Monitoring Pesticides in the Paddy Field Ecosystem of North-Eastern

Chapter 16

Downloaded by UNIV MASSACHUSETTS AMHERST on August 6, 2012 | http://pubs.acs.org Publication Date: September 21, 2007 | doi: 10.1021/bk-2007-0966.ch016

Monitoring Pesticides in the Paddy Field Ecosystem of North-Eastern Thailand for Environmental and Health Risks 1

2

Chuleemas Boonthai Iwai , Hernpak Sujira , Atcharaporn Somparn , Tatiana Komarova , Jochen Mueller , and Barry NoIIer 1

3

3

3

1

Department of Land Resources and Environment, Faculty of Agriculture, Khon Kaen University, Khon Kaen, 40002 Thailand Department of Entomology, Faculty of Agriculture, Khon Kaen University, Khon Kaen, 40002 Thailand National Research Centre for Environmental Toxicology (ENTOX), The University of Queensland, Queensland 4108, Australia

2

3

Contamination of the environment by pesticide application in paddy fields of NE Thailand was characterised by their toxicity to aquatic species, but specific classes of pesticides involved were not identified. Pesticides are dispersed in the environment and move through the food chain and may cause ecotoxicological and human health problems, hence the need for practical management tools. This research aimed at investigating a variety of techniques to screen contamination by pesticides in irrigation waters, and identify compounds that can be related to ecotoxicological effects in the paddy field ecosystem. It showed that pesticides such as desethylatrazine, atrazine, oxadiazon, dicofol,β-endosulfanand its degradation products (lactone and sulfate) are present at some sites. Pollution control authorities can develop monitoring tools for environmental management, to assist in providing sustainable agricultural practices in Thailand.

© 2007 American Chemical Society

In Rational Environmental Management of Agrochemicals; Kennedy, I., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2007.

259

260


Introduction Pesticide contamination associated with paddy field activities may pose significant environmental hazards for terrestrial and aquatic ecosystems. Effects may be observed via biomonitoring with both individual organisms and ecosystem function and structure. Pesticide monitoring is traditionally based on evaluations of individual pesticides identified through chemical analyses. In contrast, the ecotoxicity bioassay approach integrates the biological effects of all compounds present. Biomonitoring and ecotoxicological assessment of pesticides in the paddy field can provide a better indication of environmental effects than chemical analysis. A n integrated approach is needed for pesticide management with paddy field ecosystems taking on board pesticide use and the concept of risk (/). The purpose of risk assessment is to measure the risks and guide the decision making process (2). It is necessary to distinguish relative risk, based on comparisons of different pesticides, and actual risk measured by the exposure, use of exposure data, modeling and field validation (/). Many companies import and sell pesticides in Thailand. A factor that prevents transparent pesticide use and control is trade name proliferation (3, 4). The main pesticides used in paddy fields include monocrotophos (CAS:6923-224), metamidophos (CAS: 10265-92-6), methyl parathion (CAS:298-00-0), methomyl (CAS: 16752-77-5), glyphosate (CAS: 1071-83-6), 2,4-D (CAS:94-757), atrazine (CAS: 1912-24-9), ametryn (CAS:834-12-8) and paraquat (CAS:4685-14-7) (3). The highest risk from pesticide use to aquatic systems was associated with monoculture systems producing marketable crops (5). The aquatic ecosystem is critical for evaluation of the effects of pesticides discharged from the paddy field ecosystem (6). Culture of fish in paddy fields is common; the species Nile tilapia (Oreochromis niloticus) is now found all over Thailand. Fish migrate into paddy fields during flooding, and are harvested when the rice matures. Multiple cropping of rice in much of the tropics exacerbates the problem of discharged irrigation waters. The impact of pesticides on the paddy field ecosystem can be assessed by monitoring commonly found species in the paddy field. A decrease in the population of a susceptible species due to the impact of a given pesticide can decrease species diversity and ultimately change the community structure (7).

Analysis of Environmental Samples from Paddy Fields Integrative sampling is required in order to detect the actual concentrations of pesticides in water. Some currently available approaches are as follows:


261 1.


2.

Collection of a large volume of water, at least 1 L , followed by its concentration present by passage through a pre-filter to remove particulate matter and extraction with the Empore disc polar sampler (8)or by solid phase extraction columns; and Deploying passive sampling or semipermeable membrane devices (SPMDs) at the sampling site held between 1 week and 1 month in the water column to concentrate the pesticides by integrative sampling ( P - 7 7 ) . The SPMDs allow permeation of chemical species < 0 . 1 nm. A more recent version, developed at ENTOX, uses a specific polymeric material, polydimethylsiloxane (PDMS), with the property of permeability to concentrate pesticides in the water column. Concentrations of contaminants sequestered in SPMDs (C PMD) are converted to a water concentration ( C ) using a sampling rate ( R in L d" ), determined in laboratory calibrations ( 7 2 ) using the following equation: S

w

1

s

Cw = CSPMD x MSPMD/RS x t

where M P M D is the mass of the S P M D in grams and t is the sampling time in days. Rs values are available for a wide range of chemicals and can be corrected for water temperature. A n internal calibration method compensates for site specific factors that affect sampler performance. Instrumental analytical methods are required for pesticide analysis of prepared and extracted samples, prior to extensive clean-up procedures. Methods used are as follows: (i) Gas chromatography (GC) e.g. using electron capture detector (EC) for organochlorines; (ii) High performance liquid chromatography (HPLC); (iii) G C / M S ; (iv) L C / M S - M S ; and (v) Enzyme-linked immunosorbent assays (ELISA) (1,13,14). Methods can generally be obtained from the handbooks of the Association of Official Analytical Chemists (AOAC), the British Pharmacopoeia (BP) guidelines, the U S E P A , ISO, A S and other Intergovernmental agencies such as from the OECD, U N E P and E U ( 7 ) . Regardless of choice, all methods require validation of procedures within the local laboratory to demonstrate validity of quality assurance (QA/QC procedures), including use of verifiable standards. The objective of the present study was to investigate the use of a variety of concentrating techniques to screen for pesticide residues in irrigation waters, identify important compounds that are relevant to ecotoxicological effects in the paddy field ecosystem, and to show their association with the presence of aquatic species diversity and type of farming activity. This work will provide the basis for development of an integrated risk assessment approach to improve management of pesticide application in N . E . Thailand paddy fields and indicate if any risks to environment and health exist. S


262

Material and Methods


Sample Sites and Water Quality Samples sites (Table I) were selected at the paddy field ecosystems in N . E . Thailand within 50 km from the city of Khon Kaen, 450 km N E from the capital Bangkok. A l l sampling sites, excepting Site 1, which used groundwater and no synthetic pesticides (botanical pesticide such as Neem extract- Azadiracta siamesis is used), received irrigation waters that were subsequently discharged into tributaries of the Mekong River such as the Mae Nam Phong. This subregion is characterized by the presence of high clay floodplain soils with broad lateritic features giving an overall low organic carbon in sediment (

Monitoring Pesticides in the Paddy Field Ecosystem of North-Eastern

Recommend Documents