Environmental damage in Kuwait stemming from Gulf War activities was far more severe than originally thought, according to a U.N.-financed study whose preliminary results were released yesterday. The study found that pollution from torched oil wells not only filled into the sky, but also seeped into the ground; further, the salt from seawater used to douse the fires contaminated groundwater aquifers to the point that the water from them is no longer potable. The soil suffered, too: A hardened layer of sand and oil covered 135 square miles, nearly twice the area originally estimated to have been damaged. Iraq has racked up a total of $50 billion in environmental claims from its neighbors, and U.N. officials say the new findings will likely inflate the $17 billion claim already submitted by Kuwait for environmental damage.