Herbicide application and environmental pollution in peri-urban of Vientiane, Lao PDR | |
| Author | Somsanith Duangpaseuth |
| Call Number | AIT Thesis no.EV-08-33 |
| Subject(s) | Herbicides--Application--Laos--Vientiane Herbicides--Environmental aspects--Laos--Vientiane Pollution--Laos--Vientiane |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master Science in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Paraquat is known as non-selective contact herbicide that used for destroys green plant tissue in upland agriculture, included weed control before sowing or before crop emergence, pasture renovation, pre-harvest desiccation and aquatic weed control. It is quickly and strongly adsorbed by soil particles, especially in clay soil and disappears rapidly from water by binding onto aquatic weeds. It is also damage on plant tissue take place rapidly at the green plants. It may occur with an hour after applying the herbicides in sunny condition, then followed within 24 hour by wilting of leaves and later till by desiccation. So the aims of this study were to study a general overview of herbicides management in Lao PDR based on secondary data, to investigate the distribution of herbicide in a selected area by measuring the herbicide (paraquat) residue levels in water, sediment and soil. The selected study area was carried out in Vientiane capital city, includes Xiengda village, Saysettha district, which are the intensive area for agriculture to supply vegetables to the main market in Vientiane capital. Soil samples from 3 farms were collected from the study area, two farms used concentration of paraquat following by recommended label rate, but for another farm did not use paraquat for control weed was meaning that free of paraquat concentration. Sediment and water samples were selected in That Luang marshland, Hong Xeng stream and Houay Mak Hiao river. Paraquat in all samples was analyzed by 396 nm wavelength using a Hitachi U-2001 VIA / UV Spectrophotometer model at environmental engineering laboratory of AIT. From the experiment of this study, no paraquat accumulated in water samples at That Luang marshland, it was found for sediment samples trace amounts that were measured, and concentration of paraquat in the rainy season was higher than the dry season. Zone 1 which is located near That Luang marshland was found high paraquat accumulation follow by zone 3 which received drainages from canals running throughout Vientiane. In data from farm tests (routine application rates), done on three farm in this study( A, B and C), farm A & B used paraquat for weed control but farm C for no paraquat control weed. The data from farm A & B shows that depletion of paraquat in vegetable soils was approximately 3-4 weeks as indicating by its half-life. Possible processes to degrade the chemical are mainly by biological; photo-degradation was soil adsorption. Overall, it can be concluded that the DT50 of paraquat in soil in this study area is approximately 3-4 weeks. By the detection method used it proved impossible to detect any significant levels of paraquat in water. This appears to indicate that it is either present in an extremely low concentration, diluted with water, completely degraded microbiologically and probably removed from water table through setting clay adsorption. |
| Year | 2008 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Preeda Pakpian; |
| Examination Committee(s) | Nguyen, Thi Kim Oanh;Shipin, Oleg V.; |
| Scholarship Donor(s) | Sweden (Sida); |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2008 |