35-day Incubation Research Articles

Biodegradation of Di-2-Ethylhexyl Phthalate by Mangrove Sediment Microbiome Impacted by Chronic Plastic Waste.

Plastic pollution through the leaching of di(2-ethylhexyl) phthalate (DEHP), a widely used plasticizer, has led to the emergence of mangrove pollution. This study aimed to assess the DEHP removal efficiency of indigenous mangrove sediment microbiomes and identify key DEHP degraders using microcosm construction and metagenomic analysis. During the 35-day incubation period, the indigenous mangrove sediment microbiome, affected by chronic plastic pollution, demonstrated a 99% degradation efficiency of 200mg/kg DEHP. Spearman's correlation analysis suggested that Myxococcales, Methyloligellaceae, Mycobacterium, and Micromonospora were potentially responsible for DEHP degradation. Based on PICRUSt2, the DEHP-degrading pathway in the sediment was predicted to be an anaerobic process involving catechol metabolism through catC, pcaD, pcaI, pcaF, and fadA. Efficient bacterial isolates from the mangrove sediment, identified as Gordonia sp. and Gordonia polyisoprenivorans, were able to degrade DEHP (65-97%) within 7days and showed the ability to degrade other phthalate esters (PAEs).

Microplastics and biochar interactively affect nitrous oxide emissions from tobacco planting soil

Biochar application to amend acidified tobacco-soils can enhance tobacco quality and reduce nitrous oxide (N2O) emissions. Microplastics from agricultural mulch are commonly found in cash-crop farmland soils and, together with biochar, affect soil N2O emissions. In this study, we applied three types of microplastics (polyethylene, PE; polylactic acid, PLA; polybutylene adipate terephthalate, PBAT) and rice biochar alone or in combination to acidified tobacco planting soil in central China to investigate their effects on soil N2O emissions, soil chemical properties, nitrogen-cycle-related functional genes, and microbial functional diversity during a 35-day laboratory incubation period. Significant increases in N₂O emissions were observed with PE and PLA, which raised emissions by 15.96 % and 21.52 %, respectively. Additionally, different microplastics affected soil N₂O emissions through distinct regulatory pathways. Co-application of microplastics and biochar suppressed N2O emissions compared to microplastics alone. Biochar mitigates N2O emissions mainly by increasing the abundance of the nosZ gene. It can remediate soil contaminated by microplastics and reduce their negative impacts on the soil environment. This study provides deeper insight into the effects of microplastics on soil nitrogen cycling and biochar-mitigated remediation of microplastic-contaminated soil.

Impact of iron-modified biochars on soil nitrous oxide emissions: Variations with iron salts and soil fertility

Nitrous oxide (N2O) emissions from soils are a significant environmental concern due to their contribution to greenhouse gas emissions. Biochar has been considered as a promising soil amendment for its potential to influence soil processes. Iron modification of biochar has been extensively discussed for its ability to enhance adsorption of pollutants, yet its impact on mitigating soil N2O emissions remains poorly understood. In the present study, corn straw (CB) and wood (WB) biochars were treated with FeSO4/FeCl3 (SCB and SWB) and Fe(NO3)3 (NCB and NWB). The effects of these biochars on soil N2O emissions were investigated using soils with varying fertility levels over a 35-day incubation period at 20 °C. Results revealed significant variations in biochar surface chemistry depending on biochar feedstock and iron salts. Compared to pristine biochars, NWB and NCB exhibited higher pH, total N content, and dissolved NO3–N concentrations (246 ± 17 and 298 ± 35 mg kg−1, respectively), but lower bulk and surface C content. In contrast, SWB and SCB demonstrated acidic pH and elevated dissolved NH4–N concentrations (5.38 ± 0.43 and 4.19 ± 0.22 mg kg−1, respectively). In forest soils, NWB and NCB increased cumulative N2O emission by 28.5% and 67.0%, respectively, likely due to the introduction of mineral nitrogen evidenced by significant positive correlation with NO3–N or NH4–N. Conversely, SWB and SCB reduced emissions in the same soil by 28.5% and 6.9%, respectively. In agricultural soil, most biochars, except SWB, enhanced N2O emissions, possibly through the release of labile organic carbon facilitating denitrification. These findings underscore the significance of changes in biochar surface chemistry and the associated potential risk in triggering soil N2O emissions. This study highlights the need for a balanced design of biochar that considers both engineering benefits and climate change mitigation.

Swine Manure Reduces Nitrous Oxide Emissions from Acidic Red Soil Due to Mineral N Immobilization and Alleviated Acidification

Swine manure is widely used for ameliorating red soil acidification, but little information is available about its effect on N2O emissions. To explore the effects, a 35-day incubation experiment was conducted with two soils under different fertilization history: chemical fertilizers only (F) and combination of chemical fertilizers with swine manure (M). The treatments included no fertilizer (control), 100% N from urea (M0), and urea plus swine manure, which supplied 20% (M20), 40% (M40), 60% (M60), and 100% (M100) of total N. Soil N2O emission rates, pH, exchangeable acidity, mineral N species, dissolved organic carbon and nitrogen, microbial biomass carbon, and their inner relationships were examined. The N2O emission rates markedly increased following the treatments, reached peaks before day 2, and thereafter decreased sharply to the level of the control by day 25, 25, 23, 15, and 9 in F soil and by day 25, 25, 23, 19, and 11 in M soil for M0, M20, M40, M60, and M100 treatments, respectively. As swine manure application rate increased, the cumulative N2O emissions of F soil decreased significantly, while, for M soil, there was no significant difference among M0, M20, M40, and M60 treatments, which were higher than the M100 treatment. At the end of incubation, soil pH in F and M soils followed the order M0 < M20 < M40 < M60 < control < M100 and vice versa for exchangeable Al3+ and acidity. F soil had relatively higher NH4+-N concentration in M0 treatment and higher NO3−-N concentrations in M0 and M20 treatments than M soil. Soil pH and NH4+-N had the greatest relative contribution to N2O emissions. Overall, this study indicates that partial chemical N replacement by swine manure could effectively mitigate N2O emissions from acidic red soil primarily because of mineral N immobilization and alleviated red soil acidification. Thus, swine manure has the potential to co-ameliorate red soil acidification and N2O emission. Further research is needed to determine the effect of swine manure on N2O emission reductions under field conditions and the overall benefit in effective N management.

The greenhouse effect of antibiotics: The influence pathways of antibiotics on methane release from freshwater sediment

The impact of antibiotics on methane (CH4) release from sediment involves both CH4 production and consumption processes. However, most relevant studies lack a discussion of the pathways by which antibiotics affect CH4 release and do not highlight the role played by the sediment chemical environment in this influence mechanism. Here, we collected field surface sediments and grouped them with various antibiotic combination concentration gradients (50, 100, 500, 1000 ng g−1) under a 35-day indoor anaerobic constant temperature incubation. We found that the positive effect of antibiotics on sediment CH4 release potential appeared later than the positive effect on sediment CH4 release flux. Still, the positive effect of high-concentration antibiotics (500, 1000 ng g−1) occurred with a lag in both processes. Also, the positive effect of high-concentration antibiotics was significantly higher than low-concentration antibiotics (50, 100 ng g−1) in the later incubation period (p < 0.05). We performed a multi-collinearity assessment of sediment biochemical indicators, followed by a generalized linear model with negative binomial regression (GLM-NB) to obtain essential variables. In particular, we conducted the interaction analysis on CH4 release potential and flux regression for the influence pathways construction. The partial least-squares path modeling (PLS-PM) demonstrated that the positive effect of antibiotics on CH4 release (Total effect = 0.2579) was primarily attributed to their effect on the sediment chemical environment (Direct effect = 0.5107). These findings greatly expand our understanding of the antibiotic greenhouse effect in freshwater sediment. Further studies should more carefully consider the effects of antibiotics on the sediment chemical environment, and continuously improve the mechanistic studies of antibiotics on sediment CH4 release.

Insights into characteristics of white rot fungus during environmental plastics adhesion and degradation mechanism of plastics

Since the 1980s, plastic waste in the environment has been accumulating, and little is known about fungi biodegradation, especially in dry environments. Therefore, the research on plastic degradation technology is urgent. In this study, we demonstrated that Phanerochaete chrysosporium (P. chrysposporium), a typical species of white rot fungi, could react as a highly efficient biodegrader of polylactic acid (PLA), and 34.35 % of PLA degradation was obtained during 35-day incubation. A similar mass loss of 19.71 % could be achieved for polystyrene (PS) degradation. Here, we presented the visualization of the plastic deterioration process and their negative reciprocal on cell development, which may be caused by the challenge of using PS as a substrate. The RNA-seq analysis indicated that adaptations in energy metabolism and cellular defense were downregulated in the PS group, while lipid synthesis was upregulated in the PLA-treated group. Possible differentially expressed genes (DEG) of plastic degradation, such as hydrophobic proteins, lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac), Cytochrome P450 (CYP450), and genes involved in styrene or benzoic acid degradation pathways have been recorded, and we proposed a PS degradation pathway.

Effect of Phosphogypsum Amendment on Chemical Properties of Sodic Soils at Different Incubation Periods

The application of phosphogypsum (PG) on sodic soils provides nutrients to the soil, reduces the toxic effect of Na+, and improves soil properties. Laboratory experiments were performed to evaluate the effects of PG on the chemical properties of sodic soils. The treatments were arranged in a completely randomized design with five replications. The treatments included 0% GR (control), 50% GR (28.18 g·kg−1), 100% GR (56.37 g·kg−1), 150% GR (84.50 g·kg−1), and 200% GR (112.74 g·kg−1) rates that were thoroughly mixed with soil under incubation, whereas PG was mixed with topsoil before leaching at the same application rates under the leaching experiment. Soil and leachate samples from each pot were collected in 7, 14, 21, 28, and 35 days and subjected to spectrometric analysis. Results indicated that there was a highly significant ( p &lt; 0.001 ) effect on soil pH, exchangeable sodium percentage (ESP), available P, exchangeable Na+, and Ca+2 under 35-day incubation compared with control. In a closed incubation system, most of the nutrients were released after 7 days of incubation and inconstantly released after 14 days of incubation. Furthermore, the removal of Na+ and SAR increased in initial leachate collection and decreased with the subsequent application of irrigation water (PV). Because of the high contents of Ca+2 released from PG and the residual effect of H2SO4, soil pH and ESP were rapidly reduced compared with control. Post leachate analysis also revealed that available P and extractable S-SO4−2 were significantly ( p &lt; 0.001 ) increased in soil solutions. However, available P was decreased during incubations compared with the value of post leachate analysis. During a closed incubation, displaced Na+ replaces Ca+2 on exchange sites, resulting in increased Ca-P precipitation. Thus, the combined application of PG and irrigation water in 7 to 14 days would allow chemical reaction with the soils and reduce sodicity problems to crop planting.

Greenhouse Gas Emissions from Forest Soils Reduced by Straw Biochar and Nitrapyrin Applications

Forestlands are widely distributed in the dominantly agricultural landscape in western Canada, and they play important ecological functions; such forestlands (e.g., shelterbelts) accumulate soil organic matter and may receive a substantial amount of nitrogen in the form of surface and subsurface runoff from adjacent croplands and become a significant source of emissions of greenhouse gases (GHGs) such as CO2, N2O, and CH4. Biochar and nitrapyrin applications could potentially mitigate GHG emissions, but their co-application in forest soils has not been studied. We investigated the effect of the application of biochars produced at low (300 °C; BC300) and high temperatures (700 °C; BC700) using canola (Brassica napus L.) straw and the effect of their co-application with nitrapyrin on GHG emissions and soil properties in a 35-day laboratory incubation experiment using forest soils collected from five shelterbelt sites. Results showed no significant interaction effect of biochar and nitrapyrin on the global warming potential (GWP) of the GHG emissions, and the GWP was 15.8% lower in the soil with nitrapyrin than without nitrapyrin application treatments. The GWP was significantly enhanced by BC300 addition due to a 26.9% and 627.1% increase in cumulative CO2 and N2O emissions, respectively, over the 35-day incubation. The GWP significantly decreased by BC700 addition due to a 27.1% decrease in cumulative CO2 emissions. However, biochar addition did not affect CH4 emissions, while nitrapyrin decreased CH4 uptake by 50.5%. With BC300 addition, soil-dissolved organic carbon and microbial biomass carbon increased by 26.5% and 33.9%, respectively, as compared to no biochar addition (CK). Soil pH increased by 0.16 and 0.37 units after the addition of BC300 and BC700, respectively. Overall, the effect of biochar and nitrapyrin was independent in mitigating GHG emissions and was related to the type of biochar applied and changes in soil properties.

The effect of dolomite amendment on soil organic carbon mineralization is determined by the dolomite size

BackgroundThe size of lime material is vital for the efficiency of ameliorating soil acidity, thereby influencing soil biochemical processes. However, the effects of different sized lime material application on soil organic carbon (SOC) mineralization are yet to be elucidated. Therefore, a 35-day incubation experiment was conducted to determine the effects of three particle size fractions (0.5 to 0.25, 0.25 to 0.15, and < 0.15 mm) of dolomite on SOC mineralization of two acidic paddy soils.ResultsCO2 emission was increased by 3–7%, 11–21%, and 32–49% for coarse-, medium-, and fine-sized dolomite treatments, respectively, compared to the control in both soils. They also well conformed to a first-order model in all treatments, and the estimated decomposition rate constant was significantly higher in the fine-sized treatment than that of other treatments (P < 0.05), indicating that SOC turnover rate was dependent on the dolomite size. The finer particle sizes were characterized with higher efficiencies of modifying soil pH, consequently resulting in higher dissolved organic carbon contents and microbial biomass carbon, eventually leading to higher CO2 emissions.ConclusionsThe results demonstrate that the size of dolomite is a key factor in regulating SOC mineralization in acidic paddy soils when dolomite is applied to manipulate soil pH.

Canola straw biochars produced under different pyrolysis temperatures and nitrapyrin independently affected cropland soil nitrous oxide emissions

The effect of biochar and nitrapyrin (a nitrification inhibitor) applications on nitrous oxide (N2O) emissions from a cropland soil was studied in a 35-day incubation experiment. The biochars were produced using canola (Brassica napus L.) straw under two pyrolysis temperatures: 300 (BC300) and 700 °C (BC700). Biochars (20 g kg−1 soil) and nitrapyrin (80 mg kg−1 soil) were applied alone or in combination. The cumulative N2O emissions were affected by both biochar and nitrapyrin applications (p < 0.05, same below) but not by their interaction. Cumulative N2O emissions were not affected by BC700, but were increased by BC300, as compared with the CK treatment (no biochar addition). Nitrapyrin significantly decreased cumulative N2O emissions by inhibiting nitrification, whether biochar was applied or not. There were positive relationships (p < 0.05) between cumulative N2O emissions and soil microbial biomass carbon to nitrogen ratio, nitrate and dissolved organic nitrogen concentrations, and net nitrification rates. Our results show that biochars need to be appropriately selected (such as the use of BC700) that do not increase N2O emissions, while the effectiveness of nitrapyrin in reducing N2O emissions was not affected by the co-application of biochars. We conclude that the co-application of biochar and nitrapyrin may be able to both increase soil C sequestration by the addition of stable C contained in the biochar and reduce N2O emissions from agricultural production systems.

Effects of ammonium-based nitrogen addition on soil nitrification and nitrogen gas emissions depend on fertilizer-induced changes in pH in a tea plantation soil

Tea (Camellia sinensis L.) plants have an optimal pH range of 4.5–6.0, and prefer ammonium (NH4+) over nitrate (NO3−); strong soil acidification and nitrification are thus detrimental to their growth. Application of NH4+-based fertilizers can enhance nitrification and produce H+ that can inhibit nitrification. However, how soil acidification and nitrification are interactively affected by different NH4+-based fertilizers in tea plantations remains unclear. The objective of this research was to evaluate the effect of the application of different forms and rates of NH4+-based fertilizers on pH, net nitrification rates, and N2O and NO emissions in an acidic tea plantation soil. We conducted a 35-day aerobic incubation experiment using ammonium sulphate, urea and ammonium bicarbonate applied at 0, 100 or 200 mg N kg−1 soil. Urea and ammonium bicarbonate significantly increased both soil pH and net nitrification rates, while ammonium sulphate did not affect soil pH but reduced net nitrification rates mainly due to the acidic nature of the fertilizer. We found that the effect of different NH4+-based nitrogen on soil nitrification depended on the impact of the fertilizers on soil pH, and nitrification played an important role in NO emissions, but not in N2O emissions. Overall, urea and ammonium bicarbonate application decoupled crop N preference and the form of N available in spite of increasing soil pH. We thus recommend the co-application of urease and nitrification inhibitors when urea is used as a fertilizer and nitrification inhibitors when ammonium bicarbonate is used as a fertilizer in tea plantations.

Decarboxylation of organic anions to alleviate acidification of red soils from urea application

Decarboxylation of organic anions in crop straw is recognized as one of the mechanisms for increasing pH in acidified soils. However, the effectiveness of specific compounds in alleviating soil acidification from nitrification has not been well determined. This study examined three organic anions commonly found in crop straws and their effect on soil acidity and N transformation processes following urea application to a red soil (Ferralic Cambisol). A 35-day incubation experiment was conducted using soil after receiving 26 years of two different nutrient treatments: (1) chemical nitrogen, phosphorus, and potassium fertilization (NPK, pH 4.30) and (2) NPK plus swine manure (NPKM, pH 5.88). Treatments included three rates (0.25, 0.5, and 1.0 g C kg−1) of calcium citrate, 0.5 g C kg−1 calcium oxalate, 0.5 g C kg−1 calcium malate, urea-only (control) soil, and a non-treated soil as a reference. Soil acidity, mineral N species, decarboxylation, and their correlations were determined. All three organic anions significantly increased pH in both soils and the effectiveness was positively correlated with application rate. The change in total exchangeable soil acidity was dominated by aluminum concentration in the NPK soil, but by proton concentration in the NPKM soil. At ≥ 0.5 g C kg−1, the anions decreased soil exchangeable acidity by 25–68% in NPK soil and by 63–88% in NPKM soil as compared with control. Oxalate was the most effective in increasing soil pH by 0.70 and 1.31 units and reducing exchangeable acidity by 3.79 and 0.33 cmol(+) kg−1 in NPK and NPKM soils, respectively, and also resulted in the highest CO2 production rate. Addition of organic anions led to a lower nitrification rate in NPKM soil relative to the NPK soil. These results imply that crop straws rich in organic anions, especially oxalate, would have a higher potential to alleviate soil acidification.

Cattle urine and dung additions differently affect nitrification pathways and greenhouse gas emission in a grassland soil

How cattle urine and dung addition, and their interaction with the mineral soil regulate cumulative autotrophic and heterotrophic nitrifications and greenhouse gas (GHG) emission is poorly understood. We investigated the effect of urine (applied at 425 mg N kg−1 soil) and dung (applied at 200 mg total N kg−1 soil) addition on cumulative autotrophic and heterotrophic nitrifications, and GHG emission in a grassland soil in a 35-day laboratory incubation experiment under six treatments: CK, unamended control; U, urine addition; Ds, dung added on the soil surface; U-Ds, urine addition + dung added on the soil surface; Dm, dung mixed into the soil; and U-Dm, urine addition + dung mixed into the soil. Compared with the CK, the U, U-Ds, and U-Dm treatments increased cumulative net nitrification (autotrophic + heterotrophic) by 548, 587, and 505% and cumulative autotrophic nitrification by 593, 618, and 508%, but the Dm treatment decreased cumulative net and autotrophic nitrifications by 77 and 83%, respectively. However, cumulative heterotrophic nitrification was less than 1% of the cumulative autotrophic nitrification in the CK and it was decreased by Ds and Dm as compared with the CK at the end of the incubation. Cumulative emissions of carbon dioxide (CO2) and nitrous oxide (N2O) were in the order of CK < U < Ds < Dm < U-Ds < U-Dm. In addition, all urine and dung treatments reduced cumulative methane (CH4) uptake (negative values of CH4 emission) as compared with the CK. Overall, soil cumulative net and autotrophic nitrifications were higher, but GHG emission was lower, with dung added on the soil surface than with it mixed into the soil. We conclude that urine addition increases but dung addition decreases cumulative autotrophic nitrification; dung addition also decreases heterotrophic nitrification, and how dung is added to the soil is important in regulating the nitrification processes and GHG emission. Therefore, urine and dung management can alter soil N transformations and has implications for mitigating climate change.

Nitrification inhibition by urine from cattle consuming Plantago lanceolata

Plantain (Plantago lanceolata L.) has the potential to indirectly reduce nitrate leaching from urine patches via compounds excreted in the urine of animals grazing the forb acting as biological nitrification inhibitors. Proof-of-concept research was previously undertaken using sheep urine, but it is important to examine whether this effect also occurs with cattle urine since cattle pose a greater N-leaching risk due to their higher urinary-N load. Housed dairy heifers (n=4) were assigned ad libitum dietary treatments of perennial ryegrass/ white clover or plantain for 14 days. On day 14, urine was collected through a sterile Foley catheter into a sealed container. Cattle then switched dietary treatment and urine was collected after a further 14 days. Urine samples were applied to soil microcosms and the net nitrification rate during a 35-day incubation determined. Similar urine-N concentrations were applied initially but a slower rate of soil nitrification was observed in the microcosms treated with urine from plantain-fed cows compared with those treated with urine from ryegrass/white clover-fed cows. The urine samples collected after the crossover showed a wider treatment difference in total N concentration, but also demonstrated a reduction in soil nitrification rate under the plantain urine. These results show similar trends to those previously reported for sheep urine.

English

Hydrocarbons released into ecosystems have led to environmental pollution and generated a serious threat to human health. Bioremediation is an effective method to break down hazardous hydrophobic environmental contaminants with avoiding economic and technical disadvantages. This study aimed to evaluate the efficiency of Bacillus subtilis SE1, a lipopeptide biosurfactant producer isolated from a petrochemical contaminated soil, on biodegradation of gasoline, diesel oil, crude oil and used engine oil in soil microcosms. During 35-day incubation, numbers of soil bacteria in petrochemical contaminated soils with B. subtilis SE1 addition significantly (P < 0.05) increased in comparison with the oil-free soils. Bioaugmentation of SE1 strain also produced a significant (P < 0.05) increase in percent reduction of total phenolic content in oil-polluted soils as compared to the control soils at the end of experiment. This study indicates that B. subtilis SE1 can be a promising hydrocarbon degrader for in situ bioremediation of soil environment polluted with petroleum and petrochemical products. Key words: Bacillus subtilis, biodegradation, bioremediation, gasoline, diesel, crude oil, engine oil.

Characterization of Dioctyl terephthalate biodegradation by food waste composting

Dioctyl terephthalate (DOTP), a plasticizer is used as an additive in many plastic products. Disposal of DOTP into environment has been of concern because it is hardly biodegradable in nature. Therefore, the aim of this study is to investigate the biodegradation of DOTP by aerobic composting processes without bioaugmentation. The initial DOTP concentration in the compost mixture was 11,882 mg/kg, after 35-day incubation, the removal efficiency of the compost reactor was 98%. The degradation was found to follow the first-order kinetic with the half-life of 5.2 days. Food waste composting was demonstrated as a technically robust and economically competitive process for the degradation of DOTP, and that of other similar plasticizers are expected.

Physicochemical aspects of recycling tree leaf litter in the south of Western Siberia by the Eisenia fetida (Savigny) vermiculture

The utility of the compost worm Eisenia fetida (Savigny) for recycling mixed leaf litter of the tree species characteristic of the forests in the south of Western Siberia and used in the landscaping in the city of Tomsk has been demonstrated. The tree species that are the major contributors to the leaf litter in the examined area include the genera Populus, Salix, and Betula. Two-fraction substrates for leaf litter vermicomposting and conventional composting (decomposition with and without earthworms) were prepared of the harvested and dried leaf litter. The feeding fraction consisted of leaf litter moistened with distilled water and the absorbing fraction, of alluvial river sand. The physicochemical properties of the studied leaf litter were weakly acidic pH of aqueous extracts, a very low content of nitrate nitrogen, and a relatively low K+ concentration. The prevalent cation in the assayed leaf litter was Ca2+. The leaf litter was partially decomposed on the surface of sand substrates during 35-day incubation under humid conditions; accumulation of inorganic ions in the sand was one of the signs indicating this decomposition. Ca2+ was also prevalent among these ions.

Hydrogels of agarose, and methacrylated gelatin and hyaluronic acid are more supportive for in vitro meniscus regeneration than three dimensional printed polycaprolactone scaffolds

In this study, porcine fibrochondrocyte-seeded agarose, methacrylated gelatin (GelMA), methacrylated hyaluronic acid (MeHA) and GelMA-MeHA blend hydrogels, and 3D printed PCL scaffolds were tested under dynamic compression for potential meniscal regeneration in vitro. Cell-carrying hydrogels produced higher levels of extracellular matrix (ECM) components after a 35-day incubation than the 3D printed PCL. Cells on GelMA exhibited strong cell adhesion (evidenced with intense paxillin staining) and dendritic cell morphology, and produced an order of magnitude higher level of collagen (p < 0.05) than other materials. On the other hand, cells in agarose exhibited low cell adhesion and round cell morphology, and produced higher levels of glycosaminoglycans (GAGs) (p < 0.05) than other materials. A low level of ECM production and a high level of cell proliferation were observed on the 3D printed PCL. Dynamic compression at 10% strain enhanced GAG production in agarose (p < 0.05), and collagen production in GelMA. These results show that hydrogels have a higher potential for meniscal regeneration than the 3D printed PCL, and depending on the material used, fibrochondrocytes could be directed to proliferate or produce cartilaginous or fibrocartilaginous ECM. Agarose and MeHA could be used for the regeneration of the inner region of meniscus, while GelMA for the outer region.

Bioturbation Effects of Chironomid Larvae on Nitrogen Release and Ammonia-Oxidizing Bacteria Abundance in Sediments

The purpose of this work was to reveal the Chironomid larvae bioturbation impact on N release and to find the mechanism of bioturbation to N conversion at the SWI (sediment–water interface). Sampling at four points during a 35-day incubation experiment was conducted. Two in situ techniques (microelectrode and Peeper) were used to capture more realistic and accurate microenvironment information around U-shaped corridors. The results demonstrate that the concentrations of ammonia nitrogen (NH4+) and nitrate nitrogen (NO3−) decreased by 21.26% and 19.50% in sediment and increased by 8.65% and 49.82% in the overlying water compared to the control treatment, respectively. An inverse relationship was observed between NH4+ and NO3− concentrations in pore water in Chironomid larvae treatment, and they were significantly negatively/positively correlated with AOB (ammonia-oxidizing bacteria) abundance, respectively. This study confirmed that the Chironomid larvae bioturbation promoted the N (NH4+ and NO3−) release from sediment by in situ techniques, and a part of NH4+ converted into NO3− during their flow into the overlying water through the nitrification affected by AOB. Furthermore, the main depth of bioturbation influence is approximately 12 cm below the SWI and the most significant bioturbation effect was observed from days 15 to 25.

Greenhouse gas released from the deep permafrost in the northern Qinghai-Tibetan Plateau

Deep carbon pool in permafrost regions is an important component of the global terrestrial carbon cycle. However, the greenhouse gas production from deep permafrost soils is not well understood. Here, using soils collected from 5-m deep permafrost cores from meadow and wet meadow on the northern Qinghai-Tibetan Plateau (QTP), we investigated the effects of temperature on CO2 and N2O production under aerobic incubations and CH4 production under anaerobic incubations. After a 35-day incubation, the CO2, N2O and CH4 production at −2 °C to 10 °C were 0.44~2.12 mg C-CO2/g soil C, 0.0027~0.097 mg N-N2O/g soil N, and 0.14~5.88 μg C-CH4/g soil C, respectively. Greenhouse gas production in deep permafrost is related to the C:N ratio and stable isotopes of soil organic carbon (SOC), whereas depth plays a less important role. The temperature sensitivity (Q10) values of the CO2, N2O and CH4 production were 1.67–4.15, 3.26–5.60 and 5.22–10.85, without significant differences among different depths. These results indicated that climate warming likely has similar effects on gas production in deep permafrost and surface soils. Our results suggest that greenhouse gas emissions from both the deep permafrost and surface soils to the air will increase under future climate change.