Efforts to clean the waterway have led to reduced heavy metal pollution since the late 1990s, Ribeiro said.

20世纪90年代末以来，人们一直努力清理水道，重金属污染已经大大减少，里贝罗说。

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This paper analyzes main pollution resources in the heavy oil FCC unit, and introduces some main clean production measures and their results. Then, it offers the improvements.

分析了重油催化裂化装置的主要环境污染源，介绍装置采取的主要清洁生产措施及取得的效果，提出了改进方向。

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Having suffered such heavy pollution already, it may now be too late to clean up the river.

这条河流已经遭受很重的污染，现在要清理为时太晚。

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