Faculty of Agrobioengineering and Animal Husbandry, Siedlce University of Natural Sciences and Humanities, B. Prusa 14 St., 08-110 Siedlce, Poland.
Int J Environ Res Public Health. 2023 Jan 29;20(3):2367. doi: 10.3390/ijerph20032367.
The aim of this study was to assess the transformation of organic matter in organic soils undergoing a phase of secondary transformation, based on a new method of nitrogen compound fractionation. Laboratory tests were carried out for 31 layers of muck (after secondary transformation) and peat (parent material of the soil) of drained organic soils (peat). The new method consists of sequential extraction in the following steps: (1) 0.5 M KSO (extraction at room temperature); (2) 0.25 M HSO (hot hydrolysis) (3) 3.0 M HSO (hot hydrolysis); and (4) concentrated HSO (mineralization of the post-extraction residue). As a result of the extraction process, the following fractions (operating forms) were obtained: mineral nitrogen (Nmin), dissolved organic nitrogen (N-DON), readily hydrolyzing organic nitrogen (N-RH), non-readily hydrolyzing organic nitrogen (N-NRH), and non-hydrolyzing organic nitrogen (N-NH). The study demonstrates the usefulness of the applied method for assessing the degree of secondary transformation of drained organic soils. The obtained results of nitrogen fractionation indicate the significant dynamics of nitrogen forms' transformations and a significant relationship between these forms and soil properties. Nitrogen transformation processes during the secondary transformation process after dehydration resulted in an increase in the share of N-DON (on average: 1.47% of N for the peat layers and 2.97% of Norg for the muck layers) and in an increase in the share of N (on average: 20.7% of Norg for the peat layers and 33.5% of Norg for the muck layers). The method of sequential nitrogen fractionation used in our study allowed us to define an index determining the degree of transformation of organic matter in peat after drying. We defined it as the ratio of readily hydrolyzable forms (the fraction is very variable in the secondary transformation process) to non-readily hydrolyzable forms (relatively stable fraction in the secondary transformation process): N-RH/N-NRH. The average value of this index was significantly lower in the peat layers (0.64 on average) than in the muck beds (1.04 on average). The value of this index is significantly correlated with soil properties: bulk density (R = 0.470); general porosity (R = 0.503); total carbon content (TC) (R = 0.425); total carbon to total nitrogen ratio (TC/TN) (R = 0.619); and share of carbon of humic substances (C-HS) (R = 0.466). We believe that the method of sequential nitrogen fractionation may be useful for other soils and organic materials.
本研究旨在基于氮化合物分级的新方法评估经历二次转化阶段的有机土壤中有机质的转化。对 31 层（二次转化后的）泥煤和泥炭（土壤母质）进行了实验室测试。新方法包括以下步骤的连续提取：（1）0.5 M KSO（室温提取）；（2）0.25 M HSO（热水解）；（3）3.0 M HSO（热水解）；和（4）浓 HSO（提取后残渣的矿化）。作为提取过程的结果，获得了以下分数（操作形式）：矿质氮（Nmin）、溶解有机氮（N-DON）、易水解有机氮（N-RH）、不易水解有机氮（N-NRH）和非水解有机氮（N-NH）。研究表明，所应用的方法对于评估排水有机土壤的二次转化程度非常有用。氮分级的结果表明，氮形态转化的动态显著，并且这些形态与土壤性质之间存在显著关系。在脱水后的二次转化过程中，氮转化过程导致 N-DON 的份额增加（平均：泥炭层为 1.47% 的 N，泥煤层为 2.97% 的 Norg），N 份额增加（平均：泥炭层为 20.7% 的 Norg，泥煤层为 33.5% 的 Norg）。我们研究中使用的连续氮分级方法使我们能够定义一个指标来确定泥炭在干燥后的有机质转化程度。我们将其定义为易水解形式与不易水解形式的比值（在二次转化过程中，该分数变化非常大）：N-RH/N-NRH。该指标的平均值在泥炭层中明显较低（平均为 0.64），而在泥煤床中较高（平均为 1.04）。该指数的值与土壤性质显著相关：体密度（R = 0.470）；总孔隙度（R = 0.503）；总碳含量（TC）（R = 0.425）；总碳与总氮比（TC/TN）（R = 0.619）；和腐殖物质的碳份额（C-HS）（R = 0.466）。我们认为，连续氮分级方法可能对其他土壤和有机材料有用。
