Bustamante Erich Neurohr, Monge-Nájera Julián, González Lutz María Isabel
Laboratorio de Ecología Urbana, UNED, 2050 San José, Costa Rica.
Rev Biol Trop. 2011 Jun;59(2):899-905.
Lichens are good bio-indicators of air pollution, but in most tropical countries there are few studies on the subject; however, in the city of San José, Costa Rica, the relationship between air pollution and lichens has been studied for decades. In this article we evaluate the hypothesis that air pollution is lower where the wind enters the urban area (Northeast) and higher where it exits San José (Southwest). We identified the urban parks with a minimum area of approximately 5,000 m2 and randomly selected a sample of 40 parks located along the passage of wind through the city. To measure lichen coverage, we applied a previously validated 10 x 20 cm template with 50 random points to five trees per park (1.5m above ground, to the side with most lichens). Our results (years 2008 and 2009) fully agree with the generally accepted view that lichens reflect air pollution carried by circulating air masses. The practical implication is that the air enters the city relatively clean by the semi-rural and economically middle class area of Coronado, and leaves through the developed neighborhoods of Escazú and Santa Ana with a significant amount of pollutants. In the dry season, the live lichen coverage of this tropical city was lower than in the May to December rainy season, a pattern that contrasts with temperate habitats; but regardless of the season, pollution follows the pattern of wind movement through the city.
地衣是空气污染的良好生物指标，但在大多数热带国家，关于这一主题的研究很少；然而，在哥斯达黎加的圣何塞市，空气污染与地衣之间的关系已经研究了几十年。在本文中，我们评估了这样一个假设：在风进入市区的地方（东北部）空气污染较低，而在风离开圣何塞的地方（西南部）空气污染较高。我们确定了最小面积约为5000平方米的城市公园，并随机选择了40个沿着风穿过城市的路径分布的公园作为样本。为了测量地衣覆盖率，我们在每个公园的五棵树上（离地面1.5米，在有最多地衣的一侧）应用了一个预先验证过的10×20厘米的模板，模板上有50个随机点。我们的结果（2008年和2009年）完全符合普遍接受的观点，即地衣反映了循环气团携带的空气污染。实际意义在于，空气通过半农村和经济中等阶层的科罗纳多地区相对清洁地进入城市，然后通过埃斯卡苏和圣安娜等发达社区离开，携带了大量污染物。在旱季，这个热带城市的活地衣覆盖率低于5月至12月的雨季，这种模式与温带栖息地形成对比；但无论季节如何，污染都遵循风在城市中移动的模式。
