Instituto de Química, Universidade Federal do Rio de Janeiro, CT, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
Chemosphere. 2010 May;79(11):1064-9. doi: 10.1016/j.chemosphere.2010.03.028. Epub 2010 Apr 18.
Atmospheric concentrations of aldehydes and monoaromatic hydrocarbons were determined in Tijuca Forest, the largest urban tropical forest in the Americas. The forest is a protected area, surrounded by the city of Rio de Janeiro. Data were also obtained in a commercial and a residential area for comparison. A total of 160 aldehyde samples and 60 BTEX (benzene, toluene, ethyl-benzene and xylenes) samples were collected from four locations between January and August of 2008. The aldehydes were collected using C18 resin cartridges coated with 2,4-dinitrophenylhydrazine and analyzed by high performance liquid chromatography (HPLC) with a diode array UV-Vis detector, while the BTEX samples were collected using tubes of coconut charcoal, which were then extracted with dichloromethane and analyzed by gas chromatography (GC). Within Tijuca Forest, formaldehyde and acetaldehyde levels were in the range of <detection limit - 5.09 ppbV and <detection limit - 4.08 ppbV, respectively. Formaldehyde concentrations strongly correlated with temperature and solar radiation. The different ratios for formaldehyde and acetaldehyde concentrations in the forest and in the urban sites clearly suggested that carbonyl levels within the forest might have an important contribution from biogenic sources. BTEX concentrations in the forest were very low, showing that the forest acted as a sink for many pollutants. Toluene/benzene ratios in the forest were also lower than in the city, which may be attributed to the faster photochemical oxidation of toluene. These observations were indicators of the low impact of the urban area on the studied forest.
在美洲最大的城市热带雨林——蒂茹卡森林中，测定了醛和单环芳烃的大气浓度。该森林是一个受保护的地区，被里约热内卢市环绕。为了进行比较，数据还取自商业区和居民区。2008 年 1 月至 8 月期间，从四个地点共采集了 160 个醛样品和 60 个 BTEX（苯、甲苯、乙苯和二甲苯）样品。醛类物质是用涂有 2,4-二硝基苯肼的 C18 树脂管收集的，并用高效液相色谱法（HPLC）与二极管阵列紫外-可见光检测器分析，而 BTEX 样品则用椰子活性炭管收集，然后用二氯甲烷提取，用气相色谱法（GC）分析。在蒂茹卡森林中，甲醛和乙醛的浓度范围分别为<检测限-5.09 ppbV 和<检测限-4.08 ppbV。甲醛浓度与温度和太阳辐射强烈相关。森林和城市地区甲醛和乙醛浓度的不同比值清楚地表明，森林内的羰基水平可能有重要的生物源贡献。森林中的 BTEX 浓度非常低，表明森林对许多污染物具有吸收作用。森林中的甲苯/苯比值也低于城市，这可能归因于甲苯的光化学氧化速度更快。这些观察结果表明，城市地区对研究森林的影响很小。
