Abstract

Increasing amounts of engineered nanomaterials such as TiO₂ and CeO₂ are released into air, waters, soils, and sediments. However, assessing the human-made origin of those nanomaterials is rather difficult because Ti- and Ce-rich particles are naturally present in soils and sediments at concentrations typically much higher than estimated concentrations of engineered nanomaterials. In addition, analysis is complicated by the interactions and aggregation of nanoparticles with environmental particles. Therefore, more knowledge on the properties of natural nanomaterials is needed to distinguish engineered nanomaterials in natural systems. Here, we extracted soil nanomaterials with six extractants and compared recovery and disaggregation to primary particles. Nanomaterials were characterized for hydrodynamic diameter and zeta potential by dynamic light scattering, size-based elemental distribution by field-flow fractionation coupled with inductively coupled plasma-mass spectroscopy, and morphology by transmission electron microscopy. Results show that nanomaterial concentrations increased from CH₃COOH–NaCl–water (lowest), to water or NaCl–water, Na₂CO₃, Na₄P₂O₇, and NaCl–Na₄P₂O₇ (highest). Na₄P₂O₇ was the most efficient extractant that induced the release of primary nanomaterials from microaggregates. Although sodium carbonate extracted relatively high concentrations of nanomaterials, the extracted nanomaterials occurred mainly as aggregates of primary nanomaterials. Ultrapure water, sodium chloride and acetic acid resulted in poor nanomaterial extraction and broad size distributions. Elemental ratios illustrate that Ti is associated with Nb, Ta, and V, and that Ce is associated with rare earth elements such as La, Eu, Y, Ho, Er, Tm, and Yb. Our findings indicate that size, size distribution, and elemental ratios can be used as fingerprints to differentiate engineered nanomaterials such as TiO₂ and CeO₂ from natural nanomaterials in complex media.

中文翻译：

---

如何区分天然材料与工程纳米材料：土壤中TiO 2和CeO 2分析的见解

摘要

TiO ₂和CeO ₂等工程纳米材料的数量不断增加被释放到空气，水，土壤和沉积物中。但是，评估那些纳米材料的人为来源是相当困难的，因为富含Ti和Ce的颗粒自然存在于土壤和沉积物中，其浓度通常比工程纳米材料的估计浓度高得多。另外，纳米颗粒与环境颗粒的相互作用和聚集使分析变得复杂。因此，需要更多有关天然纳米材料特性的知识来区分天然系统中的工程纳米材料。在这里，我们用六种萃取剂萃取了土壤纳米材料，并将其回收率和分解率与初级颗粒进行了比较。通过动态光散射对纳米材料的流体动力学直径和ζ电势进行了表征，场流分馏与电感耦合等离子体质谱联用的基于尺寸的元素分布，以及透射电子显微镜的形貌。结果表明，纳米材料的浓度从甲烷中增加₃ COOH–NaCl–水（最低），至水或NaCl–水，Na ₂ CO ₃，Na ₄ P ₂ O ₇和NaCl–Na ₄ P ₂ O ₇（最高）。钠₄ P ₂ O ₇是最有效的提取剂，可诱导微团聚体释放初级纳米材料。尽管碳酸钠提取出相对较高浓度的纳米材料，但提取出的纳米材料主要以初级纳米材料的聚集体形式出现。超纯水，氯化钠和乙酸导致不良的纳米材料提取和较宽的尺寸分布。元素比说明Ti与Nb，Ta和V相关，而Ce与稀土元素如La，Eu，Y，Ho，Er，Tm和Yb相关。我们的发现表明，大小，大小分布和元素比率可用作指纹，以区分复杂介质中的TiO ₂和CeO ₂等工程纳米材料与天然纳米材料。