12721. 题目: Influence of dissolved organic matter components on arsenate adsorption/desorption by TiO2
期刊: Journal of Hazardous Materials
作者: Meijie Ren, Guangfei Qu, Heng Li, Ping Ning
摘要: The influences of different dissolved organic matter (DOM) components and ionic matters on As(V) adsorption/desorption behavior on the TiO2 surface were investigated. The results demonstrated that the characteristics and involving order of DOM significantly affected the As(V) adsorption/desorption behavior. The presence of DOM decreased the As(V) adsorption quantity. Fulvic acid (FA) exhibited the most negative effect, and followed by the order of alginate ≈ BSA > SDBS. The precomplexation DOM prevented more As(V) adsorption. While, the presence of DOM caused more As(V) release when the surrounding changed and FA exhibited the strongest effect. The results indicated that the site competition and electrostatic repulsion were the major mechanisms to resist As(V) adsorption. The presence of Fe3+ and Ca2+ increased As(V) adsorption by bridge effect, while PO43- and CO32- decreased As(V) adsorption owing to the competition.
12722. 题目: Use of microdialysis to assess short-term soil soluble N dynamics with biochar additions
期刊: Soil Biology and Biochemistry
作者: Si Gao, Thomas H. DeLuca
摘要: To date there has been little effort to assess fine-scale soil solution nitrogen (N) dynamics over time and space in response to biochar application within days. Herein we applied microdialysis to investigate the spatial and temporal dynamics of free amino acids (AA), ammonium (NH4+), and nitrate (NO3−) following biochar application to a column containing sandy loam forest soil. Wood biochar (diameter ≤ 5 mm) was applied either at surface or mixed through the entire soil column. Biochar stimulated localized soluble N diffusive fluxes, and the vertical distribution of AA and NH4+ hotspots gradually matched the distribution of biochar particles in the soil matrix over time. Increases in soil AA and NH4+ concentrations were more homogeneous along soil profile when biochar was mixed through the soil core and were more concentrated at the surface when biochar was surface applied. Increases in NO3− concentrations were only observed at surface soil layers following biochar addition regardless of the application strategy and generally exhibited a high degree of variation over the course of the experiment. Microdialysis sampling allowed for quantification of ‘hotspots’ of soil soluble N in association with the “charosphere” across time and space.
12723. 题目: Changes in surface soil organic/inorganic carbon concentrations and their driving forces in reclaimed coastal tidal flats
作者: Huan Zhang, Aijing Yin, Xiaohui Yang, Pengbao Wu, Manman Fan, Jingtao Wu, Ming Zhang, Chao Gao
摘要: Intensive coastal wetland reclamation in China followed by agricultural use had significant impacts on soil carbon (C) dynamics due to the alterations in soil hydrology and physicochemical properties. The changes in C and its driving factors in reclaimed soils generally concentrated on soil organic C (SOC) and soil inorganic C (SIC) as major subpools of soil C, but this topic has received little attention. In this study, we have assessed the changes in SOC and SIC concentrations (0–20 cm) with reclamation duration and land use change based on 746 surface soil samples collected from three typical reclamation areas (with differences in sediment sources) in eastern China. Key factors driving SOC and SIC dynamics were identified using a random forest model (RF). The results revealed similar SOC concentration (7.24–7.69 g kg−1) and different SIC concentration (7.25–10.9 g kg−1) for the three study areas. Overall, SOC increased with reclamation duration, suggesting a positive impact of tidal flat reclamation on SOC accumulation. For SIC, slight increases in the younger land and dramatic decreases in the older land were observed, indicating a fast IC turnover time. The land impacted strongly by human activities had higher SOC than natural tidal flats. Compared with upland soil, paddy soil resulted in greater OC (except for 10 years reclaimed land in Cixi) and comparable levels of IC. Soil nutrient levels (the concentrations of nitrogen and phosphorus) were determined to be important factors for SOC in reclaimed lands. Soil CaO was determined to be the factor with the highest importance in controlling SIC dynamics in reclaimed lands. More attention should be given to the quality of the OC sequestrated by reclaimed soils.
12724. 题目: Effect of temperature on the characterization of soluble microbial products in activated sludge system with special emphasis on dissolved organic nitrogen
期刊: Water Research
作者: Haidong Hu, Yuanji Shi, Kewei Liao, Haijun Ma, Ke Xu, Hongqiang Ren
摘要: Previous research has focused on dissolved organic carbon (DOC) as a surrogate for soluble microbial products (SMPs) and found that temperature has a significant influence on the production of SMP-based DOC (SDOC) during biological processes. Little is known about the SMP-based dissolved organic nitrogen (SDON), although some nitrogenous organic matter has been identified as an important part of SMPs. This study investigated the effect of temperature (8 °C, 15 °C and 25 °C) on the characterization of SMPs in an activated sludge system with special emphasis on SDON. Results showed the positive effect of reduced temperature on SDON production. Fluorescence spectroscopy and ultrahigh-resolution mass spectrometry showed the produced SDON at 8 °C and 15 °C exhibits more lability than at 25 °C. This was also supported by the algal bioassay, indicating the SDON produced at low temperature is highly bioavailable and prone to stimulate algae and microorganisms. In addition, principal component analysis demonstrated that the effect of temperature on the chemical characterization of SDON is different from that of SDOC. Overall, this study highlights the importance of SDON control during biological processes at a low temperature to reduce the potential impact of effluent SMPs on receiving waters or wastewater reuse.
12725. 题目: Clay content and mineralogy, organic carbon and cation exchange capacity affect water vapour sorption hysteresis of soil
期刊: European Journal of Soil Science
作者: E. Arthur, M. Tuller, P. Moldrup, L.W. de Jonge
摘要: The hysteretic behaviour of the dry region (< −1.5 MPa) of the soil water characteristic, which is of the essence for accurate characterization and modelling of bio‐physicochemical soil processes under dry conditions, is well documented. However, knowledge about how to best quantify water vapour sorption hysteresis and about the effects of soil properties on dry‐region hysteretic behaviour is limited. To overcome this knowledge gap, we proposed a new method for quantifying sorption hysteresis and evaluated its applicability based on measured sorption isotherms of four source clay minerals and 147 soil samples. Furthermore, the effects of clay mineralogy, clay content, soil organic carbon (SOC), and cation exchange capacity (CEC) on the magnitude of sorption hysteresis were investigated. For the clay minerals, kaolinite did not exhibit hysteretic behaviour, illite showed some hysteresis, while Na‐ and Ca‐smectite exhibited strong hysteretic behaviour. The average hysteresis, corrected for clay and SOC contents, was strongly reflective of the dominant clay mineralogy of the soil samples. For the soil samples with low SOC content, the average hysteresis significantly increased with increasing clay content (R2 = 0.92), except for the kaolinite‐rich samples (R2 = 0.35). The SOC‐rich samples that exhibited illitic clay mineralogy and similar soil texture showed a significant increase in average hysteresis with increasing organic carbon content (R2 = 0.93). For all soil samples combined, the CEC was the strongest indicator for the magnitude of water vapour sorption hysteresis.
12726. 题目: Bio-organic stabilizing agent shows promising prospect for the stabilization of cadmium in contaminated farmland soil
期刊: Environmental Science and Pollution Research
作者: Zhenqian Xiong, Junqing Zhang, Peng Cai, Wenli Chen, Qiaoyun Huang
摘要: In situ immobilization of cadmium (Cd) has been considered as a cost-effective and non-disruptive remediation technique for Cd-contaminated soils. In this study, several immobilization approaches were compared in a Cd-contaminated agricultural farmland. The soil was treated with different combinations of the immobilizing agents such as biochar (C), rice straw (RS), lime (L), and engineered bacteria P. putida X4/pIME (B). The plant yield and Cd uptake of lettuce as well as soil Cd fractionations were measured. The Cd content in lettuce leaves and roots decreased by 46.8~67.2% and 36.8~60.2%, respectively. Among the five treatments, combined rice straw, lime, and engineered bacteria treatment showed the lowest Cd concentration in lettuce leaves (0.14 mg/kg) and the highest plant yield (21.5 t/ha). The alleviating effects are assigned to the significant transformation of water soluble and exchangeable Cd to humic substance bound, strong organic bound and residual Cd in the soils. This study suggests that this bio-organic stabilizing agent is more cost-effective than some other immobilization agents reported previously, and shows a great application prospect in improving agriculture production of heavy metal-polluted agricultural soils.
12727. 题目: Adsorption and sequestration of cadmium ions by polyptychial mesoporous biochar derived from Bacillus sp. biomass
期刊: Environmental Science and Pollution Research
作者: Feng Li, Yixin Tang, Chengcheng Li, Yang Zheng, Xingwang Liu, Chuang Feng, Wan Zhao, Fang Wang
摘要: Bacteria-derived biochars from Bucillus sp. biomass under different pyrolysis temperature (250 °C, 350 °C, 450 °C, and 550 °C, respectively) were prepared, forming polyptychial, mesoporous graphite-like structure. The adsorption and sequestration efficiencies of Cd2+ by these biochars were evaluated, and the underlying mechanisms were then discussed. Cd2+ sorption data could be well described by Langmuir mode while the pseudo-second-order kinetic model and Elovich model best fitted the kinetic data. The functional groups complexation, cation-π interactions, and interaction with minerals (including surface precipitation with phosphorus and ion exchange) jointly contributed to Cd2+ sorption and sequestration on biochar, but the interaction with minerals played a dominant role by forming insoluble cadmium salt composed by polycrystalline and/or amorphous phosphate-bridged ternary complex. The maximum sorption capacity of BBC350 in simulated water phase of soil for Cd2+ was 34.6 mg/g. Furthermore, the addition of bacteria-derived biochars (1%, w/w) decreased the fractions easily absorbed by plants for Cd in the test paddy soils by 1.9–26% in a 10-day time. Results of this study suggest that bacteria-derived biochar would be a promising functional material in environmental and agricultural application.
12728. 题目: How close is artificial biochar aging to natural biochar aging in fields? A meta-analysis
作者: Haixiao Li, Xueqiang Lu, Yan Xu, Haitao Liu
摘要: Biochar is used as a soil amendment to improve soil quality and fertility. The performance of biochar changes as it ages in fields. Artificial biochar aging methods (i.e. chemical oxidation) are considered proxies for natural biochar aging and help to evaluate the long-term effects of biochar amendment in soil. However, few studies have focused on how close artificial biochar aging methods are to biochar aging in fields. A meta-analysis of 42-studies was conducted to quantitatively compare the effects of soil incubation (natural field biochar aging), chemical oxidation (chemical biochar aging) and freeze-thaw cycling (freeze-thaw biochar aging) on biochar properties, including surface and bulk element compositions (C, H, O, N), specific surface area, cation exchange capacity and pH. The results showed that the artificial biochar aging methods cannot yet simulate biochar aging in the soil. In comparison with natural field aging, chemical aging tended to have a higher degree of oxidation at the surface of the aged biochar and posed the problems of oxidation inside the biochar and the import of exogenous elements from oxidants to the biochar. Freeze-thaw aging changed only the porous structure of the biochar with no significant alterations to element compositions, in contrast with natural aging.
12729. 题目: The Cenomanian/Turonian boundary deep-sea deposits in the Zagros Basin (SW Iran): Bioevents, carbon isotope record and palaeoceanographic model
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Behnaz Kalanat, Hossein Vaziri-Moghaddam
摘要: The Cenomanian/Turonian (C/T) boundary interval, spanning the upper part of the Sarvak Formation in the Zagros Basin (Izeh Zone), has been studied to determine the timing and the possible cause of biotic turnovers, coinciding with the intense environmental perturbations during the Oceanic Anoxic Event 2 (OAE2). The upper Cenomanian strata in the study section, composed of light-colour marlstone/organic-rich marlstone and shale bedding couplets, record fluctuations in microfossil assemblages and organic carbon contents. We suggest that the organic-poor layers, characterized by high abundance of radiolarians, were deposited during cold periods under surface water eutrophication (upwelling) and ventilated seafloor. In contrast, water column stratification during warm periods enhanced organic matter preservation and allowed deposition of organic-rich strata. Continued stratification and also increased runoff and primary productivity during warm intervals of OAE2 led to expansion of oxygen minimum zone (OMZ), which may have caused extinctions of deep followed by intermediate water planktic foraminifera. Such conditions may have led to significant decreases in the abundance and diversity of planktic foraminifera and dominance of the biserial genus Planoheterohelix (“Heterohelix” shift event). The δ13C curve in the study interval reveals the diagnostic features of global C/T boundary carbon isotope record, including three positive peaks (A, B and C) within the Whiteinella archaeocretacea Biozone. These carbon isotope features and the most important bioevents in the study section are stratigraphically listed below: 1- Highest occurrences (HOs) of Th. greenhornensis and Th. deeckei, 2- HO of R. cushmani and δ13C peak A, 3- HO of “G”. bentonensis, 4- Onset of “Heterohelix” shift event, 5- δ13C peak B, 6- δ13C peak C, 7- Filament event, 8- Lowest occurrence (LO) of H. helvetica, and 9- Holywell event.
12730. 题目: Isotope heterogeneity in ethyltoluenes from Australian condensates, and their stable carbon site-specific isotope analysis
期刊: Organic Geochemistry
作者: Jaime Cesar, John Eiler, Brooke Dallas, Laura Chimiak, Kliti Grice
摘要: Low-molecular-weight (LMW) aromatic compounds from petroleum fluids have not been widely studied for fluid-source correlations due to their volatility and their relatively low abundances in source rocks. However, LMW aromatics are important components in fluids, including condensates which lack biomarkers (molecular fossils typically used for correlation studies). Here, we have investigated the distribution of ethyltoluenes (o-ET, m-ET and p-ET; ortho, meta and para, respectively) in fluvial-deltaic condensates which contain relatively high abundances of the meta- isomer. The meta-selectivity found in these petroleum fluids is consistent with a mineral catalytic effect on the molecular distribution of these compounds, as it occurs during the clay-catalyzed synthesis of ethyltoluenes. Isomers differ up to 6‰ in δ13C values. Condensates from the Northern Carnarvon Basin, North West Shelf of Australia (NWS), have been analyzed by compound specific isotope analysis (CSIA) by GC-ir-MS, and site-specific isotope analysis (SSIA) using a Q-Exactive-GC OrbitrapTM-based mass spectrometer. The SSIA revealed a 13C enrichment at the methyl end of the ethyl branch of m-ET, following a normal kinetic isotope effect during thermal maturation (cleavage). Continuous development of this first SSIA application will make possible high resolution analysis of light aromatics to outline the evolution of the organic matter to hydrocarbons in petroleum systems.
12731. 题目: Formation of Water-Soluble Organic Matter Through Fungal Degradation of Lignin
期刊: Organic Geochemistry
作者: Seyyedhadi Khatami, Ying Deng, Ming Tien, Patrick G. Hatcher
摘要: Lignin is a major component of decaying terrestrial vegetation in soils and has been reported to contribute substantially to the formation of soil carbon humus and associated water extracts of soil. To better understand this process of humification, lignin from brown-rot degraded wood is subjected to a white-rot fungus (Phanerochaete chrysosporium) whose enzymes are particularly effective in lignin degradation. This enzymatic attack was monitored by ultrahigh resolution mass spectrometry of water soluble extracts of the fungal cultures. The ensuing molecular level characterizations showed that the P. chrysosporium fungi induced aromatic ring oxidations followed by ring opening as expected. However, we also observed the production of new molecules, some of which are aliphatic. These results are consistent with recent findings that hydroxyl radical attack of lignin involves ring opening reactions followed by electrocyclic condensations combined with radical scavenging/disproportionation reactions.
12732. 题目: Factor contribution to soil organic and inorganic carbon accumulation in the Loess Plateau: Structural equation modeling
作者: Wei Zhao, Rui Zhang, Hua Cao, Wenfeng Tan
摘要: The effects of climate, soil characteristics and management on soil carbon accumulation have been extensively investigated. However, the relative importance of these factors remains unclear, especially in arid and semiarid regions. Here we evaluated the contribution of the environmental variables (geographical location, climate, soil type, and land use type) to soil organic and inorganic carbon accumulation in the 0–100 cm soil layers across the Loess Plateau in China. A structural equation modeling (SEM) was used to distinguish direct from indirect effects of factors on soil carbon accumulation based on covariance structures. The results showed that environmental temperature and moisture were the primary controls of soil organic carbon density (SOCD) variation. The total effects (the sum of direct and indirect effect) of soil type and land use on SOCD were less than half of those of environmental temperature and moisture. In addition, the direct and negative effect of environmental temperature on SOCD increased, and the direct and positive effect of environmental moisture on SOCD decreased with soil depth. For the soil inorganic carbon densities in the 0–100 cm soil layers, soil organic carbon (SOC) content acted as the most important factor controlling the variations in soil inorganic carbon density (SICD). Environmental temperature and moisture mainly affected indirectly SICD by mediating through its impacts on soil type, SOC content, or soil pH. Less than 40% of variation in soil carbon accumulation for 0–100 cm soil depth is explained in the model. The unexplained variance highlights the need for the data on soil physicochemical properties, quality of organic carbon inputs, and soil microorganisms.
12733. 题目: Mineral protection regulates long-term global preservation of natural organic carbon
作者: Jordon D. Hemingway, Daniel H. Rothman, Katherine E. Grant, Sarah Z. Rosengard, Timothy I. Eglinton, Louis A. Derry, Valier V. Galy
摘要: The balance between photosynthetic organic carbon production and respiration controls atmospheric composition and climate1,2. The majority of organic carbon is respired back to carbon dioxide in the biosphere, but a small fraction escapes remineralization and is preserved over geological timescales3. By removing reduced carbon from Earth’s surface, this sequestration process promotes atmospheric oxygen accumulation2 and carbon dioxide removal1. Two major mechanisms have been proposed to explain organic carbon preservation: selective preservation of biochemically unreactive compounds4,5 and protection resulting from interactions with a mineral matrix6,7. Although both mechanisms can operate across a range of environments and timescales, their global relative importance on 1,000-year to 100,000-year timescales remains uncertain4. Here we present a global dataset of the distributions of organic carbon activation energy and corresponding radiocarbon ages in soils, sediments and dissolved organic carbon. We find that activation energy distributions broaden over time in all mineral-containing samples. This result requires increasing bond-strength diversity, consistent with the formation of organo-mineral bonds8 but inconsistent with selective preservation. Radiocarbon ages further reveal that high-energy, mineral-bound organic carbon persists for millennia relative to low-energy, unbound organic carbon. Our results provide globally coherent evidence for the proposed7 importance of mineral protection in promoting organic carbon preservation. We suggest that similar studies of bond-strength diversity in ancient sediments may reveal how and why organic carbon preservation—and thus atmospheric composition and climate—has varied over geological time.
12734. 题目: Impacts of an invasive grass on soil organic matter pools vary across a tree-mycorrhizal gradient
作者: Matthew E. Craig, Nadia Lovko, S. Luke Flory, Justin P. Wright, Richard P. Phillips
摘要: Increases in carbon (C) inputs can augment soil organic matter (SOM), or reduce SOM by accelerating decomposition. Thus, there is a need to understand how and why ecosystems differ in their sensitivity to C inputs. Invasive plants that invade wide-ranging habitats, accumulate biomass rapidly, and contribute copious amounts of C to soil can be ideal for addressing this gap. We quantified the effects of the invasive C4 grass, Microstegium vimineum, on SOM in three temperate forests across plots varying in their relative abundance of arbuscular mycorrhizal (AM) versus ectomycorrhizal (ECM) trees. We hypothesized that invasion would differentially affect SOM along the mycorrhizal gradient owing to recognized patterns in nitrogen availability (AM > ECM) and the proportion of unprotected SOM (ECM > AM). Across all sites, M. vimineum was associated with lower particulate organic matter (POM) in ECM-dominated plots, consistent with our hypothesis that invader-derived C inputs should stimulate decomposers to acquire nitrogen from unprotected SOM in soils with low nitrogen availability. However, the pattern of lower POM in the ECM-dominated soils was offset by greater mineral-associated organic matter (MAOM)—and isotopic data suggest this was largely driven by native- rather than invader-derived SOM—implying an invasion-associated transfer of native-derived POM into MAOM. Our results demonstrate a context-dependent shift in the form of SOM in a system with presumably enhanced C inputs. This finding suggests a need to look beyond changes in total SOM stocks, as intrinsic SOM changes could lead to important long-term feedbacks on invasion or priming effects.
12735. 题目: Enhanced short-chain fatty acids production from waste activated sludge with alkaline followed by potassium ferrate treatment
期刊: Bioresource Technology
作者: Zhang-Wei He, Cong-Cong Tang, Wen-Zong Liu, Yong-Xiang Ren, Ze-Chong Guo, Ai-Juan Zhou, Ling Wang, Chun-Xue Yang, Ai-Jie Wang
摘要: This study reported an efficient approach, i.e., alkaline followed by potassium ferrate (PF) pretreatment, to enhance short chain fatty acids (SCFAs) production from waste activated sludge anaerobic fermentation process. The optimum condition was initial pH of 10.0 and PF dosage of 28 mg Fe(VI)/g total suspended solid, with the highest SCFAs production of 382 mg chemical oxygen demand/g volatile suspended solid, which was 2.03 and 2.06 times higher than that of corresponding sole treatments. It was found that the alkaline + PF treatment could provide more soluble substrates for subsequent acidification process by accelerating disruption of both microbial cells and extracellular polymeric substances. And the alkaline + PF treatment also benefited to the activity promotion of specific hydrolases and inhibition of methanogens. Besides, the abundances of microorganisms related to SCFAs production, such as Proteiniclasticum and Macellibacteroides, were increased greatly, whereas the main SCFAs consumer, Proteobacteria, was decreased from 29.1% to 14.4%.
12736. 题目: Soil aggregate and intra-aggregate carbon fractions associated with vegetation succession in an alpine wetland of Northwest China
作者: Yunhao LiuSui, Xinping Zhu, Dianpeng Li, Cuixia Yan, Tao Sun, Hongtao Jia, Xiaoning Zhao
摘要: Alpine wetlands can function as carbon sinks because of their high soil organic content and low decomposition rates. However, the effects of alpine wetland succession on soil structure and soil organic carbon (SOC) stability have rarely been reported. The objective of this study was to investigate the effects of vegetation succession on soil aggregate distribution, bulk soil carbon, aggregate-associated C, and intra-aggregate C fraction in the Bayinbuluk alpine wetland. Research sites were selected in adjacent swamp (S), swampy meadow (SM), and meadow (M) locations. Five soil aggregate fractions (>5000, 2000–5000, 250–2000, 53–250 and <53 μm) were separated using a modified Yoder method. The light fraction organic carbon (LFOC), coarse/fine intra-aggregate particulate organic matter carbon (iPOM-C), and mineral-associated organic matter carbon (mSOM-C) were isolated from soil aggregates. In the wetland succession sequence, the mean weight diameter of soil aggregates increased (from 4.16 to 4.63 mm) from S to SM, and then decreased (from 4.63 to 3.23 mm) from SM to M. The bulk soil carbon content initially increased (from 93 to 129 mg kg−1) from S to SM, and then decreased (from 129 to 54 mg kg−1) from SM to M. The same trends were found for the aggregate-associated C in different size aggregates. The coarse iPOM-C content (88–133 mg kg−1) was higher than the fine iPOM-C content (77–118 mg kg−1) in different size aggregates in S samples. In SM and M samples, however, the coarse iPOM-C contents (98–124 mg kg−1 (SM); 60–82 mg kg−1 (M)) were lower than the fine iPOM-C contents (129–151 mg kg−1 (SM); 71–103 mg kg−1 (M)). The ratio of coarse iPOM-C to fine iPOM-C content (ROC/F) exceeded 1 in S but was lower than 1 in SM and M. These results indicate that soil aggregation stability and SOC content increased and then decreased across the wetland succession sequence, and that ROC/F can be used as an indicator of changes in SOC content caused by wetland succession.
12737. 题目: Beneficial dual role of biochars in inhibiting soil acidification resulting from nitrification
作者: Ren-yong Shi, Ni Ni, Jackson Nkoh Nkoh, Jiu-yu Li, Ren-kou Xu, Wei Qian
摘要: The dual role of biochar for inhibiting soil acidification induced by nitrification was determined through two-step incubation experiments in this study. Ca(OH)2 or biochar was added respectively to adjust soil pH to the same values (pH 5.15 and 5.85), and then the amended soils were incubated in the presence of urea for 70 days. The results showed that compared with Ca(OH)2 treatment, both rice straw biochar and peanut straw biochar inhibited the decrease in soil pH and the increase in exchangeable acidity during the incubation. The application of biochars suppressed soil nitrification during the incubation, and thus reduced 7.5 mmol kg−1 and 1.4 mmol kg−1 protons released from nitrification compared to Ca(OH)2 treatments. Compared with Ca(OH)2 treatment, the ammonia-oxidizing bacteria population size was decreased by 8% and 12% in rice straw biochar and peanut straw biochar treatments respectively, which was the main responsibility for the inhibited nitrification after biochar application. In addition, the application of rice straw biochar and peanut straw biochar increased soil pH buffering capacity (pHBC) respectively by 22% and 32%. The increased pHBC played the main role (75%) in inhibiting the acidification of the soil amended with peanut straw biochar, while the rice straw biochar inhibited soil acidification mainly through suppressing nitrification during the incubation. Overall, compared with lime application, biochars can inhibit soil acidification caused by urea application through suppressing the nitrification process and improving the resistance of soils to acidification. The crop residue biochars presented a longer-lasting effect on ameliorating acidic soils than mineral lime.
12738. 题目: Effects of bok choy on the dissipation of dibutyl phthalate (DBP) in mollisol and its possible mechanisms of biochemistry and microorganisms
期刊: Ecotoxicology and Environmental Safety
作者: Yulong Lin, Ying Zhang, Fuqing Zhang, Rui Li, Yang Hu, Hui Yu, Diogene Tuyiringire, Lei Wang
摘要: Phytoremediation is an ecologically sustainable method for remediating contaminated soils, however, research on phytoremediation and its mechanisms are still rarely reported. The highest dibutyl phthalate (DBP) dissipation rate was 91% in 0–3mm bok choy rhizosphere via a 45-day rhizo-box experiment, and bok choy could regulate soil nutrients by increasing soil ammonia nitrogen (AN) and available phosphorus (AP). The biochemistry mechanism of interaction between dissolved organic matter (DOM) and DBP was also elucidated by various spectroscopy techniques. It was found that the alkyl ester in DBP produced the fastest response during the binding process, and the aromatic, hydroxyl and phenolic groups of the DOM humic-like substances preceded amide in DOM protein-like substance. It was found that DBP pollution reduced the Chao1 richness and Shannon index of bacteria in black soil via a pot experiment and high-throughput sequencing, which disturbed the metabolic activities and functional diversity of microorganisms in Mollisol. The microbial abundance increased in bok choy amendments, which has a specific microbial community structure and a high abundance of Actinobacteria and Acidobacteria. We concluded that some enriched genera were responsible for DBP dissipation, Alsobacter, Lacibacter, Myceligenerans, Schrenkiella parvula and Undibacterium. The findings of this study revealed that the possible biochemistry and microbial mechanisms of phytoremediation promoting the DBP dissipation in rhizosphere Mollisol and provided more useful information for phytoremediation of organic pollutants.
12739. 题目: Polyaromatic hydrocarbons in biochars and human health risks of food crops grown in biochar-amended soils: A synthesis study
期刊: Environment International
作者: Jian Wang, Emmanuel Stephen Odinga, Wei Zhang, Xian Zhou, Bing Yang, Michael Gatheru Waigi, Yanzheng Gao
摘要: Soil amendment with biochars is currently being studied worldwide as a sustainable agricultural practice to improve soil and water quality, increase crop productivity, and augment soil carbon storage. However, the formation of polyaromatic hydrocarbons (PAHs) during biochar production is inevitable. Therefore, it is crucial to assess the risks in food safety and human health of crops grown in biochar-amended soils. This paper performed a synthesis study of PAH concentrations in biochars and estimated the risks of soils amended with biochars, based on refereed articles published between 2012 and 2018. The PAH concentrations in biochars ranged greatly, with the dominant proportion being 2–3 ringed PAHs (40%–71%). Biochar application increased the PAH levels in soils at drastically varying extents (0.02–3574 μg/kg), which led to a broad range of PAH concentrations in food crops grown in biochar-amended soils. A five-step method was then introduced to assess the toxicity of biochar-borne PAHs to human health. The total mean incremental lifetime cancer risk for adults was estimated to range between 2.0 × 10−6–1.9 × 10−5 via direct contact with and ingestion (inhalation) of contaminated soils or consumption of tainted crops. These results indicated that biochar amendment in soils might pose potential risks to food safety and human health, but the overall cancer risks through exposure to biochar-borne PAHs in soils and food crops were low. Higher application rates (e.g. ≥20 t/ha) of biochars with high PAH contents can be avoided to minimize human cancer risks. Although biochar application in arable farmlands has many environmental and agronomic benefits, holistic and systematic approaches are required to fully assess the benefits and risks before their large-scale adoption. PAHs in biochar may be reduced by improving the biochar production process and developing a cost-effective post-manufacturing treatment.
12740. 题目: Remediation of heavy metal contaminated soils by biochar: Mechanisms, potential risks and applications in China
期刊: Environmental Pollution
作者: Lizhi He, Huan Zhong, Guangxia Liu, Zhongmin Dai, Philip C. Brookes, Jianming Xu
摘要: There are global concerns about heavy metal (HM) contamination in soils, which in turn has produced an increased demand for soil remediation. Biochar has been widely documented to effectively immobilize metals in contaminated soils and has received increasing attention for use in soil remediation. Here, we review recent progresses in understanding metal-biochar interactions in soils, potential risks associated with biochar amendment, and application of biochar in soil remediation in China. These recent studies indicate that: (1) the remediation effect depends on the characteristics of both biochar and soil and their interactions; (2) biochar applications could decrease the mobility/bioavailability of HMs in soils and HM accumulation in plants; and (3) despite its advantages, biochar applications could pose ecological and health risks, e.g., by releasing toxic substances into soils or by inhalation of biochar dust. Research gaps still exist in the development of practical methods for preparing and applying different biochars that target specific HMs. In the future, the long term effects and security of biochar applications on soil remediation, soil organisms and plant growth need to be considered.