Heavy Metal Pollutants in Snow and Ice from Roosevelt Island, Antarctica Andrea Jean Tuohy

161 Pages·2015·8.44 MB·English

by  Andrea Tuohy

Heavy Metal Pollutants in Snow and Ice from
Roosevelt Island, Antarctica

By

Andrea Jean Tuohy
300104536

A thesis submitted to the Victoria University of Wellington in fulfilment of
the requirements for the degree of Doctor of Philosophy

Victoria University of Wellington
2015
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Frontispiece – Setting up for ice core drilling at Roosevelt Island, during field season 2011-
2012. Photo: Sepp Kipfstuhl.

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Abstract

Global industrialization has led to emissions of heavy metal pollutants that are transported to
the most remote areas of the planet. Elevated concentrations of heavy metals are ecological
toxins in soils, water, and air. Monitoring has only been implemented during the last few
decades with anthropogenic emissions superimposed over natural sources. Furthermore, most
monitoring programs generally target local sources of emissions near cities rather than large-
scale impacts. Thus quantifying safe limits and controlling industrial emissions is
complicated by a lack of knowledge about natural sources and variability on regional,
hemispheric, and global scales. New baseline studies are needed to determine i) natural
background concentrations of heavy metals, ii) contributions of anthropogenic emissions, and
iii) the degree to which atmospheric transport affects background heavy metal concentrations.
Due to the remoteness of Antarctica, ice cores can be used as sensitive recorders of
background heavy metal atmospheric concentrations over thousands of years. This provides
the opportunity to determine natural variability and contributions to the atmosphere on a
hemispheric scale, as well as dating the onset of anthropogenic emissions.

This thesis presents a 2,300-year time-series record of six heavy metals from a new high-
resolution coastal ice core from the Ross Sea region of Antarctica. Roosevelt Island is an ice
dome located in the north-eastern Ross Ice Shelf, and a 763m deep ice core was collected
over two field seasons as part of the Roosevelt Island Climate Evolution (RICE) project. In
addition to 31 other trace elements, concentrations of iron, aluminium, manganese, lead,
arsenic, and thallium were measured using inductively coupled plasma mass spectrometry
(ICPMS) in the RICE ice core, snow pit, and snow precipitation samples. Sample resolution
over the 20th century is extremely high (~1.6 months per sample), with ~four-year resolution
extending the record back to 2,300 years ago.

We use this record to first determine the representativeness of the RICE ice core to Southern
Hemisphere atmospheric concentrations of heavy metals, and find that concentrations in
snow precipitation are strongly linked to meridional air mass pathways from the South
Pacific. Local deposition characteristics and heavy metal seasonality are also examined in the
surface snow. The natural sources and variability of the six heavy metals are explored
through the last ~2,000 years, and this provides the context for examining changes over the
20th century. We find that iron, aluminium, and manganese are strongly associated with
crustal dust and do not exhibit source changes over the 20th century, though significant
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increases in concentration may be due to anthropogenically induced increases in atmospheric
dust. Even when increased variability due to recent increased efficiency of atmospheric
transport is taken into account, the change in source emission strength dominates the
concentration increases in these elements recorded in the RICE ice core. Thallium
concentrations do not increase over the 20th century, and are likely linked to local volcanism.
Both lead and arsenic concentrations increase significantly over the 20th century, with the
pattern in lead concentrations closely matching existing Antarctic records. These increases
are linked to anthropogenic emissions, with peaks during the 1970s and 1980s up to 400%
higher than pre-industrial concentrations – well outside the natural variability. However, the
ice core record shows a decreasing trend in concentrations of these elements from the mid-
1990s to the present. Arsenic concentrations return to within pre-industrial variability, and
the timing of this trend coincides with increasing efforts of policy makers in Southern
Hemisphere countries to regulate industrial emissions and to promote public awareness of
heavy metal pollutants.

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Acknowledgements

First thanks go to my supervisors Nancy Bertler, Ross Edwards, and Dan Sinclair, for both
the opportunity to work on this project and for all the support throughout it. This has been a
great experience for me, and has challenged me to learn many new skills. In particular,
thanks to Nancy for your unquestioning support and confidence, and to Ross for your
generosity with time, expertise, and lab equipment.

Special thanks go to Peter Neff. I couldn’t have asked for a better colleague or friend to share
all the sample prep, lab time (failures and successes) and analyses. I would also like to thank
my other office mates Heidi Roop, Molly Patterson and Daniel Emanuelsson for sharing your
friendship and support and beer.

Thanks to the 2011-2012 RICE field team for making my first season in Antarctica such a
great experience; and also to the 2012 and 2013 ice core processing teams for your
comradeship through the months of shift work.

I would also like to acknowledge the wider RICE community; I’ve enjoyed working with you
on the age scale and sharing results. I also want to thank the other staff and students in the
ARC for your support and good advice both around the lunch-table and for being available
whenever I had questions.

Finally thanks to my all family, both in Christchurch and Wellington, and particularly to
Oliver Tuohy for your love, understanding, support and advice. You are the foundation from
which I draw happiness and strength.

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Table of Contents

Frontispiece…………………………………………………………………………………iii
Abstract……………………………………………………………………………………...v
Acknowledgements………………………………………………………………………...vii
Table of Contents……………………………………………………………………….....viii
List of Figures………………………………………………………………………………xi
List of Tables…………………………………………………………………………...…xiii
Foreword…………………………………………………………………………………….1
Chapter 1: Introduction and Background
1.1 Introduction………………………………………………………………….3
1.2 Research aims………………………………………………………………..5
1.3 Background concepts from the literature……………………………………5
1.3.1 Antarctic climate………………………………………………………….7
1.3.2 Atmospheric transport…………………………………………………...10
1.3.3 Major and trace elements………………………………………………...13
1.4 Conclusions…………………………………………………………………16
Chapter 2: Roosevelt Island Climate Evolution Project
2.1 Introduction…………………………………………………………………19
2.2 Science support……………………………………………………………..20
2.3 Field seasons………………………………………………………………..20
2.4 RICE ice core analysis over view…………………………………………..21
2.5 RICE ice core processing summary………………………………………...22
2.6 RICE age scale……………………………………………………………...23
Chapter 3: Analytical Methods and Data Processing
3.1 Introduction…………………………………………………………………27
3.2 Sample and standard preparation…………………………………………...27
3.3 Acidification and leaching experiment……………………………………..28
3.3.1 Results…………………………………………………………………....33
3.4 ICPMS set up and sample analysis…………………………………………34
3.4.1 Quality of ICPMS measurements………………………………………...38
3.4.2 Limits of quantification and concentration in Antarctic ice samples…….40
3.5 Analysis of plutonium isotopes……………………………………………..43
3.6 Data processing……………………………………………………………..44
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Chapter 4: Transport and Deposition of Toxic Heavy Metals in the Ross Sea Region,
Antarctica
4.1 Foreword…………………………………………………………………...45
4.2 Abstract…………………………………………………………………….46
4.3 Introduction………………………………………………………………...46
4.4 Methods…………………………………………………………………….48
4.4.1 Snow precipitation sampling…………………………………………….48
4.4.2 Snow pit sampling methods……………………………………………..49
4.4.3 ICPMS analysis of snow precipitation and snow pit samples…………...50
4.5 Results and discussion……………………………………………………...52
4.5.1 Snow precipitation at Roosevelt Island………………………………….52
4.5.2 Scavenging efficiency of different snow precipitation…………………..54
4.5.3 Back trajectory modelling………………………………………………..56
4.6 Snowpack dating……………………………………………………………60
4.7 Snowpack concentration and flux…………………………………………..61
4.8 Conclusions…………………….…………………………………………...66
4.9 References…………………………………………………………………..67
4.10 Supplementary information….……………………………………………...72
Chapter 5: 20th Century Arsenic Pollution: A record of anthropogenic emissions and recent
decreases
5.1 Foreword…………………………………………………………………..75
5.2 Introduction………………………………………………………………..75
5.3 Results and discussion…………………………………………………….77
5.3.1 Sources of pre-industrial arsenic………………………………………..79
5.3.2 Arsenic over the 20th Century…………………………………………..81
5.4 Methods…………………………………………………………………...83
5.5 References………………………………………………………………....85
5.6 Supplementary Figures and Tables………………………………………..88
Chapter 6: Heavy Metal Pollutants over the last 2,000 years at Roosevelt Island, Antarctica
6.1 Foreword………………………………………………………………….91
6.2 Abstract…………………………………………………………………...91
6.3 Introduction……………………………………………………………….92
6.4 Methods…………………………………………………………………...93
6.4.1 RICE age scale……………………………………………………95
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6.5 Results and discussion…………………………………………………....96
6.5.1 Metal concentrations and variability…………………………………...98
6.5.2 Heavy metal sources……………………………………………………99
6.5.3 20th Century Source Changes…………………………………………101
6.6 Conclusions……………………………………………………………...105
6.7 References……………………………………………………………….106
Chapter 7: Summary and Conclusions…………………………………………………..111
7.1 Future Directions………………………………………………………...115
Thesis References………………………………………………………………………..117
Appendix A………………………………………………………………………………127

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