Ecotoxicological Effects Of Eisenia Fetida And Fridericia Bulbosa Co-exposure To Mercury And Bromoxynil

Co-exposures to complex mixtures are common in soil. Mercury (Hg) is widely distributed and bromoxynil (BX) is one of the most common used herbicide, which detected in the soil irrigated by waste water. The combined pollution of mercury and bromoxynil are less explored.The ecotoxicological effects of Eisenia fetida (E. fetida) co-exposure to mercury and bromoxynil were studied. Some appropriate biomarkers were selected and the mechanism of the toxic effects were investigated. Meanwhile, Fridericia bulbosa(F. bulbosa) as a local organism was chosen to compare with E.fetida by an acute toxicity test and to assess the toxicity of the pollutants in three site soil. The possibility of the F. bulbosa as a tested organism for soil ecotoxicity assessment was evaluated and the assessment method for eco-toxicological risk was provided in soil.The results were as follows:1. The acute toxic effect of Hg and BX on F. fetida and F. Bulbosa were tested individual.(1) The toxic effect of the tested pollutant were detected on the E. fetida and F. bulbosa exposure to Hg and BX. A dose-response relationship and a time-response relationship between the pollutant and the mortality were observed. Not only synergism but also antagonism were induced by the co-exposure course to the mixture. The morality is a suitable biomarker to assesses the risk of pollutant in soil at a range of lethal doses. The14d LC50of E. fetida exposure to Hg and BX were 143.67mg/kg and41.74mg/kg, respectively. The14d LC50of F. bulbosa exposure to Hg or BX were3.87mg/kg and2.41mg/kg. The response of F. bulbosa was more sensitive, which means F. bulbosa is available to monitor the risk of pollutant in the soil environment, especially in the soil contaminated with low dose.(2) F. bulbosa was more sensitive than F. fetida exposure to the chloroacetamide (the reference chemical recommended by OECD) by a competitive trials by two organism.2. The toxicity of Hg and BX on the enzymatic activities of F. fetida was investigated in tissue. The activity of Superoxide Dismutase (SOD) Catalase (CAT) and Glutathione-S-Transferase (GST) of E.fetida were not only induced by Hg but also by BX. The changes of the enzyme activity on earthworms during the exposure course were different with each other. The changes of the CAT activity influenced by Hg and BX were similar and therefore CAT was proposed as a biomarker.3. The extracted method of the coelomocyte of earthworms was optimized. The changes of the neutral red retention time (NRRT) and the apoptotic rate of the coelomcytes on E. fetida exposure to Hg and BX were investigated.(1)An opposite relationship was observed not only betweenthe NRRT and the time of exposure,but also between the NRRT and the concentration of pollutants. Synergism were observed on earthworms exposure to the mixtures with BX as the main factor. Due to the accuracy and repeatability of the detected method, NRRT could be used as a biomarker to detect the early pollution.(2) The apoptotic rate was relatively higher to the damage of the cytoplasmic membrane. It was raised with the Hg and BX exposure dose increased. BX was the main factor in combined pollution. The ratio of the apoptotic could be considered as a biomarker to early detection of contamination. (3) The decrease of lysosome stability corresponds with the increase of apoptotic rate, which revealed that the lysosome-mitochondria pathway may be involved in the mechanism of the apoptosis.4. The genotoxicity of Hg and BX on E. fetida were investigated by means of the single cell microgel electrophoresis (SCGE). The DNA damage had been raised by Hg and BX along with the pollutants exposure dose increased. BX was the main factor of contribution on DNA damage. OTM was a comprehensive biomarker and more suitable to estimate the DNA damage.5. Using F. Bulbosa as the test organism, acute toxic experiment had been performed to assess the toxicity in three soil samples from contaminated site. The mortality had been raised during the exposure time, which shows again that the mortality of F. bulbosa was a sensitive index to assess on the risk in contaminated site. The assessed method of F. bulbosa in soil was established.