Simultaneous elution of polycyclic aromatic hydrocarbons and heavy metals from contaminated soil by two amino acids derived from β-cyclodextrins

Two highly water-soluble amino acids, which derived from β-CDs, i.e., glutamic acid-β-cyclodextrin （GluCD） and ethylene-diamine- β-cyclodextrin （EDCD）, were synthesized and were examined for their effect on solubilization of anthracene （ANT）, complexation of cadmium （Cd^2＋）, and elution removal of ANT and Cd^2＋ in soil. The results showed that GluCD and EDCD were powerful complexant for ANT and Cd^2＋. In the presence of 10 g/L GIuCD and EDCD, the solubilization of ANT increased by 47.04 and 23.85 times compared to the control, respectively. GluCD resulted in approximately 90% complexation of Cd^2＋ while 70% complexation was observed for EDCD. Simultaneously, GluCD and EDCD could greatly enhance the elution removal of ANT and Cd^2＋ from soil. GluCD resulted in the highest elution efficiency of ANT and Cd^2＋. With the addition of 10 g/L GluCD, 53.5% of ANT and 85.6% of Cd^2＋ were eluted, respectively. The ANT had a negligible effect on the Cd^2＋ removal due to different complexing sites of ANT and Cd^2＋, while Cd^2＋ enhanced the ANT removal under the addition of GluCD because Cd^2＋ neutralized the -COOH group of GIuCD. Adversely, the removal of ANT was decreased with Cd^2＋ under the addition of EDCD, this was due to the fact that Cd^2＋ enhanced the polarity of EDCD molecule and inhibited the complexation between ANT and EDCD. The study suggested that GluCD could be preferred and be successfully applied to remediation of heavy metals or organic compounds in contaminated soil.

La-EDTA coated Fe_3O_4 nanomaterial:Preparation and application in removal of phosphate from water

La-EDTA-Fe3O4 was prepared by a chemical co-precipitation method. The magnetic composite was characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FT-IR）. Furthermore, the adsorption properties of La-EDTA-Fe3O4 toward phosphate in water were investigated. The uptake rate of phosphate in water by La-EDTA-Fe3O4 was 3-1000 times than that of EDTA-Fe3O4, and reached 97.8% at 7 hr. The adsorption process agreed well with the Freundlich model and kinetics studies showed that the adsorption of phosphate proceeds according to pseudo second-order adsorption kinetics. The maximum removal rate was achieved at pH 6.0-7.0. The La-EDTA-Fe3O4 had good adsorption properties and could be separated well from aqueous solution by a permanent magnet. Therefore, this nanomaterial has potential application for the removal of phosphate from large water bodies.

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi （AMF） have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony （Sb）. The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis （PCR-DGGE）. Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis （PC_A） indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis （RDA） showed that Sb contamination was the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Gloraus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.

The implications of planting mode on cadmium uptake and remobilization in rice: Field experiments across growth stages

Global rice production practices have gradually changed from a reliance on transplanting to direct seeding.Yet how this shift may alter cadmium(Cd)accumulation in rice is poorly known.Here we conducted field experiments with two rice genotypes cultivars that were planted using three methods:via direct seeding(DS),seedling throwing(ST),and manual transplanting(MT).Rice samples were collected during four growth stages.The formation and distribution of iron plaque were analyzed using DCB(dithionite-citrate-bicarbonate)extractions and observed under micro-XRF(micro X-ray fluorescence).The results revealed that,in each growth stage,DS rice was more apt to harbor Cd distributed in the plant’s aerial parts,and the Cd concentration of brown rice from DS was 21.8%–43.3%significantly higher than those from ST and MT at maturity stage(p<0.05).During the vegetative stages,the Cd uptake percentage was higher in DS than MT rice,and those plants arising from the DS method were capable of absorbing more Cd earlier in their growth and development.Conversely,using DS decreased the amount of iron plaque covering the root surface in every growth stage,especially in the critical period of Cd accumulation,such that the roots’middle areas were distinguished by a near-complete absence of iron plaque,thus weakening its role as an effective barrier to Cd uptake from soil.Collectively,this study demonstrated that implementing the DS mode of planting will increase Cd’s distribution in the aboveground parts of rice,and heightening the risk of Cd contamination in grain.

Ammonia volatilization and availability of Cu,Zn induced by applications of urea with and without coating in soils

Ammonia volatilization and the distribution of Cu and Zn were investigated in two types of soil treated with coated and uncoated urea.The rate of ammonia volatilization in two weeks after fertilizing with coated urea was 8% in soil 1 （soil derived from river alluvial deposits in Dongting Lake Plain） and 5.15% in soil 2 （red soil derived from quaternary red clay）,about half the rates observed when fertilizing with common urea,implying that the hydrolysis speed of the coated urea was lower than for common urea,and that the coated urea can increase nitrogen use efficacy.As for the availability of Cu and Zn,their concentrations decreased in the first week after fertilization,and then increased,which was contrary to the effect of treatment on soil pH.For example,when the pH was 7.99,there was 0.79mg/kg exchangeable Cu and 0.85mg/kg exchangeable Zn in the soil derived from river alluvial deposits in Dongting Lake Plain.However,the concentrations of exchangeable Cu and Zn were generally lower for the common urea treatments than those with the coated urea because the peak pH for the common urea treatment was greater.The concentrations of these elements correlated well with pH in the range 4–8 in second order polynomial fits.