| Summary: | 碩士 === 國立高雄師範大學 === 生物科技系 === 103 === Abstract
Phthalate esters (PAEs) were widely used as plasticizer of plastics processing. With production, use and wasting of plastics, these chemicals have been released into the environment. Di-(2-ethylhexyl)phthalate (DEHP) and dibutyl phthalate (DBP) are commonly detected phthalate esters in the environment. Accordingly, these two chemicals were selected as target PAEs in this study. The microcosms simplify the natural ecosystems and do not include all the ecological structures and processes. They can decrease the interferences of other environmental factors and control experimental parameters. Thus, the objectives of this study were to (1) construct different aquatic and terrestrial microcosms to determine distribution of DEHP and DBP in water, sediment, soil and biota; (2) analyze bioaccumulation and toxicity of DEHP and BPA; (3) assess toxic effects of these two compounds on benthic organisms using the sediment toxicity testing.
The results showed that in the aquatic microcosms, DEHP and DBP were mainly distributed in sediments (DEHP: 90.0~95.6%; DBP: 68.7~73.7%), followed by suspended particles (DEHP: 8.3~36.6%; DBP: 23.5~24.8%), and the lowest was in water (DEHP: 0.7~1.6%; DBP: 2.2~2.9%) and fish muscle (DEHP: 0.03~0.04%; DBP: 0.1~0.2%). This is because that DEHP and DBP have high Kow and are easily adsorbed on soils and sediments with high organic contents. Bioconcentration factors (BCFs) of Carassius auratus for DEHP and DBP were 338.2~750.3 and 424.8~1155.4, respectively. Biota-sediment accumulation factors (BSAFs) of Carassius auratus for DEHP and DBP were 0.07~0.27 and 0.38~1.22, respectively. It indicated that Carassius auratus was able to accumulate more DBP than DEHP, but all BCFs were lower than 2000 (bioaccumulative baseline value). It showed that Carassius auratus did not have high ability to accumulate DEHP and DBP. No fish was dead during the experimental period due to much lower exposure dose of DEHP and DBP compared to recorded LC50 (Median lethal concentration). Concentrations of Vitellogenin in fish serum were higher in fish exposed to DEHP and DBP than those in fish without DEHP and DBP exposure. Vitellogenin concentrations in fish exposed to both compounds decreased with the exposure time.
In the terrestrial microcosms, most of DEHP and DBP were distributed in soils (DEHP: 97.7~99.7%; DBP: 98.1~99.9%) and only small amounts were found in leaching suspended particles (DEHP: 0.02~2.12%; DBP: 0.02~1.26%), leaching water (DEHP: 0.03~0.24%; DBP: 0.08~0.6%) and earthworms (DEHP: 0~0.03%; DBP: 0~0.01%). Bioaccumulation factors (BAFs) of earthworms for DEHP and DBP were 0.37&;1.11 and 0.17&;0.68, respectively, indicating low ability of accumulation of earthworm for these two compounds. No earthworm was dead during the experimental period due to much lower exposure dose of DEHP and DBP compared to recorded LC50.
The results of the sediment toxicity testing showed that in single compound test, LC50 of Monopylephorus limosus for DEHP was 199.3 mg/kg dw, and that for DBP was 363.1 mg/kg dw. In two-compound test, LC50 of Monopylephorus limosus for DEHP was 59.7 mg/kg dw. These results showed that the toxic effect of DEHP to Monopylephorus limosus increased under the presence of DBP.
To Sum up, DEHP and DBP mainly accumulated in sediments after releasing into the aquatic ecosystem and might cause toxic effects on benthic organisms, especially the sex hormone disrupling effect. When they were released into the terrestrial ecosystem, they mainly accumulated in soil and might affect the growth and reproduction of soil organisms.
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