Characterization of the perylenequinone pigments in Japanese Andosols and Cambisol

The green fraction of humic acid (Pg) and the chloroform-extractable green fraction (CEGF) are characteristic soil organic matter (SOM) components. These alkaline solutions are green-colored due to the presence of 4,9-dihydroxyperylene-3,10-quinone (DHPQ) chromophore. While both of which are potential indicators for the effect of land use and paleoclimatic environment in the fields of soil science as well as geochemistry, CEGF as well as its relationship with Pg in soils are not yet fully documented. In this study, we firstly investigated the chemical properties of soil CEGF fractions by ultraviolet–visible (UV–Vis) and infrared (IR) method. Two CEGF components were separated by sequential liquid-liquid extraction using aqueous ammonium hydroxide (NH₄OH) followed by aqueous sodium hydroxide (NaOH). Results showed that the UV–Vis spectral shape of NH₄OH-extractable component is very similar to that of DHPQ, except that it is red-shifted. The solubility and UV–Vis spectrum of the NaOH-extractable fraction were completely identical with those of synthesized DHPQ. Their IR spectral shapes were also almost the same. Subsequently, the distribution of CEGF in humic acid (HA), fulvic acid (FA) and humin (HN) from Japanese Andosols and Cambisol was quantitatively evaluated by sequential extraction. Most of CEGF was detected in the HA (60–78%) and HN (22–40%), but not in the FA. While the UV–Vis spectral shape of CEGF extracted from Andosols HAs showed a relatively higher proportion of DHPQ than its derivative, the opposite was observed in Cambisol HA, whose CEGF is similar to that of sclerotium grain (one of the possible origin of CEGF). These results suggest the diversity of CEGF-producing soil fungi. Quantitative data also indicated that 35–49% of Pg consisted of a chloroform-soluble fraction (i.e., CEGF) and the remaining 51–65% of Pg was chloroform-insoluble. Based on these results, we propose that CEGF is composed of DHPQ and DHPQ-derivatives and that CEGF is one of the major fractions of Pg.     

Abstracts of Nippon Nojohiryogaku Zasshi

Abstract

P type humic acid which has absorption bands near 615, 570, and 450 run due to the presence of dihydroxyperylenequinone (DHPQ) was investigated by gel-chromatography. Humic acid samples were fractionated using Sephadex G-50 as gel material and 0.1 n NaOH, with or without 1.5 m urea, as eluent. The absorption spectra of the effluent fractions were measured, and elution curves were drawn on the basis of the optical density at 600 nm.

In general, the intensity of the absorption bands due to DHPQ increased with increasing fraction number, accompanied by a change in effluent color from brown, greenish brown to green. Based on the elution curves, the effluent fractions of a humic acid containing a large amount of the green fraction were divided into six groups: B₁, B₂, BG, G₁, G₂, and G₃. These fraction groups, especially the G groups and cercosporin, a dihydroxyperylenequinone pig ment, were compared by absorption spectroscopy, ultrafiltration, ultimate analysis, TLC, and gel-chromatography.

The green fraction was composed of a non-humic, relatively lower-molecular weight polymer containing a considerable amount of DHPQ nucleus, while the brown humic fraction still maintained the characteristic light absorption due to DHPQ. It may be tentatively con cluded that the green fraction is not only a co-extracted impurity, but is also firmly associated with dark-colored humic substances.     

Chemical composition of organic matter in a deep soil changed with a positive priming effect due to glucose addition as investigated by 13C NMR spectroscopy

Fresh organic carbon becomes more accessible to deep soil following losses of surface soil and deep intentional incorporation of crop residues, which can cause the priming effect and influence the quality and quantity of SOC in deep soil. This study determined the priming effect due to addition of water-dissolved ¹³C-labeled glucose (0.4 g C kg⁻¹ soil) to a soil taken from 1.00 to 1.20 m depth. The changes in chemical compositions of SOC in soils without (G₀) and with (G_0.4) glucose addition during a 31-d incubation were investigated with solid-state ¹³C cross polarization/total sideband suppression (¹³C-CP/TOSS) and CP/TOSS with dipolar dephasing nuclear magnetic resonance (NMR) techniques. No glucose remained in the soil after 21 days of incubation, with 48% being completely mineralized into CO₂ emission and 52% being incorporated into SOC. The native SOC was decomposed by 0.23% more in G_0.4 than in G₀. The NMR spectra demonstrated that both labile and recalcitrant organic compounds in SOC changed during the incubation, but in different manners in G₀ and G_0.4. During the incubation, the -(CH₂)_n-abundance in G₀ did not change over time, but in G_0.4 it decreased from Day 0 to Day 21 and then increased from Day 21 to Day 31, suggesting shifts of soil microbial communities only in G_0.4. After the incubation, in G₀ the abundances of ketones/aldehydes and nonpolar alkyl C increased, but those of aromatic C–C and protonated O-alkyl C (OCH) decreased; In G_0.4, the abundances of NCH and protonated O-alkyl C (OCH) increased, but those of nonpolar alkyl C and nonprotonated aromatic C–O and ketones/aldehydes decreased. Such inconsistent changes in recalcitrant compounds between G₀ and G_0.4 indicated that glucose addition likely primed the decomposition of aromatic C–O and suppressed the formation of ketones/aldehydes. We have demonstrated for the first time that the priming effect of SOC decomposition in the deep soil was involved with larger notable changes in both labile and recalcitrant structures of native SOC due to glucose addition compared with that without glucose addition.     

The significance of solid‐state 13C NMR spectroscopy of whole soil in the characterization of humic matter

Abstract

Differences in characteristics of humic matter were investigated by solid‐state CP/MAS ¹³C NMR spectroscopy of whole (nontreated) materials and their extracted humic fractions. Samples used in the analysis were lignite, a commercial humate AG, and the Bh horizons of a Mascotte and a Lawnwood soil. Humic fractions were extracted by the 0.1 M NaOH or Na₄P₂O₇ (pH 9.8) method. The humic (HA) and fulvic acid (FA) obtained were weighed and analysed for total acidity, carboxyl and phenolic‐OH group contents. Whole lignite, humate AG and soil samples, and the HA and FA fractions were analyzed by solid state CP MAS ¹³C NMR and infrared spectroscopy. Carbon, H, and N contents were determined by chemical analysis. NMR spectra of the combined HA+FA extracts resembled the spectra of the whole materials. No additional signals were detected, indicating that alien compounds were not produced during the extraction. The best spectra were obtained with HA samples produced by the NaOH method. These spectra closely resembled those of the untreated materials. Spectral and chemical differences noticed between the HA (or FA) fractions were attributed more to differences in origin than to the extraction procedure. Aliphatic, aromatic and carboxyl groups were the major components of HA from lignite and humate AG. In contrast, HA from the two Haplaquods were characterized by four major components: the aliphatic, polysaccharide, aromatic, and carboxyl groups. Regardless of origin, all the HA fractions contained similar functional groups, as indicated by their close similarities in infrared spectra.     

Structural Changes of Humic Acids During Olive Mill Pomace Composting

The aim of this work was to characterize the humic acids during composting using both chemical and spectroscopic analytical methods. Humic acids (HA) were extracted from olive mill pomace (OMP) after 5, 10, 21, 32, 48, 60, 84, 95, 109 and 153 days of composting and their elemental composition, functional groups, molecular weight, ¹³C CP-MAS NMR and FTIR spectra were determined. Elemental composition of HA showed a decrease of carbon content from 56.8% to 47.1% and an increase of oxygen content from 32.7 % to 43.3%. A slight increase of carboxylic groups was observed with no variation of phenolic groups. The molecular weight of HA determined by gel chromatography showed that after 95 days of composting the molecular weight of about 40% of the polymers was greater than 10² KDalton. The ¹³C CPMAS NMR and FTIR spectra of HA showed compositional and structural changes indicating a slight increase of polysaccharides and aromatic groups and a decrease of long aliphatic chains during the composting.     

土壤中钙结合和铁铝结合腐殖质的组成及结构特征

Calcium-bound and iron- and aluminium-bound humus extracted from different soils collected from north to south of China were characterized by chemical and spectroscopic methods. Meaningful differences in the composition and structure between them were revealed by ¹³C NMR, visible spectroscopy and elemental analysis. Results showed that the contents of carbon, hydrogen and nitrogen were higher in iron- and aluminium-bound humus than in calcium-bound humus while oxygen content in calcium-bound humus was shown to be higher. The calcium-bound humus had higher C/N and O/C ratios than iron- and aluminium-bound humus. The calcium-bound humic acid (HA1) showed higher E₄/E₆ ratios than iron- and aluminum-bound humic acid (HA2) while iron- and aluminum-bound fulvic acid (FA2) showed higher E₄/E₆ ratios than calcium-bound fulvic acid (FA1). An inverse relationship between E₄/E₆ ratios and aromaticity as determined by ¹³C NMR spectra was observed for HA and FA from black soil. The ¹³C NMR spectroscopy revealed that HA2 was more aromatic than HA1. On the other hand, FA1 exhibited a higher aromaticity than FA2.     

不同土地利用方式对黑土胶散复合体的影响及与酸度的关系

以吉林省黑土玉米带区域内10对长期定位采样点的2种土地利用方式土壤(耕作黑土和防护林带黑土)为研究对象,采用胶散分组法提取土壤胶散复合体,探究长期不同利用方式对黑土胶散复合体和酸度的影响。结果表明:耕作黑土与防护林带黑土均表现为G_0与G_2组的绝对含量增加,G_1组的绝对含量下降,复合体总量分别下降了3.88%和0.28%。耕作黑土和防护林带黑土pH分别平均下降12.12%和3.77%,有机碳含量在耕作黑土和防护林带黑土中分别平均下降23.17%和9.00%,2种利用方式土壤的胡敏酸、富里酸、交换性钙离子和碳酸钙均出现下降;耕作黑土分别平均下降12.18%,3.53%,16.29%,31.53%;防护林带黑土分别平均下降20.07%,13.14%,2.81%,7.81%。G_1组与pH、HA、Ca~(2+)和CaCO_3呈极显著正相关,与FA呈显著负相关;G_2组与pH、HA、Ca~(2+)和CaCO_3呈极显著负相关。pH与HA、Ca~(2+)和CaCO_3呈极显著正相关,与FA呈显著负相关。经过11年的变化,黑土胶散复合体稳定性下降,相比非耕作状态下黑土,耕作模式下的黑土胶散复合体稳定性下降更为严重,胶散复合体总量下降的更多,酸度下降更为明显。Ca~(2+)和HA的变化是影响黑土土壤酸化和土壤团聚体稳定性的主要驱动因素。土壤酸化的结果使土壤胶散复合体数量减少,稳定性变差。     

Humic matter isolated from soils and water by the XAD‐8 resin and conventional NaOH methods

Abstract

Differences were studied in humic (HA) and fulvic acid (FA) extracted from soils and streams in South Georgia by the Amberlite XAD‐8 resin and conventional NaOH method. Characterization analysis was performed by liquid ¹³C NMR, infrared (IR) spectroscopy, scanning electron microscopy (SEM), and chemical analysis. The NMR spectra indicated that the resin method yielded black water HA and FA with spectroscopic, chemical and elemental characteristics different from those isolated by the conventional NaOH method. Humic acids from both the resin and conventional NaOH methods were composed of aliphatic, aromatics and carboxyl groups, but the “resin”; HA contained more aliphatic groups. These differences were also noticed between the FA fractions obtained by the two methods. The differences corresponded to differences in IR spectra. The IR spectrum of “resin”; FA exhibited only a weak shoulder at 1625/cm for the COO”; stretching vibration, in contrast to that of FA isolated by the conventional NaOH procedure. Apparently, the high aliphatic‐CH₃ group content has blocked the vibration above, as evidenced by methylation of HA. Fulvic acid extracted by the resin method was also higher in total acidity, but considerably lower in N content than FA obtained by the conventional NaOH method. Both methods yielded black water FA which was less aromatic in nature than black water HA, or soil FA.     

Kinetics and characteristics of humic acids produced from simple phenols

In the presence of H₂O₂ as donor, horseradish peroxidase was used to catalyze the polymerization of seven monomeric phenols. Yields of humic acid (HA) polymers from meta phenols—resorcinol and phloroglucinol—were insignificant. Of the five ortho and para phenols—phenol, catechol, hydroquinone, pyrogallol and 1,2,4-trihydroxybenzene—all except hydroquinone inhibited the enzyme at high concentration. The kinetics of polymerization of the ortho and para compounds were complex and dependent on the concentration of both electron acceptor and donor.The percentage yield of HA before dialysis was far greater from pyrogallol than from catechol or hydroquinone. After dialysis, the yield of the catechol HA was higher than those of the hydroquinone and pyrogallol HAs. A higher molecular weight for the catechol HA over those of the hydroquinone and pyrogallol HAs was also indicated by the lowest E₄/E₆ ratio and highest free radical content.All of the synthetic HAs were relatively rich in free radicals, suggesting that their synthesis occurred via free radicals, i.r. and ¹³C NMR spectra showed that the HAs were molecularly complex polymers or mixtures of complex aromatic structures rich in phenolic OH groups and to a lesser extent in CO₂H groups. The only HA which showed fine structure in the i.r. spectrum was the pyrogallol HA; the presence of aryl ethers was indicated. ¹³C NMR spectra showed that all synthetic HAs were highly aromatic, that aromatic rings of the initial phenols had been built into the HAs, but that molecular environments around phenolic OH groups had changed during the formation of the HAs.     

Land-use effects on the composition of organic matter in particle-size separates of soils: II. CPMAS and solution 13C NMR analysis

Soils from A horizons of Eutrochrepts under spruce forest (Sf), mixed deciduous forest (Df), permanent grassland (Gp), and arable rotation (Ar) were fractionated into clay- (<2 μm), silt-(2–20 μm) and sand- (20–2000 μm) sized separates. ¹³C NMR spectroscopy was used to compare SOM composition across size separates and between land-use regimes. CPMAS ¹³C NMR spectroscopy showed that the intensity of signals assigned to carbohydrates (representing most O-alkyl C) and lignin (phenolic and methoxyl C) declined with decreasing particle size. Concurrently, alkyl C and C-substitution of aromatic C increased in the order sand, silt, clay. The amount of alkyl C correlated well with microbial resynthesis of carbohydrates. Solution ¹³C NMR spectra suggested that humic acids (HA) extracted from the size separates were richer in carboxyl C and aromatic C than the bulk size separates. Also HA reflected increasing percentage of alkyl C with decreasing particle size. O-alkyl C were lower in silt HA than in clay HA whereas aromatic C tended to peak in silt HA. These results suggested that sand-sized separates were enriched in plant residues (primary resources) whereas clay-sized separates were dominated by products of microbial resynthesis (secondary resources). Silt was rich in selectively preserved and microbially transformed primary resources. ¹³C NMR spectroscopy showed only small differences in SOM composition between land-use regimes, except that silt and silt HA from Ar were richer in aromatic C than those from the other plots. But enrichment factors (E= content in fraction/content in whole soil) revealed differences in the distribution of C species across the size separates. Relatively high E_aromatic (0.9) and E_o-alkyl (1.0) for sand from Gp indicated high amounts of plant residues, probably due to intense rhizodeposition and to occlusion of plant debris within aggregates. Low E_aromatic (0.3) and E_o-alkyl (0.3) for sand from Ar suggested depletion of primary resources, which could be attributed to disintegration of soil aggregates upon cultivation. A pronounced enrichment of alkyl C in Ar clay-sized separates (E_alkyl= 3.1) suggested large amounts of microbial carbon. Microbial products attached to clay surfaces by a variety of physico-chemical bondings appeared more stable against mineralization induced by cultivation than plant residues sequestered in aggregates.     

Selective extraction of humic acids from an anthropogenic Amazonian dark earth and from a chemically oxidized charcoal

Spectroscopic techniques including X-ray photoelectron spectroscopy (XPS) can identify particular chemical groups of humic acids (HA) from “Terra Preta de Índios” (TPI) or Amazonian dark earth, the highly fertile anthropogenic soil found in the Amazonian region. The high fertility and resilience of these soils cannot be explained by their chemically inert pyrogenic C content alone, but the natural aging of this C generates reactive carboxyl functional groups attached directly to the recalcitrant polycondensed aromatic backbone. Through spectroscopic techniques used in this work, the HA fraction (the alkaline-soluble organic matter that precipitates at low pH) of the TPI soil was compared with humic and fulvic acids, obtained by oxidizing activated charcoal with sodium hypochlorite. The yields recovery of HA-like substances was 12 and 28 wt% by using 10 and 20 cmol L^?1 of oxidizing agent, respectively. X-ray photoelectron spectroscopy, energy dispersive X-ray, and solid-state ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopies were used to evaluate the elements and structures present in all samples. XPS C 1 s spectra of HA extracted from TPI soil and from prepared HA showed aromatic structures (C?=?C and π–π* shake-up satellite peak) bounded to carboxyl groups (COOH). The morphology and polycondensation level of aromatic C were evaluated by scanning electron microscopy (SEM). The similarities of the spectra indicated that the used method was efficient to obtain an organic amendment similar to TPI soil organic matter.     

Offsetting global CO2 emissions by restoration of degraded soils and intensification of world agriculture and forestry

Increase in atmospheric concentration of CO₂ from 285 parts per million by volume (ppmv) in 1850 to 370 ppm in 2000 is attributed to emissions of 270 ± 30 Pg carbon (C) from fossil fuel combustion and 136 ± 55 Pg C by land‐use change. Present levels of anthropogenic emissions involve 6·3 Pg C by fossil fuel emissions and 1·8 Pg C by land‐use change. Out of the historic loss of terrestrial C pool of 136 ± 55 Pg, 78 ± 12 Pg is due to depletion of soil organic carbon (SOC) pool comprising 26 ± 9 Pg due to accelerated soil erosion. A large proportion of the historic SOC lost can be resequestered by enhancing the SOC pool through converting to an appropriate land use and adopting recommended management practices (RMPs). The strategy is to return biomass to the soil in excess of the mineralization capacity through restoration of degraded/desertified soils and intensification of agricultural and forestry lands. Technological options for agricultural intensification include conservation tillage and residue mulching, integrated nutrient management, crop rotations involving cover crops, practices which enhance the efficiency of water, plant nutrients and energy use, improved pasture and tree species, controlled grazing, and judicious use of inptus. The potential of SOC sequestration is estimated at 1–2 Pg C yr⁻¹ for the world, 0·3–0·6 Pg C yr⁻¹ for Asia, 0·2–0·5 Pg C yr⁻¹ for Africa and 0·1–0·3 Pg C yr⁻¹ for North and Central America and South America, 0·1–0·3 Pg C yr⁻¹ for Europe and 0·1–0·2 Pg C yr⁻¹ for Oceania. Soil C sequestration is a win–win strategy; it enhances productivity, improves environment moderation capacity, and mitigates global warming. Copyright © 2003 John Wiley & Sons, Ltd.     

Total carbon and nitrogen in the soils of the world

The soil is important in sequestering atmospheric CO₂ and in emitting trace gases (e.g. CO₂, CH₄ and N₂O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil conditions, may have important effects on the size of the organic matter pool in the soil and directly affect the atmospheric concentration of these trace gases. A discrepancy of approximately 350 × 10¹⁵ g (or Pg) of C in two recent estimates of soil carbon reserves worldwide is evaluated using the geo-referenced database developed for the World Inventory of Soil Emission Potentials (WISE) project. This database holds 4353 soil profiles distributed globally which are considered to represent the soil units shown on a ¹/₂° latitude by ¹/₂° longitude version of the corrected and digitized 1:5 M FAO–UNESCO Soil Map of the World. Total soil carbon pools for the entire land area of the world, excluding carbon held in the litter layer and charcoal, amounts to 2157–2293 Pg of C in the upper 100 cm. Soil organic carbon is estimated to be 684–724 Pg of C in the upper 30 cm, 1462–1548 Pg of C in the upper 100 cm, and 2376–2456 Pg of C in the upper 200 cm. Although deforestation, changes in land use and predicted climate change can alter the amount of organic carbon held in the superficial soil layers rapidly, this is less so for the soil carbonate carbon. An estimated 695–748 Pg of carbonate-C is held in the upper 100 cm of the world's soils. Mean C: N ratios of soil organic matter range from 9.9 for arid Yermosols to 25.8 for Histosols. Global amounts of soil nitrogen are estimated to be 133–140 Pg of N for the upper 100 cm. Possible changes in soil organic carbon and nitrogen dynamics caused by increased concentrations of atmospheric CO₂ and the predicted associated rise in temperature are discussed.     

Soil Organic Matter Quality and Zinc and Lead Sorption as Affected by a Sewage Sludge Or a Sewage Sludge Compost Application

Sewage sludge (SS) or sewage sludge compost (SSC) were applied to soil under controlled conditions, at rates of 0 or 200 Mg ha^?1, to investigate changes in dissolved organic matter (DOM), humic acids (HA), and Pb and Zn sorption in the soil. Infrared spectroscopy, visible spectrophotometry, and sorption isotherms (mono-metal and competitive sorption systems) methods were used to assess the changer. The E₄/E₆ ratio (λ at 465 / λ at 665 nm) and the infrared spectra of DOM and HA showed aromatic behaviour in compost-soil (SSC-S); in contrast sewage sludge-soil (SS-S) showed an aliphatic behaviour. Application of either SS or SSC increased the Pb and Zn sorption capacity of soil. The Pb and Zn sorption increased in soil and soil mixtures with a competitive metal system. The metal affinity sequence for soil, SS-S, and SSC-S was compared with the predicted affinity sequences obtained from metal properties. Poor correspondence was observed between the metal affinity sequence and the metal affinity sequence predicted by ionic potential, indicating that metals bonding to soils were not predominantly electrostatic. An affinity sequence based on Pearson's theory agreed with the metal affinity sequences for soils. A statistical analysis showed that the bands assigned to esters (1080 cm^?1) of DOM, phenolic OH (1420 cm^?1), amide I (1650 cm^?1), carboxyl and carbonyl C=O stretches of different nature, C=O stretch of aromatic esters, aliphatic cetone, aldehyde (1720 cm^?1), ethers and esters (1230 cm^?1), aliphatic alcohols (1125 cm^?1), and lignin (1380 cm^?1) of HA were correlated with Zn constants of Langmuir adsorption isotherm (P < 0.05).     

Assessment of C budget for grasslands and drylands of the world

Intergovernmental Panel on Climate Change (IPCC) estimates indicate that potential changes in seasonal rainfall and temperature patterns in central North America and the African Sahel will have a greater impact on biological response (such as plant production and biogeochemical cycling) and feedback to climate than changes in the overall amount of annual rainfall. Simulation of grassland and dryland ecosystem responses to climate and CO₂ changes demonstrates the sensitivity of plant productivity and soil C storage to projected changes in precipitation, temperature and atmospheric CO₂. Using three different land cover projections, changes in C levels in the grassland and dryland regions from 1800 to 1990 were estimated to be ?13.2, ?25.5 and ?14.7 Pg, i.e., a net source of C due to land cover removal resulting from cropland conversion. Projections into the future based on a double-CO₂ climate including climate-driven shifts in biome areas by the year 2040 resulted in a net sink of +5.6, +27.4 and +26.8 Pg, respectively, based upon sustainable grassland management. The increase in C storage resulted mainly from an increase in area for the warm grassland sub-biome, together with increased soil organic matter. Preliminary modeling estimates of soil C losses due to 50 yr of regressive land management in these grassland and dryland ecoregions result in a 11 Pg loss relative to current conditions, and a potential loss of 37 Pg during a 50 yr period relative to sustainable land-use practices, an average source of 0.7 Pg C yr^?1. Estimates of the cost of a 20 yr rehabilitation program are 5 to 8×10⁹ US$ yr^?1, for a C sequestering cost of approximately 10 US$ per tC.     

FTIR‐spectroscopic characterization of humic acids and humin fractions obtained by advanced NaOH,Na4P2O7, and Na2CO3 extraction procedures

Aim of our study was the development of the methodological basis for the characterization of humic fractions of a long‐term field experiment. Humic acids (HAs) were extracted from three layers of a nontilled soil using three different extractants (1 M NaOH, 0.1 M Na₄P₂O₇, 1 M Na₂CO₃), and the humin fraction was enriched. NaOH as extractant for FTIR analysis of humic substances yields higher resolved IR spectra, especially in the important regions of stretching vibrations including aromatic and aliphatic groups and in the fingerprint area including amides, aliphats, and aromats than the other extractants. The NaOH extraction has lower extraction yields as compared to Na₄P₂O₇ and Na₂CO₃ and represents a different part of the soil organic matter (SOM). This is reflected by lower C : N ratios and higher E₄ : E₆ and fulvic acid–to–humic acid ratios as compared to the other extractants. The FTIR band areas of HA fraction obtained by NaOH showed an increase of the aromatic and carbonyl groups and a decrease of amide groups with increasing soil depth. Aliphatic groups showed contradicting results: The bands of the stretching vibrations increased, and the band of the bending vibrations decreased. We assume that band interactions in the bending vibrations were responsible for that phenomenon under the assumption of an increase of aliphatic groups with increasing soil depth. The IR bands of the enriched humin fraction showed a decreasing trend in case of both aliphatic bands deriving from stretching vibrations and an increase of aromatic characteristics with depth. Our study led to the conclusion that HA fractions obtained by 1 M NaOH represent a small and dynamic fraction indicated by the measured yields in combination with values of N_t, C : N, E₄ : E₆ ratios, and ratios of fulvic acids (FA) to HA. The humin fraction has a high contribution to the total organic C and represents a more stabilized fraction of SOM which still shows changes in its aromatic and aliphatic characteristics with soil depth.     

Structure of Lysophosphatidylglyceryl-Remazolbrilliant Blue (LPG-RBB) from the Surface of Dyed Wheat Starch Granules

Wheat starch granule surface was covalently stained with Remazolbrilliant blue-R dye (RBB) and then extracted with 1% SDS containing 1% 2-mercaptoethanol (2-ME) at room temperature for 14.5 hr. The extracted blue-staining material (A₆₅₀) separated into two fractions. Low molecular weight (LMW) material was further purified by Sephadex G-75 size-exclusion chromatography and thin-layer chromatography. Infrared and nuclear magnetic resonance (¹H-NMR and ¹³C-NMR) spectroscopy indicated that the structure of the purified LMW material was 18-O-(6-lysophosphatidylglyceryl)-RBB.     

Comparative evaluation of compost humic acids and their effects on the germination of switchgrass (Panicum vigatum L.)

Purpose

This study aimed to investigate comparatively the main chemical and physico-chemical properties of the humic acid (HA) fraction of three different composts and to evaluate the bioactive effects of these HAs on the germination and early growth of four populations of switchgrass.

Materials and methods

Three compost HAs isolated from a green compost (HA_GC), a mixed compost (HA_MC), and a coffee compost (HA_CC) were characterized for some chemical and physico-chemical properties, such as ash content, elemental composition, total acidity, carboxylic and phenolic OH group contents, E₄/E₆ ratio, Fourier Transform infrared (FT IR), and fluorescence spectroscopies. In subsequent experiments conducted in vitro in a climatic chamber under controlled conditions, the bioactive effects of the three HAs at concentrations of 10, 50, and 200 mg?L^?1 were tested on the germination and early growth of four switchgrass (Panicum virgatum L.) populations, the octaploids Shelter, Shawnee and Dacotah, and the tetraploid Alamo.

Results and discussion

The ash content and the E₄/E₆ ratio were, respectively, much higher or slightly higher for HA_CC than for the other two HAs. HA_MC showed the lowest C and H contents and the highest O content, whereas HA_GC had the highest N content. The total acidity and phenolic OH group content followed the order: HA_MC?>?HA_CC?>?HA_GC. The fluorescence analysis of the three HAs evidenced a common fluorophore unit possibly associated to simple aromatic structures, such as phenolic-like, hydroxy-substituted benzoic and cinnamic acid derivatives. The FT IR spectra of all HA samples indicated the presence of aromatic phenolic structures. Significant beneficial effects were produced by any HA on switchgrass germination and early growth as a function of the population tested and the HA dose.

Conclusions

Results of this study demonstrated that the addition of compost HAs to the germination medium of four switchgrass populations positively influenced the germination process and the growth of primary root and shoot. Significant correlations were found between HA bioactivity and some HA properties. These results suggest a possible use of compost as soil amendment in areas where switchgrass grows naturally or is cultivated.     

Composition of humic acids extracted under air and nitrogen atmosphere

Abstract

Differences in nature and composition of humic matter, attributed to NaOH extraction under air or a N₂ gas atmosphere, were investigated. Samples from the Ap horizons of a Cecil and Onaway soil, and lignite were shaken with 0.1 M NaOH in the presence of air or under N₂ gas. The humic (HA) and fulvic acid (FA) separated were weighed, and analyzed for C, H, O, N, and S contents. Total acidity, carboxyl and phenolic‐OH group contents were determined by chemical analysis. Characterization was performed by ¹³C nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. The results indicated that differences in amounts of HA and FA, attributed to NaOH extraction under air and N₂ gas, were small and no definite trend was noted for more HA and FA extracted under air. No differences in C, H, O, N, and S contents of HA and FA were also noticed as a result of the influence of air or N₂ gas during extraction. However, HA and FA exhibited larger values for total acidities when extracted under a N₂ gas atmosphere than under air. The lower amounts of carboxyl and phenolic‐OH group contents in HA and FA as a result of NaOH extraction under air, however, do not support the idea of increased oxidation by NaOH. No differences were noticed in NMR and IR spectra of HA and FA attributable to the two extraction methods. The differences in NMR and IR features obtained were more the result of differences in origin than in methods of extraction.