Life cycle assessment of heavy metal contaminated sites: phytoremediation and soil excavation.

Phytoextraction by native Taiwanese chenopod (Chenopodium formosanum Koidz.) and Napier grass (Pennisetum purpureum) for heavy metals such as chromium (Cr), nickel (Ni), and copper (Cu) was reported first. Maximum bioconcentration factors of Cu and Cr were 8.8 and 12.5 by Taiwanese chenopod. Napier grass cultivar Taishi No.4 plants demonstrated higher survivals than that of Taiwanese chenopod, under heavy metal stress in soils. All heavy metal accumulation and biomass data were employed, as well as historical engineering data were collected for conventional excavation-and-refill remediation of two sites. Life cycle assessment (LCA) was conducted for comparing environmental performances of phytoextraction and conventional remediation for two contaminated sites. Assuming one-year growth, three harvests were done and biomass was collected and sent to the nearest municipal incinerators, phytoextraction by both plants demonstrated superior environmental performances than conventional methods for contaminated site remediation. High quantities of fuels to haul the soils of conventional methods mainly contributed to the greenhouse gas emission. Phytoextraction has the most advantages for sites with lesser extents of pollution and time restraints. Environmental performances of phytoremediation were even better if energy recovered from biomass incineration is counted. Novelty statement Phytoextraction by native Taiwanese chenopod and Napier grass was firstly reported. Life cycle assessment was conducted for comparing the phytoextraction and conventional remediation. Phytoextraction demonstrated superior environmental performances. Energy reutilization of biomass recovered made phytoremediation more sustainable.

Effect of Paenibacillus cellulase pretreatment for fiber surface.

Refining is the major process of paper formation. This study focuses on the impact of a specific enzyme (Paenibacillus cellulase) for fibers on the surfaces, the roughness and height of the fibers are also investigated. Effects of enzyme dosages and the mechanical refining action (PFI revolution) on fiber physical properties were also analyzed. The fibers were observed by scanning electron microscopy (SEM), their roughness and height were analyzed by Atomic force microscopy (AFM). Results show that the Paenibacillus cellulase pretreatment increased the drainability of both kinds of pulp at the same level of refining energy. In other words, enzymatic treatment on pulp refining consumed less refining revolutions to reach the same drainability compared to the untreated pulp. Although the viscosity of both kinds of pulp was degraded with the enzymatic treatment, the physical properties of paper had no significantly negative influence on them. The results indicated the treatment with cellulase swelled the fibers in the absence of refining, and there were better fibrillation on the fibers treated with cellulase after refining. Furthermore, the statistical analysis of AFM suggested that both kinds of pulp treated with low cellulase dosage with PFI refining had higher roughness.

Bioethanol production from recovered napier grass with heavy metals.

Using plants to absorb and accumulate heavy metals from polluted soil, followed by the recycling of explants containing heavy metals, can help achieve the goal of reverting contaminated soil to low heavy-metal content soil. However, the re-use of recovered explants can also be problematic. Meanwhile, bioethanol has become a popular energy source. In this study, napier grass was used for the remediation of soil contaminated with heavy metals (artificially contaminated soil). The influence of bioethanol production from napier grass after phytoremediation was also investigated. The concentration of Zn, Cd, and Cr in the contaminated soil was 1000, 100, and 250 mg/kg, respectively. After napier grass phytoremediation, the concentration (dry biomass) of Zn, Cd, and Cr in the explants was 2701.97 ± 173.49, 6.1 ± 2.3, and 74.24 ± 1.42 mg/kg, respectively. Biomass production in the unpolluted soil was 861.13 ± 4.23 g. The biomass production ratio in high Zn-polluted soil was only 3.89%, while it was 4.68% for Cd and 21.4% for Cr. The biomass obtained after napier grass phytoremediation was pretreated using the steam explosion conditions of 180 °C, for 10 min, with 1.5% H2SO2, followed by enzymatic hydrolysis. The efficiency of enzymatic hydrolysis for Zn-polluted biomass was 90% of the unpolluted biomass, while it was 77% for Cd, and approximately the same for Cr. The fermentation efficiency of the heavy-metal-containing biomass was higher than the control biomass. The fermentation ethanol concentration obtained was 8.69-12.68, 13.03-15.50, and 18.48-19.31 g/L in Zn, Cd, and Cr environments, respectively. Results show that the heavy metals had a positive effect on bacteria fermentation. However, the fermentation efficiency was lower for biomass with severe heavy metal pollution. Thus, the utilization of napier grass phytoremediation for bioethanol production has a positive effect on the sustainability of environmental resources.

Phytoremediation of heavy metal contaminated soil by Jatropha curcas.

This study employed Jatropha curcas (bioenergy crop plant) to assist in the removal of heavy metals from contaminated field soils. Analyses were conducted on the concentrations of the individual metals in the soil and in the plants, and their differences over the growth periods of the plants were determined. The calculation of plant biomass after 2 years yielded the total amount of each metal that was removed from the soil. In terms of the absorption of heavy metal contaminants by the roots and their transfer to aerial plant parts, Cd, Ni, and Zn exhibited the greatest ease of absorption, whereas Cu, Cr, and Pb interacted strongly with the root cells and remained in the roots of the plants. J. curcas showed the best absorption capability for Cd, Cr, Ni, and Zn. This study pioneered the concept of combining both bioremediation and afforestation by J. curcas, demonstrated at a field scale.

Extraction of heavy metals from contaminated soil by Cinnamomum camphora.

83 acres of rice paddy fields in Taoyuan county, Taiwan, were polluted by cadmium (Cd), chromium (Cr) and copper (Cu) through a nearby irrigation channel, and rice plantation was ceased in 1987. Camphor trees (Cinnamomum camphora) have been planted in 2 acre of the above fields since 1991. Heavy metal accumulation of roots, leaves, branches and heartwood of camphor trees were analyzed during 20-year afforestation. Averaged Cd contents of the roots were found larger than the ones of the branches, leaves, sapwood and heartwood of camphor trees growing in three polluted plots. Averaged diameters at breast height (DBH) of the planted camphor trees were 13-15 cm. Cd pollution did not significantly impact the growth of camphor trees, as similar DBH's were found from both polluted and control sites. Annual growths of DBH were from 0.63 to 0.77 cm year(-1). Planting camphor trees sequestered 68.8 ton biomass per acre. During 20-year period, 0.69-1.98 ton C year(-1) ha(-1) were sequestered on three polluted plots. The above numbers exceeded IPCC LULUCF reference values 0.31-0.53 ton C year(-1) ha(-1) for activities at forest lands.

Reduction behavior of zinc ferrite in EAF-dust recycling with CO gas as a reducing agent.

EAF-dust containing metal oxides can be regarded as an important source for zinc and iron. In this study, the reduction behavior of zinc ferrite with CO gas as a reducing agent under different temperatures was investigated to develop a new process for the recovery of zinc and iron from EAF-dust. The results of the phase studies with synthetic franklinite show that zinc substituted wustite, and spinel with low zinc content formed at lower temperatures from 450 to 850 °C due to incomplete zinc-iron-separation. Zinc ferrite was completely reduced to metallic zinc and iron at 950 °C. After evaporation and condensation, metallic zinc was collected in the form of zinc powder while iron, the reduction residue, was obtained in the form of direct reduced iron (DRI). The mass balance indicates a high zinc recovery ratio of over 99%. The new treatment process by thermal reduction with CO gas as a reducing agent achieved higher recovery and metallization grade of both zinc and iron from EAF-dust at lower temperatures than other commercial processes. The metallic products can be used directly as semi-products or as raw materials for refinery.

Factors affecting chelating extraction of Cr, Cu, and As from CCA-treated wood.

The disposal of chromated copper arsenate (CCA)-treated waste wood is becoming a serious problem in many countries due to potential leaching of hazardous elements from in-service use in the environment or disposal of solutions after remediation; therefore, it is necessary to develop proper remediation techniques. The effects of concentration, extraction period, temperature, and sequential extraction on the extraction of Cr, Cu, and As from CCA-treated wood using [S,S]-ethylenediaminedisuccinic acid (EDDS), ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid (NTA) were studied. Mobility of metal in the samples was evaluated by using a sequential extraction scheme that could give the information needed to explain different extraction efficiencies for different metals. Results of long-term leaching tests of CCA-treated wood before and after EDDS extraction were used to evaluate Cr, Cu, and As leachability. Kinetic experiments showed that 6 h was the optimum extraction time for all metals and CCA-treated wood. Experimental results showed that EDDS is a very effective chelating agent for the extraction of Cr, Cu, and As from CCA-treated wood. Increased temperature significantly enhanced the extraction efficiency of CCA metals, especially Cr and As. The much better extractability of Cu compared to Cr and As by chelating agents can be attributed to the presence of larger weakly bound fractions. The CCA-treated woods after EDDS extraction have met the EPA's TCLP regulatory limit and could be classified as a non-hazardous waste according to identification standard of hazardous wastes.

Tracking of arsenics during the thermal stabilization of an AsH3 scrubber sludge.

Toxic arsenics in an AsH(3) scrubber sludge were thermally stabilized in the temperature range of 973-1,373 K. To better understand how the high-temperature treatments can stabilize arsenics in the sludge, their synchrotron X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of arsenics were determined. It is found that the reduced arsenic leachability may be associated with the formation of As(2)O(5) (51-59%) and embedded As(V) within the Ca(3)(PO(4))(2) matrix (41-49%) in the stabilized sludge. In addition, the As-O bond distances in the stabilized As(2)O(5) are much less than that of normal As(2)O(5) by 0.05-0.07 Å. The shorter As-O bond distances accompanied with the higher bonding energy also have a contribution to the thermal stabilization of arsenics.

Optogenetic stimulation in the medial prefrontal cortex modulates stimulus valence from rewarding and aversive to neutral states.

Introduction: Understanding the modulations of the medial prefrontal cortex (mPFC) in the valence of the stimulus from rewarding and aversive status to neutral status is crucial for the development of novel treatments for drug addiction. This study addressed this issue and examined whether optogenetic ChR2 photostimulation in the cingulate, prelimbic, and infralimbic cortices of the mPFC regulated the valence of saccharin solution consumption from the rewarding property, the aversive property induced by morphine's conditioning, and the neutral states via saccharin extinction processes after morphine's conditioning. Methods: All rats received virus infection, buried optical fiber, optical stimulation, water deprivation, and saccharin solution consumption phases. In Experiment 1, rats were given ChR2 virus infection into the cingulate cortex (Cg1), prelimbic cortex (PrL), and infralimbic cortex (IL) to influence the rewarding saccharin solution consumption under photostimulation. In Experiment 2, rats were given ChR2 or EYFP virus infection into the Cg1, PrL, and IL to alter the saccharin solution consumption in the morphine-induced aversively conditioned taste aversion (CTA) and the saccharin solution consumption in the neutral state following the extinction process under photostimulation. Later, the immunohistochemical staining with c-Fos protein was performed for the Cg1, IL, PrL, nucleus accumbens core, nucleus accumbens shell, central amygdala, basolateral amygdala, ventral tegmental area, and dentate gyrus. Results: The results showed that optogenetic PrL stimulation decreased the rewarding valence of saccharin solution consumption and increased the morphine-induced, aversive valence of saccharin solution consumption. PrL stimulation decreased the neutral valence of saccharin solution consumption via the extinction process. Cg1 optogenetic stimulation increased the rewarding valence of saccharin solution consumption and the aversive valence of saccharin solution consumption induced by morphine in conditioning. Optogenetic IL stimulation increased the aversive valence of saccharin solution consumption induced by morphine via conditioning. Conclusion: Altogether, optogenetic stimulation in the subareas of the mPFC modulated the reward, aversion, and neutral valences of the stimulus and altered neuronal activity in the mPFC, amygdala, nucleus accumbens, and hippocampus. Notably, the change of valence was temporary alternation during light-on related to the light-off periods. However, the findings may provide insights in the development of novel treatments for addictive symptoms.

Determination of glyphosate, aminomethylphosphonic acid, and glufosinate in river water and sediments using microwave-assisted rapid derivatization and LC-MS/MS.

Glyphosate (N-phosphonomethyl glycine) and glufosinate (ammonium dl-homoalanin- 4-methyl phosphinate) are nonselective, broad-spectrum, and highly polar herbicides that are wildly used for weed control in aquatic systems and vegetation control in non-crop areas. Aminomethylphosphonic acid (AMPA) is the major degradation product of glyphosate. To address the concerns to its environmental residue and the possible adverse effects, the analytical methods by using microwave-assisted derivatization were developed for determining glyphosate, AMPA, and glufosinate in river water and sediments. The methods applied the 9-fluorenylmethyloxycarbonyl chloride (FMOC-Cl) derivatization for the analytes. The microwave heating is first-time applied to reduce the FMOC-reaction time of glyphosate, AMPA, and glyphosate in the environmental samples to less than 2.5 min. The microwave-assisted methods were successfully validated for river water and sediment. The linear ranges of 7.8-2000.0 ng/L and 0.78-100.0 ng/g were achieved by using 10 mL of water and 2 g of sediments. Glyphosate was found in 30/32% and 25/32% of 32 water and 32 sediments at 27.1-1353.9 ng/L and 2.4-189.6 ng/g levels. AMPA was found in 30/32% and 30/32% of 32 water and 32 sediments at 60.2-1509.0 ng/L and 1.8-233.6 ng/g levels. Glyphosate was found in 10/32% of 32 water at 14.8-503.1 ng/L levels. No glufosinate residue was observed for 32 sediments. The residues of glyphosate and AMPA were wildly detected in the river waters and sediments near the agricultural regions, and glufosinate was less detected. This is the first study that reported herbicide levels in water and sediment from Taiwan rural areas using microwave-assisted rapid derivatization, useful information for environmental management.

Functional Plasticity of Foraging Shelter Tubes Built by Termites.

Social insects' constructions are diverse and functionally flexible. We aimed to understand how termites modify their behavior and building material to change the function of a shelter tube. Construction behaviors of three termite species, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), Odontotermes formosanus (Shiraki) (Blattodea: Termitidae), and Nasutitermes takasagoensis (Nawa) (Blattodea: Termitidae), were recorded and analyzed. We measured the thickness and organic matter content of shelter tubes, and further tested their water loss and water drop resistance. All three termite species used a cement-brick construction procedure. The shelter tubes of C. formosanus and N. takasagoensis incorporating of woody material and feces present a strong resistance to water drops. Shelter tubes of the fungus-growing termite, O. formosanus, constructed using only soil and fluid secretion had a weak resistance to water drops. The trade-off between using feces to increase hydrophobicity of shelter tubes and using feces to grow fungus likely occurs in fungus-growing termites. Among intraspecific colonies, increasing the thickness of shelter tube improved resistance to water loss and water drops. This study demonstrated termites employed limited construction material and building behaviors to achieve functional plasticity of foraging shelter.

The Medial Prefrontal Cortex, Nucleus Accumbens, Basolateral Amygdala, and Hippocampus Regulate the Amelioration of Environmental Enrichment and Cue in Fear Behavior in the Animal Model of PTSD.

A growing body of evidence showed that environmental enrichment (EE) ameliorated footshock-induced fear behavior of posttraumatic stress disorder (PTSD). However, no research comprehensively tested the effect of EE, cue, and the combination of EE and cue in footshock-induced fear behavior of PTSD symptoms. The present study addressed this issue and examined whether the medial prefrontal cortex (mPFC, including the cingulate cortex 1 (Cg1), prelimbic cortex (PrL), and infralimbic cortex (IL)), the nucleus accumbens (NAc), the basolateral amygdala (BLA), and the hippocampus (e.g., CA1, CA3, and dentate gyrus (DG)) regulated the amelioration of the EE, cue, or the combination of EE and cue. The results showed that EE or cue could reduce fear behavior. The combination of EE and cue revealed a stronger decrease in fear behavior. The cue stimulus may play an occasion setting or a conditioned stimulus to modulate the reduction in fear behavior induced by footshock. Regarding the reduction of the EE in fear behavior, the Cg1 and IL of the mPFC and the NAc upregulated the c-Fos expression; however, the BLA downregulated the c-Fos expression. The mPFC (i.e., the Cg1, PrL, and IL) and the hippocampus (i.e., the CA1, CA3, and DG) downregulated the c-Fos expression in the suppression of the cue in fear behavior. The interaction of EE and cue in reduction of fear behavior occurred in the Cg1 and NAc for the c-Fos expression. The data of c-Fos mRNA were similar to the findings of the c-Fos protein expression. These findings related to the EE and cue modulations in fear behavior may develop a novel nonpharmacological treatment in PTSD.

Nucleophosmin in the pathogenesis of arsenic-related bladder carcinogenesis revealed by quantitative proteomics.

To investigate the molecular mechanisms of arsenic (As)-associated carcinogenesis, we performed proteomic analysis on E7 immortalized human uroepithelial cells after treatment with As in vitro. Quantitative proteomics was performed using stable isotope dimethyl labeling coupled with two-dimensional liquid chromatography peptide separation and mass spectrometry (MS)/MS analysis. Among 285 proteins, a total of 26 proteins were upregulated (ratio>2.0) and 18 proteins were downregulated (ratio<0.65) by As treatment, which are related to nucleotide binding, lipid metabolism, protein folding, protein biosynthesis, transcription, DNA repair, cell cycle control, and signal transduction. This study reports the potential significance of nucleophosmin (NPM) in the As-related bladder carcinogenesis. NPM was universally expressed in all of uroepithelial cell lines examined, implying that NPM may play a role in human bladder carcinogenesis. Upregulation of NPM tends to be dose- and time-dependent after As treatment. Expression of NPM was associated with cell proliferation, migration and anti-apoptosis. On the contrary, soy isoflavones inhibited the expression of NPM in vitro. The results suggest that NPM may play a role in the As-related bladder carcinogenesis, and soybean-based foods may have potential in the suppression of As/NPM-related tumorigenesis.

Artificial aggregate made from waste stone sludge and waste silt.

In this research, waste stone sludge obtained from slab stone processing and waste silt from aggregate washing plants were recycled to manufacture artificial aggregate. Fine-powdered stone sludge was mixed with waste silt of larger particle size; vibratory compaction was applied for good water permeability, resulting in a smaller amount of solidifying agent being used. For the densified packing used in this study, the mix proportion of waste stone sludge to waste silt was 35:50, which produced artificial aggregate of more compact structure with water absorption rate below 0.1%. In addition, applying vibratory compaction of 33.3 Hz to the artificial aggregate and curing for 28 days doubled the compressive strength to above 29.4 MPa. Hence, recycling of waste stone sludge and waste silt for the production of artificial aggregate not only offers a feasible substitute for sand and stone, but also an ecological alternative to waste management of sludge and silt.

Treatment of septic tank effluents by a full-scale capillary seepage soil biofiltration system.

The purpose of this study is to evaluate the efficiency of septic tank effluent treatment by an underground capillary seepage soil biofiltration system in a suburban area of Taipei, Taiwan. In contrast to traditional subsurface wastewater infiltration systems, capillary seepage soil biofiltration systems initially draw incoming influent upwards from the distribution pipe by capillary and siphonage actions, then spread influent throughout the soil biofiltration bed. The underground capillary seepage soil biofiltration system consists of a train of underground treatment units, including one wastewater distribution tank, two capillary seepage soil biofiltration units in series, and a discharge tank. Each capillary seepage soil biofiltration unit contains one facultative digestion tank and one set of biofiltration beds. At the flow rate of 50 m3/day, average influent concentrations of biochemical oxygen demand (BOD), suspended solid (SS), ammonia nitrogen (NH3-N), and total phosphates (TP), were 36.15 mg/L, 29.14 mg/L, 16.05 mg/L, and 1.75 mg/L, respectively. After 1.5 years of system operation, the measured influent and effluent results show that the treatment efficiencies of the soil biofiltration system for BOD, SS, NH3-N, TP, and total coliforms are 82.96%, 60.95%, 67.17%, 74.86%, and 99.99%, respectively.

Enhancement of phytoextraction by Taiwanese chenopod and Napier grass by soapnut saponin and EDDS additions.

Employment of biosurfactants and biodegradable chelants could further promote sustainability of soil and groundwater remediation tasks. Biosurfactant (soapnut saponin) and biodegrading chelants (ethylenediamine-N,N'-disuccinic acid (EDDS)) were employed to enhance the phytoextraction by native Taiwanese chenopod (Chenopodium formosanum Koidz.), Napier grass (Pennisetum purpureum) cultivar Taishi No. 4, and soapwort (Saponaria officinalis). Ethylene diamine tetraacetic acid (EDTA) was also employed as the control. Contaminated soils as silty clay loam texture was collected from a defunct rice paddy, containing chromium (Cr), cadium (Cd), and copper (Cu). Addition of both soapnut saponin and EDDS proportionally increased bioaccumulation factors (BCFs) of aboveground biomass for all three plants. Taiwanese chenopod demonstrated the best BCF values among three plants, with BCF increased from 0.76 to 2.6 and 1.3 for Cu under the presence of the highest dosages of EDDS and saponin. Plant aboveground biomass did exhibit negative correlation toward biomass metal concentrations. Presence of saponin did exhibit the least negative slopes among the correlations of all three additives for three plants. Taiwanese chenopod did exhibit the least negative slopes among the correlations of all three additives for three plants. Above observations suggested that saponin may have some protection for plants, especially for Napier grass. Taiwanese chenopod could possess more tolerance toward heavy metals than Napier grass does.

A combined analytical method for biological monitoring of arsenic, benzene and polycyclic aromatic hydrocarbons in human urine by liquid chromatography tandem mass spectrometry.

An analytical method for the biomonitoring of arsenic, benzene and polycyclic aromatic hydrocarbons (PAHs) in human urine was developed using liquid chromatography tandem mass spectrometry (LC-MS/MS). The urinary metabolites of monomethylarsonic acid (MMAA), dimethylarsonic acid (DMAA), s-phenylmercapturic acid (S-PMA), and 1-hydroxypyrene (1-OHP) were selected as the corresponding marker compounds. After enzymatic deconjugation, 4 mL urine sample was extracted by 2 steps of solvent extractions. The 1-OHP was first extracted with n-hexane with 10% ethyl acetate, and MMAA, DMMA, and S-PMA were then extracted in a 2nd extraction/back-extraction using chloroform/ammonium bicarbonate aqueous solution. The two extracts were mixed and analyzed by LC-MS/MS. The method was validated with spiked urine samples. The obtained linear ranges (r2 > 0.99) of the urinary markers were 2-64 ng/mL MMAA, 1-64 ng/mL DMAA, 0.78-100 ng/mL S-PMA and 0.05-6.4 ng/mL 1-OHP. The measured accuracy (% Error) and precision (CV%) were -16.67 to 29.17% and 2.03-30.99% (3 spiked levels, 6 replicates), respectively. The method was applied to 10 real urine samples, and the presence of MMAA, DMAA, S-PMA and 1-OHP were clearly detected. The detected concentrations were BQL-8.38 ng/mL of MMAA, BQL-10.71 ng/mL of DMAA, BQL-2.55 ng/mL of SPMA, and BQL-0.17 ng/mL of 1-OHP, which were all consistent with the reported background levels.

Agricultural waste derived fuel from oil meal and waste cooking oil.

Oil meal is a by-product of the oil industry (peanut meal, sesame meal, and camellia meal). Oil is extracted from seeds, and the leftover meal is then pelletized, and this process generates a large amount of waste oil meal in Taiwan. In this study, peanut meal, sesame meal, and camellia meal derived fuels were prepared from the waste oil meal with waste cooking oil. The combustion behaviors of the oil meal derived fuels were also investigated. The characteristics of the derived fuel made from oil meal with waste cooking oil showed that the ash content is less than 10% and its calorific value reached 5000 kcal/kg. Additionally, the activation energy of the oil meal and waste cooking oil was analyzed by the Kissinger method. The results show that the fuel prepared in this work from the oil meal mixed with waste cooking oil is suitable for use as an alternative fuel and also avoids food safety issues.

Production of lightweight aggregates from mining residues, heavy metal sludge, and incinerator fly ash.

In this study, artificial lightweight aggregate (LWA) manufactured from recycled resources was investigated. Residues from mining, fly ash from an incinerator and heavy metal sludge from an electronic waste water plant were mixed into raw aggregate pellets and fed into a tunnel kiln to be sintered and finally cooled rapidly. Various feeding and sintering temperatures were employed to examine their impact on the extent of vitrification on the aggregate surface. Microstructural analysis and toxicity characteristic leaching procedure (TCLP) were also performed. The results show that the optimum condition of LWA fabrication is sintering at 1150 degrees C for 15 min with raw aggregate pellets fed at 750 degrees C. The rapidly vitrified surface envelops the gas produced with the increase in internal temperature and cooling by spraying water prevents the aggregates from binding together, thus forming LWA with specific gravity of 0.6. LWA produced by sintering in tunnel kiln shows good vitrified surface, low water absorption rate below 5%, and low cylindrical compressive strength of 4.3 MPa. In addition, only trace amounts of heavy metals were detected, making the LWA non-hazardous for construction use.

Sequential extraction for evaluating the leaching behavior of selected elements in municipal solid waste incineration fly ash.

A sequential extraction method has been applied for the determination of binding forms of trace elements in the municipal solid waste incineration (MSWI) fly ash and evaluating their leaching behavior in view of their potential environmental impact. The elemental determinations in the different leachates are performed by ICP-AES and ICP-MS, respectively. The morphology and mineralogical phases after extraction step were performed by scanning electron microscopy (SEM). Total of 20 elements in the samples are investigated. A reference material of city waste incineration fly ash (BCR No. 176) is also tested to examine the applicability as well as accuracy of the proposed method. The sum of most elements present in the individual fractions shows a good agreement with the total elemental concentrations. The extraction efficiencies are generally higher than 80% except for that of Cr and V. The extractable data of most elements give information about the binding forms of various elements in both incineration fly ashes. It was found that the elements such as Ca, K, Na, Pb, Zn, Cd, Cu and Sr have exhibited a remarkable mobility in fly ash. More than half of them would be dissolved or exchanged under a mild leaching condition. The toxic elements such as Pb, Cd, Zn and Cu have a great potential to be released into the environment under normal conditions.