| Author | Phanit Ratasuk |
| Call Number | AIT DISS. no. EV-03-04 |
| Subject(s) | Copper--Toxicity testing--Thailand--Samut Prakan
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| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science. Inter-University Program on Environmental Toxicology, Technology and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Uncontrolled discharge of industrial and domestic wastewater to the Samut Prakam coastal area was reported, resulted in the sediment being contaminated. This study aims to provide better understanding on transportation and transformation of copper in sediment-water ecosystem of Samut Prakam coastal area in order to evaluate its potential risk to aquatic organism or induce toxic effects. The research framework was designed to cover both field survey for sediment and seawater sampling and laboratory experiment focusing on copper fractionation using a sequential extraction procedure and adsorption-desorption phenomena. In addition, effect of copper on the metallothionein induction in mussel was studied in an attempt to evaluate the potential usefulness of the metallothionein induction as a biomarker of exposure. Copper in coastal water was found primarily in particulate form range from 22.6-60.2 mg/kg in dry season and increased in wet season range from 24.6-189.3 mg/kg. This was probably due to the fine-grained river-borne particles in wet season having higher ability in absorbing copper in comparison with coarse mineralized particle in dry season. Therefore we expect less copper toxicity in this area due mainly to predominant copper in particulate form, the not readily-bioavailable fraction. Sediment profiles of the studied area were collected using soil column technique. Each column was divided into different depth increments. All the sediment samples were then analyzed chemically and physically. The overall characteristics of sediment in this area were classified as medium to high in CEC, rich in organic matter and has the sediment texture as clay. Copper concentrations found in the sediment ranged between 1.21-54 mg/kg with value higher than 30 mg/kg in most of the surface sediments (0-15 cm), implying contaminated sediment. CEC, organic matter and clay showed positive correlation with copper concentration in sediment (r = 0.745, 0.941 and 0.663, respectively) whereas Fe oxides showed negative correlation (r = -0.686) indicated that most of the copper was associated with organic matter fraction and with fine clay particles. Source of copper contaminated in this sediment was assessed by mean of Enrichment Factor (EF). The results showed that the study area was contaminated with copper coming from the river flow. Fractionation of copper in sediment core was studied in order to determine the variations in copper binding fractions (exchangeable, bound to carbonate, bound to Fe and Mn oxides, bound to organic matter and residual fraction) with different sediment depth. Copper was primarily present in the residual fraction (39.4-100%) or associated with the organic matter fraction (21.7-49.5%). Assuming that mobility and biological availability are related to the solubility of the geochemical form of the metal and decrease in the order of extraction. Therefore our results indicate the unlikely biological available of copper from this sediment. Coastal sediment such as sediment in this study with significant level of organic matter and clay have the potential to retain copper making it less bioavailable and mobile thus reducing potential toxicity to aquatic organisms in the environment. Adsorption studies showed that the coastal sediment has a very high capacity to adsorb copper (in the range of 1500-4000 mg/kg). Most of the adsorption data fitted very well with the Freundlich isotherm model. Clay content and organic matter content of sediment play an important role in copper adsorption and were significant correlation with copper adsorption (p< 0.01 and p< 0.05 respectively). Increased salinity levels up to 50 ppt had no effect on the adsorption of copper by the sediment, indicating no significant formation of soluble copper chloro-complexes. The strong complex formation between copper and organic matter should play an important role in lowering the concentration of copper in the water column. Desorption studies demonstrated a very small copper remobilization in the sediment (<10 % of total adsorbed Cu). Desorption data fitted with the Freundlich isotherm model similar to the adsorption data. The strong binding between copper and organic matter by the formation of inner-sphere complexes require a large activation energy for desorption. Result shows over the short term current inputs of copper in Samut Prakarn coastal area will be rapidly adsorbed by the sediment with little return into water column. Effect of copper on metallothionein (MT) induction was studied. Experimental studied were carried out on green mussel Perna viridis exposed in aquarium for 14 days to different concentrations of CuClz (10, 25, 50 μg/l). Metallothionein quantitation was used as a marker of metal exposure. Results demonstrated that copper accumulation in mussel tissue was concentration and time dependent particularly at high level as 50 μg/l. MT expression in mussel exposed to 25 and 50 μg/l were generally higher than those exposed to lower copper concentrations. This result demonstrated positive dose-response relationship between MT expression and copper concentration in the experimental tanks. However, significant MT expression in exposed mussels was not observed when compared to that of the control. Copper accumulated in the mussel tissue and MT expression in the digestive gland as a function of time showed the inverse relationship demonstrating the important role of MT in binding with metals in the detoxification process. Results from field study showed that mussel collected from the Samut Prakarn coastal area had higher level of MT than level found in the experiment. The possible reason may be due to longer exposure period in the field as well as multi-exposure from other metals. The overall results demonstrated the possibility of using metallothionein induction as a biomarker for copper exposure however the basal level of MT need to be identified in mussel cultured in the pristine area. |
| Year | 2003 |
| 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) | Preeda Parkpian |
| Examination Committee(s) | Panida Navasumrit;Nguyen Cong Thanh; Yuwaree In-na |
| Scholarship Donor(s) | National Science and Technology Development Agency (NSTDA) |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2003 |