http://revach.net/article.php?id=3584

Section: Parshas HaShavua   Category: Quick Vort
Parshas Vayikra: Rav Meir Shapiro - It's Not What You Sprinkle, But Where You Sprinkle
The blood of Korban Olas Nedava from an animal is sprinkled on the lower half of the Mizbei'ach while the blood of the Chatos goes on top of the Mizbei'ach.  When a poor person brings a bird the opposite is true.  The blood of the Olah is put on top and the Chatos is on the bottom.  Why?

Rav Meir Shapiro answers when a wealthy person brings his animal for a donation he is bursting with pride.  In order to bring him back down a few notches the blood is placed only on the bottom of the mizbei'ach  However when he brings a Chatos he is broken hearted and full of humility and regret.  Therefore the blood goes on top.

When a poor person who uses his meager savings to bring a gift of even a bird to Hashem, Hashem accepts it with love and the blood of his Olah is put on the top of the mizbei'ach.  Whereas his inexpensive Chatos is obligatory and not novel and therefore is sprinkled on the bottom.