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22921. 题目: Effects of polymer aging on sorption of 2,2′,4,4′-tetrabromodiphenyl ether by polystyrene microplastics The sorption behavior of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) on aged polystyrene (PS) microplastics via seawater soaking, ultraviolet (UV) irradiation, seawater soaking and UV irradiation together was investigated. The effects of environmental factors including salinity, pH, and dissolved organic matter (DOM) on sorption of BDE-47 by the aged PS microplastics were analyzed. The equilibrium sorption capacity of BDE-47 by virgin PS, aged PS with seawater soaking, aged PS with UV irradiation and aged PS with seawater soaking and UV irradiation was 6.16, 4.96, 3.53, and 3.75 ng/g, respectively. The decrease in sorption capacity was related to the increase of surface crystallinity and the appearance of surface oxygen-containing functional groups. The kinetic and isotherm models suggested that aging did not change the sorption mechanism of BDE-47 on PS microplastics. pH had negligible impacts on BDE-47 sorption by virgin and aged PS. Sorption capacity of BDE-47 on aged PS in water with high salinity was lower than that on virgin PS, and DOM has less effect on the sorption of BDE-47 on aged PS. | |||||
22922. 题目: Effects of lead (Pb) in stormwater runoff on the microbial characteristics and organics removal in bioretention systems Bioretention systems have been proved to be a natural approach for effectively reducing stormwater runoff pollution loads. However, the effects of heavy metals in stormwater runoff on microbial characteristics and organics removal in bioretention systems are unclear. In this study, two lab scale bioretention columns including the control and lead (Pb) treatment with the soil and filler layer were established. The changes of organic matter and lead in the effluent water and the soil (or fillers) were monitored during 121 operation days. The soil (or fillers) microbial characteristics were also analyzed. The results showed that most of Pb was intercepted by soil, while a small amount accumulated in fillers after 121 days. The long-term Pb accumulation in the biorentention system negatively affected the microbial biomass and microbial activity, while positively affected the community diversity. Pb accumulation killed some microorganisms, but simultaneously stimulated the growth of some Pb-tolerance microorganisms. The abundance of bacteria with COD degradation function in soil layer decreased, while that in fillers increased, indicating the effect of Pb on the community structure of these two layers was different. The COD removal in the soil and filler layer was promoted and inhibited by Pb contamination respectively. Moreover, Pb affected the removal of organic matter by chelating organic matters and changing their composition. The results suggested that the long-term accumulation of heavy metals in bioretention system would affect microbial degradation function and pollutants removal, causing our concern for the long-term maintenance of the bioretention system. | |||||
22923. 题目: Enhanced fuel characteristics and physical chemistry of microwave hydrochar in sustainable fuel pellet production via co-densification Microwave assisted hydrothermal treatment (MHTC) was compared with torrefaction in terms of carbonization efficiency and physicochemical characteristics of char products. The utilization of produced char was optimized for composite solid biofuel production. The results show that MHTC significantly improved the binding capability of the microwave hydrochar (MHC) particles during co-densification with unprocessed biomass and coal. One possible contributor to the improved binding is the pseudo lignin formed during the MHTC, which led to a better interlocking of the feedstock particles and promoted the solid bridge formation. Composite pellet prepared with 80 wt% of torrefaction char (TC-120), 10 wt% of microwave hydrochar (MHC-30), and 10 wt% of Coal-04 showed a higher heating value of 24.54 MJ/kg and energy density of 26.43 GJ/m3, which is significantly higher than that of the raw cotton stalk pellet (16.77 MJ/kg and 18.76 GJ/m3, respectively), showing great promise as a solid biofuel. The moisture resistance and oxidation reactivity are also significantly improved. The results demonstrate that MHCs provides dual functionalities in acting as binder and fuel promoter in the production of composite biofuel. This study can provide new insight into the unique functions of MHC during fuel application, which demonstrates the great potential of applying MHTC in energy recovery from lignocellulosic biomass. | |||||
22924. 题目: Anammox Biofilm System under the Stress of Hg(II): Nitrogen Removal Performance, Microbial Community Dynamic and Resistance Genes Expression The existence of heavy metals in wastewater has obtained more attention due to its high toxicity and non-degradability. In this study, we investigated the changes of anaerobic ammonium oxidation (Anammox) system under long-term invasion of Hg(Ⅱ). The results indicated that the total nitrogen removal efficiency (TNRE) dropped to around 55% as Hg(Ⅱ) concentration went up to 20 mg L-1. But the functional bacteria rapidly developed some resistant abilities and maintained a stable TNRE of 65% till the end of test. The maximum relative expression fold change of merA, merB, merD and merR were 468.8476, 23.7383, 5.0321 and 15.2514 times, respectively. The high positive correlation between the expression abundance of metal resistance genes and the concentrations of Hg(Ⅱ) revealed the resistant mechanisms of microorganisms to heavy metals. Moreover, the protective strategy based on extracellular polymeric substances also contributed to the stability of Anammox system. | |||||
22925. 题目: Enhanced excretion of extracellular polymeric substances associated with nonylphenol tolerance in Dictyosphaerium sp Dictyosphaerium sp. is tolerant to nonylphenol (NP); however, knowledge regarding the mechanisms involved in NP tolerance is limited. In this study, a batch of algal culture experiments were carried out to elucidate the underlying mechanisms by investigating the production and composition of extracellular polymeric substances (EPS) in algae exposed to NP. The excretion of EPS was significantly enhanced (P < 0.001) in algae exposed to 4 and 8 mg/L of NP. The polysaccharides in soluble EPS and the proteins in bound EPS were specifically overproduced. The three-dimensional excitation and emission matrix fluorescence spectra analyses indicated that tyrosine- and tryptophan-like substances were the main functional compositions in the proteins of EPS. In addition, enhanced EPS secretion significantly alleviated the toxicity of NP to the algae by the reduction of cell internalization, as indicated by the higher IC50, biomass, and cell growth rate in the algae with EPS. These discoveries along with the characterizations by algal cell surface hydrophobicity analysis, scanning electron microscopy, and Fourier transform infrared spectra spectroscopy demonstrated the vital role of EPS in the algal resistance to NP. | |||||
22926. 题目: Rice husk biochar influences runoff features, soil loss, and hydrological behavior of a loamy soil in a series of successive simulated rainfall events As biochar affects soil hydrological processes, a detailed laboratory experiment was run to investigate the effect of three biochar application rates of 1, 2, and 3 kg m−2 under three successive simulated rainfall events (three rounds) with about 10-day intervals on runoff rate, soil loss, salinity of runoff and percolated water of a loamy soil. Rice husk biochar produced in 600 °C for four hours was mixed in the top 0–1.5 cm of the soil surface. A simulated rainfall intensity of 28 mm h−1 was applied for 60 min over the soil bins measuring 1.4 m × 1.4 m × 0.1 m. Results showed that the 3 kg m−2 application of biochar prevented runoff generation, and consequently there was no soil loss. The 2 kg m−2 application of biochar significantly reduced runoff rate, runoff coefficient, and soil loss compared to the 1 kg m−2 and the control (no biochar application). In addition, the 2 kg m−2 application of biochar significantly increased the time to runoff generation, which clearly implies an appropriate amount of biochar could control runoff rate and soil loss. The rainfall rounds had significant effects on the time to runoff generation, total soil loss, and the peak of runoff salinity. A combined analysis showed that a power function can be satisfactorily fit to the runoff and soil loss rates. In terms of environmental concerns of biochar application, results revealed that rice husk biochar might not be an environmental threat and the salinity of runoff and percolated water were lower than 1 dS m−1. In conclusion, this study showed that rice husk biochar at certain amounts could be used to reduce or prevent runoff and soil loss in loamy soil in a semi-region area. | |||||
22927. 题目: Effect of salt and metal accumulation on performance of membrane distillation system and microbial community succession in membrane biofilms Membrane distillation (MD) works as a potential technology for the zero liquid discharge water treatment owing to its high concentration brine tolerance. The continuous accumulation of salts and metals in the MD system during the zero liquid discharge water treatment inevitably posed remarkable impacts on the biofilm formation as well as the MD performance. Hence, the biofouling mechanism of MD was deeply researched in this study with an emphasis on the roles of salt-stress (NaCl) and metal-stress (Zn and Fe) in biofilm development. The membrane flux decline of MD was effectively mitigated by the appearance of NaCl and ZnO, while that was significantly aggravated under the metal-stress of Fe. Considering the serious membrane scaling caused by NaCl crystals, a sharp flux decline was seen for the NaCl group during the later stage of MD operation. Basing on the 16S rDNA and 16S rRNA analysis, heat-stress, salt-stress, and metal-stress all posed certain impacts on the biofouling development in the MD system, and a more remarkable influence was observed for metal-stress. Under the salt-stress from NaCl, a thin biofilm containing high biovolume of dead cells finally formed, in which the bacterial community mainly consisted of halotolerant and thermophile species. Owing to the Zn2+-stress and oxidation-stress mechanisms of ZnO, the bacteria in the MD system were largely dead and live bacterial community in biofilms was dominated by some gram-negative species. Under the metal-stress from Fe, a rather thick biofilm containing higher biovolume of live cells clearly developed, in which the prevailing species could secret large amounts of EPS and accumulate metabolites around cells as biological surfactants, inducing aggravated membrane biofouling and high risk of membrane wetting. | |||||
22928. 题目: Contamination and ecological risk assessment of the Red Sea coastal sediments, southwest Saudi Arabia The level of heavy metals (HMs) in coastal sediments has attracted the environmental researchers due to their persistence, abundance, biomagnification and toxicity. The present study was conducted to assess the contamination and ecological risk assessment of HMs in Jazan coastal sediments, Red Sea, Saudi Arabia utilizing pollution indices and multivariate statistical analyses. A total of 32 surface samples were collected for Cu, Sb, Zn, Cr, Cd, Pb, Fe, Co, Ni, Al, and total organic matter analysis using an atomic absorption spectrophotometer. The results indicate the following descending order of metal concentrations: Al > Fe > Cr > Cu > Zn > Ni > Co > Pb > Cd > Sb. Average level of Cd is significantly higher than those from many neighboring and worldwide coastal sediments; and recorded very severe enrichment, severe contamination and very high risk in the investigated sediments. The pollution indices and statistical analyses revealed that proportion of Zn, Fe, Ni, Cr, Al, Cu, Sb and Pb were formed from lithogenic sources of weathering Quaternary units and atmospheric deposition. Most of the Cd, Sb, and Pb levels were derived from anthropogenic sources of industrial, agricultural, and fishing activities. The higher contribution of organic matter may be attributed to the mangrove roots and organic fertilizers; and played a key role in adsorbing, transferring and accumulating of elements. | |||||
22929. 题目: Effect of the coupling modes on EfOM degradation and fouling mitigation in ozonation-ceramic membrane filtration To guide the practical application of ozonation coupled with tubular ceramic membranes (TCMs), the performance and the mechanism of mitigated membrane fouling by pre-ozonation-filtration (Pre-O/F) and in-situ ozonation-filtration (in-situ-O/F) were investigated. The in-situ-O/F mode exhibited a rejection performance 1.19 times better than that of Pre-O/F for effluent organic matter (EfOM) removal, but less membrane fouling mitigation. The backwashing efficiency of the in-situ-O/F mode was better than that of Pre-O/F, because backwashing loosened the in-situ-O/F membrane fouling layer and made it easier to remove by backwashing. SEM-EDX measurements were used to identify the components of the inorganic, organic, and biofouling membrane fouling layers. In Pre-O/F mode, EfOM, extracellular polymeric substances, and microorganisms in the effluent were destroyed by ozonation before filtration. In in-situ-O/F mode, the adhesion between irreversible membrane fouling and the pores/surfaces of TCMs was destroyed by ozonation, thus converting the irreversible membrane fouling to reversible membrane fouling. This led us to propose the process strategy of filtration coupled with ozonation for reclaimed water treatment. Pre-O/F is suitable for use in the treatment of large amounts of wastewater in short times because of the high-water flux. The in-situ-O/F mode is more suitable for normal use because of its lower operating cost and higher efficiency. | |||||
22930. 题目: Newly created farmland should be artificially ameliorated for agricultural production on the Loess Plateau The farmland area on Loess Plateau have been reduced because of the Grain for Green Project and other soil conservation measures. Gullies Reclamation for Farmland project has been implemented to increase the farmland areas. Many farmlands have been created, but their suitability for sustainable crop production and sustainable management practices is unknown. Topsoil was sampled from 119 sites to evaluate the soil fertility parameters (e.g., SOM, nitrogen, phosphorus, clay). We found that (1) overall fertility was lower than the soil fertility III level criterion of Shaanxi Province except for the potassium due to the loess parent materials where nutrients were at low levels except for potassium and was extremely unfavorable for crop growth; (2) the distribution of soil fertility properties and quality were variable on the Yan'an regions and especially lowest in the northern areas because of slightly precipitation and vegetation coverage, as well as lack of SOM, nitrogen and phosphorus (3) cultivation was the better choice for soil fertility restoration at short‐term in view of the higher enzyme activities and the contents of SOM, nitrogen and phosphorus. The minimum data set for this type of soil quality analysis was determined to be SOM, CEC, NaHCO3‐P, Clay, DTPA‐Fe, DTPA‐Zn and S‐UE. We recommend to planting of Medicago sativa and other legume crops in the uncultivated newly created farmland rather than letting it recover naturally. It is necessary to apply organic fertilizers, chemical fertilizer and micro‐elements simultaneously and not rely solely on chemical fertilizers in the utilization of newly created farmland. This article is protected by copyright. All rights reserved. | |||||
22931. 题目: Priming of soil organic carbon induced by sugarcane residues and its biochar control the source of nitrogen for plant uptake: A dual 13C and 15N isotope three-source-partitioning study Sugarcane (Saccharum spp.) farming systems globally have largely transitioned away from burning the crop prior to harvest. Harvesting the sugarcane crop 'green' results in large volumes of biomass residues being left on the soil. Despite this, there is little evidence for increased soil organic carbon stocks. We investigated the role of surface application or incorporation (0–200 mm soil layer) of harvest residues (15 t dry weight residues ha−1) and its biochar (5.4 t ha−1 based on the quantity of resource recovered after pyrolysis) on the priming of native soil organic carbon (SOC), the mineralisation of the organic amendments and the source of crop N uptake (SOC, organic amendment or urea). All treatments received urea at 180 kg N ha−1. To achieve the separation of C and N sources, dual 13C and 15N-enriched sugarcane residues and corresponding biochar (350 °C) were used in an 84-d controlled environment study. A three-pool isotope mixing model, utilising two levels of 13C enrichment in residue (16.6‰ and 23.8‰) and biochar (16.8‰ and 24.1‰), was also applied to partition the C from three sources: 1) root respiration, 2) organic amendment mineralisation, and 3) SOC priming. The SOC mineralisation was increased following both surface-applied and incorporated residues, over the nil organic amendment (control) by 72.3 and 78.3 CO2–C m−2 respectively over 84 days. In contrast, biochar lowered the mineralisation of SOC by 62.9 g CO2–C m−2 compared to the control. The cumulative mineralisation of sugarcane residue biochar (18.9 g CO2–C m−2) was lower (P = 0.03) than surface applied residue (50.1 g CO2–C m−2) and incorporated residue (71.9 g CO2–C m−2) over the study period. While there were no differences in total crop N uptake between the organic-amended soils and the control, the source of N was significantly different. The sugarcane plants utilised 31.0% and 29.4% of the supplied urea N in the nil organic-amended control and biochar treatment, respectively. This was significantly reduced to 24.8% and 20.6% in the surface residue and incorporated residue treatments, respectively. In comparison, the plant uptake of N derived from the organic amendments was 27.8%, 15.4% and 6.4% from incorporated residues, surface-applied residues and biochar, respectively (P < 0.001). Results suggest that the increased mineralisation of SOC, partly driven by the high C:N ratio (73:1) and the unbalanced nutrient stoichiometry may lead to low SOC accumulation from surface residue application and that sugarcane residue biochar results in SOC stabilisation and an increase in the use efficiency of fertiliser N in sugarcane systems. | |||||
22932. 题目: Preparation of high porosity biochar materials by template method: a review | |||||
22933. 题目: Effects of biochar content on gas diffusion coefficient of soil with different compactness and air contents | |||||
22934. 题目: Eco-compatible biochar mitigates volatile fatty acids stress in high load thermophilic solid-state anaerobic reactors treating agricultural waste A high concentration of accumulated volatile fatty acids (VFAs) is one of the most important factors resulting in reactor failure during solid-state anaerobic digestion. In this study, the feedstock-to-inoculum (F/I) ratio (0.5, 2, 3, 4 and 6) and the recovery method after failure (biochar addition or inoculum addition) were investigated in batch solid-state anaerobic digestion fed with rice straw and pig urine. An F/I ratio of 3 was the threshold for stable operation, while the reactors failed at F/I ratios of 4 and 6 because of high accumulated VFAs concentrations (above 30 g HAc/kg). Biochar addition (10% or 20% (wet weight) of the mixture) was as effective as inoculum addition (by adjusting the F/I ratio to 2 or 3) in promoting VFAs degradation in failed reactors within a short period (<1 day). The buffering capacity of biochar was important in promoting VFAs degradation. | |||||
22935. 题目: Simultaneous removal of Cd(II) and As(III) by graphene-like biochar-supported zero-valent iron from irrigation waters under aerobic conditions: synergistic effects and mechanisms Irrigation water is commonly contaminated with cadmium and arsenic near mining regions, which significantly contributes to excessive heavy metals in rice grains. Herein, we have developed a novel graphene-like biochar (GB)-supported nanoscale zero-valent iron (nZVI) and the underlying mechanisms of synergistic effects between GB and nZVI for the simultaneous removal of Cd(II) and As(III) under aerobic conditions. The results show that GB/nZVI has a high removal capacity of 363 mg/g (nZVI) for As(III) at pH 4 and 92.8 mg/g (nZVI) for Cd(II) at pH 7. These values are significantly higher than GB and nZVI (1.7 times for Cd(II); 1.4 times for As(III)) alone, suggesting strong synergistic effects between GB and nZVI. GB promotes nZVI oxidation to form iron oxyhydroxides and causing 35% of As(III) converting to As(V). Importantly, As(III) significantly enhance Cd(II) removal by GB/nZVI (i.e., 131.8 mg/g as nZVI). Coexisting ions such as phosphate and humic acid have stronger inhibitory effect on the simultaneous removal of Cd(II) and As(III). Our results indicate that oxidation and surface complexation are the dominant mechanisms and electrostatic binding exists for As(III) removal, while surface complexation predominates for Cd(II) removal. These findings provide insight into developing effective solution for removing Cd(II)/As(III) from irrigation waters. | |||||
22936. 题目: Inferring earthworms' impact on the stability of organo-mineral associations by Rock-Eval pyrolysis and 13C NMR spectroscopy Stabilization of organic matter (OM) against decomposition and its de-stabilization leading to mineralization are important processes controlling greenhouse gas emissions and carbon sequestration in soils. Soil organisms, particularly earthworms, may greatly influence these processes through their potential impact on the interaction of OM with clay minerals, a mechanism which may protect OM at medium (years) to long (decades, centuries) time scales. The aim of this study was to use earthworms and pure minerals in order to enhance carbon sequestration through the formation of aggregates containing particulate OM and organo-mineral associations during a composting experiment. To this end we compared OM transformations in composting treatments with and without (i) clay minerals (montmorillonite) and (ii) epigeic earthworms (Eisenia andrei and Eisenia foetida). We used density fractionation of the end-products to quantify the amount of aggregates including organo-mineral associations formed during 196 days. Their chemical composition and stability were analyzed by elemental analyses, Rock-Eval 6 pyrolysis and solid-state 13C nuclear magnetic resonance spectrometry. Our results indicated that the addition of minerals led to the formation of heavy fractions most probably containing aggregates and organo-mineral associations in treatments with and without earthworms. While OM showed higher oxidative transformation in all treatments, addition of earthworms changed organic carbon (OC) and nitrogen (N) concentrations in specific density fractions and increased the thermal stability of OM in heavy density fractions. These fractions contained higher proportions of aromatic and proteinaceous material. We conclude that earthworms under composting conditions may be able to effectively stabilize OM, though the formation of aggregates and/or organo-mineral associations containing greater proportions of microbial-derived material. | |||||
22937. 题目: Estimation of adsorption/desorption Freundlich's affinity coefficients for oxytetracycline and chlortetracycline from soil properties: Experimental data and pedotransfer functions Tetracycline antibiotics spread in the environment constitute a real threat, causing risks that should be controlled. Retention/release of these compounds after interacting with soil components are the main process governing their entry into water bodies, plant uptake, and availability for soil microorganisms. In this work, batch-type experiments were performed to study adsorption/desorption of oxytetracycline (OTC) and chlortetracycline (CTC) in 63 crop soils. The Freundlich model satisfactory described adsorption curves, showing strong affinity of both antibiotics to soils, with adsorption coefficient (KF(ads)) values between 1015 and 9733 Ln μmol1−n kg−1 for OTC, and between 1099 and 11344 Ln μmol1−n kg−1 for CTC. Desorption percentages were always lower than 10%, indicating that adsorption is highly irreversible. Furthermore, the desorption coefficient (KF(des)) correlated positive and significantly with KF(ads), showing that those soils characterized by higher adsorption were also those showing less desorption. Soil organic carbon (SOC) was the soil characteristic that most explained the variance of KF, both for adsorption and desorption, which caused that soils with higher SOC scores showed higher adsorption and lower desorption for both antibiotics. Pedotransfer functions were developed for OTC and CTC, and resulted effective to satisfactory predict KF(ads) and KF(des) values. These equations would facilitate an easy identification of soils vulnerable to antibiotics pollution, which would allow to program appropriate management practices to decrease undesirable effects on the environment and on public health. | |||||
22938. 题目: Oxidation of congo red by thermally activated persulfate process: kinetics and transformation pathway The degradation of Congo Red (CR) in thermally activated persulfate (PDS) oxidation (TAP) system was investigated in this study. Effects of chloride (Cl-), carbonate/bicarbonate (HCO3-/CO32-), natural organic matter (NOM), and operating parameters including reaction temperature, solution pH, and PDS dosage on the observed pseudo-first-order rate constants for CR degradation (kobs) were evaluated. The calculated activation energy of CR in TAP system was approximately 76(±0.8) KJ mol-1 within the range of 313∼353 K, and CR could be degraded effectively. The removal efficiency of CR increased with increasing the activation temperature (20-80 ℃) and dosage of PDS (0.1-5.0 mM). The change of pH could not affect the removal of CR directly, but the lower scavenging effect of dihydrogen phosphate than hydrogen phosphate resulted in faster degradation of CR in acidic conditions (i.e., pH= 5 and 7) than alkaline condition (i.e., pH=9). The presence of high-concentration of Cl- and CO32-/HCO3- (> 1.0 mM) could accelerate the degradation of CR in TAP system, which was attributed to the contribution of those secondary radicals (i.e., chlorine radicals, carbonate radical). The presence of NOM could inhibit the degradation of CR effectively, which could be explained by the sulfate radical (SO4-·) scavenge effect of NOM. Further, seven degradation products were detected in the reaction of CR with SO4-·. A tentative pathway was proposed, where the SO4-· attack the -SO3-, -NH2 functional group and -C-C- bond by electron transfer reactions. These results indicated that CR could be degraded effectively in TAP system under various conditions. | |||||
22939. 题目: A comparative study on the use of palm bark as a supplementary carbon source in partially saturated vertical constructed wetland: Organic matter characterization, release-adsorption kinetics, and pilot-scale performance In this study, a comparative investigation of palm bark and corncob (a well-investigated material) for enhancing nitrogen removal efficiency in partially saturated vertical constructed wetland (PSVCW) was performed to evaluate an effective and cost-effective supplementary carbon source. The characteristics of the released organic matter and the release processes were analyzed through optical property characterization and a first-order release-adsorption model, respectively, and the nitrogen removal performance was evaluated in a series of pilot-scale PSVCWs. Results showed that the amount of organic matter released per unit mass of corncob was larger than that released per unit mass of palm bark under the same pretreatment conditions (control, heat, and alkaline pretreatment). The organic matter released from corncob has a higher apparent molecular weight and a higher degree of aromatic condensation than those of the organic matter released from palm bark, whereas the organic matter released from palm bark has higher and more stable bioavailability. Moreover, palm bark showed a more significant improvement of release capacity with the heat and alkaline pretreatment methods. Pilot-scale studies revealed that PSVCW using palm bark as the supplementary carbon source has a longer replacement cycle and higher total nitrogen (TN) removal efficiency than that using corncob, indicating that palm bark can be considered an effective and inexpensive supplementary carbon source. This study provides initial guidance for the ongoing research on supplementary carbon sources for improving nitrogen removal efficiency in constructed wetlands. | |||||
22940. 题目: Potential use of biochar and rhamnolipid biosurfactant for remediation of crude oil-contaminated coastal wetland soil: Ecotoxicity assessment Remediation of wetland soils contaminated with petroleum hydrocarbons is a challenging task. Biosurfactant and biochar have been used in oil remediation. However, little is known about the ecotoxicity of these materials when applied in wetland ecosystems. In this study, the ecotoxicity of biochar and rhamnolipid (RL) biosurfactant as crude oil remediation strategies in a Louisiana wetland soil was investigated. A pot experiment was set up with wetland soil treated with/without crude oil followed by subjecting to application of 1% biochar and various levels of RL ranging from 0.1% to 1.4%. The ecotoxicity was evaluated regarding to high plant (S. Alterniflora), algae, and soil microbes. Specifically, after a 30-day growth in a controlled chamber, plant biomass change as well as shoot/root ratio was measured. Algae growth was estimated by quantifying chlorophyll by spectrometry following separation, and soil microbial community was characterized by phospholipid fatty acids analysis. Results showed that plant can tolerate RL level up to 0.8%, while algae growth was strongly inhibited at RL > 0.1%. Algal biomass was significantly increased by biochar, which offset the negative impact of oil and RL. Additionally, soil microbial community shift caused by crude oil and RL was alleviated by biochar with promoting Gram-positive bacteria, actinomycetes, and arbuscular mycorrhizal fungi. Overall, this study shows that integrated treatment of biochar and RL has the lowest ecotoxicity to plant and algae when used in oil remediation of contaminated wetland soils. | |||||
