Calmodulin-like protein MdCML15 interacts with MdBT2 to modulate iron homeostasis in apple.

BTB and TAZ domain proteins (BTs) function as specialized adaptors facilitating substrate recognition of the CUL3-RING ubiquitin ligase (CRL3) complex that targets proteins for ubiquitination in reaction to diverse pressures. Nonetheless, knowledge of the molecular mechanisms by which the apple scaffold protein MdBT2 responds to external and internal signals is limited. Here we demonstrate that a putative Ca 2+ sensor, calmodulin-like 15 (MdCML15), acts as an upstream regulator of MdBT2 to negatively modulate its functions in plasma membrane H+-ATPase regulation and iron deficiency tolerance. MdCML15 was identified to be substantially linked to MdBT2, and to result in the ubiquitination and degradation of the MdBT2 target protein MdbHLH104. Consequently, MdCML15 repressed the MdbHLH104 target, MdAHA8's expression, reducing levels of a specific membrane H+-ATPase. Finally, the phenotype of transgenic apple plantlets and calli demonstrated that MdCML15 modulates membrane H+-ATPase-produced rhizosphere pH lowering alongside iron homeostasis through an MdCML15-MdBT2-MdbHLH104-MdAHA8 pathway. Our results provide new insights into the relationship between Ca2+ signaling and iron homeostasis.

Biological characterization and regulation of soil health.

How to determine the soil health status effectively is the basic issue to realize the agriculture green development. In the existing soil health assessment system, the importance of soil organi-sms in the maintenance of soil health is rarely considered. From the perspective of soil biological health, we discussed the connotation of soil health, and summarized the biological indicators of soil health, including soil microorganisms, soil enzyme activity, soil micro-food web and earthworm. Based on the above-mentioned indicators, the regulation approaches were elaborated from the aspects of crop and soil management practices. In addition, the future research on soil biological health was prospected. The main aim of this study is to enhance the understanding of scientists and decision makers on the maintenance of soil biological health, and to give full consideration of the important role of soil organisms in ecosystem services.

Oxidation degradation of 2,2',5-trichlorodiphenyl in a chelating agent enhanced Fenton reaction: Influencing factors, products, and pathways.

The sodium pyrophosphate (SP)-enhanced Fenton reaction has been proven to have promising potential in remediation of polychlorinated biphenyls in soils by keeping iron ions soluble at high pH and minimizing the useless decomposition of H2O2. However, little information can be obtained about the effect of environmental factors on its remediation performance. Thus, the effect of environmental factors on the degradation of 2,2',5-trichlorodiphenyl (PCB18), one of the main PCB congeners in Chinese sites, was investigated in this study. PCB18 degradation was sensitive to pH, which ranged from 39.8% to 99.5% as increased pH from 3.0 to 9.0. ·OH was responsible for PCB18 degradation at pH 5.0, while both ·OH and O2- resulted in PCB 18 degradation at pH 7.0 with the calculated reaction activation energy of 73.5 kJ mol-1. Bivalent cations and transition metal ions decreased PCB18 degradation markedly as their concentrations increased. The addition of humic acid had an inhibitory on PCB18 degradation, but no obvious inhibition of PCB18 removal was observed when the same concentration of fulvic acid was added. The addition of 1 and 10 µM model humic constituents (MHCs) promoted PCB18 degradation, but the addition of 100 µM MHCs decreased PCB18 removal. Biphenyl, two dichlorobiphenyl, and two hydroxy trichlorobiphenyl derivatives were identified as the major degradation products of PCB18 in the Fe2+/SP/H2O2 system at pH 7.0. Thus, an oxidative pathway contributed by OH and a reductive pathway induced by O2- were proposed as the main mechanisms for PCB18 degradation in the SP-enhanced Fenton reaction.

BTB-BACK Domain E3 Ligase MdPOB1 Suppresses Plant Pathogen Defense against Botryosphaeria dothidea by Ubiquitinating and Degrading MdPUB29 Protein in Apple.

Apple ring rot is a severe disease that affects the yield and quality of apple fruits worldwide. However, the underlying molecular mechanism that involved in this process still remains largely unexplored. Here, we report that apple POZ/BTB CONTAINING-PROTEIN 1 (MdPOB1), a BTB-BACK domain E3 ligase protein, functions to suppress apple pathogen defense against Botryosphaeria dothidea (B. dothidea). Both in vitro and in vivo assays indicated that MdPOB1 interacted directly with and degraded apple U-box E3 ligase MdPUB29, a well-established positive regulator of plant innate immunity, through the ubiquitin/26S proteasome pathway. A series of transgenic analyses in apple fruits demonstrated that MdPOB1 affected apple pathogen defense against B. dothidea at least partially, if not completely, via regulating MdPUB29. Additionally, it was found that the apple pathogen defense against B. dothidea was correlated with the H2O2 contents and the relative expression of salicylic acid (SA) synthesis- and SA signaling-related genes, which might be regulated via degradation of MdPUB29 by MdPOB1. Overall, our findings provide new insights into the mechanism of the MdPOB1 modulation of apple ring rot resistance, which occur by directly regulating potential downstream target protein MdPUB29 for proteasomal degradation in apple.

Sorption of copper and norfloxacin onto humic acid: effects of pH, ionic strength, and foreign ions.

Copper (Cu) and norfloxacin (Nor) are frequently used as feed additives for animal growth promotion, which results in a great probability of Cu2+ and Nor coexisting in animal excretion and in soils. Sorption of Cu2+ and Nor on soil organic matter (SOM) can markedly affect their environmental fate. Thus, humic acid (HA), a major fraction of SOM, was chosen to investigate the cosorption behaviors of Cu2+ and Nor on HA under different solution chemistry conditions (pHs, ionic strengths, and foreign ions). The addition of Nor decreased the maximum adsorption capacity (Qm) of Cu2+ and an increasing effect was observed with increasing Nor concentration. Meanwhile, the addition of Cu2+ also markedly inhibited the sorption of Nor on HA. The Qm of Cu2+ increased with increasing pH from 3.0 to 5.0 whether Nor was present or not, but more addition of Nor led to less increment in Qm of Cu2+ at the same pH. The Qm of Nor was observed at pH 4.0 without Cu2+, but that was found at pH 5.0 and 3.0 with the addition of 20 and 100 mg L-1 Cu2+, respectively. The sorption of Cu2+ on HA decreased with increasing ionic strength and followed an order of NaH2PO4 > Na2SO4 ≈ NaNO3 at pH 5.0 whether Nor was present or not. Additionally, the higher valence cation had a stronger inhibition effect on Cu2+ sorption. The competition between Cu2+ and Nor for sorption on HA under the same conditions indicated that the coexistence of Cu2+ and Nor may enhance the feasibility of their mobility and environmental risk.

The apple U-box E3 ubiquitin ligase MdPUB29 contributes to activate plant immune response to the fungal pathogen Botryosphaeria dothidea.

MAIN CONCLUSION: MdPUB29 is a positive regulator of the defense response to the fungal pathogen Botryosphaeria dothidea possibly by directly regulating the salicylic acid (SA) content as well as SA synthesis-related and signaling-related gene transcription. In plants, ubiquitin E3 ligases containing a U-box domain (PUBs, Plant U-box E3 ubiquitin ligase) have been identified as key regulators of fundamental cellular processes, such as cellular growth, development, and apoptosis, as well as biotic and abiotic stress responses. However, the function of PUBs in apple ring rot remains elusive. Here, we isolated the U-box E3 ligase MdPUB29 from the apple cultivar 'Royal Gala' and characterized its function in plant pathogen defense against Botryosphaeria dothidea. qRT-PCR showed that the expression of MdPUB29 was significantly induced in apple fruits after B. dothidea infection. Overexpression of the MdPUB29 gene in apple calli increased the resistance to B. dothidea infection. In contrast, silencing MdPUB29 in apple calli resulted in reduced resistance. Ectopic expression of MdPUB29 in Arabidopsis also exhibited enhanced resistance to B. dothidea infection compared to that of the wild-type (Col) control. In addition, it was found that the increase of plant pathogen defense was correlated with the increased salicylic acid (SA) content, as well as SA synthesis-related and signaling-related gene transcription in comparison to the wild type. We elucidated the mechanism by which MdPUB29 elevates plant pathogen defense against B. dothidea possibly by regulating the SA pathway.

Study on Molecular Recognition of Cucurbit[6]uril with Oxytetracycline Molecules by Spectroscopic Methods.

The molecular recognition of Cucurbit[6]uril (CB[6]) with Oxytetracycline (OTC) was studied by fluorescence spectra and UV spectra. The results showed that the fluorescence intensity and the UV absorbance of OTC were enhanced as host molecules were added, which showed that CB[6] and OTC were interacted. The inclusion of OTC was detected by fluorescence spectra and UV spectra with an apparent 1∶1 interaction, which was also observed through the Benesi-Hildebrand method, OTC can form 1∶1 complex with CB[6] under acid condition and it can not form complex with CB[6] under basic condition. The thermodynamic parameters (stability constants Ks, Gibbs free energy change ΔG, enthalpy change, and entropy change) for the complexation process were determined. The thermodynamic studies indicated that the inclusion reactions between CB[6] and OTC were the hydrophobic interaction and endothermic process.

Effect of different levels of nitrogen on rhizosphere bacterial community structure in intensive monoculture of greenhouse lettuce.

Pyrosequencing-based analyses revealed significant effects among low (N50), medium (N80), and high (N100) fertilization on community composition involving a long-term monoculture of lettuce in a greenhouse in both summer and winter. The non-fertilized control (CK) treatment was characterized by a higher relative abundance of Actinobacteria, Acidobacteria, and Chloroflexi; however, the average abundance of Firmicutes typically increased in summer, and the relative abundance of Bacteroidetes increased in winter in the N-fertilized treatments. Principle component analysis showed that the distribution of the microbial community was separated by a N gradient with N80 and N100 in the same group in the summer samples, while CK and N50 were in the same group in the winter samples, with the other N-level treatments existing independently. Redundancy analysis revealed that available N, NO3(-)-N, and NH4(+)-N, were the main environmental factors affecting the distribution of the bacterial community. Correlation analysis showed that nitrogen affected the shifts of microbial communities by strongly driving the shifts of Firmicutes, Bacteroidetes, and Proteobacteria in summer samples, and Bacteroidetes, Actinobacteria, and Acidobacteria in winter samples. The study demonstrates a novel example of rhizosphere bacterial diversity and the main factors influencing rizosphere microbial community in continuous vegetable cropping within an intensive greenhouse ecosystem.

Soil washing in combination with homogeneous Fenton-like oxidation for the removal of 2,4,4'-trichlorodiphenyl from soil contaminated with capacitor oil.

Detoxification by chemical oxidation of polychlorinated biphenyls (PCBs) in contaminated soils is very difficult and inefficient because PCBs typically associate with the solid phase or exist as non-aqueous-phase liquids due to their low solubility and slow desorption rates, and thus, they are difficult to remove from soils by using traditional, water-based elution techniques. Surfactant can enhance washing efficiency of PCBs from contaminated soils. This study used Brij 58, Brij 30, Tween 80, and 2-hydroxypropyl-ß-cyclodextrin (HPCD) to solubilize 2,4,4'-trichlorodiphenyl (PCB28) from soil contaminated with capacitor oil into solution. The feasibility of PCB28 oxidation in soil washing wastewater through a Fe(3+)-catalyzed Fenton-like reaction was subsequently examined. Washing with 10 g L(-1) Brij 58 solution showed the highest extraction efficiency (up to 61.5 %) compared with that of the three other surfactants. The total concentration of PCB28 in contaminated soil at 25 °C after 48-h extraction was 286 mg L(-1). In contrast to conditions in which no washing agent was added, addition of the four washing agents decreased the efficiency of PCB28 degradation by the Fenton-like reaction, with the decrease due to addition of 10 g L(-1) Brij 58 solution being the smallest. The optimal concentration of H2O2 for preventing its useless decomposition was found to be 50 mM. The efficiency of PCB28 removal was lower when the initial concentration of PCB28 treated in the Fenton-like reaction was higher. The degradation efficiencies of PCB28 at initial concentrations of 0.1, 10, and 176 mg L(-1) in 10 g L(-1) Brij 58 solution at 25 °C and pH 3.0 and 9 h of reaction using 50 mM H2O2 were 64.1, 42.0, and 34.6 %, respectively. This result indicates that soil washing combined with Fenton-like oxidation may be a practical approach for the remediation of PCB-contaminated soil.

Quantitative characterization of hydroxyl radical generation in a goethite-catalyzed Fenton-like reaction.

In order to find out the truth of influence of solution chemistry on the oxidation efficiency of a goethite-catalyzed Fenton-like reaction, the amount of hydroxyl radicals (OH) was quantified by using coumarin as its trapping agent to produce the only fluorescent derivative 7-hydroxycoumarin (7-HC), because OH was the reactive species responsible for the oxidation activity of Fenton reactions. The concentration of OH achieved maximum at solution pH of 3 and decreased with an increase of solution pH value. However, considerable amount of OH can also generate at near neutral pH (i.e. pH 6 and 7). The concentration of OH was increased both with increasing of goethite and H2O2 dosages, but H2O2 could compete with coumarin to scavenge OH to reduce the formation of 7-HC when the concentration of H2O2 was too high. Anions inhibited OH generation followed an order of H2PO4(-)>SO4(2-)>Cl(-)>NO3(-)>ClO4(-). Higher concentrations of Cl(-) and SO4(2-) resulted in greater inhibition of OH generation. Results of this study demonstrated that the influence of solution chemistry on the oxidation efficiency of the goethite-catalyzed Fenton-like reaction was greatly attributed to the effect of solution chemistry on the amount of OH formed in the process of reaction.

Kinetics and products of PCB28 degradation through a goethite-catalyzed Fenton-like reaction.

Efficiencies of 2,4,4'-trichlorobiphenyl (PCB28) degradation in a goethite-catalyzed Fenton-like system under various conditions were investigated. Up to 99% of PCB28 was degraded in the Fenton-like system after 48 h. The hydroxyl radical was responsible for the degradation of PCB28 at pH 3-7. Degradation of PCB28 and H2O2 followed pseudo-first-order kinetics. The rate of PCB28 degradation decreased when the pH increased from 3 to 7, but increased with increasing concentration of goethite and H2O2. The rate of H2O2 decomposition increased at higher pH and goethite concentration, and decreased at lower H2O2 concentration. The half-lives of 4-chlorobiphenyl, 4,4'-dichlorobiphenyl, 2,4,4'-trichlorobiphenyl, and 2,2',4,4'-tetrachlorobiphenyl were 1.8, 3.5, 4.1, and 11h, respectively; therefore, the number of chlorine atoms in the biphenyl molecule determined the chemical reactivity of PCBs. By gas chromatography-mass spectrometry, one monochlorobiphenyl, three dichlorobiphenyl, and two hydroxytrichlorobiphenyl derivatives were identified as major products of PCB28 degradation. The decrease in pH of the reaction mixture after 48h reaction revealed that acidic products might be formed during degradation.

Sorption of cyromazine on humic acid: Effects of pH, ionic strength and foreign ions.

Cyromazine (CY) is a triazine pesticide used as an insect growth inhibitor for fly control in cattle manure, field crops, vegetables, and fruits. Sorption of CY onto humic acid (HA) may affect its environmental fate. In this study, HA was used to investigate the sorption of CY at different solution chemistry conditions (pH, ionic strength) and in the presence of foreign ions and norfloxacin. All sorption isotherms fitted well with the Freundlich and Langmuir models. The sorption reached a maximum at initial pH 4.0 over the initial pH range of 3.0-7.0, implying that the primary sorption mechanism was cation exchange interaction between CY+ species and the negatively charged functional groups of HA. Increasing Ca2+ concentration resulted in a considerable reduction in the Kd values of CY, hinting that Ca2+ had probably competed with CY+ for the cation exchange sites on the surfaces of HA. The sorption of CY on HA in different ionic media followed the order of NH4Cl ≈ KCl > K2SO4 > ZnCl2 ≈ CaCl2 at pH 5.0. Spectroscopic evidence demonstrated that the amino groups and triazine ring of CY was responsible for sorption onto HA, while the carboxyl group and the O-alkyl structure of HA participated in adsorbing CY.

Sorption characteristics of cyromazine and its metabolite melamine in typical agricultural soils of China.

A myriad of physical, chemical, and biological processes controls the fate of organic contaminants in soils. The knowledge of bioavailability of a contaminant in soil can be useful to conduct environmental risk assessment. We conducted batch equilibrium experiments to investigate the sorption of cyromazine (CA) and its metabolite melamine (MA) onto five typical soils of China belonging to suborders Ali-Perudic Ferrosols, Udic Argosols, Gleyic-Stagnic Anthrosols, Ustic Cambosols, and Udic Isohumosols. Results showed that sorption of CA and MA onto soils was linear, as indicated by the Freundlich and Langmuir models. Different sorption behaviors of CA and MA were observed on the five agricultural soils, with lgK f values (Freundlich model) of 1.6505-2.6557 and 1.632-2.549, respectively. Moreover, the K f values for CA and MA were positively correlated with soil organic matter (r = 0.989, r = 0.976) and significantly negatively correlated with pH (r = -0.938, r = -0.964). The free energy of sorption of CA and MA ranged from -20.8 to -23.0 kJ mol(-1) and -20.8 to -22.8 kJ mol(-1), respectively, suggesting that the sorption of CA and MA onto the soils is primarily a physical process.

Application of microwave-irradiated manganese dioxide in the removal of polychlorinated biphenyls from soil contaminated by capacitor oil.

The removal of polychlorinated biphenyls (PCBs) from soil contaminated with capacitor oil, using microwave (MW)-irradiated manganese dioxide (MnO2), was examined under different conditions. The effects of different types of MnO2 added as oxidant, as well as the initial amount of water, MnO2, and sulphuric acid solution, were also investigated. The removal efficiencies for dichlorobiphenyls, trichlorobiphenyls, tetrachlorobiphenyls, pentachlorobiphenyls, hexachloro-biphenyls, heptachlorobiphenyls, and octachlorobiphenyls were approximately 95.9%, 82.5%, 52.0%, 71.6%, 62.5%, 28.6%, and 16.1%, respectively, by 800 W MW irradiation for 45 min with the assistance of 0.1 g delta-MnO2 and 0.2 mL water in 1.0 g severely PCB-contaminated soil (sigma PCB = 1560.82 mg/kg); meanwhile, the concentrations of Mn2+ ions detected were from 10.6 +/- 1.9 mg/kg at 0 min to 108.2 +/- 7.8 mg/kg after 45 min MW irradiation, indicating that MnO2 acted as not only a MW absorber but also an oxidizer. Removal efficiencies of PCBs from contaminated soil increased with increasing the amounts of water and MnO2 added. The type of MnO2 also affected the removal of PCBs, following an order of delta-MnO2 > alpha-MnO2 > beta-MnO2. The addition of low concentration of sulphuric acid (such as 1.0 mol/L) solution was favourable for the removal of low chloro-substituted PCBs, but the addition of more than 1.0 mol/L sulphuric acid reduced the removal of all PCBs. The pronounced removal of PCBs from contaminated soil in a short treatment time indicates that MW irradiation with the assistance of MnO2 is an efficient and promising technology for the remediation of PCB-contaminated soil.

Residues of organochlorine pesticides and polycyclic aromatic hydrocarbons in farm-raised livestock feeds and manures in Jiangsu, China.

The residual levels of 8 organochlorine pesticides (OCPs) and 15 priority polycyclic aromatic hydrocarbons (PAHs) were determined in pig, chicken, and cow feed and manure samples collected from feedlots in Jiangsu province, China. The mean residuals of OCPs ranged from 25.35 to 65.62 ng g(-1) in feeds and from 33.46 to 90.89 ng g(-1) in manures. Among 4 hexachlorocyclohexanes (HCHs), α-HCH was the most abundant compound, with a high occurrence above 80% in all kinds of animal feeds and manures. For dichlorodiphenyltrichloroethanes (DDTs), the predominance of p,p'-DDE and p,p'-DDT of total DDTs was also clearly observed. Composite profiles of HCHs and DDTs in feeds indicated that the residuals of lindane and DDTs could be attributed to new inputs in the past several years. The mean residuals of all of the PAHs varied from 128.94 to 389.66 ng g(-1) in manures. The mean concentrations of seven carcinogenic PAHs in manures varied from 16.80 to 79.70 ng g(-1). Of the 15 priority PAHs, phenanthrene was the most dominant PAH species and accounted for approximately 50% of the total PAHs in all animal manures. The distribution of PAHs with different rings showed that PAHs with 3 rings were the primary components in the tested manures.

Effect of a rock dust amendment on disease severity of tomato bacterial wilt.

Nutrients are important for growth and development of plants and microbes, and they are also important factors in plant disease control. The objective of this study was to evaluate the effect of a rock dust used as a fertilizer in maintaining health of soil and tomato plants under greenhouse conditions. Four treatments-including M (commercial organic fertilizer), A (rock dust soil amendment), M + A (commercial organic fertilizer + rock dust soil amendment) and CK (blank control)--were examined for their effect on soil properties, soil enzymatic activity, plant growth and control efficacy against tomato bacterial wilt. Treatments A and M + A were significantly better than other treatments in changing soil pH, increasing it from acidic (pH 5.13) to nearly neutral (pH 6.81 and 6.70, respectively). Enzymatic activities in soil were notably influenced by the different treatments--particularly treatment M + A, which increased the activities of alkaline phosphatase, urease, catalase and sucrase to a greater extent in soil. There was no significant difference (P < 0.05) in the effects of treatments A and M + A on tomato plant height, stem diameter and biomass. The effect of the four treatments on the chlorophyll content and photosynthetic rate (in decreasing order) were M + A, A, M and CK. The replicate greenhouse experiments showed that the control efficacies of treatments M + A, A, and M against bacterial wilt were respectively 89.99, 81.11 and 8.89 % in first experiment and with the efficacies of 84.55, 74.36, and 13.49 % in the replicate; indicating that rock dust played a key role in the plant-soil interaction. The raised soil pH and Ca content were the key factors for the rock dust amendment controlling bacterial wilt under greenhouse conditions.

Sorption of norfloxacin onto humic acid extracted from weathered coal.

Norfloxacin (NOR), is an ionizable and polar antimicrobial compound, and it may enter the environment in substantial amounts via the application of manure or sewage as a fertilizer. Sorption of NOR onto humic acid (HA) may affect its environmental fate. In this study, HA extracted from weathered coal was used to investigate the sorption of NOR at different solution chemistry conditions (pH, ionic strength) and temperatures. The sorption of NOR onto HA showed a two-stage sorption process with an equilibration time of 48 h. The sorption kinetic curve fitted well with a pseudo second-order kinetic model. Thermodynamic characteristics demonstrated that the sorption of NOR onto HA was a spontaneous and exothermic process predominated by physical sorption. All sorption isotherms fitted well with the Freundlich and Langmuir models and they were highly nonlinear with values of n between 0.4 and 0.5, suggesting the high heterogeneity of HA. Increasing Ca2+ concentration resulted in a considerable reduction in the K(d) values of NOR, hinting that Ca2+ had probably competed with NOR(+,0) for the cation exchange sites on the surfaces of HA. The sorption reached a maximum at pH 6.0 over the pH range of 2.0-8.0, implying that the primary sorption mechanism was cation exchange interaction between NOR(+,0) species and the negatively charged functional groups of HA. Spectroscopic evidence demonstrated that the piperazinyl moiety of NOR was responsible for sorption onto HA, while the carbonyl group and the aromatic structure of HA participated in adsorbing NOR.

Oxidative degradation kinetics and products of chlortetracycline by manganese dioxide.

This study investigated the abiotic transformation kinetics of chlortetracycline (CTC) by synthesized δ-MnO(2) under conditions of different solutions. CTC was rapidly oxidized by δ-MnO(2), with the generation of Mn(2+). The measured CTC transformation rate increased considerably with an increase in initial δ-MnO(2) concentration but it decreased as the initial CTC concentration increased. Both the measured CTC transformation rate and the amount of Mn(2+) generated decreased with increasing pH. The CTC transformation rate rose with an increase in temperature. The apparent activation energy (45 ± 14 kJ mol(-1)) was consistent with a surface-controlled reaction. Dissolved Mn(2+) and Zn(2+), as background cations, and substituted phenols, as co-solutes, remarkably decreased the transformation rate of CTC. Liquid chromatography-tandem mass spectrometry (LC-MS-MS) was used to identify oxidation products, which include iso-CTC, 4-epi-CTC, anhydro-CTC and 4-epi-anhydro-CTC, keto-CTC, 4-epi-keto-CTC, N-demethyl-CTC, 4-epi-N-demethyl-CTC, N-didemethyl-CTC and 4-epi-N-didemethyl-CTC. Product identification together with Fourier transform-infrared (FTIR) spectra suggested that the hydroxyl groups at C6 and C12 and the dimethylamine group of CTC reacted with the Mn-OH groups on the δ-MnO(2) surface. Thus, δ-MnO(2) in the soils most probably plays an important role in the abiotic transformation of tetracycline antibiotics.

Remediation of soils contaminated with polychlorinated biphenyls by microwave-irradiated manganese dioxide.

The removal of polychlorinated biphenyls (PCBs) using microwave-irradiated manganese dioxide (MnO(2)) in PCB-contaminated soils under different conditions is investigated. The removal of PCB77 in two actual soil samples exhibits strong pH-dependent behavior, and the removal efficiency is higher in acidic soil (Ali-Perudic Ferrosols) than that in neutral soil (Udic Argosols). The removal kinetics of PCB77 using microwave-irradiated MnO(2) under different experimental conditions fits a pseudo-first-order kinetic model well. Both the removal efficiency and the kinetic constant (k) values of PCB77 in Ali-Perudic Ferrosols considerably increase, although in a nonlinear fashion, as the initial amount of MnO(2) is increased, as the treated soil mass is increased, and as the microwave power is increased. The reactivity of three PCBs (PCB28, PCB77, and PCB118) did not present as a function of the degree of chlorination in the reaction with microwave-irradiated MnO(2). The pronounced removal of three PCBs in contaminated soil (all above 95%) indicates that MnO(2) in combination with microwave irradiation is promising for technological applications that seek to remediate sites critically polluted with PCBs.

[Effects of pH and coexisting cations on ammonia adsorption from aqueous solution by strawberry stem powder].

Batch equilibrium experiments were carried out to study ammonia adsorptions from aqueous solution by strawberry (Fragaia ananassa Duchesne) stem powder. The effects of pH, coexisting cations, initial ammonia concentration and temperature were investigated as well. The results showed that the equilibrium data fitted well to the Langmuir model and Freundlich model, and the maximum adsorption capacities were 3.05, 4.24 and 4.79 mg x g(-1) at 15, 25 and 35 degrees C respectively. The increase of temperature was favorable to ammonia adsorption. The optimal pH of ammonia adsorption was in the range of 4-8. The NH4+ content decreased at higher pH and the negative charges decreased at lower pH, resulting in the decrease of ammonia adsorption at both higher and lower pH. The pH changes after adsorption buffered both effects. K+, Na+, Ca2+ and Mg2+ had no effect on ammonia adsorption by strawberry stem, but Zn2+ and Al3+ decreased the adsorption for their hydrolyzation. The ammonia adsorption by strawberry stem powder could be applied in a large pH range and could not be affected by usual metal cations in wastewater, therefore the strawberry stem powder not only could be a suitable ammonia adsorbent, but also had advantages comparing with most mineral materials.