Effect of soil moisture dynamics on dense nonaqueous phase liquid (DNAPL) spill zone architecture in heterogeneous porous media

The amount, location, and form of NAPL in contaminated vadose zones are controlled by the spatial distribution of water saturation and soil permeability, the NAPL spill scenario, water infiltration events, and vapor transport. To evaluate the effects of these processes, we used the three-phase flow simulator STOMP, which includes a new permeability-liquid saturation-capillary pressure (k-S-P) constitutive model. This new constitutive model considers three NAPL forms: free, residual, and trapped. A 2-D vertical cross-section with five stratigraphic layers was assumed, and simulations were performed for seven cases. The conceptual model of the soil heterogeneity was based upon the stratigraphy at the Hanford carbon tetrachloride (CT) spill site. Some cases considered co-disposal of NAPL with large volumes of wastewater, as also occurred at the Hanford CT site. In these cases, the form and location of NAPL were most strongly influenced by high water discharge rates and NAPL evaporation to the atmosphere. In order to investigate the impact of heterogeneity, the hydraulic conductivity within the lower permeability layer was modeled as a realization of a random field having three different classes. For six extreme cases of 100 realizations, the CT mass that reached the water table varied by a factor of two, and was primarily controlled by the degree of lateral connectivity of the low conductivity class within the lowest permeability layer. The grid size at the top boundary had a dramatic impact on NAPL diffusive flux just after the spill event when the NAPL was present near the ground surface. NAPL evaporation with a fine grid spacing at the top boundary decreased CT mass that reached the water table by 74%, compared to the case with a coarse grid spacing, while barometric pumping had a marginal effect for the case of a continuous NAPL spill scenario considered in this work. For low water infiltration rate scenarios, the distribution of water content prior to a NAPL spill event decreased CT mass that reached the water table by 98% and had a significant impact on the formation of trapped NAPL. For all cases simulated, use of the new constitutive model that allows the formation of residual NAPL increased the amount of NAPL retained in the vadose zone. Density-driven advective gas flow from the ground surface controlled vapor migration in strongly anisotropic layers, causing NAPL mass flux to the lower layer to be reduced. These simulations indicate that consideration of the formation of residual and trapped NAPLs and dynamic boundary conditions (e.g., areas, rates, and periods of different NAPL and water discharge and fluctuations of atmospheric pressure) in the context of full three-phase flow are needed, especially for NAPL spill events at the ground surface. In addition, NAPL evaporation, density-driven gas advection, and NAPL vertical movement enhanced by water flow must be considered in order to predict NAPL distribution and migration in the vadose zone.     

边坡变形时序非线性判定及混沌预测研究

以探讨边坡变形性质及混沌预测可行性为目的,基于混沌理论利用相空间重构技术对其变形时间序列进行混沌特征判定,试验显示变形系统具有混沌特性,可用混沌相关理论进行研究;基于混沌相空间重构技术,笔者构建了多种混沌预测模型进行混沌预计研究,分析各类模型的工程实际应用效果;针对单次监测时序预测精度较低的问题,提出累加时序预测方案,训练结果显示,短期预测精度变形累计值基本控制在5%以内,高程值预测相对误差均低于1%,预测精度较高,可以用于工程实际。     

矿井瓦斯煤尘爆炸传播数值模拟研究

基于连续相、燃烧、颗粒相数理方程建立瓦斯煤尘爆炸传播数理模型,并应用连续相、颗粒相计算方法,依据大型巷道瓦斯爆炸、瓦斯煤尘爆炸传播实验数据,借助普遍应用的流场模拟平台,成功开发瓦斯、煤尘爆炸数值模拟系统。该系统可有效地模拟煤矿瓦斯、煤尘的爆炸事故过程,对瓦斯爆炸的爆燃转爆轰、煤尘是否参与爆炸、爆炸冲击传播速度、衰减规律以及爆炸灾害的波及范围都能进行较准确的模拟。     

矿井通风仿真系统双线图的快速自动绘制研究

在深入研究通风网络巷道连接关系的基础上,创造性地提出一种新的效率更高的通风系统双线图的快速自动绘制方法,即"假双线法"。"假双线法"与固定宽度双线法有本质的不同,其本质是将单线巷道的线型用固定宽度双线线型表示,再对交叉点进行消隐处理,无需计算双线坐标来实现双线图的快速自动绘制。该法较好地解决了传统方法的缺陷,具有普遍性,其计算量小,执行效率高,并在双线图的基础上很容易拓展生成通风系统立体图。笔者研究成果,对于研发、改进矿井通风仿真图形系统和解决其他行业类似问题具有一定的参考价值。     

双负载双金属催化剂催化有机卤化物水相脱卤研究

通过把起相转移作用的聚乙二醇链固载在硅胶上（SiO2-PEG600）,再将聚乙稀吡咯烷酮（PVP）络合双金属Pd-Cu(PVP-PdCl2-CuCl2)后负载其中,制成一种新型双负载双金属水相脱卤催化剂PVP－PdCl2-CuCl2/SiO2-PEG600。以甲酸钠为氢转移试制,在水相中催化有机卤化物脱卤,研究结果表明：反应温度为800℃,Pd∶Cu=2∶1（摩尔比）,反应介质pH≈11.7左右时,该催化剂对芳香氯化物及α－氯代酮、酯具有良好的催化脱氯和重复使用性能。     

固相微萃取-气相色谱/质谱联用法测定饮用水中苯类化合物

用固相微苹取(ＳＰＭＥ)－气相色谱/质谱联用法测定饮用水中苯类化合物,以１００μｍ ＰＤＭＳ(聚二甲基硅氧烷)萃取针提取、浓缩、分离与测定九种目标化合物．萃取时间经优化选定为８ｍｉｎ,而热解析时间设定为２ｍｉｎ． 本方法的相对标准偏差小于５%,线性范围宽(２０ｎｇ·ｍｌ－１－１００００ｎｇ·ｍｌ－１),多数化合物的检测限低于５μｇ·ｌ－１．饮用水样品检测显示,样品加标回收率范围在８４%至１１０%内．     

碳包覆Pd/Al2O3催化剂催化4-溴苯酚加氢脱溴的活性和稳定性调控研究

在污染物液相催化加氢脱卤过程中,提高催化剂的稳定性至关重要.以水热合成法制备了不同碳包覆量的Pd/Al₂O₃@C催化剂,对催化剂进行了系列表征,并将催化剂应用于4-溴苯酚(4-BP)污染物的催化加氢脱溴反应.表征结果显示碳层提高了Pd/Al₂O₃的表面疏水性,有利于4-BP在催化剂上的吸附.并且在Pd/Al₂O₃@C催化剂的碳化过程中,碳还原部分Pd颗粒,并保留部分正价态Pd活性位,增强了4-BP中C-Br键的活化.与Pd/Al₂O₃相比,碳涂层提高了催化剂的催化活性.但当碳包覆量超过最佳包覆量后,暴露的Pd粒子随碳包覆量的增加而减少,导致活性下降.此外,碳层修饰后,催化剂的稳定性显著提高,从而大大抑制了Pd粒子的团聚和损耗.Pd/Al₂O₃@C表面的碳涂层对卤素具有较高的耐受性,从而减轻了液相催化加氢脱卤反应中活性中心的中毒.     

HPLC和HPLC-MS/MS测定地表水中酚类化合物

采用高效液相色谱法(HPLC)和高效液相色谱-三重四级杆质谱联用法(HPLC-MS/MS)测定地表水及饮用水中11种酚类化合物,通过优化测定条件,使HPLC法在0.020 mg/L~50.0 mg/L范围内,HPLC-MS/MS法在0.500μg/L~250μg/L范围内线性良好,方法检出限分别为0.005μg/L~0.031μg/L和0.005μg/L~1.56μg/L。未检出的实际样品加标回收率分别为57.2%~96.7%和81.3%~113%,RSD分别为1.5%~5.3%和3.9%~17.7%。     

固相萃取-GC/MS法测定水中持久性有机污染物

采用Envi-18固相萃取小柱富集水样,用正己烷/丙酮混合溶剂洗脱水样中42种POPs化合物,再用气质联用法测定。通过优化仪器监测条件,使目标物在0.250 mg/L~5.00 mg/L范围内线性良好。方法检出限为50.9 ng/L~11 640 ng/L,实际水样加标回收率为57.1%~129%,测定结果的RSD为0.1%~13.8%。将该方法用于测定浙江省东苕溪流域的45份水样,结果滴滴涕、六六六等有机氯农药的检出率较高,其他POPs的检出率较低。     

氨基化有机-无机杂化整体柱分离富集环境水中五价砷

将四乙氧基硅烷(TEOS)和N-(β-氨乙基)-γ-氨丙基三乙氧基硅烷(AEAPTES)作为共聚前体,采用在毛细管内原位聚合的方式制备得到氨基功能化的有机-无机杂化整体柱,将其作为针式固相微萃取(SPME)介质,建立了现场分离富集环境水中As(V)的SPME方法,优化了有机-无机杂化整体柱富集As(V)的实验条件,并研究了整体柱对As(V)的吸附/洗脱性能和富集能力,实现了环境水样中As(V)的高效、快速、高选择性检测。