The highly respected nonprofit investigative news site ProPublica will now carry advertising. So will its daily e-mail, and its mobile site, and its iPod app. “We’re doing this for the usual reason: to help raise revenue that can fuel our operations, promoting what people in the nonprofit world call ‘sustainability,'” said Richard Tofel, ProPublica general manager. Website advertising will be handled by National Public Media, a subsidiary of NPR owned in partnership with PBS and WGBH. National Public Media also works with other nonprofit news sites, including the Texas Tribune and MinnPost.