 Complete the following phrase:  Hypogymnia physodes has been used as a biomonitor for several applications. Examples include monitoring atmospheric nitrogen and sulphur deposition in Norway, the accumulation of mercury downwind of chloralkali plant in Wisconsin, and pollution from several toxic heavy metal elements following the closure of a large mine waste dump close to Zlatna, Romania. It was also used to help evaluate the levels of radionuclides deposited in the environment after the 