Chemical Recycling of Polyamide Waste at Various Temperatures and Pressures Using High Pressure Autoclave Technique

Chemical recycling of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of 150, 200, 210, 220,230 and 240 °C and at various pressures of 100, 200, 300, 400, 500, 600 and 700 psi (pound per square inch). Viscosity average molecular weight of the polyamide waste sample was determined by Ostwald method and recorded as 1.928 × 10³. The reaction was found to be first order with velocity constant in order of 10⁻² min⁻¹. The velocity constant and percent conversion of depolymerization reaction at 240 °C and 700 psi pressure were recorded as 2.936 × 10⁻² min⁻¹ and 99.99% respectively. The velocity constant was obtained on the basis of measurement of amine value. Kinetic and thermodynamic parameters such as energy of activation, frequency factor, enthalpy of activation were found to be 10.6 kJ mole⁻¹, 0.3719 min⁻¹ and 6.3 kJ mole⁻¹ respectively, at the optimum conditions for maximum depolymerization of polyamide waste.     

Simulation of substrate degradation in composting of sewage sludge

To simulate the substrate degradation kinetics of the composting process, this paper develops a mathematical model with a first-order reaction assumption and heat/mass balance equations. A pilot-scale composting test with a mixture of sewage sludge and wheat straw was conducted in an insulated reactor. The BVS (biodegradable volatile solids) degradation process, matrix mass, MC (moisture content), DM (dry matter) and VS (volatile solid) were simulated numerically by the model and experimental data. The numerical simulation offered a method for simulating k (the first-order rate constant) and estimating k₂₀ (the first-order rate constant at 20 °C). After comparison with experimental values, the relative error of the simulation value of the mass of the compost at maturity was 0.22%, MC 2.9%, DM 4.9% and VS 5.2%, which mean that the simulation is a good fit. The k of sewage sludge was simulated, and k₂₀, k_20s (first-order rate coefficient of slow fraction of BVS at 20 °C) of the sewage sludge were estimated as 0.082 and 0.015 d^?1, respectively.     

The Transit of 35SO4 2- and 3H2O Added In Situ to Soil in a Boreal Coniferous Forest

A solution containing ³⁵SO₄ ^2- and ³H₂O was applied to four plots (5 × 5 m) in a boreal coniferous forest in the Laflamme Lake watershed, Québec, under two contrasting conditions: in summer (plots 1 and 2), and on the snowpack before snowmelt (plots 3 and 4). The transit of both these tracers in the soil solution was then followed through a network of soil lysimeters located at different depths. Four months after the summer application, ³H₂O had infiltrated the whole soil profile at plot 1, while ³⁵SO₄ ^2- was only observed in the LFH and Bhf horizons. A ³⁵SO₄ ^2- budget calculated from mid-August to November indicated that 89 and 10.6% of the added ³⁵SO₄ ^2- was retained within the LFH and the Bhf layers, respectively. Fifteen months later, the added ³⁵SO₄ ^2- was distributed in the following proportions within the soil horizons: LFH (73.7%), Bhf (11.8%) and Bf (12.8%), for a total retention rate of 98.3%. The superficial penetration of ³H₂O at plot 2 was indicative of a major lateral water movement that prevented the calculation of a ³⁵SO₄ ^2- budget. This situation also was observed at plot 4 during snowmelt. At plot 3, ³H₂O moved freely through the soil profile and a significant fraction of the added ³⁵SO₄ ^2- reached the B horizons, where it was presumably adsorbed on aluminum (Al) and ferric (Fe) oxides. The ³⁵SO₄ ^2- budget for plot 3 from March to November indicated that 87% of the added ³⁵SO₄ ^2- was retained within the soil profile, with most being retained in the B horizons (LFH = 33.1%, Bhf = 33.1%, Bf = 20.8%). The contrasting retention patterns of ³⁵SO₄ ^2- within the soil profile following the summer addition and snowmelt likely was caused by the contrastingsoil temperatures and soil solution residence times within the differentsoil layers. The persistence of ³⁵SO₄ ^2- in the soil solution of the entire profile long after the initial tracer infiltration, and the relative temporal stability of specific activity of SO₄ ^2-, point to the establishment of an isotopic equilibrium between the added ³⁵SO₄ and the active S-containing reservoirs within a given soil horizon. Overall, the results clearly illustrate the very strong potential for ³⁵SO₄ ^2- retention and recycling in forest soils.     

Decomposition of dichloromethane and in situ alkali absorption of resulting halogenated products by a packed-bed non-thermal plasma reactor

For an effective decomposition and removal of organic halogenated compounds, a packed-bed non-thermal plasma reactor with in situ absorption of the resulting halogenated products by alkaline sorbent incorporated was proposed. In the plasma reactor, α-Al₂O₃ particles of 1 and 3 mm (mean particle diameter) were packed as solid dielectric medium to enhance the plasma power density in the reactor. Further, alkaline sorbent of Ca(OH)₂ was doped onto the surface of α-Al₂O₃ particles, in order to remove halogenated products by in situ absorption with Ca(OH)₂. A high-voltage and high-frequency pulsed power of −15 to 15 kV and 1 kHz was applied to the wire electrode of the plasma reactor by means of a DC power source. In the present study, as the sample of an organic halogenated compound that is most popularly used, we selected dichloromethane (CH₂Cl₂), and 500 ppm of the initial concentration of CH₂Cl₂ was fed into the reactor accompanied by air at a fixed flow rate of 500 × 10⁻⁶ m³ min⁻¹ at room temperature. As a result, it was recognized that the amount of CH₂Cl₂ decomposed by non-thermal plasma in an α-Al₂O₃ particle bed increased with an increase in plasma input power. The ratio of decomposition of CH₂Cl₂ was almost 100% at 13 kV of electric power and 1 kHz frequency, and CO₂, CH₃Cl, COCl₂, HCl, and Cl₂ were observed as the major reaction products. On the other hand, when CH₂Cl₂ was introduced into the plasma reactor where α-Al₂O₃ particles doped with Ca(OH)₂ were packed, the ratio of decomposition of CH₂Cl₂ became higher, compared to the case that α-Al₂O₃ particles were not doped with Ca(OH)₂. Moreover, there were no halogenated by-product gases detected in the outlet gas from the reactor. As the solid reaction products, CaClOH and Ca(ClO)₂·4H₂O were detected on Ca(OH)₂ by X-ray diffraction. From these findings, it was recognized that CH₂Cl₂ was decomposed more effectively without producing unwanted harmful halogenated by-products in the proposed non-thermal plasma reactor where α-Al₂O₃ particles doped with Ca(OH)₂ sorbent were packed.     

Degradation of Monophenylheptamethylcyclotetrasiloxane and 2,6-cis-Diphenylhexamethylcycloterasiloxane in Londo Soil

The natural degradation of monophenylheptamethylcyclotetrasiloxane and 2,6-cis-diphenylhexamethylcyclotetrasiloxane in soil was evaluated under laboratory conditions. Both monophenyl and 2,6-cis underwent rapid degradation in dry soil generating the same products in varying proportions. During the first 24 hr, approximately 99% of the two materials underwent significant chemical transformations forming silanols of various structures, dimethyl cyclic siloxanes of the structure (Me₂SiO)x, and rearrangement products (geometrical isomers) of diphenylhexamethylcyclotetrasiloxane. Among the silanols, the following were identified as trimethylsilyl derivatives: HOSiMe₂OH, HOSiMePhOH, HOSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OH, HOSiMePhOSiMePhOH, HOSiMe₂OSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OSiMe₂OH, HOSiMe₂OSiMePhOSiMe₂OH, HOSiMePhSiMe₂OSiMePhOH, HOSiMePhOSiMePhOSiMe₂OH, HOSiMePhOSiMe₂OSiMe₂OSiMe₂OH, HOSiMe₂OSiMePhOSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OSiMePhOSiMe₂OH, HOSiMePhOSiMePhOSiMe₂OSiMe₂OH, HOSiMePhOSiMe₂OSiMe₂OSiMePhOH, HOSiMe₂OSiMePh-OSiMePhOSiMe₂OH. Derivatization was carried out using bis(trimethylsilyl)trifluoroacetamide. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry (atmospheric pressure chemical ionization) analyses were used to derive structures. Structures were confirmed by gas chromatography-mass spectrometry comparisons of synthetic standards. Degradation was slower in wet soil. Nevertheless, in 14 days, the chemical transformation was essentially found to be complete as soil was allowed to dry. Detection of phenol as one of the degradation products revealed the occurrence of carbon–silicon bond cleavage promoted by soil.     

Sedimentary Processes of the Qingdao Nearshore Traced Using a Multi-radionuclide Approach

Sediment cores were collected from two sites (A2 and ZQ) in the Qingdao sea area of the Yellow Sea. Radionuclides ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁴Th, and ²³⁸U in the cores were measured using HPGe γ spectrometry. The sedimentation rate of the A2 Core using ²¹⁰Pb_ex and ¹³⁷Cs was 0.665 cm yr⁻¹, therefore this 32 cm long core represents a 48 year timespan leading to the sampling date in 2001. The mixing layer was restricted to the upper 5 cm as determined from the profile of ²³⁴Th. The uniformity of the activity distributions of ⁴⁰K and ²³⁸U throughout the A2 Core and the activity distributions of ²²⁶Ra, ²²⁸Ra and ²²⁸Th below the mixing layer suggested that no significant oceanographic event or change in sediment material source had occurred during this timespan. The ²¹⁰ Pb was in excess relative to ²²⁶Ra, but ²²⁶Ra was deficient with respect to ²³⁸U in the entire A2 Core, while excess ²³⁴Th and ²²⁸Th were apparent only in the surface 5 cm. Total organic matter (TOM) in Core A2 decreases with depth. The second core, taken to a depth of 14 cm, was from Site ZQ, which is located near Zhanqiao, Qingdao. The variations of the nuclide activity ratios in this core were similar to those in the A2 Core, i.e., the excess ²¹⁰ Pb and ²²⁶Ra deficiency were consistent throughout the core but excess ²²⁸Th was only in the surface to a depth of 2 cm. The ⁴⁰K activity in the ZQ Core fluctuated and showed no real trend with depth. The activities of ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra and ²³⁸U in the entire length of Core ZQ, and ²²⁸Ra and ²²⁸Th from 2 cm to the bottom, were comparable within the uncertainty of measured activity.     

Emissions of ammonia and greenhouse gases during combined pre-composting and vermicomposting of duck manure

Combined pre-composting and vermicomposting has shown potential for reclamation of solid wastes, which is a significant source of ammonia (NH₃), and greenhouse gases (GHG), including nitrous oxide (N₂O), methane (CH₄), and carbon dioxide (CO₂). Earthworms and amendments may both affect physico-chemical characteristics that control gas-producing processes, and thus affect NH₃ and GHG emissions. Here, we used two-way ANOVA to test the effects of addition of reed straw and combined addition of reed straw and zeolite on NH₃ and GHG emissions during pre-composting of duck manure, either with or without a follow-up phase of vermicomposting. Results showed that cumulative N₂O, CH₄, and CO₂ emissions during pre-composting and vermicomposting ranged from 92.8, 5.8, and 260.6 mg kg^?1 DM to 274.2, 30.4, and 314.0 mg kg^?1 DM, respectively. Earthworms and amendments significantly decreased N₂O and CH₄ emissions. Emission of CO₂ was not affected by earthworms, but increased in responses to addition of reed straw. Cumulative NH₃ emission ranged from 3.0 to 8.1 g kg^?1 DM, and was significantly decreased by reed straw and zeolite addition. In conclusion, combined pre-composting and vermicomposting with reed straw and zeolite addition would be strongly recommended in mitigating emissions of N₂O, CH₄, and NH₃ from duck manure. Moreover, this method also provides nutrient-rich products that can be used as a fertilizer.     

Municipal solid waste characteristics and management in Gümüşhane, Turkey

This paper presents a general overview of the current municipal solid waste (MSW) management in Gümüşhane Province, Turkey. In order to characterize the solid waste stream in the Municipality of Gümüşhane, a long-term study was conducted over a 52-week period between the spring of 2004 and the winter of 2005. In this study, percentage of components and specific weight of the MSW, the composting parameters (moisture content, total organic carbon, total nitrogen and pH), organic matter content, calorific value and the heavy metal concentrations (Cd, Cr, Cu, Ni, Pb, Zn, Fe, Mn, Co) of the compostable wastes sorted from the mixed MSW were determined and evaluated. In Gümüşhane, a mean of 70 tons of MSW are generated each day or 1 kg/day/capita. Approximately 4500 kg of the MSW were collected and sorted in a year, and the mean specific weight of these is 308 kg/m³. Approximately 30% of the MSW generated is compostable wastes and the yearly mean moisture content, organic matter content, C/N ratio and pH of these are 78%, 92.1%, 21.6/1 and 4.73, respectively, and approximately 24% of the MSW consists of recyclable materials. The recommended system deals with maximizing recycling and minimizing landfilling of the MSW, and consists of separation at source, collection, sorting, recycling, composting and sanitary landfilling. Heavy metal concentrations of the compostable wastes from the open dump were determined to decrease in the following order: Fe > Mn > Zn > Cr > Cu > Pb > Ni > Cd > Co.     

Estimation of transport parameters of phenolic compounds and inorganic contaminants through composite landfill liners using one-dimensional mass transport model

One-dimensional (1D) advection–dispersion transport modeling was conducted as a conceptual approach for the estimation of the transport parameters of fourteen different phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and three different inorganic contaminants (Cu, Zn, Fe) migrating downward through the several liner systems. Four identical pilot-scale landfill reactors (0.25 m³) with different composite liners (R1: 0.10 + 0.10 m of compacted clay liner (CCL), L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R2: 0.002-m-thick damaged high-density polyethylene (HDPE) geomembrane overlying 0.10 + 0.10 m of CCL, L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R3: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick bentonite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 1 × 10⁻⁸ m/s, R4: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick zeolite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 4.24 × 10⁻⁷ m/s) were simultaneously run for a period of about 540 days to investigate the nature of diffusive and advective transport of the selected organic and inorganic contaminants. The results of 1D transport model showed that the highest molecular diffusion coefficients, ranging from 4.77 × 10⁻¹⁰ to 10.67 × 10⁻¹⁰ m²/s, were estimated for phenol (R4), 2-MP (R1), 2,4-DNP (R2), 2,4-DCP (R1), 2,6-DCP (R2), 2,4,5-TCP (R2) and 2,3,4,6-TeCP (R1). For all reactors, dispersion coefficients of Cu, ranging from 3.47 × 10⁻⁶ m²/s to 5.37 × 10⁻² m²/s, was determined to be higher than others obtained for Zn and Fe. Average molecular diffusion coefficients of phenolic compounds were estimated to be about 5.64 × 10⁻¹⁰ m²/s, 5.37 × 10⁻¹⁰ m²/s, 2.69 × 10⁻¹⁰ m²/s and 3.29 × 10⁻¹⁰ m²/s for R1, R2, R3 and R4 systems, respectively. The findings of this study clearly indicated that about 35–50% of transport of phenolic compounds to the groundwater is believed to be prevented with the use of zeolite and bentonite materials in landfill liner systems.     

Study of nitrogen oxide absorption in the calcium sulfite slurry

Experiments were conducted using a bubbling reactor to investigate nitrogen oxide absorption in the calcium sulfite slurry. The effects of CaSO₃ concentration, NO₂/NO mole ratio and O₂ concentrations on NO₂ and SO₂ absorption efficiencies were investigated. Five types of additives, including MgSO₄, Na₂SO₄, FeSO₄, MgSO₄/Na₂SO₄ and FeSO₄/Na₂SO₄, had been evaluated for enhancing NO₂ absorption in CaSO₃ slurry. Results showed that CaSO₃ concentration had significant impact on NO₂ and SO₂ absorption efficiencies, and the highest absorption efficiencies of SO₂ and NO₂ could reach about 99.5 and 75.0 %, respectively. Furthermore, the NO₂ absorption was closely related to the NO₂/NO mole ratio, and the existence of NO₂ in flue gas may promote NO absorption. The presence of O₂ in simulated flue gas was disadvantage for NO _x removal because it can oxidize sulfite to sulfate. It was worth pointing out that FeSO₄/Na₂SO₄ was the best additive among those investigated additives, as the NO₂ removal efficiency was significantly increased from 74.8 to 95.0 %. IC and in situ FTIR results suggest that the main products were NO₃ ^? and NO₂ ^? in liquid phase and N₂O, N₂O₅ and HNO₃ in gas phase during the CaSO₃ absorption process.     

Comparison of PM2.5 and PM10 in A Suburban Area in Korea During April, 2003

Airborne particulate matter (PM) concentrations were measured in Iksan, a suburban area in South Korea during April, 2003. PM_2.5 (particles with an aerodynamic diameter less than 2.5 μm) and PM₁₀ (particles with an aerodynamic diameter less than 10 μm) samples were collected, and the chemical characteristics of particles were examined for diurnal patterns, yellow dust/rainfall influences, and scavenging effects. Average concentrations of PM_2.5 and PM₁₀ mass measured were 37.3 ± 16.2 μg m⁻³ and 60.8 ± 29.5 μg m⁻³, respectively. The sum of ionic chemical species concentrations for PM_2.5 and PM₁₀ was 16.9 ± 7.3 and 23.1 ± 10.1 μg/m³, respectively. A significant reduction in PM mass concentrations during rainfall days was observed for coarse mode (PM_{2.5 − 10}) particles, but less reduction was found for fine (PM_2.5) mass concentration. SO₄ ²⁻, NH₄ ⁺, and K⁺ predominated in fine particulate mode, NO₃ ⁻ and Cl⁻ predominated in fine particle mode and coarse particle mode, but Na⁺, Mg²⁺, and Ca²⁺ mostly existed in coarse mode. The high concentration of ammonium due to local emissions and long-range transport neutralized sulfate and nitrate to ammonium sulfate and ammonium nitrate, which were major forms of airborne PM in Iksan. Average mass concentrations of PM₁₀ in daytime and at night were 57.6 and 70.0 μg m⁻³, and those of PM_2.5 were 35.4 and 42.5 μg m⁻³, respectively. NO₃ ⁻ and Cl⁻ in both PM_2.5 and PM₁₀ were about double at night than in the daytime, while the rest of the chemical species were equal or a little higher at night than in the daytime. The results suggest the formation of ammonium nitrate and chloride when high ammonia concentration and low air temperature are allowed. Backward air trajectory analyses showed that air masses arriving at the site during yellow dust period were transported from arid Chinese regions, which resulted in high concentrations of airborne PM mass concentrations. In the meantime, air mass trajectories during a rainfall period were mostly from the Pacific Ocean or the East China Sea, along with a relatively low PM concentration.     

Diversity of bacterial isolates during full scale rotary drum composting

Bacterial diversity of full scale rotary drum composter from biodegradable organic waste samples were analyzed through two different approaches, i.e., Culture dependent and independent techniques. Culture-dependent enumerations for indigenous population of bacterial isolates mainly total heterotrophic bacteria (Bacillus species, Pseudomonas species and Enterobacter species), Fecal Coliforms, Fecal Streptococci, Escherichia coli, Salmonella species and Shigella species showed reduction during the composting period. On the other hand, Culture-independent method using PCR amplification of specific 16S rRNA sequences identified the presence of Acinetobacter species, Actinobacteria species, Bacillus species, Clostridium species, Hydrogenophaga species, Butyrivibrio species, Pedobacter species, Empedobactor species and Flavobacterium species by sequences clustering in the phylogenetic tree. Furthermore, correlating physico-chemical analysis of samples with bacterial diversity revealed the bacterial communities have undergone changes, possibly linked to the variations in temperature and availability of new metabolic substrates while decomposing organics at different stages of composting.     

Reclaiming the spent alkaline zinc manganese dioxide batteries collected from the manufacturers to prepare valuable electrolytic zinc and LiNi0.5Mn1.5O4 materials

A process for reclaiming the materials in spent alkaline zinc manganese dioxide (Zn–Mn) batteries collected from the manufacturers to prepare valuable electrolytic zinc and LiNi_0.5Mn_1.5O₄ materials is presented. After dismantling battery cans, the iron cans, covers, electric rods, organic separator, label, sealing materials, and electrolyte are separated through the washing, magnetic separation, filtrating, and sieving operations. Then, the powder residues react with H₂SO₄ (2 mol L^?1) solution to dissolve zinc under a liquid/solid ratio of 3:1 at room temperature, and subsequently, the electrolytic Zn with purity of ?99.8% is recovered in an electrolytic cell with a cathode efficiency of ?85% under the conditions of 37–40 °C and 300 A m^?2. The most of MnO₂ and a small quantity of electrolytic MnO₂ are recovered from the filtration residue and the electrodeposit on the anode of electrolytic cell, respectively. The recovered manganese oxides are used to synthesize LiNi_0.5Mn_1.5O₄ material of lithium-ion battery. The as-synthesized LiNi_0.5Mn_1.5O₄ discharges 118.3 mAh g^?1 capacity and 4.7 V voltage plateau, which is comparable to the sample synthesized using commercial electrolytic MnO₂. This process can recover the substances in the spent Zn–Mn batteries and innocuously treat the wastewaters, indicating that it is environmentally acceptable and applicable.     

Desulfurization of coke oven gas from the coking of coking coal blended with a sorbent and waste plastic

A new way to implement the simultaneous reutilization of solid waste, the desulfurization of coke oven gas (COG), and even the desulfurization of coke by the co-coking of coking coal (CC) and waste plastic (WP) blended with a sorbent is proposed; the evolution of H₂S and the removal efficiency of H₂S from COG during the co-coking process were investigated in a lab-scale cylindrical reactor. The experimental results indicated that for the coking of CC blended with ZnO, Fe₂O₃, or blast furnace dust (BFD) as a sorbent, the instantaneous concentration of H₂S in COG was lower than 500 mg/m³ (which meets the technical specification requirement of the Chinese Cleaner Production Standard–Coking Industry, HJ/T 126-2003) when the molar ratio between the key component of the sorbent and the volatile S in CC or the CC/WP blend, n _Zn+Fe/n _S, was about 1.2 for ZnO and Fe₂O₃, but not for BFD under the same conditions, suggesting that ZnO and Fe₂O₃ are promising sorbents, but that BFD must be treated chemical or thermally before being used as a sorbent because of the size and complicated nature of the influence of its phase/chemical composition on its desulfurization ability. However, for the co-coking of CC and WP blended with ZnO as a sorbent, n _Zn+Fe/n _S must increase to 1.4 and 1.7 for 100/2 and 100/5 blends of CC/WP, respectively, to ensure a satisfactory efficiency for H₂S removal from COG. Part of this paper was presented at the International Symposium on EcoTopia Science 2005 (ISET05), Aug 8–9, 2005, Chikusa-ku, Nagoya, Japan     

Limits and dynamics of methane oxidation in landfill cover soils

In order to understand the limits and dynamics of methane (CH₄) oxidation in landfill cover soils, we investigated CH₄ oxidation in daily, intermediate, and final cover soils from two California landfills as a function of temperature, soil moisture and CO₂ concentration. The results indicate a significant difference between the observed soil CH₄ oxidation at field sampled conditions compared to optimum conditions achieved through pre-incubation (60 days) in the presence of CH₄ (50 ml l⁻¹) and soil moisture optimization. This pre-incubation period normalized CH₄ oxidation rates to within the same order of magnitude (112-644 μg CH₄ g⁻¹ day⁻¹) for all the cover soils samples examined, as opposed to the four orders of magnitude variation in the soil CH₄ oxidation rates without this pre-incubation (0.9-277 μg CH₄ g⁻¹ day⁻¹).Using pre-incubated soils, a minimum soil moisture potential threshold for CH₄ oxidation activity was estimated at 1500 kPa, which is the soil wilting point. From the laboratory incubations, 50% of the oxidation capacity was inhibited at soil moisture potential drier than 700 kPa and optimum oxidation activity was typical observed at 50 kPa, which is just slightly drier than field capacity (33 kPa). At the extreme temperatures for CH₄ oxidation activity, this minimum moisture potential threshold decreased (300 kPa for temperatures <5 °C and 50 kPa for temperatures >40 °C), indicating the requirement for more easily available soil water. However, oxidation rates at these extreme temperatures were less than 10% of the rate observed at more optimum temperatures (∼30 °C). For temperatures from 5 to 40 °C, the rate of CH₄ oxidation was not limited by moisture potentials between 0 (saturated) and 50 kPa. The use of soil moisture potential normalizes soil variability (e.g. soil texture and organic matter content) with respect to the effect of soil moisture on methanotroph activity. The results of this study indicate that the wilting point is the lower moisture threshold for CH₄ oxidation activity and optimum moisture potential is close to field capacity.No inhibitory effects of elevated CO₂ soil gas concentrations were observed on CH₄ oxidation rates. However, significant differences were observed for diurnal temperature fluctuations compared to thermally equivalent daily isothermal incubations.     

Environmentally-Friendly Synthesis of Ag Nanoparticles by Fusarium sporotrichioides for the Production of PVA/Bentonite/Ag Composite Nanofibers

Membranes and filters made of nanofibers can have many medicines and water treatment applications. The use of silver nanoparticles (AgNPs) with antibacterial activity in these structures improve their efficiency. However, due to the toxicity of the compounds used in the chemical synthesis of AgNPs, in this study, AgNPs were obtained through a biological process using Fusarium sporotrichioides. AgNPs preparation conditions were optimized, including F. sporotrichioides medium and AgNO₃ concentration. Next, a PVA nanofiber membrane with bentonite and AgNPs (Bio-AgNPs or Chem-AgNPs) was prepared using electrospinning. The optimal conditions for the production of Bio-AgNPs were the culture of F. sporotrichioides in the MGYP culture medium and 12 M of AgNO₃. The Bio-AgNPs particle size and zeta potential were 58 nm and ??16.8 mV, respectively, with antibacterial activity. The PVA/NB/AgNPs nanofibers operation conditions included 7.5% w/w PVA, 3% w/w bentonite, and AgNPs 5% w/w at a voltage of 11 kV, feed rate of 0.5 mL/h, and 15 cm distance between the needle and the collector. The average diameter of the PVA/NB/Bio-AgNPs nanofibers was 230 nm. Also, the presence of silver in the nanofibers was confirmed through EDX and XRD methods. The antibacterial assay of the nanofibers showed that the inhibition zone of PVA/NB/Bio-AgNPs against E. coli and S. aureus was 0.62 and 0.36 mm, which is better than PVA/NB/Chem-AgNPs and comparable with chloramphenicol. The produced membrane is suitable for water treatment, food packaging, and wound dressing because of its good thermal, mechanical, and antibacterial properties.

     

Effects of Acid Rain on Competitive Releases of Cd, Cu, and Zn from Two Natural Soils and Two Contaminated Soils in Hunan, China

Leaching experiments of rebuilt soil columns with two simulated acid rain solutions (pH 4.6–3.8) were conducted for two natural soils and two artificial contaminated soils from Hunan, south-central China, to study effects of acid rain on competitive releases of soil Cd, Cu, and Zn. Distilled water was used in comparison. The results showed that the total releases were Zn>Cu>Cd for the natural soils and Cd>Zn≫Cu for the contaminated soils, which reflected sensitivity of these metals to acid rain. Leached with different acid rain, about 26–76% of external Cd and 11–68% external Zn were released, but more than 99% of external Cu was adsorbed by the soils, and therefore Cu had a different sorption and desorption pattern from Cd and Zn. Metal releases were obviously correlated with releases of TOC in the leachates, which could be described as an exponential equation. Compared with the natural soils, acid rain not only led to changes in total metal contents, but also in metal fraction distributions in the contaminated soils. More acidified soils had a lower sorption capacity to metals, mostly related to soil properties such as pH, organic matter, soil particles, adsorbed SO₄ ²⁻, exchangeable Al³⁺ and H⁺, and contents of Fe₂O₃ and Al₂O₃.     

Furniture wood wastes: Experimental property characterisation and burning tests

Referring to the industrial wood waste category (as dominant in the provincial district of Pesaro-Urbino, Marche Region, Italy), this paper deals with the experimental characterisation and the carrying out of non-controlled burning tests (at lab- and pilot-scale) for selected “raw” and primarily “engineered” (“composite”) wood wastes.The property characterisation has primarily revealed the following aspects: potential influence on moisture content of local weather conditions at outdoor wood waste storage sites; generally, higher ash contents in “engineered” wood wastes as compared with “raw” wood wastes; and relatively high energy content values of “engineered” wood wastes (ranging on the whole from 3675 to 5105 kcal kg⁻¹ for HHV, and from 3304 to 4634 kcal kg⁻¹ for LHV).The smoke qualitative analysis of non-controlled lab-scale burning tests has primarily revealed: the presence of specific organic compounds indicative of incomplete wood combustion; the presence exclusively in “engineered” wood burning tests of pyrroles and amines, as well as the additional presence (as compared with “raw” wood burning) of further phenolic and containing nitrogen compounds; and the potential environmental impact of incomplete industrial wood burning on the photochemical smog phenomenon.Finally, non-controlled pilot-scale burning tests have primarily given the following findings: emission presence of carbon monoxide indicative of incomplete wood combustion; higher nitrogen oxide emission values detected in “engineered” wood burning tests as compared with “raw” wood burning test; and considerable generation of the respirable PM₁ fraction during incomplete industrial wood burning.     

Nitrogen Budget of a Spruce Forest Ecosystem After Six-year Addition of Ammonium Sulphate in Southwest Sweden

A nitrogen (N) budget was constructed for a period of 6 years (1988–1993) in a Norway spruce stand with current deposition of 19 kg N and 22 kg S ha⁻¹ year⁻¹. The stand was fertilized annually by addition of 100 kg N and 114 kg S ha⁻¹ (NS). Above and below ground biomass, litterfall, fine- root litter production, soil solution and net mineralization were measured to estimate pools, fluxes and accumulation of nitrogen. The average needle litterfall in control (C) and NS plots in 1993 was 2.2 and 2.5 ton ha⁻¹ year⁻¹, respectively. The fine root litter production prior to treatment (1987) was 4.4 ton ha⁻¹ year⁻¹ and after treatment (1993) it was 4.5 and 3.9 ton ha⁻¹ year⁻¹ in C and NS plots, respectively. Net N mineralization in the soil profile down to 50 cm was estimated to be 86 and 115 kg ha⁻¹ year⁻¹ in C and NS plots, respectively in 1992. During the treatment period the uptake of N in the needle biomass in C and NS plots was 29 and 77 kg ha⁻¹ year⁻¹, respectively. No N was accumulated in needles of C plot where the NS plots accumulated 34 kg ha⁻¹ year⁻¹. Of the annually added inorganic N to NS plots 47% was accumulated in the above and below ground biomass and 37% in the soil. N fluxes via fine-root litter production in the C plots were much higher (54 kg ha⁻¹ year⁻¹) than that via litterfall (29 kg ha⁻¹ year⁻¹). The corresponding values in the NS plots were 65 and 43 kg ha⁻¹ year⁻¹, respectively. Most of the net N mineralization occurred in the FH layer and upper mineral soil. It is concluded that fine root litter and litterfall play an important role in the cycling of N. Despite a high N uptake the losses of N in litterfall and fine root litter resulted in an incorporation of N in soil organic matter.     

Fertilizer and sanitary quality of digestate biofertilizer from the co-digestion of food waste and human excreta

This research was aimed at assessing the fertilizer quality and public health implications of using digestate biofertilizer from the anaerobic digestion of food wastes and human excreta. Twelve (12) kg of food wastes and 3 kg of human excreta were mixed with water in a 1:1 w/v to make 30-l slurry that was fed into the anaerobic digester to ferment for 60 days at mesophilic temperature (22–31 °C). Though BOD, COD, organic carbon and ash content in the feedstock were reduced after anaerobic digestion by 50.0%, 10.6%, 74.3% and 1.5% respectively, nitrogen, pH and total solids however increased by 12.1%, 42.5% and 12.4% respectively. The C/N ratios of the feedstock and compost are 135:1 and 15.8:1. The residual total coliforms of 2.10 × 10⁸ CFU/100 ml in the digestate was above tolerable limits for direct application on farmlands. Microbial analysis of the digestate biofertilizer revealed the presence of Pseudomonas, Klebsiella, Clostridium, Bacillus, Bacteroides, Penicillum, Salmollena, and Aspergillus. Klebsiella, Bacillus, Pseudomonas, Penicillum and Aspergillus can boost the efficiency of the biofertilizer through nitrogen fixation and nutrient solubility in soils but Klebsiella again and Salmollena are potential health risks to end users. Further treatment of the digestate for more efficient destruction of pathogens is advised.