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Determination of the calcium species in coal chars by Ca k-edge xanes analysis

Chinese Physics C 2013年第2期37卷 102-104页

作者：刘利娟刘慧君崔明启胡永峰郑雷赵屹东马陈燕席识博杨栋亮郭志英王杰 Institute of High Energy Physics Chinese Academy of Sciences Department of Chemical Engineering for Energy East China University of Science and Technology Canadian Light Source University of Saskatchewan

Ca-based additives have been widely used as a sulfur adsorbent during coal pyrolysis and gasification. The Ca speciation and evolution during the pyrolysis of coal with Ca additives have attracted great attention. In this paper, Ca species in the coal chars prepared from the pyrolysis of Ca（OH）2 or CaCO3-added coals are studied by using Ca k-edge X-ray absorption near-edge structural spectroscopy. The results demonstrate that Ca（OH）2 , CaSO4 , CaS and CaO coexist in the Ca（OH）2-added chars, while Ca（OH）2 and CaSO4 are the main species in the Ca（OH）2-added chars. Besides, a carboxyl-bound Ca is also formed during both the pyrolysis for the Ca（OH）2-added and the CaCO3-added coals. A detailed discussion about the Ca speciation is given.

关键词： char pyrolysis calcium k-edge xanes

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Long-term straw addition promotes moderately labile phosphorus formation, decreasing phosphorus downward migration and loss in greenhouse vegetable soil

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Journal of Integrative Agriculture 2022年第9期21卷 2734-2749页

作者： ZHANG Yin-jie GAO Wei LUAN Hao-an TANG Ji-wei LI Ruo-nan LI Ming-yue ZHANG Huai-zhi HUANG Shao-wen key Laboratory of Plant Nutrition and Fertilizer Ministry of Agriculture and Rural Affairs/Institute of Agricultural Resources and Regional PlanningChinese Academy of Agricultural SciencesBeijing 100081P.R.China Institute of Agricultural Resources and Environment Tianjin Academy of Agricultural SciencesTianjin 300192P.R.China College of Forestry Hebei Agricultural UniversityBaoding 071000P.R.China Institute of Agricultural Resources and Environment Hebei Academy of Agriculture and Forestry SciencesShijiazhuang 050051P.R.China

Phosphorus(P) leaching is a major problem in greenhouse vegetable production with excessive P fertilizer application. Substitution of inorganic P fertilizer with organic fertilizer is considered a potential strategy to reduce leaching, but the effect of organic material addition on soil P transformation and leaching loss remains unclear. The X-ray absorption nearedge structure(xanes) spectroscopy technique can determine P speciation at the molecular level. Here, we integrated xanes and chemical methods to explore P speciation and transformation in a 10-year field experiment with four treatments: 100% chemical fertilizer(4 CN), 50% chemical N and 50% manure N(2CN+2MN), 50% chemical N and 50% straw N(2CN+2SN), and 50% chemical N and 25% manure N plus 25% straw N(2CN+2 MSN). Compared with the 4 CN treatment, the organic substitution treatments increased the content of labile P by 13.7–54.2% in the 0–40 cm soil layers, with newberyite and brushite being the main constituents of the labile P. Organic substitution treatments decreased the stable P content;hydroxyapatite was the main species and showed an increasing trend with increasing soil depth. Straw addition(2CN+2SN and 2CN+2 MSN) resulted in a higher moderately labile P content and a lower labile P content in the subsoil(60–100 cm). Moreover, straw addition significantly reduced the concentrations and amounts of total P, dissolved inorganic P(DIP), and particulate P in leachate. DIP was the main form transferred by leaching and co-migrated with dissolved organic carbon. Partial least squares path modeling revealed that straw addition decreased P leaching by decreasing labile P and increasing moderately labile P in the subsoil. Overall, straw addition is beneficial for developing sustainable P management strategies due to increasing labile P in the upper soil layer for the utilization of plants, and decreasing P migration and leaching.

关键词： k-edge xanes phosphorus speciation leaching losses sustainable phosphorus management greenhouse vegetable production

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