Chemical methods of estimating plant available manganese in soils

Summary Twelve different chemical extraction procedures for extracting soil manganese were used. Soil test values determined for fourteen representative soil samples of Rajasthan State with manganese uptake by six crop species have shown that of the extractants used, 3N ammonium dihydrogen orthophosphate can be best used for estimating plant available soil manganese.     

Potential errors caused by roots in analyses of rhizosphere soil

Roots contain high concentrations of many elements, and have the potential to interfere with measurements of chemical change in rhizosphere soil. To assess potential interferences, maize (Zea mays L.) roots (free of soil) and soil (free of roots) were extracted separately with several extractants commonly used to assess the status of soil nutrients. The maize roots were grown within filter envelopes which prevented direct contact with soil, but permitted passage of mineral nutrients and water from the adjacent soil. Water, ammonium acetate (pH 7), DTPA (pH 7.3), Morgan's solution (pH 4.8), and dilute HCl were used as extractants. Most elements were released readily into soluble forms from roots killed by freezing to lyse the cells. Significantly lower amounts were extracted from fresh roots, with the greatest differences between fresh and killed roots for the extractants H₂O and DTPA, which were the mildest in terms of acidity and salt concentration. Extraction of P from the fresh roots by H₂O and HCL was particularly low. Contamination of rhizosphere samples with root materials would almost certainly prevent the accurate measurement of water-soluble P, K, Mn, Zn, Cu, and Na in the slightly alkaline soil used in this experiment. Large errors would be likely also for P, Mn, and Cu extracted by ammonium acetate. The DTPA extractant is normally used only for micronutrient metals or heavy metals, and the small amounts of these elements released by roots should not contribute to significant error. With Morgan's solution, errors would likely be large only for P. Dilute HCl is a reasonably strong extractant for many elements in soil, and major errors from roots contained in rhizosphere samples are unlikely. The relatively high probability of errors in extractions of soluble elements from rhizosphere soil is unfortunate, because these elements are among the most readily available to plants and the most likely to be altered by the normal activities of roots.     

Evaluation of single chemical extractants for the prediction of heavy metal uptake by barley in soils amended with polluted sewage sludge

The main aim of this study was to compare the suitability of three single chemical extractants [EDTA, CaCl₂ and the low-molecular-weight organic acids solution (LMWOAs)] to estimate Cu, Zn and Ni uptake by barley (Hordeum vulgare) from rhizosphere soils, following a single application of a metal salts-spiked sewage sludge. Thirty-six contrasting soils from different parts of Spain were amended with the same dose (15.71 g dry weight kg^-1) of polluted sewage sludge and sown with barley seeds under greenhouse conditions. Eight weeks after sowing, the plants were harvested and Cu, Zn and Ni were analysed in the roots. Heavy metal uptake was then compared with the theoretically available heavy metals in the rhizosphere soils, assessed by the three single chemical extractants. These three extractants alone failed to predict heavy metal uptake, and soil properties were needed to obtain accurate predictions. Thus, none of the methods tested in this study can be used as a universal soil extraction for estimating Cu, Zn and Ni uptake by barley.     

Influence of traffic pollution on ecological state of Plantago major L.

The data are presented concerning the amount of mobile compounds of chemical elements (ChE) in soils under various human impact (acetate-ammonium buffer at pH 4.8) and in plants of ripple-seed plantain (Plantago major L.) (extractants such as diluted 1:1 HCl, 10% HCl, distilled H₂O). The content of total ash, mineral impurities of soil origin, water-soluble forms of ChE, polysaccharides and chlorophyll was determined in plants. The obtained data were compared with those for other regions. The ecological state of Plantago major L. was estimated and a conclusion was drawn about its possible use as a medicinal raw material.     

Chemical activity and biological effect of sludge-borne heavy metals and inorganic metal salts added to soils

Summary A greenhouse experiment was conducted in order to evaluate the chemical activity and the uptake by Italian ryegrass (Lolium perenne cv. S24) of Zn, Cu, Cd and Ni added to a sandy and a heavy clay soil in two different forms: as inorganic salts and sludge-borne.The chemical activity of heavy metals as evaluated with different extractants was higher for the inorganic salt treatment and for the sandy soil, indicating that the chemical form of the metal and soil characteristics largely affect their extractability.The different chemical activity was also reflected in plant uptake. For all metals the degree of plant accumulation decreased in the following order: sandy soil-salt sandy soil-sludge> clay soil-salt>clay soil-sludge.These findings indicate that caution must be used when using results of inorganic salt treatments and different soil types to evaluate plant uptake of heavy metals from sludge amended soils.     

土壤化学性质对Cu的植物吸收效应和土壤有效Cu测定的影响

在华北平原石灰性土壤中,盆栽小麦的生物相关性检验证明,常用的SB/D联合浸提剂或AB/D联合浸提剂,与植物的吸Cu量均无显著相关关系,不适合直接用来测定土壤有效Cu.校正土壤pH和有机质含量之后,SB/D侵提剂与吸Cu总量的相关性则达到P＜0.01的极显著水平,可用于土壤有效Cu的评价.土壤pH越高则小麦吸收的Cu越少;土壤pH升高1个单位,则土壤有效Cu吸收量平均减少19μg·盆^-1.土壤pH升高和有机质含量增加,土壤有效Cu的测定结果分别减小和增大.     

A suitable extractant for assessing plant-available copper in different soils (peaty,red and alluvial)

Summary Relative efficiency of five chemical extractants for the extraction of available Cu in four different soils and its uptake by rice seedlings was studied in a pot culture experiment. The Cu extracted by 0.1N HCl showed significant relationship with plant uptake whereas the values for other extractants except 0.05M EDTA did not approach the level of significance. Among the soil properties studied, pH and CaCO₃ correlated negatively and organic matter and CEC positively with Cu uptake by rice plants.     

The Influence of Heat Processing and Mechanical Disintegration on Yeast for Single-Cell Protein

Yeast was processed by means of different technical drying procedures, heating in water suspension, and mechanical disintegration. The influence on the ultrastructure, the nutritive value and on the availability of the cell nitrogen-containing compounds to chemical extractants was studied. On micrographs no cell wall disrupture could be observed after any of the heat treatments. The internal cell structure was affected at the higher temperatures. After drum drying this structure was destroyed to a large extent. The heat treatments increased the nutritive value compared to unheated yeast cells but did not increase the availability of the cell content to chemical extractants. Mechanical disintegration increased both the nutritive value and the availability to chemical extractants. Heat processes and mechanical disintegration give high nutritive value to the yeast. Mechanical disintegration is advantageous when processing steps such as extraction with chemicals are necessary for obtaining specific protein products.     

Determination of triasulfuron in soil: affinity chromatography as a soil extract cleanup procedure

Triasulfuron forms one of the group of sulfonylurea herbicides. These are used widely for controlling weeds as they are effective at very low application rates. This effectiveness is responsible for the crop losses due to persistence of trace amounts of the herbicides (≤100 pg/g) in the soil. The numerous immunoassays described have been constrained by the fact that the soil extract contains co extractants which interfere in the assays, so much so, that these assays are useless at low levels of herbicide. We describe here the preparation and application of an immunoaffinity column which binds specifically to triasulfuron, thus cleaning up the soil extract. The experiment design is such that this also leads to concentration of the triasulfuron, making it easier to assay reliably using ELISA. Six different soil types were used to validate this procedure. In most cases, the herbicide content could be detected at 100 pg/g (critical phytotoxic herbicide level in soil) with a variation of ±20% in the readings.     

Manure Application and Cannabis Cultivation Influence on Speciation of Lead and Cadmium by Selective Sequential Extraction

The contamination of agricultural soils by heavy metals is a worldwide problem. Degradation of organic matter (OM) from organic amendments used in the remediation of metal-contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of four differing organic amendments on chemical forms of Pb and Cd in a contaminated soil were investigated in a pot experiment of control unamended soil and soils amended with dry cow and poultry manures (20 g CM or PM kg^?1 soil), and cow and poultry manure extracts (2 g CME or PME kg^?1 soil) cultured with cannabis sativa. After eight weeks, a sequential extraction scheme was used to fractionate soil Pb and Cd into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), and carbonates associated (ACar) forms. The addition of animal manures and their extracts increased the DTPA-extractable Pb and Cd in soil significantly. Soil Pb and Cd in Sol-Exch fraction were increased by manure applications. Both Pb and Cd in AOM fraction were increased by application of manures and their extracts. This increase was more obvious for Pb in application of cow and poultry manure extracts. The ACar chemical forms of Pb and Cd were also increased by application of manures and their extracts. The increases of Pb and Cd in Acar fraction was noticeable in soils treated with cow manure. Soil cultivation with cannabis sativa increased available, Sol-Exch, and AOM chemical forms of Pb in soil significantly compared to control soil. However, soil Pb and Cd in ACar fraction were decreased significantly by cannabis cultivation. The effect of cannabis cultivation on all of the Cd chemical forms (except on Sol-Exch) was similar to the results of Pb chemical forms. Plant cultivation had no significant effect on Cd in Sol-Exch chemical form.     

Chemical Extraction of Arsenic and Heavy Metals from Contaminated Soils Under High Temperature and Pressure Conditions in Abandoned Mines in South Korea

The chemical extraction of As and heavy metals from contaminated soils, sampled from the Geopoong and Keumpoong mines in South Korea, was investigated under subcritical conditions. Soil samples from the abandoned mines were heavily contaminated with As, Cd, Cu, Pb, and Zn. The extent of metal removed from the contaminated soils by extractants varied according to the chemical forms of the metals in the soils. When temperature increased, the extraction of As increased accordingly, showing 92-100% removal with 100 mM of NaOH at 300°C. In contrast, the extraction of cationic metals by citric acid and ethylenediaminetetraacetic acid (EDTA) decreased markedly at 200–300°C because their chelating ability was decreased via decarboxylation and dehydration at high temperatures. Furthermore, the extraction of cationic metals was significantly affected by solution pH. Our results suggest that chemical extraction of cationic metals under subcritical conditions may be affected by several factors, including character of metal, type of extracting reagent, existing forms of metal in the soil, temperature, and soil pH.     

Chemical transformation of Kamchatka soils after input of products of volcanic eruption

It has been revealed that changes in the chemical composition of soils after the input of volcanic ash under conditions of a cold humid climate depend on granulometric and lithogeochemical compositions of eruption products, the ways and forms of the input of chemical elements to soil, the period of the year, and weather conditions at ash falls. The lithogeochemical composition of ash mainly determines the type of change in the total composition of soils. Variations in the contents of mobile forms of elements depend mainly on the period of year and meteorological conditions during ash falls. Most mobile compounds (99.3%) of many elements are transported to soil upon ash falls not as components of ash particles, but in gas- and watersoluble forms directly from the dispersion medium of the volcanic aerosol. The following regularities were revealed in soils at a distance of 25 km from the centers of eruption: (i) the increase in the total contents of elements and the removal of their mobile forms in winter and (ii) the accumulation of mobile compounds, a drop in their total compounds, and soil acidification with a significant (about 1.5 times) decrease in the degree of base saturation of soils in summer.     

A common chemical extractant for estimating plant-available zinc in different soil types (peaty,red and alluvial)

Summary Relative efficiency of five chemical extractants for the extraction of available Zn in four different soils and its uptake by rice seedlings was studied in a pot culture experiment. The Zn extracted by dithizone-ammonium acetate showed a significant relationship with plant uptake whereas the values for other extractants except NH₄OAc (pH4.8) did not approach the level of significance. Among the soil properties studied, pH and CaCO₃ correlated negatively and organic matter and CEC positively with Zn uptake by rice plants.Contribution from the Soil Science and Agricultural Chemistry Dept., Banaras Hindu University, Varanasi-221005, India.Lecturer and Research Scholar of the Soil Science and Agricultural Chemistry Department, respectively.Lecturer and Research Scholar of the Soil Science and Agricultural Chemistry Department, respectively.     

Chemical speciation of Zn in acidic soils: suitable soil extractant for assessing Zn availability to maize (Zea mays L.)

Abstract

Chemical fractions of soil Zn namely: water soluble (WS), exchangeable (EX), Pb displaceable (Pb-disp.), acid soluble (AS), Mn oxide occluded (MnOX), organically bound (OB), amorphous Fe oxide occluded (AFeOX), crystalline Fe oxide occluded (CFeOX), residual (RES) were determined in 20 surface (0–15 cm) samples of acidic soils from the provinces of Uttarakhand and Uttar Pradesh, India. The chemical fractions of soil Zn in acidic soils were found to be in the following descending order of Zn concentration: RES > CFeOX > Pb-Disp. > AFeOX > MnOX > AS > OB > EX > WS. These soil samples were also extracted by: DTPA (pH 7.3), DTPA (pH 5.3), AB-DTPA (pH 7.6), Mehlich 3 (pH 2.0), Modified Olsen, 0.01 N CaCl₂, 1 M MgCl ₂ and ion exchange resins. Chemical fractions and the soil extractable content of Zn estimated by different soil extractants were significantly correlated with some general soil properties. Maize (cv. Pragati) plants were grown in these soils for 35 days after emergence and Zn uptake by plants was compared with the amount of Zn extracted by different soil extractants and chemical fractions of Zn. Among chemical fractions of soil Zn, Pb-displaceable and acid soluble chemical fractions of soil Zn showed a significant and positive correlation with Zn uptake by maize. Path coefficient analysis also revealed that the acid soluble Zn fraction showed the highest positive and direct effect on Zn uptake (P=0.960). Among different multinutrient soil extractants evaluated for their suitability to assess Zn availability in acidic soils, DTPA (pH=5.3) was most suitable soil extractant, as the quantity of soil Zn extracted by this extractant showed a significant and positive correlation with the dry matter yield, Zn concentration and uptake by maize plants.     

土壤微量元素测试及其应用

土壤微量元素测试在其发展历史过程中,不断改进技术,逐渐深入地揭示土壤供给微量元素的能力,对指导施肥和保护生态环境起着积极的作用。现代测试手段发展到广泛采用原子吸收光谱(AA)和电感耦合等离子体发射光谱(ICP),但比色法(光度法)和极谱法不仅设备比较简便,而且新的显色剂、催化系统等方面的研究进展,使其对某些元素的测定灵敏度和准确度超过AA和ICP,从而在微量元素测试技术中仍占据一定地位。土壤溶液抽取技术虽然有所改进,但有效态微量元素仍然主要是选用适当提取剂来提取测定。临界值和分级标准的确定是应用测定值的桥梁。作者曾采用全幅分级标准分级制图,确定缺素面积和需肥区域,再根据土壤含量水平和增产幅度之间的函数关系预测增产效果和投入的经济效益。     

Review of methodologies for extracting plant-available and amorphous Si from soils and aquatic sediments

There is a variety of methodologies used in the aquatic sciences and soil sciences for extracting different forms of Si from sediments and soils. However, a comparison of the published extraction techniques is lacking. Here we review the methodologies used to extract different Si fractions from soils and sediments. Methods were classified in those to assess plant-available Si and those to extract Si from amorphous silica and allophane. Plant-available Si is supposed to comprise silicic acid in soil solution and adsorbed to soil particles. Extraction techniques for plant-available Si include extractions with water, CaCl₂, acetate, acetic acid, phosphate, H₂SO₃, H₂SO₄, and citrate. The extractants show different capabilites to desorb silicic acid, with H₂SO₃, H₂SO₄ and citrate having the greater extraction potential. The most common extractants to dissolve amorphous silica from soils and aquatic sediments are NaOH and Na₂CO₃, but both also dissolve crystalline silicates to varying degrees. In soils moreover Tiron is used to dissolve amorphous silica, while oxalate is used to dissolve allophanes and imogolite-type materials. Most techniques analyzing for biogenic silica in aquatic environments use a correction method to identify mineral derived Si. By contrast, in the soil sciences no correction methods are used although pedologists are well aware of the overestimation of amorphous silica by the NaOH extraction, which is most commonly used to extract silica from soils. It is recommended that soil scientists begin to use the techniques developed in the aquatic sciences, since it seems impossible to extract amorphous Si from soils completely without dissolving some of the crystalline silicates.     

Auxiliary phase guidelines for microbial biotransformations of toxic substrate into toxic product

When an industrial process is developed using the microbial transformation of a precursor into a desired chemical compound, high concentrations of substrate and product will be involved. These compounds may become toxic to the cells. In situ product removal (ISPR) may be carried out, using auxiliary phases such as extractants or adsorbents. Simultaneously, in situ substrate addition (ISSA) may be performed. It is shown that for uncharged substrates and products, the aqueous solubilities of substrate and product can be used to predict if ISPR might be required. When a particular auxiliary phase is selected and the distribution coefficients of substrate and product are known, it is possible to estimate a priori if this auxiliary phase might be good enough and how much of it might be needed for an efficient (fed-)batch biotransformation process. For biotransformation products of intermediate polarity (aqueous solubility of about 1-10 g/L) there seems to be a lack of extractants and adsorbents with the capacity to raise the product concentrations to commercially more interesting levels.     

Extraction of P solubilizing active substances from the cell wall of groundnut roots

Groundnut can take up more phosphorus (P) from a low P soil that hardly contains plant available iron-bound P (Fe-P) as its major P form than other crops. This is considered to be caused by the presence of substances in the root cell wall (CW) that are able to solubilize P. A method for extraction of these phosphorus solubilizing active substances (PSAS) from the root CW of groundnut is described in this paper. Acid, alkaline and water extractants were used, but only a treatment with 1 M NaOH at 80 °C for 24 h was found to be appropriate to extract the PSAS from the root CW. The characteristics of the CW and the extracted CW components were compared. The P solubilizing activity of both decreased sharply after addition of Fe³⁺, whereas Ca²⁺ and Mg²⁺ had no effect. This similarity in chemical characteristics suggested that we had successfully extracted the active substances in the CW. Phosphorus-solubilizing compounds were also extracted from the root CW of other crops like soybean, pigeon pea and maize, but these other crops contained less PSAS than groundnut. Using gel permeation and anion exchange column chromatography, the CW components were purified for HPLC analysis. The HPLC analyses indicated that two common retention times for the active substances existed for all four crops. The significance of the root CW in plant P nutrition is discussed.     

Comparison of Whole-Cell Fatty Acid (MIDI) or Phospholipid Fatty Acid (PLFA) Extractants as Biomarkers to Profile Soil Microbial Communities

The whole-cell lipid extraction to profile microbial communities on soils using fatty acid (FA) biomarkers is commonly done with the two extractants associated with the phospholipid fatty acid (PLFA) or Microbial IDentification Inc. (MIDI) methods. These extractants have very different chemistry and lipid separation procedures, but often shown a similar ability to discriminate soils from various management and vegetation systems. However, the mechanism and the chemistry of the exact suite of FAs extracted by these two methods are poorly understood. Therefore, the objective was to qualitatively and quantitatively compare the MIDI and PLFA microbial profiling methods for detecting microbial community shifts due to soil type or management. Twenty-nine soil samples were collected from a wide range of soil types across Oregon and extracted FAs by each method were analyzed by gas chromatography (GC) and GC-mass spectrometry. Unlike PLFA profiles, which were highly related to microbial FAs, the overall MIDI-FA profiles were highly related to the plant-derived FAs. Plant-associated compounds were quantitatively related to particulate organic matter (POM) and qualitatively related to the standing vegetation at sampling. These FAs were negatively correlated to respiration rate normalized to POM (Resp_POM), which increased in systems under more intensive management. A strong negative correlation was found between MIDI-FA to PLFA ratios and total organic carbon (TOC). When the reagents used in MIDI procedure were tested for the limited recovery of MIDI-FAs from soil with high organic matter, the recovery of MIDI-FA microbial signatures sharply decreased with increasing ratios of soil to extractant. Hence, the MIDI method should be used with great caution for interpreting changes in FA profiles due to shifts in microbial communities.     

The fractionation of iron-phosphorus compounds in sediments studied by Mössbauer spectroscopy

Iron compounds of phosphorus form a large part of the phosphorus bound in sediments. Mössbauer spectroscopy is a technique that enables us to study, directly, chemical forms of iron in solid samples. Mössbauer spectroscopy allowed us to check, directly, the selectivity of the extraction scheme for soil phosphorus proposed by Chang &; Jackson (1957), but only as far as the iron compounds are concerned. It appears that selectivity of the extraction method leaves much to be desired.