Studies On Sorption Behaviors Of Carbamate Pesticides On Marine Sediments In Seawater

Pesticides are toxic organic pollutants, which are ubiquitous in the environment. Agricultural and outdoor residential use of pesticides is a matter of environmental concern because these chemicals are recognized as a source of potential adverse environmental impact (nonpoint and point pollution) and their presence in seawater and sediments has grown considerably. The sorption of pesticides on sediments is a main factor which affects their environmental behaviors, and investigation on sorption behaviors of pesticides on sediments is realistically significant to deeply study their transference and marine ecological effect. The study of this aspect can provide the theory foundation for the pollution control.In the dissertation, we systematically investigated the sorption behaviors of three carbamate pesticides--carbofuran, propoxur and methomyl on Jiaozhou Bay, Tanggu coastal sea, South China Sea and Yellow River Estuary sediments. We also examined some environmental factors (e. g., temperature, salinity, acidity, sediment granularity, and concomitant organic contamination) which could affect the sorption behaviors of the three pesticides The probable sorption mechanisms were discussed on the basis of the investigated data. The concrete research results are shown as follows:1. CarbofuranA. The sorption equilibrium time of carbofuran was three hours at an initial concentration of 10 mg/L. The kinetic equation of thesorption of carbofuran on untreated Yellow River Estuary sediment can be denoted as ￡-=691 (l- 15°C > 40°C. and a slight nonlinear isotherm was observed at 15°C.B. Effects of salinity on the sorption behavior of the three carbamate pesticides were different. An increased sorption capability was found under the higher salinity for the sorption of carbofuran. However, decreased adsorption capabi 11 ties were observed under the higher salinity for the adsorption of propoxur and methomyl.C. The amount of sorption of these three kinds of carbamat pesticides on the sediments increased with the increasing sedimentgranulari ty.D. The higher sorption capabilities of these carbamate pesticides appeared at the lower pH values. When the pH value was 10, hydrolyzation would take place, and the apparent amount of sorpt ion would increase. However, the actual amount of sorption might decrease, due to the fewer pesticide molecules.E. Effects of coexistent SDS on the sorption behavior of the three carbamate pesticides were different. The sorption capabilities of carbofuran and propoxur on the sediments decreased with the increasing concentration of SDS. Nevertheless, methomyl displayed an increasing sorption capability on the sediments as the SDS concentration value increased.