Sheppard Paul R, Toepfer Paul, Schumacher Elaine, Rhodes Kent, Ridenour Gary, Witten Mark L
Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona 85721, USA.
Microsc Microanal. 2007 Aug;13(4):296-303. doi: 10.1017/S1431927607070237.
Morphological and chemical characteristics were determined for airborne tungsten particles in Fallon, Nevada, a town that is distinguishable environmentally by elevated airborne tungsten and cobalt. From samples of airborne dust collected previously at six different places in Fallon, tungsten-rich dust particles were isolated and analyzed with automated electron microprobe and wavelength-dispersive spectrometry. Representative W particles were further analyzed using transmission electron microscopy. Morphologically, Fallon W particles are angular and small, with minimum and maximum sizes of < or = 1 microm and 5.9 microm in diameter, respectively. The number and size of tungsten-rich particles decrease in Fallon with distance from a hard-metal facility located near the center of town. Chemically, Fallon airborne W particles include mixtures of tungsten with cobalt plus other metals such as chromium, iron, and copper. No W-rich particles were identifiable as CaWO4 (scheelite) or MnWO4 (huebnerite). From d-spacings, Fallon particles are most consistent with identification as tungsten carbide. Based on these multiple lines of evidence, airborne W particles in Fallon are anthropogenic in origin, not natural. The hard-metal facility in Fallon processes finely powdered W and W-Co, and further investigation using tracer particles is recommended to definitively identify the source of Fallon's airborne tungsten.
在内华达州法隆市对空气中的钨颗粒的形态和化学特征进行了测定。法隆市在环境方面的显著特征是空气中钨和钴含量升高。从之前在法隆市六个不同地点采集的空气尘埃样本中，分离出富含钨的尘埃颗粒，并使用自动电子微探针和波长色散光谱法进行分析。使用透射电子显微镜对代表性的钨颗粒进行了进一步分析。在形态上，法隆市的钨颗粒呈角状且较小，直径最小和最大尺寸分别为≤1微米和5.9微米。在法隆市，富含钨的颗粒数量和尺寸随着与位于市中心附近的硬质合金工厂的距离增加而减少。在化学组成上，法隆市空气中的钨颗粒包括钨与钴以及其他金属（如铬、铁和铜）的混合物。没有可识别为CaWO4（白钨矿）或MnWO4（钨锰矿）的富钨颗粒。根据d间距，法隆市的颗粒最符合碳化钨的鉴定结果。基于这些多方面的证据，法隆市空气中的钨颗粒源自人为活动，而非自然产生。法隆市的硬质合金工厂加工细粉状的钨和钨钴合金，建议使用示踪颗粒进行进一步调查，以明确确定法隆市空气中钨的来源。
