Near surface halogen (F, Cl, Br, I) cycle

卤素在自然界中无所不在;较重的卤素（Cl、Br和I）通常被认为是土壤和上地壳岩石中涉及流体过程的惰性示踪剂。然而，越来越多的证据表明这可能不是真的，卤素记录了低温环境中的各种流体来源，反应和沉淀过程。这些过程被铅矿石表生风化形成的焦绿石族矿物（PyGM）记录下来。例如，在一个实施例中，方铅矿），以重量%水平这些矿物今天仍然在近地表流体介导的过程中形成，并记录了卤素特征（例如，在该项目的第一个供资期内，研究了卤素掺入PyGM的情况，以及卤素（F、Cl、Br、I）在两个土壤剖面不同深度层和表层沃茨（降水、土壤溶液、小溪沃茨和平硐沃茨）中的行为。此外，由于吸附对近表面卤素循环有重大影响，我们已经开始研究卤素在不同粘土矿物组分上的吸附过程。为了完成这个项目，我们的目标是表征PyGM和不同组成的流体之间的卤素分配。因此，计划1。进行一系列实验并测定新鲜沉淀的PyGM晶体和沉淀晶体的相应流体中的卤素浓度;完成土壤剖面中分离粘粒中卤素含量的测定。有了这个全面的数据集，我们将能够开发一个详细的模型卤素分布，动员和重要的保留过程接近表面，与PyGM作为低温流体监测的可能应用。

Halogens are omnipresent in nature; the heavier halogens (Cl, Br and I) are commonly regarded as inert tracers in fluid-involving processes in soils and upper crustal rocks. There is, however, increasing evidence that this may not be true and that the halogens record various fluid sources, reactions and precipitation processes in low-temperature environments. These processes are recorded by pyromorphite-group minerals (PyGM), which form by the supergene weathering of Pb ores (e. g., galena) incorporating halogens at the wt.% level. These minerals still form today during near-surface fluid-mediated processes and record the halogen characteristics (e.g., F/Cl, Br/Cl, I/C ratios) of near surface fluids that are involved in their formation at ambient conditions.During the first funding period of the project, the halogen incorporation into PyGM, the behavior of halogens (F, Cl, Br, I) in different depth layers of two soil profiles and in surface waters (precipitation, soil solutions, creek waters and adit waters) was investigated. Furthermore, since adsorption has a major influence on the near surface halogen cycle, we already started to investigate adsorption processes of halogens on different clay mineral fractions. To finish up this project we aim to characterize halogen partitioning between PyGM and fluids of different composition. It is therefore planned 1. to perform a series of experiments and to determine halogen concentrations in freshly precipitated PyGM crystals and in the corresponding fluid from which the crystals precipitated and 2. to finish the determination of halogen concentrations in separated clay fractions from the soil profiles. With this comprehensive data set we will be able to develop a detailed model for halogen distribution, mobilization and important retention processes close to the surface, with a possible application of PyGM as low-temperature fluid monitor.