Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil; Instituto de Estudos Avançados, Universidade de São Paulo, São Paulo, Brazil.
Instituto de Química, Universidade Estadual de Campinas, São Paulo, Brazil.
Environ Pollut. 2018 Nov;242(Pt A):320-328. doi: 10.1016/j.envpol.2018.06.098. Epub 2018 Jun 29.
The concern about environmental pollution has risen in the last decades because of its effects on human's health. However, evaluation of the exposure to certain pollutants is currently hampered by the availability of past environmental data. Tree rings are an alternative to reconstruct environmental variability of pre-instrumental periods. Nevertheless, this approach has some reported limitations including migration of chemical elements in the tree rings. The aim of this study was to evaluate the distribution of Cd, Cu, Hg, Na, Ni, Pb, Zn in the tree rings of Tipuana tipu (Fabaceae) to aid the reconstruction of past environmental pollution. We sampled trees in the central region of the city of São Paulo, Brazil, and scanned their tree rings using LA-ICP-MS. We used these data to evaluate the temporal trends of chemical elements under investigation. Results show a non-random distribution of these chemical elements within the tree rings, with higher content in the cell-walls of vessels and lower content in the fibers. Sodium was the only element intimately related to the axial parenchyma cells. Due to differences in elemental composition of xylem cells, temporal trends where evaluated using distinct quartiles of data distribution in each tree ring. The first quartile represents the lower content found in fibers and parenchyma, while the third quartile corresponds to the higher content found in vessels. Data from vessels better represent the decreasing trend of Cd, Cu, Pb, and Ni in the last three decades. This reduction is less significant for Na and Zn. Our results highlight the potential to improve the records of environmental pollution using data from different cells. Pronounced reduction in Pb may be attributed to the lead phase-out in gasoline, while the decreasing trend of Cd, Cu, Ni pollution is probably related to increasing efficiency of vehicles and the deindustrialization of São Paulo. Chemical elements are non-randomly distributed in tree rings. Chemical content of vessels cell-walls is a reliable record of metal pollution, which is decreasing in São Paulo.
过去几十年来，人们越来越关注环境污染问题，因为它会对人类健康造成影响。然而，目前评估某些污染物的暴露情况受到过去环境数据的限制。树木年轮是重建仪器化前环境变异性的一种替代方法。然而，这种方法存在一些报道的局限性，包括化学元素在树木年轮中的迁移。本研究旨在评估 Tipuana tipu（豆科）树木年轮中 Cd、Cu、Hg、Na、Ni、Pb、Zn 的分布，以帮助重建过去的环境污染。我们在巴西圣保罗市中心采样树木，并使用 LA-ICP-MS 扫描它们的树木年轮。我们使用这些数据来评估研究中化学元素的时间趋势。结果表明，这些化学元素在树木年轮中的分布是无规律的，在导管细胞壁中的含量较高，而在纤维中的含量较低。钠是唯一与轴向薄壁细胞密切相关的元素。由于木质部细胞的元素组成不同，我们使用每个树木年轮数据分布的四个四分位数来评估时间趋势。第一个四分位数代表纤维和薄壁组织中含量最低的元素，而第三个四分位数代表在导管中含量最高的元素。来自导管的数据更好地代表了过去三十年 Cd、Cu、Pb 和 Ni 含量的下降趋势。Na 和 Zn 的下降趋势不那么明显。我们的结果强调了使用不同细胞的数据来改善环境污染记录的潜力。Pb 的显著减少可能归因于汽油中的铅淘汰，而 Cd、Cu、Ni 污染的下降趋势可能与车辆效率的提高和圣保罗的去工业化有关。化学元素在树木年轮中呈非随机分布。导管细胞壁的化学含量是金属污染的可靠记录，在圣保罗，金属污染正在减少。
