某火力发电厂周围小麦受SO2污染调查

对某火力发电厂排放SO2导致其周围小麦受污染的突发性事故进行了调查。通过实地勘察小麦的受害症状，发现小麦呈典型的硫氧化物危害和硫酸雾腐蚀特征；小麦生物学性状和产量调查结果表明，污染区与对照区小麦无论株高、茎粗、穗长均无显著差异。而小麦的产量已受到影响，与对照区相比差异极显著；污染区小麦叶片全硫量和水溶性硫测定结果表明，全硫量均值为0．759％，高出对照区全硫含量均值0．651％的17％，经t检验差异显著；水溶性硫含量均值0．64％，高出对照区水溶性硫含量均值0．52％的23％，经检验差异极显著，表明污染区小麦受害确系SO2所致；分析气象条件认为污染区小麦是在低气压、高湿度、低风速、偏西风和稳定天气频率偏高的状况下受到污染的。     

The Incidence of Fungi and Mycotoxins in South Africa Wheat and Wheat-Based Products

This investigation was undertaken to survey the fungal and mycotoxin contamination of South African wheat ranging from that growing in the field to processed wheat products. Samples of wheat were taken from various growing areas in South Africa and screened for fungi and mycotoxins, using a range of methodologies, including chromatography, immunoaffinity/fluorimetry, and cytotoxicity testing. Similar samples were taken from supermarkets and retail outlets in South Africa and analyzed in a similar manner. The result showed that a range of fungi and mycotoxins could be detected in wheat in all these sample types. The major fungal contaminants were Fusarium spp. and their attendant mycotoxins, in particular deoxynivalenol, which is in keeping with the observations made in the rest of the world. An interesting observation was that samples of wheat taken from the field with heavy Fusarium contamination were contaminated with fumonisin B₁, which is not normally associated with this crop. Of more concern were the low but persistent levels of mycotoxins and fungi in wheat-based products sold directly to the public.     

Secondary organic aerosol formation from straw burning using an oxidation flow reactor

Herein, we use an oxidation flow reactor, Gothenburg: Potential Aerosol Mass (Go: PAM) reactor, to investigate the secondary organic aerosol (SOA) formation from wheat straw burning. Biomass burning emissions are exposed to high concentrations of hydroxyl radicals (OH) to simulate processes equivalent to atmospheric oxidation of 0-2.55 days. Primary volatile organic compounds (VOCs) were investigated, and particles were measured before and after the Go: PAM reactor. The influence of water content (i.e. 5% and 11%) in wheat straw was also explored. Two burning stages, the flaming stage, and non-flaming stages, were identified. Primary particle emission factors (EFs) at a water content of 11% (∼3.89 g/kg-fuel) are significantly higher than those at a water content of 5% (∼2.26 g/kg-fuel) during the flaming stage. However, the water content showed no significant influence at the non-flaming stage. EFs of aromatics at a non-flaming stage (321.8±46.2 mg/kg-fuel) are larger than that at a flaming stage (130.9±37.1 mg/kg-fuel). The OA enhancement ratios increased with the increase in OH exposure at first and decreased with the additional increment of OH exposure. The maximum OA enhancement ratio is ∼12 during the non-flaming stages, which is much higher than ∼ 1.7 during the flaming stages. The mass spectrum of the primary wheat burning organic aerosols closely resembles that of resolved biomass burning organic aerosols (BBOA) based on measurements in ambient air. Our results show that large gap (∼60%-90%) still remains to estimate biomass burning SOA if only the oxidation of VOCs were included.     

Structure and function of rhizosphere and non-rhizosphere soil microbial community respond differently to elevated ozone in field-planted wheat

To assess the responses of the soil microbial community to chronic ozone(O_3), wheat seedlings(Triticum aestivum Linn.) were planted in the field and exposed to elevated O_3(e O_3)concentration. Three treatments were employed:(1) Control treatment(CK), AOT40 = 0;(2) O_3-1, AOT40 = 1.59 ppm·h;(3) O_3-2, AOT40 = 9.17 ppm·h. Soil samples were collected for the assessment of microbial biomass C, community-level physiological profiles(CLPPs), and phospholipid fatty acids(PLFAs). EO_3 concentration significantly reduced soil microbial carbon and changed microbial CLPPs in rhizosphere soil, but not in non-rhizosphere soil.The results of the PLFAs showed that e O_3 concentrations had significant effects on soil community structure in both rhizosphere and non-rhizosphere soils. The relative abundances of fungal and actinomycetous indicator PLFAs decreased in both rhizosphere and non-rhizosphere soils, while those of bacterial PLFAs increased. Thus the results proved that e O_3 concentration significantly changed the soil microbial community function and composition, which would influence the soil nutrient supply and carbon dynamics under O_3 exposure.     

Effect of fertilization and irrigation schedule on water and fertilizer solute transport for wheat crop in a sub-humid sub-tropical region

In order to increase the water and fertilizer use efficiency and decrease the losses of water and fertilizer solutes (N and P), it is necessary to assess the influence of level of fertilization and irrigation schedule on movement and balance of water and fertilizers in the root zone. With this goal, the reported study was undertaken to determine the effect of fertilization and irrigation schedule on water movement and fertilizer solute transport in wheat crop field in a sub-tropical sub-humid region. Field experiments were conducted on wheat crop of cultivar Sonalika (Triticum aestivum L.) during the years 2002–2003, 2003–2004 and 2004–2005. Each experiment consisted of four fertilizer treatments and three irrigation treatments during the wheat growth period. During the experiment, the irrigation treatments were: I₁ = 10% maximum allowable depletion (MAD) of available soil water (ASW); I₂ = 40% MAD of ASW; I₃ = 60% MAD of ASW. The fertilizer treatments during the experiment were: F₁ = control treatment with N:P₂O₅:K₂O as 0:0:0 kg ha⁻¹; F₂ = fertilizer application of N:P₂O₅:K₂O as 80:40:40 kg ha⁻¹; F₃ = fertilizer application of N:P₂O₅:K₂O as 120:60:60 kg ha⁻¹ and F₄ = fertilizer application of N:P₂O₅:K₂O as 160:80:80 kg ha⁻¹. The results of the investigation revealed that low volume high frequency irrigation results in higher deep percolation losses than the low frequency high volume irrigation with different levels of fertilization for wheat crop in coarse lateritic soil, whereas different levels of fertilization did not significantly affect soil water balance of the wheat crop root zone during all the irrigation schedules. Level of fertilization and irrigation schedule had significant effect on nitrogen leaching loss whereas irrigation schedules had no significant effect on nitrogen uptake under different levels of fertilization. On the other hand, the leaching loss of phosphorus was not significantly influenced by the irrigation schedule and level of fertilization of wheat crop. This indicated that PO₄–P leaching loss was very low in the soil solution as compared to nitrogen due to fixation of phosphorus in soils. From the observed data of nitrogen and phosphorus use efficiency, it was revealed that irrigation schedule with 40% maximum allowable depletion of available soil water with F₂ fertilizer treatment (N:P₂O₅:K₂O as 80:40:40 kg ha⁻¹) was the threshold limit for wheat crop with respect to nitrogen and phosphorus use, crop yield and environmental pollution.     

Combined effects of elevated temperature and CO2 concentration on Cd and Zn accumulation dynamics in Triticum aestivum L.

A simulated climate warming experiment was conducted to evaluate the combined effects of elevated temperature and CO_2 concentration on the bioaccumulation,translocation and subcellular distributions of Cd and Zn in wheat seedlings(Triticum aestivum L.cv.Xihan 1.) at Dingxi,Gansu Province,China.The objective was to find evidence that global climate change is affecting the bioaccumulation of Cd and Zn in T.aestivum L.cv.Xihan 1.The results showed that compared to control A,elevated temperature and CO_2 increased Cd bioaccumulation in the shoots by 1.4–2.5 times,and increased that in the roots by 1.2–1.5times,but decreased Zn levels in wheat shoots by 1.4–2.0 times,while decreased that in the roots by 1.6–1.9 times.Moreover,temperature and CO_2 concentration increase also led to increased Cd concentration,and decreased Zn concentration in subcellular compartments of wheat seedlings.The largest Cd concentration increase(174.4%) was observed in the cell wall and debris fractions of shoots after they were subjected to the highest CO_2 and temperature treatment(TC3).The largest Zn concentration decrease(53.1%) was observed in the soluble(F3) fractions of shoots after they were subjected to the medium CO_2 and temperature treatment(TC2).The temperature and CO_2 increase had no significant effect on the proportional distribution of Cd and Zn in the subcellular fractions.The root-to-shoot translocation of Cd increased with the increasing temperature and CO_2 concentration.However,the Zn distributions only fluctuated within a small range.     

Crop residue removal and fertilizer N: Effects on soil organic carbon in a long-term crop rotation experiment on a Udic Boroll

Biofuels can be produced by converting cellulose in crop residues to ethanol. This has recently been viewed as a potential supplement to non-renewable energy sources, especially in the Americas. A 50-yr field experiment was analyzed to determine the influence of (i) removing approximately 22% of the above-ground wheat (Triticum aestivum L.) residue each crop year, and (ii) N and P fertilization on soil carbon (C) in the top 15 cm depth of a fallow–wheat–wheat (F–W–W) rotation. The study was conducted from 1958 to 2007 on a clay soil, at Indian Head in sub-humid southeast Saskatchewan, Canada. Soil C concentrations and bulk densities were measured in the 0–7.5 and 7.5–15 cm depths in 1987, 1996 and 2007 and soil C changes were related to C inputs estimated from straw and root yields calculated from regressions relating these to grain yields. Two soil organic matter models [the Campbell model and the Introductory Carbon Balance Model (ICBM)] were also used to simulate and predict the effects of the treatments on soil C change over time, and to estimate likely soil C change if 50% or 95% of above-ground residues were harvested each crop year. Crop residue removal reduced cumulative C inputs from straw and roots over the 50-yr experiment by only 13%, and this did not significantly (P > 0.05) reduce soil C throughout the experiment duration. However, after 50 yr of applying N fertilizer at recommended rates, soil C increased significantly by about 3 Mg ha⁻¹ compared to the non-fertilized treatment. The simulated effect of removing 50% and 95% of the above-ground residues suggested that removing 50% of the straw would likely have a detectable effect on the soil C, while removing 95% of the straw certainly would. Measurements and model simulations suggest that adoption of no-tillage without proper fertilization will not increase soil C. Although it appears that a modest amount of residue may be safely removed from these Udic Borolls (Black Chernozems) without a measurable effect on soil C, this would only be feasible if accompanied by appropriate fertility management.     

3种毒性预测模型在镉对小麦根毒性预测中的应用及比较

一些基于重金属形态的生物毒性机理模型被广泛应用于水体和陆生生态系统,例如:自由离子活度模型(FIAM)、生物配体模型(BLM)和生物膜电势斯特恩双电层模型(GCSM),但不同模型的应用效果之间还缺乏系统比较。本研究选取小麦作为受试生物,采用水培实验进行了镉对小麦根伸长的毒性测试,通过数据分析软件对实验数据进行非线性拟合,分别建立了3种模型,并从根毒性、根表面吸附镉和根中富集镉3个方面对3个模型的预测能力进行了比较。除此之外,选取苹果酸和柠檬酸2种有机配体,研究了配体对镉生物毒性的影响。结果表明,Ca~(2+)和H~+对Cd的根毒性存在竞争效应,而Mg~(2+)、K~+和Na~+未发现竞争效应。由于BLM模型同时考虑了镉的自由离子态浓度和竞争离子的影响,在预测镉对杨麦13号根毒性和生物体内富集量时效果最好。而FIAM和GCSM模型由于计算中仅考虑了离子活度的影响,缺乏对竞争离子保护效应的考虑,因此预测效果相对较差;此外,Cd对小麦根毒性的主要受扩散过程控制,而非跨膜过程,这可能也是FIAM模型和GCSM模型预测不佳的原因之一。同时结果还发现有机配体存在时尽管降低了溶液中镉的离子活度,但未显著影响镉毒性,进一步证明了扩散过程对Cd毒性的影响。以上结果为评价和预测镉的陆生生态毒性提供了基础数据和模型依据。     

The Evaluation of Mesoporous Materials as Catalyst in Fast Pyrolysis of Wheat Straw

In this study, wheat straw was chosen as a biomass sample and the fast pyrolysis of this sample was carried out with or without catalyst at different conditions in a well-swept fixed-bed reactor. Experiments were carried out in a well-swept tubular fixed-bed reactor with a heating rate of 300°C/min, between pyrolysis temperature ranges 300–800°C in the nitrogen atmosphere. The results indicated that a maximum oil yield of 31.9% was obtained at a pyrolysis temperature of 500°C in non-catalytic procedure. Siliceous and Al-MCM-41 materials were evaluated as potential catalysts in the pyrolysis experiments. Mesoporous materials have large pore dimensions with strong acid sites. These acidic sites catalyze some reactions in pyrolysis. The product yields and the quality of bio-oil were influenced with using MCM-41 materials. The bio-oil yield was reduced, whereas the gas yield increased with using a catalyst in the experiments. An increase in the fractions of pure phenol, alkyl phenols, alkenes+alkanes, carbonyls, aromatic, and cyclic compounds and a decrease in the fractions of methoxy phenols, acids+esters, furans, and alcohols were observed in the presence of Al-MCM-41 material. According to all results, the use of Al-MCM-41 materials as catalyst in the pyrolysis can be suggested to obtain both quality fuels and valuable chemicals.     

黄河三角洲土壤(潮土)石油类含量对小麦的影响研究

本文在分析黄河三角洲土壤石油类含量状况、通过盆栽试验研究小麦对当地土壤 (潮土 )石油类含量耐受度的基础上 ,建立物流模型 ,得出了在不受污油、落地油污染的地方土壤 (潮土 )石油类含量对小麦的不利影响在较长时间内将是微弱的基本结论。