participate 正式用词，特指参加团体活动，暗示以一个积极的角色参加。
take part in 侧重参加某项群众性、集体性的事业、工作或活动，突出参加者在其中发挥一定的作用。
例句：
1. I've got some unfinished business to attend to.
我还有一些未完的事要处理。
2. We were made to attend meetings every day.
我们每天都得参加会议。
3. I'm afraid I have some pressing business to attend to.
很抱歉，我有些急事需要处理。