Enrichment of Phosphate on Ferrous Iron Phases during Bio-Reduction of Ferrihydrite

The reduction of less stable ferric hydroxides and formation of ferrous phases is critical for the fate of phosphorus in anaerobic soils and sediments. The interaction between ferrous iron and phosphate was investigated experimentally during the reduction of synthetic ferrihydrite with natural organic materials as carbon source. Ferrihydrite was readily reduced by dissimilatory iron reducing bacteria (DIRB) with between 52% and 73% Fe(III) converted to Fe(II) after 31 days, higher than without DIRB. Formation of ferrous phases was linearly coupled to almost complete removal of both aqueous and exchangeable phosphate. Simple model calculations based on the incubation data suggested ferrous phases bound phosphate with a molar ratio of Fe(II):P between 1.14 - 2.25 or a capacity of 246 - 485 mg·P·g-1 Fe(II). XRD analysis indicated that the ratio of Fe(II): P was responsible for the precipitation of vivianite (Fe3(PO4)2·8H2O), a dominant Fe(II) phosphate mineral in incubation systems. When the ratio of Fe(II):P was more than 1.5, the precipitation of Fe(II) phosphate was soundly crystallized to vivianite. Thus, reduction of ferric iron provides a mechanism for the further removal of available phosphate via the production of ferrous phases, with anaerobic soils and sediments potentially exhibiting a higher capacity to bind phosphate than some aerobic systems.

Cadmium found in peanut (Arachis hypogaea L.) kernels mainly originates from root uptake rather than shell absorption from soil

Roots and shells are two potential organs through which peanut plants absorb cadium(Cd)from soils;however,the relative contributions of the two uptake pathways(root uptake and shell absorption)to kernel Cd accumulation and their translocation characteristics are poorly understood.In this study,the relative contributions of the two pathways to Cd accumulation in two peanut cultivars,Xianghua2008(XH)and Yueyou43(YY),were accurately assessed by labeling rooting and podding zone soils with 113Cd and 111Cd isotopes(0.3 mg kg^(-1) dry soil),respectively,in a split-pot design.The results showed that approximately 96%of the Cd accumulated in the peanut kernels was derived from root uptake,while only 4%originated from shell absorption.Only 1%of the Cd accumulated in whole peanut plants was attributed to shell absorption,of which 41%–44%was retained in shells and 56%–59%was translocated to kernels.In contrast,the Cd absorbed by roots was efficiently translocated into all plant organs,of which 80%–84%was distributed in shoots.Although YY accumulated 1.3 times more Cd in whole plants than XH,the relative contributions of the two pathways to Cd accumulation in each plant organ were barely affected by peanut cultivars.Due to the strong retention effect of shells,shell-derived Cd was approximately 2 times higher than root-derived Cd in shells.These results would improve the understanding of Cd accumulation processes in peanut plants,revealing that the root uptake pathway contributes predominantly to the Cd concentration in peanut kernels,based on which strategies and technology for the reduction of Cd in peanut plants could be designed and developed.

Effect of binder addition on combustion characteristics of cotton straw pellets and kinetic analysis

In this study,the combustion characteristics and kinetics of cotton straw(CS)particles mixed with polyethylene(PE)film and coal gangue(CG)were investigated.The co-combustion characteristics of CS mixed with PE and CG at different heating rates were revealed by the thermogravimetric method and differential thermogravimetric method.The ignition temperature,burnout temperature,and maximum weight loss rate were measured,and the comprehensive combustion and flammability indexes were calculated.The results showed that the composite combustion characteristic index and flammability index increased with the increase in heating rate.The addition of PE and CG additives could effectively extend the combustion time.The Coats-Redfern(C-R)reaction model and N-order reaction model were used to evaluate the kinetic parameters of the blends.The results showed that 12.5%PE+12.5%CG particles had the lowest activation energy(Ea=103.73 kJ·mol^(-1))at the volatile combustion stage.The dynamics conform to the third-order dynamics model.In addition,the applicability of C-R model,Flynn-Wall-Ozawa(FWO)model,and Starink model in the calculation of activation energy was explored,and it was found that the FWO model is not suitable for the calculation of activation energy of biomass pellet combustion kinetics.This study provides a new method for the development and utilization of mixed fuel particles of cotton stalk and solid waste and expands the application prospect of biomass.

Rice(Oryza sativa L.)seedlings enriched with zinc or manganese:Their impacts on cadmium accumulation and expression of related genes

Cadmium(Cd)contamination in paddy soils means that the rice produced there may be unsafe for human consumption.A hydroponic study was conducted to enrich rice seedlings with zinc(Zn)or manganese(Mn),and the uptake and transport characteristics of Cd in these Zn-and Mn-rich seedlings were subsequently investigated using a greenhouse pot trial.The results showed that hydroponic cultivation in 10-50μmol L^(-1) Zn(ZnSO_(4)·7 H_(2)O)or50-250μmol L^(-1) Mn(MnSO_(4)·H_(2)O)for 30 d had no significant impact on rice growth,while the accumulation of Zn and Mn was 7.31-18.5 and 25.4-47.7 times higher,respectively,than in the control(no Zn or Mn addition).The accumulation of Cd in the Zn-and Mn-rich rice plants was 26.3%-38.6% and 34.4%-44.5% lower than that in the control,respectively,and the translocation factors of Cd from roots to shoots also decreased by 23.3%-41.3% and 25.3%-37.0%,respectively,after transplanting to Cd-contaminated soils.Furthermore,the relative expression levels of OsIRT1(Oryza sativa iron-regulated transporter 1)were downregulated by 40.1%-59.3% and 16.0%-25.9%,respectively,in the Zn-and Mn-rich seedling roots.This downregulation may indicate a possible mechanism contributing to the reductions in Cd absorption.Field experiments confirmed that the Zn-and Mn-rich seedlings produced brown rice(unpolished rice grains)with significantly decreased concentrations of Cd(34.2%-44.4%).This study provides an innovative method for reducing the food safety risks from rice grown on slightly to moderately Cd-contaminated paddy soils.

Highly sensitive luminescent lanthanide metal-organic framework sensor for L-kynurenine

L-kynurenine(L-kyn)is a marker of prostate cancer.At present,the expensive instruments are usually applied to detect L-kyn clinically,which limits its wide application for cancer diagnosis.Herein,three lanthanide metal-organic frameworks([Ln(CHO_(2))_(3)]_(n),Ln=Eu,Gd,and Tb)were designed and obtained,and detailly characterized by single crystal X-ray diffraction(SCXRD),powder X-ray diffraction(PXRD),Fourier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),and luminescence spectroscopy.Further study reveals that[Tb(CHO_(2))_(3)]_(n)is a highly selective,ultra-sensitive,of strong anti-interference,highly stable,and non-expensive sensor for prostate cancer marker L-kyn.The limit of detection(LOD)for L-kyn sensing is a highly sensitive value of 1.0×10^(−9)mol/L.Furthermore,the sensing mechanism is discussed in detail.

Migration of ammonium nitrogen in ion-absorbed rare earth soils during and post in situ mining: a column study and numerical simulation analysis

Ion-absorbed rare earth mines,leached in situ,retain a large amount of ammonium nitrogen(NH4–N)that continuously releases into the surrounding environments.However,quantitative descriptions and predictions of the transport of NH4–N across mining area with hill slopes are not fully established.Here,laboratory column experiments were designed with an inclined slope(a sand box)to examine the spatial temporal transport of NH4–N in soils collected from the ionic rare earth elements(REE)mining area.An HYDRUS-2D model simulation of the experimental data over time showed that soils had a strong adsorption capacity toward NH4–N.Chemical non-equilibrium model(CNEM)could well simulate the transport of NH4–N through the soil-packed columns.The simulation of the transport-adsorption processes at three flow rates of leaching agents revealed that low flow rate enabled a longer residence time and an increased NH4-N adsorption,but reduced the extraction efficiency for REE.During the subsequent rainwater washing process,the presence of slope resulted in the leaching of NH4–N on the surface of the slope,while the leaching of NH4–N deep inside the column was inhibited.Furthermore,the high-intensity rainfall significantly increased the leaching,highlighting the importance of considering the impact of extreme weather conditions during the leaching process.Overall,our study advances the understanding of the transport of NH4–N in mining area with hills,the impact of flow rates of leaching agents and precipitation intensities,and presents as a feasible modeling method to evaluate the environmental risks of NH4–N pollution during and post REE in situ mining activities.