SIZE FRACTIONATION, DISSOLUTION ANALYSIS, AND INFRA-RED SPECTROSCOPY OF HUMUS COMPLEXES IN ANDO SOILS     

TERUO HIGASHI  KOJI WADA 《European Journal of Soil Science》1977,28(4):653-663

Eight samples of Ando soil A₁ and buried A₁ horizons of different ages were fractionated into clay-, silt-, and sand-size separates, and the yields and carbon contents of these separates were determined. The clay-size separates were subjected to two series of successive extractions, 1) 0.1 M Na₄ P₂ O₇/2% Na₂ CO₃/0.5 M NaOH and 2) dithionite-citrate/2% Na₂ CO₃/0.5 M NaOH; and to difference infra-red spectroscopy for identification of the extracted constituents. The result indicated that humus evolves from forms with a very low complexing ability for Al and Fe into forms that complex Al and Fe in the A₁ horizon, and that humus further interacts with allophane-like constituents, allophane and imogolite in the buried A₁ horizon. These reactions between humus and inorganic constituents result in formation of silt- and sand-size aggregates which are stable to sonic wave treatment, but are broken down into finer particles upon boiling with H₂ O₂.  相似文献   

Association of cadmium,zinc, copper,and nickel with components in naturally heavy metal‐rich soils studied by parallel and sequential extractions     

《Communications in Soil Science and Plant Analysis》2012,43(7-8):1209-1230

Abstract

In this study, a new parallel and sequential extraction procedure was proposed to investigate the solubility of metals [cadmium (Cd), zinc (Zn), copper (Cu), and nickel (Ni)] and their association with soil components in naturally metal‐rich soils of Norway. Two different soils, alum shale (clay loam) and moraine (loam), developed on alum shale minerals were used. Each soil had two pH levels. For parallel and successive extractions, H₂O, 0.1M NH₄OAc (soil pH), 0.3M NH₄OAc (soil pH), 1M NH₄OAc (soil pH), and 1M NH₄OAc (pH 5.0) were used. A significant amount of Cd was extracted by NH₄O Ac related to concentration of NH₄OAc in the extracting solution. The amounts of Zn, Cu, and Ni extracted by these reagents were almost negligible except with 1M NH₄OAc (pH 5.0). Thus these metals were strongly bound to soil components. A seven step sequential extraction procedure was applied to evaluate the association of metals with soil constituents. The extractions were performed sequentially by extracting the soil with reagents having an increasing dissolution strength: 1M NH₄OAc (soil pH), 1M NH₄OAc (pH 5.0), 1M NH₂OH.HCl (in 25% HOAc), 1M NH₂OH.HCl (in 0.1M HNO₃), 30% H₂O₂ (in 0.1M HNO₃), 30% H₂O₂ (1M HNO₃), and aqua regia. In both soils at both pH levels investigated, appreciable percentages of total Cd (20–50%) were found associated with the NH₄OAc extractable fraction (mobile fraction). For Zn, Cu, and Ni, the percentage of total metal extracted with NH₄OAc was low (<4%), but it increased significantly by introducing a reducing agent (NH₂OH.HCl). The NH₂OH.HCl‐extractable fraction was the greatest fraction (>60%) for all four metals examined. These results suggest that among the metals studied, only Cd was easily desorbed from soil and should be considered mobile and potentially bioavailable. Other metals (Zn, Cu, and Ni) were strongly associated with the soil components and should be considered less available to plants. Using the sequential fractionation technique as a measure of availability, mobility and potential bioavailability of these four metals in the alum shale soils were: Cd>Zn>Ni>Cu.  相似文献   

Phosphorus amendment decreased cadmium (Cd) uptake and ameliorates chlorophyll contents,gas exchange attributes,antioxidants, and mineral nutrients in wheat (Triticum aestivum L.) under Cd stress     

Muhammad Arshad  Ali Noman  Qasim Ali  Muhammad Rizwan  Mujahid Farid 《Archives of Agronomy and Soil Science》2016,62(4):533-546

A 28-day pot (sand culture) experiment was carried to evaluate the effects of phosphorus (P) application in alleviating Cd phytotoxicity in wheat plants. Different levels of P (0, 10, and 20 kg ha^?1) were applied without and with 100 µM Cd. The results showed that 100 µM Cd concentration decreased plant biomass, chlorophyll contents, gas exchange attributes, and mineral nutrients in wheat plants. Cadmium stress increased tissue Cd and H₂O₂ concentrations. The activities of superoxide dismutases (SOD), peroxidase (POD) enzymes, increased while the activities of catalase (CAT), ascorbic acid (AsA), α-tocopherol, and phenolics decreased under Cd stress. Phosphorus supply increased shoot biomass, leaf area, photosynthetic pigments, and mineral nutrients and decreased Cd and H₂O₂ concentrations in shoots. Phosphorus application improved antioxidant enzyme activities and gas exchange attributes which emerged as an important mechanism of Cd tolerance in wheat. We conclude that P application contributes to decreased Cd concentrations in wheat shoots and increased gas exchange attributes and antioxidant enzymes and could be implemented in a general scheme aiming at controlling Cd concentrations in wheat for sustained production of this important grain crop.  相似文献   

Improved methods for selective dissolution of manganese oxides from soils and rocks   总被引：2，自引：0，他引：2  

A. Neaman  B. Waller  F. Mouélé  F. Trolard  & G. Bourrié 《European Journal of Soil Science》2004,55(1):47-54

Hydroxylamine hydrochloride (NH₂OH‐HCl) and hydrogen peroxide (H₂O₂) have been used in the past for selective dissolution of manganese oxide minerals. The methods reported, however, give poor recoveries. We tried to improve the methods in this respect. By stoichiometry, incomplete dissolution of Mn oxides is due to the lack of NH₂OH‐HCl added or to the lack of acid added in the case of H₂O₂ treatment. By increasing the amount of solution for a given amount of solid in the case of NH₂OH‐HCl and by increasing the acid concentration in the case of H₂O₂ treatment, we obtained rapid and complete dissolution of synthetic Mn oxides. The dissolution of natural samples, however, was slower than that of synthetic ones. Based on the results obtained, the improved methods are: (i) 0.1 m NH₂OH‐HCl, non‐acidified, 2 hours' stirring, and 1 g solid in 2 litres solution; (ii) 30% H₂O₂ in 0.5 m nitric acid, 0.5 hours' stirring, and 1 g solid in 1 litre solution. The improved methods achieved almost complete release of manganese from samples without decreasing the selectivity of dissolution.  相似文献   

Assessment of potentially reactive pools of aluminum in Andisols using a five-step sequential extraction procedure     

Qing-xia Dai  Noriharu Ae  Takeshi Suzuki  Mani Rajkumar  Shoko Fukunaga  Nobuhide Fujitake 《Soil Science and Plant Nutrition》2013,59(4):500-507

A five-step sequential extraction procedure was developed for the partitioning of soil aluminum (Al) into five fractions: exchangeable, weakly organic bound, strongly organic bound, inorganic non-crystalline and crystalline. The results obtained by the sequential extraction method for Al were compared with those estimated from single extractions using identical operating conditions applied in each individual sequential fraction. The Al content in the extracts was measured by inductively coupled plasma optical emission spectrometry. The results indicated that the first four steps [potassium chloride (KCl), copper chloride (CuCl₂), sodium pyrophosphate (Na₄P₂O₇), acid ammonium oxalate ((NH₄)₂C₂O₄)] in the sequential procedure could be as effective as single extraction methods at estimating exchangeable Al, weakly organic bound Al, strongly organic bound Al, and non-crystalline Al. However, the crystalline Al content by sequential procedure was not in agreement with single extraction procedures. Further, the sequential extractions resulted in more consistent estimates of the aluminum/silicon (Al/Si) molar ratio and allophane and crystalline Al contents than single extractions method. Results of X-ray diffraction on the soil samples confirm the presence of appreciable amounts of at least three types of crystalline minerals, including gibbsite, vermiculite or halloysite. Our result implies that the sequential method can be more reliable in estimating the various Al forms in Andisols.  相似文献   

Oxidative Stress Induced by Cadmium and Copper in Brassica rapa Leaves: Indicators of Stress,Oxidative Damage,and Antioxidant Mechanisms     

《Communications in Soil Science and Plant Analysis》2012,43(19):2475-2489

Brassica rapa is frequently used as a vegetable for human consumption and can accumulate metals that are bioavailable in soils. We studied the oxidative stress induced by 25 μM cadmium (Cd) and 50 μM copper (Cu) on Brassica rapa leaves and evaluated the intracellular antioxidative plant response mechanisms and the accumulation of these metals. With this purpose, hydrogen peroxide (H₂O₂) concentration, lipid peroxidation, and enzymatic and nonenzymatic responses was determined. The obtained results indicate that Cd and Cu induced different plant responses. Oxidative stress induced by Cu was characterized by increased lipid peroxidation and free proline levels. Guaiacol peroxidase and ascorbate peroxidase showed a relevant role in H₂O₂ removal. Cadmium did not influence lipid peroxidation, H₂O₂, proline and glutathione contents, and the enzymatic response mainly involves superoxide dismutase and ascorbate peroxidase. It was concluded that both excess Cu and Cd induced oxidative stress but plant response is characterized by different antioxidative response mechanisms.  相似文献   

Jasmonic acid alleviates negative impacts of cadmium stress by modifying osmolytes and antioxidants in faba bean (Vicia faba L.)     

Parvaiz Ahmad  Mohammed Nasser Alyemeni  Leonard Wijaya  Pravej Alam  Mohammad Abass Ahanger  Saud A. Alamri 《Archives of Agronomy and Soil Science》2017,63(13):1889-1899

We examined the role of jasmonic acid (JA) in faba bean under cadmium (Cd) stress, which reduces the growth, biomass yield, leaf relative water content (LRWC) and pigment systems. Hydrogen peroxide (H₂O₂) and lipid peroxidation (malondialdehyde [MDA]) levels increased by 2.78 and 2.24-fold, respectively, in plants under Cd stress, resulting in enhanced electrolyte leakage. Following foliar application to Cd-treated plants, JA restored growth, biomass yield, LRWC and pigment systems to appreciable levels and reduced levels of H₂O₂, MDA and electrolyte leakage. Proline and glycine betaine concentrations increased by 5.73 and 2.61-fold, respectively, in faba bean under Cd stress, with even higher concentrations observed following JA application to Cd-stressed plants. Superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase levels rose by 87.47%, 130.54%, 132.55% and 37.79%, respectively, with Cd toxicity, with further enhancement of antioxidant activities observed following foliar application of JA. Accumulation of Cd in roots, shoots and leaves was also minimized by external supplementation of JA. In conclusion, JA mitigates the negative impacts of Cd stress in faba bean plants by inhibiting the accumulation of Cd, H₂O₂ and MDA, and by enhancing osmolyte and antioxidant activities that reduce oxidative stress.  相似文献   

Differences in the Influence of Cadmium on the Decomposition of Various Types of Organic Materials in Soil     

Hiroyuki Hattori 《Soil Science and Plant Nutrition》2013,59(4):737-743

The influence of Cd on the decomposition of various types of organic materials in soil was studied. CdCl₂ or CaCl₂ (control) was added to a Gley soil at a level of 10 mmol kg^-1 soil. Three days later, organic materials including glutamic acid, glucose, casein, starch, cellulose, lignin, rice straw, rice straw compost, or 3 kinds of sludges were mixed with the soil in a proportion of 1%, respectively. During an 8-week period of incubation at 28°C, CO₂ evolution was measured periodically. At the end of the incubation period, the form of Cd in the soil was analyzed by successive extractions with water, CaCl₂, CH₃COOH, Na₄P₂O₇, and with hot HCl after HNO₃-HClO₄ digestion.

The decomposition of all the organic materials was inhibited by the addition of Cd, but the degree of inhibition varied considerably among the types of organic materials. The decomposition of rice straw, rice straw compost, and sludges was markedly inhibited by Cd. The amount of water-soluble Cd was less in the soils treated with rice straw, rice straw compost, and sludges than in the soils treated with other types of organic materials, while the amounts of CaCI₂-extractable Cd were much larger in the latter soils. In the case of rice straw, rice straw compost, and sludges Cd was easily adsorbed from the CdCl₂ solution.

These results suggest that the inhibition of organic matter decomposition by Cd is caused by the adsorption of Cd onto organic matter.  相似文献   

Evaluation of Multi-Mixtures of Acids for the Sample Preparation of Organic Soil Amendments for Multi-Element Determination by ICP OES     

Luiza G. R. Albuquerque  Alexandre M. Fioroto  Thiago R. L. C. Paixão 《Communications in Soil Science and Plant Analysis》2017,48(18):2210-2217

A method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwave-assisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO₃, HF, HBF₄, and H₃BO₃) combined or not with H₂O₂ were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO₃ + 1 mL HBF₄ + 2 mL H₂O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.  相似文献   

Effects of chemical and heat treatments on ethylene production in soil     

J.B. Sutherland  R.J. Cook 《Soil biology & biochemistry》1980,12(4):357-362

Factors influencing C₂H₄ production in a silt loam were investigated in an effort to determine the source of this gas in soil. Air-dried samples of soil in glass vials were moistened to about ?10 kPa, sealed with rubber septa, and incubated at 30 or 35°C with an original atmosphere of air or O₂-free N₂. C₂H₄ concentrations in the vials were determined by gas chromatography.Addition of the antibacterial agents chloramphenicol or novobiocin to the soil inhibited C₂H₄ production, whereas the antifungal agent cycloheximide had no effect. Sodium azide and sodium cyanide also reduced C₂H₄ production. Treatment of the soil with moist heat (i.e. passing a steam-air mixture through it) at 80°C for 30 min failed to reduce the ability of the soil to produce C₂H₄ during subsequent incubation at 30°C, but autoclaving it twice at 121°C prevented C₂H₄ production. As with nonheated soil, C₂H₄ production from soil treated at 80°C was prevented by novobiocin but not by cycloheximide. Only about 10% of the bacteria isolated from nontreated soil were spore-formers. In contrast, 95–98% and possibly more of the bacteria isolated from heat-treated soil were spore-formers, including those in soil which was heat-treated and then incubated moist at 30°C for an additional 3 days before dilution plating. Addition of methionine had no effect on the production of C₂H₄ in anaerobic soil, whereas ethionine, chlorogenic acid, and ethylenediaminetetraacetic acid (EDTA) all enhanced C₂H₄ production. Ethionine, but not chlorogenic acid or EDTA, also resulted in considerable C₂H₄ accumulation in autoclaved soil; the C₂H₄ detected in ethionine-amended soil was apparently nonmicrobial in origin. Soil samples incubated at constant temperatures of 30, 50, or 70°C all produced C₂H₄.The results collectively indicate that C₂H₄ in soil is most likely produced by facultative or strictly anaerobic bacteria which are probably spore-formers and may also be thermophilic. Several isolates of spore-forming bacteria were inoculated into autoclaved soil, but none produced appreciable amounts of C₂H₄ under the test conditions.  相似文献   

Role of Salicylic Acid in Alleviating Cadmium Toxicity in Rice Roots     

Bin Guo  Yongchao Liang  Zhaojun Li  Wei Guo 《Journal of plant nutrition》2013,36(3):427-439

In order to understand how salicylic acid (SA) is involved in modulating rice responses to cadmium (Cd) toxicity, particularly in Cd immobilization, a series of hydroponic experiments were conducted to examine changes in cell wall composition, activities of the enzymes related to lignin synthesis including phenylalanine ammonia-lyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO), subcellular Cd distribution, levels of hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and lignin and non-protein thiols (NPT) in rice roots under Cd stress with or without the pretreatment of SA. Results showed that Cd treatment decreased root biomass by 40% compared with the control (no Cd treatment) and pretreatment with SA significantly mitigated the Cd-induced inhibition of root growth. There was no significant difference in root cell wall composition or lignification between the treatment with Cd alone and the treatment with Cd with SA. No effects were observed for SA pretreatment on the activities of PAL, POD, or PPO under Cd stress. Furthermore, soluble Cd concentrations in root cells were significantly higher in the treatment with Cd with SA than in the treatment with Cd alone. However, H₂O₂ and MDA concentrations in rice roots were significantly lower but NPT levels were higher in the treatment with Cd with SA than in the treatment with Cd alone, which indicated that SA alleviated Cd-induced oxidative damage. It seems to suggest that SA-mediated enhancement of Cd tolerance was not due to enhanced Cd retention in the cell wall but to enhanced Cd bindings with thiols (─SH) group. The effects of SA-enhanced Cd tolerance were discussed with regard to H₂O₂ signaling pathways.  相似文献   

Continual pH lowering and manganese dioxide solubilization in the rhizosphere of the Mn-hyperaccumulator plant Chengiopanax sciadophylloides     

《Soil Science and Plant Nutrition》2013,59(6):726-733

Abstract

The Japanese woody plant Chengiopanax sciadophylloides is well known for its extraordinary accumulation of manganese (Mn), and is used as a model for studying Mn uptake and utilization by plants. To clarify the role of manganese dioxide (MnO₂) solubilization for Mn acquisition and further Mn hyperaccumulation in this plant, we examined the lowering of pH in the rhizosphere and Mn accumulation of this plant using regenerated plants. Plants regenerated from C. sciadophylloides calli lowered the pH of the culture broth continuously and simultaneously solubilized MnO₂ added to the medium. The Mn content of the plant increased up to 1,300 mg kg^?1 within 4 weeks of culture. Release of protein or specific organic acid from the roots was not observed. The medium used for plant culture maintained MnO₂ solubilization ability after removal of the plant; however, this ability was lost by adjustment to the same medium pH of pre-culture conditions. In addition, pH lowering and MnO₂ solubilization were suppressed by adding 1 mmol L^?1 of the plasma H⁺-ATPase inhibitor Na₃VO₄ to the medium, and completely inhibited when 5 mmol L^?1 of Na₃VO₄ was added. These results suggested that H⁺ leaking from plasma H⁺-ATPase plays an important role in MnO₂ solubilization in the rhizosphere of C. sciadophylloides and in Mn accumulation in this plant.  相似文献   

A convenient wet digestion procedure for multielement analysis of plant materials     

《Communications in Soil Science and Plant Analysis》2012,43(19-20):2595-2605

Abstract

For the determination of total element contents in plant material by atomic spectrometry after wet digestion, both dissolution and oxidation of the matrix are necessary. This was achieved by a sequential digestion procedure using first hydrogen fluoride (HF) for dissolution of silicate, followed by oxidation with nitric acid (HNO₃) and hydrogen peroxide (H₂O₂). The final solution is 0.2M HNO₃, and contains only traces of HF. Application of the method for the determination of aluminium (Al), boron (B), calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), lead (Pb), sulfur (S), and zinc (Zn) in various materials showed good agreement with certified reference materials.  相似文献   

Influence of pH,dispersion methods,and different compounds on adenosine triphosphate recovery from soil     

Gian Attilio Sacchi  Giovanni Valsecchi  Anna Farini  Sergio Cocucci 《Biology and Fertility of Soils》1993,16(3):238-242

We studied the recovery of ATP from soil. A soil-water suspension was prepared by two different methods (simple stirring or ballottini mill treatment) at different pH levels and in the presence of different chemicals [Na₂SO₄, Na₃PO₄, Na₅P₃O₁₀, adenosine, ethylenediaminetetra-acetic acid (EDTA), TRIS]. The ATP recovery was evaluated by adding [³H]-8 ATP to the solution and comparing the values obtained by radioactivity measurements with those obtained by an enzymatic assay. Strongly acidic (pH lower than 1.0) or alkaline (pH 10.0) extractions yielded the best ATP recoveries compared with intermediate pH values. At pH 10.0, the addition of Na₃PO₄ or Na₅P₃O₁₀ gave a high level of ATP recovery, 68 and 96%, respectively. No ATP hydrolysis occurred under alkaline extraction conditions. Under acidic extraction conditions, the addition of adenosine, EDTA, Na₂SO₄, or Na₅P₃O₁₀ improved ATP recovery but it was never higher than 34%. The results were discussed in terms of the effects of different physical and chemical conditions on cell disruption, ATP stability, ATP interactions with soil components, and ATP solubilization.  相似文献   

Amelioration of cadmium stress in gladiolus (Gladiolus grandiflora L.) by application of potassium and silicon     

Malik Muhammad Zaheer  Sajid Rashid Ahmad  Waheed Ullah Khan  Aqeel Ahmad  Aamir Ali 《Journal of plant nutrition》2018,41(4):461-476

Gladiolus corms were grown in media contaminated with cadmium (Cd) (50 mg kg^?1) and supplemented with silicon (Si) and potassium (K). The role of Si and K for mitigation of Cd toxicity was evaluated. Cd-induced stress generated significantly increased level of oxidative stress markers including hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) in gladiolus. The application of K and Si improved the production of protein and proline in the treated plants. Moreover, K and Si supplemented plants exhibited an improvement in the activity of antioxidant enzymes and a reduction in the level of MDA, H₂O₂ and Cd uptake under Cd stress. Application of K and Si also enhanced the uptake of mineral nutrients including calcium (Ca), magnesium (Mg), manganese (Mn), sulfur (S) and K. The plants supplemented with K and Si exhibited a higher amount of total phenolics and flavonoids. The combined effect of Si and K was more pronounced regarding beneficial effects on gladiolus plants compared to individual effect of these elements under Cd stress. The current research reveals that Si and K may improve gladiolus growth by decreasing the oxidative stress and Cd uptake and by increasing the activity of antioxidant defense enzymes, the quantity of secondary metabolites and plant nutrition.  相似文献   

Proper supply of S increases GSH synthesis in the establishment and reduces tiller mortality during the regrowth of Tanzania guinea grass used for Cd phytoextraction     

Flávio Henrique Silveira Rabêlo  Ricardo Antunes Azevedo  Francisco Antonio Monteiro 《Journal of Soils and Sediments》2017,17(5):1427-1436

  相似文献   

Stability of Fe- and Mn-(oxyhydr)oxides in Common Soil Dispersion Solutions     

Phung N. Manh  Moonis Ali Khan  Byong-Hun Jeon  Jae Gon Kim  Giehyeon Lee 《Water, air, and soil pollution》2011,217(1-4):677-687

Soil dispersion is a prerequisite process for the separation of metal oxides from bulk soil when magnetic separation is employed to enhance the efficiency for soil treatment. This study examined the stability of goethite, hematite, birnessite, and manganite in common dispersion solutions. The stability of pH in the oxide suspension decreased in the order carbonate (50 mM Na₂CO₃) > pyrophosphate (50 mM Na₄P₂O₇) > simple alkaline (1 mM NaOH) solutions regardless of the oxides. Dissolution of the four oxides was negligible in the carbonate and the simple alkaline solutions. In the pyrophosphate solutions, however, the oxides were subject to ligand-promoted dissolution by pyrophosphate ion. The extent of dissolution was highest for goethite followed by manganite, hematite, and birnessite. Dissolved Fe and Mn concentrations reached 68.3 and 4.1 ??M for goethite and manganite suspensions, respectively, in 21 days with 5 mM pyrophosphate. Higher pyrophosphate concentrations (up to 150 mM) did not substantially affect the extent of ligand-promoted dissolution due to the limited surface sites of the oxides. The results of this study suggest that the carbonate solution would be more desirable than the simple alkaline or the pyrophosphate solution for soil dispersion in the presence of common Fe or Mn oxides.  相似文献   

利用薄膜扩散梯度技术研究不同土壤性质影响下镉对黑麦草的生物有效性     

SONG Ning-Ning  WANG Fang-Li  MA Yi-Bing  TANG Shi-Rong 《土壤圈》2015,25(6):825-833

A generally accepted method for predicting the bioavailability and transfer of cadmium (Cd) from soil to plants has not yet been established. In this study, the diffusive gradients in thin films (DGT) and conventional extraction methods for metal fractions were used to investigate how effective these methods were at predicting Cd bioavailability to ryegrass (Lolium perenne) and to assess whether these holistic variables were independent of the soil property variables. The influences of soil properties on the predictive capabilities of the different methods were evaluated using multivariate statistics. The Cd concentrations in the shoots and roots of ryegrass correlated more closely with the effective Cd concentration measured by DGT (C_E), compared with those with soil total Cd, pore water Cd, and ethylenediaminetetraacetic acid disodium salt (Na₂EDTA)- and acetic acid (HOAc)-extractable Cd. When soil properties were included in a stepwise multiple linear regression, Cd transfer to L. perenne was negatively influenced by pH and positively influenced by organic matter (OM). The multivariate statistics showed that the adjusted correlation coefficients for the plots involving soil total Cd, pore water Cd, and Na₂EDTA- and HOAc-extractable Cd had been significantly improved after considering the influences of soil properties, which suggested that these methods were pH and OM dependent. For C_E, the relationship was pH independent or only dependent in strongly acidic soils. These results suggested that the main soil factors affecting bioavailability had the lowest impact on the DGT technique. Therefore, the DGT technique provided significant advantages over conventional methods when assessing Cd bioavailability.  相似文献   

Effects of Low-Level Aqueous Hydrogen Sulfide and Other Sulfur Species on Lettuce (Lactuca sativa) Seed Germination     

《Communications in Soil Science and Plant Analysis》2012,43(5):576-587

Low concentrations of aqueous hydrogen sulfide (H₂S) can stimulate growth of some crops. However, it is not clear whether H₂S provides crops with only sulfur and whether other sulfur compounds have similar beneficial effects. Therefore, impacts of solutions of sodium sulfate (Na₂SO₄), sodium sulfite (Na₂SO₃), sodium sulfide (Na₂S), ferrous sulfide (FeS), and H₂S at 0.01–1 mM were assessed on 5-day lettuce seed germination. Results showed that 0.01 mM H₂S solution significantly increased lettuce shoot elongation by 40 percent (to 43.6 mm from 31.0 mm in the control), whereas 0.1 mM increased elongation by 24 percent to 38.5 mm. Only a slight 10 percent increase was observed in 0.1 mM Na₂SO₄, suggesting that ameliorative impact of H₂S on plant growth was not a result of providing sulfur nutrient. Other sulfur solutions, however, inhibited lettuce germination and elongation to varying extents, hinting that H₂S might work as a signal molecule in regulating plant cellular activities.  相似文献   

Comparison of chemical fractionation methods for isolating stable soil organic carbon pools   总被引：4，自引：1，他引：4  

M. Helfrich    H. Flessa    R. Mikutta    A. Dreves  & B. Ludwig 《European Journal of Soil Science》2007,58(6):1316-1329

Stable soil organic matter (SOM) is important for long‐term sequestration of soil organic carbon (SOC), but the usefulness of different fractionation methods to isolate stable SOM is open to question. We assessed the suitability of five chemical fractionation methods (stepwise hydrolysis, treatment with H₂O₂, Na₂S₂O₈, NaOCl, and demineralization of the NaOCl‐resistant fraction (NaOCl + HF)) to isolate stable SOM from soil samples of a loamy sand and a silty loam under different land use regimes (grassland, forest and arable crops). The apparent C turnover time and mean age of SOC before and after fractionation was determined by ¹³C and ¹⁴C analysis. Particulate organic matter was removed by density fractionation before soils were exposed to chemical fractionation. All chemical treatments induced large SOC losses of 62–95% of the mineral‐associated SOC fraction. The amounts of H₂O₂‐ and Na₂S₂O₈‐resistant SOC were independent from land use, while those of NaOCl‐ (NaOCl + HF)‐ and hydrolysis‐resistant SOC were not. All chemical treatments caused a preferential removal of young, maize‐derived SOC, with Na₂S₂O₈ and H₂O₂ being most efficient. The mean ¹⁴C age of SOC was 1000–10000 years greater after chemical fractionation than that of the initial, mineral‐associated SOC and mean ¹⁴C ages increased in the order: NaOCl < NaOCl + HF ≤ stepwise hydrolysis ≪ H₂O₂≈ Na₂S₂O₈. None of the methods appeared generally suitable for the determination of the inert organic matter pool of the Rothamsted Carbon Model. Nonetheless, our results indicate that all methods are able to isolate an older, more stable SOC fraction, but treatments with H₂O₂ and Na₂S₂O₈ were the most efficient ones in isolating stable SOM.  相似文献