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Evaluating biodegradability of soil organic matter by its thermal stability and chemical composition
The stability of soil organic matter (SOM) as it relates to resistance to microbial degradation has important implications for nutrient cycling, emission of greenhouse gases, and C sequestration. Hence, there is interest in developing new ways to quantify and characterise the labile and stable forms of SOM. Our objective in this study was to evaluate SOM under widely contrasting management regimes to determine whether the variation in chemical composition and resistance to pyrolysis observed for various constituent C fractions could be related to their resistance to decomposition. Samples from the same soil under permanent pasture, an arable cropping rotation, and chemical fallow were physically fractionated (sand: 2000-50 μm; silt: 50-5 μm, and clay: <5 μm). Biodegradability of the SOM in size fractions and whole soils was assessed in a laboratory mineralization study. Thermal stability was determined by analytical pyrolysis using a Rock-Eval pyrolyser, and chemical composition was characterized by X-ray absorption near-edge structure (XANES) spectroscopy at the C and N K-edges. Relative to the pasture soil, SOM in the arable and fallow soils declined by 30% and 40%, respectively. The mineralization bioassay showed that SOM in whole soil and soil fractions under fallow was less susceptible to biodegradation than that in other management practices. The SOM in the sand fraction was significantly more biodegradable than that in the silt or clay fractions. Analysis by XANES showed a proportional increase in carboxylates and a reduction in amides (protein) and aromatics in the fallow whole soil compared to the pasture and arable soils. Moreover, protein depletion was greatest in the sand fraction of the fallow soil. Sand fractions in fallow and arable soils were, however, relatively enriched in plant-derived phenols, aromatics, and carboxylates compared to the sand fraction of pasture soils. Analytical pyrolysis showed distinct differences in the thermal stability of SOM among the whole soil and their size fractions; it also showed that the loss of SOM generally involved preferential degradation of H-rich compounds. The temperature at which half of the C was pyrolyzed was strongly correlated with mineralizable C, providing good evidence for a link between the biological and thermal stability of SOM. 相似文献
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Litter is one of the main sources of dissolved organic carbon (DOC) in forest soils and litter decomposition is an important control of carbon storage and DOC dynamics. The aim of our study was to evaluate (i) effects of tree species on DOC production and (ii) relationships between litter decomposition and the amount and quality of DOC. Five different types of leaves and needles were exposed in litterbags at two neighboring forest sites. Within 12 months we sampled the litterbags five times and leached aliquots of field moist litter in the laboratory. In the collected litter percolates we measured DOC concentrations and recorded UV and fluorescence spectra in order to estimate the aromaticity and complexity of the organic molecules. Furthermore, we investigated the biodegradability of DOC from fresh and decomposed litter during 6 weeks incubations. Fresh sycamore maple litter released the largest amounts of DOC reaching about 6.2% of litter C after applying precipitation of 94 mm. We leached 3.9, 1.6, 1.0 and 3.3% carbon from fresh mountain ash, beech, spruce and pine litter, respectively. In the initial phase of litter decomposition significantly decreasing DOC amounts were released with increasing litter mass loss. However, after mass loss exceeds 20% DOC production from needle litter tended to increase. UV and fluorescence spectra of percolates from pine and spruce litter indicated an increasing degree of aromaticity and complexity with increasing mass loss as often described for decomposing litter. However, for deciduous litter the relationship was less obvious. We assume that during litter decomposition the source of produced DOC in coniferous litter tended toward a larger contribution from lignin-derived compounds. Biodegradability of DOC from fresh litter was very high, ranging from 30 to 95% mineralized C. DOC from degraded litter was on average 34% less mineralizable than DOC from fresh litter. Taking into account the large DOC production from decomposed needles we can assume there is an important role for DOC in the accumulation of organic matter in soils during litter decomposition particularly in coniferous forests. 相似文献
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F. Murilo T. LunaBreno S. Rocha Estélio M. Rola Jr.Mônica C.G. Albuquerque Diana C.S. AzevedoCélio L. Cavalcante Jr. 《Industrial Crops and Products》2011,33(3):579-583
This study proposes to evaluate rapid methodologies to estimate oxidative stability and biodegradability for mineral, vegetable and synthetic oil samples, using quick and simple experiments. The synthetic oil sample was obtained from castor oil, so the vegetable oil chosen for this evaluation was a sample of the crude castor oil source. The oxidative stability tests described enabled the comparison of synthetic lubricant samples and showed that their stability was lower than that of petroleum-based oil. However, the physico-chemical properties, such pour points and viscosity index, were improved and potentially interesting for lubricant applications. The biodegradability experiments were carried out using a model of bio-kinetics. These studies proved that synthetic lubricant samples were easily degradable (similar to crude castor oil) and showed half-life significantly lower than those of the mineral oil samples. 相似文献
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溶解性有机质在土壤固碳中的意义 总被引：2，自引：2，他引：2
随着全球变暖的加剧,土壤圈作为全球碳循环中的重要碳库受到日益关注。土壤有机碳固定对大气温室效应和气候变暖有重要影响。溶解性有机质(DOM)是土壤中最活跃的有机碳库,其含量与土壤CO2、CH4、N2O的排放显著正相关,DOM的矿化成为土壤有机碳损失的重要途径。DOM可通过与Fe、Al共沉淀、吸附于土壤矿物表面而改变其生物降解性,从而在土壤中稳定和保留下来,对土壤有机碳积累中具有重要贡献。DOM的化学组成和结构特征影响其生物降解性,同时也影响其沉淀吸附效应。其稳定机制不同,对土壤有机碳积累的贡献也存在差异。目前估算DOM对土壤有机碳的贡献尚无普遍认可的方法,具体数值因估算方法不同而存在较大差异,有效的估算方法仍有待于进一步研究。 相似文献
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以玉米秸秆为原料,采用微波液化产物合成可生物降解聚氨酯泡沫,替代传统石化产品多元醇制备聚氨酯泡沫.通过异氰酸根指数及发泡剂水用量对聚氨酯泡沫材料密度、机械性能的影响分析,得到优化的聚氨酯合成工艺条件:水添加量0.30g、异氰酸根指数为1.0;采用土埋法生物降解试验发现,液化产物制备的聚氨酯泡沫在埋置6个月后质量损失约18.71％,热重分析表明合成的聚氨酯泡沫热分解分为4个典型的阶段.试验结果表明玉米秸秆微波液化产物可合成环境友好可生物降解聚氨酯泡沫,但其材料性能有待进一步表征. 相似文献
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[目的]为了研究微生物对不同农用吸水剂的降解作用。[方法]采用无机盐平板筛选法、微生物溶液降解法与称重法。[结果]降解40d,枯草芽孢杆菌对海藻酸钠、魔芋及淀粉接枝农用吸水剂的降解率分别为36.37%、42.00%、54.14%;大肠杆菌对3种吸水剂的降解率分别为34.28%、35.53%、49.57%;大肠杆菌和枯草芽孢杆菌的混合菌对3种吸水剂的降解率分别为37.5%、45.99%、55.65%。[结论]大肠杆菌与枯草芽孢杆菌都具有降解农用吸水剂的作用,降解率与降解时间呈正相关;混合菌的降解作用比单菌体大。 相似文献
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N. SutivisedsakH.N. Cheng M.K. DowdG.W. Selling A. Biswas 《Industrial Crops and Products》2012,36(1):127-134
Polymeric composites based on cotton burr and cottonseed bull have been prepared by melt blending and extrusion. For poly(lactic acid) (PLA) and low-density polyethylene (LDPE), addition of the fillers slightly changed the composite's thermal properties but significantly decreased the composite's mechanical properties. Heat treatment prior to extrusion resulted in composites with better tensile strength and Young's modulus. The use of maleic anhydride and peroxide only slightly improved the physical properties of the LDPE materials, but the effect was less clear for the PLA materials. The PLA-filler composites may be useful for lowering the cost of the materials in applications that can tolerate the decreased properties. In addition, the addition of fillers to LDPE might be beneficial in applications to improve stiffness or to improve biodegradability. 相似文献
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[目的]探讨淀粉的接枝改性对缓释肥包膜材料疏水性及尿素缓释性能的影响。[方法]以吡啶为溶剂,采用硬酯酰氯对淀粉进行接枝改性,并通过流延法制得一系列接枝改性膜。采用元素分析法对所得接枝改性膜的取代度进行分析,采用FT-IR、扫描电镜对其结构形貌进行表征,通过接触角、尿素渗透性及生物降解性等测试对改性膜性能进行分析。[结果]随着接枝取代度的增加,改性膜的接触角迅速增大,达110°以上,疏水性增强。7 d尿素累积渗透率下降,最低达23.6%。接枝改性后,膜材的生物降解速率下降,60 d的降解率由纯淀粉的86.0%降至29.3%。[结论]通过调节反应时间及酰氯与淀粉的添加比例,获得不同缓释性的酰化淀粉膜,以满足不同农作物在不同生长周期对养分的要求。 相似文献
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Biodegradable nanocomposites were prepared by mixing a polymer resin and layered silicates by the melt intercalation method.
Internal structure of the nanocomposite was characterized by using the small angle X-ray scattering (SAXS) and transmission
electron microscope (TEM). Nanocomposites having exfoliated and intercalated structures were obtained by employing two different
organically modified nanoclays. Rheological properties in shear and extensional flows and biodegradability of nanocomposites
were measured. In shear flow, shear thinning behavior and increased storage modulus were observed as the clay loading increased.
In extensional flow, strain hardening behavior was observed in well dispersed system. Nanocomposites with the exfoliated structure
had better biodegradability than nanocomposites with the intercalated structure or pure polymer. 相似文献