几种催化剂对垃圾渗滤液臭氧氧化效能的影响

通过制备以γ-Al2O3为载体的铬、镉、钴、铜、镍5种催化剂,研究了催化剂负载率对臭氧吸收率的影响以及臭氧催化氧化垃圾渗滤液时水质的变化情况.试验结果表明,钴在γ-Al2O3载体上具有较强的负载性,在催化剂与COD质量比为5,O3与COD质量比分别为0.11、0.15、0.26时,镉催化剂能使臭氧吸收率提高,而铬催化剂则不利于臭氧的吸收;固定催化剂与COD质量比为5,当O3与COD质量比为0.15时,铜催化剂可使COD去除率提高20.2%;同样固定催化剂与COD质量比为5,当O3与COD质量比为0.26时,镍催化剂有利于氨氮的去除,可使氨氮去除率提高20.7%;臭氧催化氧化时,臭氧的最佳投加量可按O3与COD质量比为0.125考虑.     

Minimum ignition energy theoretical model for flammable gas based on flame propagation layer by layer

To achieve the rapid prediction of minimum ignition energy (MIE) for premixed gases with wide-span equivalence ratios, a theoretical model is developed based on the proposed idea of flame propagation layer by layer. The validity and high accuracy of this model in predicting MIE have been corroborated against experimental data (from literature) and traditional models. In comparison, this model is mainly applicable to uniform premixed flammable mixtures, and the ignition source needs to be regarded as a punctiform energy source. Nevertheless, this model can exhibit higher accuracy (up to 90%) than traditional models when applied to premixed gases with wide-span equivalence ratios, such as C₃H₈-air mixtures with 0.7–1.5 equivalence ratios, CH₄-air mixtures with 0.7–1.25 equivalence ratios, H₂-air mixtures with 0.6–3.15 equivalence ratios et al. Further, the model parameters have been pre-determined using a 20 L spherical closed explosion setup with a high-speed camera, and then the MIE of common flammable gases (CH₄, C₂H₆, C₃H₈, C₄H₁₀, C₂H₄, C₃H₆, C₂H₂, C₃H₄, C₂H₆O, CO and H₂) under stoichiometric or wide-span equivalence ratios has been calculated. Eventually, the influences of model parameters on MIE have been discussed. Results show that MIE is the sum of the energy required for flame propagation during ignition. The increase in exothermic and heat transfer efficiency for fuel molecules can reduce MIE, whereas prolonging the flame induction period can increase MIE.     

Precise sex ratios manifested by several encyrtid parasitoids (Hymenoptera: Encyrtidae) of brown soft scale, <Emphasis Type="Italic">Coccus hesperidum</Emphasis> L. (Hemiptera: Coccidae)

We examined whether several facultatively gregarious encyrtid (Hymenoptera: Encyrtidae) endoparasitoids of brown soft scale, Coccus hesperidum L., manifest precise sex allocation under field conditions. Metaphycus luteolus (Timberlake), Metaphycus angustifrons (Compere), Metaphycus stanleyi (Compere), and Microterys nietneri (Motshulsky) evince brood sex ratios that are female-biased and extremely precise (low variance in the number of sons per host). Typically, this sex allocation pattern is attributed to extreme local mate competition (LMC) in which only one foundress exploits a patch of hosts and mating occurs mostly between her offspring. However, such a pattern of sex allocation was not detected for Metaphycus helvolus (Compere). Also, a large proportion of the broods in all five species contained only daughters; thus, an excess of male-only broods was expected if unmated females (i.e., females that can produce only sons) contribute offspring before mating. All-male broods were rare in our samples. This finding coupled with the life history characteristics of these wasps, such as the exploitation of aggregated hosts and the long life span and mobility of males, suggest that nonlocal mating is frequent. Our empirical work suggests that it is advantageous to allocate precise sex ratios in cases in which mating opportunities for males are not restricted to their natal host and/or when multiple foundresses exploit large patches of hosts. Limited theoretical work also supports this prediction but more detailed studies of this taxon’s mating structure and other life history characteristics are necessary to understand their sex allocation decisions.     

北京市大气中BTEX工作日与非工作日的浓度变化

对2006年北京市大气中苯系物(BTEX)在工作日和非工作日的浓度变化进行研究.结果表明,BTEX在非工作日的平均浓度比工作日低4.8%,其中"五一"和"十一"假期BTEX的浓度分别为54%和13.2%.BTEX在非工作日浓度降低的主要原因是因为非工作日机动车使用量的减少.在工作日BTEX浓度峰值与上下班交通高峰有关,而在非工作日浓度从下午到夜间维持在一个较高浓度.BTEX各物质之间的比值在工作日和非工作日差别不大,但是各物质之间在非工作日的相关性比工作日好.苯和甲苯在工作日和非工作日都具有较好的相关性,乙苯和二甲苯之间在非工作日的相关性比工作日高.     

国Ⅳ柴油机颗粒物与颗粒态多环芳烃排放特征

针对一台轻型柴油机,采用国Ⅳ柴油,在不使用和使用后处理装置的条件下,进行ESC循环工况(分别记为ESC-0、ESC-DP)和ETC循环工况(分别记为ETC-0、ETC-DP)下的发动机台架测试.每次测试用一对滤膜采集颗粒物,采样前后分别称重以确定颗粒物质量,进而计算排放因子.用气相色谱-质谱联机(GC-MS)分别分析每张滤膜上颗粒物的多环芳烃(PAHs)组分.ESC-0、ESC-DP、ETC-0、ETC-DP的颗粒物排放因子分别为0.12,0.05,0.48,0.16 g/(kW·h);相应的PAHs排放因子分别为69,35,174,76 μg/(kW·h).后处理分别使颗粒物和PAHs减排56%~68%和49%~56%.总PAHs中,三环PAHs占比重最大(64%±9%).PHE在总PAHs中占比重最大(54%±9%).PAHs的分布与其物理化学特性、柴油中的芳烃含量有关.PAHs特征比值FA/(FA+PY)为0.37~0.51.     

COD/N与pH值对短程硝化反硝化过程中N2O产生的影响

利用SBR反应器,通过投加乙醇控制COD/N为0、1.5、3、4.5,调节pH值分别在6、7、8,反硝化初始投加NO2--N为30mg/L,考察了缺氧条件下COD/N与pH值对短程硝化反硝化过程中N2O产量的影响.结果表明:低COD/N可以造成N2O持续较高的逸出,N2O最大产生量为2.35mg/L;低pH值条件下增加了N2O的积累,pH值在6时的N2O积累量是pH在7、8时的800倍;高COD/N和高pH值下的N2O产生速率最小,而当pH=6,COD/N=0时,N2O产生速率最大,为2.35×10-3mgN/(mgMLSS?L?h).其原因是:N2O还原酶争夺电子的能力较弱,充足的电子供体有利于N2O的还原;低pH值可影响微生物的代谢,且在H+存在时产生的游离亚硝酸(HNO2)对N2O还原酶具有抑制作用.充足的碳源和碱性条件,是降低短程硝化反硝化过程中N2O产量的关键因素.     

6种苯系物对球等鞭金藻和新月菱形藻的生长抑制

海洋环境中苯系物污染主要来源于海洋溢油事故以及沿海石油化工企业的废水排放。为探究苯系物对海洋微藻的毒性作用,选择球等鞭金藻和新月菱形藻作为受试生物,分别考察了苯、甲苯、乙基苯、邻-二甲苯、间-二甲苯和对-二甲苯6种苯系物对2种海洋微藻生长的影响。结果表明,在0.25~64.0 mg·L-1暴露浓度下,6种苯系物对2种微藻生长具有显著的抑制作用,随着暴露浓度的升高,抑制作用明显增强。苯、甲苯、乙基苯、邻-二甲苯、间-二甲苯、对-二甲苯对球等鞭金藻的24 h的半数效应浓度(24 h-EC50)分别为:17.07、12.88、7.58、0.55、0.36、0.27 mg·L-1;对新月菱形藻的24 h-EC50值分别为:1.03、0.68、0.46、0.40、0.42、0.38 mg·L-1。上述研究结果为确定苯系物海洋环境质量标准、保护海洋生态环境提供了基础数据。     

典型平原河网区水体富营养化特征、成因分析及控制对策研究

本文以嘉兴市北部湖荡区为典型研究区域,通过现场调研、来源分析等,揭示了平原河网区水体富营养化状态,明确了水污染主要成因,并提出控制对策.研究结果显示,北部湖荡区总磷、高锰酸盐指数、五日生化需氧量、化学需氧量、总氮、氨氮等各污染物含量呈现显著的时空分布特征,西部片区水质较东部片区差,5月水质较9月差(总磷除外);富营养化...     

双子地震P波谱比在地震短期预报中的应用研究

应用法国地震学家G.Poup inet等关于双子地震的有关理论,对云南地震台网数字地震资料开展应用研究,通过基线校正、数字滤波、波形对比等方法获得8对3级双子地震和武定地震易门台7对双子地震。对以上双子地震取起始3秒P波作富氏谱分析后进行谱比对数的斜率拟合。结果显示,由发生在6.5级姚安地震前7个月之内与之外时段的地震构成的双子地震,其P波谱比对数斜率绝对值都达到0.030以上,明显高于均由震前7个月之外发生的地震构成的双子地震谱比对数斜率;在距主震2°范围以内的台站可观测到双子波发生的变化。常熟台双子地震P波谱比对数斜率时间进程在南黄海地震发生之前也存在这一现象,但出现异常的时间扩大到9个月之内。     

气相色谱法测定环境标准样品中7种苯系物

氦气作载气,选用DB—WAX毛细管色谱柱,优化柱温、柱流量、进样口温度和检测器温度等色谱参数,实现7种苯系物的快速分析。实验结果表明,通过优化色谱条件,7种苯系物在5.3m in内得到了良好的分离,标准样品的测定均值最大相对误差-1.0%,最大相对标准偏差2.5%。