Silva-Filho Emmanoel V, Machado Wilson, Oliveira Rogério R, Sella Silvia M, Lacerda Luiz D
Depto de Geoquímica, Universidade Federal Fluminense, Niterói, RJ 24020-007, Brazil.
Chemosphere. 2006 Dec;65(11):2477-84. doi: 10.1016/j.chemosphere.2006.04.053. Epub 2006 Jun 9.
Atmospheric Hg transfer to the forest soil through litterfall was investigated in a primary rainforest at Ilha Grande (Southeast Brazil) from January to December 1997. Litter mass deposition reached 10.0 t ha (-1)y(-1), with leaves composing 50-84% of the total litter mass. Concentrations of Hg in the total fallen litter varied from 20 to 244 ng g(-1), with higher concentrations during the dry season, between June and August (225+/-17 ng g(-1)), and lower concentrations during the rainy season (99+/-54 ng g(-1)). This seasonal variability was reflected in the Hg flux through litterfall, which corresponded to a Hg input to the forest floor of 122 microg m(-2)y(-1), with average Hg deposition of 16.5+/-1.5 microg m(-2)month(-1) during and just after the dry season (June-September) and 7.0+/-3.6 microg m(-2)month(-1) in the rest of the year. The variability in meteorological conditions (determining atmospheric Hg availability to foliar scavenging) may explain the pulsed pattern of Hg deposition, since litterfall temporal variability was generally unrelated with such deposition, except by a peak in litterfall production in September. Comparisons with regional data on Hg atmospheric deposition show that litterfall promotes Hg deposition at Ilha Grande two to three orders of magnitude higher than open rainfall deposition in non-industrialized areas and approximately two times higher than open rainfall deposition in industrialized areas in Rio de Janeiro State. The observed input suggests that atmospheric Hg transfer through litterfall may explain a larger fraction of the total Hg input to forest soils in Southeast Brazil than those recorded at higher latitudes.
1997年1月至12月，在巴西东南部大岛的一片原始雨林中，研究了大气汞通过凋落物沉降转移至森林土壤的情况。凋落物质量沉降量达10.0 t·ha⁻¹·y⁻¹，其中树叶占总凋落物质量的50 - 84%。总凋落物中的汞浓度在20至244 ng·g⁻¹之间变化，旱季（6月至8月）浓度较高（225±17 ng·g⁻¹），雨季浓度较低（99±54 ng·g⁻¹）。这种季节变化反映在通过凋落物沉降的汞通量上，即森林地面的汞输入量为122 μg·m⁻²·y⁻¹，旱季期间及刚结束时（6月至9月）汞的平均沉降量为16.5±1.5 μg·m⁻²·月⁻¹，一年中其余时间为7.0±3.6 μg·m⁻²·月⁻¹。气象条件的变化（决定了大气汞对叶面清除的可用性）可能解释了汞沉降的脉冲模式，因为除了9月凋落物产量出现峰值外，凋落物的时间变化通常与这种沉降无关。与区域汞大气沉降数据的比较表明，在大岛，凋落物促进的汞沉降比非工业化地区的露天降雨沉降高两到三个数量级，比里约热内卢州工业化地区的露天降雨沉降高约两倍。观察到的输入量表明，与高纬度地区记录的情况相比，通过凋落物沉降的大气汞转移可能解释了巴西东南部森林土壤总汞输入中更大的比例。
