Characterization of cadmium uptake,translocation, and distribution in young seedlings of two hot pepper cultivars that differ in fruit cadmium concentration

The reasons why some cultivars of hot pepper (Capsicum annuum L.) accumulate low levels of Cd are poorly understood. We aimed to compare the characteristics of Cd uptake and translocation in low-Cd and high-Cd hot pepper cultivars by determining the subcellular locations and chemical forms of Cd, and its distribution among different plant organs. We conducted a hydroponic experiment to investigate the subcellular distribution and chemical forms of Cd in roots, stems, and leaves of a low-Cd (Yeshengchaotianjiao, YCT) and a high-Cd cultivar (Jinfuzaohuangjiao, JFZ). The results showed that the concentrations of Cd in almost all subcellular fractions of roots, and in all chemical forms in roots, were higher in YCT than in JFZ. Compared with YCT, JFZ had higher Cd concentrations in almost all subcellular fractions of stems and leaves, and higher Cd concentrations in almost all chemical forms in stems and leaves. Additionally, YCT had significantly higher total Cd accumulation but a lower Cd translocation rate compared with JFZ. In general, the results presented in this study revealed that root-to-shoot Cd translocation via the xylem is the key physiological processes determining the Cd accumulation level in stems and leaves of hot pepper plants. Immobilization of Cd by the cell walls of different organs is important in Cd detoxification and limiting the symplastic movement of Cd.     

Translocation analysis and safety assessment in two water spinach cultivars with distinctive shoot Cd and Pb concentrations

A pot experiment was conducted to investigate the translocation of cadmium (Cd) and lead (Pb) and assess the safety of edible parts in two cultivars of water spinach (Ipomoea aquatica Forsk.) contrasting in shoot Cd and Pb concentrations. A low-Cd-Pb cultivar (QLQ) and a high-Cd-Pb cultivar (T308) were grown in five soils with different concentrations of Cd and Pb. The results showed that QLQ had lower Cd and Pb concentrations in stems and leaves and higher root Cd concentration than T308 did. Root Pb concentration of T308 dramatically increased with increasing soil Pb concentration and was higher than that of QLQ in the highest Pb treatment. The root-to-stem Cd translocation ability in T308 was 2.3–3.0-fold higher than that in QLQ. Nevertheless, there was no significant difference in root-to-stem Pb translocation between QLQ and T308. The bioconcentration factors (BCFs) for Cd and Pb in the two cultivars remained stable in different Cd or Pb treatments, which were attributable to the homeostatic control mechanisms of Cd and Pb in water spinach.     

流向变换反应器中Pd/Zr-Mn-O/载体催化剂对甲苯的催化燃烧

在流向变换催化燃烧反应体系中,通过操作参数(甲苯浓度、空速及切换周期)对热波形状与特征参数(波峰温度、平均温度和移动速度)影响的考察,结果表明,较佳的操作参数为:甲苯浓度800～3 200 mg/m3,空速2 000～12 000h-1,切换周期2～10 min,空速和甲苯浓度对热波移动速度的影响较大,热波波峰温度和反应器平均温度随着甲苯浓度的增加而增加,随着切换周期的缩短而升高,随着空速的增加先升高后降低,与固定床装置相比,在流向变换装置中催化剂的活性更高,甲苯去除率在96.5%以上。     

等离子体协同MnO_x/SBA-15催化降解正己醛的研究

采用浸渍法制备了MnOx/SBA-15催化剂,利用BET、XRD和SEM等对催化剂进行表征。考察了介质阻挡放电等离子体协同MnOx/SBA-15催化剂对正己醛的降解性能。结果显示,负载MnOx后的SBA-15仍然保持介孔结构,且MnOx均匀地分散在SBA-15中;等离子体与催化剂表现出较好的协同作用,干燥条件下7.5 kV的放电电压结合10%MnOx/SBA-15时降解效果最佳,正己醛去除率达99%;相比干燥条件,相对湿度低于20%时正己醛去除率变化不明显,但高于20%时催化效果明显下降;该催化剂具有很强的O3分解能力,O3在催化剂表面的分解不仅促进了正己醛的氧化,同时也提高了CO2的选择性。     

试论研究生文检课教学改革

研究生文献检索课教学的重点应放在培养学生的独立思维能力和自主创新能力上。从信息资源评价、竞争情报、科技查新、信息伦理等方面对研究生文检课教学内容进行了探讨,目的在于提高教学质量和教学效果,为多出科技成果、多出创新型人才服务。     

载体结构对Co/MgO-Al2O3催化剂催化C2H6/CO2反应性能的影响

采用共沉淀-浸渍法制备了不同载体结构的Co/Al₂O₃、Co/MgO_（25）-Al₂O_3（75） （Co/M₁A₃-Spinel）、Co/MgO_（75）-Al₂O_3（25） （Co/M₃A₁-Solid）和Co/MgO催化剂,用于CO₂氧化乙烷脱氢（ODEC）和乙烷干重整（DRE）反应.XRD、Raman、H₂-TPR、XPS表征结果表明,载体结构显著影响催化剂上Co物种的落位、结构和还原性能.Co³⁺和Co²⁺在C₂H₆/CO₂反应气氛中可相互转化,促进C₂H₆和CO₂活化;尖晶石结构中的Co物种比固溶体中的Co物种可还原性强,在高温ODEC反应条件下,催化剂表面的Co物种会被还原成Co⁰,协同Co³⁺/Co²⁺导致C—C键和/或CC键断裂,使得反应路径向DRE转变.MgO基固溶体结构中Co物种与载体相互作用更强,在高温ODEC反应中避免了被大量还原为低价态的Co⁰,ODEC反应可稳定进行.     

TiO2改性银铝催化剂选择性丙烯还原NOx硫失活机制研究

采用溶胶凝胶法制备4%Ag/Al2O3、4%Ag/10%TiO2-Al2O3催化剂.利用N2物理吸附、氮氧化物/二氧化硫程序升温脱附(NOx/SO2-TPD)以及普通/原位漫反射傅里叶变换红外光谱(FT-IR/DRIFTs)对催化剂进行表征,并探讨催化剂在含硫气氛前后选择性还原NOx活性的变化及中毒机理.结果表明在4%Ag/Al2O3催化剂中掺杂10%TiO2能提高催化剂的中低温活性以及在400℃下抗SO2中毒的能力.TiO2引入后可促进甲酸盐物种的形成从而有利于低温反应的进行;SO2与NO在同一活性位上出现的竞争吸附以及活性组分Ag的硫酸化是4%Ag/Al2O3催化剂失活的重要原因;TiO2的加入能促进NO在催化剂表面的吸附并能减弱其对SO2的吸附,同时能有效抑制活性组分Ag的硫酸化,从而提高催化剂的抗硫性.     

湖南香花岭矿区地下水的水文地球化学特征及形成机制

湖南香花岭是我国有色、稀有金属的重要生产基地,其环境已经受到矿山活动的强烈影响,对矿区地下水的水化学特征研究对矿区污染分布调查和环境治理具有现实意义.本文通过主成分分析、相关性分析和离子比例系数分析对湖南香花岭地区的地下水的水化学组分进行了统计与分析,利用phreeqc模拟软件及重金属浓度分布图来探究研究区地下水水文地球化学特征形成机制.结果表明:人为活动特别是采矿活动和水岩相互作用一起影响了矿区地下水的化学成分;碳酸盐岩与非碳酸盐岩交界地区岩溶溶蚀作用表现更为明显;重金属元素经过碳酸盐岩分布区时受到拦截,不易进入地下水中.     

Study of elemental distribution in soil on the loess plateau of China

Instrument neutron activation analysis (INAA) has been employed in this study to determine 32 elements in soil on the loess plateau. The preliminary results suggest that geochemical characteristics of elements in the soil mainly retained those in the parent materials (loess). It has been found that fractional deposition among grain sizes in the process of loess transportation as well as the bioclimate in which the soil developed are main factors affecting the regional variations of elemental distribution in soil on the plateau. Contour maps of element concentrations plotted from the trend analyses exhibit the major patterns of the distributions and variations on the plateau. Furthermore, the study also provides evidence for the aeolian theory of the loess transportation in China.