[Mitigative Effect of Rare Earth Element Cerium on the Growth of Zinc-stressed Wheat （Triticum aestivum L.）Seedlings].

This research aimed to clarify the mitigative effect of exogenously applied rare earth element cerium （Ce） on the growth， zinc （Zn） accumulation， and physiological characteristics of wheat （Triticum aestivum L.） seedlings under Zn stress. The wheat variety studied was Bainong307 （BN307）， and Zn stress was achieved by growing seedlings in a hydroponic culture experiment with 500 µmol·L-1 Zn2 + added to the culture solution. It was found that Zn stress at 500 µmol·L-1 significantly inhibited the chlorophyll content， photosynthesis， and biomass accumulation of wheat seedlings. Seedling roots became shorter and thicker， and the lateral roots decreased under Zn stress. The Zn stress also increased MDA accumulation and the degree of cell membrane lipid peroxidation and reduced soluble protein contents and the activities of antioxidant enzymes such as superoxide dismutase （SOD）， catalase （CAT）， and ascorbate peroxidase （APX）. On the contrary， exogenous Ce decreased the adsorption and transport of Zn by the root system and alleviated the damage of Zn stress to wheat seedlings. Specifically， the increase in chlorophyll content （chlorophyll a， chlorophyll b， and total chlorophyll） and photosynthetic parameters， the enhancement of antioxidant enzymes activities and soluble protein levels， and the reduction in MDA content and the damage of lipid peroxidation to the cell membrane were all driven by exogenous Ce， which ultimately led to the increase in dry matter biomass of the root system and shoot. In summary， these results provide basic data for the application of exogenous Ce to alleviate Zn toxicity to plants.

[Characteristics of acidification and the distribution of available phosphorus along soil depths in heavy clay soils in southern Henan Province, China]. / è±«å—é»æ¿åœŸå£¤åˆ†å±‚é ¸åŒ–å’Œè€•å±‚é€Ÿæ•ˆç£·åˆ†å¸ƒç‰¹å¾.

The acidification of agricultural soil in the southern part of the North China Plain has become more obvious, which is particularly true for the heavy clay soil types, such as yellow-cinnamon and lime concretion black soils. To understand the spatial variability of the pH value and nutrients on the vertical agricultural soil profile of heavy clay soils in this area, we measured pH values and available phosphorus (AP) in 63 farmland sample points from Xiping County in the southern Henan Province. Geostatistical methods and ArcGIS technology were used to map soil pH values along three soil depths (0-10, 10-20, and 20-30 cm) and the spatial distribution of soil AP in the tillage layer (0-20 cm). Furthermore, the correlation between pH and AP was analyzed. The results showed that mean pH values of typical yellow-cinnamon and typical fluvo-aquic soils from three soil layers were 4.98, 4.93, 5.31, and 5.46, 5.81, 6.26, respectively, which gradually increased with soil depths. However, there was no significant difference among the three soil layers. Mean pH values of typical lime concretion black soil from the three soil layers were 5.23, 5.43 and 6.03, respectively, and that of the 20-30 cm soil layer was significantly higher than that of the 0-10 cm (by 0.8-1 pH unit) and the 10-20 cm layers. The pH of the 20-30 cm soil layer of the calcareous lime concretion black and moist soils were also significantly higher than that of the 0-10 and 10-20 cm soil layers. The AP contents of the typical yellow-cinnamon, typical lime concretion black, moist, typical fluvo-aquic and calcareous lime concretion black soils in 0-20 cm soil layer were 8.85-54.75, 4.27-37.49, 8.22-51.80, 6.07-34.82, and 13.22-22.85 mg·kg-1, respectively. The results of the map indicated that the areas with low AP were distributed in the middle of the study area in blocks, and the areas with high AP were distributed around the study area in dots and flakes. The pH values of the typical yellow-cinnamon, typical lime concretion black, and moist soils positively correlated with the content of AP in the 0-20 cm soil layer. In conclusion, the heavy clay soil in southern Henan Province became stratified acidification, which slowed down along the soil depth. Soil AP contents in the tillage layer were distributed unevenly in the study area, and were affected by soil types and soil pH. These results would be useful for the improvement of heavy clay soil acidification in the southern part of the North China Plain.

[Effects of Different Amendments on Fractions and Uptake by Winter Wheat in Slightly Alkaline Soil Contaminated by Cadmium and Nickel].

The effects of a single application of three amendments (biochar, lignite, and chicken manure) on the fraction transformations of soil Cd and Ni and uptake by winter wheat are reported to provide reference for passivation and the remediation of heavy metals in soil. Field experiments were conducted to investigate the effects of different passivators on the forms of Cd and Ni in soils at different growth stages of winter wheat, and to analyze the contents of Cd and Ni in different organs of wheat. The results showed that biochar increased soil pH and that lignite reduced soil pH, but not significantly. Chicken manure significantly reduced soil pH at booting and mature stages, and decreased by 0.23 and 0.20 pH units, respectively. The single application of biochar, chicken manure, or lignite did not reduce the exchangeable Ni content significantly, whereas the effect on the exchangeable Cd was significant. Lignite 2% treatment had the greatest decrease in exchangeable Cd at different growth stages of wheat, which were 30.50%, 43.34%, and 31.20%, respectively. The contents of Cd and Ni in the shoots and underground parts of wheat decreased to some extent, and the extent of these decreases increased with the increase of passivator dosage. The decrease of Cd content in wheat roots was the largest under the treatment of lignite 2% at different growth stages, reaching 38.35%, 58.00%, and 50.20% respectively. The greatest decline of Ni content in wheat roots occurred in the lignite 2% treatment at the booting (41.33% decline) and mature stages (51.35%). All the three amendments reduced the availability of Cd and Ni in slightly alkaline soil, and the passivation effect on Cd was better than that of Ni. All three amendments also effectively reduced the content of Cd and Ni in different organs of wheat plants in different growth period. The order of decreasing effect of Cd in wheat organs was lignite > biochar > chicken manure at the same dose of these three passivators.

[Transformation and Migration of Sulfur Speciation in the Rhizosphere and Bulk Soil of Paddy Soil].

A pool culture experiment was carried out to investigate the influence of different forms of sulfur fertilizers (sulfur and gypsum) on the transformation and migration of sulfur speciation in the rhizosphere and bulk soil of unpolluted and polluted paddy soils.The results showed that the redox potential (Eh) was about 93-283 mV and 83-254 mV, respectively, the soil solution pH was 7.5-8.4 and 7.7-8.4, respectively, and pe+pH was 9.1-13.2 and 9.1-12.5, respectively, in the bulk and bulk soil.Solution Eh values in Rhizosphere soil were generally higher than those in bulk soil, and solution pH in the former was generally lower than that in the latter.The different forms of inorganic sulfur followed the order of water-soluble sulfur (41%-81% of total inorganic sulfur, similarly hereinafter)>>sulfur adsorption (9%-34%)>hydrochloric acid soluble sulfur (8%-24%)>hydrochloric acid volatile sulfide (2%-8%) in the rhizosphere.In tillering and earing flowering,the concentrations of water-soluble and absorbed sulfur by application of gypsum were significantly higher than those using elemental sulfur.And its content in unpolluted paddy soil was significantly higher than that in polluted paddy soil. In the bulk soil,the forms of inorganic sulfur followed the order of water-soluble sulfur (40%-69%)>>hydrochloric acid soluble sulfur (18%-41%)>hydrochloric acid volatile sulfide (6%-16%)>adsorbed sulfur (0.7%-7.5%).The mass fractions of inorganic sulfur, organic sulphur and the total sulfur in the rhizosphere soil were in the range of 223-738 mg·kg-1, 574-1647 mg·kg-1 and 825-2287 mg·kg-1,respectively,and the corresponding fractions were in the range of 68-128 mg·kg-1, 108-391 mg·kg-1 and 200-477 mg·kg-1 in the bulk soil,respectively.Inorganic sulfur and organic sulfur of total sulfur in the rhizosphere were 20%-40% and 60%-80%, respectively, and those in the bulk were 18%-46% and 54%-82%, respectively.Total sulfur. organic sulfur and water-soluble sulfur and adsorbed sulfur and hydrochloric acid soluble sulfur in the rhizosphere were 3-11 times, 3-5 times, 5-7 times, 12-20 times, and 2-3 times of those in the bulk soil, respectively, whereas the hydrochloric acid volatile sulfur in the rhizosphere was lower than that in the bulk soil.

[Adsorption Characteristics of Arsenite on Goethite by Flow Stirring Method].

Adsorption characteristics of arsenite on goethite under the effects of the solution pH, concentration and temperature were investigated using a flow-stirring dynamic device. The results showed that the adsorption process of arsenic could be divided into rapid and slow reactions under different conditions.The maximum of arsenite adsorption fitted by the first order equation remarkably decreased with increase in the solution pH, for example, 246.9 mg·kg-1 at pH 3.0 and 99.8 mg·kg-1 at pH 7.0, respectively. The rate constant(k')of the apparent adsorption increased gradually along with the increase of solution pH, and so the half reaction time(t1/2)was smaller, and the equilibrium time of arsenic adsorption was shorter. At the same time, the b values of diffusion rate constant were reduced gradually. With the increase of arsenic concentration, the amounts of arsenic adsorption and the k' values increased gradually. The maximum amount of adsorption of arsenic was 96.5 mg·kg-1 and 249.1 mg·kg-1 when the arsenic concentration was 0.10 mg·L-1 and 1.00 mg·L-1, respectively. Adsorption constant(Kf)by the Freundlich equation decreased gradually with the extension of the reaction time and its ability of adsorption was gradually weakened. Distribution factor(RL)by Langmuir equation was between 0-1, and the adsorption of arsenic on goethite was accounted for the preferential adsorption. With the increase of temperature, the maximum amount of adsorption of arsenic was increased, for example, 241.1 mg·kg-1 at 298 K and 315.6 mg·kg-1 at 313 K, respectively. And the k' values of the apparent adsorption rate constant gradually rose in the meantime. The false thermodynamic constants were calculated using the b values of the diffusion rate by the parabolic diffusion equation. The reaction activation energy(Ea*)of Arsenic adsorption was 14.60 kJ·mol-1. The change of arsenic diffusion activation enthalpy(ΔHθ)decreased with the increase of temperature, and ΔHθ was positive in values and on behalf of the endothermic process. So the rising temperature was beneficial to the diffusion of arsenic. ΔGθ of activation free energy was increased as the temperatures rose, and helpful to accelerate the diffusion process. Entropy of activation(ΔSθ)was negative in all cases, suggesting that the system could improve its degree of order.

[Influence of Sulfur on the Formation of Fe-Mn Plaque on Root and Uptake of Cd by Rice (Oryza sativa L.)].

A pool culture experiment using exogenous Cd-polluted paddy soils was carried out to investigate the influence of different forms of sulfur fertilizers (sulfur and gypsum) on the formation of Fe-Mn plaque on rice root and the uptake of Cd by rice. The results showed that the redox potential ( Eh) was about--200-100 mV, the pH was 6.9-7.9 and the pe + pH was 4-10 in different growth periods of rice. The mass fractions of Fe and Mn plaque on rice root were 5000-13,000 mg · kg(-1) and 170-580 mg · kg(-1), respectively. The high sulfur treatment led to the formation of more Fe plaque than the low sulfur treatment, and the mass fractions of Fe plaque in both treatments were 9400 mg · kg(-1) and 8600 mg · kg(-1) respectively in the boot stage. Contents of Mn plaque, significantly different in the tiller stage by elemental sulfur treatment and gypsum treatment, were 600 mg · kg(-1) and 400 mg · kg(-1), respectively. The elemental S treatment led to the formation of more Mn plaque on rice root than the gypsum treatment. The excessive intake of Fe2+ might be prevented by the formation of the plaque which had little significant influence on the uptake of Mn2+. The mass fractions of Cd adsorbed by rice roots surface plaque were 78.8-131.1 mg · kg(-1) in tiller stage, 16.6-21.1 mg · kg(-1) in boot stage, and 3.0-9.2 mg · kg(-1) in mature stage. The high sulfur treatment led to higher adsorption of Cd by the plaque than the low sulfur treatment in the tiller stage and the boot stage, while opposite result was observed in the mature stage. The values of Cd on the plaque measured by ACA could not truly show its actual contents adsorbed. The mass fractions of Cd in the different parts of rice followed the order of roots > stem leaf > grain. The sulfur fertilizers applied significantly reduced the mass fractions of Cd uptake in different parts of rice, and the elemental sulfur treatment had better effects than the gypsum treatment before the mature stage in roots and stem leaf, and the gypsum sulfur treatment was better for grain. A certain amount of sulfur fertilizers could effectively prevent the migration of Cd from roots to stem and grain. The transfer coefficients of Cd from roots to stem leaf in the elemental sulfur treatment and the gypsum treatment were 0.13 and 0.25 in the boot stage, respectively, and the difference was significant. Elemental sulfur was more effective to prevent the Cd migration from roots to stem leaf, and the gypsum treatment was more active from roots to grain.