EVALUATION OF TOTAL AND SPECIES CONTAMINATION FROM ARSENIC IN THE RIVERS AND BAY OF THE PAK PA-NANG CATCHMENT, SOUTHERN THAILAND

1
EVALUATION OF TOTAL AND SPECIES CONTAMINATION
FROM ARSENIC IN THE RIVERS AND BAY OF THE PAK
PA-NANG CATCHMENT, SOUTHERN THAILAND
M. E. Foulkes1, S. Rattanachongkiat3, G.E.
Millward1, W. Utoomprurkporn2, M. Taiyaqupt2, P.
Chongprasith3 and P. Tantichodok4 1 School of E,
O and Environmental Sciences, University of
Plymouth, Plymouth PL4 8AA UK 2Faculty of
Science, Chulalongkorn University, Bangkok
3Pollution Control Department, MNRE
Bangkok 4Walailak University, Nakhon Si
Thammarat, Thailand

• INTRODUCTION
• The Pak Pa-Nang Estuary is located in southern
  Thailand and its catchment comprises a tin mining
  area. More than 1,000 inhabitants of the region
  are suffering from various stages of arsenic (As)
  poisoning. Drainage from the high concentration
  of As in spoil tips of the mined area could
  affect water and sediment quality in the bay,
  which is biologically productive, including
  substantial mussel aquaculture. Information on
  the speciation of arsenic in this bay will help
  identify any current toxicity problem and also
  serve in formulating protection strategies for
  the future.
• AIMS OF THE STUDY
• Determination of arsenic speciation in fauna
  and sediment samples using High
• Performance Liquid Chromatography (HPLC)
  coupled with Inductively Coupled
• Plasma Mass Spectrometry (ICP-MS)
• Application of the technique to assess the
  impact of As contamination to the Pak
• Pa-Nang Estuary
• METHODOLOGY
• Sediments and commercial sea foods, sardines
  (Escualosa thoracata), croakers (Johnius
  belangerii), catfish (Plotosus canius) and
  swimming crabs (Portunus pelagicus) were
  collected from the Pak Pa-Nang Estuary in August
  2001 and immediately freeze-dried. The dried
  samples were ground, using an agate mortar and
  pestle, and digested for total As in a Teflon
  bomb by microwave digestion using nitric acid and
  hydrogen peroxide. Following the digestion total
  As was determined using N2 ICP-MS?.
• Arsenic speciation studies in the samples were
  employed using HPLC coupled with ICP-MS following
  a low power microwave extraction and an enzymatic
  extraction for sediment and fauna samples,
  respectively. Speciation studies of arsenic are
  necessary because the toxicity of arsenic depends
  on the nature of its species rather than total
  concentration.

ARSENIC SPECIES IN THE SEDIMENT SAMPLES (µg g-1)
DIGESTION PROCEDURE FOR TOTAL As IN FISH AND
AVAILABLE As IN SEDIMENT
EXTRACTION OF As SPECIES FROM
FISH
EXTRACTION OF As SPECIES FROM SEDIMENT



0.25 g dry sample
0.25 g dry fish
0.5 g dry sediment



4 ml HNO3 1 ml H2O2
0.1 g trypsin in 0.1 M NH4HCO3
25 ml 1M H3PO4
Microwave digestion for 5 min
Extraction in a shaking bath (37C) for 12 hr
Extraction in a microwave digester (45w) for 20
min
50 ml solution
25 ml solution
25 ml solution
N2-ICP-MS Analysis
HPLC-ICP-MS Analysis
HPLC-ICP-MS Analysis
Extraction efficiency of arsenic using
phosphoric acid compared with total available
arsenic in sediments ranged from 95 to 108 .
Recovery of species from spiking of sediments
ranged from 90 to 100.
DISTRIBUTION OF TOTAL AVAILABLE ARSENIC IN THE
SEDIMENT SAMPLES
HPLC System for As Species in Fish
Column Hamilton Resin PRP-X100 10µm i.c. (
250 x 4.6 mm ) Injection loop/µl 100 Flow
rate/ml min-1 1.5 Mobile phases a 5 m mol l-1
Na2 SO4 pH 10-10.5 b 0.05 mol l-1 Na2 SO4
pH 10-10.5 Standard solution 200 ppb AsB, DMA,
MMA and Inorganic As Retention time/min 15
Chromatogram of Standards
M. Foulkes1
HPLC cycle -Isocratic elution Step gradient
Re-equilibrate Mobile phase gta 5 min
gtb 3 min gta till finish
ARSENIC SPECIES AND THEIR TOXICITY
Station 1
Station 3
Station 4
Adjusted with ammonia solution
HPLC System for As Species in Sediments
Column Hamilton Resin PRP-X100 10µm i.c. (
250 x 4.6 mm ) Injection loop/µl 20 Flow rate/ml
min-1 1.2 Mobile phases a 2 m mol l-1 H3 PO4 pH
7.5 b 50 m mol l-1 H3 PO4 pH 6 Standard
solution 100 ppb AsIII, DMA, MMA and
AsV Retention time/min 15
Chromatogram of Standards
DISCUSSION AND CONCLUSIONS Methods have been
developed for the determination of As and its
species in fauna and sediments from the Pak
Pa-Nang Estuary, using analytical procedures that
gave near to full extraction efficiencies and
recoveries.   While the As concentration in the
fauna and sediment samples is relatively low (not
greater than 16 µg g-1) the major species present
and available for cycling are different for the
two types of sample analysed. In fish and
crustaceans the major species present is the
non-toxic arsenobetaine (75 to 80) with smaller
quantities of the mildly toxic DMA (11 to 17).
The highly toxic inorganic As species (AsIII and
AsV) constituted some 5 to 12 of the total As in
fauna. This converts to approximately 2 µg g-1
inorganic As for a consumable fish or crustacean,
at the higher total As content found of 16 µg
g-1. Advisable levels for As in foodstuffs
suggest a 1 µg g-1 limit on inorganic As
particularly where the foodstuff constitutes a
regular or staple diet.   Only the highly toxic
inorganic As species (AsIII and AsV) were found
in the sediment samples. Considering the dynamic
conditions found in the estuary together with the
part that benthic organisms play in the estuarine
food chain, the supply of these highly toxic As
species to humans is likely to continue. This may
be for many years, particularly when the levels
of arsenic in sample cores are considered.

 
THE STUDY AREA IS CLOSE TO FORMER TIN MINING
AREAS AND THOUSANDS OF PEOPLE IN THE FORMER
MINING AREAS ARE SUFFERING FROM ARSENIC
POISONING
4
9
5
8
Pak Pa-Nang Estuary
HPLC cycle -Isocratic elution Step gradient
Re-equilibrate Mobile phase gta 3 min
gtb 6 min gta till finish
3
6
7
Adjusted with ammonia solution
2
1
TOTAL ARSENIC IN THE SAMPLES COMPARED WITH OTHER
AREAS
X Sediment sampling station X Sediment core
sampling station
? Former tin mining area
ACKNOWLEDGEMENTS The authors gratefully
acknowledge University of Plymouth, Chulalongkorn
and Walailak Universities and also their staff
for their very kind help in the laboratories and
with the field sampling.
10 km
Black spot disease
ARSENIC SPECIES IN THE FAUNA SAMPLES
PAK PA-NANG SAMPLING (AUGUST 2001)
REFERENCES 1 Hill, S.J, Ford, M.J., and
Ebdon, L., J. Anal. At. Spectrom., 1992, 7, 719.
2 Penrose, W.R., CRC Crit. Rev. Environ.
Control, 1974, 4, 465. 3 Brown, J., Kitchen,
K.and George, M., Teratog. Carcinog. Mutagen,
1997, 17, 71. 4 Cullen, W.R.and Reimer, K.J.,
Chem. Rev., 1989, 89, 713. 5 Neff, J.M.,
Environ. Toxicol. Chem., 1997, 5, 917. 6
Francesconi, K.A. and Edmonds, J.S., Arsenic and
Marine Organisms. Advances in Inorganic
Chemistry., 1997, 44, 147. 7 Branch, S.,
Ebdon, L. and Oneill, P., J. Anal. At.
Spectrom., 1994, 9, 33.
Boat-launching
Long Tail Fishing boat
Freeze-dried crabs
Sediment sampling
Sediment core sample
This work sponsored by
? The combination of chlorine introduced via the
sample with argon from the plasma can give rise
to the formation of 40Ar35Cl, which
interferes with the monoisotopic 75As the
problem was solved by adding the molecular gas
nitrogen about 4.5 (v/v) of total carrier
gas to the nebulizer gas of ICP-MS (N2 ICP-MS)
1
Croakers (Johnius belangerii)
Sardines (Escualosa thoracata)
Catfish (Plotosus canius)
Swimming crabs (Portunus pelagicus)
The Royal Thai Government
The British Council
? August 2002