Although nitrous oxide (N2O) emissions from composting contribute to the accelerated greenhouse effect, it is difficult to implement practical methods to mitigate these emissions. In this study, the ...effects of biochar amendment during pig manure composting were investigated to evaluate the inter-relationships between N2O emission and the abundance of denitrifying bacteria. Analytical results from two pilot composting treatments with (PWSB, pig manure + wood chips + sawdust + biochar) or without (PWS, pig manure + wood chips + sawdust) biochar (3% w/w) demonstrated that biochar amendment not only lowered NO2 –-N concentrations but also lowered the total N2O emissions from pig manure composting, especially during the later stages. Quantification of functional genes involved in denitrification and Spearman rank correlations matrix revealed that the N2O emission rates correlated with the abundance of nosZ, nirK, and nirS genes. Biochar-amended pig manure had a higher pH and a lower moisture content. Biochar amendment altered the abundance of denitrifying bacteria significantly; less N2O-producing and more N2O-consuming bacteria were present in the PWSB, and this significantly lowered N2O emissions in the maturation phase. Together, the results demonstrate that biochar amendment could be a novel greenhouse gas mitigation strategy during pig manure composting.
Heavy metals removal from aqueous phase by adsorption technique has recently attracted a considerable interest. Although various adsorbing materials have been developed, introducing more functional ...groups is considered as the most efficient way to promote the adsorption capacity of the selected adsorbent. However, this approach is usually limited in costly modification precursor and unguaranteed loading efficacy. In this study, waste corn straw was converted to adsorbent precursor by hydrothermal carbonization. The obtained hydrochar (HC) was chemically activated before being modified by polyethyleneimine (PEI). Multiple analysis methods including Scanning Electron Microscopy, Fourier Transform Infrared analysis, and X-ray Photoelectron Spectroscopy analysis verified the alkali activated hydrochar (alkali-HC) was more efficacy to enhance PEI grafting than acid activation. Based on this, the modified HC materials obtained a better adsorption performance. The sorption process of Cu(II) and Zn(II) on the acid-PEI-HC, alkali-PEI-HC, and pristine HC fitted the pseudo second order kinetic and Freundlich model well, and was dominated by chemisorption. Among these adsorbents, the adsorption capacity of alkali-PEI-HC to metal ions was the maximum, which was 207.6 mg/g to Zn(II) and 56.1 mg/g to Cu(II) at 298 K. Regeneration tests showed a result of no less than 60% of its removal capacity was achieved after five cycles. Therefore, alkali-PEI-HC performed as a promising composite sorbent for metal ions. In addition, the study described here has provided a new basis for the utilization of hydrochar (1.08 kWh kg−1) derived from agricultural resources as a promising adsorbent precursor.
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•Desired hydrochars after acid/alkali activation and PEI loading were synthesized.•Higher Cu(II) and Zn(II) adsorption ability was obtained by alkali-PEI-HC.•Energy of straws converted into hydrochar precursor was consumed as 1.08 kWh kg−1.
Purpose
Forests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative ...impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils.
Materials and methods
This review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils.
Results and discussion
Biochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N
2
O emissions, increasing soil CH
4
uptake, and complex (negative, positive, or negligible) changes of soil CO
2
emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific.
Conclusions
The application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.
•Biochar application decreased the concentration of extractable Cd, Cu, Pb and Zn.•Bamboo biochar was more effective than rice straw biochar in reducing the bioavailability of Cd.•Straw biochar was ...more effective than bamboo biochar in reducing the bioavailability of Cu, Pb and Zn.•Fine biochar was more effective than coarse biochar in reducing Zn concentration in plant shoots.
Soil contamination with heavy metals has become a global concern because of its adverse effects on ecosystem health and food security. Soil amendments including biochar can reduce the bioavailability of heavy metals in contaminated soils and reduce their risk of entering the food chain. A pot experiment was conducted to investigate the effects of biochars derived from bamboo and rice straw on bioavailability and plant growth in a sandy loam paddy soil naturally co-contaminated with Cd, Cu, Pb and Zn. The soil was moderately acidic (pH=5.7) and low in organic carbon content (8.7gkg−1). Bamboo and rice straw biochars, pyrolyzed at temperatures≥500°C and with two mesh sizes (< 0.25mm and<1mm), were applied at three rates (0, 1% and 5%, w/w). A metal-tolerant plant, Sedum plumbizincicola X. H. Guo et S. B. Zhou sp. nov. was used in the plant growth experiment to examine the bioavailability of these metals. The addition of biochars to soil significantly (p<0.05) increased the above-ground biomass of S. plumbizincicola. By the end of the experiment, soils amended with biochar had pH values significantly (p<0.05) higher, this effect being more accentuated at the high biochar dose and small particle size. The solubility of Cd, Cu, Pb, and Zn as measured by Toxicity Characteristic Leaching Procedure (TCLP) was significantly lower (p<0.05) in the biochar-amended soils than in the control soil. This was paralleled by significant reductions in Cd, Cu, Pb and Zn accumulated in the above-plant biomass of amended soils. Rice straw biochar reduced the concentration of Cu and Pb in the shoots by 46 and 71%, while bamboo biochar reduced concentration of Cd in the shoot by 49%. Finer biochar was more effective on reducing the concentrations of Zn in shoot than the coarse ones, while particle size had no effect on the concentrations of Cd, Cu and Pb in the shoot of S. plumbizincicola. In conclusion, the influence of biochar on heavy metal bioavailability varied not only with the feedstock and application rate of biochars, but also with the metal species. Therefore, biochar should be carefully designed to maximize the reduction of the bioavailability of a given heavy metal in soil.
Pyrolysis of rice straw to create biochar for soil amendment appears to be a promising method to address concerns with regard to improving soil fertility, increasing Carbon storage and decreasing ...Green House Gas emissions. However, the ability of rice straw-derived biochar to affect these factors might vary depending on its characteristics. It is therefore essential to investigate the properties before large-scale application of rice straw-derived biochar. In this study, rice straw-derived biochars produced at different temperatures (300, 400, 500, 600 & 700 °C) and residence time (1, 2, 3 & 5 h) were characterized using a suite of analytical techniques. Results showed that pyrolysis temperature had a greater influence than residence time on the chemical composition and structure of rice straw-derived biochar produced at low heating rate. The rice straw-derived biochars especially produced at 400 °C had high alkalinity and cation exchange capacity, and high levels of available phosphorus and extractable cations. These properties indicate potential application of rice straw-derived biochar as a fertilizer and soil amendment. Fourier transform infrared spectra showed that higher pyrolysis temperatures promote condensation reactions. Rice straw-derived biochars contained turbostratic crystallites at 400 °C, and displayed a high level of aromatization at 500 °C. Increasing charring temperature will increase the aromaticity of biochar, and might include its recalcitrance.
► Pyrolysis temperature played a significant role in rice straw biochar properties. ► Rice straw biochars had high alkalinity, cation exchange capacity and available P. ► Rice straw biochar yielded at 400 °C might be more suitable for soil amendment. ► Rice straw biochar displayed a high level of aromatization at 500 C.
The reduced human activities and associated decreases in aerosol emissions during the COVID‐19 pandemic are expected to affect climate. Assuming emission changes during lockdown, back‐to‐work and ...post‐lockdown stages of COVID‐19, climate model simulations show a surface warming over continental regions of the Northern Hemisphere. In January–March, there was an anomalous warming of 0.05–0.15 K in eastern China, and the surface temperature increase was 0.04–0.07 K in Europe, eastern United States, and South Asia in March–May. The longer the emission reductions undergo, the warmer the climate would become. The emission reductions explain the observed temperature increases of 10–40% over eastern China relative to 2019. A southward shift of the ITCZ is also seen in the simulations. This study provides an insight into the impact of COVID‐19 pandemic on global and regional climate and implications for immediate actions to mitigate fast global warming.
Key Points
Aerosol emission scenarios are produced for lockdown, back‐to‐work, and post‐lockdown stages during COVID‐19 to study fast climate responses
An anomalous surface warming appears over the Northern Hemisphere continents in response to aerosol reductions
The COVID‐19 emission reduction explains the observed 2019‐to‐2020 temperature increase by 10–40% over eastern China
Correlation between molecular structures and slow relaxation of magnetization of three mixed (phthalocyaninato)(porphyrinato) dysprosium(III) double-deckers clearly reveals the effect of the ...sandwich-type molecular structure, in particular the twist angle, on the quantum tunneling (QT) at zero dc field of these complexes, providing the first direct evidence to the theoretical inference.
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