Content uploaded by Archana Dayal
Author content
All content in this area was uploaded by Archana Dayal on Feb 28, 2019
Content may be subject to copyright.
ANALYSIS AND QUANTIFICATION OF DUST IN
ANTARCTIC SNOW: A CASE STUDY FROM PRINCESS
ELIZABETH LAND AND DRONNING MAUD LAND
Submitted by
ARCHANA DAYAL
For the partial fulfillment of the
Degree of Master of Science in
CLIMATE SCIENCE & POLICY
Submitted to
Department of Natural Resource
TERI University
(July 2012)
Work carried out at:
National Centre for Antarctic and Ocean Research
Acknowledgement
First and foremost, I thank the Almighty for having bestowed his blessings on me which helped me complete
my project successfully.
I am highly indebted to Dr. R. Ravindra, Director, National Centre for Antarctic and Ocean Research
(NCAOR), Goa, for graciously accepting my application for the internship.
I am deeply grateful to Dr. Thamban Meloth, Scientist ‘E’, Head, Ice Core Laboratory, NCAOR for believing
in me and giving an opportunity to work in the laboratory. I would also like to express my sincere thanks for
the constructive criticism and valuable suggestions provided for the completion of my project. His ready help
and counsel added great value to my work.
I convey my deep gratitude to Dr. Rahul Mohan, Scientist ‘D’, NCAOR. His welcoming and positive attitude
was instrumental in arousing my interest in this discipline of science.
I wish to express my deepest gratitude to Mr. Mahalinganathan K., Research Scientist ‘B’, NCAOR for his
tremendous contribution in the completion of my minor project. He freely shared his knowledge and was very
encouraging even when I made mistakes. Without his help, advice and guidance, even at inconvenient times, I
would not have been able to do justice to this project.
I also owe a great debt of gratitude to Dr. K.P. Krishnan, Scientist ‘C’ , NCAOR who urged me to follow my
heart and take up work in which I was interested. His patient counselling helped put me on the right track
during my early days at NCAOR.
I thank Ms. Sunaina Wadekar, Project Assistant, NCAOR for familiarising me with the working of the
instruments.
I sincerely thank Mr. Rupesh Sinha, (Senior Research Fellow), NCAOR who put me through the early steps in
cryobiology.
I wish to thank Mr. Puneet Parmar, Technical Specialist, Beckman Coulter, New Delhi for patiently replying
to my queries.
I also wish to thank my seniors Ms. Gauri G. Bandekar and Mr. Akshaya Verma (These students had worked
at NCAOR earlier and I took help from their reports).
I also wish to thank my friend, Swastika Issar who taught me how to interact with people. By observing her I
learnt to persevere and ask questions to improve my understanding.
Last but not the least I would like to thank my family for their tremendous support and encouragement.
CONTENTS
ABSTRACT
1. INTRODUCTION
1
1.1. Antarctica: Background and Exploration
1
1.2. Antarctica: Geography and Climate
2
1.3. National Centre for Antarctic and Ocean Research
3
1.4. India in Antarctica
5
1.5. A background on snow core studies
8
2. SAMPLING AND METHODOLOGY
13
a. Snow core sampling
13
b. Methodology:
2.2.1. Beckman Coulter Counter (MS4)
14
2.2.2. Particle analyses of snow cores
19
3. RESULTS
21
4. DISCUSSION AND CONCLUSION
22
5. REFERENCES
6. ANNEXURE
30
ABSTRACT
Ice sheets of Antarctica, holding fingerprints of past atmospheric events, are considered as a
barometer of global climate change. Atmospheric dust concentration in ice cores provides a direct
and reliable proxy indicator of past changes in the atmospheric composition and climate. Reliable
measurements of dust in the modern snow deposits are vital for understanding their utility for past
climate reconstruction. With this understanding, the particle mass concentration and size range
distribution of dust particles was measured from 12 snow cores (213 sub- samples) retrieved from
a Princess Elizabeth Land (PEL) transect and 7 snow cores (111 sub-samples) from a central
Dronning Maud Land (DML) transect. The spatial variation in the PEL shows a decreasing particle
mass concentration towards inland region of the transect. The particle size ranged between 2 and 3
µm. The coastal section of PEL showed an average particle mass concentration of 174 µg l-1 and
DML 140 µg l-1. The inland region of PEL transect showed an average particle mass concentration
of 141 µg l-1 and DML, 120 µg l-1. Dust flux ranged between 80 kg.km-2.a-1 and 106 kg.km-2.a-1 for
PEL and 16 kg.km-2.a-1, 648 kg.km-2.a-1 for DML. The summer dust flux tends to be on a higher
average when compared with the winter in DML and PEL. Possible sources, spatial and seasonal
variations of dust have been analysed in the present study.
Keywords: Dust, Snow, Princess Elizabeth Land, Dronning Maud Land, Antarctica
1
1. INTRODUCTION
1.1. Antarctica: Background and Exploration
Antarctica is Earth's southernmost continent, containing the geographic South Pole. It is
situated in the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is
surrounded by the Southern Ocean. It is the coldest, driest (precipitation, roughly 2 inches
per year) (www.usap.gov), harshest and windiest continent, and has the highest average
elevation of all the continents (2500 m; the average elevation of Australia is only 340 m)
(Statistics, Norway, 2011).
Fig. 1: Map of Antarctica with major geographical features
Myths and speculation about a Terra Australis ("Southern Land") date back to antiquity.
The idea of earthly balance gave rise to the name Antarktos, or Antarctica, which means
"opposite Artkos" the constellation in the northern sky, also meaning "opposite to the
2
Arctic" (andrill.org). The first confirmed sighting of the continent is commonly accepted to
have occurred in 1820 by the Russian expedition of Fabian Gottlieb von Bellingshausen and
Mikhail Lazarev on the ships Vostok and Mirnyi. The continent, however, remained largely
neglected for the rest of the 19th century because of its hostile environment, lack of
resources, and isolation.
The initial impetus for the “heroic age” of Antarctic exploration came from a lecture given to
the Royal Geographical Society in London in 1893, by Professor John Murray of the
Challenger oceanographic expedition, which had sailed to Antarctic waters in 1872–76. He
proposed that a new Antarctic expedition should be organized to "resolve the outstanding
geographical questions still posed in the south". This “Heroic Age” defines an era which
extended from the end of the 19th century to the early 1920s. During this 25-year period the
Antarctic continent became the focus of an international effort which resulted in intensive
scientific and geographical exploration. Sixteen major Antarctic expeditions were launched
from eight different countries during this age. The common factor in these expeditions was
the limited nature of the resources available to them before advances in transport and
communication technologies revolutionized the work of exploration. This meant that each
expedition became a feat of endurance that tested its personnel to physical and mental
limits, and sometimes beyond. The "heroic" label, bestowed later, recognized the adversities
which had to be overcome by these pioneers, some of whom did not survive the experience.
As a result of all this activity, much of the continent's coastline was discovered and mapped,
and significant areas of its interior were explored. The expeditions also generated large
quantities of scientific data and specimens across a wide range of scientific disciplines, the
examination and analysis of which would keep the world's scientific communities busy for
decades.
Captain Roald Amundsen, a Norwegian polar explorer led the Antarctic expedition to
discover the South Pole in December 1911 and he was the first expedition leader to
undisputedly reach the North Pole in 1926. Other polar explorers whose undefeated human
spirit led to the discovery and exploration of Antarctica are Douglas Mawson, Robert Falcon
Scott and Ernest Shackleton. Shackleton’s “Endurance” expedition is sometimes referred to
as the last Antarctic expedition of the heroic age.
1.2. Antarctica: Geography and Climate
Location: The continent is situated in the Southern Hemisphere, almost entirely south of
the Antarctic Circle, and is surrounded by the vast Southern Ocean.
3
Area: The continent covers an area of ~14.0 million km2 (5.4 million sq. mi). It is the fifth
largest continent in area after Asia, Africa, North America, and South America. For the sake
of comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is
covered by ice that averages at least 1 mile (1.6 km) in thickness.
Climate: Antarctica is considered a desert since the annual precipitation is only 200 mm (8
inches) along the coast and far less inland.
Temperature: Lowest recorded on earth -89.2°C/-128.6°F
Average summer temperature at South Pole -27.5°C/-17.5°F
Average winter temperature at South Pole -60°C/-76°F
Mawson station is the windiest place on earth
Average wind speed 37 kmph/23 mph
Maximum recorded gust: 248.4 kmph/154 mph
Population: There are no permanent human residents, but anywhere from 1,000 to 5,000
people reside throughout the year at the research stations scattered across the continent.
Flora and Fauna: Only cold-adapted organisms survive there, including many types of
algae, animals (for e.g., penguins, seals, skuas), bacteria, fungi, plants and protista.
The Polar Regions are pivotal components of the Earth’s system. Ice, rocks and living
material contain a wealth of information on the Earth’s history and the evolution of life.
Major changes in Earth’s climate system can occur in a matter of decades. The Earth’s
climate is essentially a dynamic, heat-driven, multi-component and coupled system.
Antarctica plays a very important role in global climate variability and change, especially in
the Southern Hemisphere. Being remote, isolated and frozen all year makes Antarctica one
of the world’s pristine places to do scientific research.
Although a few nations, including Australia, Argentina, and the United Kingdom, have tried
to lay claim to it over the years, it remains free of government and ownership. In 1959, the
Antarctic Treaty was drafted, and signed by 12 countries designating the land as “a natural
reserve, devoted to peace and science”; to date, 49 countries have signed the treaty.
The treaty prohibits military activities and mineral mining, prohibits nuclear explosions and
nuclear waste disposal, supports scientific research, and protects the continent's eco-zone.
On-going experiments are conducted by more than 4,000 scientists from many nations.
1.3. National Centre for Antarctic and Ocean Research, Goa, India
The National Centre for Antarctic and Ocean Research (NCAOR) is an Indian research and
development institution, and an autonomous Institution of the Ministry of Earth Sciences
4
(MoES), Government of India. NCAOR was established on 25 May 1998 as a nodal agency
for promoting and organizing the Antarctic expeditions launched from the country. The
organization’s main aim is to “plan, promote, co-ordinate and execute the entire gamut of
polar science and logistic activities of the country” in order to ensure a perceptible and
influential presence of India in Antarctica and to uphold our strategic interests in the global
framework of nation in the southern continents and the surrounding oceans. Some of the
responsibilities of NCAOR include:
Management of expeditions and scientific programs,
Coordination of expeditions to the Arctic, Antarctic and Southern Ocean
Management and logistics of the stations
Oceanographic surveys and services
Management of ocean research vessel Sagar Kanya
Bathymetric surveys related to the Exclusive Economic Zone (EEZ)
Surveys related to the legal continental shelf and marine geosciences programme
Develop a complete database (National Antarctic Data Centre)
Laboratory Facilities at NCAOR (For Snow and Ice Core Studies):
Ice Core Laboratory: NCAOR is home to the first polar laboratory of India established in
2005 which is a special low-temperature laboratory complex for the archival and processing
of ice core samples, not only from Antarctica but also from the Arctic and the Himalayas.
Class-100 Clean Room: A clean room has a controlled level of contamination i.e. the
concentration of airborne particles is controlled to specific limits. A class 100 clean room is
designed to have no more than 100 particles (0.5 microns or larger) per cubic foot of air. An
airflow in which essentially the entire body of air within a confined area moves with uniform
velocity along parallel flow lines is achieved and maintained here which is known as laminar
flow. The entrance to the clean room is through an air shower which is a specialized
antechamber to blow off dust particles from clean room personnel before their entry to
reduce the risk of contamination. The Ion Chromatography and Beckman Coulter Counter
(Multisizer 4) instruments are placed in this room so as to achieve accurate results while
measuring ions and dust concentration. The clean room personnel wear special clean room
clothing to prevent contamination.
5
Stable Isotope Ratio Mass Spectrometry (SIRMS): It is an instrument which separates
charged molecules by mass and has been specifically designed to measure the proportions of
particular isotopes. Stable isotope measurements of light elements (e.g. H, C, and O) are
made with a gas source. By comparing the detected isotopic ratios to a measured standard,
an accurate determination of the isotopic make up of the sample is obtained. For example,
carbon isotope ratios are measured relative to the international standard for CO2.
Ion Chromatography (IC): The ion chromatographic analysis is carried out in a Class 100
clean room to measure the concentration of soluble anions (SO42-, Cl-, NO3- etc.) and cations
(Na+, K+, Ca2+, Mg2+, NH4+ etc.) in the melted snow and ice samples.
Coulter Particle Counter (Multisizer 4): This instrument provides size distribution in
number, volume and surface area of micro-particles in snow and ice with an overall sizing
range of 0.4 µm to 1600 µm. It is mainly used for quantitative estimation of dust
concentration from polar ice core samples.
1.4. India in Antarctica
On realizing the strategic, geo-politic, economic, conservation, management, scientific
importance of Antarctica and exploitation of living and mineral resources in the Southern
Ocean, India entered into the realm of polar science in 1981 with the launch of the 1st
Scientific Expedition to Antarctica. So far, 31 expeditions have been successfully launched to
the icy continent on an annual basis.
Indian Antarctic Program:
The Indian Antarctic Program is a multi-disciplinary, multi-institutional scientific activity
under the coordination of NCAOR. The program gained global acceptance with India’s
signing of the Antarctic Treaty and the subsequent establishment of Dakshin Gangotri
Antarctic research base in 1983.
Indian Stations in the Antarctic:
Dakshin Gangotri: It was the first scientific base station of India situated in Antarctica. It
was established during the third Indian expedition to Antarctica in 1983-84. This was the
first time an Indian team spent a winter in Antarctica to carry out scientific work. Later on,
another permanent station, Maitri, was established in 1989.
6
7
8
Maitri: It is India's second permanent research station in Antarctica. It was built and
finished in 1989, shortly before the first station Dakshin Gangotri was buried in ice and
abandoned in 1990–91. Maitri is situated on the rocky, ice free region called Schirmacher
Oasis.
Bharati: It is the latest Antarctic research station commissioned by India during the year
2012. It is India's third Antarctic research facility and one of two active Indian research
stations, alongside Maitri. India is now one of nine nations having multiple stations within
the Antarctic Circle. Bharati's research mandate will focus on oceanographic studies and the
phenomenon of continental breakup. It will also attempt to refine the current
understanding of the Indian subcontinent's geological history.
1.5. A Background on Snow Core Studies
In order to predict the future changes in Earth’s climate, it is necessary to understand the
processes that control climate. Climate proxies help improve our understanding of past
vagaries and possible future climate change. Examples of proxies include ice cores, tree
rings, sub-fossil pollen, boreholes, corals, and lake and ocean sediments. The character of
deposition or rate of growth of the proxies' material is influenced by the climatic conditions
of the time in which they were laid down or grew. Chemical traces produced by climatic
changes, such as quantities of particular isotopes, can be recovered from proxies. Some
proxies, such as gas bubbles trapped in ice, enable traces of the ancient atmosphere to be
recovered and measured directly to provide a history of fluctuations in the composition of
the Earth's atmosphere. To produce the most precise results, systematic cross-verification
between proxy indicators is necessary for accuracy in readings and record-keeping. Proxies
can be combined to produce temperature reconstructions longer than the instrumental
temperature record and can inform discussions of global warming. (Encyclopaedia of
Quarternary Science, 2007)
Snow studies from polar and high elevation regions provide a unique and valuable archive
of the past atmospheric conditions, in large part because of the numerous physical and
chemical measurements that can be performed at any given depth. A sample of either
freshly fallen snow or the combined old and new snow on the ground obtained by pushing a
cylinder down through the snow layer and extracting it is known as a snow core. We study
snow cores because they provide us with high resolution data i.e. dust concentration,
chemical composition of the snow etc. can be easily obtained for a year. Also, chances of
9
contaminating a snow core is less as compared to an ice core as no fluid filled drill is used
for the extraction of a snow core.
Dust as a Proxy:
Dust consists of particles in the atmosphere that comes from various sources such as soil
dust lifted by wind (an aeolian process), volcanic eruptions, and pollution (Alley, 1993). Dust
grain size is a proxy for wind strength that entrains it (Guangjin, 2005). Geologists reveal the
transport and sediment characteristics using dust particle size and distribution (Steffenson,
1997). Dust particle size and distribution are used to interpret the wind strength and dust
storms in the source areas (Delmonte, 2004). Dust records from snow cores have been
widely used to infer past changes in atmospheric circulation and climatic conditions in the
dust source region.
Measurement of the suite of major ions (Na+, Mg2+, Ca2+, K+, NH4+ and SO42-) represents
approximately 95% of the soluble composition of the atmosphere, and therefore provides a
powerful tool for investigating modern and past challenges in atmospheric chemistry. The
non-sea salt fraction (a fraction derived from sources other than the sea) of several species
in the atmosphere is either wholly (in case of Ca2+, Mg2+, Na+) or partially (in case of K+,
SO42-, NO3-, Cl-) the result of soluble evaporate (e.g. Carbonates, Gypsum) minerals derived
from terrestrial deposits. Snow samples therefore collected from sites located close to arid
regions have correspondingly high dust load. Ice-free regions such as dry valleys of
Antarctica are a source of particulate material. (Encyclopaedia of Quarternary Science, 2007)
Impurities scavenged from the atmosphere by falling snow and deposited directly by
gravitational settling comprise a highly detailed record of past changes in climate and
anthropogenic impacts-including atmospheric composition (Allison, 1998), oceanic and
atmospheric circulation , meteorology , explosive volcanism , marine and terrestrial
biosphere emissions , biomass burning, and industrial pollution. The challenge is for Earth
scientists to strategically sample and analyse the unique glaciochemical archive as well as
comprehensively interpret the history contained herein.
Natural sources of aerosols include sea spray, volcanic emissions, forest and grassland fires,
mineral dust, and biogenic emissions. Micro-particles in glacier ice are both soluble and
insoluble, with most being soluble. Soluble micro-particles include sea salts, sulphate
aerosols from volcanic and marine biogenic emissions, and some terrestrial dusts such as
carbonates from evaporate deposits. Insoluble micro-particles are composed of crustal
10
materials including alumina-silicate rock dust, with lesser amounts from volcanic shards
and extra-terrestrial material.
Aerosols are an important part of the Earth system, influencing critical environmental
processes such as biogeochemical cycling and climate forcing. Since aerosols also affect the
Earth’s radiation balance (IPCC 2001, Menon 2002 and Tegen 1996), investigating how
aerosol characteristics and concentrations vary in the atmosphere today and how they might
have varied in the past is crucial to understanding the Earth system and how it will evolve in
the future. As with modern studies of airborne aerosols (Rahn and Lowenthal, 1985), rock
type and chemical composition of insoluble micro-particles found in different layers of ice
within a glacier provide important information on the origin of these micro-particles.
In the present study dust concentration and flux have been quantified and discussed in
terms of spatial variation, seasonal variation and possible sources along Princess Elizabeth
Land and central Dronning Maud Land transects.
11
12
13
2. SAMPLING AND METHODOLOGY
The study area is located in two distinct geographic regimes of Antarctica – the Princess
Elizabeth Land (PEL) sector, facing the Indian Ocean and the central Dronning Maud Land
(DML), facing the Atlantic Ocean. PEL sector of Antarctica is located between 64°56' S and
90°00' S and between 73°35' E and 87°43' E. It is bounded on the west by Amery Ice Shelf and
Mac. Robertson Land; on the east by Wilhelm II Land and Indian Ocean on the south.
Major international research stations present in this area are Davis, Mawson (Australia),
Progress and Mirnyi (Russia), Zhongshan (China) and Bharati (India). DML region is
located between 20° W and 45° E. It extends from the boundary with Coats Land in the west
and Enderby Land in the east. The DML region consists of an ice shelf (an ice shelf is a thick
floating platform of ice that forms where an ice sheet flows down the coastline and onto the
ocean surface) called Nivlisen ice shelf, which covers the ocean surface for about 90 km from
the coastline. Unlike in DML, the PEL coastline does not have an ice shelf that protrudes
several km into the ocean. Another important feature of the DML is the presence of a
continuous mountain chain (Wohlthat Mountains) parallel and about 70 km from the
coastline. These differences, along with many other seasonal features like the sea-ice extent,
biological activity in the ocean, atmospheric circulation pattern and the proximity of these
landmasses with the other continents in terms of chances of long range transport influences
the chemistry and particle flux in Antarctic snow.
In order to understand the snow chemistry variations both spatially and seasonally,
sampling along transects from coast to inland were carried out both in DML and PEL
during the 28th Indian Scientific Expedition to Antarctica. Prior to the field sampling,
adequate planning was made to carry out sampling along transects perpendicular to the
elevation contours from coast to inland in order to study the effect of rapid elevation
changes and distance from the sea on snow chemistry. Sampling for DML was carried out in
such a way that the cores were collected from the lee side, along the pass and the stoss side
of the Wohlthat mountain ranges to study its influence on the micro-particle load and ionic
chemistry in snow.
a. Snow Core Sampling
For the PEL transect, the sampling site began at 10 km from the coast from where a series of
one-meter snow cores were collected at 10 km intervals up to 180 km inland with the
helicopter support (Refer to Study Area where C stands for core and the blue circles depict
the cores that were analysed for the present study). Snow coring was carried out using a
14
KOVACS Mark IV device with a 14 cm diameter barrel. This method allowed a faster way of
sampling at a higher resolution along the transect. Precautionary measures such as the use
of sterile, long-hand, powder-free rubber gloves, polyethylene gloves and face masks were
adapted in order to avoid contamination of the snow samples. Also, to avoid contamination
due to movement of the transect team, sampling was always carried out ∼50 m upwind from
the landing site (of helicopter) at each location. In PEL, twenty-two snow cores were
collected along the transect covering an elevation of up to 2200 m. In the coastal section, i.e.
between 20 km and 50 km, cores were collected at shorter intervals for the assessment of the
spatial variability due to the presence of rapid changes in elevation. Twenty snow cores were
collected in the DML transect beginning at ~20 km from the coastline (i.e., effectively 120
km from the open ocean) due to the Nivlisen Ice Shelf (Refer to Study Area).
The cores were directly transferred from the core barrel into clean custom made HDPE
(High Density Polyethylene) bags, and sealed immediately. The well compacted snow (due
to the wind action in the area) and the shifting of samples in EPP (Expanded Poly
Propylene) boxes with the helicopter support avoided damages to the snow cores. . The
samples were shipped using −20°C reefer containers and stored at −20°C archival facility at
the National Centre for Antarctic and Ocean Research (Goa, India) (Mahalinganathan et al.,
2012).
b. Methodology: Processing of Snow Cores and Particle Analyses:
The snow cores were sub-sampled at 5 cm resolution under a laminar-flow bench, housed in
the -15°C processing facility. The sub-sampling equipment and sample containers were pre-
cleaned by rinsing several times with Milli-Q water (18 MΩ), soaked for at least 24 hours,
followed by rinsing with fresh Milli-Q water and drying in a laminar-flow bench. Samples
were melted immediately prior to the analysis in a class 100 clean room facility.
2.2.1. Beckman Coulter Counter Multisizer 4 (MS 4):
Introduced in the mid-1950s, the Coulter principle became the foundation of an industry
responding to the need for automated cell-counting instruments. The simple idea of passing
cells through a sensing aperture was developed by Wallace H. Coulter and Joseph R.
Coulter. But their idea was dismissed with the remark “You can’t patent a hole”. Today, the
Coulter principle finds applications in the fields of biomedical, biotechnology, cell biology,
crystals, marine biology, microspheres, and air and water contamination.
15
The Coulter Counter provides size distributions in number, volume and surface area in one
measurement, with an overall sizing range from 0.4 µm to 1600 µm. Its response is
unaffected by particle, colour, shape, composition or refractive index.
16
17
18
Principle of a Coulter Particle Counter:
The particles (sample) are suspended in a weak electrolyte solution which is then drawn
through a small aperture. This produces a change in impedance (a measure of the
opposition to time-varying electric current in an electric circuit) that is proportional to the
volume of the particle traversing the orifice. This pulse in impedance originates from the
displacement of electrolyte caused by the particle. Thus the particle volume is measured as
it is proportional to the pulse intensity.
Experimental Considerations:
Coincidence: Anomalous electrical pulses can be generated if the concentration of sample is
so high that multiple particles enter the aperture simultaneously. This situation is known as
coincidence. In order to prevent this situation, samples must be fairly dilute.
Particle Path: The shape of the generated electrical pulse varies with the particle path
through the aperture. Artefacts can occur because the electric field density varies across the
diameter of the aperture. Thus, a particle’s path through the field will impact the shape of
the electric pulse generated. Here, in the aperture format, signal processing algorithms are
used to correct for artefacts resulting from particle path.
Calibration of the Instrument:
Beckman Coulter Counter (MS 4) was calibrated with 50 µm and 100 µm aperture tubes by
using standards L5 (5 µm) and L10 (10 µm) beads. For the present study, a 100 µm aperture
tube (sizing range from 2 µm to 60 µm) was used to analyse the snow cores.
The aperture of the instrument is calibrated with a particle standard that is 10% to 20% of
the aperture size (20%) is preferred. As the aperture tube selected had an aperture size of
100 µm, a particle standard of 10 µm was used. The standard (L10) consists of polystyrene
latex beads of 10 µm modal diameter. A calibration constant (Kd) of 122 was obtained which
was well within the range of ± 4%. The Kd takes into account many factors associated with
the instrument and the aperture tube, including fluid flow characteristics, electrical
resistance with the electrolyte, and imperfections of the orifice such as chip damage or wear.
The calibration was also verified and the measured particle size obtained was within 3% of
the actual calibrator size (10.66 µm).
19
Statistical Determination of Accuracy and Precision: Particle number, volume and mean
diameter were repeatedly analysed using the necessary aperture tubes. The samples
analysed were:
5 µm (L5) and 10 µm (L10) Standards
BCI II Isoton
Ultrapure water
The analytical error obtained during the analysis was better than 5%.
2.2.2. Particle Analyses of Snow Cores
12 out of the retrieved 22 cores from the PEL transect and 7 out of the retrieved 20 cores
from the DML transect were analysed for particle mass concentration using Multisizer 4.
The vials, accuvettes, tips, Isoton solution and ultrapure water used for the analysis of the
samples were analyzed for particles and subtracted as “blank” accordingly during the
analysis of the snow core samples.
Particle Sizing - Analyses Procedure in Snow Cores
The snow core samples were analysed by adding 5 ml of the sample and 5 ml of Isoton (an
electrolyte) to an accuvette. The precautions taken so as to avoid contaminating the sample
included the use of plastic gloves, autoclaved tips and rinsing of the accuvette as well as the
tips with the sample. The instrument was then switched on and the number as well as
volume of dust particles was thus measured in the range of 2 µm to 60 µm diameter (2% to
60% of the aperture diameter). Particle mass concentration, in ppb, was calculated from the
volume assuming a mean particle density of 2.6 g/cm3 (Sugimae, 1984).
2.2.3. Calculations:
Particle Mass Concentration:
The equation used for the calculation of particle mass concentration (Sugimae, 1984):
Particle Mass (µgl-1) = 2.6 (Mean Particle Density) x Volume of Particle x 10-3
(in gml-1) (in µm3ml-1)
20
Non Sea-Salt Calculation:
Non sea-salt (nss) ions were calculated using the following equation:
nss Xsnow = Xsnow - { (X/Na) x (Na)snow}
where, X = Concentration of ion in ppb
Na in snow is not known to undergo any post depositional changes making it a conservative
species and is therefore used as a reference for seawater.
Dust Flux Calculation:
The dust flux (addition or removal of dust annually) was calculated using the following
equation:
Dust Flux (kg/km2/a) = Particle Mass Concentration x Annual Snow Accumulation Rate
(in gcm-3) (in cma-1)
21
3. RESULTS
The coastal section (between 20 km and 50 km) of PEL showed an average particle mass
concentration of 174 µgl-1 with a maximum of 1277 µgl-1 at 40 km from the coast and a
minimum of 31 µgl-1, 30 km from the coast. The particle size ranged between 2 µm and 4 µm.
The average dust flux was 126 kg.km-2.a-1 in this region, with a maximum flux of 207 kg.km-
2.a-1 at 40 km and a minimum of 74 kg.km-2.a-1 at 26 km from the coast. On the other hand,
the inland region of PEL (between 80 km and 180 km) showed an average particle mass
concentration of 141 µgl-1, with a maximum of 1881 µgl-1 at 120 km from the coast and a
minimum of 19 µgl-1 at 180 km from the coast. The particle size ranged between 2 µm and 3
µm. The dust flux in the inland section of the transect showed an average of 88 kg.km-2.a-1
with a maximum of 129 kg.km-2.a-1 at 120 km from the coast and a minimum of 54 kg.km-2.a-1
at 180 km from the coast. The seasonal dust flux showed a higher average during summer
than winter in PEL (Table 1)
The region towards the coast in DML (between 120 and 170 km from the sea) showed an
average particle mass concentration of 140 µgl-1 with a maximum of 445 µgl-1 and a
minimum of 31 µgl-1 at 120 km from the sea. The particle size ranged between 2 µm and 4
µm. The average dust flux was 110 kg.km-2.a-1 with a maximum of 116 kg.km-2.a-1 at 120 km
and a minimum of 104 kg.km-2.a-1 at 150 km. The inland region of DML showed an average
particle mass concentration of 120 µgl-1 with a maximum of 648 µgl-1 at 300 km and a
minimum of 16 µgl-1 at 270 km. The particle size ranged between 2 µm and 3 µm. The
average dust flux was 45 kg.km-2.a-1 with a maximum of 58 kg.km-2.a-1 at 300 km from the
coast and a minimum of 31 kg.km-2.a-1 at 270 km from the coast.
22
4. DISCUSSION AND CONCLUSION
Dust Distribution in Princess Elizabeth Land:
The coastal section (between 20 km and 50 km) of PEL showed an average particle mass
concentration of 174 µgl-1 and the inland region (between 80 km and 180 km) showed an
average of 141 µgl-1. The box plot (Fig. 25) shows the spatial distribution of dust mass
concentration along with the statistics. The maximum number of particles ranged between 2
µm and 4 µm in the coastal section, whereas in inland, the particle size ranged between 2 µm
and 3 µm. Overall, the particle size did not exceed the range above 8 µm – 10 µm. The
number of particles above 10 µm size range were very minimal (generally below 5 particles).
This could be due to the absence of exposed mountain areas in the region (Xiao, 2010). The
finer size range explains that dust could be sourced far away in the ocean or via the long
range transport of finer particles from other continents (Boutron,1994). The dust mass
concentration did not show any significant correlation with the major ions throughout the
transect. However, the dust mass concentration showed a significant correlation with
nssSO42- at 20 km (0.52 at 95% confidence level) and 30 km (0.55 at 95% confidence level).
This correlation could be attributed to the biogenic emissions of planktonic organisms
which release atmospheric sulphate through the conversion of dimethyl sulphide (DMS). An
interesting correlation between dust mass concentration and nssK+ (0.96 at 99% confidence
level) was observed only at 120 km from the coast. K+ ions normally have a sea-salt source,
however the strong correlation with a nss-source at this location indicates a possible crustal
source or more likely the result of sample contamination (during handling of samples). The
dust flux was the highest in the coastal section of PEL between 40 km and 50 km (>150
kg.km-2.a-1) (Fig. 26). However, the lowest dust flux in the coastal section was observed
between 20 km and 30 km (97 kg.km-2.a-1 and 76 kg.km-2.a-1 at 23 km and 26 km
respectively). This could be attributed to the combined effect of wind circulation pattern and
the steep topography (Mahalinganathan et al., 2012) on the dust distribution and
deposition. The dust flux values decreased inland with 106 kg.km-2.a-1 at 50 km and 92
kg.km-2.a-1 at 80 km from the coast before slightly increasing t0 129 kg.km-2.a-1 at 120 km. It
is at 120 km where the dust concentration showed a very strong correlation with that of the
nssK+ concentration in snow as noted before.
23
Table 1: Table showing total dust flux along the PEL and DML transects
Table 2: Table showing seasonal dust flux along the PEL and DML transects
PEL Dust flux (kg/km2/yr)
DML Dust flux (kg/km2/yr)
Location
Summer
Winter
Location
Summer
Winter
2
91
49
2
83
33
2b
48
48
5
74
30
2c
44
32
8
69
104
3
94
53
11
57
59
3a
78
9
17
20
11
4
103
104
20
36
22
4a
96
53
5
74
32
8
72
19
12
119
9
15
31
47
18
42
12
PEL Dust Flux (kg/m2/yr)
DML Dust Flux (kg/m2/yr)
Location
Flux
Flux
Location
2
140
116
2
2b
97
104
5
2c
76
173
8
3
147
116
11
3a
87
31
17
4
207
58
20
4a
149
5
106
8
92
12
129
15
78
18
54
24
Table 3: Table showing correlation between dust flux and ionic flux along PEL
Table 4: Table showing correlation between dust flux and ionic flux along DML
SO42-
Na+
NH4+
K+
Ca2+
Mg2+
Dust
SO42-
1.00
Na+
0.44
1.00
NH4+
-0.58
0.05
1.00
K+
0.41
0.91
0.31
1.00
Ca2+
0.85
0.73
-0.60
0.55
1.00
Mg2+
0.46
0.98
-0.09
0.82
0.76
1.00
Dust
0.87*
0.69
-0.58
0.58
0.97**
0.72
1.00
* Correlation is significant at 0.05 level of significance
**Correlation is significant at 0.01 level of significance
SO42-
Na+
NH4+
K+
Ca2+
Mg2+
Dust
SO42-
1
Na+
0.51
1.00
NH4+
0.30
0.87
1.00
K+
0.71
0.93
0.76
1.00
Ca2+
0.60
0.02
-0.10
0.26
1.00
Mg2+
0.94
0.52
0.28
0.72
0.54
1.00
Dust
0.25
-0.09
-0.30
0.10
0.22
0.31
1
25
Fig. 23: Correlation between dust mass and ionic concentration along the PEL
transect
Fig. 24: Correlation between dust mass and ionic concentration along the DML
transect
26
27
The dust flux trend reduced significantly inland ranging below 80 kg.km-2.a-1. The dust flux
did not show any correlation with that of the flux of any of the major ions (that represent
crustal significance), thus suggesting no significant crustal contribution to the dust particles
in the PEL. The summer dust largely contributed to the total dust flux throughout the
transect (Table 2). This suggests that the dust could be from local sources as during
summer, more of ice free areas develop due to melting leading to it becoming a primary
source of dust. The deposition of micro-particles on the PEL could be entirely accomplished
through the process of precipitation. The deposited particles could either be active as nuclei
in the formation of snow or be swept from the atmosphere through falling snow
(Holdsworth, 1996).
Dust Distribution in Dronning Maud Land
The section towards the coast in central DML (between 120 and 170 km from the sea)
showed an average particle mass concentration of 140 µgl-1 which decreased significantly
inland beyond the Wohlthat Mountains (beyond 250 km from the sea) with an average
particle mass concentration of 120 µgl-1. The box plot (Fig. 25) shows the spatial distribution
of dust mass concentration along with the statistics. It is clear from the plot that there is no
particular trend in the distribution of dust mass concentration with the changes in distance
from the coast and elevation. The maximum number of particles ranged between 2 µm and 4
µm in the coastal section, whereas in inland, the particle size ranged between 2 µm and 3
µm. Overall, the particle size did not exceed the range above 8 µm – 10 µm. The number of
particles above 10 µm size range were very minimal (generally below 5 particles). However,
the samples retrieved along the Wohlthat mountain pass (between 180 and 220 km from the
coast) consisted of particles that were not dissolved with a clear indication of the mountain
origin. The dust mass concentration showed significant correlation with the major ions
along the mountain pass and beyond the mountains. Correlation between particle mass
concentration and major soluble ions (Na+, K+, Mg2+, Ca2+, NH4+ and SO42-) yielded
significant correlation values of 0.8 for SO42-, 0.8 for Na+, 0.9 for K+ and 0.7 for Mg2+ at 120
km from the coast. NH4+ showed a significant correlation of 0.6 at 150 km from the coast.
Mid- transect yielded significant correlation values of 0.9 with SO42-, 0.7 with Na+, 0.8 with
NH4+, 0.9 with K+, 0.5 with Mg2+ and 0.9 with Ca2+, all at 180 km from the coast. Correlation
between particle mass concentration and non sea salt ions (Na+, K+, Mg2+, Ca2+, NH4+ and
28
SO42-) yielded significant correlation values of 0.6 ( at 99% confidence interval) with SO42- at
120 km from the coast suggesting the source to be the biogenic emissions of planktonic
organisms which release atmospheric sulphate through the conversion of dimethyl sulphide
(DMS). Mid-transect yielded significant correlation values of 0.9 with SO42-, K+ and Ca2+ at
180 km from the coast suggesting the Wohlthat mountain ranges to be the source.
Particle mass concentration was evenly distributed along both the transects , below 250 µgl-1
with no significant spatial differences in PEL and DML (Fig. 25). The coastal section of PEL
showed higher dust concentration in comparison with DML as PEL showed a maximum
value of 1277 µgl-1 at 40 km from the coast and 445 µgl-1 at 120 km from the coast for DML. A
significant decrease in dust concentration was observed with increasing distance from the
sea and elevation. However, the inland region in DML beyond the Wohlthat mountain
ranges showed an increase in the dust concentration with increasing distance from the sea.
The sources of dust here could be the Larsemann hills and the Vestfold hills (Zielinski,
1997). Correlation between particle mass concentration and major soluble ions (Na+, K+,
Mg2+, Ca2+, NH4+ and SO42-) yielded significant correlation values of 0.5 with Na+ at 270 km
and 0.5 with Ca2+ at 300 km from the coast. The correlation between particle mass
concentration and non sea salt ions (Na+, K+, Mg2+, Ca2+, NH4+ and SO42-) yielded a
significant correlation value of 0.5 with Ca2+ at 300 km from the coast. The source of dust
here could be attributed to continental crust. The summer dust largely contributed to the
total dust flux throughout the transect which was similar to the trend observed in PEL
(Table 2).
The present study using snow cores from Princess Elizabeth Land and Dronning Maud Land
from the coast to inland transect revealed a strong correlation between dust mass
concentration and ionic concentration at 180 km from the coast, PEL and 180 km from the
continental edge, DML. The correlation at these locations suggests that the source of dust in
PEL could be the Larsemann hills and Vestfold hills whereas in DML it could be the
Wohlthat mountains. It is therefore important to look at this correlation as it provides
information on the origin of dust. The amount of influx observed in PEL during summer
and winter was 74 kg/m2/yr and 39 kg/m2/yr whereas in DML it was 57 kg/m2/yr and 43
kg/m2/yr. The higher dust influx in summer suggests the origin of dust to be the ice free
areas which become more exposed due to melting in summer. The information on
seasonality and origin of dust are important parameters in the interpretation of snow and
29
ice cores. Through this information the time period and source of origin of dust can be
established. This could be instrumental in the interpretation of climate processes in the past
which in turn aid in the interpretation of future climatic signals.
30
REFERENCES
1. Alley, R. B., et al. (1993). Abrupt increase in Greenland snow accumulation at the end of the
Younger Dryas event. Nature 362, 527-529
2. Allison, I.: Surface climate of the interior of the Lambert Glacier basin, Antarctica, from
Automatic weather station data, Ann. Glaciol., 27, 515–520, 1998.
3. Boutron, C.F., Candelone, J.-P., and Hong, S. (1994). Past and recent changes in large- scale
tropospheric cycles of lead and other heavy metals as documented in Antarctic and
Greenland snow and ice: A review. Geochemica et Cosmochimica Acta 58(15), 3217-3225
4. Davidson, C.I., Jaffrezo, J.L., and Mayewski, P. A. (1991). Arctic air pollution as reflected in
snowpits and ice cores. In Pollution of the Arctic Atmosphere (W. T. Sturges, Ed.), pp. 43-95.
Elsevier
5. Delmonte, B., Basile-Doelsch, I., Petit, J.-R., et al. (2004). Comparing the Epica and Vostok
dust records during the last 220,000 years: Stratigraphical correlation and provenance in
glacial periods. Earth-Science Reviews 66, 63-87.Derbyshire, E., Kemp, R.A., Meng, X.M.,
Variations in loess and palaeosol properties as indicators of palaeoclimatic gradients across
the Loess Plateau of Northern China, Quaternary Science Reviews, 1995, 14: 681―697.
6. Guangjin WU, et al. (2005) Grain size record of micro-particles in the Muztagata ice core
7. Holdsworth, G., et al. (1996). Historical biomass burning: Late 19th century pioneer
agriculture recolution in northern hemisphere ice core data and its atmospheric
interpretation. Journal of Geophysical Research 101(D18), 23371-123334
8. Legrand, M., Feniet-Saigne, C., Saltzmann, E. S., Germain, C., Barkov, N.I., and Petrov, V.N.
(1991). Ice-core record of oceanic emissions of dimethyl sulphide during the last climate
cycle. Nature 350, 144-146
9. Ma, Y., Bian, L., Xiao, C., Allison, I., and Zhou, X.: Nearsurface climate of the traverse route
from Zhongshan Station to Dome A, East Antarctica, Antarct. ci., 22, 443–459,
doi:10.1017/s0954102010000209, 2010.
10. Mahalinganathan. K, Thamban Meloth, Laluraj C. M., Redkar B.L.: Relation between
surface topography and sea salt snow chemistry from Princess Elizabeth Land, East
Antarctica. The Cryosphere, 6, 505–515.
11. Maring, H., Savoie, D.L., Izaguirre, M. A. et al., Mineral dust aerosol size distribution
change during atmospheric transport, Journal of Geophysical Research, 2003, 108(D19), doi:
10.1029/ 2002JD002536.
12. Mayewski, P., et al. (1993). The atmosphere during the Younger Dryas, Science 261,195-197
31
13. Porter, S.C., An, Z.S., Correlation between climate events in the North Atlantic and China
during the last glaciation, Nature, 1995, 375: 305―308.
14. Robok, A., and Free, M. (1996). The volcanic record in ice cores for the past 2000 years. In
Climatic Variations and Forcing Mechanisms or the Last 2000 Years (P. Jones, R. Bradley
and J. Jouzel, Eds.), pp. 533-546.Springer.
15. Steffensen, J.P., The size distribution of microparticles from selected segments of the
Greenland Ice Core Project ice core representing different climatic periods, Journal of
Geophysical Re-search, 1997, 102(C12): 26755―26763.
16. Sugimae, A., Elemental constituents of atmospheric particulates and particle density,
Nature, 1984, 307: 145―147.
17. Zdanowicz, C.M., Zielinski, G.A., Wake, C.P., characteristics of modern atmospheric dust
deposition in snow on the Penny Ice Cap, Baffin Island, Arctic Canada, Tellus, 1998, 50(B):
506―520.
18. Zielinski, G.A., Mershon, G.R., Paleoenvironmental implications of the insoluble
microparticle record in the GISP2 (Greenland) ice core during the rapidly changing climate
of the Pleistocene- Holocene transition, Geological Society of American Bulletin, 1997,
109(5): 547―559.
Websites and Books
1. https://www.beckmancoulter.com/
2. http://www.andrill.org/about/antarctica
3. http://www.antarctica.gov.au/
4. http://www.usap.gov/
5. http://www.wikipedia.org
6. Google Earth. 1999 71°54΄25.00”S 14°01΄49.33” E, elevation 1971 m. Available through:
<http://www.google.com/earth/index.html>. Accessed 21 July 2012
7. Google Earth. 1999 71°30΄55.47”S 83°03΄17.83” E, elevation 2790 m. Available through:
<http://www.google.com/earth/index.html>. Accessed 21 July 2012
8. Scott A. Elias, 2007, Encyclopaedia of Quarternary Science.
9. Beckman Coulter Counter Manual, 2008
10. NCAOR, 2011. NCAOR Annual Report 2010-2011. Goa
32
ANNEXURE
Tables showing correlation between dust mass and ionic concentration
along PEL transect
PEL 2
Dust
PEL 2B
Dust
PEL 2C
Dust
Cl-
-0.32
Cl-
*-0.65
Cl-
0.22
Na+
-0.29
Na+
-0.11
Na+
0.21
Ca2+
0.05
Ca2+
0.05
Ca2+
0.11
Mg2+
-0.29
Mg2+
-0.32
Mg2+
0.24
SO42-
0.14
SO42-
-0.26
SO42-
0.16
K+
-0.13
K+
0.00
K+
0.24
PEL 3
Dust
PEL
3A
Dust
PEL 4
Dust
Cl-
-0.015
Cl-
-0.23
Cl-
0.056
Na+
-0.016
Na+
-0.20
Na+
0.057
Ca2+
0.183
Ca2+
-0.22
Ca2+
-0.060
Mg2+
0.028
Mg2+
-0.19
Mg2+
0.052
SO42-
0.265
SO42-
0.38
SO42-
-0.115
K+
0.014
K+
-0.16
K+
0.088
PEL
4A
Dust
PEL 5
Dust
PEL 8
Dust
Cl-
0.00
Cl-
0.21
Cl-
0.21
Na+
-0.05
Na+
0.27
NO3-
0.52
Ca2+
-0.05
Ca2+
-0.10
SO42-
0.27
Mg2+
-0.02
Mg2+
0.19
Na+
0.20
SO42-
-0.17
SO42-
0.27
NH4+
0.21
K+
-0.12
K+
0.30
K+
0.28
Ca2+
*0.49
Mg2+
0.21
PEL 12
Dust
PEL 15
Dust
PEL 18
Dust
Cl-
0.43
Cl-
0.19
Cl-
0.51
NO3-
0.43
NO3-
-0.16
NO3-
-0.28
SO42-
0.09
SO42-
-0.18
SO42-
-0.29
Na+
0.13
Na+
0.23
Na+
*0.57
NH4+
-0.14
NH4+
-0.31
NH4+
-0.22
K+
**0.96
K+
-0.13
K+
0.44
Ca2+
0.13
Ca2+
-0.13
Ca2+
-0.21
Mg2+
0.11
Mg2+
-0.04
Mg2+
*0.59
33
Tables showing correlation between dust mass and ionic concentration
along the DML transect
DML 2
Dust
DML 5
Dust
DML 8
Dust
Cl-
**0.79
Cl-
-0.07
Cl-
**0.64
SO42-
**0.76
SO42-
0.14
SO42-
**0.98
NO3-
**0.61
NO3-
-0.02
NO3-
-0.13
Na+
**0.75
Na+
-0.06
Na+
**0.72
NH4+
-0.38
NH4+
0.58
NH4+
**0.75
K+
**0.85
K+
-0.01
K+
**0.98
Mg2+
**0.72
Mg2+
-0.07
Mg2+
0.46
Ca2+
0.01
Ca2+
-0.03
Ca2+
**0.96
DML
11
Dust
DML
14
Dust
DML
17
Dust
Cl-
0.31
Cl-
0.83
Cl-
0.04
SO42-
0.32
SO42-
0.27
SO42-
0.00
NO3-
0.26
NO3-
0.09
NO3-
-0.43
Na+
0.31
Na+
0.47
Na+
0.05
NH4+
0.40
NH4+
-0.35
NH4+
0.05
K+
0.27
K+
0.25
K+
0.01
Mg2+
0.33
Mg2+
0.38
Mg2+
0.03
Ca2+
0.36
Ca2+
0.21
Ca2+
-0.38
DML 20
Dust
Cl-
0.17
SO42-
0.36
NO3-
*0.53
Na+
0.08
NH4+
0.08
K+
-0.02
Mg2+
0.40
Ca2+
*0.53
34
Tables showing correlation between dust mass and non sea salt
concentration along the PEL transect
PEL 2
Dust
PEL 2B
Dust
PEL 2C
Dust
Cl-
-0.35
Cl-
-0.02
Cl-
-0.21
Ca2+
0.26
Ca2+
0.17
Ca2+
-0.15
Mg2+
-0.05
Mg2+
0.06
Mg2+
-0.20
SO42-
*0.52
SO42-
0.02
SO42-
-0.19
K+
0.40
K+
0.20
K+
0.06
PEL 3
Dust
PEL
3A
Dust
PEL 4
Dust
Cl-
0.02
Cl-
0.17
Cl-
-0.04
Ca2+
0.20
Ca2+
-0.20
Ca2+
-0.09
Mg2+
0.16
Mg2+
0.20
Mg2+
-0.08
SO42-
0.55
SO42-
0.29
SO42-
-0.18
K+
0.15
K+
-0.10
K+
0.09
PEL
4A
Dust
PEL 5
Dust
PEL 8
Dust
Cl-
0.07
Cl-
-0.11
Cl-
0.24
Ca2+
-0.03
Ca2+
-0.14
Ca2+
0.13
Mg2+
0.06
Mg2+
-0.36
Mg2+
0.10
SO42-
-0.01
SO42-
0.11
SO42-
0.46
K+
-0.11
K+
0.25
K+
0.24
PEL 12
Dust
PEL 15
Dust
PEL 18
Dust
Cl-
0.57
Cl-
0.22
Cl-
0.28
Ca2+
0.07
Ca2+
-0.19
Ca2+
-0.34
Mg2+
**0.95
Mg2+
-0.30
Mg2+
0.29
SO42-
0.13
SO42-
-0.22
SO42-
-0.22
K+
-0.05
K+
-0.38
K+
0.16
35
Tables showing correlation between dust mass and non sea salt
concentration along the DML transect
DML 2
Dust
DML 5
Dust
DML 8
Dust
Cl-
**0.83
Cl-
-0.09
Cl-
0.04
SO42-
**0.64
SO42-
0.17
SO42-
**0.98
K+
-0.13
K+
0.20
K+
**0.95
Ca2+
-0.21
Ca2+
-0.01
Ca2+
**0.96
Mg2+
0.18
Mg2+
0.07
Mg2+
-0.88
DML
11
Dust
DML
14
Dust
DML
17
Dust
Cl-
-0.27
Cl-
0.16
Cl-
-0.10
SO42-
0.32
SO42-
0.26
SO42-
-0.02
K+
0.09
K+
0.22
K+
-0.01
Ca2+
0.36
Ca2+
0.16
Ca2+
-0.30
Mg2+
-0.35
Mg2+
-0.38
Mg2+
-0.05
DML 20
Dust
Cl-
0.32
SO42-
0.35
K+
-0.05
Ca2+
*0.48
Mg2+
-0.03
*Correlation is significant at 0.05 level of significance
**Correlation is significant at 0.01 level of significance
