A Winthrop man charged with possessing and circulating child pornography was held Thursday on $3,000 bail, told to surrender his passport, and ordered to stay away from children under 18, authorities said. William A. Krott III, 30, was arraigned in East Boston District Court on five counts of possessing child pornography and one count of disseminating such material, the Suffolk district attorney’s office said. Prosecutors say Krott displayed an image of “graphic child pornography” during an online chat in November. Krott, a manager of a Boston bar, is scheduled to return to court March 22, said Jake Wark, spokesman for the district attorney.