121. 题目: Sources and composition of natural and anthropogenic hydrocarbons in sediments from an impacted estuary
期刊: Science of The Total Environment
作者: Man Lu, Stephen Jones, Mac McKinney, Rick Wagner, Sakinat Mojisola Ahmad, Alyssa Kandow, Rona Donahoe, YueHan Lu
摘要: Hydrocarbons in estuarine sediments provide information on sources of sedimentary organic matter (OM), and they are thus useful for tracing natural and anthropogenic OM inputs to the estuary. Here, we assessed the amounts, compositions and sources of natural and anthropogenic hydrocarbons from the sediments of a large, ecologically important estuary, Mobile Bay in Southeast USA. TOC/TN ratios and δ13C of organic carbon suggest that the bulk natural OM was sourced from marine phytoplankton and bacteria mixed with marsh and terrigenous C3 plants. Normal alkanes show high proportions of long-chain compounds with a high Carbon Preference Index, indicating the importance of C3 plants-derived OM in Mobile Bay. High concentrations of biogenic hopanes and perylene indicate microbial sources and degradation played an important role in shaping OM compositions. Anthropogenic hydrocarbons, αβ-hopanes and Polycyclic aromatic hydrocarbons (PAHs), were widely detected in Mobile Bay sediments. The source diagnostic ratios of hopanes and steranes suggest they were sourced from coal and diesel combustions. The source diagnostic ratios of PAHs, together with a positive correlation between PAHs and total Hg, suggests that PAHs originated primarily from coal combustion. We proposed two ratios, αβ/(ββ + hopenes) and 16 PAHs/perylene, to evaluate anthropogenic versus natural contributions of hydrocarbons. These ratios were higher in the western estuary than in the eastern estuary, suggesting elevated anthropogenic hydrocarbon inputs to the western estuary. Correspondingly, the toxic equivalent quantity (TEQBaQ) of PAHs showed a higher ecological risk for the western estuary. This spatially uneven distribution of hydrocarbon pollutants can be attributed to more concentrated urban and industrial areas on the western shore, suggesting the importance of adjacent pollution sources. Collectively, our results provide new insights into the origins and dynamics of natural and anthropogenic OM and highlight the significance of coal combustion in contributing hydrocarbon pollutants in Mobile Bay sediments.
122. 题目: Magnesium-modified biochar was used to adsorb phosphorus from wastewater and used as a phosphorus source to be recycled to reduce the ammonia nitrogen of piggery digestive wastewater
期刊: Journal of Cleaner Production
作者: Lintong He, Dehan Wang, Zhaoyun Wu, Yongzhen Lv, Sicheng Li
摘要: High concentrations of ammonia nitrogen in piggery digestive wastewater are toxic to the microorganisms in wastewater treatment systems. The ammonia nitrogen load can be decreased by struvite precipitation. The purpose of this paper was to take phosphate from magnesium-modified biochar adsorbed wastewater as a phosphorus source and add it to biogas slurry to reduce the ammonia concentration. The effects of phosphorus source dosage, initial reaction pH value and reaction time on ammonia nitrogen removal from biogas slurry were investigated, and then the subsequent biogas slurry underwent sequencing batch reactor biochemical treatment. When the phosphorus source dosage was 20 g/L, initial reaction pH value was 10.0 and reaction time was 1 h, the NH3–N recovery was 62.98%. The subsequent biogas slurry met the discharge standards (DB44/613–2009) after biochemical treatment. An innovative process for the recycling of pig farm waste, nitrogen and phosphorus recovery and advanced treatment of biogas slurry is first proposed in this paper.
123. 题目: Accurate observation of black and brown carbon in atmospheric fine particles via a versatile aerosol concentration enrichment system (VACES)
期刊: Science of The Total Environment
作者: Huihui Kang, Xiaona Shang, Munira Abdumutallip, Yunqian Chen, Ling Li, Xiaofei Wang, Chunlin Li, Huiling Ouyang, Xu Tang, Lin Wang, Yinon Rudich, Jianmin Chen
摘要: Carbonaceous aerosols (CAs) are major components of fine particulate matter (PM2.5) that dramatically influence the energy budget of Earth. However, accurate assessment of the climatic impacts of CAs is still challenging due to the large uncertainties remaining in the measurement of their optical properties. In this respect, a modified versatile aerosol concentration enrichment system integrated into optical instruments (VACES-OPTS) was set up to increase particle concentration and amplify signal-noise ratio during optical measurement. Based on the novel technique, this study was able to lower the detection limit of CAs by an order of magnitude under high temporal resolution (2 h) and small sampling flow (6 L min−1). Besides, stable and reliable optical data were obtained for absorption apportionment and source identification of black carbon (BC) and brown carbon (BrC). In the field application of the new system, high absorption coefficient of CAs in Shanghai, China was witnessed. Further analysis of the contribution of black carbon BC and BrC to light absorption revealed that BrC could account for over 15% of the total absorption at 370 nm. According to the potential source contribution function model (PSCF) classification, CAs with strong light absorption in urban Shanghai originated not only from highly polluted inland China but also from active marine ship emissions.
124. 题目: Phototransformation of the fungicide tebuconazole, and its predicted fate in sunlit surface freshwaters
作者: Luca Carena, Andrea Scozzaro, Monica Romagnoli, Marco Pazzi, Luca Martone, Claudio Minero, Marco Minella, Davide Vione
摘要: The fungicide tebuconazole (TBCZ) is expected to undergo negligible direct photolysis in surface freshwaters, but it can be degraded by indirect photochemistry. TBCZ mainly reacts with hydroxyl radicals and, to a lesser extent, with the triplet states of chromophoric dissolved organic matter (3CDOM*). Indirect photochemistry is strongly affected by environmental conditions, and TBCZ lifetimes of about one week are expected in sunlit surface waters under favourable circumstances (shallow waters with low concentrations of dissolved organic carbon, DOC, during summer). In these cases the time trend would follow pseudo-first order kinetics (mono-exponential decay). Under less favourable conditions, photoinduced degradation would span over a few or several months, and TBCZ phototransformation would depart from an exponential trend because of changing sunlight irradiance. The TBCZ phototransformation products should be less toxic than their parent compound, thereby providing potential for photodegradation to decrease the environmental impact of TBCZ. Hydroxylation is a major TBCZ transformation route, due to either ￼OH attack, or one-electron oxidation sensitised by 3CDOM*, followed by reaction of the oxidised transient with oxygen and water.
125. 题目: Insights into the molecular compositions of CX3R-type disinfection byproduct precursors in algal organic matter from algae-laden water
期刊: Chemical Engineering Journal
作者: Yuwei Wu, Lingjun Bu, Xiaodi Duan, Shiqing Zhou, John C. Crittenden
摘要: The precursors of commonly known DBPs have been widely investigated, yet few studies have paid attention to the typical compositions of AOM-related DBP precursors at molecular-level. Hence, in this study, we established the potential relationships by linking AOM molecular formulas or properties with the formation potentials of typical CX3R-type DBPs (i.e., dichloroacetonitrile (DCAN), trichloroacetone (TCP) and trichloromethane (TCM)) by regression analysis and Spearman’s correlation analysis. By the results of significant and strong correlations between AOM molecules and DBP formation potentials, the typical precursors of DCAN or TCP were observed to be the molecules with relatively high O/C (0.5-0.8) and low H/C (0.9-1.8) ratios, while different precursors of TCM were obviously determined. Compared to the aliphatic and vascular plant-derived polyphenol compounds, the phenolic and highly unsaturated aliphatic compositions were prone to generate DCAN and TCP in chlorination. Besides, the H/N and O/N ratios of precursors of DCAN distributed around a straight line, namely, H/N = 1.86 O/N + 1.23. Such findings will provide new insights into the specific precursors at molecular-level and be beneficial to the development of effective controlling strategies for these AOM-related DBPs.
126. 题目: Characterizing Molecular Weight Distribution and Optical Properties of Dissolved Organic Matter and Unraveling the Origins of Anthropogenic Fluorophores in Yangtze River and Its Tributaries
期刊: ACS ES&T Water
作者: Ya-Ping Wu, Wen-Xiang Ji, Fei Liu, Wu-Qiang Wang, Min-Hui Cai, Ye-Chao Tian, Yan-Ting Zuo, Peng Shi, Yan Li, Wen-Tao Li, Ai-Min Li
摘要: In this study, size exclusion chromatography (SEC) coupled with multiple detectors was used to characterize the composition, molecular weight (MW), and optical properties of dissolved organic matter (DOM) in the Yangtze River main stream and its 88 tributaries. The SEC chromatograms revealed that DOM in the investigated water samples mainly comprised nonhumic proteinaceous biopolymers with apparent MW > 20 kDa and humic substances with apparent MW ranging from ∼0.5 to ∼7 kDa. The SEC fluorescence chromatograms further unraveled that there was a kind of characteristic fulvic-acid-like fluorophore in downstream tributaries, which showed triple-excitation peaks at ∼250, 310, and 365 nm with an emission peak at ∼460 nm (designated as HS-Em460-Ex3 hereinafter). Via field investigation and parallel factor analysis, this characteristic HS-Em460-Ex3 fluorophore was identified to originate from the discharge of residual naphthol and naphthylamine moieties in biologically treated textile wastewater. The SEC fluorescence fingerprints also demonstrated the occurrence of the characteristic HS-Em460-Ex3 fluorophore in the Yangtze River main stream from Changzhou to Nantong, suggesting that the discharge of textile wastewater might have altered the optical properties of riverine DOM and advanced treatment processes should be applied to eliminate residual aromatic fluorophores in textile wastewater.
127. 题目: Composition of PAHs in Biochar and Implications for Biochar Production
期刊: ACS Sustainable Chemistry & Engineering
作者: Wolfram Buss, Isabel Hilber, Margaret C. Graham, Ondřej Mašek
摘要: The content of polycyclic aromatic hydrocarbons (PAHs) in biochar has been studied extensively; however, the links between biomass feedstock, production process parameters, and the speciation of PAHs in biochar are understudied. Such an understanding is crucial, as the health effects of individual PAHs vary greatly. Naphthalene (NAP) is the least toxic of the 16 US EPA PAHs but comprises the highest proportion of PAHs in biochar. Therefore, we investigate which parameters favor high levels of non-NAP PAHs (∑16 US EPA PAHs without NAP) in a set of 73 biochars. On average, the content of non-NAP PAHs was 9 ± 29 mg kg–1 (median 0.9 mg kg–1). Importantly, during the production of the biochars with the highest non-NAP PAH contents, the conditions in the post-pyrolysis area, where pyrolysis vapors and biochar are separated, favored condensation and deposition of PAHs on biochar. Under these conditions, NAP condensed to a lower degree because of its high vapor pressure. In biochars not contaminated through this process, the average non-NAP content was only 2 ± 3 mg kg–1 (median 0.5 mg kg–1). Uneven heat distribution and vapor trapping during pyrolysis and cool zones in the post-pyrolysis area need to be avoided. This demonstrates that the most important factor yielding high contents of toxic PAHs in biochar was neither a specific pyrolysis parameter nor the feedstock but the pyrolysis unit design, which can be modified to produce clean and safe biochar.
128. 题目: 13 C methodologies for quantifying biochar stability in soil: A critique
期刊: European Journal of Soil Science
作者: Phillip Chalk, Christopher Smith
摘要: Methodologies based on 13C-enrichment (E), 13C-depletion (D) and 13C-natural abundance (NA) to estimate the stability of biochar in soil were critically examined. Stability of 13C-enriched biochar can be estimated by the quantitative recovery of excess 13C, either in the soil or in evolved CO2. Both approaches have advantages and disadvantages. Recovery in soil is a measure of both residual biochar 13C + 13C immobilized in soil organic matter during biochar decomposition. Variable proportions of organic- and inorganic-C are present in alkaline biochars, and few data exist on the uniformity of labelling, which is a basic requirement of the respired 13CO2 and E methodology. The E technique has had limited application due to the cost and difficulty of obtaining a uniformly-enriched feedstock through continuous labelling of plants with 13CO2 at a constant 13C enrichment. In contrast, the NA technique has been widely applied. The NA and D techniques are in situ methods that involve addition of C4-derived biochar to a C3-soil or vice versa. Stability is estimated by a two-end-member mixing model that allows the proportion of evolved CO2 derived from the biochar (Cdfb) to be estimated. The mixing model has recently been misused to estimate the Cdfb of 13C-enriched biochar, with 13C-abundance expressed as erroneously large δ values. 13C-based methods provide a yardstick against which rapid stability tests should be evaluated. While numerous laboratory incubation comparisons have been conducted, very few field-based data have been published.
129. 题目: Photocatalytic TiO2@MIL-88A (Fe)/polyacrylonitrile mixed matrix membranes: Characterization, anti-fouling properties, and performance on the removal of natural organic matter
作者: Saman Salehian, Mohammad Hossein Mehdipour, Farzam Fotovat, Seyyed Abbas Mousavi
摘要: Photocatalytic membrane reactors (PMRs), coupling photocatalysts and membranes in a single system, have shown a considerable potential to reduce membrane fouling, which is one of the major drawbacks of using membranes to treat water and wastewater. In this study, the visible light-activated photocatalysts were incorporated into the polyacrylonitrile (PAN) casting solution to synthesize the photocatalytic composite membranes. The physicochemical properties and the morphology of the membranes and photocatalysts were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD), ultraviolet–visible diffuse reflectance spectroscopy (UV–visible DRS), photoluminescence (PL), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET), porosimetry, and contact angle analyses. The performance of the synthesized photocatalytic mixed matrix membranes (MMMs) in treating water containing humic acid, as one of the major components in natural organic matter (NOM) existing in drinking water sources, was investigated. Under visible light irradiation, the PAN/TiO2@MIL-88A (Fe) MMMs simultaneously adopted photocatalysis and membrane separation in the PMR and thereby enhanced humic acid removal and anti-fouling properties. The best synthesized photocatalytic membrane could remove 92.4% of the humic acid once exposed to visible light. The optimum membrane had suitable water permeability, a high flux recovery ratio (99.5%), and a 13.5% decline in the humic acid flux after a 10-h run, considerably lower compared to the corresponding decline of the pristine membrane (37.5% over the same period). The remarkable properties of the PAN/TiO2@MIL-88A (Fe) membrane, including its high anti-fouling specification, confirm the appropriateness of the synthesized MMM for treating water involving humic acid.
130. 题目: Distribution and storage of soil organic and inorganic carbon in steppe riparian wetlands under human activity pressure
期刊: Ecological Indicators
作者: Xinyu Liu, Xixi Lu, Ruihong Yu, Heyang Sun, Xiangwei Li, Xiang Li, Zhen Qi, Tingxi Liu, Changwei Lu
摘要: Soil organic carbon (SOC) and soil inorganic carbon (SIC) are key components of the global wetland soil carbon pool, which plays a crucial role in carbon cycling. However, research on carbon storage in riparian wetland soils, especially in inland steppe river environments impacted by human activities, is relatively scarce. Thus, we evaluated the SOC and SIC distributions and storage in riparian wetland soils under the pressure of human activities in the Xilin River Basin (XRB). We collected surface and profile soil samples, determined the SOC and SIC contents, aboveground biomass, and soil physicochemical properties, and calculated the SOC and SIC storage (SOCs and SICs) values. The surface soil SOC content decreased substantially from the upstream to the downstream zones (mean value range: 76.30–3.18 g/kg), and the SIC content showed the opposite trend (mean value range: 0.08–34.38 g/kg). The SIC content of the riparian wetlands along the permanently flowing stretch of river was much lower than that in the wetlands along the intermittently flowing stretch. In the XRB, the SOCs was primarily affected by vegetation coverage, soil water content, and soil pH, whereas the SICs was greatly affected by soil texture. A dry lake zone was markedly affected by wetland degradation, indicating a potential increase in the decomposition rate of the surface soil SOC; however, the SOC in the deep soils was relatively stable. The high SIC content most likely resulted from weathering, resuspension, and carbonate rock reprecipitation. Compared to different steppe grassland types, riparian wetlands appear to be potential hotspots of SOCs and SICs in the Inner Mongolian region. Riparian wetland SOCs in the upstream zones was substantially greater than in adjacent terrestrial locations. However, the SOCs in the downstream wetlands was similar to that in the grasslands. Under the impact of human activities, the water and soil environments in the downstream zone of the Xilin River were substantially modified, leading to severe wetland degradation, which most likely caused the carbon storage function of the riparian wetlands to weaken and carbon loss to accelerate. The mean SOCs in the riparian wetland soils decreased from 33.3 kg/m2 in the upstream area to 16.2 kg/m2 downstream, and the mean SICs increased from 2.3 kg/m2 to 34.6 kg/m2. Therefore, urgent measures are needed to restore the carbon sink function of river wetlands for long-term climate change mitigation.
131. 题目: Autogenic signals in the sedimentary record of organic carbon preservation
期刊: Geophysical Research Letters
作者: Yi Hou, Mark A. Torres
摘要: The burial of organic carbon (OC) preserves paleoenvironmental archives and drives the evolution of Earth’s biogeochemical cycles. While the impact of kinetic heterogeneity on OC preservation has been studied, the effects of sedimentation dynamics remain largely unknown. Here we incorporate the expected stochastic variability in sedimentation rates into a reactive-transport model, generate predictions for stratigraphic variability of OC burial efficiency, and compare the model outputs to field observations. We find that internal sedimentation dynamics profoundly influence OC preservation efficiencies and create autogenic signals that may obscure signals originated from external forcings. Simulations match observations in terms of power spectra when our model considers transient periods of erosion during net deposition, implying that the manifestation of sedimentation dynamics and their interactions with biogeochemistry in chemostratigraphic records are prevalent in nature. As sedimentary OC records reflect both internal variability and external forcing, they may be used as proxies for past depositional conditions.
132. 题目: Production and transformation of organic matter driven by algal blooms in a shallow lake: Role of sediments
期刊: Water Research
作者: YingXun Du, ShiLin An, Hu He, ShuaiLong Wen, Peng Xing, HongTao Duan
摘要: The generation of organic matter (OM) occurs synchronously with phytoplankton growth. Characterization of the generated particulate and dissolved OM during algal blooms in eutrophic lakes is crucial for better understanding the carbon cycle but remains limited. We speculate that sediments play a critical role in the biogeochemical transformation of OM derived from algal blooms in shallow lakes. In this study, changes in OM quantity and quality and the concentrations of biogenic elements (nutrients and metals) during algal blooms, were studied in situ in a shallow eutrophic lake (Lake Chaohu, China). Two enclosure treatments in the presence and absence of sediments were compared, and the cause-effect relationships among sediment, nutrients, metals, phytoplankton, particulate OM (POM), and dissolved OM (DOM) were revealed by a partial least square-path model (PLS-PM). The results showed that the changes in nutrients and metals concentrations over time were consistent with that of chlorophyll a (Chl a), and at the end of the treatment, the concentrations of Chl a, nutrients, and metals in Treatment S (with sediments) were approximately 3–5 times of those in Treatment N (without sediments). The high concentration of Chl a in Treatment S resulted in a high quantity of POM, which showed low molecular weight, low humification, and was enriched in protein-like components (∼70%). For DOM, the quantity increased after the decrease in POM, and DOM quality showed a significantly higher abundance of humic-like components and a higher molecular weight than POM did. The PLS-PM results showed that the significant positive effects of sediment on nutrients, metals, phytoplankton, POM, and DOM were 0.28, 0.37, 0.28, 0.25, and 0.25, respectively, suggesting that sediment had an important role in the biogeochemical cycles of these substances. The significant negative relationship between POM and DOM (-0.62) and the distinct difference in POM and DOM quality implied the efficient transformation of the freshly generated OM to those with a higher molecular weight, higher humification, and potentially refractory. Our results depicted the quick biogeochemical transformation of nutrients, metals, and potential formation of refractory organic carbon in water column, as driven by the couple of the algae pump with the microbial carbon pump.
133. 题目: Molecular Characterization of Organosulfate-Dominated Aerosols over Agricultural Fields from the Southern Great Plains by High-Resolution Mass Spectrometry
期刊: ACS Earth and Space Chemistry
作者: Gregory W. Vandergrift, Abu Sayeed Md Shawon, Darielle N. Dexheimer, Maria A. Zawadowicz, Fan Mei, Swarup China
摘要: The molecular composition of organic aerosols, especially for day/nighttime variations of organosulfates above agricultural fields, is not well understood despite profound impacts on regional climate, crop production, air quality, and human health. Here, nanospray desorption electrospray ionization with high-resolution mass spectrometry (nano-DESI-HRMS) is used to interrogate the molecular composition of organic aerosols collected at the Southern Great Plains, located in an agricultural region of Oklahoma. Identified molecular formulae featured carbon, hydrogen, oxygen (CHO), nitrogen (CHNO), and/or sulfur (CHOS, CHNOS), with higher organosulfate proportions during daytime (41%) compared to nighttime (30%). Nighttime aerosols featured increases in CHO, CHNO, and extremely low volatility organic carbon (ELVOC) species. However, due to high relative humidity, the nighttime aerosols phase state was found to be more liquid-like than daytime aerosols using parametrized glass transition temperatures. Aerosol molecular composition from an anthropogenically influenced plume (southerly winds) showed significant increases in CHOS and ELVOC species. By comparison with chamber studies, CHOS species are suspected to be of mixed biogenic and anthropogenic origin, whereas CHNOS species (not identified in the southerly winds) are suggested to predominately be of biogenic origin. Overall, this study provides key insight into organosulfates above agricultural fields, demonstrating dependence upon day/night cycles and episodic anthropogenic emissions.
134. 题目: Comparison of different chemical agents in the single extraction of some potentially toxic elements (PTEs) from contaminated soils
期刊: Environmental Earth Sciences
作者: Mohsen Jalali, Ziba Hurseresht, Faranak Ranjbar
摘要: Single-extraction methods are one of the common ways to study the mobility of potentially toxic elements (PTEs) in artificially contaminated soils. The present study was aimed to evaluate the power of eight chemical agents to mobilize five PTEs including cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), and zinc (Zn) in 25 soils spiked with two contamination levels (T1 and T2) and the effect of soil properties on PTEs extractable by different extractants using statistical analysis and multivariable regression. Regarding average values of the relative percentage of PTEs extracted of their total amounts in contaminated soils, EDTA was the strongest reagent except for Co, while NaNO3 was the weakest one. pH showed a negative correlation with CaCl2-extractable Cd, Co, Ni, and Zn, DTPA- and EDTA-extractable Ni, HNO3-extractable Cd, Co, Cu, and Zn, MgCl2-, NaNO3-, and NH4NO3-extractable Co, Ni, and Zn, and NH4OAc-extractable Cd, Co, and Zn. Cation exchange capacity (CEC) was negatively significantly correlated with HNO3-extractable Cd, while it had a positive significant correlation with MgCl2-extractable Cd. Organic matter (OM) showed a negative correlation with HNO3-extractable Cd and Zn, whereas it had a positive correlation with NH4NO3-extractable Cu. Equivalent calcium carbonate (ECC) was negatively significantly correlated with CaCl2-extractable Cd, Co, and Ni, EDTA-extractable Co, Cu, Ni, and Zn, HNO3-extractable Cd, Co, Cu, Ni, and Zn, MgCl2- and NaNO3-extractable Zn, NH4NO3-extractable Cd, Co, Ni, and Zn, and NH4OAc-extractable Cd and Co. According to the results, pH and ECC were the most effective parameters among soil properties in multivariable regression equations.
135. 题目: Effect of Biochar Addition on Phosphorus Adsorption Characteristics of Red Soil
期刊: Frontiers in Environmental Science
作者: Yunchao Wu, Ziwei Zou, Chenxu Huang, Jie Jin
摘要: Phosphorus (P) sorption by red soil is strong due to its acidic pH and high content of metal oxides. Biochar addition may increase the availability of red soil P by altering P sorption characteristics. This study examined the influences of doping ratios of the biochar, phosphate concentration, solution pH, and biochar-derived dissolved black carbon (DBC) on P sorption in red soil. The specific sorption mechanisms were explored using 3D fluorescence spectroscopy, infrared spectroscopy, and zeta potential analysis. The results show that the bioavailable P content in the biochar-amended red soil increased to 1.92 mg kg −1 , which is an increase of 255% compared with the original red soil. With the increase in the doping ratio of biochar, the maximum sorption amount of P initially decreased and then increased. Moreover, the pH value and the content of the dissolved organic carbon (DOC) of the red soil were effectively elevated by biochar addition. The increase in the DOC content is likely caused by the DBC released from biochar. As the soil pH value increased, the amount of P sorption was reduced due to electrostatic repulsion. P sorption by the red soil decreased with the increasing DBC concentration. The humic acid-like substances in DBC can compete with phosphate for soil sorption sites, leading to a decrease in P absorption. This study demonstrates that the addition of biochar affects P sorption of the red soil mainly by changing its physicochemical properties or by releasing DBC to occupy the sorption sites.
136. 题目: Twenty years of litter manipulation reveals that above-ground litter quantity and quality controls soil organic matter molecular composition
作者: Meiling Man, Derek Pierson, Ricky Chiu, Maryam Tabatabaei Anaraki, Lori VandenEnden, RenXi Ye, Kate Lajtha, Myrna J. Simpson
摘要: Global environmental change is altering the quality and quantity of plant inputs into soil. However, it is unclear how these long-term changes may fundamentally shift the biogeochemistry of soil carbon in forests. To better understand how varied detrital inputs alter soil organic matter (OM) biogeochemistry and composition at the molecular-level, soil samples were collected from a 20 year detrital manipulation experiment in an old-growth coniferous rainforest in Western Oregon. The experiment includes ambient (control) plots and six treatments: Double Litter, Double Wood, No Roots, No Litter, No Inputs and OA-less (replacement of O and A horizons with B horizon). Total soil carbon and nitrogen, molecular-level OM composition using solid-state 13C nuclear magnetic resonance, and targeted compound extractions were measured. Although soil carbon did not increase with Double Litter and Double Wood, microbial biomass and the decomposition of specific forms of soil OM (i.e., cellulose) increased, likely due to sustained soil priming over 20 years. Mineral (0–10 cm) soil carbon was similar across litter exclusion treatments (No Litter, No Roots, No Inputs), however, soil OM decomposition increased relative to the control. Microbial-derived lipids increased under Double Litter but decreased when above-ground litter was excluded. Notably, needle-derived lipids decreased with above-ground litter exclusion and root-derived compounds did not change under below-ground root exclusion. These results suggested that above-ground litter alters soil carbon biogeochemistry in surface soils to a greater extent than below-ground inputs. This study also demonstrated that long-term soil carbon biogeochemical trajectories were mostly governed by litter quality, quality and microbial processing of above-ground inputs.
137. 题目: Influence of Citrate and Phosphate on the Adsorption of Adenosine-5′-Monophosphate at the Hematite Water Interface
期刊: Frontiers in Environmental Science
作者: Sudipta Rakshit, Avedananda Ray, Ali Taheri, Michael E. Essington
摘要: Nucleic acid derived organic phosphorus (P o ) is an important source of plant available P when degraded to inorganic phosphate (P(V) i ). It is known that when nucleic acids or components are adsorbed on mineral surfaces, the enzymatic degradation is hindered or delayed. Thus, understanding adsorption/desorption mechanisms of nucleic acids and their derivatives are key to assess the biogeochemical pathways of P o cycling. Here we report adsorption mechanisms of adenosine-5′-monophosphate (AMP) on hematite, a common iron oxide mineral, under various solution properties using macroscopic and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic probes. The effects of citrate, mimicking organic acids from roots exudates, and the influence of P(V) i , representing inorganic fertilizer application, were also evaluated on the release of adsorbed AMP under various solution properties. The results suggested that AMP adsorbed with the hematite surface via the phosphate moiety, N 7 atom and the π electron systems of the adenine moiety. The presence of citrate significantly decreased the AMP adsorption, which was also corroborated by the negative phosphate IR bands in the results of AMP and citrate competitive adsorption experiments monitored by in situ ATR-FTIR probe. Like citrate, P(V) i also reduced AMP adsorption on hematite. Our findings suggest a potential novel pathway of nucleic acid derived P o cycling in the soil environment.
138. 题目: Cowpea induced physicochemical and biological rhizosphere changes in hydrocarbon contaminated soil
期刊: Plant and Soil
作者: A. A. Farouq, H. Y. Ismail, A. B. Rabah, A. B. Muhammad, U. B. Ibrahim, A. Y. Fardami
摘要: Purpose To understand the influence of cowpea on its rhizosphere physicochemical and biological conditions. Methods Pristine soil samples were contaminated with Bonny-Light crude oil and viable seeds of cowpea were planted to establish rhizosphere soil. Cowpea root exudates were collected and characterized while soil metabolic activities, physicochemical properties and rhizosphere effect were monitored following plant emergence. Results Cowpea root exudates were composed of organic acids, phenolics, carbohydrates and hydrocarbons. High rate of soil respiration and microbial biomass carbon were observed in the contaminated rhizosphere reaching its peak on 12th week (70.56 mgCO2g−1 day−1) and 10th week (23.18 mg/Kg) respectively. Lower rates of soil respirations and microbial biomass carbon were observed in contaminated (10.28 mgCO2g−1 day−1; 1.24 mg/Kg) and uncontaminated (0.23 mgCO2g−1 day−1; 0.37 mg/Kg) non-rhizosphere control soils respectively. The metabolic properties were positively correlated with soil organic matter contents and microbial size (r = 0.98; p < 0.05). There was considerable improvement in soil physicochemical properties in the cowpea rhizosphere as compared to non-rhizosphere soil. Microbial populations were generally improved with positive rhizosphere effect values (> 1) presumably due to the presence of compounds in exudates that promote microbial growth. Conclusion The results highlighted the influence of cowpea on its rhizosphere conditions which is a good indication for its ability to promote plant growth and environmental cleanup. Therefore, there is the need to further understand the microbial community dynamics in cowpea rhizosphere using culture-independent techniques.
139. 题目: Geographic patterns of soft-bottoms benthic communities in Chilean Patagonian fjords (47°S-54°S) - influence of environmental stress on diversity patterns and stable isotope signatures
期刊: Progress in Oceanography
作者: Eduardo Quiroga, Paula Ortiz, Eulogio H. Soto, Nicole Salinas, Nicole Olguín, Chester Sands
摘要: The benthic community in the Chilean Patagonia is as rich and highly diverse as the spatial variation of its habitats and food sources. Environmental stress from glacier melt and river discharge are known drivers of benthic community dynamics. Here, we analyze longitudinal patterns of soft-bottom benthic communities across transects of glacier-marine environments and how these habitats may respond to changes in the environmental conditions. To assess the relationships between environmental heterogeneity (marine and glacial habitats) and benthic biodiversity, this paper reviews biological (mega- and macroinfauna) and sedimentological dataset from multiple oceanographic campaigns in Chilean Patagonian fjords. Furthermore, we analyze isotopic compositions of epibenthic and macroinfaunal organisms (δ13C/δ15N and C/N) to determine particulate organic carbon (POC) and particulate organic nitrogen (PON) availability and organismal stoichiometric budgets within each benthic community. Our results showed that glaciomarine and glaciofluvial environmental stress negatively affected nutrient reservoirs and organic matter (OM) availability, and hence produced changes in benthic diversity and trophic structure throughout the fjords. These conditions shaped the benthic community where small-bodied polychaetes and opportunistic species dominated. Additionally, we found a strong relationship between OM and nutrient availability with faunal isotopic composition, but a decoupling in C/N ratios between fauna and sediment OM, suggesting preferential organic carbon use under limited nitrogen in fjord sediments.
140. 题目: Leguminous Caragana korshinskii evidently enhances microbial necromass carbon accumulation in dryland soils
作者: Bin Jia, Li Jia, Yanming Zhang, Xiao Ming Mou, Xiao Gang Li
摘要: The planting of nitrogen (N)-fixing leguminous plants is a common measure to restore degraded vegetation and sequester soil organic carbon (SOC) in globally vast arid areas where N deficiency is a limiting factor for plants. However, the effect of leguminous plants on microbial synthesized SOC accumulation remains a knowledge gap. We investigated the effects of planting shrubs (leguminous Caragana korshinskii and non leguminous Salix psammophila) in abandoned croplands on microbial substance accumulation in soil compared with natural succession (dominated by non leguminous semi-shrub Artemisia desertorum) in an arid area. Seventeen years after plantation, C. korshinskii increased SOC stock in the top 20 cm across canopy and gap areas by 34–80%, but S. psammophila did not affect SOC compared with abandonment (A. desertorum). This variation in the SOC stock across three vegetation types was not consistent with change patterns of aboveground litter accumulation and root biomass, but was consistent with higher living microbial biomass and non living microbial necromass contents in the soil and their proportions in the SOC under leguminous C. korshinskii than non leguminous A. desertorum and S. psammophila. These results indicated that the increased SOC under the leguminous relative to non leguminous species was mainly ascribed to the increased accumulation of microbial synthesized substances under the legume. Microbial necromass N represented 56–59% of total soil N under C. korshinskii, but this proportion was only 25–39% under non leguminous species, responding to much greater plant N input and soil N availability under the legume. Therefore, we suggest that symbiotic N fixation by leguminous species increased the production of microbial biomass and potentially decreased the reuse of N from microbial necromass compared with non leguminous species. As such, legumes can efficiently increase the net accumulation of microbial necromass carbon and thus the SOC content in dryland soils.