Abstract. Long-term excessive application of mineral fertilizer leads to accumulation of phosphorus (P) in lime concretion black soil, which increases the risk of P migration and loss from soil profile. The colloids in the profile are important carriers for P migration due to high P adsorption and transport capacity. In this study, water extractable colloids (WECs) were obtained from 0 ~ 120 cm soil profile by soil fractionation method, and their physicochemical properties were analyzed. Solution 31P nuclear magnetic resonance (NMR) and P K-edge XANES were used to characterize the species and distribution of colloidal P in fertilized farmland soil profile. Total and available P in bulk soil and colloids decreased with soil depth. The organic P (OP) contained ~97 to 344 mg kg^-1 per bulk soil and 110–630 mg/kg per WECs in soil profile with composition of orthophosphate monoesters and diesters according to NMR results. It suggested that OP in WECs from subsoils might be affected by the translocation of colloidal P (CP) from surface soils probably due to soil acidification and preferential flow caused by swelling-shrinkage clays including montmorillonite and nontronite. Additionally, the more negative zeta potential of surface soil colloids suggests the high mobility of colloidal P to the subsoils. The CP concentrations for <2 µm was about 38–93 mg/kg per bulk soil, which is 6–37 folds of dissolved reactive P (DRP) concentrations, suggesting that the role of CP for P transport in the soil profile is dominated. This study showed that inorganic and organic P migrated from surface to deeper layer along the lime concretion black soil profile, with soil colloids having a significant effect on P migration from both surface and subsurface layers. The results have an important significance for soil P migration evaluation and agricultural non-point source pollution control in lime concretion black soil.

中文翻译：

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集约化农业管理诱导石灰结核黑土中水溶性胶体磷的地下积累

摘要。长期过量施用矿物肥料会导致石灰结核黑土中磷 (P) 的积累，从而增加磷从土壤剖面迁移和流失的风险。由于高磷吸附和运输能力，剖面中的胶体是磷迁移的重要载体。本研究采用土壤分级分离法从 0 ~ 120 cm 土壤剖面中提取水可提取胶体 (WECs)，并对其理化性质进行了分析。溶液31P核磁共振（NMR）和P K-edge XANES用于表征施肥农田土壤剖面中胶体P的种类和分布。大块土壤和胶体中的总磷和速效磷随着土壤深度的增加而降低。有机磷 (OP) 含有 ~97 至 344 mg kg ^-1根据核磁共振结果，每个大块土壤和 110-630 mg/kg 每个 WECs 在具有正磷酸单酯和二酯组成的土壤剖面中。这表明来自底土的 WEC 中的 OP 可能受到来自表层土壤的胶体 P (CP) 易位的影响，这可能是由于土壤酸化和由膨胀收缩粘土（包括蒙脱石和脱脱石）引起的优先流动。此外，表层土壤胶体的更负 zeta 电位表明胶体 P 到底土的高流动性。<2 µm 的 CP 浓度约为每块土壤 38-93 mg/kg，是溶解活性磷 (DRP) 浓度的 6-37 倍，表明 CP 在土壤剖面中对磷运输的作用占主导地位。这项研究表明，无机和有机磷沿着石灰结核黑土剖面从表层迁移到深层，土壤胶体对磷从表层和地下层的迁移有显着影响。研究结果对石灰结核黑土土壤磷迁移评价和农业面源污染控制具有重要意义。