arsenic contamination in soils, water and plants

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Arsenic contamination in soils, water and plants
surrounding gold mine in Thailand

Thares Srisatit
1
, Wanpen Wirojanagud
2
, Thanes Weerasiri
3


1 Faculty of Environmental Engineering, Chulalongkorn University, Thailand
2 Faculty of Environmental Engineering, Khonkaen University, Thailand
3 Faculty of Science and Technology, Thammasat University, Thailand


ABSTRACT

Arsenic contamination is of very high concern due to the activities of Gold Mine
situated at Wangsaphung district, Loei province, far away approximately 550 km. from
Bangkok to the northeast of Thailand. For the purpose of preventive measure and land use
management in near future, the samples of top soils, water and plants were collected from
the surrounding area of Gold Mine, within watershed covering gold mine and nearby
watershed, to conduct the contamination testing. Laboratory test results have shown that
all of those samples were contaminated with arsenic and contaminant levels in
average are of 1.34 – 497.94 mg/kg in soil, 0 – 0.3 mg/kg in plants and 0.001-0.01 mg/l
in surface water. Contamination in soils and plants were found higher much larger than
those in surface water flown from the tailing of gold mining disposal pond. As of these
results, It reasonably indicates that there naturally exists the arsenic contaminated

throughout the area not only within watershed in which the gold mine situated but also in the
outside area. The remarkable contamination of arsenic in the environment that were founded
in some specific positions were typically the cause of human activities such as gold mining,
agricultural management or others in land use.

INTRODUCTION

Exposure to arsenic can result in a variety of health problems in humans, including
various forms of cancer (e.g. skin, lung, and bladder), cardiovascular and peripheral vascular
disease, and diabetes. Human encounter arsenic from natural and anthropogenic sources
(Henke, 2009). Environmental Protection Agency (U.S. EPA) specified that the arsenic
contamination in drinking water should be less than 10
μ
g/l. In case of soils used for
agriculture and for other usages, the Office of National Environment Board of Thailand
set the maximum concentration limits (MCL) being of 3.9 mg/kg and 27 mg/kg, respectively.
Arsenic enters the environmental through herbicides, wood preservatives, and
mining industry (Chopra, Parmar, 2007). It can distribute in either soil or water, transport to
other places, pollute to water resources, and subsequently affect water for daily consumption.
Gold mining also contributes to the distribution of arsenic. During gold extraction, arsenic,
which is the composition of Arsenopyrite, is also separated and diffused into soil and water,
and pollutes to the environment.
Gold mining at Wangsaphung district, Loei province of Thailand, is the one of
mining industry that encountered this problem. After starting its work in 2006, villagers
from 6 villages complained that the natural water they normally use become contaminated
with arsenic resulting in affected human life, which has never been before. Related
government agencies and staffs from the gold mine have investigated the arsenic contamination
in both surface water and groundwater; however, they revealed that the contamination levels

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were not more than MCL specified by U.S.EPA. As of those results, there are still much
more suspects that why villagers were threatened by arsenic or arsenic contaminated in other
medias not only in the water.
To acquire the solution, this study was performed to investigate the contaminant
of arsenics in soils and plants compared to those in water. The study areas were located
not only within the interesting sub-catchment area that covering gold mine and 6 mostly
risky villages but also in the outside area to verify that the arsenic contaminants have
been formerly existed or really diffused from the gold mine. The results would give the
preliminary informations for planning to use in this area which will be advantageous for
managing the agriculture and living area in near future.

GENERAL INFORMATION

Loei, one of 76 provinces of Thailand, is situated in Northeastern part attached to the
Maekong River and border of Lao People's Democratic Republic. The study area, which is
mountainous and plateau area, is in Wangsaphung district of Loei province (Fig.1). The
altitude of gold mine is about 300 meters from mean sea level. Within 5 kilometers from
the gold mine has 10 villages, and there are 6 villages that have the most impact from
arsenic, including, Ban Nam Huai, Ban Na Nong Bong, Ban Huai Phuk, Ban Kok Sathon,
Ban Kaeng Hin, and Ban Tak Daed (Fig.2). The nearest village to the gold mine, 250 meters
from the mine and at the altitude of 277 meters from the mean sea level, is Ban Na Nong
Bong village. In those 6 villages, the farthest one is Ban Tak Daed, which is 5 kilometer
from the mine and at the altitude of 276 meters from the mean sea level. Most of lands
were engaged in farming and cropping plants such as corns, tapiocas, soybean, and rubber
trees.
Within sub-catchment area covering the gold mine and villages, there are many
small waterways, such as Huai Nam Chan, Huai Muno, Huai Haeng, Huai Khok Yai and
Huai San, flowing from high elevation at the top of plateau directing to low elevation area
and combining altogether to be one stream, called Nam Huai stream, before passing
through villages and out of the sub-catchment area into Loei River. The direction of surface

water flow is shown in Fig.3. The burnt rice affected by arsenic (Fig.4), claimed by the
villagers, was found at the Phulek creek (Fig.5).

SAMPLING

COLLECTION

AND

TESTING

Plants, soils and water samples at six locations had been taken in order to quantify
the leveling of arsenic contaminant. Five sampling locations are within the interesting
sub-catchment area whose boundary covers gold mine and affected villages; the other one
location, location no.5, was determined to be control point or reference point at the area
outside. The locations of samplings were shown in Fig.6. Detailing of samplings are
described as follows:
• Plants sampling: Total amount of 125 plant samples were collected from those
6 locations previously described. At each location, both annual crops and perennial plants
had been gathered to examine the level of arsenic contaminated in plants. Oak ferns that
are likely to grow up near water way as in location No.3, No.4 and No.6 were also
collected for contamination testing. Some plants such as common tobacco (Nicotiana
tabacum), Lemon grass (cymbopogon citratus Stapf), etc, are skipped out in some
locations because of having no cultivation in those areas.
• Soil sampling: At each location, one borehole was drilled into the ground to the
depth of 3 meter from the existing ground level and soil samples were collected at each
0.50 meter from surface through the bottom depth of borehole. In order to identify soil

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types in accordance with Unified Soil Classification System, methods of drilling and

collecting soil samples were performed following the guidance of American Society for
Testing and Materials (ASTM, 2000). Each soil sample was measured pH value before
wrapping with foil sheet and coated with paraffin to protect the moisture loss and
oxidizing reaction that might be occurred during carry on for further tests in laboratory.
The positions of each borehole are at the corresponding location number such as BH1 at
location No.1, BH2 at location No.2 and so on as depicted in Fig.6. As clearly seen, BH5 is at
location No.5, that is Ban Kok Chumsaeng, at outside the interesting sub-catchment studied
area.
• Water sampling: At the same location of soil and plants samplings, surface
water were collected for arsenic contamination testing. One sample was taken for each
location except the location No.6 that four samples were intentionally collected around
that area because there are small water ways pass through, one of which flows from the
high elevation swamp that is not far from mine tailings. All positions of water samplings
are at the same locations as plants and soils sampling (Fig 6.). The samples are treated to
remain acidic by nitric acid (5% concentration), poured in the light brown bottles for
laboratory test.
• Testing: Inductively Coupled Plasma Mass Spectrometry (ICP-MS) method
was utilized to quantify the arsenic contaminants in either soil or water. This technique
provides high precision determination of substance, even metallic or non-metallic, from
relatively small amount of samples (Skoog et al., 2007). The procedure starts from
grinding/homogenization, weighing, digestion, dilution, and final measurement.
Since this technique related to analytical chemistry and spectrometry, more details of
this method can be found in Bailey et al, (2003).

RESULTS AND DISCUSSION

• Arsenic contamination in plants
Annual crop: Laboratory results as shown in table1 reveal that there are arsenic
contaminant in plants at all locations. At each location Pumpkin leaves (Cucurbita
moschata Duchesne) is the most arsenic contaminated annual crop. Taro leaves

(Colocasia esculenta (L.) Schott), Soy bean leaves (Glycine max (L.) Merr.) and
Common tobacco leaves (Nicotiana tabacum L.) also have been contaminated in great
values but somewhat less than Pumpkin leaves. It was found very less contamination in
Lemon grass (Cymbopogon citratus Stapf) Chilli pepper (Capsicum frutescens L.) and
Sesbania flowers (
Sesbania javanica Miq
.) except at Location No.6 Lemon grass and Chilli
pepper seem to be contaminated in significantly higher value.
To determine as overall perspective, arsenic contents of all plant samples were plot
versus locations which being arranged in sequential manner from high elevation to lower
elevation as shown in Fig.7. Determining the graph, among six locations the contamination
levels in Pumpkin leaves (Cucurbita moschata Duchesne) and Taro leaves (Colocasia
esculenta (L.) Schott) are of highest values at location No.2, the values are1.04 mg/kg
and 0.70 mg/kg respectively for each plant; and contaminant levels in thus plants are
consecutively lower at the location No.6, No.3 and No.1.
Perennial plants: From table1, at each location Burmes grape (Baccaurea ramiflora
Lour.) was the plant that having been contaminated the most; except for location No.4
that Tamarind fruit (Tamarindus indica L.) is insignificantly higher more than Burmes
grape. Contamination level of all samples from location No.1 and No.3 are significantly
high as compared to all of those in the other locations.

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Also as in annual crops, the contaminant level in Burmes grape (Baccaurea ramiflora
Lour.), the most contaminated perennial plant, is highest at location No.2 and
consecutively lower at location No.6, No3 and No.1 as shown in Fig.7.
Fern: Oak fern (Dryopteris amboinensis Ktze.F) at location No.6 was contaminated
at the amount of 0.67 mg/kg which is the greatest value. At location No.3 and No.4,
arsenic contamination in Oak fern (Dryopteris amboinensis Ktze.F) are of 0.23 mg/kg
and 0.16 mg/kg, respectively.
As a result described above, it can be seen that there are arsenic contamination in plants

at all locations and are of primarily high to lower quantities from location No.2, No.6, No.3
and No.1 respectively. There are very most uptakes in Pumpkin leaves (Cucurbita
moschata Duchesne) for annual crops, Burmes grape (Baccaurea ramiflora Lour.) for
perennial plants and also Oak fern (Dryopteris amboinensis Ktze.F) at location No.6.
Considering topographic map and location studied (Fig.6), it may be possible to give
a reason that Location No.2 is very close to gold mine thus confronting directly to water
contaminated with some unintended pollutants including arsenic. More likely in location
No.6, its position is at the mountain pass, called Phulek creek, through which it was passed
by small waterways coming from the high elevation swamp that is not far from mine
tailings; it would be a greater chance for this location to be contaminated with arsenic than
the location No.3 and 4 that are even beside waterway but farther away.
Initially, Arsenic contaminant in plants as foregoing delineated seem to be the cause of
pollution from swamp closed to mine tailings; however, evidence from plant samples at
location No.5 outside sub-catchment area, exhibit that there are also arsenic
contamination in plants and content levels are not much less than of those within the
interesting area. So it can be stated that, in reality, there are arsenic naturally dispersed
throughout the areas.

Arsenic contamination in soil
Soil samples from 6 locations, called in corresponding points as bore holes (BH)
number, were classified using the Unified Soil Classification System. Soil profiles and their
altitudes were arranged in the orderly manner from high to lower existing ground
elevation, those are BH5, BH2, BH6, BH3, BH1 and BH4, respectively, as shown in
Fig.8.
The soil profile of each borehole is relatively similar composed of alternating layers
between clay, silty clay and sandy silty clay which are smaller grain sizes and higher cohesion
than purely sandy soils. Because of their small grain sizes and high cohesions, it causes
leading to be low permeability medias.
Laboratory test results show that all soil samples of 6 boreholes have arsenic contaminants
(Table 2). The relationship between concentration of arsenic with depth for 6 boreholes

shown in Fig.9 displays that there are arsenic contaminated throughout the depth of root
zone, 3 meter from soil surface. Content levels of arsenic contaminated in soil from low
to high are BH2, BH5, BH4 and BH6, respectively, and contaminant levels in BH3 is in
between BH2 and BH5. Soil samples of BH5, which its location is outside the interesting
area, have higher arsenic concentration at the upper layer than lower depth. Visible
evidence from Fig.9 exhibits the most Arsenic contaminated soil is at BH6. The
contamination levels in BH6 are substantially high at the top and steeply decrease at lower
depth; the concentration levels are of 56.17 mg/kg soil to 8.00 mg/kg soil, from highest to
lowest value, respectively, which are higher than the maximum concentration level
(MCL) allowable level for soils used for living and agriculture specified by The Office of
the National Environment board of Thailand. By this specification, the arsenic contaminant
for dwelling and agriculture area must be less than 3.90 mg/kg soil, and for other usages

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must be less than 27 mg/kg soil. Contamination levels at BH 4 are much less than those of
BH6 but still exceed MCL.
Determining location of each Bore Hole in topographic map, the location of BH6,
corresponding location No.6 in plant samplings, is at the mountain pass called Phulek creek
as previously described. It can possibly give a reason that the substantially high arsenic
concentration at the top of soil profile in BH6 is the cause of arsenic pollutant exposed from
the area near mine tailings and being carried by surface flow or seepage water downward and
thus accumulating at this location. At lower depth of BH6, arsenic concentration decreases
to the minimum value close to the concentration of BH4. It can be noticed that the arsenic
concentration values at the bottom depth of both BH6 and BH4, which is both nearby the
waterway, come close together; this value might be the minimum contaminant
concentration in soils seated beside along the water way. BH5 at outside interesting area
also has much high arsenic concentration more than MCL at nearly the top and gradually
decrease with depth; it exhibits the natural existence of arsenic in the area around. Overall
perspective view, concentrations of arsenic in BH1, BH2 and BH3 are much less than of
those in the other boreholes and somewhat near or less than the MCL.

• Arsenic contamination in water
Laboratory results show that the amount of arsenic in surface water at location No.1,
No.2, No.3, No.4 and location No.5, as shown in table 3, are less than 0.01 mg/l, which is
an MCL for drinking water specified by U.S. EPA. In contrast, at location No.6 there
are 4 samples of water including sample No.6.1, No.6.2, No.6.3 and No.6.4; all of them
have arsenic concentration much significantly higher over the MCL as shown in Fig.10.
At location No.6, Phulek creek, which is the toe of mountainous pass as described
before; the high level of arsenic concentrations in this location match up the results of
contamination in plants and soils that are also so much high in this location. Initially, it
may be likely to conclude that the highly contaminated level of arsenic at the top surface of
soil, water and plants in this location, No.6, tends to be the result of arsenic transportation
from nearby swamp.

CONCLUSION

This study reveals that the arsenic contaminant can be found in plants, soils and
surface water at all locations. The contaminations have been occurred not only in the
studying sub-catchment area but also the area outside. Therefore it would be possible that
the arsenic naturally exists over there long time before. At some locations, there has been
much higher concentration than those in the other locations due to the accumulation of
arsenic carried by water. As we can see at soil borehole No.6 (BH6) and borehole No.4
(BH4), which are beside the waterway, there are much higher of arsenic concentrations and
their values are more than 3.9 mg/kg, which is the specification of soil for dwelling and
agriculture specified by the Office of the National Environment Board of Thailand.
The remarkable contaminants of arsenic in Surface water at location No.6 consistently
agree with those in top soil at the same location. This position is the toe of mountain pass,
where the water flow from the upper area, which is the swamp closed to mine tailings. The
water might carry down the arsenic, that may pollute in the swamp, and take it settle at
downstream. Contamination in root zone of 3 meter depth soils and in plants stated that

arsenic already enters the food chain. Consequently, increasing attention should be paid for
preventing, managing and remediation.
Further studies of arsenic distribution trend and its transportation phenomena are of
very much interest in this area especially in soil media because nowadays it contaminates
into food chain which may pose serious health risk to human life. The influence factors for

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studying the behavioral distribution of arsenic such as the geological characteristics,
compositions of soil, porosity and permeability of soil, land use, and soil loss etc., may be
needed to be determined. These are important for analyzing the arsenic mobility, which
would be beneficial for planning and management of area for dwelling and other usages in
near future.




REFERENCE

American Society for Testing and Materials (2000). Annual Book of ASTM Standards.
Vol.04.08, West Conshohocken, PA.
Bailey, R.M., Stokes, S. and Bray, H. (2003).Inductively-Coupled Plasma Mass Spectrometry
(ICP-MS) for dose rate determination: some guidelines for sample preparation
and analysis. Oxford, UK: Oxford Luminescence Research Group, School of Geography
and the Environment, University of Oxford.
Chopra, H.K. and Parmar, A. (2007). Engineering Chemistry - A Text Book. India: Alpha
Science International Ltd., 5-10.
Henke, K.R. (2009). Arsenic – Environmental Chemistry, Health Threats and Waste
Treatment. 1
st
ed. John Wiley & Sons. Ltd., 1-5, 238-243.

Plant Genetic Conservation Project Under the Royal initiative of Her Royal Highness Princess Maha
Chakri Sirindhorn. Plant genetic resources. Retrieved September 1, 2010. from
/>
Skoog, D.A., Holler, F.J. and Crouch, S.R. (2007).Principles of Instrumental Analysis. 6
th
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Canada: Thomson Brooks/Cole, 291-299.
United States Environmental Protection Agency. Arsenic in Drinking Water. Retrieved
February 10, 2010. from