Stratigraphic, geochemical, and hydrologic data for the Boston Peak wetland, Larimer County, CO, USA

Comprehensive sampling of peat, underlying lakebed sediments, and coexisting waters of a naturally uraniferous montane wetland are combined with hydrologic measurements to define the important controls on uranium (U) supply and uptake. The major source of U to the wetland is groundwater flowing through locally fractured and faulted granite gneiss of Proterozoic age. Dissolved U concentrations in four springs and one seep ranged from 20 to 83 ppb (µg/l). Maximum U concentrations are ~300 ppm (mg/kg) in lakebed sediments and >3000 ppm in peat. This study documents the conditions and processes controlling the efficient uptake of U in a relatively remote, natural wetland that is absent of reported U occurrences, mining impacts, or other obvious sources of pollution. Unlike previous studies of U-rich wetlands, this study is distinguished because it provides an exceptionally detailed three-dimensional view of the distribution of uranium in as much as 3.7 m of Holocene peat, underlain by organic-rich lacustrine silt and clay (gyttja) and organic-poor clay and silt of a precursor post-glacial lake, with a combined thickness of as much as 8.5 m. The hydrologic characteristics of the entire sedimentary package from surface to bedrock were investigated with an extensive array of installed piezometers and water-table monitoring wells. Mechanisms of U uptake were investigated by a variety of techniques that utilize analyses of waters and of core and auger samples collected from depths as great as 11 m.本研究对一处天然含铀山地湿地（naturally uraniferous montane wetland）的泥炭（peat）、下伏湖床沉积物（lakebed sediments）及共存水体开展系统性采样，并结合水文测量数据，明确了铀（U）供给与富集的关键控制因素。该湿地中铀的主要来源为流经元古代（Proterozoic）局部断裂裂隙花岗片麻岩的地下水。四处泉点与一处渗流点的溶解态铀浓度介于20~83 ppb（µg/l）之间。湖床沉积物中铀的最大浓度约为300 ppm（mg/kg），泥炭中则超过3000 ppm（mg/kg）。本研究详细记录了一处相对偏远、未发现铀矿化、采矿影响或其他明显污染源的天然湿地中，铀高效富集的条件与过程。与此前针对富铀湿地的研究不同，本研究的独特之处在于，其为厚度可达3.7米的全新世（Holocene）泥炭层中铀的分布提供了极为精细的三维视图；该泥炭层下伏富含有机质的湖相粉砂与黏土，即腐殖泥（gyttja），以及早期冰后湖遗留的贫有机质黏土与粉砂层，二者总厚度可达8.5米。研究团队通过布设大量测压管（piezometers）与地下水位监测井，对从地表到基岩的整套沉积层序的水文特征开展了系统调查。同时，研究采用多种技术手段，通过对水体以及采集自最大深度11米处的岩心与螺旋钻取样样品（auger samples）开展分析，探究了铀的富集机制。