Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum Jülich, Wilhelm-Johnen-Str., 52425 Jülich, Germany; Institute for Environmental Research, Biology 5, RWTH Aachen, Worringerweg 1, 52074 Aachen, Germany.
Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg, Wonnhaldestraße 4, 79100 Freiburg i.Br., Germany.
Sci Total Environ. 2018 Sep 1;634:305-315. doi: 10.1016/j.scitotenv.2018.03.265. Epub 2018 Apr 6.
The leaching of P from the upper 20cm of forest topsoils influences nutrient (re-)cycling and the redistribution of available phosphate and organic P forms. However, the effective leaching of colloids and associated P forms from forest topsoils was so far sparsely investigated. We demonstrated through irrigation experiments with undisturbed mesocosm soil columns, that significant proportions of P leached from acidic forest topsoils were associated with natural colloids. These colloids had a maximum size of 400nm. By means of Field-flow fractionation the leached soil colloids could be separated into three size fractions. The size and composition was comparable to colloids present in acidic forest streams known from literature. The composition of leached colloids of the three size classes was dominated by organic carbon. Furthermore, these colloids contained large concentrations of P which amounted between 12 and 91% of the totally leached P depending on the type of the forest soil. The fraction of other elements leached with colloids ranged between 1% and 25% (Fe: 1-25%; C: 3-17%; Al: <4%; Si, Ca, Mn: all <2%). The proportion of colloid-associated P decreased with increasing total P leaching. Leaching of total and colloid-associated P from the forest surface soil did not increase with increasing bulk soil P concentrations and were also not related to tree species. The present study highlighted that colloid-facilitated P leaching can be of higher relevance for the P leaching from forest surface soils than dissolved P and should not be neglected in soil water flux studies.
从上覆 20cm 的森林表土中浸出的磷会影响养分（再）循环和有效磷和有机磷形态的再分布。然而，森林表土中胶体和相关磷形态的有效浸出作用迄今研究甚少。我们通过用原状中柱进行灌溉实验证明，从酸性森林表土中浸出的相当大比例的磷与天然胶体有关。这些胶体的最大尺寸为 400nm。通过现场流动分级，可以将淋滤的土壤胶体分离成三个大小级分。淋滤胶体的大小和组成与文献中已知的酸性森林溪流中的胶体相似。淋滤的三个粒径级分的胶体组成主要由有机碳组成。此外，这些胶体含有大量的磷，其浓度占总淋出磷的 12%至 91%，具体取决于森林土壤的类型。与胶体一起淋滤的其他元素的浓度范围为 1%至 25%（Fe：1-25%；C：3-17%；Al：<4%；Si、Ca、Mn：均<2%）。随着总磷淋出量的增加，胶体结合磷的比例下降。从森林表土中淋出的总磷和胶体结合磷的量与土壤总磷浓度的增加无关，也与树种无关。本研究强调，胶体促进的磷淋失对森林表土中磷的淋失可能比溶解磷更为重要，在土壤水通量研究中不应忽视。
