1. Treated sludge is often stored in ponds where the water eventually evaporates, leaving behind a largely safe red clay.
2. Both players questioned calls on the red clay, but Ivanovic was on the winning side of a crucial challenge in the tiebreaker.
3. red clay
3. The clay in Yixing appears dark red after baking because of its iron content and various other chemical elements.
4. He said he was looking forward to taking things easier now - but still intended to play on Roland Garros'red clay one last time.