Sorption Behavior of Arsenate by Mg-Bearing Minerals at Hyperalkaline Condition: Implications for Oxyanions Sequestration During the Use and Disposal of Alkaline Wastes

The utilization and disposal of alkaline waste materials such as slag and coal fly ash as cement aggregates and raw materials in cement manufacturing can pose environmental and health hazards because these waste materials usually contain elevated concentration of toxic elements. This study examined the possibility of controlling the pore water chemistry of these waste materials in order to induce the secondary mineral formation of Mg-bearing minerals as major sorbing solids for oxyanions during the utilization and disposal of alkaline wastes. The formation of Mg-bearing minerals was examined at ambient temperature and alkaline pH conditions in the Mg?CSi?CAl system. The interaction of Mg-bearing minerals with oxyanions using arsenate as an analog was examined during and after mineral formation. The results revealed that the generated Mg-bearing mineral phases were smectite and brucite in Mg?CSi system and hydrotalcite and serpentine in Mg?CSi?CAl system. Moreover, hydrotalcite, serpentine, brucite, and smectite phases formed under low Si ratio showed high sorption capacity for arsenate, but only high Al content hydrotalcite and serpentine showed substantial irreversible fraction of sorbed arsenate. Hence, the generation of these kinds of hydrotalcite and serpentine phases as scavengers for oxyanions must be considered during the utilization and disposal of alkaline wastes.     

Comparing chemical-enhanced washing and waste-based stabilisation approach for soil remediation

Purpose

This study aimed to compare the effectiveness of chemical-enhanced soil washing (with chelating agents, humic substances and inorganic acids) and soil stabilisation by inorganic industrial by-products (coal fly ash, acid mine drainage sludge and zero-valent iron) and organic resource (lignite) for timber treatment site remediation.

Materials and methods

Both remediation options were assessed in terms of extraction/leaching kinetics and residual leachability (toxicity characteristic leaching procedure, TCLP) of the major risk drivers, i.e. Cu and As.

Results and discussion

In chemical-enhanced soil washing, chelating agents only minimised the Cu leachability. Humic substances were ineffective while inorganic acids reduced the As leachability to the detriment of the soil quality. For the waste-stabilised soil, the short-term leaching potential (72 h) and long-term TCLP leachability (9 months) revealed that Fe-/Al-/Ca-rich AMD sludge and coal fly ash sequestered As through adsorption and (co-)precipitation, while carbonaceous lignite stabilised Cu with oxygen-containing functional groups. The short-term and long-term leaching of Cu and As into the soil solution was negligible in the presence of the waste materials. However, the waste-stabilised soil did not maintain sufficient Cu stability in the TCLP tests, in which acetate buffer induced significant mineral dissolution of the waste materials.

Conclusions

These results suggest that chelant-enhanced washing (significant reduction of Cu leachability) may be augmented with subsequent stabilisation with inorganic waste materials (effective control of As leachability), thus minimising the environmental risks of both Cu (heavy metal) and As (metalloid) while preserving the reuse value of the soil. Additional tests under field-relevant conditions are required to provide a holistic performance evaluation.     

Analysis of Coal Ash for Trace Elements and their Geo-environmental Implications

This study determined the content of trace elements in coal ash collected from a coal-fired thermal power plant using local coal from Sawarak, Malaysia. This is crucial for the potential impact on the geoenvironment from its disposal and utilization; as coal ash has recently been produced locally in substantial amounts and very limited data is available. The trace elements concentrations presents in coal ashes are compared with the reported coal ash concentrations and the risk for the local wet tropical geoenvironment from the perspective of its vulnerability to these is studied for an indication of potential environmental implications on the wet tropics. The trace elements were found to be in concentrations that, if applied or inadvertently released into the environmental media, present a potential hazard and further necessary research in this regard is indicated.     

云贵高原农村地区生活垃圾特性与管理分析

鉴于当前农村生活垃圾的污染日益突出,且云贵高原农村地区生活垃圾的研究尚处于空白,随机选择了该地区9个自然村,通过访问式问卷调查、现场采样、实验室测试等方法,对当地农村生活垃圾的特性、群众对生活垃圾的认知以及参与管理的意愿进行了调研,以期为农村生活垃圾的管理与处理处置提供理论支撑和技术指导。研究表明：云贵高原农村地区生活垃圾产生量为160g·人-1·d-1;主要组分有厨余类、灰土类、橡胶类、纸类和木竹类;垃圾容重、含水率、灰分、可燃物和热值分别为106kg·m-3、39．16％、19．48％、41．37％和7615kJ·kg-1。此外,云贵高原农村地区群众对生活垃圾的污染性认知主要来自于直观感受,对可回收生活垃圾的认知直接受当地废品回收商的影响,对有毒有害生活垃圾的认知不足;群众对生活垃圾处理处置的支付意愿较好,参与生活垃圾保洁和管理工作的意愿较强,该地区已基本具备开展农村生活垃圾管理与处理的群众基础。     

Technogenic Magnetic Particles in Alkaline Dusts from Power and Cement Plants

During this study, we investigated the mineralogical characterization of technogenic magnetic particles (TMPs) contained in alkaline industrial dust and fly ash emitted by coal burning power plants and cement plants. The reaction of tested dust samples varied between values of pH 8 and pH 12. Their magnetic properties were characterized by measurement of magnetic susceptibility (χ), frequency dependence of magnetic susceptibility (χ_fd), and temperature dependence of magnetic susceptibility. Mineralogical and geochemical analyses included scanning electron microscopy with energy dispersive spectroscopy, microprobe analysis and X-ray diffraction. The TMPs in fly ash from hard coal combustion have the form of typical magnetic spherules with a smooth or corrugated surface as well as a skeletal morphology, composed of iron oxides (magnetite, maghemite, and magnesioferrite) that occurred in the form of incrustation on the surface of mullite, amorphous silica, or aluminosilicate particles. The TMPs observed in fly ash from lignite combustion have a similar morphological form but a different mineralogical composition. Instead of magnetite and magnesioferrite, maghemite and hematite with lower χ values were the prevailing magnetic minerals, which explains the much lower magnetic susceptibility of this kind of ash in comparison with the ash from hard coal combustion, and probably results from the lower temperature of lignite combustion. Morphology and mineralogical composition of TMPs in cement dust is more diverse. The magnetic fraction of cement dust occurs mostly in the form of angular and octahedral grains of a significantly finer granulation (<20 μm); however, spherules are also present. A very characteristic magnetic form for cement dust is calcium ferrite (CaFe₃O₅). The greatest impact on the magnetic susceptibility of cement dust results from iron-bearing additives (often waste materials from other branches of industry), which should be considered the most dangerous to the environment. Stoichiometric analysis of micro-particles confirmed the presence of heavy metals such as Pb, Mn, Cd, and Zn connected with TMPs, which are carriers of magnetic signals in atmospheric dust. Therefore, in some cases, their presence in topsoil when detected by magnetic measurement can be treated as an indicator of inorganic soil contamination.     

Mineralization and volatile loss of nitrogen from soils treated with coal combustion byproducts

There is an increasing need to find a suitable means for disposal of coal combustion byproducts because of the increasing world-wide production of these byproducts. This need has prompted interest in the use of land disposal, but there are concerns that this use may degrade the quality of soil. To determine the influence of coal combustion byproducts on the transformation and fate of soil N and assess the potential impact of land disposal on soil quality, we studied the effects of two combustion byproducts (fly ash and bed ash) applied at rates of 22.5, 45, 90, and 180 Mg ha^-1 on mineralization and volatile loss of N from soil. Studies comparing the influence of the byproducts on these processes showed that whereas fly ash had little influence on the fate of soil N, bed ash caused substantial mineralization of organic soil N and volatile loss of this N as NH₃. Studies monitoring the pH of soils treated with bed ash showed that soil pH increased immediately after this treatment, with values reaching as high as 12.8. These studies indicated that such extreme alkaline conditions caused chemical degradation and volatile loss of as much as 10% of the organic N in soil, and they provide strong evidence that the improper disposal of bed ash on land can have a substantial negative impact on soil quality.     

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.     

不同来源腐殖酸的组成和性质的研究

本研究从三种有机物料草炭、褐煤、风化煤中提取腐殖酸,对其组成和性质进行了测定,同时对胡敏酸进行酒精沉淀分级。研究结果表明:褐煤胡敏酸氧化度和芳香度最高,其次为风化煤胡敏酸,最后是草炭胡敏酸;风化煤富里酸的氧化度和芳香度最高,其次为褐煤富里酸和草炭富里酸。胡敏酸各级分的回收率均随着级分数的升高而增加。回收率以风化煤胡敏酸最高,依次为褐煤胡敏酸、草炭胡敏酸。     

Solid Wastes In Urban And Rural Areas Of Ibadan,Nigeria: Composition,Treatment And Public Health Concerns

The composition of solid waste produced at various locations in Nigeria differs considerably because the amounts generated and the constituents thereof are determined by social customs and living standards. Nigeria has undergone extensive industrial development which has often changed the composition of domestic solid waste as well as agricultural wastes. The disposal and utilization of these mixed wastes has presented new risks and problems for our society and environment. Though most solid waste in Nigeria contains little human and animal material, pathogenic organisms affecting both continue to be present. Potential risks to human health and the environment that can arise from domestic solid waste disposal and utilization in Nigeria include pollution of water and air, accidents, contact contamination and breeding sites for flies and rodents. There also are long-term problems in relation to the human food chain.     

固体废弃物修复荒漠化土壤的研究——以包头地区为例

本文在内蒙古包头市北梁区荒漠化土壤的质地和养分元素含量分析的基础上,与包头市大量堆积的、严重威胁环境的三种固体废弃物(粉煤灰、水库淤积物和污水沉淀物)进行了对比研究。结果表明:该三种废弃物具有细粒、富含植物生长所必需之养分元素的特点。以该区荒漠化土壤作基本土壤,三种废弃物作土壤添加剂进行了玉米、沙棘树和草坪草的种植实验,结果显示:(1)三种废弃物添加到荒漠化土壤中,能够显著增加土壤的养分含量。(2)荒漠化土壤被改造成为近轻壤土的砂壤土或轻壤土。(3)改良后的土壤能够显著增加土壤的生物生产量。     

Environmental impact of radioactive waste management in the nuclear industry

Radioactive wastes from the nuclear industry are classified into low, intermediate and high activity levels, and problems of their storage and release examined in detail. Current means of storage are considered with reference to processing of low and intermediate level liquid waste, processing of high level waste, processing of airborne waste, and ground disposal and processing of solid waste. Release is discussed in terms of effluent release limits, monitoring and the use of permanent records, impact of release to the human environment, impact of release to the material environment, and guides for preventing accidental release. Contamination of the shore of Lake Huron from radioactive fallout is discussed as a particular example. Problems to be solved are identified in three main areas: gaseous wastes, actinide-contaminated wastes, and permanent disposal, and some specific suggestions for study are made.     

Characteristics of Medical Waste in Taiwan

The purpose of this study was threefold: to investigate the types and amounts of medical waste from various hospitals in Taiwan; to analyze residues from incinerated medical waste for heavy metal content; and to measure the amount of infectious and general medical waste per bed per day and determine the ratio of infectious to general medical waste. Information was first obtained on the amounts of medical waste produced per bed per day and on waste handling and treatment. Next, residue samples were taken from incinerators and analyzed for heavy metal content. Third, daily records concerning waste content and weight from one hospital were kept over the period of one year. Chromium (Cr) and zinc (Zn) concentrations were significantly higher in medical waste than in general waste. Medical waste fluctuated significantly over the one-year period. Records showed that wastes containing dialysis material and wood/cotton materials were found to have the highest weight and wastes containing human organs had the lowest weight. Results of the present study underscore the need for all hospitals to effectively separate waste for proper treatment and disposal, particularly waste that produces residues which may be hazardous to the environment. In addition, hospitals also need to recycle or reuse certain materials in order to reduce waste production.     

Water repellency of fly ash‐enriched forest soils from eastern Germany

Fly ash‐enriched soils occur widely throughout the industrial regions of eastern Germany and in other heavily industrialized areas. A limited amount of research has suggested that fly ash enrichment alters the water repellency (WR) characteristics of soil. This study concentrates on the influence of fly ash enrichment on WR of forest soils with a focus on forest floor horizons (FFHs). The soils were a Technosol developed from pure lignite fly ash, FFHs with lignite fly ash, and FFHs without lignite fly ash enrichment. Three different methods (water drop penetration time, WDPT, test; water and ethanol sorptivity measurement and the derived contact angle, θ_R; and the Wilhelmy‐plate method contact angle, θ_wpm) were used to characterize soil WR. Additionally, carbon composition was determined using ¹³C‐NMR spectra to interpret the influence of the organic matter. This study showed that the actual WR characteristics of undisturbed, fly ash‐enriched soils can be explained in terms of the composition of soil organic matter, with the fly ash content playing only a minimal role. Regardless of the huge amounts of mainly mineral fly ash enrichment, all undisturbed FFHs were comparable in their WR characteristics and their carbon compositions, which were dominated by recently‐formed organic substances. The pure fly ash deposit was strongly influenced by lignite remains, with the topsoil having a greater content of recent plant residues. Thus, the undisturbed topsoil was more repellent than the subsoil. When homogenized samples were used, we found a distinct effect of fly ash enrichment and structure on WR. Water repellency of the pure fly ash horizons did not differ distinctly, while the fly ash enrichment in the FFHs caused a significant reduction in WR. The methods used (WDPT, θ_R and θ_wpm) identified these differences similarly. These results led to the assumption that water‐repellent structures of the topsoils were probably the result of hydrophobic coatings of recently formed organic substances, whereby the initially high wettability of the mainly mineral, hydrophilic fly ash particles was reduced.     

农业固体废物分类及其污染风险识别和处理路径

防治农业固体废物污染,对保障农民身体健康,维护农业生态安全,促进农村经济社会可持续发展具有重要意义。在总结农业固体废物内涵和外延的基础上,探讨农业固体废物的主要来源、分类方法和基本特征,按照来源、毒性、组分和形态对农业固体废物进行了分类,剖析来源单一与类型多样的双重性、潜在污染与重要资源的两面性、周年持续与季节波动的复杂性等农业固体废物的基本特征。识别农业种植固体废物、畜禽水产养殖固体废物、废旧农业投入品和农产品初加工固体废物的潜在污染风险。梳理农业固体废物污染防治、处理利用代表性法规政策,分析农业固体废物全链条运营和监管体系,提出\     

Geochemical Assessment of Environmental Effects of Ash from Yatagan (Mugla-Turkey) Thermal Power Plant

Yatagan Thermal Power Plant consumes low-quality ligniteproduced from the Yatagan Basin, located in the western part ofthe Aegean region nearby Mugla City. The basin is aligned in anorthwest-southeast direction. The dominant wind direction isalso northwest-southeast, which controls the boundary of thewaste at the disposal site. In this study, the concentration of30 volatile elements was analyzed in coal, bottom ash, fly ashand background soil. The study area was divided into grids. The size of the grids was 1 km² for the background soiland 50–100 m for the ash in the vicinity of the wastedisposal site. 15 fly and bottom ash, six coal and nine-background soil samples were analyzed according to a sequential technique using ICP-AES. The results reveal that heavy metal concentrations in the coal are below the world averages for coal whereas those of bottom ash and fly ash arewithin the world averages for the respective ashes, indicatingheavy metal enrichment. It is recommended that extra care shouldbe taken to prevent subsurface contamination in the study area.     

Changes in soil acidity and the size and activity of the microbial biomass in response to the addition of sugar mill wastes

The effects of additions of three wastes from sugar mills on the properties of two acid soils were investigated. The wastes used were boiler ash and filter cake from a conventional mill and fly ash from a new mill, where filter cake is burnt. Additions of each of the wastes raised soil pH, reduced concentrations of exchangeable Al and total and monomeric Al in soil solution and increased maize yields in a pot experiment. Microbial biomass C and the percentage of organic C present as microbial biomass were decreased by additions of wastes but the effect was less marked at the higher rate of addition. Although basal respiration was decreased or unaffected by the lower rate of addition of wastes it was increased by the higher rate. The metabolic quotient increased in the order: control4⁺ and NO₃^- accumulated during incubation and arginine ammonification rate were all less at the higher rate of addition of each of the wastes. This was attributed to microbial immobilization of mineral N and arginine due to the wide C/N ratio of light fraction organic matter present in the study soil. It was concluded that all three waste materials were effective liming materials but their effect on soil microbial activity was complex.     

中国农村生活垃圾的产生量与物理特性分析及处理建议

中国农村生活垃圾对生态环境的污染日益严重,为给农村生活垃圾的管理提供相应的理论支撑和技术支持,促进"新农村"的建设,该文基于对西部6省18县59村580户农户的现场调研和全国25个省(市)128篇文献调研的数理统计,对中国农村生活垃圾的来源、产生率、产生量、组分、容重、可压缩性等特征进行了全面、系统的归纳总结与分析。结果表明:中国农村生活垃圾产生率介于0.034~3.000 kg/(人·d)之间,中位值为0.521 kg/(人·d),2014年产生量达到1.48亿t,具有来源广泛且分散、产率低、产量高、增长迅速、区域差异显著等特点。生活垃圾主要组分包括厨余类、灰土类、橡塑类和纸类,其湿基质量累计百分比达到了83.61%,区域差异显著;与城市生活垃圾组分相比,具有低厨余和金属、高灰土含量的特点,并逐渐趋于城市化。生活垃圾的容重介于40~650 kg/m~3之间,平均值为263 kg/m~3,可压缩性较好。根据生活垃圾特性,在实施"村收集-镇运输-县处理"管理模式的农村,建议采用压缩式中转站和垃圾车进行收运;在有条件的农村地区,可逐步开展垃圾分类收集,将厨余和灰土从生活垃圾中分离后就地消纳。     

Studies on the Phase Mineralogy and Leaching Characteristics of Coal Fly Ash

The phase mineralogy and leaching characteristics of some Indian coal fly ashes were studied to assess their safe disposal in abandoned coal mines. Since, fly ash contains a number of toxic trace elements, the leaching of fly ash was tested using strong acid/alkali solutions and distilled water under different conditions (solid-liquid ratio, leaching time, pH) in the temperature range of 30-100 °C. It was found that the concentration of various metals in leachates depends on their chemical nature, association with mineral phases of ash and follows the almost similar concentration profile to that of iron, especially in acidic medium. The distribution of toxic trace elements in fly ash and their leachability were found to depend on the amount of unburnt carbon and iron in fly ash. In alkaline medium, leaching of iron and toxic trace elements (except As) from fly ash was very negligible. Hence, alkali treatment of coal fly ash is desirable for its safe use in refilling of coal mines.     

The Effect of Yatagan Thermal Power Plant (Mugla,Turkey) on the Quality of Surface and Ground Waters

Yatagan thermal power plant consumes annually 5.4 million tons of coal and the annual production capacity of the plant is 3.78 billion KWh. The thermal power plant uses 15 000 tons of coal and discharges 5000 tons of fly and bottom ash daily to the disposal site. The waste is dumped using conveyer belts and pipes into a dam founded on metamorphic rocks. However, as the waste hills formed, the water level reached the karstic marbles that over lay schist. Water leaches through dried waste hills and karstic marbles, ultimately adversely affecting the quality of ground and surface waters. The concentrations of major and minor ions were determined on water samples taken at 2 points in the dam, 5 points in surface water and at 21 points in groundwater located in the vicinity of the waste disposal site, total of 28 samples, for three years. The chemical analyses revealed that the concentrations of Ca²⁺, Cd²⁺, Pb²⁺, Sb²⁺ and SO₄ ^2- in some samples exceed the Turkish Drinking Water, the U.S. EPA and WHO limits. Isotope analyses were carried out to determine the origins of waters, which showedthat contamination is taking place in the vicinity of the waste disposal site.     

The use of Folsomia candida (Collembola,Isotomidae) in bioassays of waste

There is a high probability that urban compost, sewage sludge and ash will come in contact with natural terrestrial ecosystems. The present paper investigates the extent to which the Folsomia candida population development test (now a standardised ecotoxicological test, ISO 11267, for testing the impact of pure chemicals on soil fauna) can be applied to the detection of the toxicity of these wastes, the goal being to evaluate ecotoxicity of wastes before they are spread on land. We show that some potentially useful information on waste toxicity can be obtained with this test, but the results must be interpreting with caution, indeed, problems can arise from differences in pH, humidity and organic matter content of the waste relative to the characteristics of the dilution soil. On the basis of the results of these assays, we propose a classification of the toxicity of seven wastes.