A simple method for detection of lipolytic microorganisms in soils

Media selective for the isolation of bacteria, actinomycetes and fungi were amended with 0.1% sunflower oil emulsified with 0.01% Tween 80. Lipase-producing microorganisms produced clear zones on these media. When lipase-producing bacteria were cultured on a polycarbonate membrane laid on the selective medium for bacteria, clear zones were produced on the medium when the membrane along with bacteria was removed. The agar disc cut from the clear zone also produced a clear zone when placed on the fresh medium, indicating that clear zone formation is the result of the activity of extracellular lipases. The largest population of lipase-producing microorganisms in an agricultural soil was actinomycetes followed by bacteria and fungi. Ranging from 12 to 75% of bacteria, actinomycetes and fungi isolates from soils collected from three different locations were capable of producing lipases. In general, relatively small percentages of soil bacteria were lipase producers, and lipase producers were more common among soil actinomycetes and fungi. These three groups of microorganisms appear to be all important in decomposition of oils in organic matters in soils.     

A fast and simple method for classification of soil bacterial populations

A simple method is described for a rough classification of soil bacterial populations. The method makes use of a commercially available biochemical test system and the test results are analysed in a multivariate classification program on a microcomputer. The method was used for classification of bacteria from rape rhizosphere.     

A simple method for assessing leaching risk of bacteria through soils

Abstract. Bacterial contamination of water is a problem worldwide and is often acute in developing countries where human and animal waste is disposed of on land for use as fertilizer or because of poorly developed sanitation systems. Studying leaching risk through soils is difficult when no suitable microbiological laboratory is available. A method using the movement of ZnO particles through soils as a surrogate for studying bacteria directly was tested. ZnO particles with a similar size to bacteria can readily be detected by chemical analysis. For a range of nine different soil textures, leaching rates of ZnO particles under near saturated conditions were significantly correlated with leaching rates of Escherichia coli cells ( P =0.013). For both ZnO and E. coli , leaching was generally greatest through fine textured soils.     

A simple laboratory infiltration method for measuring the tendency of soils to crust

Abstract. Rainfall simulation experiments give an indication of the tendency of soils to crust or seal but are time-consuming and require several kilograms of soil per sample. We developed a laboratory infiltration method that is less time-consuming than rainfall simulation and uses less than 40 g of soil. The method involves the leaching of an agitated 1:5 soil/water suspension through a packed soil column, which simulates the crusting process. The preparation of a dispersed soil suspension is a key feature of the method as it simulates disturbance of a soil surface by rain. This laboratory infiltration method was performed on sandy, granite-derived soils from annually burnt as well as unburnt plots in the Kruger National Park, South Africa and gave results which correlated strongly with results from rainfall simulation experiments on the same soils. We suggest that this new method may be useful for assessing the effect of different land management practices on the tendency of soils to crust.     

A simple and sensitive liquid chromatography-mass spectrometry confirmatory method for analyzing sulfonamide antibacterials in milk and egg

A simple and specific method able to identify and quantify traces of 14 sulfonamide antibacterials (SAs) in milk and eggs is presented. This method uses a single solid-phase extraction (SPE) cartridge for simultaneous extraction and purification of SAs in the above matrices. Milk and egg samples are passed through a Carbograph 4 sorption cartridge. After analyte desorption, an aliquot of the final extract is injected into a liquid chromatography-mass spectrometry (LC-MS) instrument equipped with an electrospray ion source (ESI) and a single quadrupole. MS data acquisition is performed in the positive-ion mode and by a time-scheduled multiple-ion selected ion monitoring program. Compared to two published methods, the present protocol extracted larger amounts of SAs from both milk and egg and decreased the analysis time by a factor of 3 with milk samples and by a factor of 2 with egg samples. Recovery of SAs in milk at the 5 ppb level ranged between 76 and 112% with relative standard deviations (RSDs) of 相似文献   

A simplified method for the extraction and analysis of available nitrogen,phosphorus, and potassium in soils

Abstract

Sodium bicarbonate (NaHCO₃) and calcium chloride (CaCl₂) are proposed as simultaneous extractants of available nitrate‐nitrogen (NO₃ ^‐‐N), phosphorus (P), potassium (K) in soils. Flow Injection methods were used for the determination of NO₃ ^‐ and P, and atomic emission spectroscopy for K. Parameters, such as reproducibility, precision, and recovery of the different extraction processes were studied. The usefulness of the proposed extractants was tested by applying them to different samples from the Spanish Soil Collection. The results obtained were compared with those provided after using the extractants recommended by the official methods. Sodium bicarbonate turned out to be suitable for the simultaneous extraction of NO₃ ^‐, P, and K in alkaline soils, whereas CaCl₂ was only advisable for NO₃ ^‐.     

A relatively simple scaling method for describing the unsaturated hydraulic functions of stony soils

Few if any methods exist to estimate the effects of stone content (stoniness) on the unsaturated soil hydraulic properties. A relatively simple scaling method is presented to estimate the hydraulic conductivity of unsaturated stony soils having different stone contents. A key assumption of the method is that van Genuchten's water retention parameters α and n of the fine soil fraction are the same as those of the stony soil. The method further assumes a linearly decreasing relationship between the saturated hydraulic conductivity and the stone content, based on previous numerical simulations. Using the proposed method, it is possible to calculate the hydraulic conductivity of unsaturated stony soils, knowing the saturated hydraulic conductivity of the fine soil fraction, the retention curve of the fine soil fraction, and the particular stoniness of the soil.     

Arginine ammonification,a simple method to estimate microbial activity potentials in soils

A simple, rapid and inexpensive method to determine microbial activity potentials, based on ammonification of arginine, was developed and tested on bacterial cultures and soil samples. The results are highly reproducible and correlate well with respiratory activities. Ammonification starts immediately after the addition of arginine and is linear for more than l h. Both properties show that physiological status and number of microorganisms remain stable during the assay.     

A simple and precise method for total chlorophyll analysis in tropical foliage plants 1

Methods currently in use for total chlorophyll analysis of plant tissue were reviewed. Storage of leaf tissue before analysis, filtration methods during analysis and extract longevity were investigated. The final procedure includes the use of leaf area cores and extraction with 100% acetone with results reported by area and oven dry weight. A simple and precise composite method was adopted.     

Liquid chromatographic method for analysis of elemental sulfur in pesticide formulations

A nonaqueous reverse-phase liquid chromatographic (LC) method has been developed to determine elemental sulfur in pesticide formulations. Samples were extracted in 50 mL of stabilized tetrahydrofuran (THF) by gentle swirling while sonicating for 1 min. A 5 microL aliquot was injected into the LC instrument equipped with a Vydac 218 TP 54 column. The mobile phase was methanol-acetonitrile-stabilized tetrahydrofuran (58.5 + 40 + 1.5). Sulfur was monitored at 280 nm. Retention time was approximately 5 min with total analysis time of 7 min. For 6 different products analyzed 12 times each, the coefficients of variations were all less than 3.5%. Purity of each sulfur peak was checked by using a photodiode array detector in the spectrum and absorbance ratio modes. No impurities were observed at the monitoring wavelength.     

A miniaturized curcumin method for the determination of boron in solutions and biological samples

Methods for the determination of boron require either sophisticated and expensive equipment (e.g. ICP-OES or ICP-MS) or a relatively large sample volume (e.g. spectrophotometric methods). A modified and miniaturized spectrophotometric curcumin method is presented which allows the determination of boron in sample volumes of 50—150 μl with a detection limit of 0.010 mg B l¹. The calibration curve is linear up to a concentration of 3 mg B l¹. Interferences with other ions are eliminated by extraction of boron with 2-ethyl-1,3-hexanediol in chloroform. Simultaneously, enrichment of boron in the sample can be performed within the same extraction step. Results show good reproducibility with a relative standard deviation of 15% at B concentrations between 0.05 and 0.40 mg B l^—1. In different types of solutions, recovery of added boron was in the range of 98 to 99%. For several plant materials containing from 18 to 58 μg B (g dw)¹, an overall relative standard deviation of 4.5% was established. So far, the method has been successfully applied to determine boron in waters, nutrient solutions, different plant parts (roots, stems and leaves) as well as in phloem sap and apoplastic washing fluid of several plant species.     

A simple bioassay for the diagnosis of aluminium toxicity in soils

Abstract

A bioassay procedure is described for diagnosing aluminium toxicity in soils using short term root growth in extracted soil solution. Soil solution is extracted from moist soil which has been incubated at “field capacity”; for 4 days. Soil solution extracted is divided into two portions, each of which is treated with CaCl₂ and H₃BO₃ to ensure that neither Ca nor B is limiting root growth. One portion is adjusted to pH 5.5 (pH adjusted treatment) with saturated Ca(OH)₂ solution. Aliquots (11 ml) of each portion are separately dispensed into each of five polypropylene tubes. Seedlings (in our experiment Glycine max cv. Forrest) of uniform root length are inserted into each tube (one per tube) and grown for 48 h. The increase in root length during the 48 h growth period (root elongation) in the unadjusted solutions is expressed as a percentage of that in the pH adjusted solutions to derive relative root elongation (RRE) ‐ an index of aluminium toxicity.

For 24 acidic surface soils, RRE using this soil solution bioassay was linearly correlated (r² = 0.96) with RRE obtained from a soil bioassay (with unamended, CaSO₄ and CaCO₃ treatments). The latter is commonly used to obtain an index of aluminium toxicity. The proposed procedure is less time consuming and tedious than the soil bioassay, and interpretation of the result is unambiguous.     

A method for identification and mapping potentially acid sulfate soils in Jutland, Denmark

A method for mapping potentially acid sulfate soils in Jutland, Denmark is described. First the wetlands were outlined, using already existing topographic maps. Then 7900 profiles, evenly distributed over the wetland areas, were examined to point out areas with potentially acid sulfate soils. The method used to identify potentially acid sulfate material was, for carbonate-free samples, a pH-measuring at the sampling time and after the samples were inoculated with soil water extract from an acid sulfate soil and 2, 8 or 16 weeks of incubation. For carbonate-containing samples the pyrite content was compared to the acid-neutralizing capacity. A map was constructed showing the ratio of profiles containing potentially acid sulfate soil samples to total number of profiles examined within natural geographical wetland regions.The investigation showed that 35% of the wetlands in Jutland have a high frequency of potentially acid sulfate soils.     

Qualitative aspects in the analysis of pesticide residues in fruits and vegetables using fast, low-pressure gas chromatography-time-of-flight mass spectrometry

Quantitative method validation is a well-established process to demonstrate trueness and precision of the results with a given method. However, an assessment of qualitative results is also an important need to estimate selectivity and devise criteria for chemical identification when using the method, particularly for mass spectrometric analysis. For multianalyte analysis, automatic instrument software is commonly used to make initial qualitative identifications of the target analytes by comparison of their mass spectra against a database library. Especially at low residue levels in complex matrices, manual checking of results is typically needed to correct the peak assignments and integration errors, which is very time-consuming. Low-pressure gas chromatography-mass spectrometry (LP-GC-MS) has been demonstrated to increase the speed of analysis for GC-amenable residues in various foods and provide more advantages over the traditional GC-MS approach. LP-GC-MS on a time-of-flight (ToF) instrument was used, which provided high sample throughput with <10 min analysis time. The method had already been validated to be acceptable quantitatively for nearly 150 pesticides, and in this study of qualitative performance, 90 samples in total of strawberry, tomato, potato, orange, and lettuce extracts from the QuEChERS sample preparation approach were analyzed. The extracts were randomly spiked with different pesticides at different levels, both unknown to the analyst, in the different matrices. Automated software evaluation was compared with human assessments in terms of false-positive and -negative results. Among the 13590 possible permutations with 696 blind additions made, the automated software approach yielded 1.2% false presumptive positives with 23% false negatives, whereas the analyst achieved 0.8% false presumptive positives and 17% false negatives for the same analytical data files. False negatives frequently occurred due to challenges at the lowest concentrations, but 70% of them involved certain pesticides that degraded (e.g., captafol, folpet) or otherwise could not be detected. The false-negative rate was reduced to 5-10% if the problematic analytes were excluded. Despite its somewhat better performance in this study, the analyst approach was extremely time-consuming and would not be practical in high sample throughput applications for so many analytes in complicated matrices.     

土壤中有效结合态氨的一种测定方法

Dynamics of fixed NH₄⁺ in NH₄⁺-treated soils incubated with glucose at 37±2 ℃ during the course of incubation and factors affecting it were studied. Results showed that content of fixed NH₄⁺ in soil reached a minimum on day 7 after incubation and then increased gradually regardless of the amount of glucose added and the kind of soil tested. However, the amount of fixed NH₄⁺ released from the soil at the given time varied with both the amount of glucose added and the kind of soil examined. In cases glucose was added at a rate of 10.0g C/kg soil, the amount of fixed NH₄⁺ retained in soil after 7 days of incubation was almost identical to that found by Neubauer test. Addition of K⁺ depressed the release of fixed NH₄⁺ significantly. Based on the results obtained a method for determining the content of available fixed NH₄⁺ in soils was proposed and the amount of N as available fixed NH₄⁺ in two soils measured by this method on an area profile-depth basis was presented.     

广西和福建荔枝园土壤农药残留现状研究

荔枝收获完毕后在广西壮族自治区及福建省荔枝主产区采集210 个荔枝园土壤样本, 检测了甲霜灵、代森锰锌、多菌灵、溴氰菊酯、氯氰菊酯、三氟氯氰菊酯、敌百虫、乐果和敌敌畏等9 种荔枝常用农药的含量。结果显示, 多菌灵是广西和福建荔枝园土壤最常检出的农药, 检出率分别为48.1%和84.0%。广西荔枝产区土壤代森锰锌、敌百虫和乐果均未检出, 其他5 种农药检出率均低于10%。福建荔枝产区甲霜灵和氯氰菊酯检出率均为24.0%, 其他6 种农药均未检出。广西荔枝产区土壤未检出或只检出1 种农药荔枝园分别占采样荔枝园的48.6%和38.4%, 福建荔枝产区分别占56.0%和8.0%; 检出2 种农药的广西荔枝园占11.4%,福建占32.0%。广西荔枝园土壤平均含量最高的农药为氯氰菊酯(5.0 μg·kg^-1), 敌敌畏次之(1.9 μg·kg^-1), 其他4 种检出农药不超过1.0 μg·kg^-1。福建荔枝园土壤平均含量为多菌灵(0.77 μg·kg^-1)>甲霜灵(0.65 μg·kg^-1)>氯氰菊酯(0.48μg·kg^-1)。虽然福建荔枝园土壤农药残留比广西普遍, 但两地荔枝园土壤农药残留仍属轻微。     

A method of capability evaluation for upland soils

Utilizing the data and materials accumulated in the project “Observations on Soil Fertility Changes” organized by Ministry of Agriculture and Forestry and executed by 16 Prefectural Agricultural Experiment Stations throughout Japan, an attempt was made to derive a prediction equation for soil loss due to erosion.

Five Prefectural Agricultural Experiment Stations provided us with rainfall records from which monthly rainfalls by three intensity grades, under 2 mm/10 min (LE2R), 2-4 mm 10 min (MEDRi) and over 4 mm/10 min (GT4R), were read. Multiple regression of log-transformed soil loss upon these rainfall data gave the following regression equation

Log soil loss = -0.783 0.0185**GT4R+0.00597**LE2R -0.00763**MEDR for which multiple correlation coefficient (R) was 0.74. The units of measurement were kg are for soil loss mm/month for LE2R, MEDR, and GT4R.

In order to account for the contribution of slope and soil factors to soil loss, Hayashi's theory of quantification No. I was applied after coding the relevant data. R of log-transformed soil loss on GT4R, MEDR, LE2R, slope, bulk density (BD), and texture (TEXT), reached 0.80. GT4R had the highest partial correlation coefficient, followed successively by MEDR, slope, and LE2R. Bulk density (BD) and texture (TEXT) were taken from among the data available to represent characters relevant to erosion, but they had onlv low partial correlations with soil loss in this Particular study.

The method developed in this study appears to be promising only if properly collected data are available. Conditions that should be satisfied in the planning of experiments for the purpose derivation of a prediction equation have been put forward.