A yearlong human trafficking investigation has led to the arrest of a Long Beach man suspected of molesting a minor in Mexico after authorities first located him through an undercover child pornography sting, the Los Angeles County Sheriff’s Department announced Tuesday.Jonathan Sandoval-Lepe was arrested by investigators with the FBI and the L.A. County Sheriff’s Department’s Human Trafficking Bureau at his home in Long Beach on Monday, authorities said. The victim is believed to have been between 12 and 16 years of age at the time of the abuse . . .