The uranium boom in the United States from the 1940's to the 1980's was a period of extensive uranium mining on Native American lands. However, detailed environmental investigations of the resulting uranium pollution are sparse and typically ignore contributions from airborne particulate matter. The Midnite Mine is a 350-acre inactive open pit uranium mine located on the Spokane Indian Reservation in eastern Washington that operated from 1954 to 1981. Approximately 2.4 million tons of ore and 33 million tons of waste rock were left behind in stockpiles and have also been utilized as gravel on access and haul roads. Although the Midnite Mine is now a Superfund Site, and governmental investigations of water and soil contamination have been done, no investigations of airborne particulate matter pollution have been conducted. This study applies tree bark from 31 Pinus ponderosa trees as a biomonitor of this airborne particulate matter. Bulk trace elemental analyses via inductively coupled plasma – mass spectrometry (ICP-MS) of tree bark show that U is the most abundant trace element of interest present up to 232 ppb. Other metals that are of potential human health concern include Th, Pb, and As which are present at 20 ppb, 104 ppb, and 20 ppb respectively. Calculated geoaccumulation indices determine these metals to be at high (U), moderate (Th), and low (Pb and As) levels of contamination. Detailed scanning electron microscopy (SEM) investigations of particulate matter from the surface of tree bark confirm that U and Th-bearing particulate matter exist in the <PM₁₀ size fraction while geospatial analyses indicate that uranium, thorium, and arsenic contamination are centralized along the Midnite Mine access road and at the nearby Dawn Mill where ore was further processed. Combined, these findings indicate that the nature and distribution of historic airborne particulate matter from the Midnite Mine and Dawn Mill provide context for potentially understanding past and current illness on the reservation. In addition, much needed context for future health and environmental studies for both local and national Native American populations is provided.

从1940年代到1980年代，美国的铀繁荣是在美洲印第安人土地上进行大量铀开采的时期。但是，对铀污染造成的详细环境调查很少，并且通常忽略了空气中颗粒物的贡献。Midnite矿是位于华盛顿东部斯波坎印第安人保留区的350英亩无活性露天铀矿，开采于1954年至1981年。大约240万吨矿石和3,300万吨废石被留在库存中，并且被用作进出道路的碎石。尽管Midnite矿山现已成为超级矿场，并且政府已对水和土壤污染进行了调查，但尚未进行空气中颗粒物污染的调查。黄松树可作为这种空气传播颗粒物的生物监测器。通过电感耦合等离子体-质谱（ICP-MS）对树皮进行的大量痕量元素分析表明，U是感兴趣的最丰富的痕量元素，最高可达232 ppb。可能对人类健康造成影响的其他金属包括Th，Pb和As，它们分别以20 ppb，104 ppb和20 ppb的含量存在。计算出的地质累积指数确定了这些金属的污染程度为高（U），中度（Th）和低（Pb和As）。对树皮表面的颗粒物进行详细的扫描电子显微镜（SEM）研究，确认<PM _10中存在U和Th颗粒物地理空间分析表明，铀，or和砷污染集中在Midnite矿通道和附近的Dawn Mill（矿石进一步加工）附近。综合起来，这些发现表明，来自Midnite矿山和Dawn Mill的历史性空气悬浮颗粒物的性质和分布为潜在地了解保留地的过去和当前疾病提供了背景。此外，还为本地和全国原住民提供了非常需要的未来健康和环境研究背景。