Salinity and sodicity effects on respiration and microbial biomass of soil

An understanding of the effects of salinity and sodicity on soil carbon (C) stocks and fluxes is critical in environmental management, as the areal extents of salinity and sodicity are predicted to increase. The effects of salinity and sodicity on the soil microbial biomass (SMB) and soil respiration were assessed over 12weeks under controlled conditions by subjecting disturbed soil samples from a vegetated soil profile to leaching with one of six salt solutions; a combination of low-salinity (0.5dSm⁻¹), mid-salinity (10dSm⁻¹), or high-salinity (30dSm⁻¹), with either low-sodicity (sodium adsorption ratio, SAR, 1), or high-sodicity (SAR 30) to give six treatments: control (low-salinity low-sodicity); low-salinity high-sodicity; mid-salinity low-sodicity; mid-salinity high-sodicity; high-salinity low-sodicity; and high-salinity high-sodicity. Soil respiration rate was highest (56–80mg CO₂-C kg⁻¹ soil) in the low-salinity treatments and lowest (1–5mg CO₂-C kg⁻¹ soil) in the mid-salinity treatments, while the SMB was highest in the high-salinity treatments (459–565mg kg⁻¹ soil) and lowest in the low-salinity treatments (158–172mg kg⁻¹ soil). This was attributed to increased substrate availability with high salt concentrations through either increased dispersion of soil aggregates or dissolution or hydrolysis of soil organic matter, which may offset some of the stresses placed on the microbial population from high salt concentrations. The apparent disparity in trends in respiration and the SMB may be due to an induced shift in the microbial population, from one dominated by more active microorganisms to one dominated by less active microorganisms.     

超积累植物美洲商陆根中锰的累积与解毒

美洲商陆(Phytolacca am ericanaL·,pokeweed),为商陆科多年生草本植物,因其生长适应性强,生长速度快,特别是其生物量大,具有潜在的土壤重金属污染植物修复应用前景,成为近年来颇受关注的重金属超积累植物[1-4]。关于美洲商陆重金属超积累与耐受机制,是当前环境科学与生物科学领域内的一大研究热点[5-10]。相关研究业已报道了美洲商陆对锰及镉的吸收与累积[2-4],但其重金属耐受机制仍不是十分清楚。通常,对于重金属超积累植物的研究,研究者多将植物分为地上部(茎、叶)与地下部(根),并以地上部为重点关注对象。然而,植物对重金属具有耐受或超累积能力,其根必然发挥着重要作用。     

Patterns of SSR variation in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) seeds under ex situ genebank storage and accelerated ageing

Maintaining seed viability and germplasm integrity is a challenging task in conservation of plant genetic resources, as seeds under storage will lose viability and genetic changes will occur. Attempt was made to analyze the patterns of genetic changes in wheat germplasm under ex situ genebank storage and accelerated ageing treatments. A set of 16 naturally aged wheat accessions under ex situ genebank storage since 1994 were sampled. Four recently regenerated wheat accessions were selected, four random seed samples were chosen from each accession, and three of them were exposed to three different accelerated ageing treatments. These 32 seed samples in two germplasm sets displayed a range of germination rates from 4 to 98 %. Thirty-seven microsatellite markers representing 21 wheat chromosomes were applied to screen 12 seeds of each sample and 449 SSR alleles were scored. Large SSR variation was found in each germplasm set. There was 73.1 % of the total SSR variation present among the naturally aged samples and 78.2 % present among the accelerated ageing samples. Several analyses for genetic association consistently revealed no clear genetic separations among samples of high or low germination rates in both germplasm sets. Samples under different accelerated ageing treatments did not show much genetic differentiations from the original sample of each accession. Mantel tests revealed non-significant associations between SSR variability and sample germination rates for both germplasm sets. These findings are useful for understanding seed deterioration under different ageing conditions and suggest that genome-wide SSR variability may not provide sensitive markers for the monitoring of wheat seed viability.     

A Greener UV and Peroxide-Based Chemical Oxygen Demand Test

Water quality assessment typically includes the determination of chemical oxygen demand (COD) by oxidation of organic matter with Cr(VI) in an acidic medium followed by digestion. Unfortunately, the required reagents are harmful and the reaction times are rather long. We investigated earlier the use of H₂O₂ as a more environmentally friendly oxidizing agent to replace the hazardous chromates. In the present study, we have furthered this possibility by incorporating the use of H₂O₂ in the presence of UV light. A protocol has been devised and tested with standards and real samples that replaces toxic Cr(VI), halves the amount of silver sulfate required, and greatly reduces the necessary reaction time, thus yielding a faster and more environmentally sound method.     

Characteristics of Nitrogen Loss through Surface-Subsurface Flow on Red Soil Slopes of Southeast China

Soil nitrogen (N) loss related to surface flow and subsurface flow (including interflow and groundwater flow) from slope lands is a global issue. A lysimetric experiment with three types of land cover (grass cover, GC; litter cover, LC; and bare land, BL) were carried out on a red soil slope land in southeast China. Total Nitrogen (TN) loss through surface flow, interflow and groundwater flow was observed under 28 natural precipitation events from 2015 to 2016. TN concentrations from subsurface flow on BL and LC plots were, on average, 2.7–8.2 and 1.5–4.4 times greater than TN concentrations from surface flow, respectively; the average concentration of TN from subsurface flow on GC was about 36–56% of that recorded from surface flow. Surface flow, interflow and groundwater flow contributed 0–15, 2–9 and 76–96%, respectively, of loss load of TN. Compared with BL, GC and LC intercepted 83–86% of TN loss through surface runoff; GC intercepted 95% of TN loss through subsurface flow while TN loss through subsurface flow on LC is 2.3 times larger than that on BL. In conclusion, subsurface flow especially groundwater flow is the dominant hydrological rout for N loss that is usually underestimated. Grass cover has the high retention of N runoff loss while litter mulch will increase N leaching loss. These findings provide scientific support to control N runoff loss from the red soil slope lands by using suitable vegetation cover and mulching techniques.     

Zirconium-Modified Activated Sludge as a Low-Cost Adsorbent for Phosphate Removal in Aqueous Solution

A highly effective zirconium-modified activated sludge (Zr(IV)-AS) adsorbent was prepared from activated sludge and applied to remove phosphate from aqueous solutions by batch and column experiments. Characterized results revealed that zirconium was successfully loaded onto the activated sludge (AS), and the specific surface area and pore volume were substantially improved after zirconium loading on the AS. Zr(IV)-AS exhibited a high adsorption affinity for phosphate and the maximum adsorption amount was 27.55 mg P·g^?1 at 25 °C. Adsorption isotherms of phosphate could be described by the Langmuir model, and the adsorption kinetics were well described by the pseudo-second-order model. Phosphate adsorption on Zr(IV)-AS increased monotonically with decreasing solution pH. The presence of SO₄^2? in water resulted in slightly decreased phosphate adsorption on the adsorbent even at a high concentration (25 mmol/L), and a greater influence of HCO₃^? on adsorption could be ascribed to the increased solution pH with the addition of the HCO₃^?. Column adsorption experimental results showed that the adsorbent has excellent phosphate adsorption properties and that the effluent can meet the requirement of phosphorus in the national wastewater discharge standard of China. Phosphate-saturated Zr(IV)-AS can be effectively desorbed in 0.1 mol L^?1 NaOH solution, and the regenerated adsorbent still possessed the high capacity. The adsorption between the adsorbent and the phosphate is due to the electrostatic interaction and anionic exchange at the surface of the Zr(IV)-AS. Furthermore, this approach provides a possibility of treating wastewater with waste and has the potential for industrial applications for the removal of phosphate from wastewater.     

Evaluation of palygorskite for remediation of Cd-polluted soil with different water conditions

Purpose

The study aimed at comparing the effects of different water managements on soil Cd immobilization using palygorskite, which was significant for the selection of reasonable water condition.

Materials and methods

Field experiment was taken to discuss the in situ remediation effects of palygorskite on Cd-polluted paddy soils, under different water managements, using a series of variables, including pH and extractable Cd in soils, plant Cd, enzyme activity, and microorganism number in soils.

Results and discussion

In control group, the pH in continuous flooding was the highest under three water conditions, and compared to conventional irrigation, continuous flooding reduced brown rice Cd by 37.9%, and brown rice Cd in wetting irrigation increased by 31.0%. In palygorskite treated soils, at concentrations of 5, 10, and 15 g kg^?1, brown rice Cd reduced by 16.7, 44.4, and 55.6%; 13.8, 34.5, and 44.8%; and 13.1, 36.8, and 47.3% under continuous flooding, conventional irrigation, and wetting irrigation (p < 0.05), respectively. The enzyme activity and microbial number increased after applying palygorskite to paddy soils.

Conclusions

Continuous flooding was a good candidate as water management for soil Cd stabilization using palygorskite. Rise in soil enzyme activity and microbial number proved that ecological function regained after palygorskite application.

     

套筒式橡胶减振器的疲劳工况试验研究

为了准确掌握金穗4SW系列马铃薯挖掘机摆动分离筛新型套筒式橡胶减振器的疲劳工况，进行了田间试验和实验室试验。试验表明，该橡胶减振器能够满足生产实际要求和对橡胶减振器的设计寿命要求。给出了符合橡胶减振器疲劳损失衡量标准的静刚度损失值，经生产实践证明，此值具有指导生产的实际意义。     

2ZT—2型甜菜移栽机栽植系统的参数分析

对2ZT-2型甜菜移栽机栽植器进行了运动分析与仿真研究.应用ADAMS建立了移栽机栽植器的模型,通过运动学分析对2ZT-2型甜菜移栽机的相关设计参数进行了优化,得出了影响因素变化时对纸筒苗栽植状态的影响规律,并得出了该甜菜移栽机栽植器合理的特征参数值和鸭嘴开启运动规律.     

Effects of inbreeding on nodal root system morphology and architecture of white clover (<Emphasis Type="Italic">Trifolium repens</Emphasis> L.)

Plants of white clover (Trifolium repens L.) cultivar Crau, a self-fertile Crau genotype, and nine generations of inbred progeny were raised in sand culture in a glasshouse experiment. Digital images of the root systems were made and root morphological characteristics were determined on all the plants. Root architectural parameters were measured on the Crau parent and the S₁, S₄, S₆, and S₉ inbred lines. The clover roots became shorter and thicker with inbreeding but the number of root tips per plant was unchanged. Root architecture (branching pattern) was largely unaffected by inbreeding. It is concluded that inbreeding white clover will lead to shorter, thicker roots, and reduced nutrient uptake efficiency compared with the parent clover. The degree to which these deleterious traits are overcome during the development of F₁ hybrids needs to be determined.