Cation exchange properties of soils derived from lignite ashes

In Saxony‐Anhalt, Germany, an area of about 6000 ha is covered by lignite‐ash‐derived substrates. In some cases, pollutants like heavy metals or toxic organic compounds had been disposed of together with the lignite ashes. For this reason, we assessed factors influencing the cation exchange capacity (CEC) of lignite‐ash substrates exposed to natural weathering. We chose four research sites reflecting the different methods of disposal: two dumped landfills and two lagooned ashes of different ages. After determining the CEC at pH 8.1 (CEC_pot), we evaluated the influence of the content of silt and clay and the content of total organic C. As lignite‐ash‐derived substrates are rich in oxalate‐extractable Si, Al, and Fe, we performed an oxalate extraction and determined afterwards the CEC_pot to assess the contribution of oxalate‐soluble compounds to the CEC_pot. Moreover, we determined the variable charge of selected samples at pH values ranging from 4 to 7. The lignite‐ash‐derived soils had a high CEC_pot with means ranging from 25.1 cmol_c kg^–1 to 88.8 cmol_c kg^–1. The influence of the parent material was more important than the degree of weathering. The content of total organic C consisting of pedogenic organic matter and coked lignite particles together with the content of silt and clay played a statistically significant role in determining the CEC. Another property that influenced the amount of CEC in medium textured lignite ashes was the content of oxalate‐soluble silica and aluminum. After oxalate extraction, they lost about 30% of their CEC due to the dissolution of oxalate‐soluble compounds. In coarse textured lignite ashes, oxalate extraction led to higher amounts of CEC, probably due to an increase of surface area resulting either from the disintegration of particles or from etching caused by insufficient dissolution of magnetite and maghemite. Moreover, lignite‐ash‐derived substrates exhibit a high amount of pH‐dependent charge. The CEC decreased by 40% in a topsoil sample and by 51% in a subsoil sample as the pH declined from 7 to 4.     

Synthesis of zeolite from waste lignite ash from Thailand

Almost all the lignite ash from the coal thermal power plants in Maemoa, Lumpang Province, Thailand is disposed of as solid wastes. However, the number of reclaimed sites for the disposal of the wastes is not sufficient to handle the large amount of wastes. Therefore, the development of a technique for the utilization of lignite ash is essential to preserve the environment and to recycle the waste materials. Lignite ash is composed of inorganic compounds mainly present as glasses resulting from fusion during their combustion. The chemical composition of these glasses is similar to that of volcanic glass in nature and changes easily to zeolite-like substances by hydrothermal treatment with an alkali. Henmi (1987) reported the synthesis of hydroxysodalite, a kind of zeolite, from waste coal ash. Zeolites are crystalline, hydrated aluminosilicates with a three-dimensional crystal structure and have the attractive cation-exchange properties in agricultural applications (Ming and Mumpton 1989). In the present study, attempts were made to synthesize zeolitelike substances from lignite ash from Thailand, in order to develop a new method for the disposal of industrial wastes. Although the synthesis of zeolite-like substances from waste coal ash had been reported in different countries after the publication of Henmi (1987), this method was applied for the first time in Thailand for the treatment of lignite ash.     

Phosphorus sorption maxima and desorbability in selected soils with andic properties from the Azores, Portugal

P sorption and desorption capacities were determined on 30 soil horizons (surface and subsurface) of soils with andic properties from the Azores, Portugal, using the Langmuir equation and successive extractions with dilute calcium chloride (CaCl₂), respectively. The proportion of P recovery (Prec) using distilled water (H₂O), CaCl₂, Bray 2 (B2), Mehlich 3 (M3), Egnér–Riehm (ER) and Olsen (OL) extractants was also determined to assess the extent of P release from soils enriched with P at P sorption maxima (Pm). Soils containing very low amounts of organic C and allophane (Vitrandic Haplustepts and Vitrandic Udorthents) showed the lowest values of Pm (48–565 mg kg^− 1) and the highest values of P desorbability (Pdes) (69–100%), indicating that P can be easily lost from these soils. Application of fertilizers to these soils should be restrained in order to minimize eutrophication risk of nearby water bodies. In contrast, allophanic and non-allophanic horizons of Typic Placudands, Alic Hapludands, Acrudoxic Hapludands and Acrudoxic Hydrudands showed much higher values of Pm (2273–52,400 mg kg^− 1) and lower values of Pdes (4–57%).They also showed low proportions of Prec by the used extractants, indicating that large amounts of P can be sorbed in an unavailable form. Thus, these soils may require large amounts of P fertilizers and an efficient method of P application. Other studied soils with high amounts of 1:1 layer silicate minerals and having weak andic properties (Typic and Andic Haplustepts), showed intermediate Pm (1124–8333 mg kg^− 1) and Pdes values (20–63%).

The values of Pm were positively correlated with Al_d, Al_o, allophane, Fe_o, Fe_d and Al_p contents, and with the values of Al_o + 1/2 Fe_o. In contrast, values of Pdes were negatively correlated with these soil constituents. Of the six extractants, the B2 extractant showed generally higher proportions of Prec than the other extractants in most studied soils. The proportions of Prec by the B2, M3, ER and OL extractants were negatively correlated with contents of Fe_o, Fe_d, Al_d, Al_o, Al_p, and Fe_p, and with the values of Al_o + 1/2 Fe_o and PR.     

Proposed revisions to the diagnostic critera for andic and vitric horizons and qualifiers of ardosols in the world reference base for soil resources

World Reference Base for Soil Resources (WRB) was published in 1998 and has begun to be used all over the world. We examined the definitions of andic and vitric horizons and qualifiers (lower-level units) of Andosols in the WRB by using the Tohoku University World Andosol Database (TUWAD) and proposed several revisions. Among 5 items of the definition for the andic horizon, we considered that the requirements of clay and volcanic glass contents should be deleted due to the difficulty in their accurate determination with the progression of soil weathering. In relation to this revision, correction of vitric horizon was also proposed. Although two major types of andic horizons, silandic and aluandic, are specified in the andic horizon definition, the aluandic type is not included in the qualifiers. Because aluandic volcanic ash soils have unique properties and are extensively distributed, the aluandic qualifier should be included in the lower level units of Andosols. Soil texture is used for the definition of arenic, luvic and vatic qualifiers. Therefore, these qualifiers should be modified or deleted. Both melanic and fulvic qualifiers are required to obtain the Munsell color value (moist) and chroma of 2 or less. To distinguish fulvic Andosols from melanic Andosols, the Munsell color and melanic index requirements for a fulvic horizon should be modified. Since Andosols with buried non-Andosols occur in a significantly large area, the thaptic qualifier should be used.     

Andosols and soils with andic properties in the German soil taxonomy

The presence of soils with andic properties on German territory has been suspected for decades and there are numerous reports of sites where they may potentially occur. Andic properties, however, are not adequately represented by the German soil‐classification system. The German taxonomic category “Lockerbraunerde” has not been revised or reconciled with international taxonomic categories since the year 1957, when it was initially proposed. With this review, we show that there are true Andosols of both the silandic (allophane‐containing) and the aluandic (Al‐Humus‐dominated) type in Germany and that their properties differ substantially from other soils which merely exhibit low bulk density. By (1) comparing soil carbon storage between some German Andosols, Chernozems, and nonandic Cambisols with particularly low bulk density and (2) elucidation of the differential pedogenetic pathways leading to Andosol formation, we further demonstrate that Andosols are important objects of study in research issues of contemporary interest. We propose that appropriate measures be taken to lay the foundations for the protection and conservation of these soils, because they are valuable as archives of natural history and provide opportunities to study unique soil processes.     

Studies on the properties of organic matter in buried humic horizon derived from volcanic ash

To investigate the relationship between age and the sugar composition in hydrolysates of the surface horizon and buried humic horizons with age up to 28,000 years B.P., the neutral sugars and amino sugars in soil hydrolysates were determined.

The ratios of total sugar carbon content to total carbon content of soil ranged from 2.68 to 4.13 percent. These values showed no distinct relationship with age.

Rhamnose, fucose, arabinose, xylose, mannose, galactose, glucose, g1ucosamine and galactosamine were present in the hydrolysates of all soil samples.

The polysaccharides of soil samples which have been buried for shorter periods were dominated by glucose, while those of soil samples buried for longer periods were dominated by mannose.

The proportion of hexoses showed a tendency to increase with age, while that of pentoses showed a tendency to decrease with age.     

Studies on the properties of organic matter in buried humic horizon derived from volcanic ash

Abstract

Humic acids were extracted from the surface horizon Yu 1 and buried humic horizons (Yu 2, 800-864 AD; Yu 4, ca. 4,000 years B.P.; Yu 6, 7,000 years B.P.; Yu 7, ca. 10,000 years B.P.). The humic acids were filtered with ultramembranes with 20, 10, 5, 1 or 0.1 × 10' M.W. in this order and separated into five fractions; (>20), (20-10), (10-5), (5-1) and (1-0.1) × 10⁴ M.W. fractions. The elementary composition, functional groups, optical properties, and hydrolyzable total- and sugar-carbon contents of each humic acid fraction were determined, and the changes in properties of the humic acid with age after burial were discussed.

In horizons Yu 1 to Yu 6, the patterns of M.W. distribution of the >20 × 10⁴ to (1- 0.1) × 10⁴ fractions were rather similar. In contrast, Yu 7 was characterized by the predominance of (1-0.1) x 10' M.W. fraction and the presence of a small amount of <0.1 × 10⁴ M.W. fraction.

The chemical properties of humic acid (HA) fractions of each humic horizon and their changes with age after burial were as folIows:

1) Elementary composition of HA fractions of each humic horizon was rather similar to each other. The C% and C/N ratio increased, and the H%, N% and H/C ratio decreased in all HA fractions with age.

2) Total acidity and carboxyl contents of HA fractions of Yu 1 were higher in the lower M.W. fractions. These values increased with age up to Yu 4 or Yu 6 horizons, then decreased in the Yu 6 or Yu 7 horizon. The contents of carbonyl groups in all the HA fractions which were very low in Yu 1, showed a wide range of variations in Yu 2, intermediate values from Yu 4 to Yu 6 horizons then decreased in the HA fractions of Yu 7, except for the (>20) fraction.

3) The degree of humification of the HA fractions of Yu 1 judging from the RF and \sDlogK values, tended to be higher in higher M.W. fractions, and increased in all the HA fractions with age after burial.

4) Hydrolyzable total- and sugar-carbon contents were high in the HA fractions of Yu 1 and decreased with age.

5) Changes of elementary composition, degree of humification and hydrolyzable total- and sugar-carbon contents were conspicuous from the Yu 1 to Yu 2 horizons, and less significant afterwards.

6) The 0%, C/O ratio and phenolic OH content did not show any consistent change with age after burial.     

Studies on the properties of organic matfer in buried humic horizon derived from volcanic ash

To investigate the relationship between the change of humus property and time factor, the humus composition in the buried humic horizons with the age from 28,000 years B.P. to the present was studied, according to the method presented by Kumada et al. (7).

The fH decreased with the elapse of time and in case of most of humus in the buried humic horizons with the age over 10,000 years, the fH became lower than 40 and were in the form of so-called ‘combined’ humus.

When 3,000-4,000 years have passed since the surface soil buried, the humic acid first moved . to ‘combined form.’ Second, after over 10,000 years, the fulvic acid moved to ‘combined form.’

The humification of ‘free’ humic acid proceeded with the elapse of time till around 5,000 years but of 'combined' humic acid till around 7,000 years. Both the humification-degree of ‘free’ humic acid after around 5,000 years and of ‘combined’ humic acid after around 7,000 years decreased. The humification-degree of ‘free’ and ‘combined’ humic acid from the samples with the age about 15,000 years B.P. to 28,000 years B.P. may be the same.     

Changes in soil physical properties of forest floor horizons due to long-term deposition of lignite fly ash

Background, aim, and scope

From the beginning of the twentieth century until the 1990s, energy in Upper Lusatia, Saxony in Eastern Germany was produced at power plants that burnt lignite coals. As a result, alkaline fly ash and aerosols from the combustion of brown coal have accumulated in adjacent areas that are partly under forestry. We ask the question, “how have these atmospheric depositions of fly ash influenced the soil physical properties (bulk density, particle density, saturated hydraulic conductivity, pore size distribution, and water repellency) of forest floor horizons?”

Materials and methods

The experimental sites represented typical soil types and stands of the sylviculturally used areas in the region of Upper Lusatia. Three forest sites were located close to the emission sources, where high amounts of fly ashes accumulated, and three control sites were without fly ash enrichment. Pore size distribution, saturated hydraulic conductivity, and bulk density were examined with undisturbed samples (metal cylinder 100 cm³). Disturbed samples were used for the characterization of particle density, texture, and water repellency (Wilhelmy plate method). Additionally, the carbon content was determined. Scanning electron microscopy was used to show fly ash enrichment.

Results

The enrichment of mineral fly ash particles could be proven for sites close to the emission source. Using scanning electron microscopy, spherical fly ash particles could be identified. Total quantities of persistent fly ash enrichment amounted to approximately 150-280 Mg ha^–1. The enrichment of fly ash affected the soil-physical characteristics. Close to the emission source (sandy fly ashes), particle density, air capacity, and saturated hydraulic conductivity were significantly increased, whereas the plant available water was significantly reduced. With increasing distance from the emission source (silty fly ashes or no ash enrichment), air capacity and saturated hydraulic conductivity were reduced, while an increase of plant available water was observed. Furthermore, the forest floor horizons close to the emission source were characterized by significantly reduced water repellency due to the dominance of hydrophilic mineral fly ash particles.

Discussion

Fly ash deposition in Upper Lusatia must be considered as relevant for properties of forest soils. Mean particle density was significantly higher at sites with fly ash accumulation. This indicates the admixture of mineral particles. While bulk densities were not noticeably influenced, the increase of particle density and the dominance of sandy to coarse silty particles close to the emission sources cause an increase in total porosity, air capacity, and a relative reduction of plant available water. Hollows in spherical fly ash particles might contribute to the meso- and macropores. Due to the admixture of hydrophilic fly ash, the enriched forest floor horizons feature a distinct increase in potential wettability, which coincides with a higher pore and, hence, nutrient and contaminant accessibility. In combination with a higher saturated hydraulic conductivity, an increase in translocation of dissolved substances can be expected especially in the course of acidification, which causes an additional mobilization of nutrients and contaminants.

Conclusions

With this study, we could prove the impact of fly ash enrichment on physical soil properties of forest floor horizons. Via SEM, we detected fly ash particles. The amounts of persistent fly ash accumulation could modify particle density, thickness, bulk density, and carbon content. To characterize hydraulic properties, we investigated the pore size distribution, the saturated hydraulic conductivity, and a water repellency parameter. Thereby, we detected a distinct increase of coarse pores and an accompanying extremely high saturated hydraulic conductivity. The water repellency parameter indicated a significant decrease of hydrophobicity of fly-ash-enriched forest floor horizons.

Recommendations and perspectives

Fly ash enrichment in forest floor horizons not only causes distinct chemical modifications but also alters soil physical properties, which must be considered in further hydrological investigations, as they may influence seepage of water and contaminant translocation within the soil and into groundwater.

     

Expression of andic properties in soils from Galicia (NW Spain) under forest and agricultural use

The organic matter (OM) of soils with andic properties has long been considered highly stable because of the presence of Al–humus complexes and sorption of organic ligands onto amorphous compounds. In this study, we characterized soils under different land use regimes located within an amphibolitic massif close to Santiago de Compostela (Spain), where soils with andic properties are present. Slash and burn agriculture was a common practice in the area until the second half of the 20th century. Thereafter, modern agriculture was progressively introduced into the area (AGR soils), and the rest of the land was either reforested or abandoned (FOR soils). We found that the mean organic C content of AGR soils (48.7 g kg^?1) was ～ 50% that of FOR soils (94.2 g kg^?1). Mean soil pH was significantly greater (P < 0.05) in the AGR than in the FOR soils (4.95 compared with 4.63), which is attributed to liming and Ca‐phosphate fertilization of the former. Mean concentrations of the Al forms studied (extractable with CuCl₂, sodium pyrophosphate, ammonium oxalate, or NaOH) were significantly smaller (P < 0.01) in AGR (1.4, 4.9, 9.3, 11.0 g kg^?1, respectively) than in FOR soils (3.9, 10.2, 16.5, 17.9 g kg^?1, respectively). The results show the vulnerability of the OM and Al–humus complexes in these soils to modern agricultural practices, which has led to the attenuation – and in some cases even the disappearance – of andic soil properties in a relatively short time (< 30 years) following changes in land use/management. We propose the inclusion of the formative element ‘andic’ in the criteria for the definition of Umbrisol subunits; this would avoid the abrupt discontinuity observed in the current World Reference Base classification.     

Some properties of the ash from spruce needles

Abstract

The weight of the ash resulting from dry ashing spruce needles at 500° C can be predicted with good precision from the concentrations of calcium (Ca), potassium (K), magnesium (Mg), manganese (Mn), and silicon (Si) in the needles. The empirical factors associated with the individual elements are given. There is evidence that they can also be applied to leaves from other plants. The colour of the ash can be related to the Mn concentration in the needles. Dry ashing entails no losses for Ca, cobalt (Co), barium (Ba), K, rubidium (Rb), antimony (Sb), scandium (Sc), and zinc (Zn), whereas a very small loss was observed for cesium (Cs), and a very large for bromine (Br).     

Microbial biomass and respiration in soils derived from lignite ashes: a profile study

Microbial biomass C and soil respiration measurements were made in 17–20 yr old soils developed on sluiced and tipped coal‐combustion ashes. Topsoil (0–30 cm) and subsoil (30–100 cm) samples were collected from three soil profiles at two abandoned disposal sites located in the city area of Halle, Saxony‐Anhalt. Selected soil physical (bulk density and texture) and chemical (pH, organic C, total N, CEC, plant available K and P, and total Cd and Cu) properties were measured. pH values were significantly lower while organic C and total N contents and the C : N ratio were significantly higher in the topsoil than in the subsoil indicating the effects of substrate weathering and pedogenic C accumulation. Likewise, microbial biomass C, K₂SO₄‐extractable C, and soil respiration with median values of 786 μg biomass C g^–1, 262 μg K₂SO₄‐C g^–1, and 6.05 μg CO₂‐C g^–1 h^–1, respectively, were significantly higher in the topsoil than in the subsoil. However, no significant difference was observed in metabolic quotient between the topsoil and the subsoil. Metabolic quotient with median values of 5.98 and 8.54 mg CO₂‐C (g biomass C)^–1 h^–1 for the 0–30 cm and 30–100 cm depths, respectively, was higher than the data reported in the literature for arable and forest soils. Microbial biomass C correlated significantly with extractable C but no relationship was observed between it and total N, Cd, and Cu contents, as well as plant‐available K and P. We conclude that the presence of the remarkable concentration of extractable C in the weathered lignite ashes allowed the establishment of microbial populations with high biomass. The high metabolic quotients observed might be attributed to the heavy‐metal contamination and to the microbial communities specific to ash soils.     

Residual effects of poultry litter on silage maize (Zea mays L.) growth and soil properties derived from volcanic ash

Abstract

Poultry litter (PL) is a cheap alternative to conventional fertilizers. The use of PL in this way also reduces the environmental problems normally associated with its disposal. The residual effect of PL may reduce the amount of fertilizer (especially N fertilizer) required by subsequent crops. This study examines the residual effects of PL (with and without additional mineral fertilizer) on the properties of a volcanic ash soil and on silage maize (Zea mays) yields in central Chile. Poultry litter and mineral fertilizer were applied in 2002–2003 and their residual effects were determined in 2004–2006. The dry matter (DM) yield, nutrient balance and apparent nitrogen recovery efficiency (ANRE) of the silage maize were determined for each season, and the soil properties were analyzed at three depths (0–20, 20–40 and 40–60 cm) at the end of the third season. Crop yield showed a positive response to all fertilizer treatments. The residual effect, the nutrient balance, N uptake and ANRE also improved with fertilizer treatment, especially with the PL treatments. The average DM yield for the PL treatments was higher than that observed using mineral fertilizer by 2.8 and 1.2 Mg ha^?1 in the third and fourth years, respectively. The ANRE was generally higher in the PL treatments, although it decreased over time (12.4 and 1.7% for the last 2 years, respectively). The mean ANREs for the mineral fertilizer treatment were 4.1 and 1.6% for the same years. The results suggest that the PL treatments had an important positive residual effect in terms of N supply. This should be taken into account when planning the next crop. After two annual applications of PL, slight increases were observed in soil NO₃-N at a depth of 0–20 cm, and extractable P at depths of 20–40 cm and 40–60 cm. No other soil variables were significantly affected by any of the treatments. An additional source of K was found to be necessary to maintain an adequate soil K level.     

Clay minerals and humus complexes in five Kenyan soils derived from volcanic ash

Clay minerals and humus complexes and their effects on soil chemical properties were studied for five profiles around the Longonot and Susua volcanoes in Kenya. Morphologically, all profiles have some resemblance to Andepts, but there were clear-cut differences in clay contents and mineral composition as well as pH between profiles 1 through 4 and profile 5, which occur under semi-arid to subhumid and under humid climatic conditions, respectively. Profiles 1 through 4 contained embryonic halloysites with X-rays amorphous iron oxide and silica, whereas profile 5 contained a kaolin mineral, chloritized 2:1 layer silicates, gibbsite and hematite. These mineral associations probably represent early and advanced stages of weathering of volcanic ash under weak and strong leaching conditions, respectively. Embryonic halloysites consisted of more or less poorly ordered halloysite and “1.0- and 0.7-1.0-nm minerals”. The carbon contents of A horizons ranged from 100 to 112 g/kg in profiles 2, 3 and 5. Humus complexes increased in the order; Fehumus ⩽ Al-humus ⩽ Ca-humus in profiles 2 and 3, whereas Al- and Fe-humus were found exclusively in profile 5. The pH (NaF), phosphate retention and acid oxalate extractable Al qualify only profile 5 as an Andept or Andisol.     

Origin of cristobalite in soils derived from volcanic ash in temperate and tropical regions

Cristobalite was isolated from four Ando soils and a Podzolic soil developed on volcanic ashes in French West Indies, Indonesia and Japan by selective chemical dissolution with 6 M HCl, 0.5 M NaOH and H₂SiF₆ treatments followed by specific gravity separation. All the cristobalite isolates give X-ray diffractograms with a strong and sharp peak at 4.10–4.11 Å and associated peaks at 2.8 and 2.5 Å, which are characteristic for cristobalite of high-temperature origin. Four out of five isolates show a peak at 4.06–4.07 Å ascribed to low-temperature cristobalite. The oxygen isotopic ratios (δ¹⁸O_SMOW) of cristobalite isolates show a range of +5.3 to +11.0%. which suggests a high-temperature igneous origin. These X-ray diffraction and oxygen isotopic data indicate that the cristobalite was inherited from primary volcanic ash rather than formed during pedogenesis.     

Manufacture and properties of bifidogenic saccharides derived from wood mannan

Pinus pinaster wood samples were subjected to double hydrothermal processing. The liquors coming from the second stage, containing soluble saccharides of polymeric or oligomeric nature from hemicelluloses (POHs), were subjected to membrane processing (operating in discontinuous diafiltration) for refining and fractionation. Refined POH fractions were characterized by matrix-assisted laser desorption/ionization time of flight mass spectrometry and chromatographic techniques. The most complex POH component was made up of 14 hexoses and contained 4 acetyl groups. The fermentability of purified POHs by human fecal inocula was assessed by measuring both carbon source consumption and formation of short-chain fatty acids. The bifidogenic ability of POHs was confirmed by fluorescence in situ hybridization. The stimulatory effects on the bifidobacterial population reached by POHs were of the same order as those obtained with commercial fructooligosaccharides.     

生物质气化站玉米芯飞灰的特性及其综合利用

作为玉米生产加工过程的农业废弃物,玉米芯的产量巨大,生物质气化工业利用玉米芯原料制备生物质燃气的过程中将产生大量的玉米芯灰。为了全面认识这些废弃玉米芯灰的灰特性及可能的应用,通过激光粒度分析、X射线荧光(X-ray fluorescence,XRF)、X射线衍射(X-ray diffraction,XRD)、热重和差热分析(thermal gravimetric and differential thermal analysis,TG-DTA)、扫描电镜(scanning electron microscopy,SEM)、能谱分析(energy dispersive X-ray,EDX)等方法对其进行深入研究。结果表明:玉米芯灰的粒度较小且分布不均,平均粒径为12.96μm;灰的元素组成中K和Si所占的比重最大;富含K、Ca、S和Cl等元素使玉米芯灰可用作土壤改良剂,而且灰中大量的Si O2和Al2O3使其可以用来制备抗压强度较高的水泥混凝土;灰中存在多种含钾元素的KHCO3、KAl Si O4、KAl Si2O6、KCl和K2SO4等结晶相矿物成分;灰粒的形状极不规则,树枝状的团聚灰渣具有丰富的空隙,易逐级吸附小颗粒,灰粒表面存在大量弱粘结的絮状物,断面多为孔状结构;熔融灰粒表面存在富钾现象,且多以KCl形式存在;飞灰的热解具有分段机制,加热到1 200℃时,其总失重和最大失重速率均随着氧气浓度的升高而增加;氮气中620℃的吸热峰是由KCl熔融吸热所致,而有氧气氛中在630℃处的放热峰则是未燃尽的残碳继续燃烧或有机物分解放热所致。     

Phosphorus exchange properties of European soils and sediments derived from them

The sorption and desorption of phosphorus (P) from eroding soil particles in land runoff are important processes contributing to agriculturally‐driven eutrophication. We investigated the P‐exchange properties and related chemical characteristics of contrasting European agricultural soils and sediment material eroded from them under indoor (small‐scale) and outdoor (larger‐scale) rainfall simulations. Quantity‐intensity (Q/I) relationships revealed large variation in equilibrium P concentrations at zero net P sorption (EPC₀) (0–10.3 mg l⁻¹) and instantly labile P (−Q₀, the amount of P to be desorbed to obtain a P equilibrium concentration of 0 mg l⁻¹) (2–75 mg kg⁻¹), both correlating closely with Al‐bound P and the P saturation degree of Al oxides (DPS_Alox). Maximum P sorption (Q_max) (43–515 mg kg⁻¹) also correlated most closely with Al_ox. The indoor and outdoor rainfall simulations produced sediments with different P sorption properties: in the indoor simulation (less kinetic energy, constant slope), the sediments had larger EPC₀ values, and usually larger −Q₀ values, than the sediments in the outdoor simulation (greater kinetic energy, variable slopes). Furthermore, the P exchange properties of the sediments differed from those of the bulk soil depending on the enrichment of soil P‐sorption components (Fe/Al oxides, clay). The outdoor simulation indicated that sites with gentle slopes produced sediments that were more enriched with Al_ox, Fe_ox, Mn_ox and organic C than those with steeper slopes. In this study, when the bulk soil had an initial EPC₀ greater than 1.3 mg l⁻¹, the outdoor rainfall simulation produced sediment with smaller EPC₀ and vice versa, indicating that, depending on the P status of the bulk soil, the sediment material was acting as source or sink for P during transport. However, on the basis of their EPC₀ values, most eroding sediments might be expected to desorb, rather than adsorb, P when entering surface water.