IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Research article
erd

Pesticide Distribution in the Namphong River NE Thailand
Arising from Land Use and Other Practices
TATIANA KOMAROVA*
Queensland Health Forensic and Scientific Services (QHFSS), Coopers Plains, Brisbane,
Australia
Email: Tatiana_Komarova@health.qld.gov.au

CHULEEMAS BOONTHAI IWAI
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

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

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

JOCHEN MUELLER
National Research Centre for Environmental Toxicology (Entox),
The University of Queensland,Coopers Plains, Brisbane,Australia

IVAN KENNEDY
Faculty of Agriculture and Environment, University of Sydney, Australia

BARRY NOLLER
Centre for Mined Land Rehabilitation (CMLR), Sustainable Minerals Institute,
The University of Queensland, Brisbane, Australia
Received 11 February 2015

Accepted 31 May 2015(*Corressponding author)

Abstract Large quantities of pesticides and herbicides are used in the Namphong River
catchment, NE Thailand for protection of crops and agro industrial production. The aim of
this study was to screen pesticides in waters of the Namphong River from in-situ riveraquaculture, surface runoff and agro industrial discharges to identify if pesticide levels posesignificant risk to the aquatic ecosystem. A passive sampling technique was used toestimate the level of pesticides in the river water. Pesticides were accumulated onpolydimethyl siloxane (PDMS) strip passive samplers during 29 days deployment inJanuary-February 2012, and then sent to Australia for analysis of pesticides at the
University of Queensland and Queensland Health Laboratories. The PDMS passive
samplers were deployed at 5 sites in the Namphong River from below the Ubonratana Dam,the tributary downstream of the paper mill and vegetable and paddy fields down to the Chi
River above the junction of Namphong River. Atrazine, ametryn, chlorpyrifos andoxadiazon were found at all sites at elevated levels associated with vegetable and paddy
field areas indicating their extensive application. Terbuthylazine, terbuphos and phosphate
tri-n-butyl were found only in the paper mill discharge. Traces of galaxolide were found at
all sites but only in significant amounts (30 times higher) just below the paper mill.
Comparison of pesticides between the present and an earlier 2005 study of the paddy fieldecosystem 50 km N from Khon Kaen show a shift from organochlorine use to low
persistence pesticides, particularly chlorpyrifos. The results confirm that a range ofpesticides are being used in the Namphong river catchment able to be detected downstream,
though at low levels. These data provide a baseline, showing the need exists for more
systematic and complex assessment of the catchment to develop a tool for pollution control
in the catchment and to identify major sources of contamination and for ongoingenvironmental risk management.
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Keywords pesticides, herbicides, passive sampling, land use practices, environmental risk
management

INTRODUCTION
The Namphong River in the NE part of Thailand is within a sub-catchment of the Mekong River(Fig. 1). The Namphong River flows to the Chi River and via the Mun River to the Mekong River.
Below Ubolratana Dam, there are extensive agro-industry and farming activities along theNamphong River which use irrigation from dam storage and some supplementary groundwatersupply. Pesticides and herbicides from agro-industry activities are identified as potential risks tohuman health and the environment and as significant pollutants (Somparn et al., 2014). Of all
pesticides in use, chlorpyrifos was identified as the highest volume of insecticide importation in
Thailand (Department of Agriculture, 2012). The aquatic ecosystem of the Namphong River is a
critical aspect for the evaluation of the effects of pesticides dispersed in the environment.
Ecotoxicological effects from pesticides on aquatic organisms may be observed via biomonitoringwith both individual organisms and ecosystem function and structure. The Namphong River also
supports extensive cage aquaculture which may be affected by pesticides. In 2010, 209 cages
produced 1536 tonnes of Nile tilapia in Khon Kaen province (Department of Fisheries, 2010).
Key questions are: (i) what are the effects of pesticides in the Namphong River?; and (ii) theirrelationships to other water quality parameters associated with agro-industry and farming activities.
The prevailing tropical wet and dry seasons cause variation in river flow. The addition, ofparticulate and organic matter from soil transferred directly to river water can absorb pesticides.
Potential effects are therefore possible from pesticides added to river water during the annual cyclethat may arise from agricultural, aquaculture and other urban discharges from Khon Kaen city.
OBJECTIVE
This study aims to identify if pesticides and herbicides from multiple agro-based activities
comprising agro-industry and small-scale farming activities along the Namphong River, areenvironmental and health risks, causing any impact to the Namphong River water body at different
sample locations, and compares data from the 2012 dry season with existing data and criteria.
METHODOLOGY
Pesticides and herbicides were accumulated on polydimethylsiloxane (PDMS) strip passive
samplers during 19 January-23 February 2012 at 5 sites at the Namphong River from below the
Ubonratana Dam, the tributary downstream of the paper mill and vegetable and paddy fields down
to the Chi River above the junction of Namphong River (Fig. 1). Site C is on a small tributary lessthan a few km to the Namphong River from the pulp and paper mill (Fig. 1C). Prior to applicationeach PDMS sampler (strips 2.5 cm x 92 cm and thickness about 400 µm) was cleaned on ahorizontal shaker in fresh redistilled hexane for three consecutive 24 h periods at the pesticide
analytical laboratory followed by drying under high purity nitrogen gas steam, wrapping in acetone
rinsed aluminium foil and stored in the refrigerator until dispatched to Khon Kaen. The PDMS
samplers were placed under water at a depth of 0.50 m and left in place for 29 days. Following
collection, the PDMS samplers were placed in pre-cleaned acetone rinsed aluminium foil envelopes
and kept refrigerated until dispatched with quarantine clearance details from Khon Kaen toAustralia for sample processing and analysis using the routine procedures of Queensland HealthOrganic Chemistry Laboratory. Prior to PDMS extraction in hexane and following instrumental
analysis each of them was cleaned by scrubbing with water, dipping in redistilled hexane for 30
seconds and 0.5M HCL for 20 seconds followed by rinsing with acetone and isopropanol. Water
quality measured using standard techniques described (Komarova et al., 2012, 2013).
Passive samplers using polydimethylsiloxane are low cost and have an improved affinity forⒸ ISERD

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polar compounds relative to other samplers (Rusina et al., 2007). Comparative studies (Shaw et al.,2010) showed that PDMS samplers accumulated a larger number of compounds with log Kow 2.9
to 6.4 dissolved in water. At log Kow of 4.7 (chlorpyrifos) and 4.27 (trifluralin) the mass captured
was 6 times higher in PDMS compared with other samplers with the same surface area.

Fig. 1 Location of study site in the Mekong River basin NE Thailand (Maps A and B)
and sampling sites along the Namphong River (Map C)[Sites A – Ubolratana Dam; B – fish cage (in-river cage aquaculture for Tilapia production); C – pulp/paper industrial
plant (discharge via small tributary to main river); sugar industrial plant; C2 cucumber culture; C3 corn culture; Dovegetables 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]

Well developed and validated procedures are used at all steps of PDMS passive sampler
application (Shaw, 2005). The mass of contaminants accumulated in a PDMS sampler are
converted to their concentrations in water (Cw, ng/L) using a sampling rate (Rs in Ld-1) that is
estimated for different pesticides at different environmental conditions in laboratory calibration
study (Huckins et al., 2002) by Eq. 1.
Cw = MPDMS / Rs t

(1)

where MPDMS is the mass of a pesticide found in the PDMS sampler after deployment (ng) and t isthe deployment time in days. Method detection limits are calculated from the lowest mass per
sampler detected on analytical equipment (LCMS, GCMS) and the respective compound sampling
rate (e.g. <50 ng/mL for the extracted volume in the laboratory and 0.001 ng/L for chlorpyrifos in
PDMS samplers for 29 day deployment). These detection limits are an order of magnitude lower
than reported for pesticide concentrations using grab sampling techniques (Shaw, 2005). The
linearity of the relationship between log Kow and sampler to water partition coefficients has been
demonstrated over a wide range of compounds for PDMS (Yates et al., 2007).
Following preparation, extraction of samples and extensive clean-up procedures using size
exclusion chromatography, pesticide and herbicide are analysed by different instrumental analyticalmethods: these are gas chromatography (GC), high performance liquid chromatography (HPLC),
GC/MS and LC/MS-MS undertaken in the Queensland Health NATA accredited laboratory(according to ISO 17025) and based on USEPA Method EPA 503/6-90-004. All standards (3external standards) and samples are spiked with an internal standard just prior to analysis.

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RESULTS AND DISCUSSION
Table 1 gives the pesticide and herbicide concentrations that have the highest inputs for effluent at
Site C (Paper Mill) when compared with Table 2. Galaxolide, terbuthylazine, phosphate tri-n-butyl,
tonalid and terbutryn are added in paper mill effluent (Table 1) but only galaxolide remains
detectable at much lower concentration (1:35) showing dilution down to Site F at the Chi River;
tonalid is diluted 1:10 at Site C3 (Fig. 1C) but is then undetectable downstream.
Table 1 Pesticide and herbicide concentrations for 19-23 January 2012 showing Site C (Paper
Mill) effluent with highest input (average of 2 PDMSs per site)
Sampling site

Galaxolidea

Terbuthylazine

A. Ubolratana (ng/L)

0.201<0.001

Terbuphos<0.001

Phosphate
Tri-n-Butyl

Tonalid

Terbutryn<0.001<0.001

0.069

C. Pulp mill (ng/L)
26.8
3.1
1.1
0.18
0.17
0.34
C3. Corn (ng/L)
0.68<0.001<0.001<0.001
0.017<0.001
D. Vegetable/ paddy<0.0010.81<0.001<0.001<0.001<0.001
field (ng/L)
F. Vegetable (ng/L)
0.89<0.001<0.001<0.001<0.001<0.001
Guideline or acute toxicity
Algae, protozoa
LC50 (ng/L)
3.2-100 x 106(WHO, 1991)
Fish LC50 (ng/L)
2340 – 20000
0.8 – 10.0 x
0.16-90 x 106(PAN, 2014)
106
Fish LC50 (ng/L)
0.318 x(PFW Aroma
106
Chemicals, 2007)
Note: a. Not toxic to aquatic species, with low toxicity to terrestrial species [Rat Acute: >5000 mg/kg rat (Spectrum,2009)]

Table 2 gives the pesticide and herbicide concentrations for all sites upstream or lower
downstream; i.e. below Site C2. Ametryn, oxadiazon, chlorpyrifos, prometryn and atrazine are all
found at measureable concentrations at Site A below Ubonratana Dam (Fig. 1C) indicating thatapplication of these pesticides and herbicides has occurred in the upper Namphong River
catchment above Ubonratana dam and contribute to the downstream river load. Fig. 1 shows thatabout 60% of the Namphong River catchment is associated with the two branches above
Ubonratana dam. At Site C3 (Fig. 1C), ametryn, oxadiazon, chlorpyrifos, prometryn and atrazine
all show increased or similar concentrations indicating extensive insect and weed control fromagricultural activities in the upper Namphong catchment. The trend continues at Sites D and F withsignificant (2-7 times) increases in concentrations of ametryn, oxadiazon, chlorpyrifos, prometryn
and atrazine in river water (Table 2) where the observed levels of pesticides and herbicides areassociated with vegetable and paddy field areas indicating their extensive application. At Site D(Fig. 1C) the application of trifluralin is observed, indicating a particular crop application, but wasthen undetectable at Site F (Table 2).
The comparison of measured concentrations of pesticides and herbicides for all sites in Tables
1 and 2 with compiled details of guidelines and LC50 values for fish and other freshwater species
shows that all compounds are well below concentrations that will induce a toxic response. While allcompounds excepting chlorpyrifos are present at exceedingly low concentrations, chlorpyrifos isonly 10-20 times lower than the validated Australian aquatic guideline (Table 2 – note no Thai
guideline available). The application of chlorpyrifos is associated with insect control of vegetableand paddy field areas in line with the highest volume of insecticide importation in Thailand cited
above (Department of Agriculture, 2012). The pesticides and herbicides that were detected at the
sampling sites of the Namphong River in January 2012 are all low persistent compounds andindicate recent applications. Comparison of the observed pesticides and herbicides identified in thisstudy with an earlier 2005 study of paddy fields, horticulture and vegetable farming in theⒸ ISERD

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Namphong River basin sediment, water samples and PDMS samplers (Boonthai-Iwai et al., 2007)
showed that the pesticides and herbicides in use at that time included atrazine, oxadiazon and theorganochlorines dicofol and endosulfan; comparison with Tables 1 and 2 levels shows there was nodetection of organochlorines in 2012 but that chlorpyrifos is used extensively together with a rangeof herbicides. If the application rate of chlorpyrifos increases, the level in Namphong River may
increase and exceed the threshold of toxicity for fish and be a threat to cage aquaculture. Thus there
needs to be a more systematic and complex assessment of chlorpyrifos in the Namphong Riverbasin to develop a tool for its control and environmental risk management.
Table 2 Pesticide and herbicide concentrations for 19-23 January 2012 showing inputs at allsites upstream or below site C downstream (average of 2 PDMSs per site)
Sampling site

AmetrynOxadiazon

Chlorpyrifos

Prometryn

Atrazine

Trifluralin

A. Ubolratana (ng/L)

2.6

0.46

0.061

0.23

0.10

<0.001

C. Pulp mill (ng/L)
C3. Corn (ng/L)
D. Vegetable/ paddy field(ng/L)
F. Vegetable (ng/L)

0.12
1.7

0.75
1.0

<0.001
0.14

0.10
0.29

<0.001<0.001

2.7

6.7

0.24
0.45
0.79

0.30

0.40

0.062

0.28

0.40

0.18

-

13000

4400

-

-

-

2.5 – 10.0 x
106

-

-

95% protection aquatic
freshwater species(ANZECC/ARMCANZ,
2000) (ng/L)
Nile tilapia LC50 (ng/L)(PAN, 2014)
Fish LC50 (ng/L)(EXTOXNET, 2014a,b)

2.6

7.2
0.88
Guideline or acute toxicity

-

-

-

60000

3.2 – 8.8 x
106

-

10
-

CONCLUSION
This paper identified that the Namphong River basin can absorb current inputs of pesticides andherbicides that arise from the agro-based activities and is not causing any impact to the water
quality in the Namphong River itself. Measured pesticides and herbicides except chlorpyrifos were
present at exceedingly low concentrations in Namphong river water. However chlorpyrifos is only
10-20 times lower than the Australian aquatic guideline (noting no Thai guideline) for protection of
aquatic species and was identified as the highest volume of insecticide importation in Thailand. If
the application rate of chlorpyrifos is increased, the level in Namphong River may increase andexceed the threshold of toxicity for fish and other species and be a threat to cage aquaculture.
Although there does not appear to be a current contamination problem there is a potential issue
with chlorpyrifos in water which is identified as having higher risk and requiring further data andinformation. Thus there needs to be a more systematic and complex assessment of chlorpyrifos in
the Namphong River basin to develop a tool for its control and environmental risk management.
ACKNOWLEDGEMENTS
The authors wish to thank the Integrated Water Resource Management Research and Development
Center in Northeast Thailand, Khon Kaen University, Thailand. We thank Clinical and Statewide
Services (CASS), Queensland (Australia) for the financial support and staff of Inorganic Chemistry
Division of QHFSS (Australia) for assistance with sample analyses and data interpretation. Aung
Naing Oo, Suraden Chason, and Pantakarn Wanciaen from Khon Kaen University assisted withfield work. Entox is a partnership between Queensland Health and the University of Queensland.
Dharawan Noller prepared the maps.

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