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Soil contamination in Fildes Peninsula (King George Island,

Antarctic): Bio(availability) and Remediation strategies.

Ana Padeiro1*, Margarida C. Santos1, João Canário1

1CQE, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

*ana.padeiro@tecnico.ulisboa.pt

Abstract

The Fildes Bay, located on Fildes Peninsula, King George Island, is characterized by its

high biodiversity, but also by the high density of scientific stations, becoming one of the

most contaminated areas of Antarctica. In order to assess the contamination and

distribution of several trace elements (Cr, Ni, Cu, Zn, As, Pb, Cd and Hg) in Fildes Bay,

soil samples were collected, The results obtained in this study point to the existence of

several contaminated hotspots mainly related to high levels of Cu, Zn, Pb, Cd, Cr and Ni.

The comparison of the contaminant distribution pattern with previous works allows

identifying the anthropogenic sources as well as proposing several remediation

strategies.

Keywords: Trace elements, contamination, human impacts, remediation, Fildes Bay, Antarctica

Introduction

In recent decades there has been an

increasing expansion, in intensity and

diversity, of human activities in Antarctica,

especially in its peninsula and surrounding

islands, which has caused serious pollution

problems, mainly near the scientific stations

(Bargagli, 2008). These problems have led

to the implementation of an environmental

protocol, the Madrid Protocol, which

designates Antarctica as a “natural reserve,

devoted to peace and science” (Art.

2). Article 3 of the Environment Protocol

sets four basic principles applicable to

human activities in Antarctica to avoid or

limit negative impacts on the environment

and ecosystems and Article 7 prohibits all

activities relating to Antarctic mineral

resources, except for scientific research

(Secretariat of the Antarctic Treaty, 2011).

Humans have occupied the Fildes Bay area

for over fifty years and in the past ten years

the average number of people living and

working in stations increased about 26%

during the summer (251 to 316) and 33% in

winter (95 to 126). It is possible to assume

that this growth in the number of occupants

of the stations will lead to a potential

increase risk for the environment (Peter, et

al., 2013). Recent studies reveal that in

some areas, near the scientific stations, the

concentrations of several trace elements

are increasing, affecting the surrounding

ecosystem (Artaxo & Rabello, 1992; Negri,

2006; Santos, et al., 2005). Bargagli (2005)

and Peter et al. (2008) state that the Fildes

region is directly influenced – although with

limits – by the current management of

waste stations, oil handling, ships and

tourism yachts in KGI and also by airborne

contaminants from South America.

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Although there are some studies which the

concentrations of trace elements in the

Fildes Peninsula were determined, this is

the first study that provides an insight of the

source, distribution and bio(availability) of

trace elements (Cr, Ni, Cu, Zn, As, Pb, Cd

and Hg) on soil in Fildes Bay. No studies to

date have examined the availability of trace

elements in Fildes soils. Such data can help

to predict the degree of vulnerability of

Fildes soil in response to the growing

human occupation. The vulnerability of the

environment is directly proportional to the

capacity of a soil for retaining pollutants.

The environmental risks are as high as the

availability of the trace elements, which

leads to leaching and groundwater

contamination (Mendonça, et al., 2013).

Material and Methods

Site description

The Fildes Bay also known as Maxwell Bay,

located in Fildes Peninsula (62º 08´ S - 62º

14´S, 59º 02´ W - 58º 51´W) is located in

the southwest of the Island of King George

(KGI), South Shetland Island (Fig.1), and

represents one of the largest ice-free areas

in the maritime Antarctic region and it is

characterized by its high biodiversity (Peter,

et al., 2013). Collins Glacier was used as

reference site because there are no human

pressures in this site.

Figure 1- Fildes Peninsula location and map showing the sampling sites.

Sampling and Analytical methods

During the summer of 2014, surface soil

samples (the top 10 cm) were collected

around Fildes Bay (Fig.1). Sampling was

carried out with ultra-clean protocol

techniques, using acid decontaminated

material and wearing latex gloves. Samples

were collected with a decontaminated

plastic spatula, stored in zip sealed plastic

bags and also dried at 40°C. After dried,

sediments where sieved and only the

fraction <2 mm was used for analysis, to

avoid the dilution of contents by coarse

material.

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Digestion of the samples was carried out to

destroy organic matter and to dissolve

suspended solids. Samples were digested

in Aqua Regia (HCl, 36 %; HNO3, 60 %,

3:1) and HF (40 %) in Teflon bombs (100

ºC for 1 h) (Loring and Rantala, 1992),

evaporated to near dryness and dissolved

with HNO3 (1 %).

Tests of bioavailability were conducted with

Immobilised Phaeodactylum tricornutum in

alginate. Immobilised P.tricornutum was

incubated, with water and soil collected at

Fildes bay, in polyethylene devices. Control

and test incubation devices were produced

according to Cabrita et al. (2013); a control

device comprised a zip-lock transparent

polyethylene bag filled with Immobilised P.

tricornutum with f/2, preventing contact with

Fildes Bay water or water and soil, whereas

a test one consisted of a drilled zip-lock

transparent polyethylene bag filled with

Immobilised P. tricornutum, that allowed the

contact with Fildes Bay water or water and

soil. At each experiment day, both control

and test incubation devices were always

used.

Leaching simulation tests were performed

for the partitioning of particulate trace

elements into the exchangeable fractions

using H2O Millipore, shaking for 6 h.

Analyses of trace elements (Cr, Ni, Cu, Zn,

As, Pb and Cd) in all samples were done by

ICP–MS. Hg determination in soil samples

were done by atomic absorption using a

direct mercury analyzer

QA/QC Control: International certified

standards (MESS-3, TH2 and 414-

Plancton) were used to ensure the

accuracy of our procedure. For all

parameters, obtained values were

consistent within the ranges of certified

values. Analytical variability and

homogeneity of soils samples (calculated

as standard deviation of duplicates, with

values below 15%) were considered

satisfactory.

Results and discussion

Trace elements content

The ranges of values measured for the 8

elements in Fildes Bay and Collins Glacier

are shown in Table 1. The element content

(μg g-1; Hg mg g-1) in Fildes Bay were 15-

263 Cr, 12-141 Ni, 56-179 Cu, 68-949 Zn,

13-23 As, 3-418 Pb, 0,2-1,2 Cd and 0,005-

0,37 Hg. These concentrations are higher

than the values found for the Collins Glacier

(reference site - without anthropogenic

impacts), 28-31 Cr, 12-18 Ni, 49-70 Cu, 56-

87 Zn, 12-18 As, 5-7 Pb, 0,2 Cd and 0,006

Hg.

Table 1- Ranges of element concentration (μg g-1; Hg mg g-1) in Fildes Bay soil samples.

Local Cr Ni Cu Zn As Pb Cd Hg

Fildes Bay 15-263 12-141 56-179 68-949 13-23 3-418 0,2-1,2 0-0,37

Collins Glaciar 28-31 12-18 49-70 56-87 12-18 5-7 0,2 0,006

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Trace elements distribution

Figure 2 – Element distribution (μg g-1; Hg mg g-1) in Fildes Bay and the representation (through the hoop) of the average concentration of each element in the reference soil (glacial Collins).

With the observation of Fig. 2 it is possible

to see that samples of Fildes Bay have

higher values than those found in Collins

Glacier. The concentrations of As and Hg

are those with lower amplitude across the

Bay. Therefore, except for sample 14

relative to the mercury which has a 21

times higher concentration than the others,

it is expected that levels of these elements

are mostly of geologic origin. The

distribution of the remaining elements

follows the distribution of waste sites

(without protection for the ecosystems) that

exist in the Bay, as well as locations

affected by oil substances in the case of Pb

and Cd, in particular in areas with fuel

storage tanks. The distribution of Ni and Cr

shows a significant correlation (rs = 0.92, P

<0.05), as well as Pb and Cd (rs = 0.81, P

<0.05), which indicates the same source of

contamination for the correlated elements.

Fig. 3 allows a better understanding of that,

since it allows the comparison of sampling

sites with local waste disposal and spill or

fuel storage.

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Figure 3 - Distribution of waste disposal and fuel storage and/ or spills in Fildes Bay (Adapted from Peter, et al. 2013).

Leaching simulation

The percentages of the element extracted

by water were calculated by:

%𝑀𝐸 =[𝑀]𝑒𝑥𝑡𝑟𝑎𝑐𝑡𝑒𝑑 × 𝑉

[𝑀]𝑇𝑜𝑡𝑎𝑙 × 𝑚𝑆𝑜𝑖𝑙 × 100

Where [M]extracted is the concentration of

element extracted from the soil (µg L-1); V

the volume of milipore water (L); [M]Total is

the

concentration of element in the soil (g);

Msolo is the mass of soil used is the

experiment.

The main objective of this test was to

simulate the leaching/runoff caused by

rainfall and glacier melt in Fildes Bay. From

Table 2 it can be seen that only a tiny

fraction of total elements that are found in

soils is extractable.

Table 2 – Percentage range of element removal by Millipore H2O (contact for 6h with stirring)

Cr Ni Cu Zn As Pb Cd

0,02-0,09 0,02-0,19 0,05-0,38 0,04-1,04 0,16-0,86 0-0,04 0,5-2,01

Trace elements bioavailability

Figure 4 shows the mean and standard

deviation of the concentration of Cr, Ni, Cu,

Zn, Cd and Pb in P. tricornutum cells in the

water and soil from study site, as well as

the controls.

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Figure 4 -Incorporation of trace element in cells of P. tricomutum during testing of bioavailability. Incubation: a) Collins water + C2 Soil; b) Fildes water + 27 Soil; c) Fildes water + 35; d) Fildes water + 75 soil.

With the exception of Pb in microalgae

incubated with soil 35, the accumulation of

Cr, Ni, Cu, Zn, As, Cd, and Pb in the

immobilised P. tricornutum cells exposed is

significantly (p<0.05) higher than the

concentration in control cells.

In order to assess the amount of element

incorporated into the cell was calculated the

% of Element removal by,

%𝑅𝑀𝐴 =𝑀𝐸𝐴𝑙𝑔𝑎𝑒 × 𝑚𝑎𝑙𝑔𝑎𝑒

𝑀𝐸𝑆𝑜𝑖𝑙 × 𝑚𝑆𝑜𝑖𝑙

where ME is the element concentration (µg

g-1) and m the mass (g)

All elements have bioavailable fractions,

although, as expected, with different levels

of incorporation by the cells. The Zn was

the element that showed a greater

incorporation by the algae in all soils, with a

maximum of 25%. The maximum

percentage removal achieved for Zn and Pb

is much higher than other elements,

suggesting the possibility of anthropogenic

contribution.

Table 3 – Percentage range of element removal by microalgae.

Cr Ni Cu Zn As Pb Cd

1,4-4,3 1,8-3,2 1,1-3,5 3,9-25 0,8-1,2 2,7-24 1,7-5,3

Conclusion

The concentration and distribution of the

trace elements analyzed in the soil samples

of Fildes Bay clearly evidence the negative

impact of human presence. A significant

correlation was found between the

concentrations of Cr and Ni, where high

concentrations were found near the waste

disposal sites. A significant correlation was

also found between Pb and Cd

concentrations, where higher

concentrations were found in samples near

the fuel tanks. The distribution of Zn seems

to be related to both, fuel tanks and waste

disposal.

The simulation of leaching and the

bioavailability tests indicate that the

elements in soils are mainly in the

particulate fraction, and therefore transport

by the suspended particles. Once the

particles reach the bay deadsorption takes

place (owing to the high ionic strength and

complexing capacity of the salt water) thus

increasing the concentration of the

7

elements. By the bioavailability tests it was

concluded also that, except for As and Hg,

all elements are biologically available. We

concluded that it is urgent that measures for

soil rehabilitation are taken in Fildes Bay,

especially with respect to contamination by

Cr, Ni, Pb, Cd, Cu and Zn. Thought further

research is needed in order to fully access

the contamination a brief research allowed

to suggest that the remediation measures

that may be more adequate in the area are

the chemical fixation (using

orthophosphates) and the permeable

reactive barrier.

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Obtido em 6 de Abril de 2014, de

ats: http://www.ats.aq/e/ep.htm