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| Titel |
Monitoring and modeling the fate of commonly used pesticides in surface water of the Lower Mekong Delta |
| VerfasserIn |
Pham Van Toan, Zita Sebesvari, Vo Phuong Hong Loan, Fabrice Renaud |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032160
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| Zusammenfassung |
| Introduction: The Lower Mekong Delta, one of the largest agricultural areas in
Southeast Asia, has been reported to be increasingly polluted by agrochemicals
since the beginning of the transformation processes in Vietnamese economy and
specifically in the agricultural sector in 1986 (MRCS, 2007; Dasgupta et al., 2005;
Dung, 2003; Phuong, 2003). Although pesticides have contributed significantly to
enhancing agricultural productivity, these agrochemicals also have created risks
to human health and environment (Margni, 2001; Phuong, 2003; Dasgupta et al.,
2005) and lead to value loss of water resources (Phuong, 2003). While prohibited
persistent organic pollutants such as HCHs and DDTs, were monitored and still
detected in the Lower Mekong Delta in recent studies (Minh et al., 2007, Carvalho
et al., 2008) little data exist on water pollution by recently used pesticides in the
Delta.
Aiming to fill this information gap, a study comprising three components was set up
at two study sites of the Delta. Pesticide use and management was investigated
through surveys and participatory rural appraisals with farmers; pesticide residue
concentrations were determined in field outflows, connected irrigation canals and in
drinking water and finally pesticide fate was predicted by using a coupled MIKE 11/
MIKE SHE model. This abstract focuses on the work done in the field of pesticide
monitoring.
The western study site (An Long Commune, Dong Thap province) represented an
agricultural pattern with two intensive paddy rice crops per year and was heavily affected by
flood in the rainy season. The second site located in the central part of the Delta (Ba Lang
ward, Can Tho City) was characterized by a mix of paddy rice, vegetables and fruit trees.
Fifteen pesticide compounds (buprofezin, butachlor, cypermethrin, difenozonazol,
α-endosulfan, β-endosulfan, endosulfan-sulfate, fenobucarb, fipronil, hexaconazol,
isoprothiolane, pretilachlor, profenofos, propanil, and propiconazol) were monitored
systematically from August 2008 to August 2009.
Methods: Water samples (0.5 L) were collected in borosilicate bottles with
Teflon caps, pre-filtered with glass wool (Roth, Germany) and glass fibre filter
(Millipore, USA), solid-phase extracted (Phenomenex, C18-E) and quantified using
GC-MS (Agilent 6890). For quality assurance samples and blanks were spiked with
a surrogate standard (d-HCH). The recovery of the surrogate standard was used
to monitor for matrix effects and sample processing errors. Surrogate recovery
was evaluated by a recovery standard (Fluoren-d10) spiked to the sample after the
extraction.
Results: A total of 434 samples (253 samples in Ba Lang, 119 samples in An Long and
62 drinking water samples) were collected from August 2008 to August 2009. In An Long 13
of the 15 target compounds were detected in water samples. Average residue concentrations
ranged from 0.01 to 3.96 μg/l. The fungicide isoprothiolane and the insecticide
buprofezin occurred with the highest concentrations (up to 20.77 and 16.53 μg/l,
respectively). In Ba Lang, 12 of the 15 monitored pesticides were detected with an average
concentration from 0.01 to 0.30 μg/l. The fungicide isoprothiolane was detected
with highest (up to 12.86 μg/l). In 70% of all samples more than four different
pesticides were detected. Their effect may add up and pose risk to humans and aquatic
organisms.
In rural areas surface water is frequently used as drinking water source. First
results from a sampling program of drinking water indicate that locally used water
treatment methods (precipitation with aluminium sulfate followed by boiling) were not
appropriate to reduce the pesticide exposure of the consumer. Through evaporation,
boiling of drinking water even increased the concentrations of some non-volatile
pesticides.
References
Carvalho, F. P., Villeneuve, J.P., Cattini, C., Tolosa, I., Thuan, D. D., Nhan, D. D., 2008.
Agrochemical and polychlorobyphenyl (PCB) residues in the Mekong River delta, Vietnam.
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Dasgupta S., Meisner C., Wheeler D., Nhan L. T., Khuc X., 2005. Pesticide poisoning of
farm workers: implications of blood test results from Vietnam. World Bank Policy Research
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Dung, N.H., Dung, T.T., 2003. Economic and health consequences of pesticide use in
paddy production in the Mekong Delta, Vietnam. Economy and environment case studies in
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Margni, M., Rossier, D., Crettaz, P., Jolliet, O., 2002. Life cycle impact assessment of
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