Priming of Soil Carbon Decomposition in Two Inner Mongolia Grassland Soils following Sheep Dung Addition: A Study Using ¹³C Natural Abundance Approach

<div><p>To investigate the effect of sheep dung on soil carbon (C) sequestration, a 152 days incubation experiment was conducted with soils from two different Inner Mongolian grasslands, <i>i.e.</i> a <i>Leymus chinensis</i> dominated grassland representing the climax community (2.1% organic matter content) and a heavily degraded <i>Artemisia frigida</i> dominated community (1.3% organic matter content). Dung was collected from sheep either fed on <i>L. chinensis</i> (C₃ plant with δ¹³C = −26.8‰; dung δ¹³C = −26.2‰) or <i>Cleistogenes squarrosa</i> (C₄ plant with δ¹³C = −14.6‰; dung δ¹³C = −15.7‰). Fresh C₃ and C₄ sheep dung was mixed with the two grassland soils and incubated under controlled conditions for analysis of ¹³C-CO₂ emissions. Soil samples were taken at days 17, 43, 86, 127 and 152 after sheep dung addition to detect the δ¹³C signal in soil and dung components. Analysis revealed that 16.9% and 16.6% of the sheep dung C had decomposed, of which 3.5% and 2.8% was sequestrated in the soils of <i>L. chinensis</i> and <i>A. frigida</i> grasslands, respectively, while the remaining decomposed sheep dung was emitted as CO₂. The cumulative amounts of C respired from dung treated soils during 152 days were 7–8 times higher than in the un-amended controls. In both grassland soils, ca. 60% of the evolved CO₂ originated from the decomposing sheep dung and 40% from the native soil C. Priming effects of soil C decomposition were observed in both soils, <i>i.e.</i> 1.4 g and 1.6 g additional soil C kg⁻¹ dry soil had been emitted as CO₂ for the <i>L. chinensis</i> and <i>A. frigida</i> soils, respectively. Hence, the net C losses from <i>L. chinensis</i> and <i>A. frigida</i> soils were 0.6 g and 0.9 g C kg⁻¹ soil, which was 2.6% and 7.0% of the total C in <i>L. chinensis</i> and <i>A. frigida</i> grasslands soils, respectively. Our results suggest that grazing of degraded Inner Mongolian pastures may cause a net soil C loss due to the positive priming effect, thereby accelerating soil deterioration.</p></div

Fates of soil and sheep dung carbon after 152

a<p>Net soil C loss was given by the value of sheep dung C sequestrated in the soil during 152 days subtracted from the primed soil CO₂.</p>b<p>Soil C loss (%) is the percentage total CO₂-C loss compared to soil total organic C content.</p

Temporal dynamics of δ¹³C (‰ vs VPDB) signatures in CO₂ emitted during 152 days following sheep dung addition to <i>L. chinensis</i> and <i>A. frigida</i> soil (n = 3).

<p>Temporal dynamics of δ¹³C (‰ vs VPDB) signatures in CO₂ emitted during 152 days following sheep dung addition to <i>L. chinensis</i> and <i>A. frigida</i> soil (n = 3).</p

The relative contribution of dung-derived CO₂-C and soil-derived CO₂-C during 152 days incubation calculated from the δ¹³ C signature of CO₂ after sheep dung addition (n = 3).

<p>The relative contribution of dung-derived CO₂-C and soil-derived CO₂-C during 152 days incubation calculated from the δ¹³ C signature of CO₂ after sheep dung addition (n = 3).</p

Two Unprecedented Transition-Metal–Organic Frameworks Showing One Dimensional-Hexagonal Channel Open Network and Two-Dimensional Sheet Structures

Two new metal–organic frameworks, {[Co₃(μ₃-DMPhIDC)₂(H₂O)₆]·2H₂O}_<i>n</i> (<b>1</b>) and {[Mn₅(μ₃-DMPhIDC)₂(μ₂-HDMPhIDC)₂(Phen)₅]·2CH₃OH·3H₂O}_<i>n</i> (<b>2</b>) (H₃DMPhIDC = 2-(3,4-dimethylphenyl)-1<i>H</i>-imidazole-4,5-dicarboxylic acid, Phen = 1,10-phenanthroline), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses, X-ray powder diffraction (XRPD), thermal analyses, and IR spectra. Polymer <b>1</b> is an enchanting three-dimensional network containing infinite one-dimensional-hexagonal channels and [Co₂(DMPhIDC)]₆ cages, which have two interpenetrating nets topology. Polymer <b>2</b> exhibits a two-dimensional framework, which is composed of left- and right-handed helices pillared by Mn²⁺ linkages. Antiferromagnetic coupling exists between the Co­(II) ions or Mn­(II) ions in <b>1</b> or <b>2</b>, respectively

Two Unprecedented Transition-Metal–Organic Frameworks Showing One Dimensional-Hexagonal Channel Open Network and Two-Dimensional Sheet Structures

Two new metal–organic frameworks, {[Co₃(μ₃-DMPhIDC)₂(H₂O)₆]·2H₂O}_<i>n</i> (<b>1</b>) and {[Mn₅(μ₃-DMPhIDC)₂(μ₂-HDMPhIDC)₂(Phen)₅]·2CH₃OH·3H₂O}_<i>n</i> (<b>2</b>) (H₃DMPhIDC = 2-(3,4-dimethylphenyl)-1<i>H</i>-imidazole-4,5-dicarboxylic acid, Phen = 1,10-phenanthroline), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses, X-ray powder diffraction (XRPD), thermal analyses, and IR spectra. Polymer <b>1</b> is an enchanting three-dimensional network containing infinite one-dimensional-hexagonal channels and [Co₂(DMPhIDC)]₆ cages, which have two interpenetrating nets topology. Polymer <b>2</b> exhibits a two-dimensional framework, which is composed of left- and right-handed helices pillared by Mn²⁺ linkages. Antiferromagnetic coupling exists between the Co­(II) ions or Mn­(II) ions in <b>1</b> or <b>2</b>, respectively

Dissolution-Dictated Recrystallization in Cesium Lead Halide Perovskites and Size Engineering in δ‑CsPbI₃ Nanostructures

Crystal strain, crystal size, and reactivity with surrounding species underlie the thermal stability of the photoactive γ-CsPbI3 in theoretical and practical perspectives. The spontaneous transformation of optically γ-CsPbI3 nanocrystals (NCs) to inactive δ-CsPbI3 nanostructures (NSs) hinders the development of the fabrication of efficient photovoltaic devices. To understand this process, we conducted a comprehensive investigation on the phase transformation kinetics and the nucleation and growth of δ-CsPbI3 NSs from γ-CsPbI3 NCs (∼8 nm) in a stepwise manner. The reaction scheme involved independently carrying out reactions where the γ-CsPbI3 NCs reacted with optimized amounts of aprotic polar solvent (acetone), which leads to dissolution followed by a recrystallization process at solvent interfaces (acetone/hexane) to observe even the early changes in this process. Interestingly, the γ-CsPbI3 NCs during dissolution in acetone enable the release of PbI2 NCs, eventually leading to changes in crystal phase, size, and shape of the NCs. As a result, we observed unique absorption spectra and multiple emission features that enable white light emission. In contrast to the previously explored phase transformation process (γ-CsPbI3 to δ-CsPbI3 NSs) observed in larger-sized γ-CsPbI3 NCs (∼18 nm), which occurs through an oriented self-assembly process when the NCs come in contact with polar solvents, in our two-step solvent introduction procedure, the γ-CsPbI3 NCs first transform into zero-dimensional Cs4PbI6 NCs by their dissolution in acetone. Depending on the rate of dissolution which is proportional to the amounts of supplied acetone, the reaction solution can result in Cs4PbI6 NCs, γ-CsPbI3 NCs, or δ-CsPbI3 NSs during the recrystallization process. Furthermore, our investigations provided insights into this phase transition mechanism governed by the seeded growth phenomenon. This research facilitates enhanced control over undesired transitions, thereby promoting the development of refined and uncomplicated methodologies for recycling stable γ-CsPbI3 NCs

Temporal dynamics of CO₂ fluxes (mg C kg^–1 day^–1) (A and B), and cumulative CO₂-C loss (mg C kg^–1 day^–1) (C and D) during 152 days of incubation of <i>L. chinensis</i> and <i>A. frigida</i> soils amended with C₃ and C₄ dung.

<p>Values are the mean (n = 3) ± SE (bars).</p

Characteristics of sheep dung used in the incubation study. Dung was collected from sheep either fed on L. <i>chinensis</i> (C₃ dung) or C. <i>squarrosa</i> (C₄ dung).

a<p>The content based on 60g fresh dung portions as applied in the experiment.</p>b<p>Numbers are mean ± SE of n = 3 replicates.</p

Primed CO₂ emission (mg C kg⁻¹ day⁻¹) during 152 days of incubation from sheep dung amended <i>L. chinensis</i> and <i>A. frigida</i> soils.

<p>The numbers indicate soil C derived CO₂ emitted in excess to the control soil (n = 3).</p