Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Aas, Norway.
Sci Total Environ. 2012 Mar 15;420:327-33. doi: 10.1016/j.scitotenv.2012.01.027. Epub 2012 Feb 10.
Sewage sludge application on soils represents an important potential source of silver nanoparticles (Ag NPs) to terrestrial ecosystems, and it is thus important to understand the fate of Ag NPs once in contact with soil components. Our aim was to compare the behavior of three different forms of silver, namely silver nitrate, citrate stabilized Ag NPs (5nm) and uncoated Ag NPs (19nm), in two soils with contrasting organic matter content, and to follow changes in binding strength over time. Soil samples were spiked with silver and left to age for 2h, 2 days, 5 weeks or 10 weeks before they were submitted to sequential extraction. The ionic silver solution and the two Ag NP types were radiolabeled so that silver could be quantified by gamma spectrometry by measuring the (110m)Ag tracer in the different sequential extraction fractions. Different patterns of partitioning of silver were observed for the three forms of silver. All types of silver were more mobile in the mineral soil than in the soil rich in organic matter, although the fractionation patterns were very different for the three silver forms in both cases. Over 20% of citrate stabilized Ag NPs was extractible with water in both soils the first two days after spiking (compared to 1-3% for AgNO(3) and uncoated Ag NPs), but the fraction decreased to trace levels thereafter. Regarding the 19nm uncoated Ag NPs, 80% was not extractible at all, but contrary to AgNO(3) and citrate stabilized Ag NPs, the bioaccessible fraction increased over time, and by day 70 was between 8 and 9 times greater than that seen in the other two treatments. This new and unexpected finding demonstrates that some Ag NPs can act as a continuous source of bioaccessible Ag, while AgNO(3) is rapidly immobilized in soil.
污水污泥在土壤中的应用代表了银纳米粒子（Ag NPs）向陆地生态系统的一个重要潜在来源，因此了解 Ag NPs 一旦与土壤成分接触后的归宿非常重要。我们的目的是比较三种不同形式的银，即硝酸银、柠檬酸稳定的 Ag NPs（5nm）和未涂层的 Ag NPs（19nm），在两种具有不同有机质含量的土壤中的行为，并随着时间的推移跟踪结合强度的变化。土壤样品中加入银，并在老化 2h、2 天、5 周或 10 周后，再进行顺序提取。将离子银溶液和两种 Ag NP 类型进行放射性标记，以便通过测量不同顺序提取部分中的（110m）Ag 示踪剂，通过伽马光谱定量银。观察到三种形式的银的分配模式不同。所有类型的银在矿物质土壤中的移动性都比富含有机质的土壤强，尽管在这两种情况下，三种银形式的分馏模式非常不同。在两种土壤中，稳定化的柠檬酸 Ag NPs 在最初的两天内有超过 20%可被水提取（相比之下，AgNO3 和未涂层的 Ag NPs 的提取率为 1-3%），但此后该分数下降至痕量水平。对于 19nm 的未涂层 Ag NPs，有 80%根本不可提取，但与 AgNO3 和柠檬酸稳定的 Ag NPs 相反，生物可利用部分随时间增加，到第 70 天，比其他两种处理高 8-9 倍。这一新颖而意外的发现表明，一些 Ag NPs 可以作为生物可利用银的连续来源，而 AgNO3 则迅速被土壤固定。
