IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Research article
erd

Passive Sampling Approach to Identify Contaminants ina Tropical FreshwaterI River System
TATIANA KOMAROVA*4.
72

Queensland Health Forensic and Scientific Services (QHFSS), Brisbane, Australia
Email: Tatiana_Komarova@health.qld.gov.auwo

CHULEEMAS BOONTHAI IWAIr
Faculty of Agriculture, Khon Kaen dUniversity, Khon Kaen, Thailands

ATCHARAPORN SOMPARN
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

NATSIMA TOKHUN
Faculty of Agriculture, Khon Kaen University, Khon Kaen,Thailand

BARRY NOLLER
Centre for Mined Land Rehabilitation (CMLR), Sustainable Minerals Institute, The Universityof Queensland, Brisbane, Australia
Received 17 January 2013

Accepted 10 June 2013(*Corresponding Author)

Abstract This study aimed to understand labile metal distribution and water quality
associated with agro-industry and farming activities along the Namphong River, a subcatchment of the Mekong River located in NE Thailand. An integrated sampling program
was designed to identify the range of potential contaminants in the Namphong River byincorporating active or grab sampling along with passive sampling using the diffusegradients in thin films technique (DGTs) for the bio available heavy metal forms, fieldmeasurement of pH, electrical conductivity, temperature and dissolved oxygen andlaboratory-based measurement of total solids, total alkalinity, hardness, nutrients anddissolved organic carbon concentration together with heavy metals (total and filtered (<0.45 µm) fractions). The DGTs were deployed at 10 different sites along approximately 50
km of the Namphong River for 4 days to enable sufficient integrative sampling of heavy
metals. One liter of water samples were collected from the sites before and after
deployment of the DGTs. Although total and filtered (<0.45 µm) concentrations of
cadmium, chromium, copper, lead and zinc in the Namphong River from active samplingsignificantly exceeded the trigger values of water quality guidelines for protection of
freshwater aquatic species, the concentration of metals estimated from DGT data indicatedmore accurately that the bio available metal levels were below the trigger values and that
there were no predicted effects on aquatic species. The agro-industrial area (pulp and sugarmills) was a major potential source of contamination of the Namphong River associatedwith increased levels of heavy metals (aluminium, chromium, cobalt, iron and manganese)but diluted to insignificant levels in the Namphong River. The release of copper, nickel
and lead to the downstream Namphong River occurred in the area of rice and mixed
vegetable cultivation and was most likely related to extensive pesticide use. The outcomeof this study will help to develop more focused monitoring of specific toxic heavy metals
at particular locations on the Namphong River.
Keywords active and passive sampling, aquatic ecosystem, DGT, heavy metals,
bioavailability

INTRODUCTION
The NE part of Thailand is the location of extensive wet-dry agricultural activities with major use© ISERD154

IJERD – International Journal of Environmental and Rural Development (2013) 4-2of irrigation from dam storage and some supplementation of water supply from groundwater
sources. The rivers systems of NE Thailand are also part of the sub-catchment of the Mekong River(Fig. 1). One of the sub-catchments of the Chi River is that of the Namphong River. Below theUbolratana Dam there are extensive agro-industry and farming activities along the NamphongRiver which flows to the Chi River and via the Mun River to the Mekong River. A key question
was the extent and the effects on aquatic species of heavy metal additions to the river system that
result from the collective of agricultural activities. River water may also be used for humanconsumption and recreational activities.
The Diffusive Gradients in Thin-films (DGT) technique uses passive sampling to give an
integrated concentration measurement (Davison and Zhang 1994). The DGT technique waspreviously described for measurement of labile metal forms in water and predicting their toxicity toaquatic biota (Komarova et al. 2012). In contrast, active sampling collects a grab sample at a fixedtime. This paper uses passive sampling techniques to measure dissolved inorganic compounds inwaters at sub-nanogram per liter levels. “Passive” samplers are defined as human-made devices
where sample collection is completely passive. The DGT technique is designed to accumulate
labile metal species in environmental systems including from water (Davison and Zhang, 1994;
Davison et al. 2000; Zhang and Davison, 1995; Zhang and Davison, 2000).
OBJECTIVE
This study aimed to understand the labile metal distribution associated with agro-industry andfarming activities along the Namphong River a sub catchment of the Mekong River located in NE
Thailand. The study addressed the following questions: (i) to compare passive DGT and active
sampling techniques for heavy metals and associated water quality in the Namphong River water
body for different locations; (ii) to compare labile heavy metal concentration data from the DGTtechnique with water quality guidelines that can be incorporated into the trace metal monitoring
programs in water together with traditional methods and replace them in the future; and (iii) to use
DGT analysis for labile metals to assess bioavailability to aquatic freshwater species.
METHODOLOGYThe DGT technique employed an ion exchange resin (Chelex-100) that was immobilized in apolyacrylamide gel (the binding or resin gel), to exchange analytic species from solution (Davisonand Zhang 1994). Chelex-based resins can be used for simultaneous collection of many metals inwater including aluminium (Al), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe),lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn) (Komarova et al. 2012). The binding gel wasseparated from the bulk solution by a permeable polyacrylamide gel (the diffusive gel) and asolution diffusive boundary layer.
An integrated sampling program was designed to identify the range of potential contaminantsin the Namphong River by using diffuse gradients in thin films technique (DGTs) for the passive(integrated) sampling of labile heavy metal forms, field measurements of pH, electricalconductivity (EC), temperature and dissolved oxygen (DO) concentration and active sampling for
total solids (TS), total alkalinity (mg/L CaCO3), hardness (mg/L CaCO3), nutrients, dissolved
organic carbon (DOC) and heavy metal concentrations for the total and filtered (< 0.45 µm)
fractions. DGTs were deployed for 4 days from 19-23 January 2012 to accumulate labile heavy
metals at 10 different sites along approximately 50 km of the Namphong River (Fig. 1).
One liter of grabbed water samples were collected before and after DGT deployment; themean concentrations of metals were calculated from the measured parameters. All measurementson the active water samples were undertaken in the field or at the Division of Land Resources andEnvironment, Department of Plant Sciences and Agricultural Resources, Faculty of Agriculture
Khon Kaen University. Following deployment, DGTs were sent by air courier to the Queensland
Health Forensic and Scientific Services (QHFSS), Inorganic Chemistry Division laboratory atCoopers Plains, Australia to separate the gels and elute the accumulated analyte from the binding© ISERD
155

IJERD – International Journal of Environmental and Rural Development (2013) 4-2

gel using dilute nitric acid. The concentrations of metals in the eluant were then determined byinductively-coupled plasma mass spectrometry (ICPMS). The time-averaged concentration ofdissolved metal species in the bulk solution, C, is then calculated using Eq. (1), which is derived
from Fick’s first law of diffusion (Zhang and Davison, 1995): M is the accumulated mass of ametal on the binding gel; Δg is the thickness of the diffusive gel, D is the diffusion coefficient of aspecific metal in the diffusive gel, t is the deployment time, and A is the surface area of thediffusive gel exposed to the bulk solution.
C = M Δg / D t A(1)

The assessment of water quality for the protection of the aquatic ecosystem made use of acombination of analytical methods based on following the Australian ANZECC/ARMCANZ(2000) decision tree process for assessing metal toxicity in water. An initial step was to calculate
site-specific trigger values for metals by using a correction for hardness, calculated from thecalcium plus magnesium concentrations expressed as mg/L CaCO3, to the default
ANZECC/ARMCANZ (2000) guideline value. This more accurately predicts aquatic metal toxicity
which decreases with increasing water hardness as soluble metal is precipitated. The next step inthe decision tree process used the measurements of metals in labile or bioavailable forms andmetals in particulate and insoluble colloidal fractions that could be measured through filtration(<0.45 µm membrane) to predict the bioavailable fractions of metals in waters. Thus DGT samplersoffered an alternative to conventional water sampling techniques for measuring labile trace metals.

AMekong River

BNamphong River
Mekong RiverCThailand
Khon Kaen

B
Khon Kaen
Chi River

Mun RiverBangkokCAB
Namphong River

Ubolratana Dam

C1CC2C3Do

Khon Kaen
Chi RiverDEFFig. 1 Location of study site in the Mekong River basin NE Thailand (Maps A and B) andsampling sites along the Namphong River (Map C)
Sites A – Ubolratana Dam; B – fish cage (in-river cage aquaculture for Tilapia production); C – pulp/paperindustrial plant (discharge via tributary to main river); sugar industrial plant; C2 cucumber culture; C3 cornculture; Do vegetables culture; D vegetable culture and paddy fields; E vegetables culture; and F –vegetables culture, residential discharge to Chi River just upstream from confluence with Namphong River© ISERD
156

IJERD – International Journal of Environmental and Rural Development (2013) 4-2

RESULTS AND DISCUSSION
Tables 1 and 2 give the water quality data (mean (±sd) of before and after DGT sampling) for the
10 sampling sites along the Namphong River below the Ubolratana dam (Fig.1).
Table 1 Field water quality data (mean of before and after DGT sampling)
pHSampling site
A. Ubolratana
B. River cage Aquaculture
C. Pulp mill
C1. Sugar mill
C2. Cucumber culture
C3. Corn culture
Do. Vegetable culture
D. Vegetable culture
and paddy field
E. Vegetable culture
F. Vegetable culture

Temp
(0C)
23.0
23.0
25.0
25.0
23.0
23.0
25.0

DO(mg/L)
6.28
5.45
5.88
5.29
7.65
7.31
5.46

Sat (%)

7.0
7.0
7.7
7.3
7.4
7.4
7.3

EC(µS/cm)
94
86
1250
97
80
99
102

7.3

106

25.0

5.75

70.5

7.2
7.3

109
110

25.0
25.0

5.54
5.4769.669.7

76.4
62.8
75.1
70.3
91.4
90.1
69.6

Table 2 Water quality data (mean±sd of before and after DGT sampling)
Sampling site
A. Ubolratana
B. River cageaquaculture
C. Pulp mill
C1. Sugar mill
C2. Cucumberculture
C3. Corn culture
Do. Vegetableculture
D. Vegetable culture
and paddy field
E. Vegetable culture
F. Vegetable culture

Hardness(mg/L
CaCO3)
64± 4

DOC(mg/L)

Total N(mg/L)

NO3(mg/L)

46±3

Alkalinity(mg/L
CaCO3)
18±1

2.3

23±4

1.8±0.2

80± 4

47±1

31±1

66± 4

1.926±42.8±0.31790±80
360±20672±752±0131±124±0227± 570± 72.3
3.428±719±8

2.5±0.5
3.1±0.2

107±1047±429±769± 4

1.923±82.9±0.3

80± 051±312±067± 5

1.812±22.0±0.1

133±1955±018±165± 7

1.3

13±2

1.9±0.6120± 055±023±369± 3

3.612±4

3 ±1150±19150±1957±057±030±230±061±13
66± 7

2.9
3.1

12±4
7 ±0

2.2±0.7
2.4±0.1

TS(mg/L)

TDS(mg/L)

53± 2

Generally good water quality was found. The Namphong River water pH (range 7.0-7.4) andhardness (range 64-70 mg/L as CaCO3) were consistent and electrical conductivity showed slightincrease in proceeding downstream, apart from Site C (pulp mill) which was a tributary receiving
discharge to the main river and indicated that groundwater may be used in the processing. Sites Cand C1 also showed that increased total solids in water were associated with these agro-industries.
Nitrate was consistent travelling downstream while dissolved organic carbon (DOC) tended toincrease downstream and total-nitrogen decreased downstream (Table 2). Total and filterable
phosphorus (ranges 0.33 - 0.39 mg/L and 0.03 - 0.05 mg/L respectively, excluding Site C) showedno change from upstream to downstream Namphong River.
The total and filtered (<0.45 µm) concentrations of cadmium, chromium, copper, lead and zincin the Namphong River were measured from before and after sampling and significantly exceeded
the ANZECC/ARMCANZ (2000) the hardness-adjusted trigger values of water quality guidelines(Table 3). However, the concentration of metals estimated from the DGT data were below thehardness-adjusted trigger values (Table 3) and indicated (more accurately) that the labile(bioavailable) metal concentrations in the Namphong River were not significant to freshwater© ISERD
157

IJERD – International Journal of Environmental and Rural Development (2013) 4-2

aquatic biota. The industrial area (Site C - pulp and sugar mills) was a major potential source ofcontamination of the Namphong River associated with increased levels of heavy metals (aluminiumchromium, cobalt, iron and manganese). Confirmation that groundwater was being used in the pulp
mill (Site C) was indicated by the increased total alkalinity, hardness, electrical conductivity(Tables 1 and 2) and the presence of iron and manganese from the total, <0.45 µm filtered andDGT concentration data (Table 3 and Fig. 2). Comparison of the DGT and active sampling (<0.45µm filtered) data for manganese (Fig. 2) at Site C suggested that there was a high short term releaseof manganese into the tributary of the Namphong river during DGT deployment. Active samplingtechnique data (Fig. 2) showed only a slight elevation in manganese concentration as sampling wasundertaken before and after the release.
Table 3 Mean concentrations of heavy metals in Namphong River and trigger values
for 95% level of aquatic species protection (ANZECC/ARMCANZ 2000)
Cmax (µg/L)
DGT conc.

Cmin (µg/L)
Total conc.

0.03
0.2
0.2
1.5
34.3
0.5
3.8

57.9
0.3
58.7
42.2
470.0
64.0
223.0

Cmin (µg/L)
Filtered (0.45 µm)
conc.

MetalCdCoCrCuFePbZn

11.5
0.1
48.0
19.2
77.0
28.0
32.2

Trigger value (µg/L)
95% of aquaticspecies protection(adjusted forhardness)
0.5
ID
2.5
3.5ID
13.6
20.0ID; insufficient data to derive reliable trigger value

300

Mn µg/L

250200150
100500A

BCC1C2C3DoDEFSite
Mn µg/L

Mn Total

Mn <0.45µm

Mn DGT

Fig. 2 Manganese (µg/L) in total, 0.45 µm filtered water fraction by active sampling andpassive DGT technique from the Namphong River
The release of copper, nickel and lead in the Namphong River occurred in the area of rice andmixed vegetable cultivation (Sites Do - F) and was most likely related to extensive pesticide uses
(metals in the pesticides used such as carbamates).
The overall finding is that there is little effect on the water quality of the Namphong River
from upstream to downstream and taking into account of dilution removing observed additions ofsuspended solids and metals from the major agro-industrial activities located upstream. In addition
the Namphong River water is considered safe for human consumption and recreational activities
based on comparison with relevant guidelines.

© ISERD158

IJERD – International Journal of Environmental and Rural Development (2013) 4-2

CONCLUSION
Active and passive sampling methods produce similar trends with results when usedsimultaneously at the same sites. DGTs were shown to be effective for measuring ultra-trace levelsof the labile fraction of heavy metals in water. DGTs offer an extra cost effective and sensitive
method for the independent evaluation of environmental sites. DGTs help to estimate the actuallevels of toxicities of metals under the specific environmental conditions and measure time
integrated average water concentrations of metals over the deployment time where active sampling
represents single points in time. Concentrations of Cd, Cr, Cu, Pb, and Zn in the Namphong Riverby active sampling significantly exceeded the hardness-adjusted ANZECC/ARMCANZ (2000)
trigger value for 95% protection of aquatic species. Concentration of metals estimated from DGTdata were far below the trigger values and indicated more accurately that there were no predicted
toxicity effects on aquatic biota in the Namphong River from dissolved metals. Although theindustrial area (pulp and sugar industries) is a major source of contamination of the NamphongRiver with heavy toxic metals (aluminium, cobalt, chromium, iron and manganese), there issufficient dilution from the Namphong River to give safe levels downstream for protection ofaquatic species. The outcome of this study will help to develop more focused monitoring ofspecific toxic heavy metals at particular locations on the Namphong River.
ACKNOWLEDGEMENTS
The authors wish to thank the Integrated Water Resource Management Research and Develpoment
Center in Northeast Thailand, Khon Kaen University, Thailand for assistance. The Clinical andStatewide Services (CASS), Queensland (Australia) provided financial support of this work andstaff of Inorganic Chemistry Division of QHFSS (Australia) especially Michael Peters and Tetyana
Krasnoff for assistance with sample analyses and data interpretation. Assistance with field work
was provided by Aung Naing Oo, Suraden Chason, and Pantakarn Wanciaen from Khon Kaen
University. Dharawan Noller prepared the figures.
REFERENCESANZECC/ARMCANZ. 2000. Australian water quality guidelines for fresh and marine water quality.
Australian and New Zealand Environment and Conservation Council and Agriculture and Resource
Management Council of Australia and New Zealand. Australia and New Zealand.
Davison, W., Fones, G., Harper, M., Teasdale, P. and Zhang, H. 2000. Chemical analysis and speciation. In:
Situ Monitoring of Aquatic Systems, J. Buffle, G. Horvai (Eds.), John Wiley & Sons, Inc., New York,USA.
Davison, W. and Zhang, H. 1994. In situ speciation measurements of trace components in natural waters
using thin-film gels. Nature, 367, 546-548.
Komarova, T., Olszowy, H., Noller, B. and Golding, G. 2012. The Diffusive gradients in thin films technique(DGT) for trace metals versus active sampling. Int. J. Environ. Rural Devt., 3, 169-174.
Zhang, H. and Davison, W. 1995. Performance characteristics of diffusion gradients in thin films for the insitu measurement of trace metals in aqueous solution. Anal. Chem., 67, 3391 -3400.
Zhang, H. and Davison, W. 2000. Direct in situ measurements of labile inorganic and organically boundmetal species in synthetic solutions and natural waters using diffusive gradients in thin films.
Anal.Chem., 72, 4447-4457.

© ISERD
159