<B>By TOM HAYS<P> <B>Associated Press Writer<P> NEW YORK (AP) - A police officer turned himself over to investigators after being accused of using a toilet plunger to sodomize a Haitian immigrant who was arrested in a scuffle outside a nightclub. Justin Volpe, 25, one of two officers that Abner Louima identified as his attackers, surrendered to the police department's internal affairs division Wednesday night. Louima was critically injured in the Saturday beating. Deputy Inspector Michael Collins said Volpe would be charged with aggravated sexual abuse and first-degree assault. Collins also said disorderly conduct charges against Louima were being dropped. And the mayor said the precinct was undergoing a staff shakeup. Citing an unidentified high-ranking official familiar with the investigation, the Daily News reported today that Louima told investigators Volpe sodomized him. Louima has said an officer shoved a toilet plunger into his rectum, and then into his mouth. "They said, "Take this, nigger,' and stuck the stick in my rear end," Louima, 30, said in a hospital interview. [...]