Journal of Environmental Protection, 2011, 2, 1211-1217
doi:10.4236/jep.2011.29139 Published Online November 2011 (http://www.scirp.org/journal/jep)
Preservation Artifacts and Loss Pattern of Arsenic:
A Case Study from Highly Contaminated Location
in Central-East India
Piyush Kant Pandey1, Hansa Zankyani2, Madhurima Pandey2
1Bhilai Institute of Technology, Kendri, New Raipur (Chhattisgarh), India; 2Centre for Environmental Science & Engineering, De-
partment of Engineering Chemistry, Bhilai Institute of Technology, Durg (Chhattisgarh), India.
Received August 14th, 2011; revised September 26th, 2011; accepted November 2nd, 2011.
ABSTRACT
Arsenic is the focus of public attention because of its wider prevalence and toxicity. Proper sampling is important in
characterizing toxic water contaminants in the groundwater. The present paper studies aspects of sampling, preserva-
tion artifacts, analytical issues etc. in a natural arsenic contaminated groundwater. The samples were collected from
arsenic contaminated groundwater at three locations of village Kaudikasa in Rajnandgaon (Chhattisgarh). The stan-
dard method of samp ling and preservation of arsenic was examined. The permitted sample holding time in this state is
180 days which has been found to be unrealistic on examination. The communication also compares the loss pattern of
arsenic in unpreserved samples with samples preserved and kept at 4˚C. It was found that about As losses dur ing hold-
ing after preservation were about 0% in one day, 35% in seven day, 70% in fifteen day, and 65% in thirty days time.
Hence, the present recommended method of preservation leads to huge under reporting of As in natural samples. If the
pattern of losses observed at the present location exists at other locations then the actual As levels could be much
higher than the reported ones.
Keywords: Arsenic, Groundwater Contamination, Preservation, Loss Pattern, Chhattisgarh
1. Introduction
Arsenic is one of the oldest poisons known to men and
its applications throughout history are wide and varied
[1]. Arsenic is a problematic and naturally occurring
toxic contaminant, which has many chemical species,
each with a different toxicity and mobility [2]. A recent
study on arsenic toxicity have shown that exposure to
arsenic through drinking water has direct effect on the
early stages of life when the brain is usually most vul-
nerable [3]. Yu Chen and colleagues add to the evidence
that arsenic in water increases mortality from cardiovas-
cular disease with the findings of their prospective cohort
study in Bangladesh [4]. Ingestion of inorganic arsenic in
drinking water causes cancer of the skin, bladder, lung,
liver, and kidney [5]. Inorganic arsenic species arsenite
[As(III)] and arsenate [As(V)] predominate in natural
water [6]. Organic arsenic species, such as monomethyl
arsonate (MMA) and dimethyl arsinate (DMA), are only
present at low levels [7]. Inorganic arsenic species in-
clude known carcinogens [8]. Of these, As(III) is more
toxic than As(V), while the toxicities of the organic arse-
nic species have not been fully evaluated [9-11]. Arsenic
contamination in groundwater and related diseases affect
major parts of Ganga delta down stream of Rajmahal
hills in West Bengal, India and other low lying areas in
Bangladesh [12-16]. Alluvial areas from USA, Hungary,
China, Taiwan and Vietnam are also similarly affected
[17-19]. The problem has also been reported from Kaudi-
kasa, district Rajnandg aon, Chhattisg arh [20-23]. Daus et
al. (2002) used nitrilotriacetic acid (NTA), hydrochloric
acid (HCl), phosphoric acid (H3PO4), and acetic acid for
this procedure [24], and found the best results with 0.01
mol/L H3PO4. A detailed description of the preservation
and sampling of groundwater was given in our previous
publication [25]. This paper further studies the implica-
tions and reports arsenic losses in preserved groundwater
samples. Bednar et al. used ethylenedinitrilotetraacetic
acid (EDTA), sulfuric acid (H2SO4), nitric acid (HNO3),
and HCl to preserve inorganic arsenic species in ground-
water and acid mine drainage samples [26]. Arsenic con-
tamination has been acknowledged as a major public

Preservation Artifacts and Loss Pattern of Arsenic: A Case Study from Highly Contaminated Location 1212 in Central-East India
health issue by the World Health Organisation (WHO)
based on its international prevalence; WHO has proclaimed
that it requires to be dealt with on an emergency basis [27].
Sampling is an extremely important consideration in
properly characterizing groundwater for toxic water con-
taminants removal. It is a complicated task to analyze the
toxic elements in natural water samples as they are pre-
sent in a low co ncen tration and a re subj ect to a var iety of
chemical modifications after sampling. Arsenic is the
focus of public attention because of its toxicity. Arsenic
analysis, its toxicity, and its fate in th e environment have
been broadly studied, still its blank values, adsorption to
sampling materials and pre-concentration of water sam-
ples as well as stabilization of arsenic compounds in wa-
ter samples under field conditions have been very little
investigated. Arsenic species are readily transformed in
nature by slight changes in conditions. Each species has
a different toxicity and mobility. Also, the analytical p ro-
cedure must be selected carefully because the levels and
hydride generation efficiencies of arsenic in different
species can vary, even for the same amount of arsenic
[28].
Whatever the collection and storage method used, sub-
stantial oxidation of arsenic was commonly observed
over periods of weeks to several months [29]. The aim of
the preservation is to maintain the original concentration
of the trace elements and their chemical nature. A proper
estimation of the concentration and speciation of the
samples is important from the health point of view,
where the dose and its chemical species govern the likely
effects. A proper estimation of the concentration and spe-
ciation is important from the health point of v iew, where
the dose and its chemical species govern the likely ef-
fects. Errors associated with the collection and handlings
of a sample generally exceed those associated with the
analysis [30].
Preservation of groundwater samples aims to retard
the biodegradation reactions, precipitation and co-preci-
pitation reactions, hydrolysis reactions, sorption reac-
tions and any other physico-chemical reactions, which
may occur in a natural sample. Sample preservation us-
ually involves reducing or increasing pH by adding an
acid or base preservative. Th e total conc entratio n of inor-
ganic arsenic species must be preserved in the field to
eliminate changes caused by metal oxyhydroxide preci-
pitation, photochemical oxidation, and redox reactions.
The standard practice for the preservation of metals, ex-
cept mercury and hexavalent chromium, is the addition
of HNO3 until a pH less than 2 is obtained and the sam-
ple holding time in this state is 180 days. The recom-
mended sample container is either glass or plastic bottle
that is typically polyethylene, polypropylene or polyvinyl
chloride [31-34].
Once a sample is taken, the constituen ts of the sample
should be maintained in the same condition as when col-
lected. When it is not possible to analyze collected sam-
ples immediately, samples should be preserved properly.
Methods of preserva tion include cooling , pH control, and
chemical addition. The length of time that a constituent
in groundwater will remain stable is related to the char-
acter of the constituent and the preservation method
used.
Arsenic species are readily transformed in nature by
slight changes in conditions. Each species has a different
toxicity and mobility. Also, the analytical procedure
must be selected carefully because the levels and hydride
generation efficiencies of arsenic in different species can
vary, even for the same amount of arsenic. Based on
extensive experimental results in Fe (II)-contaminated
challenge water, it was found that EDTA-HAc could be
used to preserve the arsenic species for at least 28 days in
opaque plastic bottles. Although th e alternative preserva-
tives, H2SO4 and H3PO4, successfully preserved the ori-
ginal As(III)/(V) speciation under some conditions, these
preservatives were generally unsuccessful for the desired
28-day period under reducing and oxidizing conditions in
the sample pH range of 6.5 - 8.4 and in the presence of 3
mg/L Fe(II) [35].
2. Materials and Method
Arsenic contaminated groundwater samples of three lo-
cations of Kaudikasa district Rajnandgaon were the sam-
pling sources.
The methods enumerated in Handbook for Sampling
and Sample Preservation of Water and Wastewater [36]
was adopted for this experiment. The brief detail is pro-
vided in Table 1. Two series of samples were taken for
every location. The first series was preserved as per the
guidelines.
The second series was kept without preservation.
While in storage both types of samples were maintained
at 4˚C. The onsite As analysis was carried out using As
test kit (Merck, Germany). Both ranges (0.02 - 3 mg/L
and 0.1 - 3 mg/L) of the Merckoquant kits were used
depending on the expected level of As. Arsenic was ana-
lysed in laboratory by hydride generation Atomic Absor-
ption Spectrophotometer (Varian AA 240 FS), Merck
certified standard solution and chemicals were used.
Double distilled and deionized water was u sed in the pre-
paration of standard solutions and for dilution of the
samples.
3. Result and Discussion
The various equilibria occurring in natural waters in-
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Preservation Artifacts and Loss Pattern of Arsenic: A Case Study from Highly Contaminated Location
in Central-East India
1213
Table 1. Required containers, preservation techniques, and holding times.
Parameter Container Preservative Max i mum Holding Time
Inorganic Tests
Acidity P,G Cool, 4˚C 14 days
Alkalinity P,G Cool, 4˚C 14 days
BOD P,G Cool, 4˚C 48 hours
Cool, 4˚C
COD P,G H2SO4 to pH < 2 28 days
Hardness P,G HNO3 to pH < 2 6 months
Hydrogen ion (pH) P,G None required Analyze immediately
Metals
Chromium (VI) P,G Cool, 4˚C 24 hours
Mercury P,G HNO3 to pH < 2 28 days
Metals, except above P,G HNO3 to pH < 2 6 months
Residue, non-filterable (TSS) P,G Cool, 4˚C 7 days
Residue, settleable P,G Cool, 4˚C 48 hours
Residue, volatile P,G Cool, 4˚C 7 days
Adopted from Environmental Protection Agency Guidelines for handling and preserving samples. P = plastic, G = glass.
volving metal ions make the sample preservation critical,
as changes between arsenate and arsenite can be caused
by bacterial activity, as well as by oxidising or reducing
components in the natural water. In general, the addition
of acids has been recommended for natural water pre-
servation [37] but this procedure can not be used for ar-
senic speciation, as it would affect the arsenic forms pre-
sent.
The three locations of village Kaudikasa district Rajn-
andgaon were analysed. The samples were first analysed
on site by As testing kit and thereafter in laboratory at
specified time intervals. Each and every sample of Loca-
tion I, Location II and Location III were analyzed 4 times
after preservation that is first day, seventh day, fifteenth
day and thirtieth day. Triplicate analyses, for each par-
ticular sample, were performed. In Figure 1 the As con-
centration in preserved and unpreserved samples of all
three Locations is shown. The Location II shows the
maximum loss of As concentration in comparison to Lo-
cation I and III.
The results further show that the concentration of As
decreases with the time and after some days it becomes
constant. However, on the first day after sampling no sig-
nificant losses of As concentration was observed. Then,
the rate of loss of As increased with holding time. The
maximum loss was observed within first 7 days. The rate
of loss was positive till 15th day and then no significant
loss was observed till 30th day (Figures 2, 3 and 4). The
total percentage loss of arsenic samples of Location I,
Location II and Location III of groundwater, collected
from Kaudikasa is shown in Figure 5.
Overall taking all three locations together the average
percentage loss of As was 0% in one day, 35% in seven
day, 70% in fifteen day, and 65% in thirty days time Ta-
ble 2. Individually the Location II showed more promi-
nent loss pattern compared to the other two locations.
This means that As losses are expected to be more rapid
in case of higher As va lues. This observation is very sig-
nificant because in the As studies worldwide, the As
concentrations are generally believed to be more or less
stable and are expected to follow a law of average. Look-
ing to this trend monitored at Kaudikasa we are inclined
to say that the reported results may not be really reflect-
ing the true picture of As contamination. It is because of
the fact in the most studies the sample holding time is
neither specified nor mentioned in the results. In many
cases the actual analysis might be performed very late
after the sampling. We are further inclined to say that
many of the reported results could be 60% - 70% less
than the actual. If this is the case then we have to realize
that we are dealing with a monster which is more power-
ful than what we believe. To effectively deal with such a
condition it is necessary that the proper sampling, time
specified preservation and analysis regime is necessary.

Preservation Artifacts and Loss Pattern of Arsenic: A Case Study from Highly Contaminated Location 1214 in Central-East India
Figure 1. Arsenic loss (mg/L) pattern of three Locations during the holding time of one month.
Figure 2. Arsenic loss (mg/L) pattern of Location I during specified time intervals.
Figure 3. Arsenic loss (mg/L) pattern of Location II during specified time intervals.
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Preservation Artifacts and Loss Pattern of Arsenic: A Case Study from Highly Contaminated Location 1215
in Central-East India
Figure 4. Arsenic loss (mg/L) pattern of Location III during spec i fie d time intervals.
Figure 5. Percentage loss of Arsenic at three Locations.
Table 2. Average percentage loss of Arsenic at three locations at different time intervals.
1st Day 7th Day 15th Day 30th Day
Location I 0 37 57 55
Location II 0 30 78 73
Location III 0 39 74 67
Overall Loss pattern 0 35 70 65
Further the study on sampling and pr eserva tion artif act at
all major As contaminated locations it should be carried
out immediately.
Our work has found that the As contaminated levels at
Kaudikasa village are still heavily contaminated [25].
Table 3 presents the comparison of reported yearly mean
values of arsenic levels of three years i.e. 1999, 2000 [25]
and 2008 [38]. Here we find the difference in levels re-
ported. The reason for this difference could be either a
genuine geo-chemical reason or could simply be due to
the preservation artifacts. In either case a more careful
and stringent QA/QC is called for.
As far as the reason of such losses is concerned we
had hypothesized that the loss of arsenic may be due to
the conversion of arsenic groundwater samples to the
volatile phase [25]. Based on this sequel study the prob-
able loss in polyethylene bottles due to conversion of As
to volatile phase appears valid. It is because we have also
found less As losses when the glass bottles were used as
sample container.

Preservation Artifacts and Loss Pattern of Arsenic: A Case Study from Highly Contaminated Location 1216 in Central-East India
Table 3. Comparison of reported arsenic levels from the same locations in Kaudikasa village.
Location Identifying number Area Mean arsenic (µg/L)
2008 Mean arsenic (µg/L) 2000 Mean arsenic (µg/L) 1999 Total arsenic (µg/L) (NEERI, 2000)
Location I HP 9 Anganbadi 462 1120 960 826
Location II HP 6 Kunjam Ho u s e 2817 3050 1965 1890
Location III HP 12 Old Boys Hostel 966 1265 300 245
NEERI, 2000, Study of arsenic contamination in the groundwater of Block Chowki, District Rajnandgaon (MP), National Environment Engineering Research
Institute, Nagpur.
4. Conclusions
Analytically, the nature of arsenic compounds present
and other concomitant parameters in the contaminated
samples in Kaudikasa village need a further study to ex-
plain the higher rates of arsenic loss compared to the
synthetic samples or similar samples from different loca-
tions. The results also show that the sampling and pre-
servation artifacts may result into serious under-reporting
of arsenic levels, particularly in developing countries.
It is suggested that many of the repo rted r esults around
the world could be 60% - 70% less than the actual. If this
is the case then the arsenic monster is more powerful
than what we believe. To effectively deal with such a
condition it is necessary that the proper sampling, time
specified preservation and analysis regime may be fol-
lowed. Further the study on sampling and preservation
artifact at all major As contaminated locations it should
be carried out immediately and the results be interpreted
accordingly.
The reason for the loss of As after sampling appears to
be due to the conversion of soluble As into volatile spe-
cies which could permeate out more easily in polyethy-
lene bottles than the glass one.
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