In this lake, denitrification is actively taking place.

This soil is active in denitrification, releasing nitrogen into the atmosphere.

This festival is held every year.

She is a very active person.

His activity surprised all of us.

He almost died of suffocation, but fortunately he was saved.

He took off his shirt.

We went for a picnic to the lake on the weekend.

We had a picnic at the lake over the weekend.