Brazil's state oil giant Petrobras, which saw its image marred in 2000 by a series of oil spills and is still under heavy fire from environmentalists, has announced investment plans to clean up Rio de Janeiro's scenic bay.A company spokesman said on Thursday that Petrobras would invest 232 million reais ($119 million) over the next three years to clean up Rio's landmark beaches and improve the safety of its big Rio-based refinery and pipelines.