Effect of heavy metals on soil microbial activity and diversity in a reclaimed mining wasteland of red soil area

The microbial biomass, basal respiration and substrate utilization pattern in copper mining wasteland of red soil area, southern China, were investigated. The results indicated that soil microflora were obviously different compared with that of the non-mine soil. Microbial biomass and basal respiration were negatively affected by the elevated heavy metal levels. Two important microbial ecophysiological parameters, namely, the ratio of microbial biomass C（ Cmic ）/organic C（ Corg ） and metabolic quotient（qCO2 ） were closely correlated to heavy metal stress. There was a significant decrease in the Cmic/Corg ratio and an increase in the metabolic quotient with increasing metal concentration. Multivariate analysis of Biolog data for sole carbon source utilization pattern demonstrated that heavy metal pollution had a significant impact on microbial community structure and functional diversity. All the results showed that soil microbiological parameters had great potential to become the early sensitive, effective and liable indicators of the stresses or perturbations in soils of mining ecosystems.

Characteristics of soil microbial community functional and structure diversity with coverage of Solidago Canadensis L

The relationship between Solidago canadensis L.invasion and soil microbial community diversity including functional and structure diversities was studied across the invasive gradients varying from 0 to 40%,80%,and 100% coverage of Solidago canadensis L.using sole carbon source utilization profiles analyses,principle component analysis(PCA) and phospholipid fatty acids(PLFA) profiles analyses.The results show the characteristics of soil microbial community functional and structure diversity in invaded soils strongly changed by Solidago canadensis L.invasion.Solidago canadensis L.invasion tended to result in higher substrate richness,and functional diversity.As compared to the native and ecotones,average utilization of specific substrate guilds of soil microbe was the highest in Solidago canadensis L.monoculture.Soil microbial functional diversity in Solidago canadensis L.monoculture was distinctly separated from the native area and the ecotones.Aerobic bacteria,fungi and actinomycetes population significantly increased but anaerobic bacteria decreased in the soil with Solidago canadensis L.monoculture.The ratio of cy19:0 to 18:1ω7 gradually declined but mono/sat and fung/bact PLFAs increased when Solidago canadensis L.became more dominant.The microbial community composition clearly separated the native soil from the invaded soils by PCA analysis,especially 18:1ω7c,16:1ω7t,16:1ω5c and 18:2ω6,9 were present in higher concentrations for exotic soil.In conclusion,Solidago canadensis L.invasion could create better soil conditions by improving soil microbial community structure and functional diversity,which in turn was more conducive to the growth of Solidago canadensis L.

Effects of contamination of single and combined cadmium and mercury on the soil microbial community structural diversity and functional diversity

To assess the effects of single and combined pollution of cadmium (Cd) and mercury (Hg) on soil micro-bial community structural and functional diversities, an incubation experiment was conducted, by employing two soils, namely, the marine sediment silty loam soil and the yellowish-red soil, in which five levels of Cd, Hg and Cd and Hg in combination were added. After being incubated for 56 days, the phospholipid fatty acids (PLFAs) profile and sole carbon source utilization pattern (BIOLOG) of the samples were tested. The results showed that the compo-sition of the microbial communities changed significantly at different levels of metals application. The principal component analyses (PCA) of PLFAs indicated that the structure of the microbial community was also significantly altered with increasing levels of metals, with increasing PLFAs biomarkers for fungi and actinomycetes, and in-creasing ratio of Gram-positive to Gram-negative bacteria. Sole carbon source utilization pattern analysis revealed that single and combined application of Cd and Hg inhibited significantly the functional activity of soil microorgan-isms, the functional diversity indices [Richness (S), Shannon-Wiener indices (H) and Evenness (EH)] were signifi-cantly lower in polluted soils than those in non-polluted soils, which also significantly altered with increasing levels of metals. PCA for the sole carbon source utilization pattern also indicated that the metal contamination could result in a variable soil microbial community. The results revealed that the combination of Cd and Hg had higher toxicity to soil microbial community structural and functional diversities than the individual application of Cd or Hg.

Effects of combination of plant and microorganism on degradation of simazine in soil

The degradative characteristics of simazine （SIM）, microbial biomass carbon, plate counts of heterotrophic bacteria and most probably number （MPN） of SIM degraders in uninoculated non-rhizosphere soil, uninoculated rhizosphere soil, inoculated non- rhizosphere soil, and inoculated rhizosphere soil were measured. At the initial concentration of 20 mg SIM/kg soil, the half-lives of SIM in the four treated soils were measured to be 73.0, 52.9, 16.9, and 7.8 d, respectively, and corresponding kinetic data fitted first-order kinetics. The experimental results indicated that higher degradation rates of SIM were observed in rhizosphere soils, especially in inoculated rhizosphere soil. The degradative characteristics of SIM were closely related to microbial process. Vegetation could enhance the magnitude of rhizosphere microbial communities, microbial biomass content, and heterotrophic bacterial community, but did little to influence those community components responsible for SIM degradation. This suggested that rhizosphere soil inoculated with microorganisms-degrading target herbicides was a useful pathway to achieve rapid degradation of the herbicides in soil.

Foliar application of micronutrients enhances crop stand, yield and the biofortification essential for human health of different wheat cultivars

Globally about half of the world’s population is under micronutrient malnutrition due to poor quality food intake.To overcome this problem,fortification and biofortification techniques are often used.Biofortification is considered a better option than fortification due to the easy control of nutrient deficiencies present in daily food.This field experiment was conducted to evaluate the effects of foliar application of a micronutrient mixture(MNM)consisting of zinc(Zn),iron(Fe),copper(Cu),manganese(Mn)and boron(B)on yield and flour quality of wheat.The results show the effectiveness of foliar feeding for growth and yield parameters,in addition to the enriching of wheat grains with Zn,Cu,Fe,Mn and B.Compared to the control without foliar feeding,foliar application on wheat crop increased tillering ability,spike length,grain yield and the contents of Zn,Cu,Mn,Fe and B by 21,47,22,22 and 25%in wheat flour,respectively.Therefore,foliar feeding of micronutrients could be an effective approach to enrich wheat grains with essential nutrients for correcting malnutrition.

Combined Effect of Nutrient and Pest Management on Soil Ecological Quality in Hybrid Rice Double-Cropping System

The mineral fertilizers (NPK) and pesticide, including herbicides, insecticides and fungicides, were applied alone or in combination and the soil sampling was done at different growth stages during the crop cycle to study the changes in soil organic matter, microbial biomass and their activity parameters in a paddy soil with different nutrient and pest management practices in a hybrid rice double-cropping system. A consistent increase in the electron transport system (ETS) activity was measured during the different crop growth stages of rice. The use of fertilizers (NPK) alone or with pesticides increased ETS activity, while a decline of ETS activity was noticed with pesticides alone as compared with the control. Nearly an increasing trend in soil phenol content was observed with the progression of crop growth stages, while the usage of pesticides alone caused maximum increments in the soil phenol content. The soil protein content was found nearly stable with fertilizers and/or pesticides application at various growth stages in both crops taken. But notable changes were noticed at different growth stages probably because of fluctuations in moisture and temperature at particular stages, which might have their effects on N mineralization. Marked depletions in the phospholipid content were found with the advancement of crop growth stages, while the incorporation of fertilizers and/or pesticides also produced slight changes, in which a higher decline was noticed with pesticide application alone compared with the control.

Changes of Soil Microbiological Characteristics After Solidago canadensis L. Invasion

The relationship between Solidago canadensis L. invasion and soil microbial communities was studied across the invasive gradients varying from 0 to 40, 80, and 100% coverage of S. canadensis. The results showed both soil microbial biomass C （Cmic） and N （Nmic） increased as the coverage of S. canadensis increased. Soil microbial quotient Cmic/Corg （microbial biomass C/organic C） tended to increase linearly with the coverage of S. canadensis. Soil basal respiration （BR） also showed a similar trend. The soil respiratory quotient qCO2 decreased with S. canadensis invasion, and remained at quite a constantly low level in the invasive soils. Sole carbon source utilization profiles analyses indicated that S. canadensis invasion tended to result in higher microbial functional diversity in the soil. Average utilization of specific substrate guilds was highest in the soil with S. canadensis monoculture. Principle component analysis of sole carbon source utilization profiles further indicated that microbial functional diversity in the soil with S. canadensis monoculture was distinctly separated from those soils in the native area and the ecotones. In conclusion, S. canadensis invasion improved soil microbial biomass, respiration and utilization of carbon sources, and decreased qCO2, thus created better soil conditions, which in turn were more conducive to the growth of S. canadensis.

Role of biochar in raising blue carbon stock capacity of salt marshes

Salt marshes are an important blue carbon ecosystem, with surprisingly fast carbon accumulation rates that are 40 times higher than those of terrestrial forests. In recent decades, salt marshes have suffered great degradation and loss all over the world. The idea to enhance carbon stock in salt marshes(so-called blue carbon) using biochar (so-called black carbon) has recently been proposed. Although experiments and observations remain limited, significant enhancements in soil organic carbon and plant growth have been documented in most case studies. However, due to the limited number of observations and their relatively short time window ranging from months to less than one year, there still exists a knowledge gap regarding the process, mechanism, and effect of biochar in enhancing carbon stock in salt marshes. Future research is urgently needed in the following perspectives:1) exploring the relationship between carbon stock enhancement efficiency and biochar properties, 2) optimizing the physical and chemical properties of biochar to boost its efficiency, and 3)studying the in-situ responses of complex carbon pools to biochar addition, especially under tidal conditions and over a longer period of time.

A mini-review of the electro-peroxone technology for wastewaters:Characteristics,mechanism and prospect

The electro-peroxone technology,a novel type of advanced oxidation technology,is widely used in wastewater treatment.Herein,this paper reviews the advantages and problems of the electro-peroxone technology compared with electrochemical oxidation technology,ozonation technology,and traditional peroxone technology.Due to the high kinetics of pollutant degradation,the electro-peroxone process can reduce the reaction time and energy consumption of pollutant treatment in wastewater.The electroperoxone technology can promote pollutant degradation and mineralization,which shows obvious synergistic effects of electrochemical oxidation and ozonation for wastewater treatment.Most importantly,the research mechanism of the electro-peroxone technology is systematically introduced from two aspects of cathode reaction and bulk reaction.The influence of experimental parameters on the wastewater treatment effect is also discussed.Finally,the potential applications and future research directions of the electro-peroxone technology in the wastewater field are proposed.The electro-peroxone process can offer a highly efficient and energy saving water treatment method to improve the performance of existing ozonation and electrochemical systems and has therefore become a promising electrochemical advanced oxidation process for wastewater treatment.

Assessment of sunflower germplasm for phytoremediation of lead-polluted soil and production of seed oil and seed meal for human and animal consumption

Phytoremediation is a valuable technology for mitigating soil contamination in agricultural lands,but phytoremediation without economic revenue is unfeasible for land owners and farmers.The use of crops with high biomass and bioenergy for phytoremediation is a unique strategy to derive supplementary benefits along with remediation activities.Sunflower(Helianthus annuus L.)is a high-biomass crop that can be used for the phytoremediation of polluted lands with additional advantages(biomass and oil).In this study,40 germplasms of sunflower were screened in field conditions for phytoremediation with the possibility for oil and meal production.The study was carried out to the physiological maturity stage.All studied germplasms mopped up substantial concentrations of Pb,with maximum amounts in shoot>root>seed respectively.The phytoextraction efficiency of the germplasm was assessed in terms of the Transfer factor(TF),Metal removal efficiency(MRE)and Metal extraction ratio(MER).Among all assessed criteria,GP.8585 was found to be most appropriate for restoring moderately Pb-contaminated soil accompanied with providing high biomass and high yield production.The Pb content in the oil of GP.8585 was below the Food safety standard of China,with 59.5% oleic acid and 32.1% linoleic acid.Moreover,amino acid analysis in meal illustrated significant differences among essential and nonessential amino acids.Glutamic acid was found in the highest percentage(22.4%),whereas cysteine in the lowest percentage(1.3%).Therefore,its efficient phytoextraction ability and good quality edible oil and meal production makes GP.8585 the most convenient sunflower germplasm for phytoremediation of moderately Pb-contaminated soil,with fringe benefits to farmers and landowners.

Influences of accumulated mileage and technological changes on emissions of regulated pollutants from gasoline passenger vehicles

In this study, the influences of accumulated mileage （deterioration） and technological changes （emission standards） on emission factors （EFs） of regulated pollutants （CO, HC, and NOx） from gasoline passenger vehicles were investigated based on Inspection and Maintenance （I/M） data using the chassis dynamometer method. The accumulated mileage of passenger vehicles was significantly linearly correlated with vehicle age. For most cases, the average EFs of CO, HC and NOx were significantly linearly correlated with accumulated mileage, indicating that emission deterioration had a significant impact on pollutant EFs. Implemented emission standards markedly influenced the EFs of regulated pollutants, and EFs markedly decreased with progressing emission standards. The present study also compared EFs of regulated pollutants between this study and the International vehicle emission （IVE） model, and marked differences in EFs were seen with variations in emission standards, vehicle types and accumulated mileage; NOx EFs in this study were higher than in the IVE model. The results provide new insight into estimating regulated pollutant emissions using the IVE model.

Response of ATP sulfurylase and serine acetyltransferase towards cadmium in hyperaccumulator Sedum alfredii Hance

We studied the responses of the activities of adenosine-triphosphate (ATP) sulfurylase (ATPS) and serine acetyltransferase (SAT) to cadmium (Cd) levels and treatment time in hyperaccumulating ecotype (HE) Sedum alfredii Hance, as compared with its non-hyperaccumulating ecotype (NHE). The results show that plant growth was inhibited in NHE but promoted in HE when exposed to high Cd level. Cd concentrations in leaves and shoots rapidly increased in HE rather than in NHE, and they became much higher in HE than in NHE along with increasing treatment time and Cd supply levels. ATPS activity was higher in HE than in NHE in all Cd treatments, and increased with increasing Cd supply levels in both HE and NHE when exposed to Cd treatment within 8 h. However, a marked difference of ATPS activity between HE and NHE was found with Cd treatment for 168 h, where ATPS activity increased in HE but decreased in NHE. Similarly, SAT activity was higher in HE than in NHE at all Cd treatments, but was more sensitive in NHE than in HE. Both ATPS and SAT activities in NHE leaves tended to decrease with increasing treatment time after 8 h at all Cd levels. The results reveal the different responses in sulfur assimilation enzymes and Cd accumulation between HE and NHE. With increasing Cd stress, the activities of sulfur assimilation enzymes (ATPS and SAT) were induced in HE, which may contribute to Cd accumulation in the hyperaccumulator Sedum alfredii Hance.

Microbial Biomass and PLFA Profile Changes in Rhizosphere of Pakchoi(Brassica chinensis L.) as Affected by External Cadmium Loading

The effects of root activity on microbial response to cadmium(Cd) loading in the rhizosphere are not well understood.A pot experiment in greenhouse was conducted to investigate the effects of low Cd loading and root activity on microbial biomass and community structure in the rhizosphere of pakchoi(Brassica chinensis L.) on silty clay loam and silt loamy soil.Cd was added into soil as Cd(NO_3)_2 to reach concentrations ranging from 0.00 to 7.00 mg kg^(-1).The microbial biomass carbon(MBC) and community structure were affected by Cd concentration,root activity,and soil type.Lower Cd loading rates(<1.00 mg kg^(-1)) stimulated the growth of pakchoi and microorganisms,but higher Cd concentrations inhibited the growth of microorganisms.The content of phospholipid fatty acids(PLFAs) was sensitive to increased Cd levels.MBC was linearly correlated with the total PLFAs.The content of general PLFAs in the fungi was positively correlated with the available Cd in the soil,whereas those in the bacteria and actinomycetes were negatively correlated with the available Cd in the soil.These results indicated that fungi were more resistant to Cd stress than bacteria or actinomycetes,and the latter was the most sensitive to Cd stress.Microbial biomass was more abundant in the rhizosphere than in the bulk soil.Root activity enhanced the growth of microorganisms and stabilized the microbial community structure in the rhizosphere.PLFA analysis was proven to be sensitive in detecting changes in the soil microbial community in response to Cd stress and root activity.

Simultaneous removal of NO and dichloromethane(CH_(2)Cl_(2)) over Nb-loaded cerium nanotubes catalyst

Herein,a series of niobium oxide supported cerium nanotubes(Ce NTs)catalysts with different loading amount of Nb_(2)O_(5)(0–10 wt.%)were prepared and used for selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR)in the presence of CH_(2)Cl_(2).Commercial V_(2)O_(5)-WO_(3)-TiO_(2) catalyst was also prepared for comparison.The physcial properties and chemical properties of the Nb_(2)O_(5) loaded cerium nanotubes catalysts were investigated by X-ray diffractometer,Transmission electron microscope,Brunauer-Emmett-Teller specific surface area,H_(2)-temperature programmed reduction,NH_(3)-temperature programmed desorption and Xray photoelectron spectroscopy.The experiment results showed that the loading amount of Nb_(2)O_(5) had a significant effect on the catalytic performance of the catalysts.10 wt.%Nb-Ce NTs catalyst presented the best NH_(3)-SCR performance and degradation efficiency of CH_(2)Cl_(2) among the prepared catalysts,due to its superior redox capability,abundant surface oxygen species and acid sites,the interaction between Nb and Ce,higher ratio of Nb^(4+)/(Nb^(5+)+Nb^(4+))and Ce^(3+)/(Ce^(3+)+Ce^(4+)),as well as the special tubular structure of cerium nanotube.This study may provide a practical approach for the design and synthesis of SCR catalysts for the simultaneously removal NOxand chlorinated volatile organic compounds(CVOCs)emitted from the stationary industrial sources.

Formyl tetrahydrofolate deformylase affects hydrogen peroxide accumulation and leaf senescence by regulating the folate status and redox homeostasis in rice

It is well established that an abnormal tetrahydrofolate(THF)cycle causes the accumulation of hydrogen peroxide(H_(2)O_(2))and leaf senescence,however,the molecular mechanism underlying this relationship remains largely unknown.Here,we reported a novel rice tetrahydrofolate cycle mutant,which exhibited H_(2)O_(2)accumulation and early leaf senescence phenotypes.Map-based cloning revealed that HPA1 encodes a tetrahydrofolate deformylase,and its deficiency led to the accumulation of tetrahydrofolate,5-formyl tetrahydrofolate and 10-formyl tetrahydrofolate,in contrast,a decrease in 5,10-methenyl-tetrahydrofolate.The expression of tetrahydrofolate cycle-associated genes encoding serine hydroxymethyl transferase,glycine decarboxylase and 5-formyl tetrahydrofolate cycloligase was significantly down-regulated.In addition,the accumulation of H_(2)O_(2)in hpa1 was not caused by elevated glycolate oxidation.Proteomics and enzyme activity analyses further revealed that mitochondria oxidative phosphorylation complex I and complex V were differentially expressed in hpa1,which was consistent with the H_(2)O_(2)accumulation in hpa1.In a further feeding assay with exogenous glutathione(GSH),a non-enzymatic antioxidant that consumes H_(2)O_(2),the H_(2)O_(2)accumulation and leaf senescence phenotypes of hpa1 were obviously compensated.Taken together,our findings suggest that the accumulation of H_(2)O_(2)in hpa1 may be mediated by an altered folate status and redox homeostasis,subsequently triggering leaf senescence.

Soil properties drive the bacterial community to cadmium contamination in the rhizosphere of two contrasting wheat(Triticum aestivum L.)genotypes

Cadmium(Cd)bioavailability in the rhizosphere makes an important difference in grain Cd accumulation in wheat.Here,pot experiments combined with 16S rRNA gene sequencing were conducted to compare the Cd bioavailability and bacterial community in the rhizosphere of two wheat(Triticum aestivum L.)genotypes,a low-Cd-accumulating genotype in grains(LT)and a high-Cd-accumulating genotype in grains(HT),grown on four different soils with Cd contamination.Results showed that there was non-significant difference in total Cd concentration among four soils.However,except for black soil,DTPA-Cd concentrations in HT rhizospheres were higher than those of LT in fluvisol,paddy soil and purple soil.Results of 16S rRNA gene sequencing showed that soil type(52.7%)was the strongest determinant of root-associated community,while there were still some differences in rhizosphere bacterial community composition between twowheat genotypes.Taxa specifically colonized in HT rhizosphere(Acidobacteria,Gemmatimonadetes,Bacteroidetes and Deltaproteobacteria)could participate inmetal activation,whereas LT rhizosphere was highly enriched by plant growth-promoting taxa.In addition,PICRUSt2 analysis also predicted high relative abundances of imputed functional profiles related to membrane transport and amino acid metabolism in HT rhizosphere.These results revealed that the rhizosphere bacterial community may be an important factor regulating Cd uptake and accumulation in wheat and indicated that the high Cd-accumulating cultivar might improve Cd bioavailability in the rhizosphere by recruiting taxa related to Cd activation,thus promoting Cd uptake and accumulation.

Enhanced CH4 selectivity in CO2 photocatalytic reduction over carbon quantum dots decorated and oxygen doping g-C3N4

Graphitic carbon nitride(g-C3N4,CN)exhibits inefficient charge separation,deficient CO2 adsorption and activation sites,and sluggish surface reaction kinetics,which have been recognized as the main barriers to its application in CO2 photocatalytic reduction.In this work,carbon quantum dot(CQD)decoration and oxygen atom doping were applied to CN by a facile one-step hydrothermal method.The incorporated CQDs not only facilitate charge transfer and separation,but also provide alternative CO2 adsorption and activation sites.Further,the oxygen-atom-doped CN(OCN),in which oxygen doping is accompanied by the formation of nitrogen defects,proves to be a sustainable H^+ provider by facilitating the water dissociation and oxidation half-reactions.Because of the synergistic effect of the hybridized binary CQDs/OCN addressing the three challenging issues of the CN based materials,the performance of CO2 photocatalytic conversion to CH4 over CQDs/OCN-x(x represents the volume ratio of laboratory-used H2O2(30 wt.%)in the mixed solution)is dramatically improved by 11 times at least.The hybrid photocatalyst design and mechanism proposed in this work could inspire more rational design and fabrication of effective photocatalysts for CO2 photocatalytic conversion with a high CH4 selectivity.

Phosphomonoesterase Activities,Kinetics and Thermodynamics in a Paddy Soil After Receiving Swine Manure for Six Years

Soil phosphomonoesterase plays a critical role in controlling phosphorus(P) cycling for crop nutrition,especially in P-deficient soils.A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activities,kinetics and thermodynamics during rice growth stages after consistent swine manure application,to understand the impacts of swine manure amendment rates on soil chemical and enzymatic properties,and to investigate the correlations between soil enzymatic and chemical variables.The experiment was set out in a randomized complete block design with three replicates and five treatments including three swine manure rates(26,39,and 52 kg P ha^(-1),representing low,middle,and high application rates,respectively) and two controls(no-fertilizer and superphosphate at 26 kg P ha^(-1)).The results indicated that the grain yield and soil chemical properties were significantly improved with the application of P-based swine manure from 0 to 39 kg P ha^(-1);however,the differences between the 39(M_(39)) and 52 kg P ha^(-1) treatments(M_(52)) were not significant.The enzymatic property analysis indicated that acid phosphomonoesterase was the predominant phosphomonoesterase in the tested soil.The M_(39) and M_(52) treatments had relatively high initial velocity(V_0),maximal velocity(V_(max)),and activation grade(lgN_a) but low Michaelis constant(K_m),temperature coefficient(Q_(10)),activation energy(E_a),and activation enthalpy(ΔH),implying that the M_(39) and M_(52) treatments could stimulate the enzyme-catalyzed reactions more easily than all other treatments.The correlation analysis showed that the distribution of soil phosphomonoesterase activities mainly followed the distributions of total C and total N.Based on these results,39 kg P ha^(-1) could be recommended as the most appropriate rate of swine manure amendment.