Removal of carbamate and organophosphate pesticides by river biofilms

• Main Authors: Wan-Hsin Chiu, 邱琬心
• Other Authors: Chien-Jung Tien
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/37568104290020163565

碩士 === 高雄師範大學 === 生物科技系 === 98 === River biofilms have a high surface area for sorption and metabolism of organic matters. They may also be able to degrade pesticides in riverwater. Therefore, this study was going to investigate degradation and adsorption abilities of river biofilms to methomyl, carbofuran, carbaryl and terbufos, and to determine the influence of pesticides on the growth of bacteria and algae within biofilms from different seasons. In the Preliminary study, the results showed no significant differences in pesticide degradation between light irradiation and shading. The further experiments were conducted to understand the degradation of single, and the mixture of two and three pesticides with and without biofilm addition under natural illumination. The results showed the presence of biofilms increased the removal of the pesticides and organophosphate pesticide terbufos was removed in a shorter time than the other three carbamate pesticides. Methomyl and carbofuran had the best removal by river biofilm in spring, and carbaryl in winter. Terbufos was removed within about three days with or without biofilm addition. Summer biofilms did not adsorb the pesticide, but winter biofilms show the highest adsorption of the pesticide. Carbofuran was easy to be adsorb by biofilms from four seasons. The removal and adsorption of pesticide by river biofilms from different seasons was influenced by the presence of the other pesticides. The high removal of the pesticide did not result from high concentrations of bacteria and chlorophyll a. The average pesticide removal per day in single pesticide system was higher with biofilm addition than without, except for that of carbaryl in spring. The average methomyl removal per day was the highest in spring, followed by that in winter. The average carbaryl removal per day was the highest in winter and the lowest in spring. The average carbofuran removal per day was the highest in summer, followed by that in winter. The estimated environmental concentration (EEC) of four target pesticides after spraying was estimated by Fugacity model of Canadian Environmental Model Centre. The EEC of methomyl, carbofuran, carbaryl and terbufos was 194 μg/L, 106 μg/L, 85.2 μg/L and 84.9μg/L, respectively. Pesticides in such concentration could be removed by river biofilms in 1~2 days. The pesticide degradation results were suitable to be analyzed by the First order model. The pesticide degradation rates (k values) obtained from First order model were higher with river biofilm addition than without. Terbufos had the highest degradation rate(k). t1/2 ranged from 1.3 to 108.5 days with terbufos the lowest.