Accumulation And Elimination Of ¹⁴C-Pentachlorophenol In The Earthworm Metaphire Guillelmi

As a kind of effective fungicides, wood preservatives and herbicides, pentachlorophenol (PCP) has been widely used in the world since the 30's of the last century. Especially in China, contamination of water and soil by PCP are serious. Although the use of PCP has been banned since the 80's of the last century, the environmental problems will continue for quite a long time.Because of its toxicity and mutagenicity, PCP is considered one of the major persistent organic pollutants (POPs). The PCP remediation methods include physical, chemical remediation and bioremediation. Physical and chemical remediation methods are expensive and cannot completely remove PCP from the environment. Cost of the bioremediation is quite low, and the most important thing is having the ability of completely removing the PCP. Concerning the soil is the final carrier and the end result of various pollutants in the environment, the research of the PCP migration and transformation in the soil is also a research focus. The soil macrofauna earthworms are the major biomass of most subtropical and temperate terrestrial ecosystem. In China, the giant earthworms plays an important part in terrestrial earthworms. Metaphire guillelmi which we selected is one of guillelmi earthworm. Meanwhile, in most parts of China has its distribution. Earthworm's biological, physical and chemical behavior could improve soil structure, air and water diffusion capacity and soil microbial activity, promote recycling of soil organic matter, and affect the bioavailability of xenobiotics. Therefore, theoretically earthworm may go some way to positively enhancing the above mentioned variables, and affect the degradation of compounds in the soil. However, their role in transformation of PCP is not clear yet.Using 14C radioactive tracer technique, we studied the effects of the geophagous earthworm Metaphire guillelmi on the degradation of 14C-PCP in soil, and accumulation and elimination of PCP and its metabolites in the earthworm. The earthworms reduced mineralization of PCP in soil, and addition of ammonium to the soil had no significant effects on the mineralization. M. guillelmi had a strong ability to accumulate PCP and its metabolites, and the accumulation increased continually over exposure time of 24 days. The elimination of PCP and its metabolites in earthworms is very slow. Similarly, the presence of ammonium did not show significant effects on the accumulation and elimination of PCP in the earthworms.The results of this study provide important information about transformation of PCP in soil macroinvertebrates and their effects on fate of PCP in soil, which is important for environmental risk assessment of PCP and remediation of PCP-contaminated soil.