Potential impacts derived from herbicide accumulation in the Pak Phanang Bay, Nakhon Si Thammarat Province, Thailand | |
| Author | Damrongsak Noicharoen |
| Call Number | AIT Diss. no.EV-12-04 |
| Subject(s) | Paraquat--Environmental aspects--Thailand--Nakhon Si Thammarat Glyphosate--Environmental aspects--Thailand--Nakhon Si Thammarat Herbicides--Environmental aspects--Thailand--Nakhon Si Thammarat |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-12-04 |
| Abstract | Herbicide is commonly used in agricultural activities to control weed and maintain productivity. Two of the most widely used herbicides in the world, in sediment of Pak Phanang River Basin, Thailand, glyphosate (N-(phosp honomethyl)glycine) and paraquat (1, 1’-dimethyl-4, 4’-dipyridyliumdichloride). When the contaminated soil become eroded and transported to fresh water ecosystem, harmful effects to aquatic environment may be less, because glyphosate and paraquat are rapidly and tightly bounded with clay minerals and organic materials which suspension in water body and sinking into bottom sediment. In contrast, resuspension of the sediment contamina ted by herbicides or changing environment factor especially salinity, in the over lying water as well as sediment itself might become biologically active or toxic to aquatic species again. Batch experiments were conducted to study the effect of salinity gradient (0-20 ppt) on adsorption and desorption of two herbicides in sediment of Pak Phanang River Basin. Sediments from five locations were used in the studies (two from freshwater sites and three sites under saline environment). The paraquat adsorption capacity (Kf) of the sediments was positively correlated with CEC (r=0.81 ∗∗ ) and clay content (r=0.70 ∗ ). Paraquat adsorption by sediment was faster under fresh water (0 ppt) versus saline conditions (10 and 20 ppt). The adsorption coefficient (Kf) at low salinity (0 ppt) was 17,302 whereas the Kf at 10 and 20 ppt were 5,344 and 4,263, respectively. Paraquat desorption was greater at higher salinity, which is similar to the salinity of estuarine or seawater. Approximately 12– 31 % of sorbed paraquat in fresh water and saline sediment (7.67 and 7.98 mg/kg) were released when leaching with 20 ppt salinity. The amount of paraquat released was in proportion to the amount sorbed. Results show that increases in salinity resulting from salt water intrusion from the lower estuary into the Pak Phanang River Basin would result in release of adsorbed paraquat from sediment into the water column. Contrary, glyphosate adsorption capacity (Kf) of the sediments was positively correlated with OC(r=0.867*). The intensity factor (1/n) has a positive relationship to pH(r=0.879*) and sample station (r=0.915*). Glyphosate adsorption rate was faster in saline water sediment than in the fresh water sediment, opposing to paraquat. Glyphosate desorption is very low, less than one percent in all experiments. Data in desorption expe riment shows that the desorption coefficient (Kdes) is very high. As a result, it is not released or dissolubilized in to overlying water again. Then, the potential risk from bounded glyphosate sediment could be neglect and not play attention to concerned in normal condition. The concentration of paraquat in freshwater environment of the study site is 8.028 μ g/L higher than EC 50 (0.55 μ g/L) which is the safe toxicity level for freshwater diatom. This supported by the HQ value of 14.596, more than 1.0 indicate unacceptable risk to freshwater diatom. But, in comparison with the screening toxicology value of paraquat for drinking water follow US. National Drinking Water Standards and Health Criteria (Oregon, 2003), IPCS Inchem (1986) and Drinking water Standards and Criteria of England and Canada, then the Hazard Quotient (HQ) is less than 1.0. Glyphosate concentration in fresh water column found the highest value at 4.141 μ g/L (or ppb) on the bottom level of station FW-4B on December 2008. The screening ecotoxicology value (SEV) of glyphosate for drinking water follow National Primary Drinking Water Regulations, US-EPA (2006) at the rate of 700 ppb, then the Hazard Quotient (HQ) value can be calculated and the result shown that HQ value is less than 1.0. Indicating water in Pak Phanang River is safe from glyphosate and paraquat for drinking or using as tab water production |
| Year | 2012 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-12-04 |
| Type | Dissertation |
| 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) | Shipin, Oleg ;Preeda Parkpian (Co-Chairperson) |
| Examination Committee(s) | hongrak Polprasert ;Gallardo, Wenresti |
| Scholarship Donor(s) | National Science and Technology Development Agency (NSTDA), Thailand |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2012 |