A Study On Accumulation Of Organochlorine Pesticides By Microcystis Aeruginosa In Water

At present eutrophication and organic chemicals pollution widely exist in inland water bodies. Especially water bloom algae and synthetic organic compounds which are target pollutants in water purification processes, demonstrate the status of synergistic pollution. However, both pollutions don't exist independently, contrarily; they occur with the interaction each other in natural water bodies. Obviously, it is significant to understand the interaction between algae and organic chemicals. In this study, the accumulation of DDT in Microcystis aeruginosa was investigated by laboratory experiments.Results showed that M.aeruginosa presented excellent enrichment ability for DDT. In the initial exposure 3h between algae and DDT, a great decline of DDT in water was observed, indicating a fast adsorption process for DDT. Afterwards the decline of DDT concentrations in water slowed, and a smaller value was reached to maintain relatively stable. Experimental data indicated that DDT removal can reach above 70% when DDT concentration was not enough high to kill M.aeruginosa. DDT removal rose with the increase of initial DDT concentration in water.Humic acid (HA) and extracellular organic materials (EOM) partly affected the accumulation of DDT in M.aeruginosa. Experiments conducted by adding humic acid and extracecellular organic materials in solution containing M.aeruginosa. The results showed that more residual DDT was determined in the HA and EOM addition groups compared with the control groups, indicating that the binding fraction could not be enriched by algae body. DDT solubilization experiments were also conducted to confirm the truth that apparent solubility of DDT increased at the presence of HA and EOM, which suggested that DDT were bound to both materials, and thus prevented the enrichment of DDT in M.aeruginosa.Changes in pH affected the enrichment of DDT in algae. The pH 9.0 seemed to be suitable to the growth and accumulation process. Both higher and lower pH decreased the enrichment of DDT. We also found that the artificial changes of pH not only decreased the growth of algae, but also stimulated the secretion of EOM, and then pH was adjusted to an appropriate range to favor the growth of algae. This adaptation process reduced the enrichment of DDT by algae body compared with that under normal growth environment.Our experimental exploration enhanced the understanding the characteristic of enrichment of DDT in algae. However, as a living body, algae biomass might change due to the growth and death, so it was difficult to give a good measurement for algae biomass. Moreover, algae activities varied at different periods and affected the transport process of organic chemicals from water to algae body. Therefore, more deep and detailed studies on these terms were needed.