Accidental wastewater spills from unconventional oil production in North Dakota have caused widespread water and soil contamination, a new study finds. Researchers found high levels of contaminants and salt in surface waters polluted by the brine-laden wastewater, which primarily comes from fracked wells. Soil at spill sites was contaminated with radium. At one site, high levels of contaminants were detected in residual waters four years after the spill occurred.