121. 题目: Abiotic plastic leaching contributes to ocean acidification
Ocean acidification and plastic pollution are considered as potential planetary boundary threats for which crossing certain thresholds could be very harmful for the world's societies and ecosystems well-being. Surface oceans have acidified around 0.1 units since the Industrial Revolution, and the amount of plastic reaching the ocean in 2018 was quantified to 13 million metric tonnes. Currently, both ocean threats are worsening with time. Plastic leaching is known to alter the biogeochemistry of the ocean through the release of dissolved organic matter. However, its impact in the inorganic chemistry of the seawater is less studied. Here we show, from laboratory experiments, that abiotic plastic degradation induces a decrease in seawater pH, particularly if the plastic is already aged, as that found in the ocean. The pH decrease is enhanced by solar radiation, and it is probably induced from a combination of the release of organic acids and the production of CO2. It is also related to the amount of leached dissolved organic carbon, with higher acidification as leaching increases. In coastal areas, where plastic debris accumulates in large quantities, plastic leaching could lead to a seawater pH decrease up to 0.5 units, comparable to the projected decrease induced in surface oceans by the end of the twenty-first century for the most pessimistic anthropogenic emissions scenarios.
122. 题目: Is the transactional carbon credit tail wagging the virtuous soil organic matter dog?
Nature-based solutions are gaining momentum as approaches to address major environmental challenges, including markets for soil carbon (C) sequestration for mitigating climate change. This special collection of papers, stemming from a symposium of the 2021 Fall Meeting of the American Geophysical Union, poses several tough questions about the practical potential for significant C sequestration resulting from farmer participation in carbon markets. A common theme among these papers is that promotion of soil C sequestration through carbon markets has likely gotten ahead of the agronomic and biogeochemical science and especially the social science. We know a great deal about soil C dynamics and stabilization, but we know less about translating that knowledge to market-based solutions that have inherent challenges of validating sequestration rates and other potential pitfalls. Scientists can help provide rigor to carbon markets, although they must maintain objectivity and avoid conflicts of interests with well-intended evolving markets. Even when there is strong scientific support for the feasibility and the virtues of best management practices that provide numerous co-benefits while building soil organic matter, socio-economic barriers to farmer adoption remain poorly understood. Although soil markets currently focus almost exclusively on C, mitigation of methane and nitrous oxide emissions from agriculture could offer several advantages as well as challenges. The papers in this special collection offer a needed perspective urging soil scientists, biogeochemists, and social scientists to step up and offer honest appraisals of what is most likely to work, or not, and why.
123. 题目: Field-aged biochar enhances soil organic carbon by increasing recalcitrant organic carbon fractions and making microbial communities more conducive to carbon sequestration
Biochar has been widely proposed for carbon (C) sequestration, but its residual effects on soil organic C (SOC) accumulation and microbial characteristics are unknown. Herein, we investigated the content and components of organic C, and the abundance and community characteristics of microbes in a fluvo-aquic soil, after 4 years of biochar application at rates of 3, 6 and 12 t ha−1. Biochar application increased the contents of SOC and recalcitrant organic C fraction by 11.02–22.13 % and 18.41–32.31 % at 6 and 12 t ha−1, respectively, and the increased proportion for recalcitrant organic C fraction was greater than that for SOC. Among C functional groups, aryl C content was increased by 26.50–95.41 % at all rates, compared with 23.83–56.73 % for phenolic C at 6 and 12 t ha−1, and both increases were higher than that for SOC. Biochar application decreased bacterial abundance by 9.25–35.77 %, and altered bacterial community structure by increasing the relative abundance of Chloroflexi phylum, members of which have a low C mineralisation rate and strong C fixation ability. Dissolved organic C was the most critical factor of bacterial abundance and community structure. By contrast, 12 t ha−1 biochar application decreased fungal diversity by 12.45 %, and altered fungal community structure by increasing the relative abundances of Sordariomycetes and Tremellomycetes classes, both of which favoured SOC formation. The C/N ratio was the most important variable affecting fungal diversity and community structure. Overall, our results suggest that field-aged biochar, especially at a high-dose rate, accelerates organic C accumulation by increasing aryl and phenolic C functional groups of recalcitrant organic C fractions and shifting microbial communities more conducive to C sequestration in the fluvo-aquic soil.
124. 题目: Controls on vertical distribution of organic carbon in the intermontane valley soils (Barak, Northeast India)
The Intermontane valleys interspersed with rugged landscapes represent a unique ecosystem and are the barn of the eastern Himalayas (EH). Soil organic carbon (SOC) plays an important role in controlling cropland productivity in these valleys. Despite this, very little is known about SOC inventories (content and stocks) and their complex interplay with some of the major control factors such as climate, elevation, land use, parent materials, and soil properties. Therefore, the objective of this study was to assess the relative influence of heterogeneous control factors (PL: Parent materials and land use) on the vertical distribution of SOC inventories at a homogeneous climate and altitude. For the study, I choose one of the largest but largely unexplored intermontane valleys (Barak) of the eastern Himalayas. By exposing a total of 72 profiles to the C horizon or water table, a thorough analysis of the influence of PL on SOC inventories (Dichromate oxidizable) and key soil parameters controlling vertical distribution of SOC in valley soils were determined The measured SOC content in the surface soil (0.15–0.24 m deep) varied from 0.91% to 1.42%, while in the soil profile (up to a depth from 1.19 to 1.56 m), the SOC content (PWA: profile weighted average) ranged from 0.60% to 0.97%. The surface layer represented only 15% soil profile depth, while contributing 33% of the SOC content (Dichromate oxidizable). The variation in SOC content (PWA) was higher among soil parent materials (e.g. Alluvium, pebble bedded-sandstone, sandstone intercalated with shale, and pure shale, CV> 16.0%) than in land use systems (e.g. Paddy agriculture, forest, and plantation, CV <3.0%). The SOC stock on the soil profile (PWA) ranged from 19.4 to 36.0 Mg ha−1. The total (soil profile) SOC stock varied from 67.5 to 161.1 Mg ha−1. In general, the SOC inventories increased relative to the clay content (correlation, r = 0.38–0.75, p < 0.05) and parent materials controlled the variation in surface and subsurface soils while the effect of land use was mostly limited to surface soils only. Deep soils (>1.55 m) developed on shale with higher clay content had higher SOC inventories (p < 0.05) than coarse-textured sandstone soils. Parent materials contributed to greater heterogeneity (R2adj = 77.1%) in SOC inventories compared to land use systems (R2adj = 61.7%). Therefore, in addition to land use, parent materials should be considered an important control factor in the estimation of SOC inventories and future research on C- sequestration in the intermontane valleys.
125. 题目: Towards the outwelling hypothesis in a Patagonian estuary: First support from lipid markers and bacterial communities
Biogeochemical markers in combination with bacterial community composition were studied at two contrasting stations at the Río Negro (RN) estuary to assess the outwelling hypothesis in the Argentinian Patagonia. Inorganic nutrients and dissolved organic matter were exported clearly during the last hours of the ebb at the station Wetland. Moreover, a considerable outwelling of polyunsaturated fatty acids (PUFA), particulates and microalgae was inferred by this combined approach. The exported 22:6(n-3) and 20:5(n-3) contributed very likely to sustain higher trophic levels in the coasts of the Southwest Atlantic. The stable isotopes did not evidence clearly the outwelling; nevertheless, the combination of δ13C with fatty acid bacterial markers indicated organic matter degradation in the sediments. The dominance of Desulfobacterales and Desulfuromonadales suggested sulphate reduction in the sediments, a key mechanism for nutrient outwelling in salt marshes. Marivivens and other Rhodobacterales (Alphaproteobacteria) in the suspended particulate matter were clear indicators of the nutrient outwelling. The colonization of particles according to the island biogeography theory was a good hypothesis to explain the lower bacterial biodiversity at the wetland. The copiotrophic conditions of the RN estuary and particularly at the wetland were deduced also by the dynamic of some Actinobacteria, Bacteroidia and Gammaproteobacteria. This high-resolution snapshot combining isotopic, lipid and bacterial markers offers key pioneer insights into biogeochemical and ecological processes of the RN estuary.
126. 题目: Transformation of dissolved organic matter by two Indo-Pacific sponges
127. 题目: Interactions between organic matter and Fe oxides at soil micro-interfaces: Quantification, associations, and influencing factors
Iron (Fe) oxides are widely recognized to prevent the degradation of organic matter (OM) in environments, thereby promoting the persistence of organic carbon (OC) in soils. Thus, discerning the association mechanisms of Fe oxides and OC interactions is key to effectively influencing the dynamics and extent of organic C cycling in soils. Previous studies have focused on i) quantifying Fe oxide-bound organic carbon (Fe-OC) in individual environments, ii) investigating the distribution and adsorption capacity of Fe-OC, and iii) assessing the redox cycling and transformation of Fe-OC. Furthermore, the widespread application of high-tech instrumentation and methods has greatly contributed to a better understanding of the mechanism of organic mineral assemblages in the past few decades. However, few literature reviews have comprehensively summarized Fe-OC distributions, associations, and characteristics in soil-plant systems. Here, studies investigating the Fe-OC contents among different environments are reviewed. In addition, the mechanisms and processes related to OM transformation dynamics occurring at mineral-organic interfaces are also described. Recent studies have highlighted that diverse interactions occur between Fe oxides and OC, with organic compounds adhering to Fe oxides due to their huge specific surfaces area and active reaction sites. Moreover, we also review methods for understanding Fe-OC interactions at micro-interfaces. Lastly, developmental prospects for understanding coupled Fe-OC geochemical processes in soil environments at molecular- and nano-scales are outlined. The summary suggests that combined advanced techniques and methods should be used in future research to explore micro-interfaces and in situ descriptions of organic mineral assemblages. This review also suggests that future studies need to consider the functional and spatial complexity that is typical of soil/sediment environments where Fe-OC interactions occur.
128. 题目: An integrated straw-tillage management increases maize crop productivity, soil organic carbon, and net ecosystem carbon budget
Soil carbon sequestration is widely considered to improve soil quality, safeguard food security, and mitigate climate change. However, the effect of best management practices like conservation tillage on soil carbon sequestration remains unclear. A 3-year field experiment was conducted to explore the effect of integrated straw-tillage systems (conventional rotary tillage, CT; no-tillage, NT; CT with straw retention, CT-SR; NT with straw retention, NT-SR) on maize productivity, soil organic carbon (SOC), and net ecosystem carbon budget (NECB) in Southwest China. The results indicate that the CT-SR achieved the highest grain yield (9.1 Mg ha-1) and aboveground biomass (19.0 Mg ha-1). Averaged grain yield and aboveground biomass of the two systems without straw retention, CT and NT, were, respectively, 4.5 % and 4.1 % lower than those with straw retention. The NT-SR and CT-SR achieved the highest SOC concentration, 12.3 g kg-1 and 11.9 g kg-1, respectively, as well as the highest SOC stock and the annual increase in SOC and SOC stock. The highest NECB was observed in NT-SR, which was not significantly different from those of CT-SR and CT, but was higher than that of NT by 13.1 %. Higher SOC sequestration was the major contributor to the NECB of NT-SR, while higher gross primary productivity and harvest carbon removal contributed mostly to NECB of CT-SR and CT. A combination of straw retention and NT was more positive than that with CT for the continued rise in SOC sequestration. The NT system was inferior to others for improving the system productivity and NECB, especially when comparing with CT-SR. In summary, the integrated straw retention and rotary tillage (CT-SR) achieved the highest system productivity, while the NT-SR was superior for SOC sequestration and NECB than other systems for maize production in the Southwest China. An integrated straw-tillage management is therefore an efficient and feasible way to maintain high maize productivity and carbon sustainability.
129. 题目: Unravelling relationships between fluorescence spectra, molecular weight distribution and hydrophobicity fraction of dissolved organic matter in municipal wastewater
The characteristics of dissolved organic matter (DOM) in the influent and secondary effluent from 6 municipal wastewater treatment plants (WWTPs) were investigated with a size exclusion chromatogram (SEC) coupled with multiple detectors to simultaneously detect ultraviolet absorbance, fluorescence, dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) as a function of molecular weight (MW). The SEC chromatograms showed that biopolymers (>6 kDa) and humic substances (0.5–6 kDa) comprised the significant fraction in the influent, while humic substances became the abundant proportion in the secondary effluent. Direct linkages between MW distribution and hydrophobicity of DOM in the secondary effluent were further explored via SEC analysis of XAD resin fractions. DON and DOC with different hydrophobicity exhibited significantly distinct MW distribution, indicating that it was improper to consider DOC as a surrogate for DON. Different from DOC, the order of averaged MW in terms of DON was hydrophobic neutral ≈ transphilic neutral > hydrophobic acid > transphilic acid > hydrophilic fraction. Fluorescence spectral properties exhibited a significant semi-quantitative correlation with MW and hydrophobicity of DOC, with Pearson's coefficients of −0.834 and 0.754 (p < 0.01) for biopolymer and humic substances. Meanwhile, regional fluorescence proportion was demonstrated to indicate the MW and hydrophobicity properties of DON at the semi-quantitative level. The fluorescence excitation-emission matrix (EEM) could be explored to provide a rapid estimation of MW distribution and hydrophobic/hydrophilic proportion of DOC and DON in WWTPs.
130. 题目: Comparison of cadmium adsorption by hydrochar and pyrochar derived from Napier grass
Biochar (e.g. pyrochar and hydrochar) is considered a promising adsorbent for Cd removal from aqueous solution. Considering the vastly different physicochemical properties between pyrochar and hydrochar, the Cd2+ sorption capacity and mechanisms of pyrochars and hydrochars should be comparatively determined to guide the production and application of biochar. In this study, the hydrochars and pyrochars were prepared from Napier grass by hydrothermal carbonization (200 and 240 °C) and pyrolysis (300 and 500 °C), respectively, and the physicochemical properties and Cd2+ sorption performances of biochars were systematically determined. The pyrochars had higher pH and ash content as well as better stability, while the hydrochars showed more oxygen-containing functional groups (OFGs) and greater energy density. The pseudo second order kinetic model best fitted the Cd2+ sorption kinetics data of biochars, and the isotherm data of pyrochar and hydrochar were well described by Langmuir and Freundlich models, respectively. In comparison with hydrochar, the pyrochar exhibited better Cd2+ sorption capacity (up to 71.47 mg/g). With increasing production temperature, the Cd2+ sorption capacity of pyrochar elevated, while the reduction was found for hydrochar. The mineral interaction, complexation with surface OFGs, and coordination with π electron were considered the main mechanisms of Cd2+ removal by biochars. The minerals interaction and the complexation with OFGs was the dominant mechanism of Cd2+ removal by pyrochars and hydrochars, respectively. Therefore, the preparation technique and temperature have significant impacts on the sorption capacity and mechanisms of biochar, and pyrochar has better potential for Cd2+ removal than the congenetic hydrochar.
131. 题目: Green synthesis of porous biochar with interconnected pore architectures from typical silicon-rich rice husk for efficient CO2 capture
Carbon capture is an effective solution to reduce the emitted CO2 from the burning of fossil fuels. However, the intrinsic tradeoff between activator selection and narrow pores for CO2 capture, as well as the difficult design of pores according to the biomass natural structure, greatly limits the CO2 capture capacity. To overcome those issues, for the first time, porous biochar with precisely narrow pores (0.36 and 0.59 nm) and nanocapsules structure was assembled by coupling the merit of typical silicon-rich waste rice husk and low-corrosive potassium citrate for CO2 adsorption application. The narrow ultramicropore was obtained and verified by CO2 and N2 molecular probes. Potassium citrate activated biochar exhibited an excellent gravimetric CO2 capture capacity of 1.55 mmol/g, which was 1.35 and 2.04 times higher than potassium citrate self-assembled and KOH-activated samples, respectively. The as-synthesized potassium citrate activated biochar exhibited high CO2/N2 selectivity of 37.80 (1 bar, 25°C) and regeneration efficiencies above 99% after 10 cycles. In combination with TG-FTIR, SEM and XRD, key CO2 capture mechanisms were proposed: 1) CO2 is encapsulated in the nanocapsules structure (∼1 μm) and enters the interior carbon matrix skeleton with narrow ultra-micropores (Vultra=0.213 cm3/g); 2) CO2 tend to be absorbed in interconnected channel formed by tailoring the external SiO2 nanoparticles and internal organic carbon. This strategy could provide a new insight to guide the pores design according to biomass natural structure for efficient CO2 capture.
132. 题目: Batch and fixed bed sorption of low to moderate concentrations of aqueous per- and poly-fluoroalkyl substances (PFAS) on Douglas fir biochar and its Fe3O4 hybrids
Per- and poly-fluoroalkyl substances (PFAS) can cause deleterious effects at low concentrations (70 ng/L). Their remediation is challenging. Aqueous μg/L levels of PFOS, PFOS, PFOSA, PFBS, GenX, PFHxS, PFPeA, PFHxA, and PFHpA (abbreviations defined in Table 1) multi-component adsorption (pH dependence, kinetics, isotherms, fixed-bed adsorption, regeneration, complex matrix) was studied on commercial Douglas fir biochar (BC) and its Fe3O4-containing BC. BC is a waste product when syn-gas is produced in a large scale from wet Douglas fir wood fed to gasification at 900–1000 °C and held for 1–20 s. This generates a relatively high surface area (∼700 m2/g) and large pore volume (∼0.25 cm3/g) biochar. Treatment of BC with FeCl3/FeSO4 and NaOH to chemically precipitate Fe3O4 onto BC. BC and its magnetic Fe3O4/BC analogue rapidly adsorbed (20–45 min equilibrium time) significant amounts of PFOS (∼14.6 mg/g) and PFOA (∼652 mg/g) at natural waters’ pH range (6–8). Adsorption from μg/L concentrations has produced remediated aqueous PFAS concentrations of ∼50 ng/L or below the detection limits, which is closing in on EPA advisory limits. Column capacities of PFOS were 215.3 mg/g on BC and 51.9 mg/g Fe3O4/BC vs 53.0 mg/g and 21.8 mg/g, respectively, for PFOA. Hydrophobic and electrostatic interactions are thought to drive this sorption. Successful stripping regeneration by methanol was achieved. Thus, hydrophobic Douglas fir biochar produced by fast high temperature pyrolysis and its Fe3O4/BC analogue are adsorbent candidates for PFAS remediation from the dilute PFAS concentrations often found in polluted environments. Small Fe3O4/BC particles can be magnetically removed from batch treatments avoiding filtration.
133. 题目: The effect of shrublands degradation intensity on soil organic matter-associated properties in a semi-arid ecosystem
Vegetation degradation can have significant effects on organic matter fractions as well as various soil characteristics. All these can lead to the changes in soil microbial communities, which are main drivers of nutrient cycles. This is especially important for mountainous ecosystems that are very sensitive and fragile habitats due to their climatic conditions, but less attention has been paid to them. Thus, Mirkola mountainous region (northern Iran) with semi-arid climate and vegetation being dominated by Crataegus and Berberis shrubs were investigated in this study. Sites with different intensities of vegetation degradation [light (60–70 % coverage), moderate (30–40 % coverage) and heavy (0–10 % coverage)] and also non-degraded control sites (90–100 % coverage) were selected. In order to avoid pseudoreplication, three plots, each with an area of 1 ha (100 m × 100 m), were used for each of the four studied habitats. Soil (in three soil depths at 0–10 cm, 10–20 cm and 20–30 cm) samples were collected from the corners and also the center (n = 5) of the plots using iron frames (30 × 30 cm). A total of 180 soil samples (4 habitats × 15 sample × 3 depths) were transferred to the laboratory. Labile and non-labile contents of soil organic matter (SOM) (C and N in soil particles and aggregates, C and N stocks, particulate and dissolved organic matter, hot-water extractable carbohydrate, C and N mineralization) were measured in each of these sites. Results showed that vegetation degradation might result in both labile and non-labile SOM losses. SOM and its associated properties were highest in the non-degraded sites, whereas, lower values were common under degraded areas. Based on the obtained data, vegetation cover can enhance the amount of organic matter entering the soil (especially in the surface layers) and formation of fertile islands in ecosystems. Accordingly, vegetation protection is emphasized to maintain stability and provide ecosystem services in mountainous semi-arid regions.
134. 题目: Vertical distributions of atmospheric black carbon in dry and wet seasons observed at a 356-m meteorological tower in Shenzhen, South China
Black carbon (BC) is a vital climate forcer in the atmosphere, but measurements of BC vertical profiles near the surface remain limited. This study investigates time-resolved vertical profiling of BC in both dry (December 2017) and wet (August 2018) seasons in Shenzhen, China, at a 356-m meteorological tower. In the dry season, five micro-aethalometers were deployed at different heights (2, 50, 100, 200, and 350 m), while four heights (2, 100, 200, and 350 m) were measured in the wet season. The concentrations of equivalent BC (eBC) showed a decreasing trend with altitude in the dry season, while a weaker vertical gradient was observed in the wet season. The diurnal variability of eBC in the dry season is also more significant than in the wet season. Correlation analysis between eBC concentrations at the ground and those at the upper levels suggest a better vertical mixing of eBC in the wet season than in the dry season. In the wet season when south wind prevailed, eBC concentration at ground level was likely reduced by the large amount of vegetation cover south to the sampling site. In the dry season, eBC concentrations at 350 m show little dependence on wind speed, implying that local emissions have a limited effect on eBC concentrations at 350 m. In the wet season when brown carbon influence was weak, higher wind speed leads to a higher Ångström exponent (AAE) at 350 m, likely associated with more aged BC particles. Cluster analysis of backward trajectories suggests that high eBC concentration was associated with air masses from Central China in both seasons. This study provides a better understanding on the influencing factors that affect the vertical distributions of BC in the lower part of the boundary layer.
135. 题目: Composition of dissolved organic matter (DOM) in lakes responds to the trophic state and phytoplankton community succession
Dissolved organic matter (DOM), a heterogeneous mixture of diverse compounds with different molecular weights, is crucial for the lake carbon cycle. The properties and concentration of DOM in lakes are closely related to anthropogenic activities, terrigenous input, and phytoplankton growth. Thus, the lake's trophic state, along with the above factors, has an important effect on DOM. We determined the DOM sources and molecular composition in six lakes along a trophic gradient during and after phytoplankton bloom by combining optical techniques and the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). CDOM pools in eutrophic lakes may be more biologically refractory than in oligotrophic and mesotrophic lakes. Molecular formulas of DOM were positively correlated with the TSI (trophic state index) value (R2=0.73), with the nitrogen-containing compounds (CHON) being the most abundant formulas in all studied lakes. Eutrophication modified the molecular formulas of DOM to have less CHO% and more heteroatom S-containing compounds (CHOS% and CHNOS%), and this was the synactic result of the anthropogenic perturbation and phytoplankton proliferation. In eutrophic lakes, summer DOM showed higher molecular lability than in autumn, which was related to the seasonal phytoplankton community succession. Although the phytoplankton-derived DOM is highly bioavailable, we detected a simpler and more fragile phytoplankton community ecosystem in autumn, which may be accompanied by a lower phytoplankton production and metabolic activity. Therefore, we concluded that the lake eutrophication increased the allochthonous DOM accumulation along with sewage and nutrient input, and subsequently increased its release with phytoplankton bloom. Eutrophication and phytoplankton growth are accompanied by more highly unsaturated compounds, O3S+O5S compounds, and carboxylic-rich alicyclic compounds (CRAMs), which are the biotransformation product of phytoplankton-derived DOM. Eutrophication may be a potential source of refractory DOM compounds for biodegradation and photodegradation. Our results can clarify the potential role of water organic matter in the future global carbon cycle processes, considering the increasing worldwide eutrophication of inland waters.
136. 题目: Effect of carrier gas during pyrolysis on the persistence and bioavailability of polycyclic aromatic hydrocarbons in biochar-amended SOIL
In this study the persistence (based on extractable, Ctot) and bioavailability (based on freely dissolved content, Cfree) of polycyclic aromatic hydrocarbons (PAHs) in biochar-amended soil was investigated. Biochar produced at 500 or 700 °C from sewage sludge (BC) or sewage sludge and willow (W) mixture (BCW) in an atmosphere of nitrogen (N2) or carbon dioxide (CO2) was evaluated. The biochars were applied to the real soil (podzolic loamy sand) at a dose of 2% (w/w). The content of Ctot and Cfree PAHs was monitored for 180 days. The biochar production conditions determined the Ctot and Cfree PAHs in the soil. A change of carrier gas from N2 to CO2 caused an increase in Ctot PAH losses in the soil from 19 to 75% for the biochar produced from SL and from 49 to 206% for the co-pyrolyzed biochar. As regards Cfree PAHs, the change from N2 to CO2 increased the losses of Cfree PAHs only for the biochar derived from SL at a temperature of 500 °C (by 21%). In the soil with the other biochars (produced at 700 °C from SL as well as at 500 and 700 °C from SL/W), the Cfree increased from 17 to 26% compared to the same biochars produced in an atmosphere of N2.
137. 题目: The advanced treatment of textile printing and dyeing wastewater by hydrodynamic cavitation and ozone: Degradation, mechanism, and transformation of dissolved organic matter
The emission standards for textile printing and dyeing wastewater are stricter due to serious environmental issues. A novel technology, hydrodynamic cavitation combined with ozone (HC + O3), has attracted wide attention in wastewater advanced treatment, whereas the contaminants removal mechanism and transformation of dissolved organic matter (DOM) were rarely reported. This study investigated the removal efficiency and mechanism of HC + O3. The maximum removal rates of UV254, chrominance, CODCr, and TOC were 64.99%, 91.90%, 32.30%, and 36.67% in 60 min, respectively, at the inlet pressure of 0.15 MPa and O3 dosage of 6.25 mmol/L. The synergetic coefficient of HC + O3 was 2.77. The removal of contaminants was the synergy of 1O2, ·OH and , and high molecular weight and strong aromaticity organic matters were degraded effectively. The main components in DOM were tryptophan-like and tyrosine-like, which were effectively removed after HC + O3. Meanwhile, most DOM had decreased to low apparent relative molecular weight (LARMW) compounds. Additionally, the HC + O3 effluent can reach the emission standard in 60 min for 8.07 USD/m3. It can be concluded that HC + O3 is an effective technology for the advanced treatment of industrial wastewater. This study will provide suggestions for the engineering application of HC + O3.
138. 题目: Biochar application for greenhouse gas mitigation, contaminants immobilization and soil fertility enhancement: A state-of-the-art review
Rising global temperature, pollution load, and energy crises are serious problems, recently facing the world. Scientists around the world are ambitious to find eco-friendly and cost-effective routes for resolving these problems. Biochar has emerged as an agent for environmental remediation and has proven to be the effective sorbent to inorganic and organic pollutants in water and soil. Endowed with unique attributes such as porous structure, larger specific surface area (SSA), abundant surface functional groups, better cation exchange capacity (CEC), strong adsorption capacity, high environmental stability, embedded minerals, and micronutrients, biochar is presented as a promising material for environmental management, reduction in greenhouse gases (GHGs) emissions, soil management, and soil fertility enhancement. Therefore, the current review covers the influence of key factors (pyrolysis temperature, retention time, gas flow rate, and reactor design) on the production yield and property of biochar. Furthermore, this review emphasizes the diverse application of biochar such as waste management, construction material, adsorptive removal of petroleum and oil from aqueous media, immobilization of contaminants, carbon sequestration, and their role in climate change mitigation, soil conditioner, along with opportunities and challenges. Finally, this review discusses the evaluation of biochar standardization by different international agencies and their economic perspective.
139. 题目: Tree species richness and N-fixing tree species enhance the chemical stability of soil organic carbon in subtropical plantations
Tree species diversity enhances productivity and soil carbon storage in subtropical forests. However, the effects of tree species diversity and N-fixing tree species on the chemical stability of soil organic carbon (SOC) have been poorly understood. In this study, a manipulative experiment involving varying tree species richness (i.e., one, two, four and six species) and the inclusion of N-fixing trees was conducted to investigate the effects of tree species richness and the presence of N-fixing tree species on the chemical stability of SOC. Biological traceability was used to separate SOC into plant-vs. microbial-derived components, and then assessed by four measures of the chemical stability, including the cyclic/acyclic lipid ratio, average carbon chain length (ACL), Pielou's evenness of acyclic lipids and Pielou's evenness of cyclic lipids. We found that tree species richness was positively correlated with the cyclic/acyclic lipid ratio, ACL and evenness of acyclic lipids. In the presence of N-fixing tree species, tree species richness significantly increased both plant- and microbial-derived lipids, resulting in a higher cyclic/acyclic lipid ratio through stimulated root-microorganism interactions. Plant-derived lipids were positively correlated with the cyclic/acyclic lipid ratio, ACL and evenness of acyclic lipids, suggesting the important role of plant-derived components in shaping the chemical stability of SOC. This study reveals that the chemical stability of SOC is not only a function of tree species richness, but also manifested by the presence of N-fixing tree species. These results demonstrate that mixed plantations with N-fixing trees as an appropriate silvicultural option will be beneficial to the enhancement of the chemical stability of SOC through increased soil recalcitrant C components.
140. 题目: Long-term immobilization of cadmium and lead with biochar in frozen-thawed soils of farmland in China
The problem of potentially toxic elements (PTEs) in farmland is a key issue in global pollution prevention and control and has an important impact on environmental safety, human health, and sustainable agricultural development. Based on the climate background of high–latitude cold regions, this study simulated freeze–thaw cycles through indoor tests. Different initial conditions, such as biochar application rates (0%, 1%, 2%) and different initial soil moisture contents (15%, 20%, 25%), were set to explore the morphological changes in cadmium (Cd) and lead (Pb) in soil and the response relationship to the changes in soil physicochemical properties. The results indicate that soil pH decreases during freeze–thaw cycles, and soil alkalinity increases with increasing biochar content. Freeze–thaw cycles caused the total amount of PTEs to have a U–shaped distribution, and the amount of PTEs in the soluble (SOL) and reducible (RED) fraction increased by 0.28–56.19%. Biochar reduced the amount of Cd and Pb migration in the soil, and an increase in soil moisture content reduced the availability of Cd and Pb in the soil. Freezing and thawing damaged the soil structure, and biochar reduced the fractionation of small particle aggregates by enhancing the stability of soil aggregates, thereby reducing the soil's ability to adsorb Cd and Pb. In summary, for farmland soil remediation and pollution control, the application of biochar has a certain ability to optimize soil properties. Considering the distribution of PTEs in the soil and the physicochemical properties of the soil, the application of 1% biochar to soil with a 20% moisture content is optimal for regulating seasonally frozen soil remediation.