A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Inter {u2013} University Pro gram on Environmental Toxicology, Technology and Management

Thesis (M.Sc.) - Asian Institute of Technology, Chulabhorn Research Institute and Mahidol University, 2010

Glyphosate and paraquat are herbicides which are widely used in agricultural activities especially in crops cultivation. Degradation of paraquat in environment is very slow and has possibilities of transportation to other place by vectors like wind or water during degradation processes. Moreover, these herbicides{u201F} translocations are critical in Thailand because of the favorable local climate and the majority of Thai populations are farmers. Agricultural area mostly located near the water resources especially flow water resources like rivers. In addition, rain is one of the common climatic events in tropical zone. As a consequence of these two co-existences, the pesticides on farmland have high chance to move from one place to other via the soil surface wash-off and the flow of water resources. Thus, vetiver grass which used as green barrier to prevent soil erosion and surface wash-off has taken part in to prevent this transportation to happen. The experiment in greenhouse was set up to determine the effects of chemicals which were glyphosate, paraquat, and nanoscale zero-valent iron (nZVI) on growth of Vetiveria nemoralis. The results showed that glyphosate has negative effects on V. nemoralis growth in length of root and formation of secondary cell wall in the root while paraquat has shown its effect on induction of secondary cell wall formation. However, nZVI at selected dose, 1g/kg soil, has beneficial effects on vetiver grass growth and helps in paraquat reduction. The reduction of glyphosate and paraquat contents in soils was set up with 12 weeks of the observation period. The highest percentage of glyphosate removal was found in treatment of paraquat with glyphosate and V. nemoralis combination while the combination of paraquat with nZVI, V. nemoralis showed the highest paraquat removal at 85.71% and 56.38% at week 12, respectively. Moreover ,the accumulation of glyphosate was found in the shoot while paraquat was accumulated in the root of V. nemoralis. Uptake of plant nutrients like iron, copper, zinc, and manganese by V. nemoralis were monitored. The results showed that most elements accumulate in root more than shoot. However, the uptake of these elements was decreased by glyphosate application. In field study vetiver grass were used for run-off prevention, the areas which were planted with Vetiveria zizanioides had glyphosate and paraquat residues in soil less than soil on the bare land at the same distance. The efficiency of vetiver strips on the reduction of glyphosate in the soil was found after the second strip while paraquat reduction was found after the third strip. Both greenhouse and field studies suggest that selected vetiver grass should be useful for reducing the run-off of these pesticides from agricultural area into the natural water resources.