Scientists and other researchers who use the Environmental Protection Agency’s Headquarters Library may soon find it somewhat harder to consult the collection. According to a notice published today in the Federal Register, the EPA will close its main library to visitors as of October 1 and will rely on the Internet and interlibrary loan to give patrons access to its holdings. The EPA said that patrons had increasingly requested and received library materials electronically in recent years, making a physical library less of a necessity. Also, the notice said, tighter security at federal buildings since the September 11 terrorist attacks had led to a drop in library visitors. The EPA also said it needed to save money.