Ein neues Verfahren zur Extraktion von organischen Stoffen aus Böden mit überkritischen Gasen 2. Mitteilung

A new procedure for the extraction of organic matter from soils by supercritical gases Extracting soil samples with supercritical gases high amounts of nearly ash-free organic preparations can be obtained. A direct fractionation in classes of compounds with different chemical constitution is achieved by using solvents of variable polarity. Fats and dicarboxylic acids can be solved in pentan, phenols and hemicelluloses in ethanol, lignin and cellulose in ethanol/water. The substances obtained from the pentan extract were identified by GC/MS analysis. The non volatile compounds of the ethanol/water extract were decomposed by permanganate and the products compared with those of the oxidized humic acids. Though there is a high number of different compounds the podzol profile investigated shows typical patterns of distribution for certain components.     

Availability of Pyrene in Unaged and Aged Soils to Earthworm Uptake, Butanol Extraction and SFE

Eco-risk of an organic pollutant in soil is quite influenced by the property of the soil and contamination history. To evaluate the influence of these factors on the availability of organic pollutants, earthworm accumulation of pyrene in six different soils were studied in this paper used unaged and aged samples. Moreover, butanol extraction and supercritical fluid extraction (SFE) of pyrene in these samples were determined simultaneously, and the relationship between bioaccumulation and extraction by butanol and SFE before and after aging were investigated in order to find a rapid method to predict the bioavailability. The results showed that, for unaged samples, percentages of pyrene accumulated by the earthworms (Eisenia foetida), extracted by butanol and mild supercritical fluid were 1.9–18.5%, 41.8–50.8% and around 50%, respectively. Generally, the percentages of the earthworm accumulation decreased significantly and butanol extraction decreased slightly with the content of soil organic matter (SOM) in soils. Clay content might also influence pyrene availability when SOM content is smaller than 1%. However, mild SFE could not differentiate the availability of the pyrene in unaged soils. Both the bioavailability and the chemical availability of pyrene decreased significantly after aged in soils for 120 days, and the percentages of availability by the three test methods were 0.87–3.65%, 18.7–27.6% and 12.9–28.2%, respectively. A correlation relationship study of pyrene extractability by butanol and mild SFE with bioavailability to earthworm uptake for aged soils suggested that mild SFE was a better approach to predict the bioavailability of organic chemicals in field soils compared to butanol extraction.     

Liquid extraction of low molecular mass organic acids and hydroxamate siderophores from boreal forest soil

Low molecular mass organic acids (LMMOAs) and hydroxamate siderophores (HS) are molecules secreted by microbes and have previously been found in soil solution and in cultures. Mycorrhizal fungi are suggested to be involved in the nutrient uptake processes of trees and weathering of minerals. In this study soil samples taken from the O and E horizons of a podzol were extracted with 10 mM potassium phosphate buffer at pH 7.2. Variable parameters included addition of methanol to the extraction buffer and the use of ultrasonication or rotary shaking during extraction. LMMOAs and HS content of the soil extracts were determined. Analysis of soil extracts were carried out by liquid chromatography mass spectrometry (LC–MS) and the extraction results compared to results for soil solution samples obtained by centrifugation of the soils sampled. The extraction yields were significantly increased by addition of methanol to the extraction buffer, especially for the O horizon samples. Rotary shaking of the samples for 90 min gave slightly higher yields than ultrasonication for 15 min but the reduction in extraction time makes ultrasonication an attractive option. Of the HSs determined, ferricrocin was found in all samples. Optimal extraction conditions showed citric acid and isocitric acid to be the most abundant organic acids in the O and E horizons, respectively.     

Liquid extraction of low molecular mass organic acids and hydroxamate siderophores from boreal forest soil

Low molecular mass organic acids (LMMOAs) and hydroxamate siderophores (HS) are molecules secreted by microbes and have previously been found in soil solution and in cultures. Mycorrhizal fungi are suggested to be involved in the nutrient uptake processes of trees and weathering of minerals. In this study soil samples taken from the O and E horizons of a podzol were extracted with 10 mM potassium phosphate buffer at pH 7.2. Variable parameters included addition of methanol to the extraction buffer and the use of ultrasonication or rotary shaking during extraction. LMMOAs and HS content of the soil extracts were determined. Analysis of soil extracts were carried out by liquid chromatography mass spectrometry (LC–MS) and the extraction results compared to results for soil solution samples obtained by centrifugation of the soils sampled. The extraction yields were significantly increased by addition of methanol to the extraction buffer, especially for the O horizon samples. Rotary shaking of the samples for 90 min gave slightly higher yields than ultrasonication for 15 min but the reduction in extraction time makes ultrasonication an attractive option. Of the HSs determined, ferricrocin was found in all samples. Optimal extraction conditions showed citric acid and isocitric acid to be the most abundant organic acids in the O and E horizons, respectively.     

The effects of rock fragmentation and / or deep tillage on soil skeletal material and chemical properties in a Mediterranean climate

In Puglia, Italy, deep tillage and rock fragmentation are common agricultural practices to prepare land for vineyards or orchards. Unfortunately, little is known about how these practices influence soil structure and quality. There is a lack of information on the consequences of these practices on the soil fractions coarser than 2 mm, which are known as rock fragments or skeletal material, the focus of this study. Soil samples were obtained from depths of 0‐20 and 20–40 cm and analysed for pH, electrical conductivity, total organic carbon, total nitrogen, available phosphorus, and total and active calcium carbonate. For each soil depth, we determined the amount of fine earth and skeletal material by volume. The results indicate that rock fragmentation and/or deep ploughing cause a major change in soils, leading to the progressive reduction in total organic carbon and nitrogen, and to an increase in total and active calcium carbonate. In addition, there was a marked increase in skeletal material compared to undisturbed soil. The results confirm that rock fragmentation causes significant changes in soil physical properties and increases greatly the amount of skeletal material.     

Einfluß von Meliorationsmaßnahmen auf die kleinräumliche Variation von Waldbodeneigenschaften

Influence of amelioration procedures on the small scale spatial variation of forest soil properties After clearcutting, a podzol-pseudogley derived from silty loam covering clay and a podzolic brown forest soil of sandy texture were treated as follows: CaPMg-fertilization either alone or combined with tilling (after herbicide spray) or ploughing (after mechanical stump extraction); planting of young pines, fertilization with N in the third growing season. Eight years after initiation of the trials, the coefficients of variation for stoniness and bulk density didn't differ between treatments. On the other hand there was clear evidence, that the clearcutand the subsequent amelioration techniques had increased the variability of the organic floor weight as well as of the pH, the carbon and nitrogen contents of the top mineral soil. These effects presumably are due to an irregular mixing of fertilized raw humus and A-horizon material with subsoil layers by harvesting procedures, tilling or ploughing and bioturbation.     

Water-extractable organic matter linked to soil physico-chemistry and microbiology at the regional scale

A better understanding of the links between dissolved organic matter and biogeochemical processes in soil could help in evaluating global soil dynamics. To assess the effects of land cover and parental material on soil biogeochemistry, we studied 120 soil samples collected from various ecosystems in Burgundy, France. The potential solubility and aromaticity of dissolved organic matter was characterised by pressurised hot-water extraction of organic carbon (PH-WEOC). Soil physico-chemical characteristics (pH, texture, soil carbon and nitrogen) were measured, as was the δ¹³C signature both in soils and in PH-WEOC. We also determined bacterial and fungal abundance and the genetic structure of bacterial communities. Our results show that the potential solubility of soil organic carbon is correlated to carbon and clay content in the soil. The aromaticity of PH-WEOC and its δ¹³C signature reflect differences in the decomposition pathways of soil organic matter and in the production of water-extractable organic compounds, in relation to land cover. The genetic structure of bacterial communities is related to soil texture and pH, and to PH-WEOC, revealing that water-extractable organic matter is closely related to the dynamics of bacterial communities. This comprehensive study, at the regional scale, thus provides better definition of the relationships between water-extractable organic matter and soil biogeochemical properties.     

Soil organic phosphorus in tropical forests: an assessment of the NaOH–EDTA extraction procedure for quantitative analysis by solution 31P NMR spectroscopy

The extraction of soil organic phosphorus by the NaOH–EDTA procedure was assessed in detail for a tropical forest soil (clay‐loam, pH 4.3, total carbon 2.7%). Optimum conditions for the quantification of soil organic phosphorus and characterization of its composition by solution ³¹P NMR spectroscopy were extraction in a solution containing 0.25 m NaOH and 50 mm Na₂EDTA in a 1:20 solid to solution ratio for 4 hours at ambient laboratory temperature. Replicate analyses yielded a coefficient of variation of 3% for organic phosphorus as a proportion of the spectral area. There was no significant difference in total phosphorus extraction from fresh and air‐dried soil, although slightly more organic phosphorus and less paramagnetic ions were extracted from dried soil. The procedure was not improved by changing the concentration of NaOH or EDTA, extraction time, or solid to solution ratio. Pre‐extraction with HCl or Na₂EDTA did not increase subsequent organic phosphorus extraction in NaOH–EDTA or improve spectral resolution in solution ³¹P NMR spectroscopy. Post‐extraction treatment with Chelex resin did not improve spectral resolution, but removed small concentrations of phosphorus from the extracts. Increasing the pH of NaOH–EDTA extracts (up to 1.0 m NaOH) increased the concentration of phosphate monoesters, but decreased DNA to an undetectable level, indicating its hydrolysis in strong alkali. The standardized NaOH–EDTA extraction procedure is therefore recommended for the analysis of organic phosphorus in tropical forest soils.     

土壤有机质光谱响应特性研究

土壤有机质光谱响应特性研究是光学遥感定量化的基础性研究.研究利用VF991地物光谱测量仪对八个不同环境条件下形成的土壤样本剖面上的各个土层进行光谱测量,得到各个土层的反射率光谱曲线,并测出各个土层的有机质含量.通过研究土壤的有机质含量与土壤反射光谱间的相关性分析,发现有机质含量与土壤光谱在紫外区的376.795nm波段、可见光区的616.506nm波段和近红外区的724.0975nm波段附近有较好的负相关性     

土壤、沉积物和植物样品中多环芳烃（PAHs）不同提取与净化方法比较

系统分析和比较了土壤、沉积物和植物样品中多环芳烃（PAHs）的提取与净化方法,阐述和对比了索氏提取法、超声波提取法、超临界流提取法、固相提取与固相微提取法、固液提取法、微波辅助提取法、快速溶剂提取法等提取方法以及定量浓缩净化法、硅胶柱层析净化法、费罗里土柱层析净化法、氧化铝净化法、固相萃取（SPE）净化法等净化方法。旨在通过比较目前的提取和净化方法,展望将来提取与净化方法发展的新方向。     

Application of <Superscript>13</Superscript>C NMR Spectroscopy to the Study of Soil Organic Matter: A Review of Publications

Possibilities of NMR spectroscopy with ¹³C nuclei application to the study of soil organic matter and its various fractions is considered. This is a non-destructive method, which is particularly valuable in the analysis of various fractions of soil organic matter. It is regarded as a direct method, and, unlike most of indirect methods, it allows one to obtain reliable estimates of the ratio between virtually all groups of carbon atoms in different organic molecules, including those in humus specimens. Owing to impulse technique and high sensitivity, ¹³C-NMR spectra may be obtained immediately from soil samples without any extraction operations. The modern technique of obtaining spectra, their mathematical processing (Fourier transform), and data interpretation are considered. The results of applying ¹³C-NMR to the study of humus substances, water-soluble fractions of soil organic matter, and soil litters from different natural zones are discussed.     

土壤样品中多环芳烃分析方法研究进展

概述了国内外土壤样品中多环芳烃(PAHs)测定方法的研究状况,其中提取方法包括加速溶剂萃取方法、固相微萃取方法、超临界流体萃取方法、亚临界水萃取方法和流化床提取方法等,测定方法有HPLC法、GC法和免疫分析法等。重点介绍了PAHs的提取过程,同时总结了各种方法的优缺点。     

Kinetics of the release of dissolved organic matter (DOM) from air‐dried and pre‐moistened soil material

In this study, the kinetics of soil organic matter (SOM) dissolution from soil samples in different states of moisture was investigated, using a continuous extraction method. The investigation distinguished three processes of SOM dissolution. They include an initial, fast process (probably hydrophilic dissolved organic matter) and two slow, rate limited processes, which probably correspond to hydrophobic dissolved organic matter (DOM). The second process indicates a slow, continuous release of DOM, whereas the third process is determined by a power law. The rate of the third process strongly depends on temperature and state of moisture. It is diffusion limited, with the diffusion control probably being located in the solid soil organic matter. This was explained by a gel structure, which slowly forms in the hydrating SOM and allows diffusion of mobile particles of SOM. The results show the importance of considering the moisture state of SOM for the kinetics of DOM dissolution.     

Supercritical fluid extraction of bioavailable amino acids from soils and their liquid chromatographic determination with fluorometric detection

A new procedure with supercritical CO2 modified with 0.5 mL of water and 0.75 mL of 0.1 M HCl in situ and 0.75 mL of water on-line at 15 MPa and 50 degrees C for 45 min was applied for the extraction of bioavailable amino acids from soil samples. Total extraction time was 60 min, but more favorable conditions are even possible for selected groups of amino acids. All analytes were trapped into 20 mL of methanol with satisfactory recovery (94-104%) and determined using high-performance liquid chromatography with fluorometric detection on a Zorbax Eclipse column (4.6 x 75 mm, 3.5 microm) with Na2HPO4 and acetonitrile/methanol/water as a mobile phase. Linear calibration curves were obtained (r > 0.999 except 0.99823 for Ile) with lower limits of detection (S/N = 3) in the range from 1.54 pg (Gly) to 13.5 pg (Cy2) or from 18.6 fmol (Ser) to 64.8 fmol (Lys). Validation and repeatability data are also given. Comparable results were obtained with a robust, commonly used extraction method (0.5 M ammonium acetate, 60 min in shaker, followed by filtration and lyophilization). Limiting values of artificial release of amino acids were also determined for each soil sample to eliminate any false results to ensure that all extracted amino acids originate from soil solution and exchangeable bound positions of soil samples.     

Abiotic uptake of gases by organic soils

Methodological and experimental studies of the abiotic uptake of gaseous substances by organic soils were performed. The static adsorption method of closed vessels for assessing the interaction of gases with the solid and liquid soil phases and the dynamic method of determining the sorption isotherms of gases by soils were analyzed. The theoretical substantiation of the methods and their practical implementations on the basis of a PGA-7 portable gas analyzer (Russia) were considered. Good agreement between the equilibrium sorption isotherms of the gases and the Langmuir model was revealed; for the real ranges of natural gas concentrations, this model can be reduced to the linear Henry equation. The limit values of the gas sorption (Langmuir monolayer capacity) are typical for dry samples; they vary from 670–4000 g/m³ for methane and oxygen to 20 000–25 000 g/m³ for carbon dioxide. The linear distribution coefficients of gases between the solid and gas phases of organic soils (Henry constants) are 8–18 units for poorly sorbed gases (O₂, CH₄) and 40–60 units for CO₂. The kinetics of the chemicophysical uptake of gases by the soil studied is linear in character and obeys the relaxation kinetic model of the first order with the corresponding relaxation constants, which vary from 1 h ^?1 in wet samples to 10 h ^?1 in dry samples.     

THE EFFECT OF SOIL FACTORS ON THE EXTRACTION OF SOIL ORGANIC MATTER BY ANHYDROUS FORMIC ACID

Twenty-five soils, having a wide range of organic matter contents, were extracted with anhydrous formic acid containing 10 per cent acetylacetone, and the extracted material precipitated in two fractions with diisopropyl ether. Precipitates comprised from 5.1 to 51.1 per cent of the original soil organic matter, the proportion extracted tending to be greatest from acid soils of fairly high organic matter content and least from neutral or slightly alkaline soils of low organic matter content. Soil clay content appeared to have no effect on the efficiency of organic matter extraction, but was the most important soil factor governing the proportion of the total soil-N extracted. Amounts of N extracted ranged from 10.2 to 57.8 per cent of the original soil N content, extraction efficiency being greatest with soils of low clay content and low pH. There was evidence to suggest that soil clay afforded some protection to N compounds against extraction. The results indicate that formic acid/acetylacetone is most effective with soils in which much of the organic matter is only partly humified.     

Multiresidue analysis of pesticides in soil by supercritical fluid extraction/gas chromatography with electron-capture detection and confirmation by gas chromatography-mass spectrometry

The applicability of supercritical fluid extraction (SFE) in pesticide multiresidue analysis (organohalogen, organonitrogen, organophosphorus, and pyrethroid) in soil samples was investigated. Fortification experiments were conducted to test the conventional extraction (solid-liquid) and to optimize the extraction procedure in SFE by varying the CO2 modifier, temperature, extraction time, and pressure. The best efficiency was achieved at 400 bar using methanol as modifier at 60 degrees C. For the SFE method, C-18 cartridges were used for the cleanup. The analytical screening was performed by gas chromatography equipped with electron-capture detection (ECD). Recoveries for the majority of pesticides from spiked samples of soil at different residence times were 1, 20, and 40 days at the fortification level of 0.04-0.10 mg/kg ranging from 70 to 97% for both methods. The detection limits found were <0.01 mg/kg for ECD, and the confirmation of pesticide identity was performed by gas chromatography-mass spectrometry in a selected-ion monitoring mode. Multiresidue methods were applied in real soil samples, and the results of the methods developed were compared.     

Influence of drying vs. freezing of archived soil samples on soil organic matter fractions

Archived soil samples are a valuable tool for any long‐term soil research. We analysed total carbon (C) and nitrogen (N) content and soil organic matter fractions in 38 archived soil samples that were stored for up to 21 years and compared air‐dried storage to frozen storage conditions. Samples include top‐ and upper subsoils, different soil texture and land use with C contents between 4.3 and 174 mg g^?1. The results from this study reveal no changes in total C and N contents with storage time up to 21 years or type of storage (freezing vs. air drying). The analyses of soil physical fractions also revealed no significant differences between air‐dried stored and frozen stored samples for most samples. However, we found indications, that freezing of soil material might lead to changes in the mineral fractions for soils containing high amounts of water. Therefore, and as archiving soils in a frozen state is more expensive than storing air‐dried samples, we recommend the use of air‐dried samples for C quality analyses of archived soil samples.     

Method for characterization of inert organic carbon in Urbic Anthrosols

Abstract

Organic matter in Urbic Anthrosols often contains chemically and biologically inert organic carbon. This material, called black carbon (BC), originates from municipal wastes, coal‐mine deposits and/or fly ash. This black carbon needs to be differentiated from the other soil organic substances because of its very different physical and chemical nature. In this paper, we propose a new method for determining BC, integrated into the humic fractionation procedure. The remaining organic carbon in the soil residue left after lipid extraction, alkaline extraction [0.5 M sodium hydroxide (NaOH)], and further oxidation with 30% hydrogen peroxide (H₂O₂) is defined as inert organic carbon or BC. The common fractions of soil organic matter, such as lipids, fulvic and humic acids, and humins are thus supplemented with a new fraction, BC. According to our results by ¹³C‐NMRspectroscopy, this fraction consists mainly of polyaromatic hydrocarbons with few functional groups.     

Soil organic matter composition in three humus profiles of the western Taurus,Turkey, as revealed by wet chemistry and CP/MAS 13C NMR spectroscopy

In this study three soil profiles located in the Western Taurus (Turkey) at different altitudes (10, 1900, and 3080 m a.s.l.) were compared with respect to their soil organic matter characteristics. The soil samples were fractionated by density to plant residues, slightly altered plant material, organo-mineral complexes, and organic-free minerals. Bulk samples and fractions were analyzed for C and N, the bulk samples additionally for total sugars, lignin signature, and bulk soil organic matter composition by CP/MAS ¹³C NMR spectroscopy. The first step of litter decomposition and humification is a very strong degradation of polysaccharides without the loss of O-alkyl structures. This process is slowing down very fast and the polysaccharides are stabilized. Lignin is decomposed as fast or even faster than polysaccharides. The data obtained by wet-chemical analysis and by NMR spectroscopy are not or only weakly correlated to each other. This leads to the conclusion that the two types of methods give complementary rather than equivalent information. For the study of soil organic matter it is important to combine different methods and to draw the advantages of either type.