Immobilization Rates Research Articles

Response of soil phosphorus fractions and fluxes to different vegetation restoration types in a subtropical mountain ecosystem

Soil phosphorus (P) improvement is one of the important aims of vegetation restoration. However, the effects of different vegetation restoration types on soil P cycling and the underlying mechanisms remain unclear. Together with vegetation structure and soil properties, we measured the soil P fractions and P transformation rates to evaluate the characteristics of ecologically relevant soil P fraction distributions and their dynamics for the most common vegetation restoration types in a subtropical mountain ecosystem (i.e., PF, Pinus forest; EF, Eucalyptus forest; SL, shrubland; and NSF, natural secondary forest). We found that water-extractable inorganic P (Pi), organic P (Po), and acid phosphatase activity (APA) were significantly higher in NSF than those in the other vegetation types (P < 0.01), together with the highest gross P mineralization rate (Pmin) and net P immobilization rate (Pimm), suggesting biological processes played a more important role in soil P cycling in the NSF. In contrast, the soil showed the lowest values of Pmin, Pimm, and APA in the EF compared to NSF and PF (P < 0.05), together with the highest P loss and the higher net P solubilization rate (Psol), indicating the greater importance of soil geochemical processes. Compared with the NSF and EF, geochemical and biological processes co-regulated soil P cycling in the PF and SL. However, the soil in the PF displayed higher P fluxes (Pmin, Pimm, Psol, and P loss) than those in the SL (P < 0.05), suggesting the soil had higher P flux magnitudes in the PF. Results of correlation analyses showed that the soil microbial community structure and activity played a more important role than plant community attributes and soil physicochemical properties in soil P fraction distribution and fluxes. In conclusion, soil P fraction distributions and their fluxes can be significantly influenced by vegetation restoration types. Land management strategies focusing on restoration of the soil microbial community may enhance soil P cycling and improve soil quality.

Assessment of iron-based and calcium-phosphate nanomaterials for immobilisation of potentially toxic elements in soils from a shooting range berm

Shooting range facilities in military areas have been indicated as a hotspot of land degradation with high contents of Potentially Toxic Elements (PTEs). Currently, based on the new nanomaterials with specific characteristics, nanoremediation technologies are used to immobilise and to reduce the availability of PTEs in field and laboratory conditions. In this study, the effects of nano-hydroxyapatite and/or hematite on PTEs immobilisation (As, Cd, Cu, Pb, Sb and Zn) in military shooting range soils were assessed through the measure of available and leachable forms with three single-extractions: calcium chloride (0.01M CaCl2), low molecular weight organic acids (10 mM LMWOAs) and toxicity characteristic leaching procedure (TCLP). A sequential chemical extraction was used to determine the distribution of the PTEs in the different geochemical phases of the soils before and after the nanomaterial treatments. Results showed that the availability of PTEs decreased, especially for Pb (40–95%) and Zn (50–99%) after nanomaterial treatments. When both nanomaterial (hydroxyapatite + hematite) were combined, the immobilisation rate improved. However, when each nanomaterial was added individually to the soils, some elements, such as, Cu or Sb, showed a slight increment of their mobilisation. The sequential chemical extraction showed that the highest percentage of PTEs were mainly in the residual fraction before and after adding nanomaterials, being even higher in soils after the nanomaterial treatments. Likewise, the mobile fractions decreased after the treatment with nanomaterials. Our findings suggest that nanoremediation techniques improve the soil conditions, but they should be used carefully to avoid mobilisation of non-target PTEs or unexpected potentially impacts for soil biota.

Remediation of chromium-contaminated soil using delaminated layered double hydroxides with different divalent metals

Soil is commonly polluted by chromium, and layered double hydroxides (LDHs) are widely used for chromium removal due to their strong adsorption capacity and the unique properties of their delaminated products. In this study, delaminated LDHs (S–Mg-LDH and S–Ca-LDH) and their original LDHs were used to remediate Cr(VI)-contaminated soil. A series of characterizations confirmed the successful synthesis of delaminated LDHs whose sheet structure was thinner with a greater surface energy than the original LDHs. The remediation results indicated that delaminated LDHs could more efficiently immobilize Cr(VI) in soil. The immobilization rate of S–Mg-LDH was 64.32%, while Mg-LDH was only 8.09%. However, at low dosages, the efficiency of S–Ca-LDH was 28.1% while Ca-LDH was 5.16%, but they had similar effects at high doses. Moreover, soil pH had little effect on their removal efficiencies. The toxicity characteristic leaching procedure (TCLP) results showed that the leaching of Cr(VI) in soil after treatment with S–Mg-LDH, S–Ca-LDH, Mg-LDH, and Ca-LDH was reduced by 75.43%, 72.43%, 86.55%, and 75.90%, respectively. The phytotoxicity tests of soil treated by S–Mg-LDH and S–Ca-LDH revealed that they effectively reduced the toxicity of chromium and lowered its bioaccumulation. Overall, this study confirms the feasibility of delaminated LDHs for Cr(VI) immobilization in soils.

Characteristics of organic material inputs affect soil microbial NO3− immobilization rates calculated using different methods

AbstractMicrobial immobilization of nitrate (NO3−) is considered to be an important process in reducing NO3 − accumulation and regulating nitrogen (N) retention capacity in soils. Accurately quantifying the rate of microbial NO3− immobilization is, therefore, necessary to predict its role in lowering NO3− accumulation in soils. We compared microbial NO3− immobilization rates using a 15NO3− labelling technique in three different ways: (a) 15N pool dilution, (b) organic 15N recovery and (c) microbial biomass 15N recovery, in a nitrate‐rich upland soil with and without amendment with organic materials with differing carbon‐to‐nitrogen ratios (C/N). The three methods generated similar NO3− immobilization rates, except when the soil was amended with easily decomposable organic materials (glucose and sucrose). We also developed a microbial NO3− immobilization‐specific quality index that incorporates the C/N ratio, lignin, cellulose and hemicellulose contents and pH for slowly decomposing organic materials (plant residues). This study provides direct empirical evidence that the results of different methods for calculating soil microbial NO3− immobilization rates are affected by the characteristics of organic materials added to the soil.Highlights Three methods for estimating microbial NO3− immobilization were compared The methods generated similar NO3− immobilization rates when amended with plant residues Higher NO3− immobilization when measured with 15N dilution with readily available C input A microbial NO3− immobilization‐specific index for plant residues was developed

Soil Material Quality and Environmental Potential of Metallically Contaminated Soils

The paper presents the results of the evaluation of the environmental potential of soils in the area affected by the long-term mining activity. The environmental potential index consists of a numerical expression of the ability to provide water storage, immobilization of risk elements, and immobilization and transformation of organic pollutants. The exceedance of the limit values Hg, Cu, Zn, As, Cd and Pb was found in the soils of the investigated area of central Spiš. The rate of soil immobilization of risk elements is very low to high. The point value expressing the ability of agricultural lands to provide environmental functions is very low to medium in the studied areas, the financial expression of the values of the environmental potentials indexes is in the range of 7 100 to 14 000 € ha-1, while the average value of 1 ha of agricultural land in Slovakia is about 14 200 €.

Continuous Cropping Affects Gross Nitrogen Transformations in Subtropical Acidic Soils Under Greenhouse Cultivation

Relationship between gross N transformation rate and continuous cropping years in the greenhouse soil is largely unknown. This study aimed to investigate the mechanism of the gross N transformation rate changes in greenhouse subtropical acidic soils under different continuous cropping years. The 15N isotope tracer method was used to study the effects of greenhouse soil under 4 years of continuous cropping (C4), 5 years of continuous cropping (C5), and 7 years of continuous cropping (C7) of lily (Lilium brownii), respectively, on soil N transformation with the N tracer model. The results showed that the main soil N transformation processes were N mineralization, autotrophic nitrification, and NO3−-N immobilization under the three continuous cropping years. After continuous cropping, the gross N mineralization rate, autotrophic nitrification rate, and NO3−-N immobilization rate increased with the increase of continuous cropping years. Specifically, the gross N mineralization rate was 0.62~0.85 mg N kg−1 day−1, the autotrophic nitrification rate was 1.08~3.24 mg N kg−1 day−1, and the NO3−-N immobilization rate was 0.30~0.62 mg N kg−1 day−1. Moreover, the positive difference between the autotrophic nitrification rate and immobilization rate of NO3−-N became greater with the increase of continuous cropping years, which might have been the main reason for the accumulation of NO3−-N in greenhouse subtropical soils. These findings contribute to the understanding of the mechanism of soil secondary salinization formation and provide ideas for prevention of secondary salinization under long-term continuous cropping.

Posterior fusion of the craniocervical junction in the pediatric spine: Wright's translaminar C2 screw technique provides for more safety and effectiveness.

Posterior fusion of the craniocervical junction (CCJ) has always been challenging in children with rare congenital diseases and malformations. At our institution, the introduction of the translaminar C2 screw technique led to a significant improvement in the quality of treatment. Retrospective analysis of a pediatric cohort at a single institution whounderwent CCJposterior fusion between 2007 and 2018. Patients were divided into group 1 (other posterior fusion techniques, n = 12) and group 2 (translaminar axis screw placement, n = 19). Diagnosis, sex, age at surgery, surgical technique, immobilization, revisions, fusion, reduction, and complications were assessed. Follow-up ranged from 12 to 145months (mean 50.7). The initial fusion rate detected at 3months by CT differed significantly (66, 7% in group 1 vs. 100% in group 2, p = 0.018). Full reduction of C1/C2 malalignments was achieved in 41, 6% of group 1 versus 84, 2% of group 2 (p = 0.007). Immobilization was applied in 83, 3% of group 1 versus 26, 3% of group 2 (p = 0.0032). Ten complications were treated conservatively, and 15 events required revision surgery (80% in group 1 vs. 20% in group 2). Eight complications were related to immobilization. The implementation of the translaminar C2 technique resulted in significantly more safety and efficiency regarding pediatric posterior fusion CCJ surgery at our institution, with significantly higher rates of rigid fixation, full reduction, and fusion, and significantly lower rates of complications and immobilization. These slides can be retrieved under Electronic Supplementary Material.

Hydration behavior and immobilization mechanism of MgO–SiO2–H2O cementitious system blended with MSWI fly ash

MSWI(Municipal solid waste incineration) fly ash as hazardous wastes usually is treated properly with OPC(ordinary Portland cement) based binders prior to being disposed in security landfill, but some toxic elements present poor stability in its highly alkaline environment. This study developed a novel solidification/stabilization technology based on MgO–SiO2–H2O (M-S-H) cementious material with compatibility with contaminants for MSWI fly ash encapsulation. Compressive strength and leaching toxicity tests were undertaken to evaluate the immobilization effect of MSWI fly ash treated with M-S-H matrix. And TAM, XRD, DTA/TGA and SEM techniques were employed to explore hydration process and microstructure morphology of M-S-H solidified body. Results demonstrated that M-S-H cement matrix played a positive impact on the immobilization of heavy metals, and the immobilization rate of Cd, Pb and Zn was 97.5%, 99.8% and 98.7%, which was far more than that fixed in Portland cement. The incorporation of MSWI fly ash inhibited the hydration process of M-S-H matrix on the whole, which was mainly due to its poor pozzolanic activity. Moreover, there were some new hydration phases including CdSiO3, Ca3PbSiO6 and Zn(OH)2 generated and some MSWI fly ash embedded in the core-shell structure of M-S-H matrix in depth. These results suggested that heavy metals of MSWI fly ash were mainly fixed in M-S-H solidified bodies by physical encapsulation, isomorphous replacement and chemical precipitation. Overall, this study demonstrated that M-S-H matrix is a promising candidate that can serve as low-carbon and high-efficient materials for hazardous MSWI fly ash.

Characteristics and in situ remediation effects of heavy metal immobilizing bacteria on cadmium and nickel co-contaminated soil.

Cadmium (Cd) and nickel (Ni) in soil have caused serious environmental problems and increased healthy risks to humans and biota, it is vital important and necessary to develop effective methods to resolve the combined contaminated problems. In this study, strains L5 and L6 with good heavy metal resistant and immobilizing capacities were isolated from Cd and Ni contaminated soil. Bacterial characteristic experiment illustrated that many functional groups (-OH, -NH2 and -COO et al.) were distributed on the surface of L5 and L6. Under the stress of heavy metals, bacterial appearances were distorted. The pot experiment indicated that the concentrations of HOAc-extractable Cd and Ni in soil reduced 6.26-15.33% and 13.31-19.53% with the inoculation of L5 and L6. In addition, the immobilization rates on Cd and Ni improved 61.27-128.50% and 23.69-39.66% with re-inoculation of strains L5 and L6 at 30 days, respectively. After inoculation of strains L5 and L6 for 60 days, the activities of FDA hydrolysis, acid phosphatase, urease, invertase and dehydrogenase in soil increased obviously. Furthermore, bacterial diversity indexes and community structure of soil were also improved. Thus, given the beneficial remediation effects of the isolated strains, L5 and L6 have great potentials for heavy metals contaminated soil remediation.

Co-Immobilization and Co-Localization of Multi-Enzyme Systems on Porous Materials.

The immobilization of multi-enzyme systems on solid materials is rapidly gaining interest for the construction of biocatalytic cascades with biotechnological applications in industry. The heterogenization and control of the spatial organization across porous materials of the system components are essentials to improve the performance of the process providing higher robustness, yield, and productivity. In this chapter, the co-immobilization and co-localization of a bi-enzymatic bio-redox orthogonal cascade with in situ cofactor regeneration are described. An NADH-dependent alcohol dehydrogenase catalyzes the asymmetric reduction of 2,2,2 trifluoroacetophenone using an NADH regeneration system consisting of a glutamate dehydrogenase and glutamic acid. Three different spatial organizations of the enzymes were compared in terms of cofactor-recycling efficiency. Furthermore, we demonstrated how the co-localization and uniform distribution (by controlling the enzyme immobilization rate) of the main and recycling dehydrogenases inside the same porous particle lead to enhance the cofactor-recycling efficiency of the bi-enzymatic bio-redox systems.

Immobilization of functional biomolecules onto polypropylene fabric using plasma pre-treatment

In order to realize the immobilization of collagen, chitosan and sericin on the surface of polypropylene fabric, the fabric is treated by ammonia and nitrogen low temperature plasma to produce reactive groups, and then the epoxy compounds (ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether) are used as crosslinkers for a bridging process. Single factor experiment is carried out to investigate the influence of crosslinking parameters (temperature, time and the dosage of crosslinker) on immobilization yield. Chemical composition changes on the surface of the treated samples is analyzed by infrared spectroscopy, which indicated that the ammonia plasma treatment can produce more active groups. The results showed that immobilization rate of samples crosslinked by ethylene glycol diglycidyl ether is superior to that of trimethylolpropane triglycidyl ether. It also can be found that the fabric had a better wettability and antimicrobial properties. The whiteness and comfort property of chitosan-polypropylene fabric decreased slightly.

Phosphate rock solubilization and the potential for lead immobilization by a phosphate-solubilizing bacterium (Pseudomonas sp.)

Lead (Pb) pollution is getting more and more serious in phosphate mining wastelands recently. However, seldom studies focused on the bioremediation of Pb pollution in phosphate mining wastelands by phosphate-solubilizing bacterium (PSB). In this study, a PSB named LA with high Pb tolerance was isolated from a phosphate mining wasteland. Based on its cell morphology, physiology, and phylogenetic analysis, it was identified as Pseudomonas sp. Its capabilities to solubilize mid-low-grade phosphate rock (PR) and immobilize Pb were assessed in this study. It was found that LA could effectively solubilize PR on PKO culture medium and release soluble phosphate in the culture medium. PR solubilization and Pb immobilization were investigated at different initial Pb concentrations and pH levels. The results showed that soluble phosphate was highly effective in immobilizing Pb and that when the initial concentration of Pb2+ was 100 mg/L, the immobilization rate of Pb was enhanced. Further, the mechanisms underlying solubilization of PR and biomineralization of Pb ions in LA were evaluated by Fourier transform infrared spectroscopy and X-ray diffraction. The results showed that some functional groups on the PR surface and LA were altered, and LA could form hydroxyapatite and pyrophosphate with Pb ions.

Stable rates of operative treatment of distal radius fractures in Ontario, Canada: a population-based retrospective cohort study (2004–2013)

Rates of surgical management of distal radius fractures are increasing internationally despite the higher cost and limited outcome evidence to support this shift. This study examines the epidemiology of distal radius fractures and asks if the same shift has occurred in Ontario, Canada (population 13.9 million). This population-based, retrospective cohort study examined distal radius fractures in people aged 18 years and older over a 10-year period (2004–2013). The incidence analyses were based on the first occurrence of a fracture within a 2-year time period. The number of fractures, age-adjusted incidence rates and frequency of fracture treatment type by year were assessed. We used a Poisson regression with robust standard errors to determine if there was a statistically significant change in the frequency of fracture treatment type over time. There were 25 355 distal radius fractures among Ontarians 18 years of age and older in 2013. Between 2004 and 2013, the age-adjusted incidence rate for people 35 years of age and older was stable, between 2.32 and 2.70 per 1000 population. Rates of cast immobilization remained stable between 82% and 84%. Of those patients treated surgically, the rate of open reduction and internal fixation rose from 7% in 2004 to 13% in 2013 at the expense of other types of surgical management. In Ontario, rates of cast immobilization are stable and there has been a movement toward open reduction and internal fixation among patients treated surgically.

15N tracing studies including plant N uptake processes provide new insights on gross N transformations in soil-plant systems

Most soil N transformations studies are carried out using soil incubations without plants, despite the fact that plant-soil interactions potentially influence soil N dynamics. In this study, gross N transformation rates were quantified using a subtropical acidic forest with and without plants (and under different soil storage conditions). The results showed that the gross rates of N mineralization in air-dried and rewetted soil significantly increased, while the gross rates of nitrification and immobilization decreased, compared with fresh soil. Soil storage for more than one month at 4 °C (typical refrigerated conditions) and room temperature (25 °C) did not affect the gross rates of soil N mineralization and immobilization but significantly inhibited heterotrophic nitrification rates. Moreover, plants grown in the soil significantly stimulated gross rates of N mineralization, autotrophic and heterotrophic nitrification, and NO3− immobilization. Plant NH4+ uptake rates (3.74 mg N kg−1 d−1) were 374 times greater than the NH4+ immobilization rate (0.01 mg N kg−1 d−1). The competition for NH4+ between plants and soil microorganisms led to strong feedback effects on soil N transformations. Based on our results we recommend to carry out 15N tracing studies with plants to more realistically mimic field conditions. 15N tracing techniques in combination with 15N-tracing models, such as NtracePlant, provide a robust method to quantify soil N transformations and plant N uptake rates in plant-soil systems.

Efficiency of lime, biochar, Fe containing biochar and composite amendments for Cd and Pb immobilization in a co-contaminated alluvial soil

Present study reports the laboratory and field scale application of different organic and inorganic amendments to immobilize cadmium (Cd) and lead (Pb) in a co-contaminated alluvial paddy soil. For that purpose, lime, biochar, Fe-biochar and two composite amendments (CA) composed of biochar, lime, sepiolite and zeolite (CA1: composite amendment 1) and manure, lime and sepiolite (CA2: composite amendment 2) were firstly tested in an incubation experiment to ameliorate Cd and Pb co-contaminated alluvial soil. It was observed that liming and CA2 elevated the soil pH and reduced DTPA extractable Cd and Pb in the incubated soil leading to higher metal immobilization. Therefore, efficiency of lime and CA2 was further investigated in field conditions with mid rice as the test crop to evaluate field scale immobilization and precise application rate for the tested soil type. DTPA and CaCl2 extractable Cd (46 and 51%) and Pb (68 and 70%) in field soil were decreased with applied treatments. Speciation of Cd and Pb also promoted conversion of metal exchangeable contents to less-available forms. Activated functional groups on amendments’ surface (_OH bonding, C_O and CO, -O-H, Si–O–Si, carboxylic and ester groups) sequestered metals by precipitation, adsorption, ion exchange or electro static attributes. Application of lime at 2400 kg/acre (T4) and CA2 at 1200 kg/acre was more effective in reducing rice shoot and grains metal contents. Moreover, obtained results in terms of pH, extractable content, speciation and yield, and microanalysis of amendments highlights the remarkable efficiency of lime and composite amendment to sorb Cd and Pb providing the key evidence of these amendments for metals immobilization and environmental remediation. Considering these results, lime and CA2 are potential amendments for co-contaminated rice field especially in context of alluvial soil.

On how environmental and experimental conditions affect the results of aquatic nanotoxicology on brine shrimp (Artemia salina): A case of silver nanoparticles toxicity

The genus Artemia sp. has been accepted as a reliable model organism for aquatic toxicity and nanotoxicity experiments, as far as the ISO TS 20787 has recently been published to standardize nanotoxicity test with this organism. Experimental and environmental conditions may affect the toxicity of nanomaterials on aquatic organisms including Artemia sp. nauplii. In this study, acute toxicity effects of silver nanoparticles (AgNPs) on the nauplii of Artemia salina was investigated under various conditions (e.g. different lights, salinities, temperatures, volume and agitation of exposure media and instar stages of nauplii). The EC values were calculated using Probit program and all data were analyzed statistically by SPSS software. At all test conditions, the immobilization rate of Artemia nauplii increased in a concentration-dependent manner (P < 0.05). The sensitivity of instar stage II to different concentrations of AgNPs was significantly higher than instar I (P < 0.05). The toxicity effect of AgNPs was affected by alteration of environmental conditions, so that the effective concentration (EC) values for instar I of A. salina decreased with increasing water temperature, decreasing water salinity and in continuous darkness condition. The EC50 value of AgNPs was significantly lower in 100 mL beakers (21.35 ± 5.67 mg L−1) than 10 mL well plates (42.44 ± 11.30 mg L−1). Agitation of exposure media did not affect the toxicity of AgNPs. The results indicated that the experimental and environmental conditions influence on the toxicity of AgNPs in the nauplii of A. salina.

The Pediatric "Floating Knee" Injury: A State-of-the-Art Multicenter Study.

Isolated femoral and tibial fractures are 2 of the top 5 causes of pediatric orthopaedic hospital admission, yet their simultaneous ipsilateral presentation, the "floating knee" injury, remains rare. Historically, treatment consisted of traction and cast immobilization, which resulted in prolonged periods of immobilization, lengthy hospitalizations, and high rates of malunion. As such, previous authors have recommended fixation of at least 1 bone in the setting of a floating knee injury. This strategy, however, has never been evaluated and the outcomes of modern treatment are unknown. We performed a multicenter retrospective review of the records of pediatric patients with ipsilateral femoral and tibial fractures that had been treated at 11 tertiary care level-I pediatric trauma centers from 2004 to 2014. Outcomes and treatment strategies were assessed with standardized means. Over the study period, 130 floating knees in 129 patients met the inclusion criteria for evaluation. The average patient age was 10.2 years, and 63.1% were male. One-third of the patients presented with open injuries, and 83.8% of injuries were related to vehicular trauma. Simple diaphyseal fractures (OTA/AO 32-A and B femoral fractures and OTA/AO 42-A and B tibial fractures) were most common. Intramedullary fixation (rigid or flexible) was the most common treatment strategy for femoral fractures (69.2%). Tibial fractures were treated most commonly with casting (27.7%), followed by flexible intramedullary nailing (24.6%). The mean duration of hospitalization was 9.7 days. Outcomes were excellent in 66.6% of cases and good in 26.4% of cases. Previous literature on pediatric floating knee injuries consisted of small case series that were published prior to the introduction of flexible intramedullary nailing to North America. This multicenter study of a large cohort demonstrates a change in practice pattern from a largely nonoperative treatment strategy to operative fixation of at least the femoral fracture. In the present study, this approach led to good or excellent results in 93.1% of cases and was associated with a short duration of hospitalization. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Annual dynamics of soil gross nitrogen turnover and nitrous oxide emissions in an alpine shrub meadow

Soil nitrogen (N) transformations play a vital role in maintaining grassland productivity and influence nitrous oxide (N2O) emissions. To evaluate annual dynamics of soil gross N turnover and its effects on N2O emissions in typical grasslands, we conducted year-round measurements of soil gross N turnover rates, inorganic N pool sizes and N2O fluxes in an alpine shrub meadow of the Qinghai–Tibet Plateau. Gross ammonium (NH4+) and nitrate (NO3−) immobilization rates were calculated by the “isotope dilution method” (i.e., based on the consumption rates) and the “reformed difference method” (i.e., based on the differences between gross and net turnover rates). The “reformed difference method” avoids additional measurements of net N turnover rates in unlabeled soils compared to the traditional “difference method”, and provides more reliable estimates of NH4+ immobilization in soils with low ambient NH4+ pool sizes than the “isotope dilution method”. The annual gross rates of mineralization, nitrification, NH4+ and NO3− immobilization amounted to 606 ± 43, 236 ± 27, 389 ± 24 and 82 ± 19 mg N kg−1 dry soil yr−1, respectively, in a topsoil of 10 cm. The soil gross N turnover rates during freezing and freeze–thaw periods contributed considerably to the annual totals (22–44%). Thus, the freezing and freeze–thaw periods were not dormant seasons for microbial N transformations, even under a frigid alpine climate. The annual N2O emission was 0.20 ± 0.03 kg N ha−1 yr−1, 35% of which originated from a short-lived emission pulse during the freeze–thaw period (52 d). The promotion of gross mineralization increased soil NH4+ pool sizes, whereas the increase in gross nitrification did not enhance soil NO3− pool sizes during the freeze–thaw period. Coupled nitrification–denitrification dominated NO3− consumption and freeze–thaw related N2O production and hence, the low NO3− pool sizes were not indicative of the potential of pulsed N2O emissions. Year-round measurements with intensive observations during both the non-freezing and freeze–thaw periods are indispensable to fully understand soil N cycling and its response to climate change in alpine ecosystems.

Bioreactor Membranes for Laccase Immobilization Optimized by Ionic Liquids and Cross-Linking Agents.

A novel concept of membrane bioreactor based on polymeric ionic liquids laccase membrane has been implemented in batch process for decolorization of the anthraquinonic dye Remazol Brillant Blue R (RBBR). New laccase immobilization strategy has been optimized by casting the enzyme into a polymeric inclusion membrane (PIM) using ionic liquids (ILs) and polyvinyl chloride (PVC) leading to laccase polymeric IL membrane (PILM). Four different ILs (1-octyl-3-metylimidazolium bis(trifluoromethylsulfonyl)imide, [OMIM][NTF2]; cholinium bis(trifluoromethylsulfonyl)imide, [Ch ol][NTF2]; cholinium dihydrogenphosphate, [Chol][H2PO4] and hydroxyethylammonium formate, [HEA][Fo]) have been screened and mixed to constitute the active phase of the support of PIM. This strategy has been fully succeeded since high laccase immobilization rates were recorded (about 98%) when using the optimal mixture containing three ILs (45% [OMIM][NTf2]/5% [Chol][NTf2]/2.5% [HEA][Fo]) and supplemented by 0.5% glutaraldehyde. It was found that such mixture contributes to increase the stability and reusability of laccase-PILM during eight successive assays in a batch discontinued stirred reactor. Decolorization rate of 75% has been reached in the batch decolorization process of RBBR with high reusability yield. Graphical Abstract Decolorization of RBBR by PILM_laccase.

Highly effective immobilization of Pb and Cd in severely contaminated soils by environment-compatible, mercapto-functionalized reactive nanosilica

Soils contaminated with Pb and Cd greatly threaten the health of humans. With a view to decrease the environmental risk of Pb and Cd in the soil, we design and prepare a type of immobilization material possessing high stability and high immobilization efficiency towards Pb and Cd. Nanosilica which has good compatibility with soils is chosen as the matrix and functional groups (mercapto) are loaded on the nanosilica surface via the covalently bonding between 3-mercaptopropyl-trimethoxysilane (denoted as MPTS) and nanosilica. The as-prepared MPTS/nano-silica is characterized, and its immobilization efficiency towards Pb and Cd in contaminated soil as well as the stability of the immobilized Pb and Cd under acidic condition is evaluated. Results demonstrate that the as-prepared nanosilica has spherical or spheroidal shape and exhibits a diameter of 20–30 nm. In the meantime, MPTS/nano-silica selectively reacts with Pb and Cd to reduce the content of bioavailable-Pb and bioavailable-Cd from 1193.54 mg/kg and 12.46 mg/kg to 10.34 mg/kg and 0.22 mg/kg, respectively, providing an immobilization rate of 99.12% and 98.23% for Pb and Cd. The results of chemical species analysis of Pb/Cd indicate that the nanosilica can transform most Pb/Cd from unstable species into more stable species. More importantly, MPTS/nano-silica exhibits low impact on soil and the Pb- and Cd-species immobilized by MPTS/nano-silica exhibit greatly increased acid resistance, which could be significant for the long-term remediation of the heavy-metal-contaminated soils.