HUMUS TYPE DISCRIMINATION USING PATTERN RECOGNITION OF THE MASS SPECTRA OF VOLATILE PYROLYSIS PRODUCTS

Mull and mor humus can be distinguished in freely drained British surface soils by the pyrolysis products derived from whole soil samples. About i milligram of soil is pyrolysed at 770 °C in a Curie point apparatus and a sample of the volatile decomposition products is allowed to enter a low-resolution mass spectrometer. A numerical value (the ‘Discriminator Value’) which will discriminate between the two humus types is then calculated from the spectrum of each sample. This is performed by multiplying the intensity of each mass peak by a weight factor and then summing the weighted intensities up to mass 110 The weight factors are obtained empirically by taking sets of spectra from clearly distinguished mull and mor samples and applying a computerized learning machine procedure. Once obtained, they are relatively easily applied to spectra from other soils. The method places all samples on a numerical scale on which mull types appear positive up to about 20 × 10⁸ and mor types negative down to about -15 × 10³, intermediate types being recognized in about the middle of the range. It is indicated that the most important pyrolysis products active in the discrimination process are the olefin hydrocarbons, particularly ethylene, which are produced in greater abundance from mor humus.     

A PYROLYSIS-GAS CHROMATOGRAPHY METHOD FOR DISCRIMINATION OF SOIL HUMUS TYPES

Principles governing the choice of a pyrolysis-gas chromatography method for work on soils and organic macromolecules are reviewed, and the method is applied to the discrimination of mull and mor humus in freely drained soils. Relatively undecomposed surface humus shorizons yield pyrolysis products characteristic of lignin, but these are not present in mineral horizons apart from traces persisting in some podzol A horizons. Mor humus incorporated in A horizons is characterized by a high pyrolysate content of furfurals and phenols whilst mull humus yields proportionately more pyrrole. Humus in B horizons yields a low furfural content with respect to pyrrole and a low content of polar heteroatomic molecules with respect to benzene, toluene, and light molecules of low polarity.     

土壤种子库样品萌发的前处理方法： 水洗减量

埋藏于土壤中的种子是植物群落再生的物质基础,识别这些种子的种类与数量特征是很多植物群落学、恢复生态学等相关学科领域的重要内容。将采集土壤样品置于温室内,保持最佳的萌发环境让尽量多的物种种子萌发,通过鉴定这些萌发幼苗的种类与数量来推断土壤种子库的种类组成与密度是最重要的种子库检测方法之一[1~3],国内的研究者也基本采用这一方法[4~11]。该方法在检测的精度和准确度上具有不可替代的优越性[1,12,13]。即使在同一生态系统内,不同的植物种子所需要的萌发条件可能由于休眠[2]、种子对策差异[3,14],对光照、温度[14~16]等的需求差异而存在巨大差别,作为种子存贮与萌发介质的土壤层的厚度和     

一种直接测定硝化—反硝化气体的15N示踪—质谱法

本文对¹⁵N示踪—质谱法的可靠性进行了检验。结果表明,在不同的¹⁵N丰度气体样品的测定中,用两种方法(反硝化作用源的¹⁵N丰度法和气样的¹⁵N丰度法)计得的反硝化损失量基本一致,故建立起来的¹⁵N示踪—质谱法是可靠的。该方法的测定偏差随气样¹⁵N丰度的降低而增大。此外,回收率结果表明,(N₂+N₂O+NO_x)-¹⁵N累积释放量占加入NO₃-¹⁵N量的94.1％。因此,这一方法可用于直接测定氮肥的硝化—反硝化损失的研究中。     

THE HUMIC ACIDS EXTRACTED BY VARIOUS REAGENTS FROM A SOIL

The infra-red, visible, and ultra-violet absorption spectra of humic acids extracted from a red-brown earth by various reagents, are described. The variations in the intensity of various absorption bands in the infra-red spectra are related to the method of extraction, yield, and titration data. For example, the humic acids extracted by milder reagents give rise to spectra which show relatively weak aliphatic C-H absorption whilst the intensity of the bands arising from oxygen-containing groups (carboxyl and ketone carbonyl) is relatively strong. The opposite behaviour is shown by the corresponding bands in the spectra of humic acids extracted by stronger reagents. The intensities of other infra-red bands are also considered. The optical density of the C═O band at 1720 cm^?1 in the humic-acid spectra and of the carboxylate ion band at 1380 cm^?1 in the spectra of the K salt is linearly related to the exchange capacity. The presence of carboxyl groups ionizing above pH 7 and extending to as high as pH 11, is demonstrated.     

THE HUMIC ACIDS EXTRACTED BY VARIOUS REAGENTS FROM A SOIL

Solutions of o.5N NaOH, o.1M pyrophosphate (pH 7), and o.5N Na(CO^2?₃/HCO^?₃) [2:1] extract humic acid and organic matter from a soil with decreasing effectiveness. Pre-treating the soil with o.1N HC1 increased the yield of humic acid obtained with the alkaline extractants. An additional pre-treatment with a mixture, which was normal with respect to HC1 and HF, gave a slight reduction in yield. Increasing the temperature of extraction increased the yield of humic acid. The total C extracted was usually in excess of the humic acid recovered. The difference was obtained as ‘humins’. The sum of the Fe₂O₃, SiO₂, and A1₂O₃ contents of the humic acids was always less than 2 per cent. Where the extraction was carried out at room temperatures the SiO₂/Al₂O₃ ratio suggested that they might be present as clay mineral. When extraction was carried out at an elevated temperature this ratio was altered. Humic acids of low ash content (0.1–0.5 per cent) could be obtained by the use of hot reagents. Of all the extractants used at room temperature, pyrophosphate produced the humic acid of lowest ash content (～ 0.2 per cent). The Fe₂O₃ content of the humic acids was not correlated with their SiO₂ or A1₂O₃ content. The N-content of the humic acids was substantially independent of the method of extraction. The cation-exchange capacities (C.E.C.), average pK values and range of pK values, have been determined from the titration curves of the humic acids. These quantities vary with the method of extraction. There are good correlations between cation exchange capacity and both average pK values and the range of pK values. The within-molecule variation of pK values appears to be greater than the between-molecule variation. No correlation exists between C.E.C. and Fe, Al, Si, and N content of the humic acids.     

施加不同电压对铬污染黄棕壤电动过程的影响

研究了在控制阴极液酸度条件下,施加不同电压对铬污染黄棕壤中铬的电动过程的影响,结果表明增加应用电压显著提高了处理电流和电渗流量,所有电动处理后土柱中土壤pH均在3左右,低pH环境引起土柱中铬的氧化还原和沉淀反应并导致土柱中电压降的不均匀分布。施加20 V电压处理获得了较好的铬去除率和较低的能耗,576 h后土壤中总铬和六价铬的去除率分别达到41.1%和77.7%。控制阳极池溶液酸度将是一个能够显著提高土壤铬去除的有效方法。     

INTERPRETATION OF PHOSPHORUS UPTAKE BY BARLEY FROM ACID SOILS USING A DIFFUSION MODEL

Phosphorus uptake by bailey (per cent of dry tissue) grown on four acid soils, each treated with four amounts of lime and P, correlated equally well with EPC (equilibrium P concentration = concentration of P supported in solution at field capacity) and with diffusion supply of P to root cylinder surfaces calculated from the soil indices including EPC, a soil capacity factor maintaining that concentration, and a diffusion coefficient. Calculated rates of P supplied by diffusion to primary root cylinder surfaces were too low to account for P found in plants. If the remainder of the observed P uptake was assigned to root hairs, the ratios of calculated root hair surface area to estimated root cylinder surface areas necessary to account for the difference were in reasonable agreement with ratios for barley reported by other workers.     

SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDES BY EDTA FROM A DANISH SANDY LOAM

EDTA extracts (pH 7.5–10.5) from a Danish sandy loam showed no significant (95% level) increase in amounts of aluminium, calcium, iron, and magnesium between three and nine months' shaking. The amounts were independent of the soil: solution ratio (1:10–1:50), the EDTA concentration (0.01 M–0.2 M), and crushing the soil (< 0.25 mm or < 2 mm). IR spectroscopy and X-ray diffraction showed no change in the mineral composition of the soil during the extraction. The extracted iron was equal to that extracted after 2 h by ammonium oxalate at pH 3.0. EDTA extraction at pH > 7.5 seems to extract selectively iron oxides with solubility products > ～ 10^?41.     

魔芋辐照接枝丙烯酸及其产物吸水性能的研究

研究了魔芋-丙烯酸辐照接枝共聚条件及产物的吸水性能,结果表明接枝最佳配方为:魔芋粉∶丙烯酸∶NaOH(9.5mol/L)∶水=3g∶21ml∶17.8ml∶131ml。丙烯酸与魔芋粉配比为7∶1(体积质量比);丙烯酸中和度55%;辐照后胶体最佳烘干温度30℃,该温度下40~80目颗粒吸水倍数较大,常温120min时达最大吸水866.5倍。温度对产物吸水和胶体保水有一定影响,以60℃以下为宜。pH对产物吸水倍数影响明显,但不及离子浓度对产物吸水倍数的影响大。     

A COMPARISON OF THE POLYCARBOXYLIC ACIDS EXTRACTED BY WATER FROM AN AGRICULTURAL TOP SOIL WITH THOSE EXTRACTED BY ALKALI

Humic and fulvic acids were isolated from an agricultural soil by conventional means. The same soil was extracted with water and the organic matter freed of inorganic and low molecular weight substances. The usual chemical differences between humic acid and fulvic acid were confirmed and the water extract was shown to resemble fulvic acid quite closely. Further fractionation of the fulvic acid and water extract showed that the elemental composition, carboxyl and acidic hydroxyl contents, molecular weights, and infrared spectra of the purified polycarboxylic acids were virtually identical. Both promoted the same growth response in cultured isolated tomato roots. It is suggested that the qualitative similarity of fulvic acid to the polycarboxylic acid extracted by water justifies the use of the more easily isolated fulvic acid in physiological experiments on the direct effects on plants of soil organic matter.     

A METHOD OF PREDICTING BULK DENSITY CHANGES IN FIELD SOILS RESULTING FROM COMPACTION BY AGRICULTURAL TRAFFIC

A simplified soil mechanical model was constructed to predict compaction beneath agricultural wheels when running on soils of certain characteristics. Soil strength functions were developed from in situ measurements of field soils and some laboratory measurements. Soil strain was measured by surface sinkage and changes of dry bulk density by gamma-ray transmission methods. Soil stresses were measured by deformable spherical transducers and compared to predicted stresses using equations developed by Söhne. A method of analysis was devised to identify a form of the virgin compression line from field data. Changes of the slope and intercept of this line were monitored over a range of moisture contents for two soils and used in the prediction model. The prediction model was tested against compaction measured during independent experiments at different sites. Good prediction was found for soils of initial dry bulk density greater than 1.1 g cm^?3 and cone resistance greater than 500 kPa, using a 30°, 12.9mm diameter cone. On looser and weaker soils the predicted compaction was often less than measured values. Using the model for simulation of compaction beneath a range of wheels revealed that contact pressure alone can be a misleading guide to compaction. Increases of bulk density below 10cm are considerably influenced by wheel load. The most effective way of reducing compaction requires the use of both a minimum load and a maximum contact area.     

SEPARATION OF THE LIGHT FRACTION FROM SOILS BY ULTRASONIC DISPERSION IN HALOGENATED HYDROCARBONS CONTAINING A SURFACTANT

Partially humified material can be separated from other soil material by flotation on a bromoform-petroleum spirit mixture of density 2·0 g cm^-3. Maximum recovery of partially humified material requires ultrasonic dispersion and the addition of a surfactant to the suspension. For large-scale work‘Nemagon’ may be used in place of the bromoform-petroleum spirit mixture.     

γ辐照与赤霉素复合处理育成小麦新品种西辐九号

选用西昌反修麦为材料，经＾６０Ｃｏγ射线辐照之后，播种前用赤霉素（Ｇｉｂｂｅｒｅｌｌｉｎ）浸种复合处理，诱变育成矮秆抗倒，株型紧凑，幼苗直立，叶片短宽，适应性较广，耐瘠，耐湿，抗条锈病小麦新品种西辐九号，一般产量６８４０ｋｇ／ｈｍ＾２，研究表明，γ辐照与赤霉素复合处理能减轻辐射损伤，有效的提高辐照当代的田产出苗率，拓宽突变谱，扩大变异群体，提高有益突变频率，赤霉素可作辐射防护剂。     

SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDE BY EDTA FROM A MIXTURE OF AMORPHOUS IRON OXIDE, GOETHITE, AND HEMATITE

Iron (III) was extracted by EDTA and ammonium oxalate from a model substance consisting of amorphous iron oxide, goethite, and hematite precipitated in the presence of quartz sand. Even by varying the EDTA concentration between 0.02 and 0.1 M, pH between 4.40 and 6.00, the solid:solution ratio between I:25 and I:250, and using extraction times up to go days, it was found that EDTA was able to extract only a limited amount of iron. In contrast, 0.2 M ammonium oxalate at pH 3.0 is able to dissolve all the iron compounds if the extraction time is sufficient. Nevertheless, the amount of EDTA-extractable iron is equal to the amount of iron extracted after 4–5 hours with ammonium oxalateat pH 3.0. From X-ray analysis, DTA curves, a solubility product determination, and a kinetic investigation, it is concluded that the EDTA-extractable fraction consists of X-ray amorphous iron oxide, less soluble than polymeric iron hydroxide, and presumably only one compound. Therefore, it is concluded that it may be possible by means of EDTA to carry out a selective extraction of X-ray amorphous iron oxides mixed with goethite and hematite.     

MOBILIZATION OF POTASSIUM FROM WASTE MICA BY PLANT GROWTH PROMOTING RHIZOBACTERIA AND ITS ASSIMILATION BY MAIZE (ZEA MAYS) AND WHEAT (TRITICUM AESTIVUM L.): A HYDROPONICS STUDY UNDER PHYTOTRON GROWTH CHAMBER

A hydroponics study was carried out to evaluate the effect of three plant growth promoting rhizobacteria (PGPR) namely, Bacillus mucilaginosus, Azotobacter chroococcum, and Rhizobium spp. on their ability to mobilize potassium from waste mica using maize and wheat as the test crops under a phytotron growth chamber. Results revealed that PGPR significantly improved the assimilation of potassium by both maize and wheat, where waste mica was the sole source of potassium. This was translated into higher biomass accumulation, potassium content and uptake by plants as well as chlorophyll and crude protein content in plant tissue. Among the rhizobacteria, Bacillus mucilaginosus resulted in significantly higher mobilization of potassium than Azotobacter chroococcum and Rhizobium inoculation. Overall, inoculation of maize and wheat plants with these bacteria could be used to mobilize potassium from waste mica, which in turn could be used as a source of potassium for plant growth.