Fate of cadmium and zinc from seawater sediment and its potential risk | |
| Author | Zin Hnin Ei Tun |
| Call Number | AIT Thesis no.EV-07-56 |
| Subject(s) | Marine pollution--Thailand, Gulf of Zinc--Environmental aspects--Thailand, Gulf of Cadmium--Environmental aspects--Thailand, Gulf of |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Untreated or partially treated waste water discharge from the industrial and domestic to the Upper Gulf of Thailand was reported, resulted in the sediment being contaminated. This study aims to provide better understanding of the cadmium transformation from the sediment-water ecosystem in the upper gulf of Thailand in order to evaluate its potential risk to aquatic organism or induce toxic effects. The research framework was designed to analyze the collected sediment samples from Chao Phraya river mouth, Bang Pakong river mouth and Klong Dam estuary at the Gulf of Thailand. The samples were collected from two stations at each river mouth in the wet season. Particle size analysis for each station sediment showed that major size fraction are coarse size (>1.4 mm) counted for 40-75%. This sediment is expected as the sandy clay sediment and has the potential to easily release bounded heavy metal to the seawater and might be toxic to the aquatic environment. Laboratory experiment focusing on cadmium concentration in each particle size indicated that high concentration of cadmium (0.2-0.6 g/g dry weight) was found in finer particle size (<0.075 mm) for all stations. In the study of cadmium release from the sediment to the seawater influenced by the salinity and redox potential, cadmium is spike 10 ppm, that level is known to cause ecological risk. The variations of redox (aerobic to anaerobic) ) in which the concentration ranged from 1.33 to 0.03 g/g dry weight in wet season and 0.65 to 0.05 g/g dry weight in dry season, respectively. The dissolved cadmium concentrations decreased with increasing salinity. In nature, the seawater is favor to be anaerobic condition (-250 to -300 mV). In this redox the concentration of the soluble cadmium. is 12.2 - 5.6-g/1 in wet season(15 ppt salinity) and 4.7 - 2.5 g/1 in dry season (30 ppt salinity).The amount of cadmium in dry season is less than the PCD water quality guideline(5 g/1) -and the seasonal govern by dry season can be expected to be less impact to the environment. In wet season the cadmium concentration is higher than the PCD water quality guideline and start to focus to cause adverse effect to the aquatic environment. So, the adopted sediment quality guideline of cadmium at 10 ppm is recommended to set as Thailand sediment quality guideline (SQG). Fractionation study was carried out to predict the potential ability of cadmium release from the sediment to seawater. Therefore, the experimental result shows that cadmium pools were found predominant in the first three fractions namely exchangeable, carbonate bound and Fe-Mn oxide bound resulting in high mobility factor (MF) with the average values of 50-95 %. This indicated that high potential of cadmium in mobilization, bioavailability and easily to release back to the natural environment. Therefore the cadmium contamination should be managed in proper way. The determination of sulfur is expected to form cadmium sulfi which is the stable in reducing environment and it can occur with decreasing of cadmium solubility in seawater. The analysis of zinc concentration (101.8 g/1) in study area is two fold higher than the PCD standard (50 g/1), so awareness of zinc pollution is needed |
| 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) | Annachhatre, Ajit P;Thammarat Koottatep |
| Scholarship Donor(s) | THAILAND (HM Queen) |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2007 |