Assessment of dredging influenced sediment toxicity of endosulfan and lindane using black tiger shrimp (Penaeus monodon Fabricius) as an animal model in Chantaburi River Estuary in Thailand | |
| Author | Sumith, Jayakody Arachchige |
| Call Number | AIT Thesis no.EV-07-59 |
| Subject(s) | Endosulfan Shrimps--Effect of sediments on--Thailand--Chantaburi Lindane--Thailand--Chantaburi |
| 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 | Standard elutriate toxicity tests proposed at 1:4 (v/v) of undisturbed sediment be mixed with water from the dredging site has been validated to be used as a conservative predictor of dredging site effects of dissolved chemical concentrations. Series of experiments including background sediment elutriate, spiked-sediment elutriate and spiked-water toxicity tests were carried out to determine if dredging affects survivability and ecological competence of commercially important shrimp postlarvae of Penaeus monodon Fabricius as the surrogate species. The sediment represented for the most contaminated from concerned toxicants (i.e., endosulfan and lindane) obtained from the Chantaburi river mouth estuary where maximum sediment contamination levels of endosulfan and lindane were 32.5 and 37.3 μg/kg sediment (dry weight). The dissolution potential was as low as 0.23% for endosulfan and 1.84% for lindane indicating strong affinity for hydrophobic contaminants in the Chantaburi estuary sediment. Dose-response studies in static, non-renewal tests revealed that NOEC, LOEC and LC50 (96 h) of endosulfan for survival effect in spiked-water toxicity tests based on mean concentrations were 0.536, 1.038 and 1.60 μg/L, respectively. The respective statistical end points (p<0.05) for lindane were 0.617, 1.638 and 3.01 μg/L. The spiked-sediment toxicity tests resulted statistical endpoints for endosulfan and lindane lower than the spiked-water toxicity tests. While LOEC for endosulfan and lindane were 0.141 and 0.429 μg/L, respectively, NOECs were remained to be the simulated sediment plume (=elutriate) concentration levels present in the Chantaburi estuary sediment. The results demonstrated that combined effect of endosulfan and lindane was effectively additive for the survival endpoint represented by mean negative additive indexes of -0.27 and -0.31 within a range that overlapping zero in spiked-water and elutriate tests. The whole body homogenate phenoloxidase enzyme activity was significantly (p<0.05) affected by endosulfan and lindane compared to respective controls. The effects on enzyme activity were biphasic (up-regulation and down-regulation) for individual pesticides in spiked-water tests but the mixture effect was monophasic. It was demonstrated that single exposure to endosulfan decreased enzyme activity by 86% while it was 61% for lindane in low-dose phase. Up to 99% increase of enzyme activity was recorded in higher dose range of endosulfan while it was 51% for lindane. The combination of compounds significantly increased the enzyme activity by 61% of control. Accordingly, NOEC established for endosulfan was 0.274 μg/L while a concentration <0.617 μg/L was estimated for lindane based on the spiked-water tests. Neither enzyme activity in shrimp postlarvae exposed for sub-lethal to lethal doses of same compounds in sediment elutriate were significant (p<0.05) nor biphasic effect was prominent in all tests. Worst case dissolution concentrations of endosulfan and lindane in the water column upon simulatory dredging under the present maximum sediment contamination levels in the Chantaburi estuary are estimated to be 0.075 and 0.686 μg/L, respectively and these levels are sharing same orders of magnitude for NOEC of respective chemicals (i.e., 0.034 and 0.16 μg/L) established for whole salt water aquatic life by the USEPA and “safe” levels calculated by 0.01 safety factor approach. In conclusion, the Chantaburi river estuary sediment can be potentially toxic to shrimp postlarvae on lethal and sub-lethal effects upon dredging at present contamination levels. A multiple pollutant assessment is suggested for elucidating the true impact. The present study further warrants for a range of assays to measure the true impact of immunocompetence and their relationship to the observed up-regulation and down-regulation of phenoloxidase activity |
| Year | 2007 |
| 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 Parkpian; |
| Examination Committee(s) | Visvanathan, C.;Berg, Carl Eric Hakan; |
| Scholarship Donor(s) | Parliamentary Scholarship Board Government of Sri Lanka; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2007 |