21. 题目: Restoration of afforested peatland: Immediate effects on aquatic carbon loss
22. 题目: Relative role of black carbon and sea-salt aerosols as cloud condensation nuclei over a high altitude urban atmosphere in eastern Himalaya
The present study is an attempt to investigate the relative role of black carbon (BC) and sea-salt aerosols on the CCN activation over a high altitude station, Darjeeling (27.1° N and 88.15° E, 2200 m asl) at eastern Himalaya. Aerosols (CN, CCN, BC and PM2.5) were measured during premonsoon and monsoon in 2017 and 2018. A unique sampling strategy and a novel methodology were adopted that enabled us to quantitatively and separately determine the contributions of local emissions (LE), valley wind transport (VWT) and long-range transport (LRT) to BC aerosols and their role in CCN activation. On the other hand, the contributions of transported sea-salt (NaCl) aerosols to CCN activation were also determined when they interact with the local anthropogenic soluble species and when they do not. CCN (0.5% super-saturation) concentrations were found to be increased when BC aerosols were more aged (~ 80 cm−3 and 218 cm−3 increase in CCN for 1 μg m−3 increase in BCLE and BCLRT with activation ratios of 0.17 and 0.55 respectively). Local anthropogenic acidic species (SO42−/H2SO4 (g) and NO3−/HNO3 (g)) interact with NaCl resulting to Cl− depletion. Cl− depletion was increased with the increase in NO3− + SO42−(45% for1 μg m−3increase in NO3− + SO42−) that in turn sharply decreased the AR of NaCl (0.04 for 1% increase in Cl- depletion). On the other hand, higher the NO3− + SO42−, higher were the CCN activation of transported BC which could be due to the soluble coating on BC. The important and interesting fact is that when transported and interacted with anthropogenic soluble species, BC aerosols (though hydrophobic) act as much better CCN than NaCl (though hydrophilic).
23. 题目: Abiotic and biotic controls of soil dissolved organic nitrogen along a precipitation gradient on the Tibetan plateau
24. 题目: High adsorption capacity of Mg–Al-modified biochar for phosphate and its potential for phosphate interception in soil
In this study, Mg and/or Al modified biochars (MABC1, MBC2, ABC3) prepared by co-precipitation were to explore their phosphate adsorption capacity from aqueous solution and the potential for soil phosphate interception. The results revealed that MABC composites contained more functional groups than MBC and showed a higher surface area than ABC. The surface of MABC contained dispersed MgAl2O4, Mg(OH)2, AlOOH and Al2O3 crystals that were associated with its enhanced maximum phosphate adsorption capacity (153.40 mg g−1). According to Langmuir model, the maximum adsorption capacity of MABC was 15.91, 1.85, and 93.54 times the capacity of MBC, ABC, and raw biochar (BC4), respectively. The addition of MABC in red soil could significantly slow down the release of soil phosphorus, and MABC also had a stronger phosphate interception capacity (59.89%) than other BCs. In summary, MABC exhibits superior phosphate adsorption and interception capacity, making it ideal for treatment and prevention of phosphorus-polluted water.
25. 题目: Caffeine removal by Gliricidia sepium biochar: Influence of pyrolysis temperature and physicochemical properties
The present study aimed to envisage the effect of physicochemical properties on the performance of Gliricidia sepium biochar (GBC) pyrolyzed at 300, 500, and 700 °C in the removal caffeine (CFN); a pharmaceutical and personal care product, from water. The physicochemical properties of GBC were characterized by proximate and ultimate analysis, BET, SEM, FTIR, and Raman spectroscopy. The adsorption batch experiment was carried out at various pH values (pH 3–10), mixing times (up to 24 h), and initial CFN concentration (10–500 mg/L). The FTIR analysis revealed the loss of polar functional groups on the surface of GBC derived at high temperatures. The red-shifted and blue-shifted Raman peaks indicate the condensation of small molecules on GBC. The GBC derived at 700 °C demonstrated high CFN adsorption capacity (16.26 mg/g) due to its high surface area and aromaticity. The highest adsorption of CFN was occurred at acidic pH range from 3.5 to 4.5 due to the existence of non-specific attraction between CFN and GBC. The kinetics and isotherm experimental data were fitted with Elovich and fractional power kinetic regression, Freundlich, and Temkin isotherm models, which suggested the adsorption of CFN on the GBC by mixed mechanisms; physisorption and chemisorption including π–π interactions, hydrogen bonding, n–π interactions, electrostatic attraction, and electron donor-acceptor attraction. Moreover, both surface area and aromaticity index have demonstrated a high positive correlation for CFN adsorption, signifying the importance of controlling physicochemical properties based on the end-user purpose of biochar.
26. 题目: Combination of energy limitation and sorption capacity explains 14C depth gradients
During the last decade, a paradigmatic shift regarding which processes determine the persistence of soil organic matter (SOM) took place. The interaction between microbial decomposition and association of organic matter with the soil mineral matrix has been identified as a focal point for understanding the formation of stable SOM. Using an improved version of the vertically resolved SOM model COMISSION (Ahrens et al., 2015), this paper investigates the effect of a maximum sorption capacity (Qmax) for mineral-associated organic matter (MAOM) formation and its interaction with microbial processes, such as microbial decomposition and microbial necromass production.
We define and estimate the maximum sorption capacity Qmax with quantile regressions between mineral-associated organic carbon (MAOC) and the clay plus silt (<20 μm) content. In the COMISSION v2.0 model, plant- and microbial-derived dissolved organic matter (DOM) and dead microbial cell walls can sorb to mineral surfaces up to Qmax. MAOC can only be decomposed by microorganisms after desorption.
We calibrated the COMISSION v2.0 model with data from ten different sites with widely varying textures and Qmax values. COMISSION v2.0 was able to fit the MAOC and SOC depth profiles, as well as the respective 14C gradients with soil depth across these sites. Using the generic set of parameters retrieved in the multi-site calibration, we conducted model experiments to isolate the effects of varying Qmax, point-of-entry of litter inputs, and soil temperature. Across the ten sites, the combination of depolymerization limitation of microorganisms due to substrate scarcity in the subsoil and the size of Qmax explain 14C depth gradients in OC.
27. 题目: Arsenic adsorption on layered double hydroxides biochars and their amended red and calcareous soils
Highly efficient amendments for controlling arsenic (As) pollution in soils are imperative to improve soil quality and enhance food production. In the present study, corn stalk biochar was functionalized with three kinds of layered double hydroxides (i.e., Mg–Al-LDH, Zn–Al-LDH, and Cu–Al-LDH) using a simple co-precipitation method. The synthesized LDH biochar composites () exhibited better adsorption capacity and affinity for As due to their enhanced anion exchange capacity and reactive surface hydroxyl groups identified by XRD, FTIR and XPS. Arsenic (As) bioavailability and leaching characteristics of spiked red and calcareous soils (150 mg As/kg) amended with or without were investigated using soil column. The Zn– decreased the As (V) migration and increased pak choi (Brassica chinensis L.) growth in both red and calcareous soil. These results indicated that LDH modified biochar is an effective way to overcome the shortfalls of unmodified biochar in mitigating the As contamination and provide a basis for further exploring the potential of biochar-based soil amendments for environmental remediation.
28. 题目: Degradation of sulfamethoxazole with persulfate using spent coffee grounds biochar as activator
In the present study, biochar from spent coffee grounds was synthesized via pyrolysis at 850 °C for 1 h, characterized and employed as catalyst for the degradation of sulfamethoxazole (SMX) by persulfate activation. A variety of techniques, such as physisorption of N2, scanning electron microscopy, Fourier transform infrared spectroscopy, X–ray diffraction, thermogravimetric analysis, and potentiometric mass titration, were employed for biochar characterization. The biochar has a surface area of 492 m2/g, its point of zero charge is 6.9, while mineral deposits are limited.
SMX degradation experiments were performed mainly in ultrapure water (UPW) at persulfate concentrations between 100 and 1000 mg/L, biochar concentrations between 50 and 200 mg/L, SMX concentrations between 500 and 2000 μg/L and initial solution pH between 3 and 10. Real matrices, besides UPW, were also tested, namely bottled water (BW) and treated wastewater (WW), while synthetic solutions were prepared spiking UPW with bicarbonate, chloride, humic acid or alcohols. Almost complete removal of SMX can be achieved using 200 mg/L biochar and 1000 mg/L sodium persulfate (SPS) within 75 min. The presence of biochar is important for the degradation process, while the activity of the biochar increases linearly with SPS concentration. Degradation follows a pseudo–order kinetic model and the rate increases with increasing biochar concentration and decreasing SMX concentration. Although SMX adsorption onto the biochar surface is favored at acidic conditions, degradation proceeds equally fast regardless of the initial solution pH. Reactions in either real matrix are slower, resulting in 55% SMX removal in 60 min for WW. Bicarbonate causes severe inhibition as only 45% of SMX can be removed within 75 min in UPW. The addition of alcohol slightly inhibits degradation suggesting that the reaction pathway is either under electron transfer control or due to the generation of surface oxygen radicals with higher oxidation potential than the homogeneously produced radicals.
29. 题目: Volatile organic compounds from leaf litter decomposition alter soil microbial communities and carbon dynamics.
Investigations into the transfer of carbon from plant litter to underlying soil horizons has primarily focused on the leaching of soluble carbon from litter belowground or the mixing of litter directly into soil. However, previous work has largely ignored the role of volatile organic compounds (VOCs) released during litter decomposition. Unlike most leaf carbon, these litter‐derived VOCs are able to diffuse directly into the soil matrix. Here, we used a 99‐day microcosm experiment to track VOCs produced during microbial decomposition of 13C‐labeled leaf litter into soil carbon fractions where the decomposing litters were only sharing headspace with the soil samples, thus preventing direct contact and aqueous movement of litter carbon. We also determined the effects of these litter‐derived VOCs on soil microbial community structure. We demonstrated that the litter VOCs contributed to all measured soil carbon pools. Specifically, VOC derived carbon accounted for 2.0, 0.61, 0.18, and 0.08% of carbon in the microbial biomass, dissolved organic matter, mineral associated organic matter, and particulate organic matter pools, respectively. We also show that litter‐derived VOCs can affect soil bacterial and fungal community diversity and composition. These findings highlight the importance of an underappreciated pathway where VOCs alter soil microbial communities and carbon dynamics.
30. 题目: Activated carbon and organic matter characteristics impact the adsorption of DBPs precursors when chlorine is added prior to GAC contactors
Pre-chlorination (i.e. dosing chlorine prior to granular activated carbon (GAC) contactors) was recently introduced as a promising method to reduce the formation of disinfection byproducts (DBPs). However, our understanding on the effect of natural organic matter (NOM) and GAC characteristics on pre-chlorination efficiency is still elusive. Thus, we have designed this systematic study to investigate the effects of GAC characteristics (i.e. surface area, pore size, and surface charge) on the subsequent reduction of DBP formation using five well-characterized adsorbents with three different NOM under three initial Br− concentrations. The results revealed that the adsorption of halogenated DBPs precursors mostly occurs in the mesoporous region (i.e. 2 nm < pore size <50 nm) of the adsorbents. Subsequently, pre-chlorination before treatment with HD3000 (i.e. GAC with the highest mesoporous surface area) decreased the formation of DBPs by 58%. Furthermore, oxidation of GAC increased the surface acidity and negatively impacted the adsorption of halogenated DBP precursors, which suggests basic GACs as promising adsorbents when applying pre-chlorination. In addition, experiments with different NOM showed that pre-chlorination was effective with higher aromatic NOM (i.e. high specific ultraviolet absorbance (SUVA254)). However, pre-chlorination of NOM with low SUVA254 has decreased the adsorption of some DBP precursors which resulted in increased formations of haloacetic acid (HAA) and total organic halide (TOX). Also, experiments with effluent organic matter (EfOM) showed that pre-chlorination did not increase the adsorption of DBP precursors in low SUVA254 wastewater effluents. Besides, increasing initial Br− concentration increased the formation of brominated DBPs (Br-DBPs) and the adsorbed Br-DBP precursors. This study gives in-depth understanding of the mechanisms, advantages, and limitations of pre-chlorination as a potential method to control DBPs formation.
31. 题目: Dynamics of active potential bacterial and fungal interactions in the assimilation of acidobacterial EPS in soil
Acidobacteria are one of the most abundant and ubiquitous bacterial phyla in soil, but the mechanisms underpinning their ecological success remain unknown. Acidobacteria produce copious amounts of extracellular polymeric substances (EPS) with unique sugar composition that can be used as a nutrient source for other microorganisms. Here, we investigated the assembly and potential interactions of the active bacterial and fungal communities in soil treated with the EPS of the Acidobacteria Granulicella sp. strain WH15 (WH15EPS) as a carbon source by the stable isotope probing (SIP) approach during a 35-day period. WH15EPS was mainly assimilated by Planctomycetes, Verrucomicrobia, Ascomycota and Basidiomycota and analysis suggested overall relationships between the kingdoms. Our study revealed active potential interactions between microorganisms in their natural habitat. In addition, the structure of the co-occurrence network of active microorganisms able to metabolize WH15EPS differed from those of the control treatments, demonstrating that hidden potential interactions can be unraveled by more specific and targeted metabolism studies.
32. 题目: Updated potential soil carbon sequestration rates on U.S. agricultural land based on the 2019 IPCC guidelines
The Intergovernmental Panel on Climate Change (IPCC) recently updated the 2006 IPCC Guidelines to reflect the most current research and information available for countries to accurately estimate their reporting data for greenhouse gas emissions. To report on changes in soil organic carbon (SOC), the IPCC method uses fixed factors to estimate how land-use and management changes affect default reference SOC stocks. The 2019 IPCC Guidelines incorporate additional studies and more recent research to modify the default reference SOC stocks and the factors used to estimate the effect of land use and management changes on SOC stocks. The research presented here applies the 2019 IPCC factors to agricultural land in the conterminous U.S. and compares the results to the same research conducted using the 1996 IPCC factors. Baseline SOC stocks were slightly higher estimated with 1996 IPCC factors compared to 2019 factors (17.1 vs 15.2 Tg C yr−1 (million metric tonnes of carbon per year)), but the source was quite different. Applying the 1996 factors resulted in about 52 percent of the SOC stock increase from land-use-change (LUC) and 42 percent from tillage effects while the 2019 factors indicate about two-thirds of the SOC stock increase was from LUC and one-third from tillage effects. Using the 1996 IPCC documentation provided estimates of annual SOC stock increases of 83.2 Tg C yr−1 for twenty years (66 Tg C yr−1 more than the baseline) from set-aside, including winter-cover crops, eliminating fallow, and no-till adoption. Smaller increases from these same activities are estimated when using the 2019 IPCC factors with a total potential increase of 47.3 Tg C yr−1. The SOC stock increases are predominantly in the wetter regions. The two activities that provide the greatest increase in estimated SOC stocks were from the addition of cover crops, which increased SOC by 17.7 Tg C yr−1 using 2019 IPCC factors compared to 22.8 Tg C yr−1 using the 1996 IPCC factors, and full adoption of no-till which increased SOC by 18.4 compared to 30.3 Tg C yr−1 for the same comparison.
33. 题目: Synthesis, characterization and application of novel MnO and CuO impregnated biochar composites to sequester arsenic (As) from water: Modeling, thermodynamics and reusability
The present study aimed at enhancing the adsorption potential of novel nanocomposites of Sesbania bispinosa biochar (SBC) with copper oxide (SBC/CuO) and manganese oxide nanoparticles (SBC/MnO) for the efficient and inexpensive removal of environmentally concerned contaminant arsenic (As) from contaminated water at batch scale. The scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX), X-ray diffraction (XRD) and point of zero charge (PZC) analyses proved successful impregnation of the metallic nanoparticles on SBC surface. The results revealed the maximum As removal (96 %) and adsorption (12.47 mg/g) by SBC/CuO composite at 10 mg As/L, optimum pH-4, dose 1.0 g/L and ambient temperature (25 ± 1.5 °C) as compared with SBC (7.33 mg/g) and SBC/MnO (7.34 mg/g). Among four types of adsorption isotherms, Freundlich isotherm demonstrated best fit with R2 > 0.997. While pseudo second-order kinetic model revealed better agreement with kinetic experimental data as matched with other kinetic models. The thermodynamic results depicted that As adsorption on the as-synthesized adsorbents was endothermic and spontaneous in nature with increased randomness. The SBC/CuO displayed excellent reusability and stability over four adsorption/desorption cycles and proved that the as-synthesized SBC/CuO composite may be the efficient adsorbent for practical removal of As from contaminated water.
34. 题目: Effect of biochar addition on CO2 exchange in paddy fields under water-saving irrigation in Southeast China
Biochar has been widely applied to paddy fields to improve soil fertility, crop productivity and carbon sequestration, thereby leading to variations in the CO2 exchange between the paddy fields under flooding irrigation and the atmosphere, as indicated by many previous reports. However, few relevant reports have focused on paddy fields under water-saving irrigation. This study conducted a field experiment to investigate the effects of three biochar addition rates (0, 20 and 40 t ha−1) on the CO2 exchange between paddy fields under controlled irrigation (CI, a water-saving irrigation technique) and the atmosphere in the Taihu Lake region of Southeast China. Our results showed that biochar addition increased the paddy field ecosystem respiration (Reco) and the soil respiration rate (Rs) in the CI paddy fields. And biochar application increased the total CO2 emissions and the total soil CO2 emissions, especially at a rate of 40 t ha−1. In contrast, gross primary productivity (GPP) was decreased and the net ecosystem exchange of CO2 (NEE) was increased with biochar addition. However, biochar addition at a rate of 20 t ha−1 significantly increased the total CO2 absorption and the net CO2 absorption of the CI paddy fields (p < 0.05), whereas biochar addition at a rate of 40 t ha−1 had no effect on the total CO2 absorption and decreased the total net CO2 absorption. At the same time, biochar addition significantly increased soil catalase, invertase and urease activities and contributed substantially to the increase in soil invertase activity. In addition, the soil bacterial, fungal and actinomycetal abundances were evidently increased with biochar addition, of which the soil fungal abundance showed the greatest increase. A high correlation was observed between soil catalase and invertase activities and soil microbial abundance. Reco was highly correlated with air and soil temperatures and soil enzyme activity. A significant quadratic polynomial correlation was observed between GPP and leaf area index (p < 0.01) The combination of biochar addition at a rate of 20 t ha−1 and water-saving irrigation has the potential to increase the size of the carbon sink and promote soil enzyme and microbial activities in paddy field ecosystems.
35. 题目: Molecular-level insights into the transformation mechanism for refractory organics in landfill leachate when using a combined semi-aerobic aged refuse biofilter and chemical oxidation process
Landfill leachate contains high concentrations of complex organic matter (OM) that can severely impact the ecological environment. If landfill leachate is to be treated using a combined biological + advanced treatment process, the molecular information of OM must be investigated to optimize the operation parameters of the combined process and maximize the removal of organic pollutants. This study applied ultra-high resolution mass spectroscopy to investigate the degradation and transformation characteristics of refractory OM in mature landfill leachate at the molecular level (m/z = 150–800) during biological treatment (i.e., semi-aerobic aged refuse biofilter, SAARB) and subsequent chemical oxidation (i.e., the Fenton process and ozonation). After SAARB treatment, the polycyclic aromatics (aromatic index, AI > 0.66) and polyphenol (0.66 ≥ AI > 0.50) contents increased, and the highly unsaturated phenolic compounds (AI ≤ 0.50 and H/C < 1.5), which have a high bioavailability, were mostly removed. Compared with raw leachate, SAARB effluent (i.e., SAARB leachate) contained fewer organics with short carbon chains, more organics with long carbon chains, an elevated condensation degree for organics and, thus, a considerably reduced biodegradability. Although both the Fenton and ozonation processes could remove many of the polycyclic aromatics and polyphenols, ozone produced considerable amounts of aliphatic compounds with high bioavailability. Compared to ozonation, the Fenton process utilized the hydroxyl radical to non-selectively react with OM and produced better mineralization results.
36. 题目: Ecological risks of heavy metals as influenced by water-level fluctuations in a polluted plateau wetland, southwest China
The Caohai wetland, one of karst plateau wetlands in southwest China, is given more attention due to the serious heavy metal (HM) pollution from artisanal zinc smelting activities. A natural hydrological change has caused this wetland to form a water-level fluctuating zone. This raises a question of whether such an area has elevated HM risks to the aquatic environment, and it was explored by a field investigation and biological exposure experiment. The results showed that Caohai sediment properties were significantly altered by water-level fluctuation, and the permanently inundated sediment had obviously higher organic matter (SOM) concentrations (32.62 ± 9.37%), humification levels (ratio of C to H, 6.81 ± 0.97), and Fe oxide fractions (12.29 ± 3.17%) than seasonally inundated sediment (4.94 ± 2.25%, 1.33 ± 0.75, and 8.72 ± 1.87%, respectively). These significantly enhanced the competition and retention, resulting in the increased accumulation, whereas reduced bioavailability of HMs. In comparison, the mean bioaccumulation capacity of Zn, Pb and Cd by wild benthos at the seasonally inundated area respectively increased by 2, 11 and 20 times higher than that at the permanently inundated area, which was further verified in the biological incubation experiment. Our results suggest that hydraulic fluctuation can greatly shape the sediment properties to increase the ecological risks of HMs to organisms.
37. 题目: Infrared spectroscopy approaches support soil organic carbon estimations to evaluate land degradation
38. 题目: Stabilization of soil aggregate and organic matter under the application of three organic resources and biochar-based compound fertilizer
39. 题目: Usage of biochar for mitigation of CO2 emission and enhancement of CH4 consumption in forest and orchard Haplic Luvisol (Siltic) soils
It has been reported that biochar changes the properties of soil and has beneficial environmental and agrotechnical consequences, especially in degraded lands, including those affected by climate change. We added wood biochar (produced from fir sawdust by pyrolysis at 650 °C) to soil collected from a forest and an adjacent long-term cultivated orchard to test the short-term response of soil respiration and methanotrophy under moisture levels of 100% and 55% water holding capacity (WHC).
In the controls of the respiration studies (without biochar), CO2 emission was generally higher under 55% than 100% WHC in both soils. Biochar application to the forest soil resulted in a significant reduction of the CO2 emission rate under both WHC levels. This is in contrast with the orchard soil, where the CO2 emission rate was not significantly changed (55% WHC) or even stimulated (100% WHC). Regardless of the moisture level, the CO2 emission and O2 consumption was higher in the forest soil than in orchard soil. In the controls of the methanotrophic study, only slight CH4 consumption was observed in both the tested water-content conditions. The biochar effect was dependent on the WHC level. Under 100% WHC, CH4 was completely consumed in both soils with different lag durations. However, under 55% WHC, methanotrophy was stimulated by biochar only in the orchard soil. We concluded that the short-term response of soil respiration and methanotrophy to biochar amendment is influenced by land use and strongly depends on soil moisture conditions. We showed the effectiveness of biochar addition as a method to limit CO2 emission in non-saturated forest soil, and to increase CH4 uptake in saturated soils, regardless of land use, which confirms its efficiency in reducing the greenhouse effect.
40. 题目: Strong linkages between dissolved organic matter and the aquatic bacterial community in an urban river
Aquatic bacterial communities play an important role in biogeochemical cycling in river ecosystems; however, knowledge of the linkages between bacterial communities and dissolved organic matter (DOM) in urban rivers is limited. Here, 16S rRNA amplicon sequencing and parallel factor (PARAFAC) modeling of excitation-emission fluorescence spectroscopy were used to analyze the compositions, co-occurrence patterns, and interactions with chromophoric DOM (CDOM) of bacterial communities in urban river water samples influenced by different human activities. The results revealed that two protein-like components accounted for 65.2 ± 9.56% of the total variability in all three fluorescence components, which suggests that CDOM in urban rivers is mainly a microbial source. In addition to pH and DO, CDOM is also an important factor affecting bacterial community structure, and the main classes (Gammaproteobacteria and Clostridia) and genera (Limnohabitans and Alpinimonas) showed strong positive correlations with terrestrial humic-like C1 and tryptophan-like C2, respectively. When autotrophic and heterotrophic bacteria coexist in urban rivers, the production and degradation of CDOM will occur simultaneously. Furthermore, the riverine bacterial co-occurrence network had a nonrandom modular structure, which was mainly driven by classification correlation and bacterial function. The high abundance of genes related to xenobiotic metabolism, carbon metabolism and nitrogen metabolism in the urban river indicated that anthropogenic activity may be the dominant selective force altering the bacterial communities. Overall, our results provide a novel view for the assembly of bacterial communities in urban river ecosystems under the influence of different human activities.