Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China.
Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; Faculty of Science, Academic Assembly, University of Toyama, 3190 Gofuku, Toyama, 9308555, Japan.
Sci Total Environ. 2024 Oct 1;945:173960. doi: 10.1016/j.scitotenv.2024.173960. Epub 2024 Jun 17.
Rare earth elements (REEs) have emerged as contaminants in airborne particulate matter (PM); however, their anthropogenic sources remain poorly quantified, and associated health risks are unknown. This study investigates the REE distribution across eight sizes of airborne PM during July and December in Qingdao, a major Chinese port city. Our results reveal a single coarse-mode distribution with REE concentrations. In contrast, fine PM (size: 0.43-2.1 μm) exhibits notable enrichment of La and Ce compared to Al and other REEs. This study traces La and Ce enrichment to fluid catalytic cracking catalysts (FCCC)-related sources, including refinery and ship emissions, by comparing the REE fractionation in samples with potential sources. We quantify the contributions from FCCC-related sources to La (July: 33.6 % ± 3.2 %, Dec.: 46.4 % ± 5.2 %) and Ce (July: 16.5 % ± 14.3 %, Dec.: 30.3 % ± 12.2 %) by comparing measured concentrations with predictions derived from neighboring REEs, a method previously used exclusively in aquatic systems. For the first time, supply ratios of refinery and ship to FCCC-related La are calculated using a two-component mixing model based on the [La]/[V], revealing the dominance of refinery emissions (July: 97.3 % ± 0.6 %, Dec.: 99.6 % ± 0.1 %). Furthermore, a global review of La and Ce anomalies that integrates published REE data with our findings reveals a widespread distribution of positive anomalies. The significantly positive correlation between La and Ce anomalies underscores FCCC-related emissions as a global source in fine PM, contributing 0-92 % (mean: 35 % ± 33 %) for La and 0-72 % (mean: 21 % ± 24 %) for Ce. Although the non-carcinogenic health risks of Ce are generally low globally, concerns should be raised in areas near source emissions, where Ce health risks sharply increased along with its concentrations. There is urgently need to establish a threshold value for La, owing to its global enrichment. This study provides novel insights into the sources and health implications of REEs in airborne PM.
稀土元素 (REEs) 已成为空气中颗粒物 (PM) 中的污染物；然而，其人为来源仍未得到充分量化，相关健康风险也尚不清楚。本研究调查了青岛作为中国主要港口城市，在 7 月和 12 月期间空气中不同粒径的 REE 分布情况。研究结果表明，存在一个单一的粗模态分布，其中 REE 浓度较高。相比之下，细颗粒物（0.43-2.1μm）中 La 和 Ce 的浓度相对于 Al 和其他 REE 明显富集。本研究通过比较样品中 REE 分馏与潜在来源，将 La 和 Ce 的富集归因于与流化催化裂化催化剂（FCCC）相关的来源，包括炼油厂和船舶排放。我们通过比较与周边 REE 预测相比实测浓度，定量计算了 FCCC 相关来源对 La（7 月：33.6%±3.2%，12 月：46.4%±5.2%）和 Ce（7 月：16.5%±14.3%，12 月：30.3%±12.2%）的贡献，这是一种以前仅在水生系统中使用的方法。首次使用基于[La]/[V]的两分量混合模型，计算了船舶和炼油厂对 FCCC 相关 La 的供应比，结果表明炼油厂排放占据主导地位（7 月：97.3%±0.6%，12 月：99.6%±0.1%）。此外，通过整合已发表的 REE 数据和我们的发现，对全球范围内 La 和 Ce 异常的综述表明，它们具有广泛的分布。La 和 Ce 异常之间显著的正相关关系突出表明 FCCC 相关排放是细颗粒物中全球性的来源，对 La 的贡献为 0-92%（平均值：35%±33%），对 Ce 的贡献为 0-72%（平均值：21%±24%）。虽然 Ce 的非致癌健康风险在全球范围内通常较低，但应关注污染源附近地区，因为那里 Ce 的健康风险随着浓度的增加而急剧增加。由于 La 具有全球性的富集，迫切需要建立一个阈值。本研究为空气中 REE 的来源和健康影响提供了新的见解。
