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Titanium dioxide nanoparticles (TiO2 NPs) can potentially impact constructed wetlands (CWs). The aim of this study was to investigate the rapid impacts on nitrogen removal performance and on the microbial community after short-term exposure to TiO2 NPs in CWs, which were determined via 16S rDNA amplicon sequencing and Biolog-Eco technologies. The results showed that removal efficiencies declined by 23.9%, 32.2%, and 38.8% for ammonia nitrogen (NH4+-N) and by 26.5%, 43.4%, and 71.4% for nitrate nitrogen at TiO2 NP concentrations of 50, 100, and 150 mg/L, respectively. Bacterial damage and TiO2 NP agglomeration on the packing increased as the TiO2 NP concentration increased. Microbes showed different tolerances against TiO2 NPs, and members, such as the bacteria removing organic pollutants and NH4+-N, were susceptible to TiO2 NPs. The order of microbial utilisation of the six carbon sources was determined, and the utilisation ratios declined as TiO2 NP concentration increased. The concentration of 50 mg/L TiO2 NPs impaired the functions of nitrifiers and denitrifiers in CWs after short-term exposure, and higher concentrations (100 mg/L and 200 mg/L) had no additional negative impact on the packing compared with the concentration of 50 mg/L. [ABSTRACT FROM AUTHOR]

The aim of this meta-analysis was to synthesize the effects of biochar amendment on soil enzyme activities (SEAs) related to carbon (C), nitrogen (N), and phosphorus (P) cycling. Based on 401 paired comparisons from 43 published studies, the SEAs and main influential factors were analyzed in response to biochar characteristics, soil properties, and experiment conditions. Results showed that biochar additions to soils overall increased the N- and P-cycling SEAs by 14 and 11%, respectively. The enhancement of the N- and P-cycling SEAs was mainly attributable to the microbial stimulation by biochar properties (i.e., nutrient content and porosity) and soil nutrients (e.g., soil organic C and total N). The enhancement was the most significant under the conditions with biochars produced at low temperatures and using feedstock materials with high nutrient content, and biochar applications in acidic or neutral soils, coarse or fine soils, and farmland soils. Biochar additions to soils overall reduced the C-cycling SEAs by 6.3%. The C-cycling SEAs were greatly suppressed under the conditions with low and very high biochar loads, biochars produced at high temperatures and with feedstock materials of herb and lignocellulose, and biochar applications in alkaline, fine, and forest soils. The results were mainly related to the adsorption and inhibition effects of biochars and soil properties (e.g., liming effect, high biochar porosity and aromatic C content) on fungi and the enzymes. Biochar feedstock, C/N and load, and soil total N were the main influential factors on the SEAs. The results from this study demonstrate that biochar amendment is beneficial to improving soil N and P cycling and C sequestration. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study was to investigate the effects of amendment of different biochars on the physical and hydraulic properties of desert soil. Materials and methods: Biochars were produced with woodchip, rice straw, and dairy manure at temperatures of 300 and 700 °C, respectively. Each biochar at 5% (w/w) was mixed with desert soil, and the mixtures were incubated for 120 days. Results and discussion: The different biochar treatments greatly reduced soil bulk density and saturated hydraulic conductivity. Especially the rice straw biochar addition resulted in the lowest saturated hydraulic conductivities among the treatments. Biochar addition significantly increased water retention of desert soil at any suction. At the same suction and experimental time, the treatment with the rice straw biochar produced at the lower temperature resulted in higher water content than the other treatments. The biochar additions slightly enhanced formation of soil macro-aggregates in the early experimental time. However, the aggregate contents gradually decreased with time due to the lack of effective binding agents (e.g., soil organic matter and clay minerals). Conclusions: The changes of hydraulic properties of desert soil were attributable to the biochar properties. The higher fine particle content, porosity, and surface hydrophilicity of rice straw biochars were the most beneficial properties to increase soil water retention and to reduce water flow in the desert soil. The improvement of hydraulic properties by biochar addition may provide a potential solution to combat desertification. [ABSTRACT FROM AUTHOR]

Purpose: The addition of organic substrates can change the decomposition rate of soil organic matter (SOM), which is termed as "priming effect." The objective of this study was to explore the priming effects of SOM decomposition with the addition of different organic carbon substrates, including glucose, oxalic acid, and tannin. We hypothesized that with additions from labile to recalcitrant carbon substrates, the soil priming effects changed from positive to negative.Materials and methods: Representing from labile to recalcitrant carbon substrates, glucose, oxalic acid, and tannin were added to soil, respectively. Physicochemical properties of soil, carbon dioxide emission rate, soil organic carbon in the labile and recalcitrant carbon pools, microbial biomass carbon (MBC), and microbial community diversity and structure were measured in different treatments.Results and discussion: Results showed that the addition of glucose and tannin produced positive priming effects, while the addition of oxalic acid led to a negative priming effect. The addition of glucose and tannin significantly increased the MBC. The addition of glucose significantly promoted the carbon decomposition in both the labile and recalcitrant soil carbon pools. The addition of tannin greatly promoted carbon decomposition in the labile carbon pool and slightly decreased carbon decomposition in the recalcitrant carbon pool of the soil. However, the addition of oxalic acid reduced the MBC and resulted in insignificant changes of the different soil carbon pools. The addition of organic carbon substrates reduced the soil microbial community diversity, especially the addition of glucose. The different priming effects of the treatments with glucose and tannin were attributable to the different phases in the succession of SOM decomposition processes. The treatment with oxalic acid reduced the soil pH, resulting in inactive microbial growth and reproduction.Conclusions: The addition of both glucose (labile carbon) and tannin (recalcitrant carbon) produced positive priming effects. In contrast, the addition of oxalic acid produced a negative priming effect. Except the treatment with tannin, the hypothesis was successfully tested. The results from this study should be useful to better understand the turnover processes of soil carbon pools with exogenous carbon inputs. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the temperature sensitivity of labile and relatively recalcitrant forest soil carbon (C) pools amended with biochar during short-term incubation. Biochars were prepared using sugar cane residue under pyrolysis temperatures of 300 and 700 °C (i.e., BC300 and BC700), respectively. Coarse particulate organic matter and acid hydrolysis residue were separated from a forest soil and treated as the labile and recalcitrant C pools of the soil, respectively. Temperature sensitivity of the soil C pools was characterized using the Q10 values (i.e., the proportional increase in respiration per 10 °C rise). The increased Q10 values of treatments in the earlier stage were attributable to instantaneously increased aromatic C content. The following decreased Q10 values were related to the consumption of labile C. However, the two types of biochars led to similar Q10 values in the same C pools at the later stage of incubation, which was closely related to the nearly humic-like component content in the dissolved organic matter. The different temporal distributions of Q10 values were attributable to changes of aromatic C content and continuous consumption of labile components. [ABSTRACT FROM AUTHOR]

Purpose: The soil is the largest carbon pool in the terrestrial ecosystem. Changes of soil respiration with the climate warming are essential for the carbon cycling between the terrestrial ecosystem and the atmosphere. The aim of this study was to investigate the temperature adaptability of soil respiration and the possible mechanisms.Materials and methods: Experiments with a meadow soil were conducted through pre-incubation for 3 days at 22 °C, then incubation under temperatures of 22 ± 1, 30 ± 1, and 38 ± 1 °C, respectively, for 35 days. For the different incubation temperatures, gas samples were collected on days 3, 9, 13, 16, 20, 23, 30, and 35, respectively. The gas samples were used for measurements of CO2 concentrations and calculation of soil respiration rates. The temperature sensibility of soil respiration was characterized with the index Q10 (i.e., the increasing multiple of respiration rate with temperature increase of 10 °C). Soil properties related to respiration rates were measured, including total carbon (TC), dissolved organic carbon (DOC), soil organic matter (SOM), microbial biomass carbon (MBC), enzyme activities, and microbial community structure.Results and discussion: After 35 days of incubation, the temperature sensibility of soil respiration decreased with the incubation temperatures, i.e., Q10 (22 °C) > Q10 (30 °C) > Q10 (38 °C). The result showed that soil respiration exhibited temperature adaptability. The TC and SOM contents were not significantly different among the different temperatures, indicating sufficient substrate availability during the short incubation period. The warming scenarios led to lower activities of enzymes relative to C and N cycles and MBC and significantly changed the microbial community, especially decreased abundance of gram-negative bacteria. The elevated temperatures also reduced the comparability of bacteria and fungi and increased the diversity of microbial community structure.Conclusions: Mechanisms of the temperature adaptability of soil respiration included reduction of the carbon-use efficiency and temperature adaptation of microorganisms. Among them, the microbial adaptation was the dominant mechanism for the temperature adaptability of soil respiration during the short-term incubation experiments. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the influence of chemical leaching on permeability and Cd removal from fine-grained polluted soils. Column leaching experiments were conducted using two types of soils (i.e., artificially Cd-polluted loam and historically polluted silty loam). Chemical agents of CaCl, FeCl, citric acid, EDTA, rhamnolipid, and deionized water were used to leach Cd from the soils. Results showed that organic agents reduced permeability of both soils, and FeCl reduced permeability of loam soil, compared with inorganic agents and deionized water. Entrapment and deposition of colloids generated from the organic agents and FeCl treatments reduced the soil permeability. The peak Cd effluence from the artificially polluted loam columns was retarded. For the artificially polluted soils treated with EDTA and the historically polluted soils with FeCl, Cd precipitates were observed at the bottom after chemical leaching. When Cd was associated with large colloid particles, the reduction of soil permeability caused Cd accumulation in deeper soil. In addition, the slow process of disintegration of soil clay during chemical leaching might result in the retardation of peak Cd effluence. These results suggest the need for caution when using chemical-leaching agents for Cd removal in fine-grained soils. [ABSTRACT FROM AUTHOR]

The aim of the present study is to investigate the effect of seed inoculation with endophytic denitrifiers on rice seedling growth and nitrogen use efficiency under low- and high-urea conditions. Pseudomonas sp. B2, Streptomyces sp. A9, and Fusarium sp. F3 were isolated from rice plant tissues. Rice seeds inoculated with the denitrifiers were sown in soil fertilized with 100 and 300 mg/kg urea concentrations, respectively. The denitrifiers increased soil ammonia concentrations or kept high ammonia concentration for a longer time in soils. However, soil nitrate concentrations with the denitrifier treatments were lower than that of the control. All the denitrifier treatments increased the chlorophyll content by more than 200% under the low urea condition. Compared to the control, the denitrifier inoculation treatments significantly increased shoot length, fresh weight, and dry weight of rice seedlings under the low- and high-urea conditions ( P < 0.05). The chlorophyll concentrations, shoot length, wet weight, and dry weight of all the denitrifier treatments under the low urea fertilization were significantly higher than those of the control under the high-urea fertilization ( P < 0.05). The nitrogen use efficiency of rice seedlings might be attributable to nitrate reductases of the denitrifiers, acting as the rice nitrate reductase. The treatment of endophytic denitrifiers significantly improved rice seedling growth and nitrogen use efficiency under both low- and high-urea conditions. [ABSTRACT FROM AUTHOR]

Metal-resistant endophytic fungi from roots improved phytoremediation efficacy of host plants; however, the effects of endophytic fungi from plant aerial parts on host plants are unknown. The aim of this study was to develop a feasible method to screen fungal endophytes from stems and roots of Brassica napus and to investigate effects of the endophytic fungi on growth and phytoremediation efficiency of the plant. Endophytic Fusarium sp. CBRF44, Penicillium sp. CBRF65, and Alternaria sp. CBSF68 with different traits were isolated from roots and stems of rapes grown in a metal-contaminated soil. Fusarium sp. CBRF44 (resistant to 5 mM Cd and 15 mM Pb, isolated from roots) and Alternaria sp. CBSF68 (resistant to 1 mM Cd and 10 mM Pb, isolated from stems) could produce indole-3-acetic acid (IAA) and siderophore; Penicillium sp. CBRF65 (tolerate 2 mM Cd and 20 mM Pb, isolated from roots) could not produce IAA and siderophore but showed the highest phosphate-solubilizing activities. Fusarium sp. CBRF44 and Penicillium sp. CBRF65 significantly increased the rape biomass and promoted the extraction efficacy of Pb and Cd, while Alternaria sp. CBSF68 did not show similar results. Penicillium sp. CBRF65 and Fusarium sp. CBRF44 could be frequently recovered from inoculated rape roots, while Alternaria sp. CBSF68 was scarcely recovered. The results indicate that the colonizing capacity of endophytic fungi in roots is important to improve phytoremediation efficacy of host plants. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of biochar addition on the denitrification process and NO emission in Cd-contaminated soil. Four different biochars, i.e., dairy manure and rice straw pyrolyzed at 350 and 550 °C, respectively, were added into a Cd-contaminated soil and incubation experiments were conducted for 8 weeks. Results showed that Cd had an inhibitory effect on denitrifying reductase enzymes and reduced the abundance of functional genes. On the contrary, amendment with the biochars increased denitrifying enzyme activity and gene abundance, and thus, enhanced the denitrification process. Labile carbon (C) in the biochar-amended soil, which was calculated based on the two-pool exponential model, was the key factor to facilitate this process. As a less important factor, elevated soil pH by biochar addition also increased denitrifying activity as well as the nosZ abundance. Decrease of Cd bioavailability by the biochar addition was beneficial to the denitrification process. Addition of the biochars with higher amount of NO -N, especially the rice straw-derived biochars, increased cumulative NO emission by more than ten times relative to the Cd-contaminated soil. With the great amount of labile C and NO -N, the treatment of biochars prepared at 350 °C released the larger amount of CO and NO than other treatments. The biochar addition could totally release the heavy metal stress and restore the Cd-contaminated soil in terms of bacterial community. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of single and mixed culture of denitrifying fungi, bacteria, and actinobacteria on nitrogen removal and NO emission in treatment of wastewater. Denitrifying endophytes of Pseudomonas sp. B2, Streptomyces sp. A9, and Fusarium sp. F3 isolated from rice plants were utilized for treatment of synthetic wastewater containing nitrate and nitrite. Experiments were conducted under shaking and static conditions. Results showed that under the static condition, more than 97 % of nitrate removal efficiencies were reached in all the treatments containing B2. The nitrate removal rates within the first 12 h in the treatments of B2, B2+A9, B2+F3, and B2+A9+F3 were 7.3, 9.8, 11, and 11 mg L h, respectively. Under the shaking condition, 100 % of nitrite was removed in all the treatments containing B2. The presence of A9 and F3 with B2 increased the nitrite removal rates under both the shaking and static conditions. Compared to the B2 system, the mixed systems of B2+A9, B2+F3, and B2+A9+F3 reduced NO emission (78.4 vs. 19.4, 1.80, and 0.03 μM in 4 weeks, respectively). Our results suggested that B2 is an important strain that enhances nitrogen removal from wastewater. Mixed cultures of B2 with A9 and F3 can remove more nitrate and nitrite from wastewater and reduce nitrite accumulation and NO emission in the denitrification process. [ABSTRACT FROM AUTHOR]

Microorganisms play a key role in removal of pollutants in constructed wetlands (CWs). The aim of this study was to investigate the composition and diversity of microbes in a full-scale integrated constructed wetland system and examine how microbial assemblages were shaped by the structures and physicochemical properties of the sediments. The microbial assemblages were determined using 16S rRNA high-throughput sequencing. Results showed that the microbial phenotypes were more diverse in the system than in single CWs. The genera of Zoogloea, Comamonas, Thiobacillus, Nitrosospira, Denitratisoma, Azonexus, and Azospira showed relatively high abundances, which contributed to the removal of organic matter and nitrogen. The interactions among the three CWs in series acted a key role in the increase of phylogenetic diversity and high percentage of shared operational taxonomic units. In the system, some core microbes always existed even with the changing environment. Redox potential and NH-N were the important factors affecting the overall microbial community patterns. Total organic carbon had a relatively high impact on some denitrifiers. The results from this study should be useful to better understand the microbial mechanism of wastewater treatment in integrated constructed wetland systems. [ABSTRACT FROM AUTHOR]

As the bioelectrochemical system, the microbial fuel cell (MFC) and the microbial electrolysis cell (MEC) were developed to selectively recover Cu and Ni ions from wastewater. The wastewater was treated in the cathode chambers of the system, in which Cu and Ni ions were removed by using the MFC and the MEC, respectively. At an initial Cu concentration of 500 mg ·L, removal efficiencies of Cu increased from 97.0%± 1.8% to 99.0%±0.3% with the initial Ni concentrations from 250 to 1000 mg·L, and maximum power densities increased from 3.1±0.5 to 5.4±0.6W·m. The Ni removal mass in the MEC increased from 6.8±0.2 to 20.5±1.5 mg with the increase of Ni concentrations. At an initial Ni concentration of 500 mg·L, Cu removal efficiencies decreased from 99.1%±0.3% to 74.2%±3.8% with the initial Cu concentrations from 250 to 1000 mg ·L, and maximum power densities increased from 3.0±0.1 to 6.3±1.2W·m. Subsequently, the Ni removal efficiencies decreased from 96.9%±3.1% to 73.3%±5.4%. The results clearly demonstrated the feasibility of selective recovery of Cu and Ni from the wastewater using the bioelectrochemical system. [ABSTRACT FROM AUTHOR]

Microbial desalination cell (MDC) is a promising technology to desalinate water and generate electrical power simultaneously. The objectives of this study were to investigate the desalination performance of monovalent and divalent cations in the MDC, and discuss the effect of ion characteristics, ion concentrations, and electrical characteristics. Mixed salt solutions of NaCl, MgCl, KCl, and CaCl with the same concentration were used in the desalination chamber to study removal of cations. Results showed that in the mixed salt solutions, the electrodialysis desalination rates of cations were: Ca >Mg>Na>K. Higher ionic charges and smaller hydrated ionic radii resulted in higher desalination rates of the cations, in which the ionic charge was more important than the hydrated ionic radius. Mixed solutions of NaCl and MgCl with different concentrations were used in the desalination chamber to study the effect of ion concentrations. Results showed that when ion concentrations of Na were one-fifth to five times of Mg, ion concentration influenced the dialysis more profoundly than electrodialysis. With the current densities below a certain value, charge transfer efficiencies became very low and the dialysis was the main process responsible for the desalination. And the phosphate transfer from the anode chamber and potassium transfer from the cathode chamber could balance 1%-3% of the charge transfer in the MDC. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the potential to remove chromium (Cr) from aqueous solutions using the fruiting body of Auricularia polytricha. Batch experiments were conducted under various conditions, and different models were used to characterize the biosorption process. Results showed that, for both fresh and dried fruiting bodies of A. polytricha, removal efficiencies of Cr(VI) and total Cr reached maximum values at pH values of 1 and 2, respectively. The process of Cr(VI) removal by A. polytricha included the sorption process as well as the reduction of Cr(VI) to Cr(III). Spectra of X-ray photoelectron spectroscopy of the biosorbent revealed that most of the Cr loaded on the biomass surface was in the trivalent form. The Freundlich model fitted the isotherm process better than the Langmuir model in the concentration range examined. The pseudo-second-order model well described the adsorption process of Cr onto the biomass. The biosorption capacity of Cr(VI) by fruiting bodies was much higher than that by most of other biosorbents reported. The results suggest that the fruiting bodies of A. polytricha should be a promising biomaterial for Cr removal from water contaminated by the heavy metal. [ABSTRACT FROM AUTHOR]

To take full advantage of biochar as a soil amendment, the objective of this study was to investigate the effects of biochar addition on soil bacterial and fungal diversity and community composition. Incubation experiments with a forest soil (a red oxidized loam soil) with and without biochar amendment were conducted for 96 days. The culture-independent molecular method was utilized to analyze soil bacterial and fungal species after the incubation experiments. Results showed that bacteria and fungi responded differently to the biochar addition during the short-term soil incubation. Twenty four and 18 bacterial genara were observed in the biochar amended and unamended soils, respectively, whereas 11 and 8 fungal genera were observed in the biochar amended and unamended soils, respectively. Microbial taxa analysis indicated that the biochar amendment resulted in significant shifts in both bacterial and fungal taxa during the incubation period. The shift for bacteria occurred at the genus and phylum levels, while for fungi only at the genus level. Specific taxa, such as Actinobacteria of bacteria and Trichoderma and Paecilomyces of fungi, were enriched in the biochar amended soil. The results reveal a pronounced impact of biochar on soil microbial community composition and an enrichment of key bacterial and fungal taxa in the soil during the short time period. [ABSTRACT FROM AUTHOR]

Purpose: Carbon (C) flux is largely controlled by the highly bio-reactive labile C (LC) pool, while long-term C storage is determined by the recalcitrant C (RC) pool. Soil nitrogen (N) availability may considerably affect changes of these pools. The aim of this study was to investigate the effects of N treatments on soil LC and RC pools. Materials and methods: A field experiment was conducted in a city lawn soil for 600 days with three N treatments, i.e., the control (0 kg N ha year), low-N (100 kg N ha year), and high-N (200 kg N ha year) treatments. As the N source, NHNO solution was added to soil surface monthly. Measurements of LC, RC, and other soil biochemical properties, including pH, soil respiration rates, microbial biomass, and enzymes activities, were taken during the experiment period. Results and discussion: The low-N and high-N treatments increased 6.3 and 13% of the LC pool, respectively, which was caused by decreased microbial biomass and soil respiration rates under the N treatments. By contrary, the low-N and high-N treatments decreased 5.9 and 12% of the RC pool, respectively. The N addition treatments enhanced phenol oxidase activities. The enhanced oxidase activities decreased new RC input and the increased dissolved organic C stimulated RC pool decomposition. The LC and RC pools were highly influenced by the N treatments, whereas effect of the N treatments on soil organic C was not significant. The N addition treatments also caused soil acidification and reduced bacterial biomass proportion in the soil microbial composition. Conclusions: The N addition increased the LC pool but decreased the RC pool in the soil. These changes should greatly impact soil long-term C storage. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the features of a Cd-, Pb-, and Zn-resistant endophytic fungus Lasiodiplodia sp. MXSF31 and to investigate the potential of MXSF31 to remove metals from contaminated water and soils. The endophytic fungus was isolated from the stem of Portulaca oleracea growing in metal-contaminated soils. The maximum biosorption capacities of MXSF31 were 3.0 × 10, 1.1 × 10, and 1.3 × 10 mg kg for Cd, Pb, and Zn, respectively. The biosorption processes of Cd, Pb, and Zn by MXSF31 were well characterized with the pseudo-second-order kinetic model. The biosorption isotherm processes of Pb and Zn by the fungus were fitted better with the Langmuir model, while the biosorption processes of Cd was better fitted with the Freundlich model. The biosorption process of MXSF31 was attributed to the functional groups of hydroxyl, amino, carbonyl, and benzene ring on the cell wall. The active biomass of the strain removed more Cd, Pb, and Zn (4.6 × 10, 5.6 × 10, and 7.0 × 10 mg kg, respectively) than the dead biomass. The inoculation of MXSF31 increased the biomass of rape ( Brassica napus L.), the translocation factor of Cd, and the extraction amount of Cd by rape in the Cd + Pb-contaminated soils. The results indicated that the endophytic fungus strain had the potential to remove heavy metals from water and soils contaminated by multiple heavy metals, and plants accumulating multiple metals might harbor diverse fungi suitable for bioremediation of contaminated media. [ABSTRACT FROM AUTHOR]

Separator between anode and cathode is an essential part of the microbial fuel cell (MFC) and its property could significantly influence the system performance. In this study we used polyvinyl alcohol (PVA) polymer membrane crosslinked with sulfosuccinic acid (SSA) as a new separator for the MFC. The highest power density of 759±4mW·m was obtained when MFC using the PVA membrane crosslinked with 15% of SSA due to its desirable proton conductivity (5.16±10 S·cm). The power density significantly increased to 1106±30 mW·m with a separator-electrode-assembly configuration, which was comparable with glass fiber (1170±46 mW·m). The coulombic efficiencies of the MFCs with crosslinked PVA membranes ranged from 36.3% to 45.7% at a fix external resistance of 1000 Ω. The crosslinked PVA membrane could be a promising alternative to separator materials for constructing practical MFC system. [ABSTRACT FROM AUTHOR]

Free-floating aquatic plants Pistia stratiotes and Eichhornia crassipes are well-known invasive species in the tropics and subtropics. The aim of this study was to utilize the plants as cost-effective and environmentally friendly oil sorbents. Multilevel wrinkle structure of P. stratiotes leaf (PL), rough surface of E. crassipes leaf (EL), and box structure of E. crassipes stalk (ES) were observed using the scanning electron microscope. The natural hydrophobic structures and capillary rise tests supported the idea to use P. stratiotes and E. crassipes as oil sorbents. Experiments indicated that the oil sorption by the plants was a fast process. The maximum sorption capacities for different oils reached 5.1-7.6, 3.1-4.8, and 10.6-11.7 g of oil per gram of sorbent for PL, EL, and ES, respectively. In the range of 5-35 °C, the sorption capacities of the plants were not significantly different. These results suggest that the plants can be used as efficient oil sorbents. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the benthic bacterial communities in different depths of an urban river sediment accumulated with high concentrations of nutrients and metals. Vertical distributions of bacterial operational taxonomic units (OTUs) and chemical parameters (nutrients: NH 4+, NO 3−, dissolved organic carbon, and acid volatile sulfur; metals: Fe, Zn, and Cu) were characterized in 30 cm sediment cores. The bacterial OTUs were measured using the terminal restriction fragment length polymorphism analysis. Biodiversity indexes and multivariate statistical analyses were used to characterize the spatial distributions of microbial diversity in response to the environmental parameters. Results showed that concentrations of the nutrients and metals in this river sediment were higher than those in similar studies. Furthermore, high microbial richness and diversity appeared in the sediment. The diversity did not vary obviously in the whole sediment profile. The change of the diversity indexes and the affiliations of the OTUs showed that the top layer had different bacterial community structure from deeper layers due to the hydrological disturbance and redox change in the surface sediment. The dominant bacterial OTUs ubiquitously existed in the deeper sediment layers (5–27 cm) corresponding to the distributions of the nutrients and metals. With much higher diversity than the dominant OTUs, the minor bacterial assemblages varied with depths, which might be affected by the sedimentation process and the environmental competition pressure. [ABSTRACT FROM AUTHOR]

Purpose: Biochar addition to soils potentially affects various soil properties, and these effects are dependent on biochars derived from different feedstock materials and pyrolysis processes. The objective of this study was to investigate the effects of amendment of different biochars on soil physical and hydraulic properties. Materials and methods: Biochars were produced with dairy manure and woodchip at temperatures of 300, 500, and 700 °C, respectively. Each biochar was mixed at 5 % ( w/w) with a forest soil, and the mixture was incubated for 180 days, during which soil physical and hydraulic properties were measured. Results and discussion: Results showed that the biochar addition significantly enhanced the formation of soil macroaggregates at the early incubation time. The biochar application significantly reduced soil bulk density, increased the amount of soil organic matter, and stimulated microbial activity at the early incubation stage. Saturated hydraulic conductivities of the soil with biochars, especially produced at high pyrolysis temperature, were higher than those without biochars on the sampling days. The treatments with woodchip biochars resulted in higher saturated hydraulic conductivities than the dairy manure biochar treatments. Biochar applications improved water retention capacity, with stronger effects by biochars produced at higher pyrolysis temperatures. At the same suction, the soil with woodchip biochars possessed higher water content than that with the dairy manure biochars. Conclusions: Biochar addition significantly affected the soil physical and hydraulic properties. The effects were different with biochars derived from different feedstock materials and pyrolysis temperatures. [ABSTRACT FROM AUTHOR]

In this study, DOW CORNING 1-2577 Conformal Coating was proposed for the cathode diffusion layer of the microbial fuel cell (MFC). In MFCs, stainless steel mesh cathodes using DOW CORNING 1-2577 Conformal Coating/carbon as the diffusion layer and two poly (dimethylsiloxane) (PDMS)/carbon diffusion layers and carbon cloth cathode with four poly (tetrafluoroethylene) (PTFE) diffusion layers were constructed for comparison. Under the same operational condition, the MFCs with the DOW CORNING 1-2577 Conformal Coating/carbon diffusion layer produced the maximum power density of 1585±52 mW·m, compared with those using poly (tetrafluoroethylene) (PTFE) diffusion layers (1421±45 mW·m) and poly (dimethylsiloxane) (PDMS)/carbon diffusion layers (1353±49 mW·m). The DOW CORNING 1-2577 Conformal Coating could be an alternative for the diffusion layer construction in the MFC due to its remarkable performance and much simple construction procedure. [ABSTRACT FROM AUTHOR]

Purpose: The source and diagenesis of sediment organic matter (OM) based on amino sugar yields and compositions were investigated in sediment samples collected along a reach of the upper Pearl River Estuary in south China. Materials and methods: Sediment samples were collected from the estuary. Three sediment size fractions-coarse particulate OM (CPOM), fine particulate OM (FPOM), and ultrafiltered dissolved OM (UDOM)-were analyzed for total hydrolysable amino sugars (THAS), total organic carbon (TOC), and total nitrogen (N). Results and discussion: THAS contributed much more to sediment TOC and total N in UDOM than in CPOM and FPOM. Percentages of TOC as THAS increased with increasing sediment size. The low glucosamine/galactosamine ratios indicated a relatively large bacterial contribution to the sediment OM size fractions and the less reactive nature of sediment OM in the upper Pearl River Estuary. However, the depletion in muramic acid in the three sediment fractions, especially in UDOM, suggested that living bacteria or intact peptidoglycan units were not a major contributor to sediment OM. Conclusions: The increases of TOC as THAS and C-normalized yields of THAS with the different sediment size fractions demonstrated that they could be used as diagenetic indicators. [ABSTRACT FROM AUTHOR]

As a polycyclic aromatic hydrocarbon (PAH), pyrene is one of hazardous persistent organic pollutants in the aquatic environment. The aim of this study was to investigate the influence of denitrifying conditions on pyrene degradation in a pure culture. With a strain isolated from petrol-contaminated river sediment, treatments of pyrene biodegradations were set up using various ratios of nitrate to nitrite (NO/NO). Results showed that various NO/NO conditions significantly influenced the anaerobic pyrene degradation efficiency. Nitrite could induce the complete denitrification process so that NO acted as a key factor to promote high degradation efficiency. The low N treatment of NO and NO concentrations made the denitrifying-pyrene-degradation process more effective. Additionally, high C/N value stimulated high degradation rates. High concentrations of NO and NO as well as toxic intermediate product accumulation might inhibit the bacterial growth and biodegradation process. The information from this study should be useful to design bioremediation strategies of PAH. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of biochar application on soil methane (CH) emission. Experiments were conducted over an 84-day incubation period with the following treatments: each of two soils (a paddy soil and a forest soil) was treated with or without biochar at three soil moisture levels (35, 60, and 100 % water-filled pore space (WFPS) for the paddy soil; 35, 60, and 85 % WFPS for the forest soil). Biochar application ( P < 0.05) significantly increased soil pH and stimulated C mineralization at the early incubation stage. The effects of biochar application on CH emission were related to the soil moistures, with reduction of CH emission at 35 and 60 % WFPS and stimulation at the highest soil moisture. While both soils changed from CH sinks to sources by increasing soil moisture regardless of biochar addition, the effect was enhanced with biochar application. At lower soil moistures, the CH oxidation activity in soils was higher with biochar than without biochar, while the trend became opposite at higher soil moistures. Therefore, the CH production and consumption processes were influenced by different soil moisture levels and microbial communities of different soils. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the biosorption characteristics of Cd, Cu, and Pb by the fruiting body of jelly fungus Auricularia polytricha. Batch experiments were conducted to characterize the kinetics, equilibrium, and mechanisms of the biosorption process. Optimum values of pH 5, biomass dosage 4 g L, and contact time 60 min provided maximum biosorption capacities of A. polytricha for Cd, Cu, and Pb of 63.3, 73.7, and 221 mg g, respectively. The maximum desorption was achieved using 0.05 mol L HNO as an elute. The fruiting body was reusable at least for six cycles of operations. The pseudo-second-order model was the best to describe the biosorption processes among the three kinetic models tested. Freundlich and Dubinin-Radushkevich models fitted the equilibrium data well, indicating a heterogeneous biosorbent surface and the favorable chemisorption nature of the biosorption process. A Fourier transform infrared spectroscopy analysis indicated that carboxyl, amine/hydroxyl, amino, phosphoryl, and C-N-C were the main functional groups to affect the biosorption process. Synergistic ion exchange and surface complexation were the dominant mechanisms in the biosorption process. The present work revealed the potential of jelly fungus (fruiting body of A. polytricha) to remove toxic heavy metals from contaminated water. [ABSTRACT FROM AUTHOR]

Purpose: Nitrate (NO) is often considered to be removed mainly through microbial respiratory denitrification coupled with carbon oxidation. Alternatively, NO may be reduced by chemolithoautotrophic bacteria using sulfide as an electron donor. The aim of this study was to quantify the NO reduction process with sulfide oxidation under different NO input concentrations in river sediment. Materials and methods: Under NO input concentrations of 0.2 to 30 mM, flow-through reactors filled with river sediment from the Pearl River, China, were used to measure the processes of potential NO reduction and sulfate (SO) production. Molecular biology analyses were conducted to study the microbial mechanisms involved. Results and discussion: Simultaneous NO removal and SO production were observed with the different NO concentrations in the sediment samples collected at different depths. Potentially, NO removal reached 72 to 91 % and SO production rates ranged from 0.196 to 0.903 mM h. The potential NO removal rates were linearly correlated to the NO input concentrations. While the SO production process became stable, the NO reduction process was still a first-order reaction within the range of NO input concentrations. With low NO input concentrations, the NO removal was mainly through the pathway of dissimilatory NO reduction to NH, while with higher NO concentrations the NO removal was through the denitrification pathway. Conclusions: While most of NO in the sediment was reduced by denitrifying heterotrophs, sulfide-driven NO reduction accounted for up to 26 % of the total NO removal under lower NO concentrations. The vertical distributions of NO reduction and SO production processes were different because of the variable bacterial communities with depth. [ABSTRACT FROM AUTHOR]

Climate change, such as warming and precipitation change, as well as elevated CO can affect soil organic carbon (SOC) dynamics and cause changes in soil carbon sequestration. In this study, we introduced a response equation, relating the relative change of SOC to the relative changes of annual average temperature, annual precipitation, and atmospheric CO concentration, as well as their inter-products. Using Nelson Farm as a case study, based on simulations of CENTURY model and multiple regressions, we examined the response equation for three vegetation covers (i.e., soybean, corn, and grass) and scenarios with different soil erosion rates and initial SOC contents. The response equation fit the simulation results very well with high adjusted coefficients of determination ( R) (0.982 to 0.990). The results showed that the SOC was negatively related to the annual average temperature, positively related to the annual precipitation, and positively related to the elevated CO for all the vegetation covers ( p < 0.001). The SOC was also significantly impacted by the interaction effects between elevated CO and warming or precipitation change ( p < 0.001). The general form of the response equations for the different vegetation covers, soil erosion rates, and initial SOC contents was the same although the parameters varied with the different conditions. Based on the response equation, 'cutoff surfaces' were defined to clearly quantify the synthesis effects of any possible combination of climate change and elevated CO on the SOC, and the SOC sequestration potential was assessed under climate change and elevated CO for different vegetations. Compared with the empirical models in the literature, this response equation provides a simple yet but robust method to represent the relationship between the SOC relative change vs. the relative changes of atmospheric temperature, precipitation, and atmospheric CO concentration. [ABSTRACT FROM AUTHOR]

Bacteria, actinomycetes, and fungi are the dominant components of the soil microflora, and some of their species can perform denitrification. The aim of this study was to investigate the interactions of three kinds of denitrifiers in mix-culturing systems. Three denitrifying strains, i.e., one bacterial strain (strain B5), one actinomycete strain (strain A2), and one fungal strain (strain F1), were isolated from a rice paddy soil. Denitrifier interactions were examined by analyzing the population dynamics and metabolic substance in the mix-culturing systems with two and three strains and by estimating the effects of cell-free culture filtrates on the strains. Results showed that the growth of B5 was enhanced by F1 and A2, respectively, and nitrate removal proportions in the culture systems increased from 52% (B5) to 64% (B5 + F1) and 67% (B5 + A2), and the nitrate removal was further enhanced in the three strain mix-culturing system (74%, A2 + F1 + B5). Strain B5 stimulated the cell growth of A2 directly and indirectly. The existence of A2 was lethal for cell growth of F1, while A2 was also suppressed by F1. The suppressive interaction reduced nitrate removal rates from the single systems of 12.8 (F1) and 11.5 mg L day (A2) to 8.75 mg L day (A2 + F1). Likewise, F1 was inhibited by B5. The results also showed that the cell-free culture filtrates of other strains suppressed the cell growth of B5 and F1, respectively, but enhanced the cell growth of A2. In addition to the direct effect of cell-free culture filtrates, other indirect relationships could affect the denitrifier spatial distributions and balance of the suppression or promotion effects, which were beneficial to maintain the microbial structure and function stability with a low nitrous oxide emission in the soil. [ABSTRACT FROM AUTHOR]

The active region model (ARM) has been developed as a practical and effective approach for characterizing and representing preferential flow patterns in unsaturated soils. However, studies on methods to determine the ARM parameter ( γ) are very limited. The major objective of this work was to refine the methods for determining the ARM parameter ( γ) using the data from field-scale dye staining experiments. For this purpose, 13 field-scale dye staining experiments were conducted in silty clay, loam and sand with various initial and boundary conditions. The distributions of soil water content and fraction of stained region were measured to determine the ARM parameter ( γ). Three determination methods of ARM parameter ( γ) were presented according to the different distribution patterns of the soil water content of stained region. The efficiency of these approaches was demonstrated with the results from 13 field-scale dye staining tests that were directly related to preferential flow patterns. Impacts of soil texture on soil water redistribution, and effects of initial soil water content and infiltration amount on the preferential flow heterogeneity were also discussed in this research. [ABSTRACT FROM AUTHOR]

To better understand the bacterial processes in river sediments, it is necessary to investigate the depth-related bacterial communities in the whole sediment profile. Sediment samples were collected to a depth of 25 cm from the Pearl River. Bacterial abundance, activity, cell-specific respiration rate, and diversity were measured, respectively, by 4′, 6-diamidino-2-phenylindole direct count, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) staining, electron transport system by CTC reduction, and denaturing gradient gel electrophoresis analysis of 16S rRNA amplification fragments. Results showed that the bacterial metabolism activities decreased with the sediment depth. The total bacterial abundance was highest in the surface sediment with 65.1 × 10 cells g, and decreased to 11.1 × 10 cells g below 20 cm in the sample location that suffered from heavy sewage inputs. The active bacteria accounted for 7.50-46.7% of the total bacterial number and decreased with the sediment depth. Electron transport system by the CTC reduction showed that bacterial respiration rate declined from 1.093 μmol CTC-formazan h g in the surface sediment to a half in the bottom sediment, while the cell-specific respiration increased significantly with the depth from 3.56 to 93.75 fmol CTC-formazan cell. The bacterial diversity also changed with the depth. Beta-Proteobacteria were the dominant species in the surface sediment, whereas Delta-Proteobacteria were the main species below 10 cm. Results of canonical correspondence analysis (CCA) indicated that the distribution of bacteria was affected by the combined effect of various dissolved inorganic matter, while the respiration rate was independent of the nutrient conditions. The specific bacterial distribution contributed to not only the nutrient cycle but also enhanced pollutant decomposition in sediment of the Pearl River. The results showed that some specific bacterial species had a strong activity in the deeper layers. Therefore, the metabolic functions of the deeper bacterial species should not be neglected. [ABSTRACT FROM AUTHOR]

Soil and crop management including crop rotation influences available organic carbon and soil nitrate levels, which may in turn affect denitrification losses from soils. The objective of this paper was to determine how the current and previous crop affect denitrification by comparing the basal denitrification rate (BDR), denitrification rate with added nitrate (DAN), and potential denitrification rate (PDR) (amended with glucose and nitrate) of a clay loam soil under monoculture corn (C), soybean (S), and winter wheat (WW) with or without underseeded red clover (RC) and under each phase of a 2-year crop rotation (C-S) and two 3-year crop rotations (C-S-WW, C-S-WW+RC). The BDRs were greater in the 3-year C-S-WW rotation treatments than in the 2-year C-S rotation and monoculture C, S, and WW treatments. The WW+RC phase of the C-S-WW+RC treatment was found to have a greater BDR and DAN than the corn phase of the rotation. Available organic carbon was found to limit denitrification in the BDR and DAN incubations as evidenced by the 2- to 21-fold increase in denitrification when glucose was added in the PDR assay. Further, the significant relationship between soil respiration and BDR suggests that available carbon was a limiting factor. This study found that both the current crop and previous crops in a rotation affected soil denitrification rates substantially; and that denitrification rate was increased when a mixture of crop residues were added to soil (i.e., from growing crops in rotation) relative to when only a single residue was added (i.e., monoculture cropping). [ABSTRACT FROM AUTHOR]

Preferential flow commonly observed in unsaturated soils allows rapid movement of solute from the ground surface or vadose zone to the groundwater, bypassing a significant volume of unsaturated soil and increasing the risk of groundwater contamination. A variety of evidence indicates that complex preferential flow patterns observed from fields are fractals. This paper discusses a macroscopic relationship for modeling preferential flow in the vadose zone. Conceptually, the flow domain can be divided into active and inactive regions. Flow occurs preferentially in the active region (characterized by fractals), and inactive region is simply bypassed. The portion of the active region was found to be a power function of saturation. The validity of this macroscopic relationship is demonstrated by its consistency with field observations and the related numerical experiments. [ABSTRACT FROM AUTHOR]

To better understand the adsorption and transport of Cd2+ in soils, column experiments were conducted with various soils and inflow solutions with different pH values. Breakthrough curves (BTCs) of the column tests were fitted using both the equilibrium and non-equilibrium models installed in the program of CXTFIT. Results showed that the equilibrium model fitted most of BTCs reasonably well. Values of the retardation factor ( R) and the distribution coefficient ( k d) for Cd2+ adsorption and transport increased with increasing pH values of the inflow solution and of the soil. However, the clay content was not a key factor to affect R and k d for Cd2+ adsorption and transport. The average dispersivity values and the variance values of dispersivity increased with increasing clay content of the soils. [ABSTRACT FROM AUTHOR]

Irrigation practices greatly affect sustainable agriculture development. In this study, we investigated the effects of irrigation efficiency on water flow and chemical transport in soils, which had significant impact on the environment. Field dye staining experiments were conducted at different soils with various irrigation amount. Image analysis was conducted to study the heterogeneous flow patterns and their relationships with the irrigation efficiency. Irrigation efficiency and its environmental effects were evaluated using various indictors, including application efficiency, deep percolation ratio, storage efficiency, and uniformity. Under the same irrigation condition, soil chemical distributions were more heterogeneous than soil water distributions. The distributions were mainly affected by soil texture, initial soil water content, and irrigation amount. Storage efficiency, irrigation uniformity, and deep percolation ratio increased with irrigation amount. Since the chemical distribution uniformity was lower than the water uniformity, the amount of chemical leaching increased sharply with decrease of irrigation uniformity, which resulted in high environmental risks of groundwater pollution. [ABSTRACT FROM AUTHOR]

As the critical information to study flow transport in soil–plant systems, root distributions and root-water-uptake (RWU) patterns have been studied extensively. However, most root distribution data in the past were collected under surface irrigation. Less research has been conducted to characterize root distributions under sub-irrigation. The objectives of this study were to (1) test if the generalized function of normalized root length density (NRLD) in the literature was applicable to root distributions of winter wheat under natural sub-irrigation, which provides water from subsurface by capillary rise from the water table, and (2) estimate RWU distributions of winter wheat under natural sub-irrigation. Column experiments were conducted to study the distributions of root length density (RLD) and RWU of winter wheat ( Triticum aestivum L. cv. Nongda 189) during a growing period of 57 days from planting to tillering stages under surface irrigation and natural sub-irrigation. Data of root distributions and soil water content were collected in the experiments with different treatments of irrigation levels. Results showed that the RLD distributions of winter wheat under both surface irrigation and natural sub-irrigation were of similar patterns. The NRLD distributions under sub-irrigation were adequately characterized by the generalized function. An inverse method was employed to estimate the average RWU rate distributions of winter wheat. In addition, based on the potential RWU coefficient and the NRLD function, a simple approach was developed to predict RWU rates at different depths. The predicted RWU rates had a good agreement with the estimated RWU rate distributions using the inverse method. [ABSTRACT FROM AUTHOR]

Estimating spatial variability of soil salinity is an important issue in precision agriculture. Geostatistical methods provide a means to study the heterogeneous nature of spatial distributions of soil salinity. In this study, geostatistical methods, kriging and cokriging, were applied to estimate sodium adsorption ratio (SAR) in a 3375 ha agricultural field. In cokriging, more easily measured data of electrical conductivity (EC) were incorporated to improve the estimation of SAR. The estimated spatial distributions of SAR using the geostatistical methods with various reduced data sets were compared with the extensive salinity measurements in the large field. The results suggest that sampling cost can be dramatically reduced and estimation can be significantly improved using cokriging. Compared with the kriging results using total SAR data, cokriging with reduced data sets of SAR improves the estimations greatly by reducing mean squared error and kriging variance up to 70% and increasing correlation of estimates and measurements about 60%. The sampling costs for SAR estimation can be reduced approximately by 80% using extensive EC data together with a small portion of SAR data in cokriging. [ABSTRACT FROM AUTHOR]

The combination of the microbial electrolysis desalination and chemical-production cell (MEDCC) and Fenton process for the pesticide wastewater treatment was investigate in this study. Real wastewater with several toxic pesticides, 1633 mg/L COD, and 200 in chromaticity was used for the investigation. Results showed that desalination in the desalination chamber of MEDCC reached 78%. Organics with low molecular weights in the desalination chamber could be removed from the desalination chamber, resulting in 28% and 23% of the total COD in the acid-production and cathode chambers, respectively. The desalination in the desalination chamber and organic transfer contributed to removal of pesticides (e.g., triadimefon), which could not be removed with other methods, and of the organics with low molecular weights. The COD in the effluent of the MEDCC combined the Fenton process was much lower than that in the perixo-coagulaiton process (< 150 vs. 555 mg/L). The combined method consumed much less energy and acid for the pH adjustment than that the Fenton. [ABSTRACT FROM AUTHOR]

The aim of this study was to synthesize a novel lanthanum (La) doped catalyst and to investigate antipyrine removal in wastewater using the Fenton-like process with the catalyst. The La-doped Co-Cu-Fe catalyst was synthesized using the modified hydrothermal method. Results showed that the La-doped catalyst had higher specific surface area and lower particle size than the catalyst without La doping (i.e., the control) (267 vs. 163 m2/g and 14 vs. 32 nm, respectively). Under the conditions of catalyst dosage 0.5 g/L, H2O2 concentration 1.70 g/L, and NaHCO3 0.1 g/L, the antipyrine removal within 60 min using the Fenton-like process with the La-doped catalyst was much higher than that with the control (95% vs. 54%). The hydroxyl radical concentration with the La-doped catalyst within 60 min was two times higher than that with the control (49.2 vs. 22.1 µg/L). The high catalytic activity of La-doped catalyst was mainly attributed to its high specific surface area based on the X-ray photoelectron spectroscopy result. Our La-doped catalyst should have great potential to remove antipyrine in wastewater using the heterogeneous Fenton-like process. [ABSTRACT FROM AUTHOR]