| Author | Anchalee Pradidwongkool |
| Call Number | AIT Thesis no.EV-04-02 |
| Subject(s) | Pesticides--Environmental aspects--Thailand--Pathum Thani
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, Asian Institute and Technology; Inter-University Program on Environmental Toxicology, Technology and Management, Chulabhorn Research Institute and Mah idol University |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-04-02 |
| Abstract | A sub-district of Nong Seao district was selected area for this study. The current main
commercial crops in this flat intensely irrigated area were identified to be long beans,
com, cucumbers and, to a much lower extent, tangerines (previously dominant crop item).
It was found in the present study that a recent crop diversification necessitated application
of various new pesticides. These were carbosulfan, methomyl, tetradifon, malathion,
abamectin, EPN (insecticdes), zineb (fungicide) and herbicides: glyphosate, atrazine and
paraquat. It was found that most farmers correctly think that pesticides may contaminate
environment and accumulate in soil reducing soil quality and result in pesticide residuals
in products (65%). However, due to economical reasons the conventional chemical
pesticides will still be used extensively in the foreseeable future. Therefore new ways of
mitigation of their detrimental impact were to be investigated as a high priority issue.
Natural Treatment Systems (NTS) due to their low cost and low tech nature were found to
be promising alternative options for the local mitigation of the impact of pesticides. The
research showed that the main types of NTS were farm irrigation canals (94 %), paddy
fields (5 %) and, to a much lesser degree, ponds (1 %). Overall these systems comprise a
formidable area of 59,848 ha (374,050 rai) or 74 % of total agricultural area of the
province. It was shown that due to a hydraulic regime of the fields the farm irrigation
canals (as well as paddy fields) could be effectively considered as already functioning
natural treatment systems which due to their large area effectively mitigate impacts of
agricultural runoff. This was further confirmed by the field study of the degradation of
paraquat, one of the main locally used herbicides. The data from the plot with producerrecommended
application dose applied specifically for the experiment and the 2 plot with
elevated dose applied shows that DT5o of paraquat in top soil in the former plot (6 days) is
lower than in the latter 2 plot (10 days). Though different, they fall into the same time
range (1-1.5 weeks). In terms of the degradation rate, the former plot had a sharper curve
than the latter due to the first order reaction. In the other set of tests (routine application
rates), done on three farms in the study area (A, B and C) the data shows that average
DT 50 of paraquat in top soil at routine application rates practiced by farmers was 3 weeks.
It appears from the kinetics of the degradation that the main mechanism for the
degradation is photodegradation. Overall, it can be concluded that the DT 50 of paraquat in
soil in the study area (tropical climate) is approximately 1-3 weeks. The fact that the
paraquat concentration in the farm irrigation canal sediments was found to be at the
background level concentration of the study area 0.8 ppm (mg/kg) appears to demonstrate
that biodegradation, albeit known to be very slow, does play a role in the long run. By the
detection method used it proved impossible to detect any significant levels of paraquat in
water of the farm irrigation canals. This appears to indicate that it is either present in an
extremely low concentration, diluted with water, completely degraded microbiologically
or, most probably, removed from water table through settling clay adsorption. Therefore at
least in this respect the water in farm irrigation canals is reasonably safe. |
| Year | 2004 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. EV-04-02 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Shipin, Oleg V.; |
| Examination Committee(s) | Preeda Parkpian;Skorn Mongkolsuk;
Thammarat Koottatep; |
| Scholarship Donor(s) | Royal Thai Government;
Chulabhorn Research Institute;
Mahidol university;
Asian Institute of Technology
(RTG-CRI-MU-AIT); |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2004 |