The nanoparticles of TiO₂ (TiO₂ NP) have been used as a plant-growth stimulant or catalyst in pesticide formulas. However, due to high resistance of TiO₂ NP to abiotic weathering, dissolved Ti is unlikely to act as an active compound in these preparations. Even if soil is acidic, TiO₂ NP do not dissolve easily and preferably remain as undissolved particles. The low dissolution rates of inorganic nanoparticles in the soil environment make Ti in TiO₂ NP largely unavailable for plants and soil microorganisms. To characterize the behavior of TiO₂ NP in soil under different pH conditions, we analyzed TiO₂ NP-size distribution in two soil materials, an alkaline and acidic one. We also cultivated Aspergillus niger, a fungus ubiquitously found in soils, in the growth medium spiked with TiO₂ NP to assess accumulation of the nanoparticles in fungus. In soil suspensions, the dissolved Ti was present in low concentrations (up to 0.010 mg L⁻¹). Most of the TiO₂ NP remained in particulate form or appeared as aggregates sized 100–450 nm. In experiment on Ti accumulation by A. niger, TiO₂ NP either settled down to the bottom of the flask with growth medium or were actually accumulated by the fungus; about 7.5% of TiO₂ NP were accumulated in fungal mycelia. Most of the TiO₂ NP remain in particulate form in soil solutions, regardless of soil pH. Filamentous fungus A. niger has the ability to accumulate bioavailable TiO₂ NP, which hints at the possibility that some soil fungi can affect spatial distribution of this type of nanoparticles in soils.

中文翻译：

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TiO2纳米颗粒在酸性和碱性土壤中的分布及其在黑曲霉中的积累

TiO ₂（TiO ₂ NP）的纳米颗粒已被用作农药配方中的植物生长刺激剂或催化剂。但是，由于TiO ₂ NP对非生物风化具有很高的抵抗力，因此溶解的Ti在这些制剂中不太可能充当活性化合物。即使土壤是酸性的，TiO ₂ NP也不易溶解，并且优选以未溶解的颗粒形式保留。无机纳米颗粒在土壤环境中的低溶解度使TiO ₂ NP中的Ti大大不适用于植物和土壤微生物。为了表征不同pH条件下土壤中TiO ₂ NP的行为，我们分析了TiO ₂NP大小分布在两种土壤物质中，一种是碱性物质，另一种是酸性物质。我们还在掺有TiO ₂ NP的生长培养基中培养了黑曲霉（一种在土壤中普遍发现的真菌），以评估纳米颗粒在真菌中的积累。在土壤悬浮液中，溶解的Ti含量低（最高0.010 mg L ^-1）。大多数TiO ₂ NP保持颗粒状或以100-450 nm的聚集体形式出现。在黑曲霉对钛的积累实验中，TiO ₂ NP要么在生长培养基中沉降到烧瓶底部，要么实际上被真菌积累。约7.5％的TiO ₂NP在真菌菌丝体中积累。无论土壤的pH值如何，大多数TiO ₂ NP都以颗粒形式保留在土壤溶液中。丝状真菌黑曲霉具有积累生物利用性TiO ₂ NP的能力，这暗示某些土壤真菌可能会影响这种类型的纳米颗粒在土壤中的空间分布。