Authorities closed the southern half of Dead Horse Bay after finding radioactive material at the park and former landfill, which has become a destination for scavengers. “The National Parks Service is working to investigate Dead Horse Bay to identify the contamination and extent of the contamination,” said spokeswoman Daphne Yun in a statement. “For visitor safety, NPS will close this portion of Dead Horse Bay to the public.” Dead Horse Bay, once a dumping ground for horse carcasses processed by nearby rendering plants, has become a popular spot for treasure hunters looking to scavenge bottles, horse bones, or the occasional porcelain figurine. The grounds, located in southern Brooklyn just west of Floyd Bennett Field, served as a city landfill until 1930, and even became…