铁路沿线可燃重气储罐最小隔离区域划分探讨*

为保护铁路线，以某化工厂距离高铁路线最近的丙烯球罐为例，提出丙烯球罐泄漏最小隔离区域划分方法以及2种保护高铁线路方案，利用重气扩散模型和定量风险评价（QRA）软件分别进行丙烯扩散模拟、爆炸模拟，并进行危险与可操作性分析（HAZOP）和保护层分析（LOPA）。结果表明:球罐发生泄漏及火灾爆炸等事故，会给附近铁路线带来严重破坏；丙烯泄漏或球罐因周围其他设备设施或可燃物质着火而温度升高时，保护措施不足；隧道的安全可靠性要高于仅设1道防爆墙，隧道长度需覆盖最小隔离区域的可及范围，在扩散区域内也需设立普通挡墙，在极度危险情况下，需要实施高铁停开等保护措施。     

锐钛矿-金红石混合晶型TiO2降解气相苯

用溶胶-凝胶法并通过控制煅烧温度合成不同晶相比的混合晶型纳米TiO_2,在紫外光光照下降解气相苯。考察了苯初始质量浓度、紫外灯光照强度和催化剂加入量对苯去除率的影响;探究了光催化降解气相苯的动力学特征。结果表明:450℃煅烧制备的催化剂降解苯效率最高,此催化剂金红石相质量分数为6.30%;在苯初始质量浓度为74.39 mg/m~3、催化剂加入量为7 g、光照强度为2.18 klux的最佳条件下反应84 min,苯去除率达99.73%;光催化降解率与光照强度之间符合0.5级动力学特征;当催化剂加入量为3 g时,单位时间单位质量催化剂降解苯的质量最多;苯的光催化降解反应均符合一级动力学方程。     

Metabolic uncoupler, 3,3′,4′,5-tetrachlorosalicylanilide addition for sludge reduction and fouling control in a gravity-driven membrane bioreactor

• Effects of metabolic uncoupler TCS on the performances of GDMBR were evaluated. • Sludge EPS reduced and transformed into dissolved SMP when TCS was added. • Appropriate TCS increased the permeability and reduced cake layer fouling. • High dosage aggravated fouling due to compact cake layer with low bio-activity. The gravity-driven membrane bioreactor (MBR)system is promising for decentralized sewage treatment because of its low energy consumption and maintenance requirements. However, the growing sludge not only increases membrane fouling, but also augments operational complexities (sludge discharge). We added the metabolic uncoupler 3,3′,4′,5-tetrachlorosalicylanilide (TCS) to the system to deal with the mentioned issues. Based on the results, TCS addition effectively decreased sludge ATP and sludge yield (reduced by 50%). Extracellular polymeric substances (EPS; proteins and polysaccharides) decreased with the addition of TCS and were transformed into dissolved soluble microbial products (SMPs) in the bulk solution, leading to the break of sludge flocs into small fragments. Permeability was increased by more than two times, reaching 60–70 L/m²/h bar when 10–30 mg/L TCS were added, because of the reduced suspended sludge and the formation of a thin cake layer with low EPS levels. Resistance analyses confirmed that appropriate dosages of TCS primarily decreased the cake layer and hydraulically reversible resistances. Permeability decreased at high dosage (50 mg/L) due to the release of excess sludge fragments and SMP into the supernatant, with a thin but more compact fouling layer with low bioactivity developing on the membrane surface, causing higher cake layer and pore blocking resistances. Our study provides a fundamental understanding of how a metabolic uncoupler affects the sludge and bio-fouling layers at different dosages, with practical relevance for in situ sludge reduction and membrane fouling alleviation in MBR systems.     

Co-treatment of fruit and vegetable waste in sludge digesters. An analysis of the relationship among bio-methane generation,process stability and digestate phytotoxicity

The co-digestion of a variable amount of fruit and vegetable waste in a waste mixed sludge digester was investigated using a pilot scale apparatus. The organic loading rate (OLR) was increased from 1.46 kg VS/m³ day to 2.8 kg VS/m³ day. The hydraulic retention time was reduced from 14 days to about 10 days. Specific bio-methane production increased from about 90 NL/kg VS to the maximum value of about 430 NL/kg VS when OLR was increased from 1.46 kg VS/m³ day to 2.1 kg VS/m³ day. A higher OLR caused an excessive reduction in the hydraulic retention time, enhancing microorganism wash out. Process stability evaluated by the total volatile fatty acids concentration (mg/l) to the alkalinity buffer capacity (eq. mg/l CaCO₃) ratio (i.e. FOS/TAC) criterion was <0.1 indicating high stability for OLR <2.46 kg VS/m³ day. For higher OLR, FOS/TAC increased rapidly. Residual phytotoxicty of the digestate evaluated by the germination index (GI) (%) was quite constant for OLR < 2.46 kg VS/m³ day, which is lower than the 60% limit, indicating an acceptable toxicity level for crops. For OLR > 2.46 kg VS/m³ day, GI decreased rapidly. This corresponding trend between FOS/TAC and GI was further investigated by the definition of the GI ratio (GIR) parameter. Comparison between GIR and FOS/TAC suggests that GI could be a suitable criterion for evaluating process stability.     

农药混配制剂环境风险评估现状与展望

本文综述了欧洲和美国农药混配制剂的环境风险评估方法。详细介绍了欧洲食品安全局(EFSA)评估体系中的2种方法,即,基础的"整体测试法"和近年来提倡的"基于组分的方法"。"基于组分的方法"的特点是以浓度加和模型(CA模型)作为默认假设进行初级评估,以独立作用模型(IA模型)等作为高级评估手段的农药混配制剂环境风险评估方法。此外,本文还介绍了模型偏差率(MDR)、毒性相似度及毒力单元(TU)等概念以及混配制剂风险评估流程。本文的目的旨在为建立我国农药混配制剂的环境风险评估方法体系提供参考。     

Influence of dissolved humic substances on the mass transfer of organic compounds across the air-water interface

The effect of dissolved humic substances (DHS) on the rate of water-gas exchange of two volatile organic compounds was studied under various conditions of agitation intensity, solution pH and ionic strength. Mass-transfer coefficients were determined from the rate of depletion of model compounds from an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution (dynamic system). Under these conditions, the overall transfer rate is controlled by the mass-transfer resistance on the water side of the water-gas interface. The experimental results show that the presence of DHS hinders the transport of the organic molecules from the water into the gas phase under all investigated conditions. Mass-transfer coefficients were significantly reduced even by low, environmentally relevant concentrations of DHS. The retardation effect increased with increasing DHS concentration. The magnitude of the retardation effect on water-gas exchange was compared for Suwannee River fulvic and humic acids, a commercially available leonardite humic acid and two synthetic surfactants. The observed results are in accordance with the concept of hydrodynamic effects. Surface pressure forces due to surface film formation change the hydrodynamic characteristics of water motion at the water-air interface and thus impede surface renewal.     

层燃螺旋炉排焚烧技术处理含油污泥研究

通过对几种含油污泥无害化处理技术的比选,分析不同处理技术物耗、能耗情况,优选出经济有效的含油污泥焚烧技术,结合新疆油田含油污泥的特点,采用层燃螺旋炉排焚烧技术,利用其燃烧热能生产蒸汽用于原油生产,采用余热吸收急冷与碱液半干法除酸技术,有效控制了二次污染;采用布袋除尘与烟尘固化技术确保了烟气达标排放。年节省成本支出3095.88万元。     

1株异养硝化-好氧反硝化细菌DK1的分离鉴定及其脱氮特性

从某反应器活性污泥中分离筛选出1株假单胞菌属(Pseudomonas sp.)细菌,命名为DK1,并对该菌进行脱氮特性研究.在以葡萄糖为碳源,C/N量比为5时,分别以NaNO_3和NaNO_2为氮源,二者的好氧反硝化速率为4.09 mg·(L·h)-1和4.43mg·(L·h)~(-1).以二者同时为氮源脱氮率为100%;此外,菌株DK1具有异养硝化性能,NH_4~+-N平均去除速率为2.32mg·(L·h)-1.缺氧时以NO_2~--N为氮源菌株DK1可将一系列梯度浓度NO_2~--N(约100~300 mg·L-1)在36 h内降为0.当NO_3~--N和NO_2~--N同时存在时,菌株DK1会优先利用NO_3~--N进行反硝化.同时该菌株还具有同步硝化反硝化(SND)性能,可同时去除NH_4~+-N、NO_2~--N或NH_4~+-N、NO_3~--N,30 h内脱氮率分别达95.06%和94.69%.相同时间内在NH_4~+-N、NO_2~--N和NO_3~--N三者均存在时,脱氮效果最佳,达100%.菌株DK1的高效SND及反硝化性能表明其在处理含氮废水方面有一定的潜力和应用价值.     

成都市污染边界层高度的演变特征分析

基于2014年1月21日至2月5日成都市人民南路四段逐时PM_(2.5)质量浓度、大气能见度资料以及同期Mie散射激光雷达探测数据,遵循消光系数与细颗粒物质量浓度之间的关系,探讨污染边界层高度的演变特征。结果表明:污染时段内的污染边界层高度偏低,平均为221m;污染边界层高度与地面PM_(2.5)浓度的变化具有明显相关性,但污染边界层高度改变在前,地面PM_(2.5)浓度响应在后;污染边界层高度的日变化表现为单峰单谷型,峰值和谷值分别出现在08:00时和14:00时前后。     

喀斯特常绿与落叶阔叶混交林过去50年来的碳循环模拟

通过对Forest-DNDC模型的植被和土壤参数本地化校准,以气象插值数据为输入,模拟了贵州省普定县高原型喀斯特次生常绿与落叶阔叶混交林1965~2014年的土壤、植被和生态系统碳循环特征。结果表明,与冷模拟和实测值相比,参数本地化校准后的模型能更准确地模拟春、秋、冬3个季节的土壤呼吸动态,而模拟的夏季土壤呼吸偏小;但统计检验指出,参数修订后的Forest-DNDC模型能够较好地模拟喀斯特森林土壤呼吸,降低了模拟误差,可用于喀斯特常绿与落叶阔叶混交林碳动态的模拟。进一步分析发现,1965~2014年喀斯特森林的碳通量除模拟早期的前3~4年急剧增加之外,随后总初级生产力(GPP)保持相对稳定,植物呼吸(Rplant)和生态系统呼吸(R_(ecosystem))随着森林发育而增加,土壤呼吸(R_(soil))减少,植被净初级生产力(NPP)呈迅速减小趋势;净生态系统碳交换量(NEE)亦较迅速下降,在2013年达到最低值-0.17 t C/ha,喀斯特森林由碳汇变为弱碳源。相关分析表明,年均温度和年降水对喀斯特常绿与落叶阔叶混交林的GPP和R_(soil)没有显著影响,但却显著影响NPP、R_(plant)、R_(ecosystem)和NEE。