title: Sulphate partitioning into calcite: Experimental verification of pH control and application to seasonality in speleothems

authors: Wynn, Peter M.

subjects: Science & Technology

abstract: Carbonate-associated sulphate (CAS) is a useful carrier of palaeoenvironmental information throughout the geologic record, particularly through its stable isotope composition. However, a paucity of experimental data restricts quantitative understanding of sulphate incorporation into carbonates, and consequently CAS concentrations and their diagenetic modifications are rarely interpreted. However, in the case of calcite speleothems, the remarkably high-resolution CAS records which are obtainable via modern microanalytical techniques represent a potentially invaluable source of palaeoenvironmental information. Here, we describe the results of controlled experiments of sulphate co-precipitation with calcite in freshwater solutions where pH, saturation state, and sulphate concentration were varied independently of each other. Solution pH is confirmed as the principal control on sulphate incorporation into calcite. The relative efficiency of incorporation was calculated as a partition coefficient Dₛₒ₄=(mSO₄/mCO₃)solid/(mSO₄/mCO₃)solution. High crystal growth rates (driven by either pH or saturation state) encouraged higher values of Dₛₒ₄ because of an increasing concentration of defect sites on crystal surfaces. At low growth rates, Dₛₒ₄ was reduced due to an inferred competition between sulphate and bicarbonate at the calcite surface. These experimental results are applied to understand the incorporation of sulphate into speleothem calcite. The experimentally determined pH-dependence suggests that strong seasonal variations in cave air PCO₂ could account for annual cycles in sulphate concentration observed in stalagmites. Our new experimentally determined values of Dₛₒ₄ were compared with Dₛₒ₄ values calculated from speleothem-drip water monitoring from two caves within the Austrian and Italian Alps. At Obir cave, Austria, Dₛₒ₄ (×10⁵) varies between 11.1 (winter) and 9.0 (summer) and the corresponding figures for Ernesto cave, Italy, are 15.4 (winter) and 14.9 (summer). These values approximate predicted Dₛₒ₄ values based on our chamber experiments containing both low (2 ppm) and high (20 ppm) sulphate concentrations. Our experimental values of Dₛₒ₄ obtained at crystal growth rates typical of stalagmites, closely match those observed in other cave sites from around the world. This validates the universality of the controls behind Dₛₒ₄ and will enhance the use of speleothem CAS as a palaeoenvironmental proxy.

text: Sulphate partitioning into calcite: Experimental verification of pH control and application to seasonality in speleothems Carbonate-associated sulphate (CAS) is a useful carrier of palaeoenvironmental information throughout the geologic record, particularly through its stable isotope composition. However, a paucity of experimental data restricts quantitative understanding of sulphate incorporation into carbonates, and consequently CAS concentrations and their diagenetic modifications are rarely interpreted. However, in the case of calcite speleothems, the remarkably high-resolution CAS records which are obtainable via modern microanalytical techniques represent a potentially invaluable source of palaeoenvironmental information. Here, we describe the results of controlled experiments of sulphate co-precipitation with calcite in freshwater solutions where pH, saturation state, and sulphate concentration were varied independently of each other. Solution pH is confirmed as the principal control on sulphate incorporation into calcite. The relative efficiency of incorporation was calculated as a partition coefficient Dₛₒ₄=(mSO₄/mCO₃)solid/(mSO₄/mCO₃)solution. High crystal growth rates (driven by either pH or saturation state) encouraged higher values of Dₛₒ₄ because of an increasing concentration of defect sites on crystal surfaces. At low growth rates, Dₛₒ₄ was reduced due to an inferred competition between sulphate and bicarbonate at the calcite surface. These experimental results are applied to understand the incorporation of sulphate into speleothem calcite. The experimentally determined pH-dependence suggests that strong seasonal variations in cave air PCO₂ could account for annual cycles in sulphate concentration observed in stalagmites. Our new experimentally determined values of Dₛₒ₄ were compared with Dₛₒ₄ values calculated from speleothem-drip water monitoring from two caves within the Austrian and Italian Alps. At Obir cave, Austria, Dₛₒ₄ (×10⁵) varies between 11.1 (winter) and 9.0 (summer) and the corresponding figures for Ernesto cave, Italy, are 15.4 (winter) and 14.9 (summer). These values approximate predicted Dₛₒ₄ values based on our chamber experiments containing both low (2 ppm) and high (20 ppm) sulphate concentrations. Our experimental values of Dₛₒ₄ obtained at crystal growth rates typical of stalagmites, closely match those observed in other cave sites from around the world. This validates the universality of the controls behind Dₛₒ₄ and will enhance the use of speleothem CAS as a palaeoenvironmental proxy.

year: 2018

title: Some inconvenient truths about education in Aotearoa-New Zealand

authors: Thrupp, Martin

subjects: poverty

abstract: How does poverty affect New Zealand children’s schooling? Answers to this question generally revolve around three perspectives. First, it is argued that the children of families in poverty in New Zealand are disadvantaged in schools because of the level and nature of their family resources. Such resources can be both material and cultural: ill health, poor nutrition, overcrowding and transience, fewer curriculum relevant experiences, limited literacy and little early childhood education all reduce the ability of children to progress at school (Biddulph, J, & Biddulph, 2003; Nash, 1993). Second, it is argued that schools serving poorer areas are under-resourced. This applies more to places such as the USA, where school funding depends on the tax-base of local districts (Kozol, 1991), than to New Zealand, where schools are funded nationally and extra funding is provided for low socio-economic “low-decile” schools. Nevertheless underfunding, or the method of funding, of low-decile schools remains an issue in New Zealand, both because of relatively low parent and community contributions in such schools, and because of the sheer scale of their students’ needs. A third perspective is that poor teaching and ineffective schools are the problem, rather than poverty. Yet quality teaching and school improvement cannot be divorced from the social context. Low socio-economic schools often find it difficult to recruit permanent, long-term teaching staff. Teachers at low-socio-economic schools struggle more to meet the learning needs of children and spend a lot more time on pastoral care than in those middle class settings (Thrupp, 1999).

text: Some inconvenient truths about education in Aotearoa-New Zealand How does poverty affect New Zealand children’s schooling? Answers to this question generally revolve around three perspectives. First, it is argued that the children of families in poverty in New Zealand are disadvantaged in schools because of the level and nature of their family resources. Such resources can be both material and cultural: ill health, poor nutrition, overcrowding and transience, fewer curriculum relevant experiences, limited literacy and little early childhood education all reduce the ability of children to progress at school (Biddulph, J, & Biddulph, 2003; Nash, 1993). Second, it is argued that schools serving poorer areas are under-resourced. This applies more to places such as the USA, where school funding depends on the tax-base of local districts (Kozol, 1991), than to New Zealand, where schools are funded nationally and extra funding is provided for low socio-economic “low-decile” schools. Nevertheless underfunding, or the method of funding, of low-decile schools remains an issue in New Zealand, both because of relatively low parent and community contributions in such schools, and because of the sheer scale of their students’ needs. A third perspective is that poor teaching and ineffective schools are the problem, rather than poverty. Yet quality teaching and school improvement cannot be divorced from the social context. Low socio-economic schools often find it difficult to recruit permanent, long-term teaching staff. Teachers at low-socio-economic schools struggle more to meet the learning needs of children and spend a lot more time on pastoral care than in those middle class settings (Thrupp, 1999).

year: 2008

title: Kia Maanu, Kia Ora: Stay Afloat, Stay Alive – Acknowledging the significance of tikanga Māori in formulating and communicating water safety policies and practices

authors: Haimona, Mark

subjects: New Zealand

abstract: The traditional beliefs and practices of Māori demonstrate great respect for water, for its dangers as well as its life-giving properties, and Māori have, along with other Polynesian peoples, been known for their skill in swimming, fishing and canoeing. However, Māori now outnumber others in New Zealand in terms of the proportion involved in drowning and water-related injury. In seeking to promote water safety among Māori, Water Safety New Zealand has enlisted the help of Māori communities. Its message - Kia Maanu, Kia Ora (Stay Afloat, Stay Alive) - is underpinned by an acknowledgment of the need to reinforce the traditional respect for water that permeates the Māori worldview.

text: Kia Maanu, Kia Ora: Stay Afloat, Stay Alive – Acknowledging the significance of tikanga Māori in formulating and communicating water safety policies and practices The traditional beliefs and practices of Māori demonstrate great respect for water, for its dangers as well as its life-giving properties, and Māori have, along with other Polynesian peoples, been known for their skill in swimming, fishing and canoeing. However, Māori now outnumber others in New Zealand in terms of the proportion involved in drowning and water-related injury. In seeking to promote water safety among Māori, Water Safety New Zealand has enlisted the help of Māori communities. Its message - Kia Maanu, Kia Ora (Stay Afloat, Stay Alive) - is underpinned by an acknowledgment of the need to reinforce the traditional respect for water that permeates the Māori worldview.

year: 2007