Towards a better understanding of the origin and fate of fine colloidal and dissolved black carbon in agro-ecosystems

更好地了解农业生态系统中细粒胶体和溶解黑碳的起源和命运

• 批准号: 336943844
• 负责人: Dr. Melanie Braun
• 金额: --
• 依托单位: Arbeitsgruppe Bodenkunde und Bodenökologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/336943844?language=en
• 关键词: Towards; better; understanding; origin; fate

Black carbon (BC) comprises a variety of organic combustion residues, which enter the soil by atmospheric deposition, e.g. from vegetation fires and/or by direct application of BC in form of biochar. Black C is highly recalcitrant and hence accumulates in soil within several decades. However, the degradation and loss of BC in soil is hardly understood. In the last years several studies showed that BC occurs in water in the form of dissolved BC (DBC), which includes particles < 450 nm. Though, a direct evidence for loss of BC from soil in form of water extractable BC (WEBC) to this dissolved fraction is missing. I hypothesize that i) a large part of BC in arable soils exists in water-transportable form (WEBC), and that ii) WEBC consist mainly of colloidal to nano-sized particles, which can be characterized via analytical and preparative field flow fractionation (FFFprep). Besides, I assume that this WEBC is produced by microbial BC degradation. To test these hypotheses, I will first investigate arable soils from field experiments with different BC inputs on their WEBC content and composition (0, 4.5 and 9 t biochar/ha applied with compost to coppice plantations). WEBC will be extracted from soil and filtrated to < 450 nm prior to BC analyses (oxidation to benzene polycarboxylic acids (BPCA method). Secondly, for the determination of BC abundance in colloidal- to nano-size classes an FFFprep method will be established and later on optimized for preparative isolation of BC particles. These can then be used for subsequent analysis of BPCAs, which serve as marker for the degree of aromatic condensation. To elucidate the contribution of microbial BC degradation to WEBC formation, samples of a 5-year incubation experiment (including sterile and non-sterile variants) are characterized by FFFprep and subsequent BPCA analyses. These experiments will first time investigate the size distribution of WEBC in soil and to which degree it will change during degradation. This study will further reveal if biochar application rates correlate with WEBC in soil. I will then be able to provide first ideas if degradation of BC to fine-colloidal and nanoparticles might be relevant for BC losses from soil and the global carbon cycle at least in decadal time-scales.

黑碳（BC）包括各种有机燃烧残留物，其通过大气沉积进入土壤，例如来自植被火灾和/或通过以生物炭形式直接施用BC。黑C是高度可吸收的，因此在几十年内积累在土壤中。然而，BC在土壤中的降解和损失还不清楚。在过去的几年中，一些研究表明，BC以溶解BC（DBC）的形式存在于水中，其中包括< 450 nm的颗粒。然而，缺乏直接证据证明土壤中的BC以水可提取BC（WEBC）的形式流失到这种溶解部分。我假设，i）在耕地土壤中的BC的很大一部分存在于水传输的形式（WEBC），和ii）WEBC主要由胶体到纳米尺寸的颗粒，其特征在于通过分析和制备场流分级（FFFprep）。此外，我假设这种WEBC是由微生物BC降解产生的。为了验证这些假设，我将首先调查耕地土壤从田间实验与不同的BC输入其WEBC含量和组成（0，4.5和9吨生物炭/公顷堆肥应用于矮林种植园）。将从土壤中提取WEBC，并在BC分析前过滤至< 450 nm（氧化为苯多羧酸（BPCA法））。其次，为了测定胶体至纳米级的BC丰度，将建立FFFprep方法，并随后优化BC颗粒的制备分离。然后，这些可用于随后的BPCA分析，BPCA用作芳族缩合程度的标志。为了阐明微生物BC降解对WEBC形成的贡献，通过FFFprep和随后的BPCA分析表征了5年孵育实验的样品（包括无菌和非无菌变体）。这些实验将首次调查WEBC在土壤中的粒度分布以及在降解过程中的变化程度。本研究将进一步揭示生物炭施用量与土壤WEBC的相关性。然后，我将能够提供第一个想法，如果BC降解为细胶体和纳米颗粒可能是相关的BC损失从土壤和全球碳循环至少在十年的时间尺度。