Modelling accidental releases of dangerous gases into the lower troposphere from mobile sources

The article reports the results of different methods of modelling releases and dispersion of dangerous gases or vapours in cases of major accidents from road and rail transportation in urban zones. Transport accidents of dangerous substances are increasingly frequent and can cause serious injuries in densely inhabited areas or pollution of the environment. For quantitative risk assessment and mitigation planning, consequence modelling is necessary.

The modelling of dangerous substance dispersion by standard methods does not fully represent the behaviour of toxic or flammable clouds in obstructed areas such as street canyons. Therefore the predictions from common software packages as ALOHA, EFFECTS, TerEx should be augmented with computational fluid dynamics (CFD) models or physical modelling in aerodynamic tunnels, and further studies are planned to do this.

The goal of this article is to present the results of the first approach of modelling using these standard methods and to demonstrate the importance of the next development stage in the area of transport accident modelling of releases and dispersions of dangerous substances in urban zones in cases of major accident or terrorist attacks.     

Multiple batch extraction test to estimate contaminant release parameters using a Bayesian approach

Industrial activities produce vast amounts of weakly contaminated materials which are commonly reused as filling materials on natural ground. There is a strong demand to define guidelines for the application of these materials, to estimate the leaching potential of contaminants from the materials, and to assess the potential hazard for groundwater pollution. We present a multiple batch experiment, where measurements of liquid-phase concentrations at varying liquid/solid ratios are used to estimate the total mass of contaminant that can be extracted from a contaminated material with a mild extractant like water. Furthermore, the experiment yields estimates of the isotherm describing the partitioning of the contaminant between the solid and liquid phases, and a concentration that might be expected under soil hydraulic conditions representative for the field situation. Model parameters are estimated from liquid-phase concentrations within a Bayesian framework by applying the Shuffled Complex Evolution Metropolis Algorithm (SCEM-UA), an efficient Markov Chain Monte Carlo sampler. A sensitivity analysis and inversions of synthetically generated data corrupted with noise show the general suitability of the proposed method. An uncertainty analysis for model parameters and model predictions shows the expected accuracy of the estimates. An application to concentration measurements obtained from a multiple batch extraction test illustrates the applicability of the approach for a real situation.     

土壤污染物的释放速率及阻隔措施的研究

本文测定了硝基苯,苯胺,萘和苯酚从土壤向大气释放的速度,这些污染物一开始都有较高的释放速率,几天后污染物的释放速率下降。清洁的粘土和水泥板覆盖在污染的土地上能有效地防止污染物向大气释放,可用于土壤的修复。     

三峡库区消落带下部区域土壤氮磷释放规律模拟实验研究

三峡库区消落带形成后其下部区域（145~155 m）由于长期处于淹没状态,其表层土壤将类似底泥状态,研究选择嘉陵江江底沉积物模拟其在好氧及厌氧淹水条件下N、P向上覆水体的释放规律。结果表明：土壤处于淹水期间,均向上覆水释放N、P,其中好氧状态下上覆水中TN以硝态氮为主,厌氧环境下上覆水中TN以氨氮形式为主;淹水前期,N、P释放速率均较快,随时间增加逐渐减缓,且在厌氧环境下TP释放能力较好氧环境强。好氧淹水中曝气量对上覆水中TN平衡浓度无显著影响,但对氨氮、硝态氮释放过程有影响,从而影响TN浓度变化;底泥状土壤落干过程对N素释放有正影响,对P素释放有负影响;在短暂的落干期间,如果进行农业利用,将增加库区水环境污染和水体富营养化的风险.     

红枫湖沉积物内源磷释放通量估算方法的对比研究

湖泊沉积物内源磷是湖泊水体磷的重要来源,但目前对内源磷释放通量的科学估算缺乏定量研究。本文以贵州红枫湖为研究对象,对比研究了野外调查分析法、模拟实验法和扩散模型法等3种估算方法下的红枫湖沉积物内源磷释放通量。结果表明,野外调查分析法可宏观获取水体污染物来源的概况,但对采样点布设、采样频次和周期等要求较高,估算结果往往存在较大偏差和不确定性;模拟实验法可粗略获得沉积物磷释放通量,但由于取样和实验培养过程破坏了沉积物的物理化学结构,估算结果难以精确;扩散模型法可定量估算沉积物磷释放通量,但须与沉积物-水界面高分辨率观测数据相结合才能使结果可靠。红枫湖沉积物内源磷输入对水体磷污染的贡献较高(25.7%~46%),因此在富营养化治理过程中,一方面应继续强化外源污染治理,另一方面亟待加强对沉积物内源磷释放的有效控制。     

污染沉积物中重金属的释放及其动力学

研究了广州城市水体污染沉积物在不同pH条件下释放重金属的能力以及酸性条件下重金属的释放动力学。研究结果表明,重金属从污染沉积物中的释放主要是在酸性(pH<4)条件下发生,并且释放率随pH的升高而迅速降低。重金属的释放顺序大致为Cu≈Zn≈Ni>Pb。重金属的释放动力学过程可分为两个阶段,第一阶段一般认为是重金属从沉积物表面的快速解吸过程,第二阶段则可能是重金属缓慢地从沉积物内部微孔向溶液的扩散过程。释放动力学过程可以用Elovich方程和双常数速率方程(Freundlich修正式)较好地描述。     

环境条件变化对太湖沉积物磷释放的影响

本文系统研究了环境条件变化对太湖沉积物磷释放的影响，结果表明：温度、ＰＨ、氧化还原条件对沉积物磷释放有很大影响，获得了在不同环境条件下磷释放的方程，结果还表明，厌氧下（ＤＯ〈１．０ｍｇ．ｌ＾－１）沉积物磷的最大释放量明显高于好氧条件（ＤＯ〉８．０ｍｇ．ｌ＾－１），其释放速率分别为３．１４μｇ．ｇ＾－１．ｄ＾－１和２．７５μｇ＾－１．ｄ＾－１，相应的动力学方程可表示为ＣＰ＝Ａｅ＾ｂ／ｔ，观察到藻与沉     

模拟酸雨对森林红壤中铝的溶出及不同土层酸度变化的影响

为进一步探明酸沉降对森林红壤及生态环境的影响，模拟长沙地区降水酸度及离子组成，采用浸泡试验对两种森林红壤活性铝的释出及土壤理化性质的变化进行了研究。结果表明，模拟酸雨浸泡初期，土壤活性铝的释出量随浸泡次数的增加而增加，原始土壤pH值愈低，活性铝释出愈多；强酸度、高离子浓度（AR4）模拟酸雨对土壤中活性铝的溶出量远大于基础酸雨（AR3）及弱酸、低离子浓度酸雨（AR2）和对照酸雨（AR1）。模拟酸雨酸度愈大，对土壤pH值的影响愈明显，不同土层间，以A层土壤pH值下降最明显，B、C层土壤则下降较小。模拟酸雨模拟浸泡土壤25年后，土壤阳离子交换量均有不同程度下降，有机质含量高，原土壤阳离子交换量大的土壤下降幅度也大。     

高锰酸钾缓释剂的制备及其性能研究

利用油相相分离法微胶囊技术,以硬脂酸为壳物质,制备高锰酸钾缓释剂,通过条件优化实验,确定最佳工艺条件为:壳核比值为3∶1、搅拌速度450 r/min以及超声时间为10 min。所制的高锰酸钾缓释剂包覆率为163.3%,在水中缓释行为符合Q=0.00518×t0.611(R2=0.9951)动力学方程,理论缓释期为229.4 d,具有较好的缓释效果。对高锰酸钾缓释剂进行红外光谱和环境电镜扫描分析,结果表明,成膜前后硬脂酸的结构发生改变,硬脂酸对高锰酸钾的微胶囊化不是简单的物理吸附,而是通过化学键合包覆在高锰酸钾表面。