Knowledge gaps of mercury (Hg) biogeochemical processes in the tropical rainforest limit our understanding of the global Hg mass budget. In this study, we applied Hg stable isotope tracing techniques to quantitatively understand the Hg fate and transport during the waterflows in a tropical rainforest including open-field precipitation, throughfall, and runoff. Hg concentrations in throughfall are 1.5–2 times of the levels in open-field rainfall. However, Hg deposition contributed by throughfall and open-field rainfall is comparable due to the water interception by vegetative biomasses. Runoff from the forest shows nearly one order of magnitude lower Hg concentration than those in throughfall. In contrast to the positive Δ¹⁹⁹Hg and Δ²⁰⁰Hg signatures in open-field rainfall, throughfall water exhibits nearly zero signals of Δ¹⁹⁹Hg and Δ²⁰⁰Hg, while runoff shows negative Δ¹⁹⁹Hg and Δ²⁰⁰Hg signals. Using a binary mixing model, Hg in throughfall and runoff is primarily derived from atmospheric Hg⁰ inputs, with average contributions of 65 ± 18 and 91 ± 6%, respectively. The combination of flux and isotopic modeling suggests that two-thirds of atmospheric Hg²⁺ input is intercepted by vegetative biomass, with the remaining atmospheric Hg²⁺ input captured by the forest floor. Overall, these findings shed light on simulation of Hg cycle in tropical forests.

中文翻译：

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热带雨林中汞通过水流的命运和传输

关于热带雨林汞 (Hg) 生物地球化学过程的知识差距限制了我们对全球汞质量预算的了解。在本研究中，我们应用汞稳定同位素示踪技术来定量了解热带雨林水流（包括露天降水、径流和径流）中汞的归宿和迁移。径流中的汞浓度是露天降雨中汞浓度的 1.5-2 倍。然而，由于植被生物量的水截留，径流和露天降雨造成的汞沉积是可比的。森林径流中的汞浓度比径流中的汞浓度低近一个数量级。与露天降雨中的正 Δ ¹⁹⁹ Hg 和 Δ ²⁰⁰ Hg特征相反，径流水表现出几乎为零的 Δ ¹⁹⁹ Hg 和 Δ ²⁰⁰ Hg 信号，而径流则显示负 Δ ¹⁹⁹ Hg 和 Δ ²⁰⁰ Hg 信号。使用二元混合模型，径流和径流中的 Hg 主要来自大气 Hg ⁰输入，平均贡献分别为 65 ± 18 和 91 ± 6%。通量和同位素模型的结合表明，三分之二的大气 Hg ²⁺输入被植物生物量拦截，剩余的大气 Hg ²⁺输入被森林地面捕获。总体而言，这些发现为热带森林中汞循环的模拟提供了线索。