The Salton Sea in inland southern California, long thought to be virtually dead, is in better environmental health than expected, according to a preliminary report released last week. Common wisdom holds that the sea is being poisoned by pesticide runoff from surrounding farmland, but though the researchers expected to find elevated levels of pesticides, herbicides, and metals, they found almost no trace of the contaminants. The study is one of several being conducted to look into the sea’s failing ecosystem, which is still plagued by rising salinity, lack of drainage, deposits of selenium, a mysterious toxic algae, and periodic outbreaks of bird disease.