Potential bioavailability of POPs in lake sediment under tropical conditions : a case study of Mae Thang Reservoir, Northern Thailand | |
| Author | Pannawee Mekwichai |
| Call Number | AIT Thesis no.EV-08-46 |
| Subject(s) | Persistent pollutants--Thailand--Mae Thang Reservoir Lake sediments--Thailand--Mae Thang Reservoir |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | The contamination levels of Persistent Organic Pollutants (POPs) were measured in sediment samples that collected from four locations along the Mae Thang reservoir, Northern part of Thailand during dry season (November) in 2007. Soxhlet extraction technique was used for sediment extraction, and gas chromatography with electron capture detector (GC-ECD) was applied for pesticides determination. Results of total pesticide concentrations at each location showed that the concentrations of total endosulfan in sediment (0-35 cm) were highest at only one location (130.67 μg/kg) which near outlet of the dam while total hexachlorocyclohexane (HCH) were high at all locations. The chemical properties of sediment such as pH, cation exchange capacity (CEC) and organic matter (OM) at those locations were not showed positive correlation with total pesticide concentrations. This indicated that the difference in concentrations of total pesticide was not related with sediment properties due in part to quite low concentrations of pesticides accumulated in the sediments. According to distribution of pesticide in the sediments cores, HCH was predominated in different those depths in the sediment that divided into two forms, αHCH (62.04-134.81 μg/kg) and γHCH (4.21-21.63 μg/kg) following by total endosulfan (non detectable-2.48 μg/kg) and heptachlor (0.81-4.43 μg/kg). For the relationships determined between total pesticide concentrations with sediment depth and total organic carbon (TOC), the finding suggested that heptachlor was correlated with TOC (r=0.466) whereas αHCH and γHCH were expressed correlation with sediment depth. Such expression was increased with increasing depths. This might have been due to eroded particles carry with them the mixed pesticides (heptachlor and HCH) were deposited into the lake corresponding with run off and sedimentation time. Thus organic carbon in the sediment serves as sink or binding material for such pesticides. The low density polyethylene (LDPE) and pore water methods were tested to extract bioavailable fractions of POPs pesticides from the sediments. Results used to determine bioavailability pesticide fraction. The result showed that LDPE pellets could remove higher concentrations of endosulfan around 1 to 2 times over the pore water method with the values of 2.87 μg/kg and 0.34 μg/kg, respectively. Besides, heptachlor and HCH were also removed by two methods. In addition, the sediment extracts were assessed for environmental risk using hazard quotient (HQ) with Thailand, Canada and Netherlands benchmarks through LDPE method. The results suggested that potential were acceptable risks when LDPE extract were used as the adsorbent. The HQ value of pore water method was applied with EPA, WHO and Australian standards. The results illustrated that potential were unacceptable risk which may cause harmful effect on aquatic species. |
| 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) | Chongrak Polprasert;Annachhatre, Ajit P.; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2008 |