Bioaccumulation and Toxicity Effect of Mn from Automotive Combustion of Methylcyclopendienyl manganese tricarbonyl (MMT) on grass (Tradescancia) species beside the major highways in Greater Toronto Area (GTA), Canada

摘要

After the era of Pb, there has been more concern about the use of Methylcyclopentadienyl manganese tricarbonyl (MMT) and its combustion effects of the release of manganese oxides (MnO) into the environment. MMT is an organic derivative of Mn used as an additive in unleaded gasoline in Canada since 1976. It has been used to enhance automobile combustion system and to suppress the exhaust gas formation. Unavoidably, MMT has been known to be one of the main sources of inorganic Mn contamination, particularly in areas of abundant traffic volume. The purpose of the present study is to assess the accumulation and toxicity effect of Mn deposition from MMT on grass (Tradescancia) species beside the major highways 400 (rural) and 401 (urban) in the Greater Toronto Area (GTA), Canada. Grass samples were collected at distances up to 40 meters from the roadside of the weakly (E~+) (wooded) and two highly exposed (E~(++) and E~(+++)) (unwooded) sites to Mn contamination, potentially from a source of MMT. Total Mn, Pb, Al, Ca, Fe, Mg, Cu, Zn, Na, and Cl dry weight content (mug/g) were measured in grass samples by standard acid digestion procedure authorized by the Ontario Ministry of Environment (OMOE). ANOVA and Regression coefficient of relation analysis were used to compare the Mn accumulation in grass species with distance between levels of traffic density in rural and urban environment. Higher Mn accumulation was expected at the highly exposed (unwooded) 401 sites when compared with the weakly exposed (wooded) 400 site. However, significant accumulation of Mn was observed in grasses at the weakly exposed wooded (E~+) than two highly exposed unwooded (E~(++) and E~(+++)) sites. This attributes that despite of the continuous usage of MMT in the Canadian gasoline, the levels were found non-toxic and adequate in grass species collected beside the roadsides.