表面活性剂对苯系物在静水面挥发的影响

以苯、甲苯和乙苯为苯系物(BTEX)的目标化合物 ,研究了十二烷基苯磺酸钠(SDBS)、十六烷基三甲基溴化铵(CTMAB)和月桂醇聚氧乙烯(4)醚(Brij30)共存时,BTEX在静水面的挥发及机理 ,为复合污染的水体中表面活性剂对有机物挥发的影响提供理论依据 .结果表明 ,在所测浓度范围内 ,表面活性剂浓度大于临界胶束浓度 (CMC)且分别达到1000mg/L、2000mg/L和3000mg/L 时 ,乙苯、甲苯和苯的挥发速率分别开始变小 ,挥发半衰期值(t_1/2)变大 .胶束的形成 ,减小了BTEX在液膜和液相中的浓度比(α) ,使BTEX在静水面的挥发速率降低 .CTMAB和Brij30对苯系物在静水面挥发速率的抑制作用明显强于SDBS .相同表面活性剂对BTEX挥发速率的抑制作用与BTEX的辛醇 水分配系数 (Kow)和亨利系数(H)均呈正相关 .     

炼焦过程中单环芳烃排放及源特征

通过不锈钢采样罐采样和液氮预浓缩/气相色谱/质谱系统分析,研究我国山西某地的土法炼焦和机械炼焦生产过程中单环芳烃(MAHs)的排放情况.炼焦过程MAHs以苯、甲苯、(间+对)-二甲苯为主要成分,苯和总MAHs浓度在土法炼焦烟气中最高达3421.0μg/m3和4865.9μg/m³,在机械炼焦无组织排放气体和烟气中分别为548.7μg/m³、1054.8μg/m³和1376.4μg/m³、1819.4μg/m³.焦炭生产过程中MAHs浓度变化显著:土法炼焦过程MAHs前期释放浓度高于后期;机械炼焦无组织排放MAHs在装煤和出焦时明显升高;而机械炼焦烟气中则是装煤时最高,出焦时最低.苯、甲苯、乙苯和二甲苯(BTEX)散点图和相关性分析显示机械炼焦释放MAHs主要来自煤的高温分解,而土法炼焦中MAHs释放则可能除焦煤不完全燃烧释放外还受别的因素影响.苯/甲苯/乙苯/二甲苯比值(B/T/E/X)特别是苯/乙苯(B/E)值显示炼焦释放的MAHs具有不同于其它来源的特征.     

空气中苯系物测定方法的比较

主要讨论了用活性炭吸附,二硫化碳解析气标中的苯系物,比较工作曲线和标准曲线法的差异。其中苯乙烯在两者中的差异较大,用工作曲线更准确。     

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。     

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。     

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.     

北京市道路空气中挥发性有机物时空分布规律

为研究城市交通道路空气中挥发性有机化合物(VOCs)的污染状况、变化规律和不同道路类型的浓度特点,于2008年5月—2009年7月对北京市3种典型道路(街道峡谷、交叉道路和开阔道路)进行空气质量监测. 采用气相色谱法测定道路空气中非甲烷烃(NMHCs)、苯系物(苯、甲苯和二甲苯)的质量浓度. 结果表明:北京市道路空气中挥发性有机化合物污染比较严重,其中ρ(NMHCs)日均值为1.0～3.3 mg/m3,ρ(苯系物)日均值为8.8～80.0 μg/m3. 污染物浓度日变化多呈现双峰型. 选取1,4,7和10月为不同季节的代表月份,7月的ρ(NMHCs)和ρ(苯系物)均最高,10月最低. 3种典型道路中,街道峡谷的污染物质量浓度高于另外2种道路. 道路附近的挥发性有机物质量浓度主要受到机动车排放、气象条件和地形条件等的影响.      

2种统计方法在一次实验室间比对中的应用比较

比较了稳健统计法和误差系数法在水中苯系物实验室间比对结果中的应用,分别采用两种方法对比对结果进行了分析,探讨了两种统计方法的差异和适用范围。结果显示,两种方法对此次比对结果的分析结论基本一致,在实际应用中应跟据实验室间比对的目的和样品特点选择合适的统计方法。     

Depleted uranium mobility and fractionation in contaminated soil (Southern Serbia)

GOAL, SCOPE AND BACKGROUND: During the Balkan conflict in 1999, soil in contaminated areas was enriched in depleted uranium (DU) isotopic signature, relative to the in-situ natural uranium present. After the military activities, most of kinetic DU penetrators or their fragments remained buried in the ground in certain geomorphological and geochemical environments exposed to local weathering conditions. The contamination distribution, mobility and/or fixation of DU in the contaminated soil profile at one hot spot were the subject of our study. The results should disclose what happened with released DU corrosion products in three years elapsed, given the scope of their geochemical fractionation, and mark out the most probable host substrates in investigated soil type. METHODS: Gamma-spectrometric analysis of soil samples taken in the DU penetrator impact-zone was done to obtain present contamination levels. Set of samples is subjected to five-step and three-step sequential extraction procedures, specifically selective to different physical/chemical associations in soil. The stable elements are determined in extracts by the atomic absorption spectroscopy. After the ion-exchange based uranium separation procedure, alpha-spectrometric analysis of obtained fractions was done and DU distribution in five extraction phases found from 235U/238U and 234U/238U isotopic ratios. RESULTS: Depleted uranium concentration falls down to the 1% of the initial value, at approximately 150 mm distance to the source. Carbonates and iron/manganese hydrous oxides are indicated as the most probable substrates for depleted uranium in the characterized soil type. Therefore, in the highly contaminated soil samples, depleted uranium is still weakly bonded and easy exchangeable. The significant levels of organic-bonded depleted uranium are found in surface soil only. DISCUSSION: Dependence of the fractionation on the contamination levels is evident. Samples with higher DU contents have shown a longer maintenance in the exchangeable phases, probably because adsorption/desorption mass transfer through the medium was not very fast. Organic-bonded, depleted uranium is present in surface soil samples due to its higher humus content. Considering geochemical composition of investigated soil, the indicating chemical associations as substrates are in agreement with some considerations based on the results for low-level waste unsaturated zones. CONCLUSIONS: The soil contamination with depleted uranium in investigated area is still 'spot' type and not widespread. Dependence of the fractionation on the contamination levels and presence of weakly bonded, depleted uranium in the hot spots areas is evident. RECOMMENDATIONS AND PERSPECTIVES: A detailed study may be undertaken with suitable extractive reagents to define a bio-available fraction of depleted uranium in soil. The comparison of results for different soil types investigated by the same methodology may be useful. An applied combination of physical/chemical procedures and analysis may help in the decision making on the remediation strategy for sites contaminated with depleted uranium used in military operations.