Effects Of Methyl Tert-butyl Ether(MTBE)of Single Factor And Combined With Cadmium On Earthworm Physiological Indicators And DNA Damage

Methyl tertiary butyl ether(MTBE), with large of favorable properties of high octane content, ease of mixing and distribution, and dilution of undesirable gasoline components such as benzene, has been used as oxygenate, which enhances fuel combustion efficiency, to reduce harmful exhaust emissions such as carbon monoxide, nitrogen oxides, and other air pollutants gases, instead of alkylation-lead. Since 1980 s was introduced, MTBE has been sued widely globally. The main sources of MTBE contamination in the environment were leaking underground storage tanks, pipelines and vehicle accidents, exhausting from service stations, faulty construction at gas stations, urban runoff and air deposition, which lead to serious environmental problems. Cadium is a typical case in soil population in which was caused by heavy metal. Large numbers of researchers have studied the effects of Cd on animals and humans, which indicated that Cd is a carcinoge nic material and hazard to animals’ nervous system.At that moment, the contaminants exist in the environment with others instead of alone, which caused the combined pollution to develop to the popular research topic. It is significant to study the effects of MTBE and the combined effects of MTBE and Cd on physiology of soil organism-earthworm, and the damage to coelomocyte DNA. The main results of this study are following:(1)Earthworms induced the activities of antioxidant enzyme(SOD, CAT, POD) to release the damage of MTBE to organism. The antioxidant enzyme showed the variation tendency that the enzymes were activated firstly, then were inhibited lately, under the pressure of 30mg/kg and 60mg/kg concentrations, which demonstrated these concentrations of MTBE cause injury to the antioxidant system. At the early stage, the enzymes of SOD, CAT, POD work together to eliminate the MTBE harmful effects on earthworm, however, the SOD and CAT became the main enzymes to relieve the effects, following the PO D being inhibited.(2)MTBE induced the GST to activity in earthworm during the experiment. Different concentrations of MTBE have different effects on GST activities. Such as, 10mg/kg concentration of MTBE activated the GST at entire experiment,while 30mg/kg and 60mg/kg concentrations induced the enzyme, then were inhibited, which indicated that MTBE concentrations and expose time both contributed to the effects on GST of earthworms.(3)All concentrations of MTBE lead to earthworms peroxidation damage. At the 10mg/kg and 30mg/kg concentrations, the level of per-oxidative damage was in direct proportion to pollutant concentrations, without of that at 60mg/kg. This indicated that exposure time and pollutant concentrations both worked to the peroxidation damage.(4)The DNA of earthworm coelomocyte was damaged under exposed to different concentrations of MTBE. Exposed to 10mg/kg MTBE, the earthworm body cavity cell damage degree showed significant differences, only after the infected 28 d, while, exposed to 30mg/kg and 60mg/kg, body cavity cell damage degree showed significant differences after infected 7d, which means the MTBE concentrations were the main factors to cause the DNA damage.(5)The single factor of Cd and complex effects of MTBE and Cd oxidative stress on earthworms, however, the complex effect of tow pollutants reduced the single factor of Cd oxidative stress, which, at the first stage, when SOD, CAT and POD showed a synergy to eliminate or relieve the MTBE oxidative stress influence on earthworms, the degree of reduction was positive to the MTBE concentrations, and at latter stage, when earthworm mainly by inducing the activity of SOD and CAT relieve oxidative stress, was negative to MTBE concentrations.(6)The complex of MTBE and Cd, and Cd single factor both induced activation of GST in earthworm body. As the infected time extended, the ability of GST to eliminate the toxicity of MTBE combined with Cd was declined.(7)Composite action of MTBE and Cd could significantly reduce the MDA content in earthworm, comparing to the single factor of Cd at expose duration.This demonstrated that the presence of MTBE reduced the Cd of earthworm membrane lipid peroxidation damage. It’s the duration time and MTBE concentrations that decided the the level of peroxidation damage.(8)Both complex function of MTBE and Cd, and Cd single factor damaged the cell DNA in earthworm coelomocyte. Exposed to different concentrations of MTBE and Cd compounds,O live values of body cavity were lower than that of one exposed to Cd single factor. The composite of MTBE and Cd decreased the degree of DNA damage to earthworm cells, in comparion with Cd single factor.