Late Quaternary peat accumulation in southern Africa

It is suggested that the accumulation of peat deposits and other organic sediment may be a clue to the timing of moister periods in the late Quaternary climatic history of southern Africa. Data presented from 26 sites across the sub-continent point to two periods during which organic sedimentation commenced, suggesting a moister late Pleistocene and a period during the mid-late Holocene when conditions also became more conducive to peat formation. Owing to the confusing and conflicting nature of other palaeoenvironmental information, organic sediment accumulation chronologies seem to provide additional insight into the environmental history of southern Africa and the implications of this are discussed.     

木本泥炭对谷子物质生产及产量构成的影响研究

针对新整治旱地土壤养分及有机质含量低、作物产量低等问题,以冀谷38号为供试品种,设置试验处理[FD-A1:木本泥炭+腐熟秸秆+生物激发调节剂I+常规施肥;FD-A2:木本泥炭+腐熟秸秆+生物激发调节剂II+常规施肥;FD-B1:木本泥炭+腐熟秸秆+常规施肥;FD-B2:木本泥炭(减量)+腐熟秸秆+常规施肥]和对照CK(FD-C1:常规施肥)开展大田试验,探究木本泥炭及添加辅料对谷子农艺指标、干物质量积累以及产量的影响。试验结果表明,与常规施肥模式相比,施用木本泥炭能提升谷子农艺指标,木本泥炭减量后还能促进谷子地上生物量及根生物量干物质量积累,木本泥炭添加生物激发调节剂后不仅能提升谷子农艺指标,促进干物质量积累,还能提高谷子产量,添加生物激发调节剂II和生物激发调节剂I较常规施肥模式分别增产15.72%和14.18%,其中木本泥炭+生物激发调节剂II+腐熟秸秆+常规施肥模式为最佳处理模式。     

The occurrence of aphid wax in peat

Small white aggregates frequently observed in peat have been studied using scanning electron microscopy and infrared absorption spectrometry. It has been shown that they are fibrous, consisting of paraffin wax and associated carbohydrate and secondary amide, and are secreted by the aphid Colopha compressa, which colonizes the roots of Eriophorum spp. growing on peat. This is the first report of the occurrence of this aphid species in Scotland.     

Controls on carbon accumulation and storage in the mineral subsoil beneath peat in Lakkasuo mire, central Finland

What processes control the accumulation and storage of carbon (C) in the mineral subsoil beneath peat? To find out we investigated four podzolic mineral subsoil profiles from forest and beneath peat in Lakkasuo mire in central boreal Finland. The amount of C in the mineral subsoil ranged from 3.9 to 8.1 kg m^?2 over a thickness of 70 cm and that in the organic horizons ranged from 1.8 to 144 kg m^?2. Rates of increase of subsoil C were initially large (14 g m^?2 year^?1) as the upland forest soil was paludified, but decreased to < 2 g m^?2 year^?1 from 150 to 3000 years. The subsoils retained extractable aluminium (Al) but lost iron (Fe) as the surrounding forest podzols were paludified beneath the peat. A stepwise, ordinary least‐squares regression indicated a strong relation (R² = 0.91) between organic C concentration of 26 podzolic subsoil samples and dithionite–citrate–bicarbonate‐extractable Fe (negative), ammonium oxalate‐extractable Al (positive) and null‐point concentration of dissolved organic C (DOC_np) (positive). We examined the ability of the subsoil samples to sorb dissolved organic C from a solution derived from peat. Null‐point concentration of dissolved C (DOC_np) ranged from 35 to 83 mg l^?1, and generally decreased from the upper to the lower parts of the profiles (average E, B and C horizon DOC_np concentrations of 64, 47 and 42 mg l^?1). The DOC_np was positively correlated with percentage of soil C and silt and clay content. The concentration of dissolved organic C in pore water in the peat ranged from 12 to 60 mg l^?1 (average 33 mg l^?1), suggesting that the sorptive capacity of the subsoil horizons for C had been exhausted. We suggest that the increase of C contents in the subsoil beneath mires is related to adsorption of dissolved organic C and slow mineralization under anaerobic conditions.     

The nitrogen content of particle size fractions separated from peat and its rate of mineralization during incubation

Particle size fractions, varying from 5 to 0.005 mm, were separated from samples of several peat types using a wet sieving technique. In all types, nitrogen content of fractions increased as particle size decreased, the fine fractions (0.15–0.005 mm) accounting for around 43–64% of the total nitrogen. During incubation, fractions from two blanket peats showed a net release of mineral nitrogen, whereas those from raised bog peats were characterized, for the most part, by net immobilization. Amounts of mineral nitrogen released in fractions from any one peat after 28 days incubation at 30°C did not always correlate with either total nitrogen content or C:N ratio. However, better correlations between mineral nitrogen production and total N were obtained for fractions of similar particle size. The proportion of the total nitrogen that was mineralized tended to be higher in coarse fractions > 0.15 mm, blanket peats giving much higher values than samples from raised bogs. Carbon dioxide release also varied with particle size, being highest in large particles and fibres and least in the size range 0.15–0.5 mm. Smaller particles < 0.15 mm, gave intermediate values that were higher in blanket than in raised bog peat.     

The redox characteristics of four peat profiles

In several previous observations on peat soils, redox potentials appeared to vary with season and depth. To clarify this variation, a systematic study was made over 1 yr at four peat sites, including wet and dry areas at high and low altitude in northern England.The coefficients of linear regressions of redox potential on seasonal temperatures became progressively more negative with increasing depth at all four sites. These observations support an hypothesis that increased aeration accompanying increased temperature played a role at the surface, but was of less importance in the deeper layers, where the reducing conditions that result from microbial activity were dominant.By using orthogonal polynomials, it was possible to demonstrate the existence of redox minima in the profiles at all sites. There were rather more minima present using this method at the lowland sites that at the upland ones where trends of redox with depth were otherwise linear or non-significant. Although the mean redox potentials over whole profiles were lower in the wetter sites than the drier, the mean depths of the redox minima were similar. These mean depths were poorly defined however having standard deviations of 30–50 per cent of the means calculated from the year's observations.Finally, it was shown that although the potentials were measured 60 s after closing the circuit, very similar conclusions would have been reached if the readings had been taken after 10 s.     

Radiogeochemistry of Kamchatka soils

Background concentrations of Th and U in volcanic soils (Andosols) of Kamchatka are much lower than their clarkes in continental soils. The dose rate of gamma radiation above the soil surface (10–11.5 µR/h in the south and 8–9.5 [m]R/h in the north of Kamchatka Peninsula) is lower than the natural level of this index for the mountainous areas in the boreal zone of Russia. The natural radiogeochemical background of Kamchatka soils is controlled by the petrochemical composition of volcanic ash composing the mineral basis of Kamchatka soils. It is higher in the southern soil province, where soils develop from acidic ashes, in comparison with the northern province, with a predominance of soils developing from ashes of basic and intermediate composition. This agrees with Th and U clarkes for the corresponding types of volcanic rocks and explains the natural origin of the elevated radiogeochemical background in the southern part of Kamchatka as compared with its northern part. The soils of the northern province developing from relatively fresh volcanic ashes show a lower Th/U ratio as compared to the soils of southern Kamchatka because of higher uranium content in the newly deposited ashes.     

The development of chernozems on the Dniester-Prut interfluve in the Holocene

The development of forest-steppe and steppe chernozems on the Dniester-Prut interfluve in the Holocene was studied on the basis of data on the paleosols buried under archaeological monuments of different ages. The parameters of the mathematic models of the development of the soil humus horizons in different subtypes of chernozems were calculated. They were used to determine the rate of this process and the age of the soils formed on the surface of Trajan’s lower rampart. The climate-controlled changes in the character of the soil’s development in the Late Holocene were differently pronounced in the different subtypes of chernozems. The suggested differentiation of the trends in the development of the humus horizon in the studied chernozems corresponds to the differences in the soil-forming potential of particular areas (as judged from the energy consumption for pedogenesis).     

Phenolic esters in peat

The p-hydroxypropiophenone ester of stearic acid has been isolated sedge peat. This appears to be the first report of the ester as a natural product.     

The effect of pH on sulfate availability in sphagnum peat

Abstract

The influence of pH upon the availability of sulfate‐sulfur in sphagnum peat moss was studied. Samples of sphagnum peat moss amended with 0, 1.41, 2.82, 3.81 and 5.64 g/L Ca(OH)₂, had pH values of 2.8, 3.7, 4.7, 5.8 and 7.0, respectively. Sulfate was extracted from peat samples with a 0.15% CaCl₂.H₂O or a 500 mg P/L (as Ca(H₂PO₄)₂.H₂O) extractant and quantified with a Dionex QIC ion Chromatograph. Sulfate availability from the CaCl₂‐extracted solutions was greatest at pH 4.7 and 5.8, but highest at pH 4.7 only for the P‐extracted solutions, in which no measurable extracted sulfur was found at pH levels greater than 4.7.     

Available potassium in volcanic soils of Kamchatka

The distribution of available potassium in the profiles of synlithogenic volcanic soils of Kamchatka has been studied. Most of the soils in the Central Kamchatka Depression and the Western Kamchatka Lowland are characterized by a medium content of nonexchangeable potassium and a high content of exchangeable potassium. The soils of the east coast are less rich in potassium. The reserves of available potassium in the root layer of the virgin and cultivated soils of Kamchatka have been calculated. It is shown that differences in the reserves of potassium are related to different degrees of the soil tolerance toward the depletion of potassium and to the uneven application of potassium fertilizers. In most cases, soil cultivation is accompanied by a general rise in the reserves of available potassium with an increase in the portion of exchangeable potassium relative to its nonexchangeable forms.     

The role of mineralization of the organic matter of soddy-podzolic and peat bog soils in the accumulation of <Superscript>137</Superscript>Cs by plants

The role of mineralization of soil organic matter (SOM) in the mobilization of ¹³⁷Cs was estimated on the basis of data on the biokinetic fractionation of the organic matter of soddy-podzolic sandy-loam and peat bog soils and on the coefficients of the soil-to-plant transfer of radiocesium under field conditions. The peat bog soils were richer than the soddy-podzolic soils in the total organic carbon (by 7.9–23.8 times), the potentially mineralizable carbon (by 2.4–6.5 times), and the carbon of the microbial biomass (by 2.9–4.6 times). The agricultural use of the soddy-podzolic and peat bog soils led to a decrease in the SOM mineralization capacity by 1.1–1.8 and 1.4–2.0 times, respectively. Simultaneously, the portions of the easily, moderately, and difficultly mineralizable fraction of the SOM active pool changed. The coefficients of the ¹³⁷Cs transfer from the peat bog soils to plants were 3.3–17.6 times higher than those for the soddy-podzolic soils. The content of ¹³⁷Cs in plants grown on the peat bog soils was 2–65 times higher than that in the mobile (salt-extractable) soil pool by the beginning of the growing season. Strong positive linear correlations were found between the coefficients of the soil-to-plant transfer of ¹³⁷Cs and the total content of the SOM, the content of the microbial biomass, the content of the potentially mineralizable carbon, and the intensity of its mineralization. It was concluded that the decisive factors controlling the intensity of the ¹³⁷Cs transfer from mineral and organic soils into plants are the SOM content and its mineralization potential. The mineralization of the SOM is accompanied by the release of both ¹³⁷Cs and mineral nitrogen; the latter facilitates the transfer of radiocesium into plants.     

The soil cover of Central Kamchatka (GIS model)

The spatial distribution of major soil horizons and layers of pyroclastic deposits in Kamchatka was analyzed with the use of GIS technologies. For this purpose, the attribute soil database and the computer-supported cartographic database were developed. Their analysis with the help of GIS technologies made it possible to study the dependence of the morphology of soil profiles on the bioclimatic conditions and on the stratification of ash layers in the particular areas of Kamchatka and to develop the cartographic model of the areas of soil horizons. The concept of tephra stratotypes—the particular combinations of ash layers in the profiles of volcanic soils—was verified on the basis of factual materials. It was shown that tephra stratotypes affect many important soil properties and specify the direction of soil formation in Kamchatka. Several major tephra stratotypes differing in their morphology and environmentally important features were distinguished in Central Kamchatka. The method of soil mapping on the basis of the concept of tephra stratotypes with due account for the specificity of surface organic horizons of soils was developed. It is argued that this method makes it possible to reflect the specificity of soil formation in volcanic regions.     

Use of peat in the treatment of oily waters

Peat is an effective medium in the treatment of oil-in-water emulsions due to its known capacity to absorb oil and its abundant availability. Horticultural Sphagnum peat was used in the present study to assess its potential for removal of oil from oily wastewaters. Oily wastewater samples included a low viscosity (50 cP) crude oil Midale, a medium viscosity (130 cP) standard mineral oil, a refinery effluent and a cutting oil emulsion. It was found that the oil binding capacity of the peat was 7.5 to 7.8 times its air dry weight. The percentage removal of oil from oil-in-water emulsions ranged from 21 to 98% depending upon the type of emulsion studied. Batch kinetic studies showed that equilibrium was reached in 1 to 3 hr for the emulsions investigated. Isotherm analysis of the data showed that BET isotherm fits generally the adsorption pattern. By applying the BET isotherm to the particular oil-in-water emulsion, it is possible to calculate the amount of peat required to reduce the oil in the oily water to a desired concentration; a batch adsorption system can be designed to operate on a fill-and-draw basis.     

The fine scale variability of dissolved methane in surface peat cores

Peat forming wetlands are globally important sources of the greenhouse gas CH₄. The variability of flux recordings from peatlands is however considerable and the distribution of CH₄ below the water table poorly described. Surface peat (0-500 mm below the water table) is responsible for the bulk of emissions and a localised region of intense CH₄ concentration may exist within this region but the structure of peat and presence of gas bubbles make the determination of in situ gas distributions problematic. We report on the in situ distribution and concentrations of CH₄, CO₂ and O₂ in surface bog peat cores using Quadrupole Mass Spectrometry and relate this to peat physical structure. Replicate cores collected in spring and autumn from both hollows and hummocks are used (n = 10). CH₄ recorded in almost every profile was localised in intense peaks reaching concentrations up to 350 μM at depths where O₂ was absent. Each CH₄ peak had a coincident CO₂ peak with a minimum mean ratio of ∼20:1 (CO₂:CH₄) and we found more CH₄ beneath hollows than hummocks. In statistical comparisons CH₄ concentration and distribution differed significantly between profiles for each depth. We demonstrate that variability found within a single core is at least as great as that between cores collected across the bog. The distribution of CH₄ was negatively correlated with bulk density and in some cases the location of roots matched those of intense CH₄ concentration where bubbles had formed and been trapped. Our comparisons suggest variability in gas distribution is caused by a heterogenous peat structure that controls the movement of gas bubbles and contains localised hotspots of gas production. The small and fine root systems of vascular plants on the peatland surface may cause high levels of methanogenic activity in their vicinity and also represent a physical barrier capable of trapping CH₄ bubbles.     

The regularities of the late Holocene soil formation in the lower don steppes

The direction and stages of pedogenesis, rate and scales of changeability, and type of evolution of chernozems in the steppes of the Lower Don are ascertained by studying the archaeological monuments of the Bronze Age, Early Iron Age, and Middle Ages. It is shown that the soil formation process was characterized by cyclicity, and evolutional soil transformations took place at the level of subtype. The paper ascertains the polygenetic character of modern chernozems, whose evolution during the second half of the Holocene was predominantly low-contrast, inheriting, and transforming. The processes forming the humus, salt, gypsum, and carbonate profiles, as well as the processes of solonetzization-desolonetzization, were the most dynamic. The fundamental differences in the genesis of different parts of the humus profile are revealed. The role of climatically pulsing solonetzicity in forming the specific Azov chernozems is for the first time ascertained.     

Estimating the carbon stock of a blanket peat region using a peat depth inference model

At the global scale peatlands are an important soil organic carbon (SOC) pool. They sequester, store and emit carbon dioxide and methane and have a large carbon content per unit area. In Ireland, peatlands cover between 17% and 20% of the land area and contain a significant, but poorly quantified amount of SOC. Peatlands may function as a persistent sink for atmospheric CO₂. In Ireland the detailed information that is required to calculate the peatland SOC pool, such as peat depth, area and carbon density, is inconsistent in quality and coverage. The objective of this research was to develop an improved method for estimating the depth of blanket peat from elevation, slope and disturbance data to allow more accurate estimations of the SOC pool for blanket peatlands. The model was formulated to predict peat depth at a resolution of 100 ha (1 km²). The model correctly captured the trend and accounted for 58 to 63% of the observed variation in peat depth in the Wicklow Mountains on the east coast of Ireland. Given that the surface of a blanket peatland masks unknown undulations at the mineral/peat interface this was a successful outcome. Using the peat depth model, it was estimated that blanket peatland in the Wicklow Mountains contained 2.30 Mt of carbon. This compares to the previously published values ranging from 0.45 Mt C to 2.18 Mt C.     

Sulfur mineralization in sphagnum peat

Abstract

Open and closed incubation systems were studied as means of quantifying sulfate fractions in sphagnum peat moss. Sulfate was extracted in the closed system with a 0.15% CaCl₂‐H₂O or a 500 mg P/L extractant. Sulfate was extracted in the open system with 10 mM KC1, 0.15% , CaCl₂‐H₂O, or 500 mg P/L extractant. Extractants were quantified by ion chromatography. Phosphate extractant released more sulfate than CaCl₂, in the closed system. There was a significant increase over time of sulfate released by the CaCl₂ extractant. In the open system, there was no significant difference in release and total amounts leached of sulfate‐S between extractants. The closed system released more sulfate‐S than the open system. Phosphate extractants in both systems mineralized 43% of initial sulfur content     

The severity of smouldering peat fires and damage to the forest soil

Smouldering wildfires propagate slowly through surface and subsurface organic layers of the forest ground and severely affect the soil, producing physical, chemical and biological changes. These effects are caused by the prolonged heating and the large loss of soil mass but are poorly documented in the literature. A series of smouldering experiments with boreal peat have been conducted under laboratory conditions to quantify these effects using small-scale samples. Peat samples of 100 mm by 100 mm in cross section and 50 mm in depth of different moisture were exposed to an external ignition source. Thermocouples placed throughout the sample bed measured the temperature evolution and tracked the peat ignition, intensity and spread of the smouldering front. The results show that moisture content controls peat ignition and that moisture below 125 ± 10% (in dry base) are required. The severity of the smouldering peat on the soil has been quantified in terms of temperature vs. residence time curves and mass loss. The measurements show temperatures in excess of 300 °C for residence times of 1 h leading to sterilization of the soil and mass loss in burnt layers above 90%.