RESUMEN
Antibiotic production wastewater usually contains high concentrations of antibiotic residues, which can cause instability and deterioration of biological wastewater treatment units and also domestication and proliferation of antibiotic-resistance bacteria. An effective pretreatment on antibiotics production wastewater is expected to selectively reduce the concentration of antibiotics and decrease the toxicity, rather than mitigate organic and other contaminants before further treatments. In this work, two polymer-based solid acids, PS-S and CPS-S bearing high concentrations of -SOH3 groups (up to 4.57 mmol/g), were prepared and successfully used for hydrolytic mitigation of 100 mg/L tylosin within 20 min. The co-existence of high concentrations of COD and humic substances did not affect the mitigation of tylosin obviously, while more than 500 mg/L of nitrogenous compounds suppressed the hydrolytic efficiency. Recycle and reuse experiments showed that the solid acids performed well in five cycles after regeneration. Three transformation products (P1, P2 and P3) were identified using UPLC-QTOF-MS/MS. Sugar moieties including mycarse, mycaminose, and mycinose detached and released simultaneously or in order from the 16-member lactone ring through desugarization, which led to a dramatic decrease in antibacterial activity as revealed by cytotoxicity evaluations using S. aureus. Ecotoxicity estimation indicated the acute toxicities of the hydrolyzed products to model species (e.g., fish, daphnid and green algae) were classified as "not harmful". This work suggested an effective and selective method to pretreat tylosin-contained production wastewater by using polymer-based solid acids. These results will shed light on effective elimination of antibiotics pollution from pharmaceutical industries through strengthening the pretreatments.
Asunto(s)
Poliestirenos , Tilosina , Animales , Tilosina/toxicidad , Aguas Residuales , Polímeros , Staphylococcus aureus , Espectrometría de Masas en Tándem , Antibacterianos/toxicidadRESUMEN
It becomes common to wear a disposable face mask to protect from coronavirus disease 19 (COVID-19) amid this pandemic. However, massive generations of contaminated face mask cause environmental concerns because current disposal processes (i.e., incineration and reclamation) for them release toxic chemicals. The disposable mask is made of different compounds, making it hard to be recycled. In this regard, this work suggests an environmentally benign disposal process, simultaneously achieving the production of valuable fuels from the face mask. To this end, CO2-assisted thermo-chemical process was conducted. The first part of this work determined the major chemical constituents of a disposable mask: polypropylene, polyethylene, nylon, and Fe. In the second part, pyrolysis study was employed to produce syngas and C1-2 hydrocarbons (HCs) from the disposable mask. To enhance syngas and C1-2 HCs formations, multi-stage pyrolysis was used for more C-C and C-H bonds scissions of the disposable mask. Catalytic pyrolysis over Ni/SiO2 further expedited H2 and CH4 formations due to its capability for dehydrogenation. In the presence of CO2, catalytic pyrolysis additionally produced CO, while pyrolysis in N2 did not produce it. Therefore, the thermo-chemical conversion of disposable face mask and CO2 could be an environmentally benign way to remove COVID-19 plastic waste, generating value-added products.
RESUMEN
Biochar has been recognized as a sustainable platform for developing functional materials including catalysts. This work demonstrated a method of converting biochar to sulfonated solid-acid catalysts, and the effectiveness of the catalysts for spiramycin hydrolysis was examined. Two biochar samples (H and X) were sulfonated with three reagents (concentrated H2SO4, ClSO3H and p-toluenesulfonic acid (TsOH)) under hydrothermal, simple heating, ambient temperature, and CHCl3-assisted treatments. The effect of elemental compositions and structural characteristics of the feeding materials (H and X) on the acidic properties of the sulfonated biochars were investigated. The results showed that the sulfonation ability of the three reagents was in the order of ClSO3H > H2SO4 > TsOH, while hydrothermal treatment provided the highest total acidity, and largest amount of acidic groups (e.g., SO3H, COOH and Ar-OH). Biochar X with higher O/C and N contents, and less graphitic features showed superior acidic properties than biochar H under all the employed treatments. The hydrolytic efficiencies of the sulfonated biochars under 200 W of microwave irradiation increased with increasing total acidity, and the amount of SO3H and COOH groups. After sulfonation, the O/C of biochars increased, while H/C decreased, and the aromatic and graphitic features did not change. The electromagnetic energy absorbed by the sulfonated biochars did not notably contribute to spiramycin hydrolysis. Thus, this work demonstrated an effective and promising method for maneuvering biochar-based functional solid-acid catalysts for antibiotic remediation in contaminated water.
Asunto(s)
Espiramicina , Catálisis , Carbón Orgánico , HidrólisisRESUMEN
The precipitation of struvite (MgNH4PO4·6H2O) consumes many chemicals to completely remove ammonium and phosphate from urine and has the difficulty in solid separation from solution. This study proposed an alternative approach for the complete nutrient removal through recycling use of microwave-induced decomposition product of struvite pellet with sizes of 2-4 mm. Results showed that microwave radiation effectively decomposed the struvite pellet in an alkaline solution within 8 min. An increase in microwave power and NaOH concentration enhanced the decomposition. The double-layer structure of the pellet led to multiple paths of struvite decomposition. Active components of the decomposition product were newberyite, brucite, and amorphous MgNaPO4 and MgHPO4. The removal efficiencies of ammonium and phosphate from urine both reached 93% using the decomposition product at optimized P/N ratio and pH. Maximum recycles of 4 were recommended because further decomposition of the regenerated struvite pellets induced high losses of magnesium and phosphate. Calculations showed that the total cost of chemical consumption of the proposed approach was reduced by 47% compared with that of a conventional chemical struvite precipitation. Moreover, the volume index of the regenerated struvite pellets was 15 mL/gP which was much lower than that of conventional struvite fines (116 mL/gP), thereby indicating a better solid-liquid separation ability. Therefore, recycling of struvite pellets combining with microwave decomposition was chemical saving and easily separating of solid from liquid for the complete removal of nutrients from urine.
Asunto(s)
Compuestos de Amonio , Microondas , Fosfatos , Reciclaje , Estruvita , Eliminación de Residuos LíquidosRESUMEN
Excessive nitrate (NO3-) is among the most problematic surface water and groundwater pollutants. In this study, a type of magnetic cationic hydrogel (MCH) is employed for NO3- adsorption and well characterized herein. Its adsorption capacity is considerably pH-dependent and achieves the optimal adsorption (maximum NO3--adsorption capacity is 95.88 ± 1.24 mg/g) when the pH level is 5.2-8.8. The fitting result using the homogeneous surface diffusion model indicates that the surface/film diffusion controls the adsorption rate, and NO3- approaches the center of MCH particles within 30 min. The diffusion coefficient (Ds) and external mass transfer coefficient (kF) in the liquid phase are 1.15 × 10-6 cm2/min and 4.5 × 10-6 cm/min, respectively. The MCH is employed to treat surface water that contains 10 mg/L of NO3-, and it is found that the optimal magnetic separation time is 1.6 min. The high-efficiency mass transfer and magnetic separation of MCH during the adsorption-regeneration process favors its application in surface water treatment. Furthermore, the study of the mechanism involved reveals that both -N+(CH3)3 groups and NO3- are convoluted in adsorption via electrostatic interactions. It is further found that ion exchange between NO3- and chlorine occurs.
Asunto(s)
Contaminantes Químicos del Agua , Purificación del Agua , Adsorción , Hidrogeles , Concentración de Iones de Hidrógeno , Cinética , Nitratos , SolucionesRESUMEN
A novel polycyclodextrin-modified magnetic cationic hydrogel (PCD-MCH) was developed and its performance, kinetics and mechanism for the removal of reactive brilliant red X-3B (X-3B) were studied. The results showed that the zeta-potential of PCD-MCH was 32.8 to 16.7mV at pH3.0-10.5. The maximum X-3B adsorption capacity of PCD-MCH was 2792.3mg/g. The adsorption kinetics could be well-described by the Weber-Morris model and the homogeneous surface diffusion model (HSDM). Diffusion stages corresponding to surface or film diffusion, intra-particle or wide mesopore diffusion, and narrow mesopore/micropore diffusion occurred at 0-120, 120-480 and 480-1200min, respectively. The latter two diffusion stages were rate-controlling for X-3B adsorption kinetics. At the initial X-3B concentration of 600mg/L, the diffusion coefficient (Ds) and external mass transfer coefficient in the liquid phase (kF) were 3×10-11cm2/min and 4.68×10-6cm/min, respectively. X-3B approaching the center of PCD-MCH particles could be observed at 360min. At the end of the third diffusion stage, the Cp at q/qe=0 was 45.20mg/L, which was close to the homogeneous Cp value of 46mg/L along the radius of PCD-MCH particles. At pH3.0-10.0, PCD-MCH showed stable X-3B adsorption capacities. After five regeneration-reuse cycles, the residual adsorption capacity of regenerated PCD-MCH was higher than 892.7mg/g. The corresponding adsorption mechanism was identified as involving electrostatic interactions, cyclodextrin cavities and hydrogen bonds, of which cyclodextrin cavities showed prominent capture performance towards dye molecules through the formation of inclusion complexes.
Asunto(s)
Colorantes/química , Hidrogeles/química , Contaminantes Químicos del Agua , Purificación del Agua/métodos , Adsorción , Cationes , Ciclodextrinas/química , Concentración de Iones de Hidrógeno , Cinética , Fenómenos MagnéticosRESUMEN
Carbon dot- and magnetite-modified magnetic carbon nanotubes (CMNTs) were synthesized and evaluated for carbamazepine removal from water. The adsorbent was characterized by multiple modern surface and microstructure analyzing techniques. CMNTs were composed of three components including carbon dots (CDs), carbon nanotubes (CNTs) and magnetite. CDs and CNTs introduce abundant carboxyl groups onto CMNTs and magnetite allows rapid magnetic separation of the adsorbent realizable after batch adsorption. This adsorbent has a moderately high adsorption capacity of 65â¯mg-carbamazepine/g-adsorbent at pH 7.0⯱â¯0.2, which is superior to many reported adsorbents. Carbamazepine was uptaken well in a wide pH range, regardless of the surface charging of CMNTs. Its adsorption on CMNTs was quite fast and reached 80% of removal during the initial 3â¯h. The mass transfer within CMNTs and the time-dependent utilization, exhaustion and depletion of the adsorption capacity were successfully described using a simplified homogeneous surface diffusion model (HSDM). The surface diffusion coefficients (Ds) rose with increasing initial carbamazepine concentrations. After six regeneration and recycle experiments, the capacity loss of CMNTs was less than 2.2% at the conditions tested. FTIR spectra showed the characteristics of the components. Raman spectra implied a π-π electron donor-acceptor (EDA) interaction during adsorption. This work proposed a method of combining π-bond-rich materials (CNTs and CDs) and magnetite to make separable composite adsorbents with high affinity interactions between carbamazepine and carbon materials. The prepared adsorbent is attractive for carbamazepine removal due to its good performance, moderate cost, ease of separation, and ability to regenerate.
Asunto(s)
Carbamazepina/análisis , Nanotubos de Carbono , Contaminantes Químicos del Agua , Purificación del Agua , Adsorción , Fenómenos Magnéticos , AguaRESUMEN
Breaking down the structural bonds and eliminating the functional groups are more efficient than destroying the whole molecule in antibiotic production wastewater (APW) pretreatment before further biotreatment. Two sulfated titania (TiO2/SO4) solid superacids, SSA1 and SSA2 were synthesized, characterized and used for hydrolytic pretreatment of spiramycin in APW. Spiramycin removal followed an order of SSA2>SSA1>TiO2≈pHâ¯=â¯3>control. The hydrolytic efficiencies increased at elevated temperature from 25⯰C to 65⯰C. The hydrolytic kinetics followed a first-order model and SSA2 performed the fastest. The performances were positively correlated with both the total acidity determined by n-butylamine titration and the strength of acid sites measured by NH3-temperature-programmed desorption (TPD). The residual solution for SSA2 presented the least antibacterial potency and anaerobic inhibition among all treatments. The hydrolyzed product was identified as the m/z 699.4321 fragment using UPLC-Q/TOF-MS, which was formed after losing a functional mycarose moiety from the parent molecular. The solid superacids were effective in selectively eliminating 433â¯mg/L of spiramycin and the antibacterial potencies of the spiramycin production wastewater, which contained very high concentrations of COD (33,000â¯mg/L). This hydrolytic method avoids using and handling hazardous and corrosive mineral acids on site. It is attractive as a selective catalytic pretreatment method to cleave antibiotics' functional groups and to reduce its inhibitory effects before sequential biotreatments.
Asunto(s)
Antibacterianos/química , Espiramicina/química , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/química , Antibacterianos/análisis , Catálisis , Hidrólisis , Espiramicina/análisis , Aguas Residuales , Contaminantes Químicos del Agua/análisisRESUMEN
A novel, cost-effective and real-time process monitoring and control system was developed to maintain stable operation of waste-to-energy gasification process. It comprised a feedback loop control that utilized the differential temperatures of the oxidation and reduction zones in the gasifier to determine the regional heat-flow (endothermic or exothermic), to assess the availability of oxidizing agent (for instance, air or O2) at the char bed and to calculate the fuel feeding rate. Based on the correlations developed, the air-to-fuel ratio or the equivalence air ratio (ER) for air gasification could be instantaneously adjusted to maintain stable operation of the gasifier. This study demonstrated a simplification of complex reaction dynamics in the gasification process to differential temperature profiling of the gasifier. The monitoring and control system was tested for more than 70â¯h of continuous operation in a downdraft fixed-bed gasifier with refuse-derived fuel (RDF) prepared from municipal solid wastes (MSW). With the system, fuel feeding rate could be adjusted accurately to stabilize the operating temperature and ER in the gasifier and generate syngas with consistent properties. Significant reductions in the fluctuations of temperature profiles at oxidation and reduction zones (from higher than 100⯰C to lower than 50⯰C), differential temperatures (from ±200 to ±50⯰C) in gasifier and the flow rate (from 16⯱â¯6.5 to 12⯱â¯1.8â¯L/min), composition of main gas components, LHV (from 6.2⯱â¯3.1 to 5.7⯱â¯1.6 MJ/Nm3) and tar content (from 8.0⯱â¯9.7 to 7.5⯱â¯4.2â¯g/Nm3) of syngas were demonstrated. The developed gasifier monitoring and control system is adaptable to various types (updraft, downdraft, and fluidized-bed) and scales (lab, pilot, large scale) of gasifiers with different types of fuel.
Asunto(s)
Residuos de Alimentos , Residuos Sólidos , Calor , TemperaturaRESUMEN
The recovery of phosphate from human urine has been considered as one of the most attractive benefits of urine source separation because P is an essential but limited macronutrient. This study investigated the approach to modify wood waste biochar via metal oxides aiming to recover phosphate from human urine to produce a value-added biochar. Results showed the phosphate removal ability was enhanced for the modified biochar pre-treated in modification solutions of MgCl2, AlCl3, CaCl2 and FeCl3, respectively, while natural biochar released phosphate to urine. Among the tested biochar, Mg-biochar presented the best capacity for phosphate removal from the hydrolyzed urine, reaching 118 mgP g-1 at a MgCl2 concentration of 2.3 M. However, higher MgCl2 concentration would not further increase the adsorption capacity. Fitting of the adsorption kinetics and isotherms indicated that the phosphate removal process was probably controlled by multiple mechanisms. Both the experimental and fitting results confirmed that the content of Mg oxides was the key factor determining the adsorption rate and capacity of phosphate on Mg-biochar. pH ranges of 7-9 and the ammonium concentration higher than 108 mgN L-1 enhanced the phosphate adsorption capacity. As such, the Mg-biochar was more favored for the treatment of hydrolyzed urine rather than fresh urine with acidic pH and lower concentration of ammonium. Further calculations were carried out using the Langmuir model to evaluate the removal of phosphate and the product. Results indicate that it is an effective technique to use Mg-biochar for phosphate removal from hydrolyzed urine and it yields phosphate-enriched biochar products.
Asunto(s)
Carbón Orgánico/química , Óxido de Magnesio/química , Fosfatos/aislamiento & purificación , Orina/química , Madera/química , Adsorción , Humanos , Concentración de Iones de Hidrógeno , Hidrólisis , Cinética , Metales/química , Modelos Teóricos , Óxidos/química , Fosfatos/química , ResiduosRESUMEN
The occurrence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) has been intensively investigated for wastewater treatment systems treating single class of antibiotic in recent years. However, the impacts of alternately occurring antibiotics in antibiotic production wastewater on the behavior of ARGs in biological treatment systems were not well understood yet. Herein, techniques including high-capacity quantitative PCR and quantitative PCR (qPCR) were used to investigate the behavior of ARGs in an anaerobic-aerobic full-scale system. The system alternately treated three kinds of antibiotic production wastewater including ribostamycin, spiramycin and paromomycin, which referred to stages 1, 2 and 3. The aminoglycoside ARGs (52.1-79.3%) determined using high-capacity quantitative PCR were the most abundant species in all sludge samples of the three stages. The total relative abundances of macrolide-lincosamide-streptogramin (MLS) resistance genes and aminoglycoside resistance genes measured using qPCR were significantly higher (P < 0.05) in aerobic sludge than in sewage sludge. However, the comparison of ARGs acquired from three alternate stages revealed that MLS genes and the aminoglycoside ARGs did not vary significantly (P > 0.05) in both aerobic and anaerobic sludge samples. In aerobic sludge, one acetyltransferase gene (aacA4) and the other three nucleotidyltransferase genes (aadB, aadA and aadE) exhibited positive correlations with intI1 (r 2 = 0.83-0.94; P < 0.05), implying the significance of horizontal transfer in their proliferation. These results and facts will be helpful to understand the abundance and distribution of ARGs from antibiotic production wastewater treatment systems.
Asunto(s)
Farmacorresistencia Microbiana/genética , Paromomicina/química , Ribostamicina/química , Espiramicina/química , Aguas Residuales/química , Aerobiosis , Anaerobiosis , Bacterias/efectos de los fármacos , Bacterias/genética , Transferencia de Gen Horizontal , Mutación , Paromomicina/farmacología , Reacción en Cadena de la Polimerasa , ARN Ribosómico 16S/genética , Ribostamicina/farmacología , Aguas del Alcantarillado , Espiramicina/farmacologíaRESUMEN
Limited mechanistic knowledge is available on the interaction of biochar with trace elements (Sb and As) that exist predominantly as oxoanions. Soybean stover biochars were produced at 300 °C (SBC300) and 700 °C (SBC700), and characterized by BET, Boehm titration, FT-IR, NMR and Raman spectroscopy. Bound protons were quantified by potentiometric titration, and two acidic sites were used to model biochar by the surface complexation modeling based on Boehm titration and NMR observations. The zero point of charge was observed at pH 7.20 and 7.75 for SBC300 and SBC700, respectively. Neither antimonate (Sb(V)) nor antimonite (Sb(III)) showed ionic strength dependency (0.1, 0.01 and 0.001 M NaNO3), indicating inner sphere complexation. Greater adsorption of Sb(III) and Sb(V) was observed for SBC300 having higher -OH content than SBC700. Sb(III) removal (85%) was greater than Sb(V) removal (68%). Maximum adsorption density for Sb(III) was calculated as 1.88 × 10(-6) mol m(-2). The Triple Layer Model (TLM) successfully described surface complexation of Sb onto soybean stover-derived biochar at pH 4-9, and suggested the formation of monodentate mononuclear and binuclear complexes. Spectroscopic investigations by Raman, FT-IR and XPS further confirmed strong chemisorptive binding of Sb to biochar surfaces.
Asunto(s)
Antimonio/química , Carbón Orgánico/química , Glycine max , Contaminantes del Suelo/química , Adsorción , Concentración Osmolar , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Ferric hydroxide (FHO), which has high phosphate adsorption capacity, was prepared by precipitation at industrial scale and then fabricated via the drum granulation method with cross-linked poly(vinyl alcohol) as the binder. The optimum binder/FHO powder ratio was 0.6 for producing a granular adsorbent with a high phosphate adsorption capacity and stability. The Langmuir maximum adsorption capacities of powder and granular FHOs were 74.07 mg g⻹ and 56.18 mg g(-1) at pH 7.0 ± 0.2, respectively, which were higher than those of other reported phosphate adsorbents under neutral or acidic conditions. Phosphate-loaded granular FHO could be regenerated by NaOH solution. Columns containing the granular FHO were used for phosphate removal from ozonated secondary effluents of a municipal wastewater treatment plant at space velocity (SV) of 2 and 5 h⻹. During more than 2 months' operation, the average removal percentage of PO(4)(3-) was more than 90% and the turbidity and concentration of CODMn in the effluents were lower than in the influents. In addition, energy dispersive X-ray results suggested that active sites inside the granular FHO were available for phosphate removal. The results demonstrated that granular FHO can be applied as an assist technology for phosphate removal from secondary effluents.
Asunto(s)
Compuestos Férricos/química , Fosfatos/metabolismo , Aguas Residuales/química , Contaminantes Químicos del Agua/metabolismo , Adsorción , Compuestos Férricos/metabolismo , Concentración de Iones de Hidrógeno , Microscopía Electrónica de Rastreo , Espectrofotometría Ultravioleta , Difracción de Rayos XRESUMEN
The impacts of microplastics on soil ecological functions such as carbon recycling and soil structure maintenance have been extensively focused. However, the mechanisms underlying the impacts of microplastics on soil carbon transformation and soil microbial community at soil aggregate scale have not been clarified yet. In this work, the effects and action mechanisms of traditional microplastic polypropylene (PP) and degradable microplastic polylactic acid (PLA) on carbon transformation in three sizes of soil aggregates were investigated. The results showed that both PP and PLA promoted CO2 emission, and the effect depended on the type and content of microplastics, and the size of soil aggregates. Changes in soil carbon stocks were mainly driven by changes in organic carbon associated with macroaggregates. For macroaggregates, PP microplastics decreased soil organic carbon (SOC) as well as dissolved organic carbon (DOC). These changes were reversed in microaggregates and silt and clay. Interestingly, PLA increased the SOC, DOC and CO2 emissions in bulk soil and all three aggregates with a dose-effect response. These changes were associated with soil microbes, functional genes and enzymes associated with the degradation of labile and recalcitrant carbon fractions. Furthermore, PP and PLA reduced bacterial community diversities and shifted bacterial community structures in both the three aggregates and in bulk soil. Alterations of functional genes induced by microplastics were the key driving factors of their impacts on carbon transformation in soil aggregates. This research opened up a new insight into the mechanisms underlying the impacts of microplastics on soil carbon transformation, and helped us make rational assessments of the risks and the disturbances of microplastics on soil carbon cycling.
RESUMEN
With exogenous nitrogen (N) input into soil, phosphorus (P) could become a limiting nutrient for plant growth. Soil microbes play a crucial role in regulating soil P cycle and availability. P functional genes, further, regulate soil P availability. It is unclear how the addition of N in different chemical forms and rates influences the composition of soil microbes associated with P cycling and the abundance of P functional genes. A long-term experiment of N addition in three chemical forms with two levels in a temperate forest was performed to reveal the influences and the underlying mechanisms. We found that both chemical N forms and N rates selected for different P-solubilizing microbes. Ammonia form-N increased the abundances of P-solubilizing bacteria at low and high rates. Continuous N deposition included a significant decrease in soil pH and inhibited the viability and activity of bacterial communities in soil, especially the P-solubilizing bacteria. Thus, it restricted inorganic P mobilization and led to a decrease in soil available P. In addition, ammonium-N enhanced the relative abundance of most of the functional genes related to organic P mineralization, while nitrate-N presented a decrease trend. Ammonium-N significantly decreased most of the functional genes relevant to P transportation, whereas the other chemical N forms did not change them. Although N-addition consistently decreased the functional genes relevant to inorganic P solubilization, two of them (ppx and ppa) were the exceptions and showed an increase trend. N addition also decreased soil pH and altered soil properties, and indirectly contributed to the changes in community composition of P-solubilizing microbes and the abundances of multiple P functional genes. Our results provide a mechanistic explanation for the regulation of microbes on N-induced available P limitation via tuning the compositions of P-solubilizing microbes and the abundances of multiple P functional genes.
Asunto(s)
Compuestos de Amonio , Suelo , Suelo/química , Microbiología del Suelo , Nitrógeno/análisis , Fósforo/metabolismo , Bosques , Bacterias/metabolismo , Compuestos de Amonio/metabolismoRESUMEN
Increases in soil available nitrogen (N) influence N-cycle gene abundances and emission of nitrous oxide (N2O), which is primarily due to N-induced soil acidification in forest. Moreover, the extent of microbial-N saturation could control microbial activity and N2O emission. The contributions of N-induced alterations of microbial-N saturation and N-cycle gene abundances to N2O emission have rarely been quantified. Here, the mechanism underlying N2O emission under N additions (three chemical forms of N, i.e., NO3--N, NH4+-N and NH4NO3-N, and each at two rates, 50 and 150 kg N ha-1 year-1, respectively) spanning 2011-2021 was investigated in a temperate forest in Beijing. Results showed N2O emissions increased at both low and high N rates of all the three forms compared with control during the whole experiment. However, N2O emissions were lower in high rate of NH4NO3-N and NH4+-N treatments than the corresponding low N rates in the recent three years. Effects of N on microbial-N saturation and abundances of N-cycle genes were dependent on the N rate and form as well as experimental time. Specifically, negative effects of N on N-cycle gene abundances and positive effects of N on microbial-N saturation were demonstrated in high N rate treatments, particularly with NH4+ addition during 2019-2021. Such effects were associated with soil acidification. A hump-backed trend between microbial-N saturation and N2O emissions was observed, suggesting N2O emissions decreased with increase of the microbial-N saturation. Furthermore, N-induced decreases in N-cycle gene abundances restrained N2O emissions. In particular, the nitrification process, dominated by ammonia-oxidize archaea, is critical to determination of N2O emissions in response to the N addition in the temperate forest. We confirmed N addition promoted soil microbial-N saturation and reduced N-cycle gene abundances, which restrained the continuous increase in N2O emissions. It is important for understanding the forest-N-microbe nexus under climate change.
Asunto(s)
Nitrógeno , Suelo , Nitrógeno/análisis , Microbiología del Suelo , Ciclo del Nitrógeno , Bosques , Óxido Nitroso/análisisRESUMEN
A Fe-Zr binary oxide adsorbent has been successfully synthesized using a co-precipitation method. It showed a better performance for antimonate (Sb(V)) removal than zirconium oxide or amorphous ferric oxide. The experimental results showed that the Fe-Zr adsorbent has a capacity of 51 mg/g at an initial Sb(V) concentration of 10 mg/L at pH 7.0. Sb(V) adsorption on the Fe-Zr bimetal oxide is normally an endothermic reaction. Most of the Sb(V) adsorption took place within 3 hr and followed a pseudo second-order rate law. Co-existing anions such as SO4(2-), NO3(-) and Cl(-) had no considerable effects on the Sb(V) removal; PO4(3-) had an inhibitory effect to some extent at high concentration; while CO3(2-) and SiO4(4-) showed significant inhibitory effects when they existed in high concentrations. The mechanism of Sb(V) adsorption on the adsorbent was investigated using a combination of zeta potential measurements, XPS, Raman, FT-IR observations and SO4(2-) release determination. The ionic strength dependence and zeta potential measurements indicated that inner-sphere surface complexes were formed after Sb(V) adsorption. Raman and XPS observations demonstrated that both Fe-OH and Zr-OH sites at the surface of the Fe-Zr adsorbent play important roles in the Sb(V) adsorption. FT-IR characterization and SO4(2-) release determination further demonstrated that the exchange of SO4(2-) with Sb(V) also could promote the adsorption process. In conclusion, this adsorbent showed high potential for future application in Sb(V) removal from contaminated water.
Asunto(s)
Antimonio/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Concentración de Iones de Hidrógeno , Hierro/química , Cinética , Concentración Osmolar , Espectroscopía de Fotoelectrones , Espectroscopía Infrarroja por Transformada de Fourier , Espectrometría Raman , Sulfatos/análisis , Temperatura , Termodinámica , Circonio/químicaRESUMEN
Permeability significantly affects leachate transportation. Yet, there often exists a gap for its measurements between laboratory and the field. To predict the fate and transport of heavy metals from IBA leaching, a large-scale field trial study was performed using a big column (dâ¯×â¯hâ¯=â¯3â¯mâ¯×â¯5.5â¯m) packed with 1-m thickness of IBA (approx. 10.6 tons) overlaid by 4-m sand layer. The determined field permeability (kF) was compared with that achieved from the laboratory, demonstrating a large disparity as much as 4 orders of magnitude likely due to IBA self-compaction. Indeed, back calculation using Blake-Kozeny's equation unveiled that, the "effective" diameters were significantly reduced by 21-46%. kF also demonstrated an anisotropic characteristic associated with fingered flows, trapped bubbles and heterogeneous consolidation/cementation efficiencies. To quantify the effects by kF, we ran a mechanistic model to simulate the transport of 11 heavy metals under advection (dh/dx â¯=â¯0.05â¯m/m), indicating dramatically prolonged breakthrough time from days to centuries. Interestingly, breakthrough time was comparable among various metal ions (0-16.6% of RSD), suggesting their synchronous movements. Metal flux under kF was predicted in the end to address its toxicity potential, demonstrating limited environmental impacts in presence of the USEPA criterion.
Asunto(s)
Monitoreo del Ambiente , Modelos Químicos , Contaminantes Químicos del Agua/análisis , Anisotropía , Metales Pesados , PermeabilidadRESUMEN
Leaching kinetics of trace metals from incineration bottom ashes (IBA) under diffusion and advection were investigated through leaching tests of compacted granulars of IBAs and their packed columns with seawater eluent for 64 days and 26 days, respectively. Metal fluxes were distinct among species while linearily decreased at log-log scales as a function of time. Short-term environmental risks for Cu, Ni and Pb were identified under advection. The metal leaching behavior generally followed the pseudo-second order under diffusion, while the pseudo-first order kinetics under advection. Investigated metals may be further identified as diffusion- (As, Cd, Cr, Sb) and advection-dominant species (Ba, Cu, Ni, Pb, Zn) according to their fluxes, which interestingly corresponded to the low- (5.19-147.90 mg·kg-1) and high-value (116.46-2398.44 mg·kg-1) of their metal distribution from IBAs, respectively. Considering the general higher metal release, decay models were employed to simulate the column leaching results. Particularly, Type-II model based on two-site assumptions fit much better to the experimental data, unveiling significant yet retarded release (in 1-2 pore volumes) of certain metals from the slow-reaction sites. Further investigation on the release of bulk parameters unveiled that, there existed rebounded leaching rates primarily ascribed to the IBA heterogeneity.
RESUMEN
Incineration bottom ash (IBA) faces challenges for its sustainable recycling due to the absence of scenario-specific risk assessment. Environmental risk assessment was carried out via a case study incorporating key factors to dominate human exposures during IBA utilization in land reclamation. Three research components echoing respective IBA leaching, exposures, and consequences were performed under a supportive framework to elaborate these interlinked key factors and unveil the potential environmental risks. IBA leachability was firstly investigated using various laboratory standard leaching methods while conducted a large-scale field trial experiment for mutual confirmation, suggesting that maximum leached amounts may be achieved when liquid to solid (L/S) ratio increases to 10. Dilution and transportation models were both developed to discriminate the mitigation of IBA leachate between two periods i.e. during and after land reclamation, suggesting that dilution rather than transportation may dominate the environmental impact for metal exposures. Metal bioaccumulation from a typical mollusk species was performed coupling the calculated dietary safety limits based on Singaporean diet intake for development of the threshold of toxicology concerns on human exposures. With such, IBA benign usage in land reclamation was also conferred in the form of distance and dilution factor.