干热河谷林地燥红土固碳特征及"新固定"碳表观稳定性

全球气候变化背景下,森林土壤固碳能力及所固定碳的稳定性受到极大关注.基于土壤密度分组和酸水解技术,对比研究了1991年营造的大叶相思(Acacia auriculiformis)林不同阶段(1991、1997、2003和2010年)土壤及其物理和生化组分中有机碳密度.结果表明,造林19 a后林地表层(0～15 cm)和亚表层(15～30 cm)土壤有机碳密度分别为1.40 kg.m-2和0.99kg.m-2.研究期内(1991～2010年)表层和亚表层土壤平均固碳速率分别为37.89 g.(m2.a)-1和16.84 g.(m2.a)-1,且土壤呈现加速固碳特征.2003年林地表层重组有机碳分配比例为71.44%,显著高于2010年(67.99%).2003年林地表层或亚表层轻组顽固性碳指数显著高于重组,但均随林龄的增加而降低,尤其是轻组顽固性碳指数.2003～2010年间燥红土"新固定"碳中57%～70%受物理保护,33%～49%为生化稳定性碳.研究揭示出干热河谷人工林燥红土具备较大的固碳能力.受物理保护碳的生化稳定性低于非保护碳,其稳定性均随林龄的增加而降低.     

“水解酸化+接触氧化”工艺在小型企业中成药废水处理中的应用

介绍了"水解酸化+接触氧化"工艺处理具有污染物浓度高、水质水量波动大等特点的某小型企业中药废水实际工程。监测数据表明该工艺处理效果稳定、可靠,出水指标达到GB 8978—1996《污水综合排放标准》医药原料药二级标准。     

模拟酸雨对烤烟叶片光合特性和叶绿素荧光参数的影响

以烤烟为供试材料,采用土培盆栽的方法研究了不同pH值的模拟酸雨(pH5.6、pH4.5、pH4.0、pH3.5、pH3.0、pH2.5、pH2.0)对烤烟叶片叶绿素含量、气体交换和叶绿素荧光参数的影响.结果表明:pH≥3.5处理的轻度酸雨对烤烟Chl.a含量影响不大,但pH≤3.5处理烤烟叶片Chl.b和总叶绿素含量显著下降.pH≤2.5模拟酸雨使烤烟叶片净光合速率(Pn)、气孔导度(Ls)、胞间CO2浓度(Ci)、叶面饱和蒸气压力亏缺(VPD)显著降低,使烤烟叶片的气孔限制值(Ls)和潜在水分利用效率(WUEi)显著升高,模拟酸雨使pH2.0处理烤烟叶片的蒸腾速率(Tr)和pH2.5处理的瞬时水分利用效率(WUE)显著降低.pH≥3.5处理的光合有效量子产量(EQY)、光合电子传递速率(ETR)和光化学猝灭(qP)与对照差异不大,但pH≤3.0处理明显降低;烤烟叶片的非光化学猝灭呈先升高后降低趋势,pH≥3.5处理的非光化学猝灭(NPQ)明显高于pH≤3.0处理.     

纳米催化剂Pd/SnO_2的制备及催化还原硝酸盐反应的调控

采用热分解法制备了SnO2载体,并用浸渍法制备了Pd/SnO2催化剂.同时,采用X射线衍射仪(XRD)、透射电镜(TEM)、扫描电镜(SEM)及BET比表面积仪等对所制载体和催化剂材料进行了分析表征.结果表明,热分解法和浸渍法都能够获得纳米材料,SnO2及Pd/SnO2的粒径均在9～10nm左右,比表面积分别达到144.99m·2g-1和147.36m·2g-1.在以甲酸为还原剂的Pd/SnO2催化还原硝酸盐体系中,在Pd与SnO2负载比为2%～7%,反应温度为20～50℃和甲酸投加量4.0～24.0mmol·L-1的条件下,催化活性为0.70～9.48mg·min-·1g-1,且催化活性随着负载比、温度和甲酸投加量的增大而增大,随着pH的升高先升后降,最佳pH为3.反应温度升高及pH降低都能够提高Pd/SnO2的选择性.甲酸-Pd/SnO2催化还原硝酸盐体系中还原反应的调控策略为:反应温度宜控制在40～50℃内,这样可同时获得较高的催化活性和选择性,温度过高对催化活性和选择性影响很小,温度过低则会同时降低催化活性和选择性;控制pH为3时,可以获得最大的催化活性及较好的选择性,pH升高会降低Pd/SnO2的催化活性和选择性,pH降低会导致催化活性迅速降低,但对选择性影响不大;甲酸与硝酸盐的物质的量比宜大于4:1,此时可以有效地抑制pH的上升,同时获得较高的催化活性和选择性,甲酸与硝酸盐的物质的量比小于4:1时,会同时降低Pd/SnO2的催化活性和选择性.     

Degradation of acid fuchsine by a modified electro-Fenton system with magnetic stirring as oxygen supplying

The current modified electro-Fenton system was designed to develop a more convenient and e cient undivided system for practical wastewater treatment. The system adopted a cathode portion that employed magnetic stirring instead of common oxygen gas di usion or gas sparging to supply oxygen gas for the electrolyte solution. Key factors influencing the cathode fabrication and activity were investigated. The degradation of acid fuchsine with a self-made graphite-polytetrafluorethylene cathode was studied using a spectrophotometer. It was found that the cathode generated hydrogen peroxide with high current e ciency and the hydrogen peroxide yield of the cathode did not decay after 10 times reuse. With the Pt anode at a ferrous ion concentration of 0.5 mmol/L, a pH of 3, and using magnetic stirring, dye decolorization could be rapidly accomplished but the destruction of benzene rings and intermediates was fairly di cult. With a Fe anode, dye degradation was more complete.     

Selective removal of 2,4-dichlorophenoxyacetic acid from water by molecularly-imprinted amino-functionalized silica gel sorbent

A molecularly-imprinted amino-functionalized sorbent for selective removal of 2,4-dichlorophenoxyacetic acid(2,4-D) was prepared by a surface imprinting technique in combination with a sol-gel process.The 2,4-D-imprinted amino-functionalized silica sorbent was characterized by FT-IR,nitrogen adsorption and static adsorption experiments.The selectivity of the sorbent was investigated by a batch competitive binding experiment using an aqueous 2,4-D and 2,4-dichlorophenol(2,4-DCP) mixture or using an aqueous 2...     

Bioaccumulation of cadmium bound to humic acid by the bivalve Meretrix meretirx Linnaeus from solute and particulate pathways

Humic acid is an important pool of heavy metals in sediments.Generally,the presence of refractory humic matter in aquatic systems would decrease the bioavailability of Cd and hence control the bioaccumulation of Cd in benthic animals.In the present work,we applied a suspending system to determine the relative importance of particulate and dissolved fractions of humic acid as Cd sources for the bivalve Meretrix meretrix and to investigate the difference of bioaccumulation characteristics of Cd adsorbed on di...     

Removal of humic acid from aqueous solution by cetylpyridinium bromide modified zeolite

Natural zeolite was modified by loading cetylpyridinium bromide (CPB) to create more e cient sites for humic acid (HA) adsorption. The natural and CPB modified zeolites were characterized with X-ray di raction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. The e ects of various experimental parameters such as contact time, initial HA concentration, solution pH and coexistent Ca2+, upon HA adsorption onto CPB modified zeolites were evaluated. The results showed that natural zeolite had negligible a nity for HA in aqueous solutions, but CPB modified zeolites exhibited high adsorption e ciency for HA. A higher CPB loading on natural zeolites exhibited a larger HA adsorption capacity. Acidic pH and coexistent Ca2+ were proved to be favorable for HA adsorption onto CPB modified zeolite. The kinetic process was well described by pseudo second-order model. The experimental isotherm data fitted well to Langmuir and Sips models. The maximum monolayer adsorption capacity of CPB modified zeolite with surfactant bilayer coverage was found to be 92.0 mg/g.     

Effect of lime application on microbial community in acidic tea orchard soils in comparison with those in wasteland and forest soils

Lime application is a conventional technology to control acidification in tea orchard soils. We investigated the e ect of lime application on soil microbial community diversity in the soils of three tea orchards, wasteland and forest. The BIOLOG data showed that both the average well color development of all carbon sources and the functional diversity index increased with the liming rate in the tea orchards and the forest, but decreased in the wasteland. The phospholipid fatty acid (PLFA) analysis showed that the structural diversity index of soil microbial community increased with the liming rate in all the tea orchards, the wasteland and the forest. Lime application also increased the soil-bacterial PLFA content in all the soils. Soil fungal and actinomycete PLFAs in the tea orchards showed an increasing trend from 0 to 3.2 g CaCO3/kg application and then a decreasing trend from 3.2 to 6.4 g CaCO3/kg application. The principal component analysis of BIOLOG and PLFA data suggested that lime application had a significant e ect on soil microbial community structure, and land use had a greater e ect on soil microbial community structure compared to lime application.     

我国14个站点降水中甲酸和乙酸浓度及对酸性的贡献

为了较全面地掌握我国大气降水中有机酸含量及其对降水酸性的贡献,于2007年全年在我国14个区域代表性较好的站点采集了降水样品,利用离子交换色谱法分析了样品中的甲酸和乙酸2种重要有机酸的浓度,对所得各站数据进行了统计分析,计算了2种酸的湿沉降通量和对降水酸性的相对贡献.观测到的14个站点甲酸和乙酸平均浓度范围分别为0.96～3.43μmol/L和0～5.13μmol/L,接近国外偏远地区观测结果,也接近我国过去短期观测结果的低端值.比较显示,偏远地区有机酸含量低于城市附近地区.估算的甲酸和乙酸湿沉降通量范围分别为0.38～4.18mmol/(m2.a)和0.06～5.87mmol/(m2.a),南方站点有机酸湿沉降通量大于北方.有机酸对降水酸性的贡献范围是0.02%～51.6%,总平均贡献为2.95%,这一结果表明,虽然我国酸雨主要是硫、氮排放造成的,但有机酸在部分地区及部分时段甚至有很显著的致酸作用,应该成为酸雨观测研究内容之一.