汞在泥炭上的吸附特征研究

采用批次法研究了汞在三江平原泥炭、吉林双阳泥炭上等温吸附特征及介质pH值、背景离子浓度的影响。实验结果表明:两种泥炭吸附等温线均同时符合Langmuir和Freundlich等温吸附方程,而与Langmuir方程的拟合效果更好; 在溶液汞浓度相同时,温度升高,泥炭对汞的吸附量降低;在相同的条件下,三江平原泥炭对汞的吸附量大于吉林双阳泥炭对汞的吸附量;两种泥炭对汞的吸附量受pH值的影响明显且都在pH 6.0左右具有最大的吸附量;在酸性条件下,吸附介质的pH值升高利于泥炭对汞的吸附;介质的离子浓度升高,可以使两种泥炭对汞的吸附量迅速降低。     

In Situ Pore Pressure Responses of Native Peat and Soil under Train Load: A Case Study

Settlement and formation of piping holes on surfaces were observed along a rail embankment subject to normal traffic load. Piezometers were installed in the native peat and soil underneath the embankment inside and outside problematic area to measure the pore pressure responses during train traffic. Peculiar pore pressure responses were observed. Cyclic pore pressures were only measured during the first 60–80?s of the 6-min train passage, and thereafter the pressures decayed rapidly to the initial values. The pore pressure changes in the shallow peat layer were lower than those in the deep soil layer. Possible mechanisms causing such peculiar pore pressure responses, surface settlement, and piping holes were explored and identified. It was found that the stiffness contrast between the stiff, upper granular fill and the soft, native peat material could lead to a redistribution of tensile stress in the granular fill layer to the peat layer due to the moving train load. This stress redistribution promotes the propensity of vertical piping in the peat layer.     

Reconsideration of the settlement behavior of peat from view point of hydraulic conductivity

This paper deals with the settlement of peat from the view point of hydraulic conductivity (k). The validity of using the oedometer tests, including the calculation method, for measuring k is carefully examined by numerical analysis as well as a test combined with an oedometer and a hydraulic conductivity test. It is found from these studies that the conventional oedometer test (JIS A 1217, 2009) can be evaluated to measure k for peat with the same accuracy as that for usual clays, provided that the incremental load ratio is unity. The significant difference in the characteristics of k for peat and usual clayey soils is their relation between the compression index (C_c) and the hydraulic conductivity change index (C_k). As a result, rather than remaining constant during consolidation, the coefficient of consolidation (c_v) of peat decreases considerably with increasing consolidation pressure (p), while the c_v coefficient for usual clayey soil is almost constant at the normally consolidated stage. The influence of c_v dependent on p is studied by a numerical analysis for the one dimensional consolidation problem as well as for the ground improved by vertical drain. It is found that if the incremental consolidation pressure (Δp/p) is large, careful judgment is required when adopting conventional consolidation analyses, especially in case of the vertical drain.     

Impact of Temperature and Loading on the Mitigation of AMD in Peat Biofilter Columns

The mitigation of AMD at Canadian mine sites using passive treatment technologies requires a combined strategy that minimizes the effect of climatic variability on the treatment performance of the system. A vertical-flow combined passive treatment system was developed consisting of an oxidation/precipitation basin for excess iron removal; an unsaturated flow peat biofilter for heavy metal sorption and the reduction of oxygen concentrations; a sulfate reducing bacteria bioreactor for alkalinity generation and sulfate reduction; and, an anoxic limestone drain for alkalinity addition. Laboratory investigations were undertaken to characterize AMD mitigation through the peat biofilter under unsaturated flow conditions and to assess its performance in the combined passive system. Peat column sorption studies were conducted at 20 and 0°C to assess the effect of temperature on metal retention. At 0°C, a metal removal efficiency of Cd < Mn < Zn < Al < Ni < Cu < Fe was noted. At 20°C, however, sulfate-reducing conditions developed in the column as a result of the flow regime, which facilitated the establishment of anaerobic zones within the peat column, leading to a significant increase in effluent pH and metal removal. Sequential extraction indicated that Fe, Cu, and Al were typically bound to the organic matter fraction, while Mn, Zn, Ni, and Cd were primarily associated with the exchangeable fraction.     

泥炭资源的综合利用

综述了国内外在泥炭研究方面取得的成果,重点阐述了泥炭在饲料添加剂、泥炭营养土、去除废水中的重金属离子、净化工业和城市污水、吸附水中石油等环保方面以及能源、工业和医疗美容等方面的研究现状。同时对泥炭的应用前景做出了展望。     

煤系有机质生成烃类中甾烷系列化合物地球化学特征——以高温封闭体系下热模拟实验为例

选择泥炭和褐煤进行热模拟试验并开展对比研究,目的是全面获得煤系有机质生烃特征。通过对草本泥炭和褐煤的热模拟实验液态产物饱和烃进行色谱—质谱分析得到,在泥炭和褐煤热模拟样品中均检测出丰富的甾族系列化合物,且以C29甾烷占优势。研究发现,随热模拟温度增高,C29甾烷相对含量减少,温度在350℃之后趋于稳定;而C27甾烷和C28甾烷相对含量具有增加的趋势,暗示了C29甾烷的去甲基效应。C2920S/（20S＋20R）值和C29ββ/（ββ＋αα）值可以判识样品是否成熟或未熟,是良好的成熟度指标。∑重排甾烷/∑规则甾烷值可以区分成样品成熟度。研究发现,在低演化阶段,泥炭和褐煤模拟曲线存在显著差异,而在高演化阶段,二者吻合较好。所以,对比研究泥炭和褐煤的地球化学特征,对认识煤系有机质生烃特征具有重要意义。     

A comparison of low-cost biosorbents and commercial sorbents for the removal of copper from aqueous media

Three biosorbents, crab carapace, the macroalgae Fucus vesiculosus and peat were compared with two commercial materials, an activated-carbon and an ion-exchange resin for the removal of copper from aqueous media. Kinetic models of Lagergren first-order, pseudo-second order and intraparticular diffusion were used to model the data. The process for all materials is best represented by the pseudo-second order rate model. Langmuir and Freundlich isotherms were used to describe the sorption equilibrium data. Maximum uptake values were 79.4, 114.9 and 71.4 mg g(-1) for crab carapace, F. vesiculosus and ion-exchange resin, respectively. Langmuir and Freundlich isotherm models could not be fitted to the experimental data for peat and activated-carbon. Ion-exchange was calculated to contribute approximately 75%, 77% and 44% to the total biosorption by crab carapace, F. vesiculosus and peat, respectively. The removal efficiencies of crab carapace and F. vesiculosus were >95% and comparable with those achieved using ion-exchange resin. Results from this study suggest that both crab carapace and F. vesiculosus are efficient and effective biosorbent materials for the removal of copper from aqueous solutions and given that they are also low-cost, may be considered viable alternatives to activated-carbon and ion-exchange resin.     

Historical accumulation rates of mercury in four Scottish ombrotrophic peat bogs over the past 2000 years

The historical accumulation rates of mercury resulting from atmospheric deposition to four Scottish ombrotrophic peat bogs, Turclossie Moss (northeast Scotland), Flanders Moss (west-central), Red Moss of Balerno (east-central) and Carsegowan Moss (southwest), were determined via analysis of ²¹⁰Pb- and ¹⁴C-dated cores up to 2000 years old. Average pre-industrial rates of mercury accumulation of 4.5 and 3.7 μg m^− 2 y^− 1 were obtained for Flanders Moss (A.D. 1-1800) and Red Moss of Balerno (A.D. 800-1800), respectively. Thereafter, mercury accumulation rates increased to typical maximum values of 51, 61, 77 and 85 μg m^− 2 y^− 1, recorded at different times possibly reflecting local/regional influences during the first 70 years of the 20th century, at the four sites (TM, FM, RM, CM), before declining to a mean value of 27 ± 15 μg m^− 2 y^− 1 during the late 1990s/early 2000s. Comparison of such trends for mercury with those for lead and arsenic in the cores and also with direct data for the declining UK emissions of these three elements since 1970 suggested that a substantial proportion of the mercury deposited at these sites over the past few decades originated from outwith the UK, with contributions to wet and dry deposition arising from long-range transport of mercury released by sources such as combustion of coal. Confidence in the chronological reliability of these core-derived trends in absolute and relative accumulation of mercury, at least since the 19th century, was provided by the excellent agreement between the corresponding detailed and characteristic temporal trends in the ²⁰⁶Pb/²⁰⁷Pb isotopic ratio of lead in the ²¹⁰Pb-dated Turclossie Moss core and those in archival Scottish Sphagnum moss samples of known date of collection. The possibility of some longer-term loss of volatile mercury released from diagenetically altered older peat cannot, however, be excluded by the findings of this study.     

Combustion possibility of low rank Russian peat as a blended fuel of pulverized coal fired power plant

Combustion possibility of Russian peat as a blended fuel of commercial thermal power plant was investigated by thermogravimetric analysis (TGA), drop tube furnace (DTF) and ignition temperature (IT) tester. TGA results showed that the linear regression for the Arrhenius plot to the experimental data is very good, and activation energies for overall combustion of bituminous C & A (Coal & Allied, Australia coal name) and peat are 66.83 and 25.05 kJ/mol, respectively. It was derived that activation energies of 30%, and 50% blends produced through mixing of peat of 30%, and 50% to Design C & A (design criteria coal of 500 M coal fired power plant) are 27.76 and 24.22 kJ/mol in reciprocal proportion to blending ratio. The conversion behavior of the samples observed in DTF was similar to that reflected in TGA. DTF studies showed that the combustion of all blends was also completed at residence time of around 1 s, set temperature range of 1200 °C similar to commercial coal fired plant. Although the peat has the highest conversion than the blends, it was not appropriate as the single pulverized fuel of coal fired plant because its initial deformation (IDT) and ignition temperatures of about 1160 and 240 °C, respectively, were too low to cause the slagging in boiler, and the firing at pulverizer. The IDT and FT of the blends ashes of peat of less than 30% was about 1260 and 1410 °C, respectively, and was not expected to be associated with slagging and fouling in pulverized coal fired systems. The liability of spontaneous combustion of coal samples was increased with increasing the moisture and volatile contents whereas the same of peat was the lowest due to the high volatile content and specific heat (Cp). It was therefore proposed that the combustion of blends of peat with less than 30% was the most appropriate for the prevention of slagging and spontaneous combustion at the pulverized coal fired boilers, and has the excellent combustion efficiency.     

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