School of Plant and Environmental Sciences, Virginia Polytechnic Institute, 185 Ag Quad Lane, Blacksburg, VA, 24061, USA.
Department of Ecology, University of Innsbruck, Sternwartestraße 15A-6020, Innsbruck, Austria.
Sci Rep. 2022 Mar 11;12(1):4261. doi: 10.1038/s41598-022-08241-w.
Preferential flow reduces water residence times and allows rapid transport of pollutants such as organic contaminants. Thus, preferential flow is considered to reduce the influence of soil matrix-solute interactions during solute transport. While this claim may be true when rainfall directly follows solute application, forcing rapid chemical and physical disequilibrium, it has been perpetuated as a general feature of solute transport-regardless of the magnitude preferential flow. A small number of studies have alternatively shown that preferential transport of strongly sorbing solutes is reduced when solutes have time to diffuse and equilibrate within the soil matrix. Here we expand this inference by allowing solute sorption equilibrium to occur and exploring how physiochemical properties affect solute transport across a vast range of preferential flow. We applied deuterium-labeled rainfall to field plots containing manure spiked with eight common antibiotics with a range of affinity for the soil after 7 days of equilibration with the soil matrix and quantified preferential flow and solute transport using 48 soil pore water samplers spread along a hillslope. Based on > 700 measurements, our data showed that solute transport to lysimeters was similar-regardless of antibiotic affinity for soil-when preferential flow represented less than 15% of the total water flow. When preferential flow exceeded 15%, however, concentrations were higher for compounds with relatively low affinity for soil. We provide evidence that (1) bypassing water flow can select for compounds that are more easily released from the soil matrix, and (2) this phenomenon becomes more evident as the magnitude of preferential flow increases. We argue that considering the natural spectrum preferential flow as an explanatory variable to gauge the influence of soil matrix-solute interactions may improve parsimonious transport models.
优先流会减少水的停留时间，并允许污染物（如有机污染物）快速传输。因此，优先流被认为会降低溶质传输过程中土壤基质-溶质相互作用的影响。虽然当降雨直接紧随溶质施加时，这种说法可能是正确的，因为它会迫使化学和物理迅速达到不平衡状态，但它被认为是溶质传输的一个普遍特征，而不管优先流的程度如何。少数研究表明，当溶质有时间在土壤基质中扩散和达到平衡时，强吸附溶质的优先传输会减少。在这里，我们通过允许溶质吸附平衡发生，并探索物理化学性质如何影响跨越广泛优先流范围的溶质传输，扩展了这一推断。我们将氘标记的降雨应用于含有经过 7 天与土壤基质平衡后的粪肥和 8 种常见抗生素的田间小区，并使用沿山坡分布的 48 个土壤孔隙水采样器来量化优先流和溶质传输。基于超过 700 次测量，我们的数据表明，当优先流小于总水流的 15%时，无论抗生素对土壤的亲和力如何，溶质向淋溶器的传输都是相似的。然而，当优先流超过 15%时，对土壤亲和力相对较低的化合物的浓度会更高。我们提供的证据表明：(1) 旁路水流可以选择更易于从土壤基质中释放的化合物；(2) 随着优先流幅度的增加，这种现象变得更加明显。我们认为，考虑自然谱优先流作为解释变量来衡量土壤基质-溶质相互作用的影响，可能会改进简约的传输模型。
