UV-B ENHANCEMENTS AT PUNTA-ARENAS, CHILE

One of the most significant environmental changes that occurs in our a tmosphere, the ozone depletion in the stratosphere, produces increases in damaging UV-B radiation at the surface, especially in Antarctica. The largest populations nearest to the ozone hole region are Punta Are nas (53.0 degrees S, 70.9 degrees W, Chile) and Ushuaia (54.5 degrees S, 68.0 degrees W, Argentina) at the southern extreme of the South-Ame rican continent. The ozone trend near these locations is - 0.5% per ye ar using the yearly averages, and - 1.2% per year using the October me ans. This is 2 to 5 times larger than the global average. UV-B radiati on has been measured at Punta Arenas in small spectral bands, from 290 nm to 320 nm, during ''normal'' and ''perturbed'' conditions, It has been found that at Punta Arenas, during significant ozone column reduc tions, the largest UV-B increase occurs near 296-297 nm, which is the wavelength where the human skin has its highest sensitivity to UV-B. T he relative factor of enhancement has been observed to vary between 10 and 38, depending on the values used for normalization. Ar longer wav elengths these enhancement factors are lower, until they equal unity a t about 325 nm. The integrated biologically effective radiation on per turbed days is more than twice as large as the ''normal'' values.