is important in many areas of cognitive science, computer science, and statistics. In machine learning, functions that measure similarity between two instances form the core of instance-based classifiers. Past similarity measures have been primarily based on simple Euclidean distance. As machine learning has matured, it has become obvious that a simple numeric instance representation is insufficient for most domains. Similarity functions for symbolic attributes have been developed, and simple methods for combining these functions with numeric similarity functions were devised. This sequence of events has revealed three important issues, which this thesis addresses.

The first issue is concerned with combining multiple measures of similarity. There is no equivalence between units of numeric similarity and units of symbolic similarity. Existing similarity functions for numeric and symbolic attributes have no common foundation, and so various schemes have been devised to avoid biasing the overall similarity towards one type of attribute. The similarity function design framework proposed by this thesis produces probability distributions that describe the likelihood of transforming between two attribute values. Because common units of probability are employed, similarities may be combined using standard methods. It is empirically shown that the resulting similarity functions treat different attribute types coherently.

The second issue relates to the instance representation itself. The current choice of numeric and symbolic attribute types is insufficient for many domains, in which more complicated representations are required. For example, a domain may require varying numbers of features, or features with structural information. The framework proposed by this thesis is sufficiently general to permit virtually any type of instance representation-all that is required is that a set of basic transformations that operate on the instances be defined. To illustrate the framework’s applicability to different instance representations, several example similarity functions are developed. 

The third, and perhaps most important, issue concerns the ability to incorporate domain knowledge within similarity functions. Domain information plays an important part in choosing an instance representation. However, even given an adequate instance representation, domain information is often lost. For example, numeric features that are modulo (such as the time of day) can be perfectly represented as a numeric attribute, but simple linear similarity functions ignore the modulo nature of the attribute. Similarly, symbolic attributes may have inter-symbol relationships that should be captured in the similarity function. The design framework proposed by this thesis allows domain information to be captured in the similarity function, both in the transformation model and in the probability assigned to basic transformations. Empirical results indicate that such domain information improves classifier performance, particularly when training data is limited.

year: 1997

title: Tephras and New Zealand archaeology

authors: Lowe, David J.

subjects: tephrochronology

abstract: Establishing an accurate date for earliest Polynesian settlement in New Zealand is essential for understanding patterns of settlement and associated environmental impacts, and the processes and rates of cultural change in Eastern Polynesia. Tephra deposits from five volcanic centres, together with exotic sea-rafted pumice, provide isochronous constraints on the timing of earliest settlement and human impacts in northern New Zealand. A local basaltic tephra from Rangitoto Island (Auckland) and locally distributed andesitic tephras from Egmont volcano directly date human occupation to c. AD 1400–1450. Distal andesitic tephras (Tufa Trig Formation) from Mt Ruapehu, Tongariro volcanic centre, help constrain the timing of earliest anthropogenic deforestation signals in Hawke's Bay. Sea-rafted Loisels Pumice(s), although of uncertain stratigraphic reliability in places, overlies cultural remains that can be no younger than c. AD 1350 along the east coast, North Island. The regionally extensive rhyolitic Kaharoa Tephra, which erupted from Okataina volcano between c. AD  1300–1390, is the critical “settlement layer” datum for dating prehistory in the North Island: no human artefacts are recorded beneath it and the earliest inferred environmental impacts by humans are dated to c. AD  1280, just prior to its deposition. This maximum date matches the earliest radiocarbon dates derived for both settlement and human impacts from archaeological and natural sites (c. AD 1250), and implies that the onset of deforestation was essentially contemporaneous with initial settlement.
The widespread rhyolitic Taupo Tephra, which erupted from Taupo volcano c. AD 200, provides an isochronous benchmark well before earliest settlement. The tephra may coincide approximately with a putative earlier transient contact in New Zealand based on Pacific rat-bone (Rattus exulans) dates. More precise calendrical dates on the tephras—via dendrochronology or ice-core records or other dating methods—would help refine assessment of the timing of earliest settlement, while extending the distributional range of critical tephra layers, through application of crypto-tephra analysis, could lead to a greater understanding of settlement patterns.

text: Tephras and New Zealand archaeology Establishing an accurate date for earliest Polynesian settlement in New Zealand is essential for understanding patterns of settlement and associated environmental impacts, and the processes and rates of cultural change in Eastern Polynesia. Tephra deposits from five volcanic centres, together with exotic sea-rafted pumice, provide isochronous constraints on the timing of earliest settlement and human impacts in northern New Zealand. A local basaltic tephra from Rangitoto Island (Auckland) and locally distributed andesitic tephras from Egmont volcano directly date human occupation to c. AD 1400–1450. Distal andesitic tephras (Tufa Trig Formation) from Mt Ruapehu, Tongariro volcanic centre, help constrain the timing of earliest anthropogenic deforestation signals in Hawke's Bay. Sea-rafted Loisels Pumice(s), although of uncertain stratigraphic reliability in places, overlies cultural remains that can be no younger than c. AD 1350 along the east coast, North Island. The regionally extensive rhyolitic Kaharoa Tephra, which erupted from Okataina volcano between c. AD  1300–1390, is the critical “settlement layer” datum for dating prehistory in the North Island: no human artefacts are recorded beneath it and the earliest inferred environmental impacts by humans are dated to c. AD  1280, just prior to its deposition. This maximum date matches the earliest radiocarbon dates derived for both settlement and human impacts from archaeological and natural sites (c. AD 1250), and implies that the onset of deforestation was essentially contemporaneous with initial settlement.
The widespread rhyolitic Taupo Tephra, which erupted from Taupo volcano c. AD 200, provides an isochronous benchmark well before earliest settlement. The tephra may coincide approximately with a putative earlier transient contact in New Zealand based on Pacific rat-bone (Rattus exulans) dates. More precise calendrical dates on the tephras—via dendrochronology or ice-core records or other dating methods—would help refine assessment of the timing of earliest settlement, while extending the distributional range of critical tephra layers, through application of crypto-tephra analysis, could lead to a greater understanding of settlement patterns.

year: 2000