A Comparative Study on Removal Efficiency of Cr(VI) in Aqueous Solution by <Emphasis Type="Italic">Fusarium</Emphasis> sp. and <Emphasis Type="Italic">Myrothecium</Emphasis> sp.

Environmental pollution with chromium is due to residues of several industrial processes. Bioremediation is an alternative actually considered to remove Cr (VI) from the environment, using adapted organisms that grow in contaminated places. Have been conducted studies with fungi mechanisms of interaction with chromium, most of which have focused on processes biosorption, characterized it by passive binding of metal components of the cell surface, and bioaccumulation, wherein the metal entry to cells occurs with energy expenditure. The paper presents the results of studies carried out on sorption of chromium (VI) ions from aqueous solutions by Fusarium sp. and Myrothecium sp. Both biomasses have the ability to take up hexavalent chromium during the stationary phase of growth and as well inactive conditions. Fusarium sp. showed 26% of biosorption with active biomass and 64% in inactive biomass; meanwhile, Myrothecium sp. obtained 97 and 82%, respectively. Both fungi showed adjust to pseudo-second-order model in active (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.96) and inactive biomass assay (Fusarium sp. R ² = 0.99; Myrothecium sp. R ² = 0.99). The data of the active biomass test also confirmed to the intraparticle diffusion model (Fusarium sp. R ² = 0.98; Myrothecium sp. R ² = 0.93). The results obtained through this investigation indicate the possibility of treating waste effluents containing hexavalent chromium using Fusarium sp. and Myrothecium sp.     

<Emphasis Type="Italic">Trichoderma</Emphasis> improves the growth of <Emphasis Type="Italic">Leymus chinensis</Emphasis>

Bio-fertilizer application has been proposed as a strategy for enhancing soil fertility, regulating soil microflora composition, and improving crop yields, and it has been widely applied in the agricultural yields. However, the application of bio-fertilizer in grassland has been poorly studied. We conducted in situ and pot experiments to investigate the practical effects of different fertilization regimes on Leymus chinensis growth, with a focus on the potential microecological mechanisms underlying the responses of soil microbial composition. L. chinensis biomass was significantly (P?<?0.05) increased by treatment with 6000 kg ha^?1 of Trichoderma bio-fertilizer compared with other treatments. We found a positive (R² =?0.6274, P <?0.001) correlation between bacterial alpha diversity and L. chinensis biomass. Hierarchical cluster analysis and nonmetric multidimensional scaling (NMDS) revealed that soil bacterial and fungal community compositions were all separated according to the fertilization regime used. The relative abundance of the most beneficial genera in bio-fertilizer (BOF) (6000 kg ha^?1Trichoderma bio-fertilizer) was significantly higher than in organic fertilizer (OF) (6000 kg ha^?1 organic fertilizer) or in CK (non-amend fertilizer), there the potential pathogenic genera were reduced. There were significant negative (P?<?0.05) correlations between L. chinensis biomass and the relative abundance of several potential pathogenic genera. However, the relative abundance of most beneficial genera were significantly (P?<?0.05) positively correlated with L. chinensis biomass. Soil properties had different effects on these beneficial and on these pathogenic genera, further influencing L. chinensis biomass.     

Dominant Characteristics Between <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> and <Emphasis Type="Italic">Cyclotella</Emphasis> Sp. Accompanying Dilution Process in Eutrophic Lake

Although dilution of lake water has been used for improvement of water quality and algal blooms control, it has not necessarily succeeded to suppress the blooms. We hypothesized that the disappearance of algal blooms by dilution could be explained by flow regime, nutrient concentrations, and their interaction. This study investigated the effects of daily renewal rate (d), nitrogen (N) and phosphorus (P) concentration, and their interaction on the domination between Microcystis aeruginosa and Cyclotella sp. through a monoxenic culture experiment. The simulation model as functions of the N:P mass ratio and dilution rate (D) (calculated from d) was constructed, and the dominant characteristics of both species were predicted based on the model using parameters obtained in a monoculture experiment and our previous study. Results of monoxenic culture experiment revealed that M. aeruginosa dominated in all conditions (d = 5 or 15%; N = 1.0 or 2.5 or 5.0 mg-N L^?1; P = 0.1 or 0.5 mg-P L^?1) and the predicted cell densities were substantially correspondent to experimental data. Under various N:P ratios and D values, characteristics of domination for each species were predicted, indicating that Cyclotella sp. tended to be dominant under high P concentrations (P ≥ 0.36 mg-P L^?1) when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1). It was also suggested that the dilution rate leading to the Cyclotella sp. domination required 0.20 day^?1 or higher regardless of the N:P ratios.

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Graphical Abstract ? M. aeruginosa and Cyclotella sp. could be a superior competitor in nutrient-limited and nutrient-rich conditions, respectively. ? The simulation model in this study indicated that the predicted cell density and nutrient concentration were substantially correspondent to experimental data. ? The model predicted that Cyclotella sp. tended to be dominant at the P ≥ 0.36 mg-P L^?1 when the N:P ratio was less than 7.0, and M. aeruginosa could not form algal blooms at the N:P ratio ≤ 7.0 (N ≤ 0.7 mg-N L^?1).

     

Interactive effects of biochar addition and elevated carbon dioxide concentration on soil carbon and nitrogen pools in mine spoil

Purpose

This study aimed to assess the effects of biochar on improving nitrogen (N) pools in mine spoil and examine the effects of elevated CO₂ on soil carbon (C) storage.

Materials and methods

The experiment consisted of three plant species (Austrostipa ramossissima, Dichelachne micrantha, and Lomandra longifolia) planted in the N-poor mine spoil with application of biochar produced at three temperatures (650, 750, and 850 °C) under both ambient (400 μL L^?1) and elevated (700 μL L^?1) CO₂. We assessed mine spoil total C and N concentrations and stable C and N isotope compositions (δ¹³C and δ¹⁵N), as well as hot water extractable organic C (HWEOC) and total N (HWETN) concentrations.

Results and discussion

Soil total N significantly increased following biochar application across all species. Elevated CO₂ induced soil C loss for A. ramossissima and D. micrantha without biochar application and D. micrantha with the application of biochar produced at 750 °C. In contrast, elevated CO₂ exhibited no significant effect on soil total C for A. littoralis, D. micrantha, or L. longifolia under any other biochar treatments.

Conclusions

Biochar application is a promising means to improve N retention and thus, reduce environmentally harmful N fluxes in mine spoil. However, elevated CO₂ exhibited no significant effects on increasing soil total C, which indicated that mine spoil has limited potential to store rising atmospheric CO₂.

     

Steam activation of biochars facilitates kinetics and pH-resilience of sulfamethazine sorption

Purpose

Sulfamethazine (SMT) is increasingly detected in environmental matrices due to its versatile use as antibiotics. We aimed to investigate the benefits and roles of steam activation of biochars with respect to SMT sorption kinetics and equilibrium sorption.

Materials and methods

Biochars were produced from burcucumber plant and tea waste using a pyrolyzer at a temperature of 700 °C for 2 h. The biochar samples were treated with 5 mL min^?1 of steam for an additional 45 min for post-synthesis steam activation. The SMT sorption on the unmodified and steam activated biochars were compared.

Results and discussion

The time taken to reach equilibrium was significantly less for steam activated biochars (～4 h) than non-activated biochars (>24 h). Up to 98 % of SMT could be removed from aqueous solutions by steam activated biochars. The sorption kinetic behaviors were well described by the pseudo-second model and SMT sorption rates of steam activated biochars (k ₂?～?1.11–1.57 mg g^?1 min^?1) were significantly higher than that of the unmodified biochars (k ₂?～?0.04–0.11 mg g^?1 min^?1) because of increased availability of accessible porous structure with averagely larger pore diameters. Moreover, the equilibrium sorption on the unmodified biochars was significantly influenced by increasing solution pH (～30–50 % reduction) because of speciation change of SMT, whereas steam activated biochars manifested much stronger sorption resilience against pH variation (～2–4 % reduction only) because the enhanced porosity offset the effect of unfavorable electrostatic repulsion.

Conclusions

The observed features of steam activated biochars would render their applications more versatile and reliable in field throughout changeable environmental conditions.

     

C-banded karyotype of <Emphasis Type="Italic">Thinopyrum bessarabicum</Emphasis> and identification of its chromosomes in wheat background

C-banded pattern in two accessions of Thinopyrum bessarabicum (Save ex Rayss) A. Löve (2n = 2x = 14, E^bE^b) and their idiogram was established. C-banding analysis was further used to identify the chromosomes of Tritipyrum amphiploid (2n = 6x = 42, AABBE^bE^b) and a BC₁F₂ genotype from wheat and Tritipyrum. Two 18S-26S rDNA loci were detected on Th. bessarabicum chromosomes by in situ hybridization using an 18S-26S rDNA probe. E^b chromosomes in Tritipyrum generally were identified by their distinctive C-banding patterns which reflected heterochromatin regions. C-banding procedure resulted in sharp and distinct bands in one or both ends of E^b chromosomes without interval bands. Observed C-bands in E^b genome mainly reflected the telomeric and subtelomeric sequences which also showed more strong signals in genomic in situ hybridization. Results showed the importance of the C-banding technique as a screening tool in identification of addition and substitution lines in the progenies of wheat and Tritipyrum crosses during segregating generations.     

Changes in methane emission and methanogenic and methanotrophic communities in restored wetland with introduction of <Emphasis Type="Italic">Alnus trabeculosa</Emphasis>

Purpose

The dynamics and uncertainties in wetland methane budgets affected by the introduction of Alnus trabeculosa H. necessitate research on production of methane by methanogenic archaea and consumption by methane-oxidizing microorganisms simultaneously.

Materials and methods

This study investigated methane emission in situ by the closed chamber method, and methanogenic and methanotrophic communities using denatured gradient gel electrophoresis (DGGE) and quantitative PCR based on mcrA (methyl coenzyme M reductase), pmoA (particulate methane monooxygenase) genes in the rhizosphere and non-rhizosphere soils in the indigenous pure Phragmites australis T., and A. trabeculosa–P. australis mixed communities in Chongxi wetland.

Results and discussion

Methane flux rate from the pure P. australis community was 2.4 times larger than that of A. trabeculosa–P. australis mixed community in the rhizosphere and 1.7 times larger in the non-rhizosphere, respectively. The abundance of methanogens was lower in the mixed community soils (3.56?×?10³–6.90?×?10³ copies g^?1 dry soil) compared with the P. australis community (1.47?×?10⁴–1.89?×?10⁴ copies g^?1 dry soil), whereas the methanotrophs showed an opposite trend (2.08?×?10⁶–1.39?×?10⁶ copies g^?1 dry soil for P. australis and 6.20?×?10⁶–1.99?×?10⁶ copies g^?1 dry soil for mixed community soil). A liner relationship between methane emission rates against pmoA/mcrA ratios (R ²?=?0.5818, p?<?0.05, n?=?15) was observed. The community structures of the methane-cycling microorganism based on mcrA and pmoA suggested that acetoclastic methanogens belonging to Methanosarcinaceae and a particular type II methanotroph, Methylocystis, were dominant in these two plant communities.

Conclusions

The introduction of A. trabeculosa would promote the proliferation of methanotrophs, especially the dominant Methylocystis, but not methanogens, ultimately diminishing methane emission in the wetland.

     

Effect of Cadmium Stress on Growth and Electrical Impedance Spectroscopy Parameters of <Emphasis Type="Italic">Cotinus coggygria</Emphasis> Roots

The use of plants for ecological remediation is an important method of controlling heavy metals in polluted land. Cotinus coggygria is a landscape plant that is used extensively in landscaping and afforestation. In this study, the cadmium tolerance level of C. coggygria was evaluated using electrical impedance spectroscopy (EIS) to lay a theoretical foundation for broad applications of this species in Cd-polluted areas and provide theoretical support to broaden the application range of the EIS technique. Two-year-old potted seedlings of C. coggygria were placed in a greenhouse to analyse the changes in the growth, water content and EIS parameters of the roots following treatment with different Cd concentrations (50, 100, 200, 500, 1000 and 1500 mg kg^?1), and soil without added Cd was used as the control. The roots grew well following Cd treatments of 50 and 100 mg kg^?1. The Cd contents increased with the increase in Cd concentration in the soil. However, the lowest root Cd content was found at 4 months of treatment. The extracellular resistance r_e and the intracellular resistance r_i increased first overall and then decreased with the increasing Cd concentration, and both parameters increased with a longer treatment duration. The water content had a significant negative correlation with the Cd content (P?<?0.01) and the r_e (P?<?0.05). C. coggygria could tolerate a soil Cd concentration of 100 mg kg^?1. There was a turning point in the growth, water content and EIS parameters of the C. coggygria roots when the soil Cd concentration reached 200 mg kg^?1. The root water content and r_e could reflect the level of Cd tolerance in C. coggygria.     

Taxon-specific responses of soil microbial communities to different soil priming effects induced by addition of plant residues and their biochars

Purpose

This work investigated changes in priming effects and the taxonomy of soil microbial communities after being amended with plant feedstock and its corresponding biochar.

Materials and methods

A soil incubation was conducted for 180 days to monitor the mineralization and evolution of soil-primed C after addition of maize and its biochar pyrolysed at 450 °C. Responses of individual microbial taxa were identified and compared using the next-generation sequencing method.

Results and discussion

Cumulative CO₂ showed similar trends but different magnitudes in soil supplied with feedstock and its biochar. Feedstock addition resulted in a positive priming effect of 1999 mg C kg^?1 soil (+253.7 %) while biochar gave negative primed C of ?872.1 mg C kg^?1 soil (?254.3 %). Linear relationships between mineralized material and mineralized soil C were detected. Most priming occurred in the first 15 days, indicating co-metabolism. Differences in priming may be explained by differences in properties of plant material, especially the water-extractable organic C. Predominant phyla were affiliated to Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Firmicutes, Planctomycetes, Proteobacteria, Verrucomicrobia, Ascomycota, Basidiomycota, Blastocladiomycota, Chytridiomycota, Zygomycota, Euryarchaeota, and Thaumarchaeota during decomposition. Cluster analysis resulted in separate phylogenetic grouping of feedstock and biochar. Bacteria (Acidobacteria, Firmicutes, Gemmatimonadetes, Planctomycetes), fungi (Ascomycota), and archaea (Euryarchaeota) were closely correlated to primed soil C (R ²?=??0.98, ?0.99, 0.84, 0.81, 0.91, and 0.91, respectively).

Conclusions

Quality of plant materials (especially labile C) shifted microbial community (specific microbial taxa) responses, resulting in a distinctive priming intensity, giving a better understanding of the functional role of soil microbial community as an important driver of priming effect.

     

Evaluation of different fractions of the organic matter of peat on tetracycline retention in environmental conditions: in vitro studies

Purpose

Due to the modernization of the agro-industrial sector, compounds with different toxicity and effects on human health and animal have been used and consequently affecting the environment. Among them, tetracycline (TC) stands out as one of the antibiotics most commonly used worldwide. This study evaluated the TC interaction with different fractions of peat in natura and humic substances, humic acid, fulvic acid, and humin.

Materials and methods

The different fractions of the organic matter were characterized by organic matter content, elemental analysis, spectroscopic analysis (E₄/E₆), and nuclear magnetic resonance of carbon 13 (NMR ¹³C), and the interaction between TC and different fractions of organic matter was made by fluorescence spectrometry. We used the tangential ultra-filtration system for determining the complexation capability of humic substances (HSs), fulvic acids (FA), humic acids (HA), and humin (HUM) from peat with TC. Finally, we evaluated sorption kinetic experiments between TC and peat in natura.

Results and discussion

The peat samples, humic substances, FAs, HAs, and HUM were characterized by organic matter (OM), atomic ratio (H/C and C/O) calculated from elemental analysis data, functional groups quantified by NMR ¹³C data, and E₄/E₆ ratio, and the results show significant differences in the structural characteristics of the fractions of OM influenced by the type of microorganisms and environmental factors associated with this decomposition. Data analysis revealed the strongest interaction between HUM and TC (59.19 mg g^?1), followed by interaction between HS and TC (43.36 mg g^?1 HS). In the sorption studies, these conditions showed the best model to describe the system under consideration using the Freundlich model.

Conclusions

The results showed that the different fractions of the OM extracted from peat show different contributions that affect the bioavailability of contaminants to the environment.

     

Evaluation of Mercury,Lead, Arsenic,and Cadmium in Some Species of Fish in the Atrato River Delta,Gulf of Urabá, Colombian Caribbean

The concentrations of mercury, lead, cadmium, and arsenic were evaluated in 96 samples, 12 by each one of the following eight fish species: snook (Centropomus undecimalis), crevalle jack (Caranx hippos), Serra Spanish mackerel (Scomberomorus brasiliensis), southern red snapper (Lutjanus purpureus), blue runner (Caranx crysos), Atlantic tarpon (Megalops atlanticus), ladyfish (Elops saurus), and Atlantic goliath grouper (Epinephelus itajara), which were collected during 1 year in the Atrato River Delta in the Gulf of Urabá, Colombian Caribbean. Three fish were caught from each of the following sites the community usually uses to catch them (known as fishing grounds): Bahía Candelaria, Bahía Marirrío, Bocas del Roto, and Bocas del Atrato. The quantification of metals was performed by microwave-induced plasma-optical emission spectrometry. The Pb concentration fluctuated from 0.672 to 3.110 mg kg^?1, surpassing the maximum permissible limit (MPL?=?0.3 mg kg^?1) for human consumption for all species. The Hg concentration ranged between < Limit of detection and 6.303 mg kg^?1, and in the crevalle jack and Atlantic tarpon, concentrations exceeded the MPL (0.5 mg kg^?1). The levels of Cd and As were not significant in the studied species and did not exceed the MPL (0.05 mg kg^?1).     

Assessing the potential of using biochar in mine rehabilitation under elevated atmospheric CO<Subscript>2</Subscript> concentration

Purpose

Re-establishment of soil nitrogen (N) capital is a priority in mine rehabilitation. We aimed to evaluate the effects of biochar addition on improving mine spoil N pools and the influence of elevated CO₂ concentration on mine rehabilitation.

Materials and methods

We assessed the effects of pinewood biochar, produced at three temperatures (650, 750 and 850 °C, referred as B₆₅₀, B₇₅₀ and B₈₅₀, respectively), on mine spoil total N concentrations with five different plant species, including a tree species (Eucalyptus crebra), N-fixing shrubs (Acacia floribunda and Allocasuarina littoralis) and C₃ and C₄ grasses (Austrodanthonia tenuior and Themeda australis) incubated at ambient (400 μL L^?1) and elevated (700 μL L^?1) atmospheric CO₂ concentrations, as well as the effects of elevated CO₂ on mine rehabilitation.

Results and discussion

Soil total N significantly improved following biochar incorporation under all plant species (P < 0.05) except for T. Australis. E. crebra had the highest soil total N (0.197%, 0.198% and 0.212% for B₆₅₀, B₇₅₀ and B₈₅₀, respectively). Different from the negligible influence of elevated CO₂ on soil properties under the grasses and the N-fixing shrubs, elevated CO₂ significantly increased soil water and hot water extractable organic C (WEOC and HWEOC, respectively) and decreased total C under E. crebra, indicating that the nutrient demands were not met.

Conclusions

Biochar addition showed the potential in mine rehabilitation in terms of improving soil N pool, especially with E. crebra. However, it would be more difficulty to rehabilitate mine spoils in future with the rising atmospheric CO₂ concentration.

     

The Influence of Humification Degree of Humic Acid on Its Sorption of Norfloxacin During Sewage Sludge Composting

Norfloxacin (NOR), an antibiotic widely used in livestock and poultry production, has become ubiquitous in the aquatic and terrestrial ecosystems as a result of veterinary excretion of the parent compound or its active metabolites. The sorption of NOR onto humic acid (HA) may influence the fate of NOR in the environment. In the present study, HA was extracted from sewage sludge in different composting stages of days 0, 10, 30, and 70 to investigate the sorption of NOR onto HA as affected by the humification degree of HA. The results of elemental and Fourier transform infrared (FTIR) spectrum analyses showed that the contents of aromatic and carboxylic groups in HA increased with composting time, indicating an increase of humification degree. The result of sorption experiments demonstrated that the HA had a high sorption capacity for NOR with strong nonlinearity. A two-stage sorption was observed in the sorption process with an equilibration time of 48 h. Both the Freundlich model (Adj. R² range 0.988–0.994) and Langmuir model (Adj. R ² range 0.917–0.928) fitted well with all sorption isotherms of the HA samples of different humification degrees. Moreover, the increase of sorption distribution coefficient (K _d ) value with composting time indicated that the sorption affinity of HA for NOR increased with increasing humification degree of HA. The major sorption mechanism was the interaction between NOR and rich aromatic moieties and carboxylic group in the HA.     

Concentrations and Exports of Fecal Indicator Bacteria in Watersheds with Varying Densities of Onsite Wastewater Systems

The research goal was to determine if onsite wastewater system (OWS) density had an influence on the concentrations and watershed exports of Escherichia coli and enterococci in urbanizing watersheds. Eight watersheds with OWS densities ranging from <?0.1 to 1.88 systems ha^?1 plus a watershed served by sewer (Sewer) and a mostly forested, natural watershed (Natural) in the Piedmont of North Carolina served as the study locations. Stream samples were collected approximately monthly during baseflow conditions between January 2015 and December 2016 (n?=?21). Median concentrations of E. coli (2014 most probable number (MPN) 100 mL^?1) and enterococci (168 MPN 100 mL^?1) were elevated in streams draining watersheds with a high density of OWS (>?0.77 system ha^?1) relative to watersheds with a low (<?0.77 system ha^?1) density (E. coli: 204 MPN 100 mL^?1 and enterococci: 88 MPN 100 mL^?1) and control watersheds (Natural: E. coli: 355 MPN 100 mL^?1 and enterococci: 62 MPN 100 mL^?1; Sewer: 177 MPN 100 mL^?1 and 130 MPN 100 mL^?1). Samples collected from watersheds with a high density of OWS had E. coli and enterococci concentrations that exceeded recommended thresholds 88 and 57% of times sampled, respectively. Results show that stream E. coli and enterococci concentrations and exports are influenced by the density of OWS in urbanizing watersheds. Cost share programs to help finance OWS repairs and maintenance are suggested to help improve water quality in watersheds with OWS.     

Copper Binding by Activated Biochar Fibres Derived from <Emphasis Type="Italic">Luffa cylindrica</Emphasis>

The adsorption of copper (Cu(II)) from aqueous solutions by activated Luffa cylindrica biochar fibres has been investigated by means of batch equilibrium experiments and FTIR spectroscopy. The effect of various physicochemical parameters, such as pH, initial metal concentration, ionic strength, mass of the adsorbent, contact time and temperature, has been evaluated by means of batch type adsorption experiments. FTIR spectroscopy, as well as acid-base titrations, was used for the characterization of the material and the surface species formed. According to the experimental results even at pH 3, the relative sorption is above 85% and the adsorption capacity of the activated biochar fibres for Cu(II) is q _max = 248 g kg^?1. Moreover, the interaction between the surface carboxylic moieties and Cu(II) results in the formation of very stable inner-sphere complexes (?G ^o = ?11.2 kJ mol^?1 at pH 3 and ?22.4 kJ mol^?1 at pH 5.5).     

An overlooked nitrogen loss linked to anaerobic ammonium oxidation in estuarine sediments in China

Purpose

Despite its importance, anammox (anaerobic ammonium oxidation) in estuarine sediment systems remains poorly understood, particularly at the continental scale. This study aimed to understand the abundance, diversity, and activity of anammox bacteria and to determine the main factors influencing the anammox process in estuarine sediments in China.

Materials and methods

Estuarine sediments were collected from 18 estuaries spanning over 4000 km. Experiments using an ¹⁵ N–tracer, quantitative PCR, and clone library construction were used to determine the activity, abundance, and diversity of anammox bacteria. The impact of environmental factors on anammox processes was also determined.

Results and discussion

The abundance of the anammox-specific hydrazine synthase (hzsB) gene ranged from 1.8 × 10⁵ ± 3.4 × 10⁴ to 3.6 × 10⁸ ± 7.5 × 10⁷ copies g^?1 dw. Candidatus Scalindua, Brocadia, Kuenenia, Jettenia, and two novel unidentified clusters were detected, with Scalindua dominating the anammox population. Additionally, the abundances of Scalindua, Kuenenia, and Brocadia were found to be significantly correlated with latitude. The anammox rates ranged from 0.29 ± 0.15 to 13.68 ± 3.98 nmol N g^?1 dw h^?1 and contributed to 2.39–82.61% of total N₂ production. Pearson correlation analysis revealed that the anammox rate was positively correlated with total nitrogen, total carbon, and temperature, and was negatively correlated with dissolved oxygen (DO). The key factors influencing the hzsB gene abundance were ammonium concentration, salinity, and DO. Ammonium concentration, pH, temperature, and latitude were main variables shaping the anammox-associated bacterial community.

Conclusions

Our results suggested that anammox bacteria are ubiquitous in coastal estuaries in China and underline the importance of anammox resulting in N loss at a continental scale.

     

Effect of Metals on Decolorization of Reactive Blue HERD by <Emphasis Type="Italic">Comamonas</Emphasis> sp. UVS

Comamonas sp. UVS was able to decolorize Reactive Blue HERD (RBHERD) dye (50 mg L^?1) within 6 h under static condition. The maximum dye concentration degraded was 1,200 mg L^?1 within 210 h. A numerical simulation with the model gives an optimal value of 35.71?±?0.696 mg dye g^?1 cell h^?1 for maximum rate (V_max) and 112.35?±?0.34 mg L^?1 for the Michaelis constant (K_m). Comamonas sp. UVS has capability of decolorization of RBHERD in the presence of Mg²⁺, Ca²⁺, Cd²⁺, and Zn²⁺, whereas decolorization was completely inhibited by Cu²⁺. Metal ions also affected the levels of biotransformation enzymes during decolorization of RBHERD. Comamonas sp. UVS was also able to decolorize textile effluent with significant reduction in COD. The biodegradation of RBHERD dye was monitored by UV–vis spectroscopy, FTIR spectroscopy, and HPLC.     

Sorption of humic acid on Fe oxides,bacteria, and Fe oxide-bacteria composites

Purpose

Sorption of humic substances on other soil components plays an important role in controlling their function and fate in soil. Sorption of humic substances by individual soil components has been studied extensively. However, few studies reported the sorption characteristic of humic substances on composites of soil components. This study aimed to investigate the sorption characteristics of humic acid on Fe oxide-bacteria composites and improve the understanding on the interaction among humic substance Fe oxide bacteria in soil.

Materials and methods

Humic acid was purchased from Sigma-Aldrich and was purified. Hematite and ferrihydrite were synthesized in the lab. Bacillus subtilis and Pseudomonas putida were cultivated in Luria-Broth medium and harvested at stationary growth phase. Batch sorption experiments were carried out at pH 5.0. Various amounts of humic acid were mixed with 20 mg of Fe oxide, bacteria, or Fe oxide-bacteria composite (oxide to bacteria of 1:1) in 10 mL of KCl (0.02 mol L^?1) to construct sorption isotherms. The effects of phosphate concentration and addition order among humic acid, Fe oxide, bacteria on the sorption of humic acid were also studied. The sorption of humic acid was calculated by the difference between the amount of humic acid added initially and that remained in the supernatant.

Results and discussion

The maximum sorption of humic acid on hematite, ferrihydrite, B. subtilis and P. putida was 73.2, 153.5, 69.1, and 56.7 mg C g^?1, respectively. The maximum sorption of humic acid on examined Fe oxide-bacteria composite was 28.2–57.2 % less than the predicted values, implying that the sorption of humic acid was reduced by the interaction between Fe oxides and bacteria. The presence of phosphate exerted negligible influence on the sorption of humic acid on bacteria while it inhibited the sorption of humic acid on Fe oxides. On Fe oxide-bacteria composites, inhibiting influences followed by promoting or weak inhibiting effects of phosphate with increasing concentration on the sorption of humic acid were found.

Conclusions

The interaction between Fe oxides and bacteria reduced the sorption of humic acid; moreover, the reduction was greater by the interaction of bacteria with ferrihydrite than that with hematite. Phosphate exerted negligible and inhibiting influence on the sorption of humic acid by bacteria and Fe oxides, respectively. On Fe oxide-bacteria composites, humic acid sorption was initially inhibited and then promoted or weakly inhibited by phosphate with increasing concentration.     

Tillage system affects fertilizer-induced nitrous oxide emissions

Since the development of effective N₂O mitigation options is a key challenge for future agricultural practice, we studied the interactive effect of tillage systems on fertilizer-derived N₂O emissions and the abundance of microbial communities involved in N₂O production and reduction. Soil samples from 0–10 cm and 10–20 cm depth of reduced tillage and ploughed plots were incubated with dairy slurry (SL) and manure compost (MC) in comparison with calcium ammonium nitrate (CAN) and an unfertilized control (ZERO) for 42 days. N₂O and CO₂ fluxes, ammonium, nitrate, dissolved organic C, and functional gene abundances (16S rRNA gene, nirK, nirS, nosZ, bacterial and archaeal amoA) were regularly monitored. Averaged across all soil samples, N₂O emissions decreased in the order CAN and SL (CAN?=?748.8?±?206.3, SL?=?489.4?±?107.2 μg kg^?1) followed by MC (284.2?±?67.3 μg kg^?1) and ZERO (29.1?±?5.9 μg kg^?1). Highest cumulative N₂O emissions were found in 10–20 cm of the reduced tilled soil in CAN and SL. N₂O fluxes were assigned to ammonium as source in CAN and SL and correlated positively to bacterial amoA abundances. Additionally, nosZ abundances correlated negatively to N₂O fluxes in the organic fertilizer treatments. Soils showed a gradient in soil organic C, 16S rRNA, nirK, and nosZ with greater amounts in the 0–10 than 10–20 cm layer. Abundances of bacterial and archaeal amoA were higher in reduced tilled soil compared to ploughed soils. The study highlights that tillage system induced biophysicochemical stratification impacts net N₂O emissions within the soil profile according to N and C species added during fertilization.