离子类型、强度和铁氧化物影响下微塑料的迁移行为及模型计算

土壤中的微塑料（MPs）作为一种新型污染物而被广泛关注,其迁移行为受到自身理化性质、土壤溶液化学组成和土壤矿物等因素的影响.目前,铁氧化物存在时,离子类型和离子强度对MPs迁移行为的影响机制尚不明确.通过稳定性实验和迁移实验,重点考察了离子类型、离子强度和铁氧化物对带有不同官能团聚苯乙烯微塑料（PSMPs）迁移行为的影响,并用胶体迁移模型、CD-MUSIC模型及DLVO理论探讨其迁移机制.结果表明,PSMPs在NaH₂PO₄背景下的稳定性最强,标准化浓度（c/c₀）达到0.99,而在CaCl₂背景下的稳定性相对弱,c/c₀降低至0.94.不同离子种类对PSMPs的迁移行为产生不同影响,对于阳离子Na⁺和Ca²⁺,二价Ca离子有架桥作用和较强的电荷中和作用,更能阻滞PSMPs在石英砂中的迁移,出水溶液中PSMPs回收率低至（43.83±1.71）%且第二动力学位点上的一级保留系数k_2a为1.54 min^-1,铁氧化物会进一步加剧阻滞作用,回收率降低为（6.04±0.40）%且k_2a升高为5.33 min^-1;对于阴离子Cl^-和PO₄^3-,PSMPs在纯石英砂柱中的迁移主要受其自身表面电负性的控制,Cl^-离子下PSMPs电负性更低,回收率升高［（92.95±0.63）%］且k_2a降低（0.19 min^-1）,而当铁氧化物存在时,PSMPs的迁移则受控于载铁石英砂表面的Zeta电位.CD-MUSIC模型计算结果显示PO₄^3-容易吸附在铁氧化物表面形成内圈络合物,降低载铁石英砂表面的电负性,因此PSMPs在PO₄^3-背景下的回收率升高［（76.22±1.39）%］且k_2a降低（0.66 min^-1）;同时,该内圈络合物的形态受PO₄^3-浓度的控制且不同形态的内圈络合物具有不同的表面负电荷数,因此高PO₄^3-浓度下载铁石英砂表面电负性反而高,不利于PSMPs迁移.此外,PSMPs的迁移均随着离子强度的增加而降低.最后,DLVO理论计算出不同条件下PSMPs和介质间的一级势垒变化趋势与PSMPs的迁移能力一致,即较高的一级势垒表明PSMPs和介质间较大的相互斥力有利于PSMPs的迁移,可以更好地阐明PSMPs的迁移行为.     

碳纳米管对污染物的吸附及其在土水环境中的迁移行为

碳纳米管具有独特的物理化学特性,对污染物具有优异的吸附性能,在环保领域具有巨大的应用潜力,因而吸引人们对碳纳米管吸附有毒污染物的行为和规律开展了大量研究.同时,碳纳米管特有的表面化学性质和结构特征,使得其自身的环境行为具有一定的风险性,对碳纳米管在水土环境中的迁移行为进行评价,是碳纳米管工程应用之前必须要解决的重要问题,相关研究也有一定程度的开展.本文从碳纳米管对环境污染物的吸附行为和相关机理以及碳纳米管在水土环境中的迁移行为方面进行了综述,阐述了这些研究对于评估碳纳米管的环境应用潜力、环境和生态风险所具有的意义.     

Solute transport in crystalline rocks at Äspö — II: Blind predictions, inverse modelling and lessons learnt from test STT1

Based on the results from detailed structural and petrological characterisation and on up-scaled laboratory values for sorption and diffusion, blind predictions were made for the STT1 dipole tracer test performed in the Swedish Äspö Hard Rock Laboratory. The tracers used were nonsorbing, such as uranine and tritiated water, weakly sorbing ²²Na⁺, ⁸⁵Sr²⁺, ⁴⁷Ca²⁺and more strongly sorbing ⁸⁶Rb⁺, ¹³³Ba²⁺, ¹³⁷Cs⁺.Our model consists of two parts: (1) a flow part based on a 2D-streamtube formalism accounting for the natural background flow field and with an underlying homogeneous and isotropic transmissivity field and (2) a transport part in terms of the dual porosity medium approach which is linked to the flow part by the flow porosity.The calibration of the model was done using the data from one single uranine breakthrough (PDT3). The study clearly showed that matrix diffusion into a highly porous material, fault gouge, had to be included in our model evidenced by the characteristic shape of the breakthrough curve and in line with geological observations.After the disclosure of the measurements, it turned out that, in spite of the simplicity of our model, the prediction for the nonsorbing and weakly sorbing tracers was fairly good. The blind prediction for the more strongly sorbing tracers was in general less accurate. The reason for the good predictions is deemed to be the result of the choice of a model structure strongly based on geological observation. The breakthrough curves were inversely modelled to determine in situ values for the transport parameters and to draw consequences on the model structure applied. For good fits, only one additional fracture family in contact with cataclasite had to be taken into account, but no new transport mechanisms had to be invoked. The in situ values for the effective diffusion coefficient for fault gouge are a factor of 2–15 larger than the laboratory data. For cataclasite, both data sets have values comparable to laboratory data. The extracted K_d values for the weakly sorbing tracers are larger than Swedish laboratory data by a factor of 25–60, but agree within a factor of 3–5 for the more strongly sorbing nuclides. The reason for the inconsistency concerning K_ds is the use of fresh granite in the laboratory studies, whereas tracers in the field experiments interact only with fracture fault gouge and to a lesser extent with cataclasite both being mineralogically very different (e.g. clay-bearing) from the intact wall rock.     

膨润土颗粒对多壁碳纳米管在饱和多孔介质中迁移的影响

选用石英砂填充柱模拟土壤体系,通过对比在有无膨润土颗粒(Bentonite particles)存在时得到的多壁碳纳米管(MWCNTs)的穿透曲线和滞留曲线,考察膨润土颗粒对MWCNTs在多孔介质中迁移沉积行为的影响.实验选取的Na Cl溶液离子强度为1 mmol·L-1和30 mmol·L-1,Ca Cl2溶液离子强度为0.3 mmol·L-1和1.2 mmol·L-1.溶液p H不进行调节,p H值大约为5.6.研究结果表明,在低离子强度Na Cl(1 mmol·L-1)溶液中,有膨润土颗粒共存时MWCNTs的穿透曲线和滞留曲线与没有膨润土颗粒共存时相近,表明该条件下MWCNTs的迁移和沉积行为不受膨润土颗粒影响,而在高离子强度Na Cl(30 mmol·L-1)溶液中,有膨润土颗粒共存时MWCNTs的穿透曲线低于没有膨润土颗粒共存时MWCNTs的穿透曲线,表明该条件下膨润土颗粒会抑制MWCNTs的迁移,且增加的滞留主要发生在柱子入口端;在Ca Cl2溶液中,无论离子强度的高低(0.3 mmol·L-1和1.2 mmol·L-1),有膨润土颗粒共存时,MWCNTs的穿透曲线和滞留曲线都不发生变化,说明在二价溶液中膨润土颗粒对MWCNTs的迁移和沉积行为影响不大.     

华北平原耕作土壤特性对基因工程菌迁移的影响

基因工程菌在土壤中的迁移是影响污染土壤生物强化修复的重要因素.在华北平原饱和耕作土壤中,考察了1株阿特拉津降解基因工程菌迁移留存及其影响因素.结果表明,在饱和耕作土壤中,平流渗透是基因工程菌迁移的主要机制,其过程可用过滤模型拟合.土壤性质对孔隙水流和基因工程菌迁移具有显著影响.随着土壤粒径、孔隙率和土壤砂粒组分增加,土壤水力传导率常数增大,基因工程菌过滤系数减小,土壤对基因工程菌过滤留存作用降低.土壤条件不变时,增加入渗流量也会增大土壤水力传导率常数,减小基因工程菌过滤系数.饱和土壤中,水力传导率常数为5.02~6.70 m·d-1时,基因工程菌在土壤中的过滤系数为0.105~0.274,二者存在显著负相关关系.     

城市生活垃圾集装箱转运过程中污染物产生状况研究

以上海市某生活垃圾中转站垃圾集装箱为研究对象,分析了1 a不同季节中转站集装箱内垃圾二次污染物的产生和变化规律.结果表明,集装箱内产生的主要气体指标中,H2S的变化范围为0.3~10.3 mg·m-3;CH4的变化范围为0.02%~2.97%;NH3的变化范围为0.7~4.5 mg·m-3,浓度峰值都出现在夏季.产生的渗滤液水质指标中,pH值在5.4~6.3之间变化,呈现酸性;SS在9 120~32 475 mg·L-1之间变化,波动较大;有机物COD的变化范围为41 633~84 060 mg·L-1,BOD5在18 116~34 130 mg·L-1之间变化,呈现出冬季高于夏季的特点;氨氮和总磷的变化范围分别为537~1 222 mg·L-1和17.98~296 mg·L-1之间,季节变化不明显.极端温度特别是夏季高温对箱体内气体污染物的产生影响明显,警示夏季要谨防在高温暴露和过长的停留时间,以防止易燃易爆气体和其他污染物的大量产生.     

碘普罗胺降解菌Pseudomonas sp. I-24共代谢降解性能研究

菌株Pseudomonas sp.I-24(I-24)难以利用碘普罗胺(IOP)作为唯一的碳源和能源进行生长和代谢,因此本研究选用淀粉、麦芽糖、葡萄糖和甘油作为I-24共代谢IOP的外加碳源,考察了在摇瓶实验中,不同外加碳源对I-24生长及降解IOP的影响.结果表明,I-24共代谢IOP符合一级反应动力学特征,淀粉对共代谢过程的促进作用最为显著,IOP的五日降解率可达到92.7%,I-24的IOP降解酶活力在培养第3 d达到最高0.182 mU,淀粉投加的最佳浓度为1 g·L-1,然而葡萄糖和麦芽糖分别对I-24的生长和电子传递系统活性(ETSA)有着最佳促进作用,表明降解菌生长过快将导致竞争性抑制,降低IOP降解率,同时ETSA与共代谢作用无直接关联.此外,从空白样表现出的酶活力得出IOP降解酶即使在低基质条件下同样可被诱导产生.     

危险品运输道路轴辐式网络设计

为降低危险品运输网络的总风险和成本,实现规模效益,根据危险品道路运输网络规划中存在监管者路网规划和运输者路线选择的双层约束特征,探讨轴辐式网络在危险品运输网络设计中的应用。针对长距离、大规模的第三方危险品货运业务,建立上层以风险最小化,下层以成本最小化为目标的双层规划模型。运用Matlab对模型进行求解。最后,通过实例分析检验模型和算法的有效性。结果表明,通过对运输企业网络进行轴辐式网络设计,即将原有节点设置为一个或多个枢纽点,集中零散分布的货源,能比传统直通式物流网络设计节约总运输成本。     

2010年中国东部PM2.5空间分布及沉降模拟研究

结合我国目前面临的PM2.5污染严重问题,采用CMAQ 4.7.1模式模拟我国东部各省PM2.5浓度分布,并探索了其输送、沉降规律.结果表明:综合空气质量模式CMAQ模拟结果与观测结果较为一致,可以较好地模拟PM2.5质量浓度变化特征;我国东部PM2.5呈现明显的季节分布特征,且PM2.5质量浓度分布与污染源的位置分布有较好的对应,呈现由城市边缘向城市中心推移递增的趋势,区域性PM25高值中心可达120 μg/m3以上;湿沉降是细颗粒物的主要去除方式,且湿沉降量至少为干沉降量5倍以上;PM2.5夏季沉降通量最大,冬季最小,我国东部地区沉降通量高值中心可达30 mg/(m2·d)以上;模拟区域湿沉降量占总沉降量的91％以上,模拟计算区域的总沉降量为4.67×106 t/a,其中京津冀地区细颗粒物总沉降量为1.65 × 106 t/a.     

Energy consumption and carbon emission for tourism transport in World Heritage Sites: a case of the Wulingyuan area in China

Transport profoundly affects energy use and carbon dioxide emissions in the tourism sector. The Wulingyuan Scenic Area (WSA), a natural heritage destination in China, is chosen for the case study. The energy consumption and carbon emission of 10 types of tourism transportation modes at the destination are measured and analyzed using a bottom‐up approach for the period of 1979 to 2010. Scenarios were created to project the effects of single and multiple factors on energy consumption and carbon emission by tourism transportation during 2011‐2020. The results showed the following: (a) there is a large difference in energy consumption and carbon emission per capita and per kilometer per capita among the 10 vehicle modes; (b) the monthly energy consumption and carbon emission of tourism transportation differed significantly, the month with the highest (October) are respectively 6.8 and 4 times that of the lowest month (January); (c) the highest annual growth rate of energy consumption and carbon emission are respectively as 32.16% and 27.98% during 1979‐2010; and (d) the amount of energy consumption and carbon emission in the multiple factor scenarios are lower than that in the reference and single factor scenarios during 2011‐2020.