焚烧厂周边居民重金属污染物多途径暴露的健康风险

焚烧厂排放的重金属污染物会通过不同途径富集于周围环境介质中,如土壤、地表水、地下水、大气、蔬菜和家禽等.焚烧厂周边人群通过上述各种环境介质暴露于重金属,并产生累计的健康危害.然而目前研究很少关注人群通过多途径暴露的累计健康风险.本研究调查了一座典型医疗废物焚烧厂周边不同环境介质中的重金属含量,分析其与人体暴露关系,并计算了其不同途径暴露的健康风险及累计风险.结果表明重金属产生的非致癌风险大小As(298.1)Cr(35.4)Mn(14.0)Pb(7.0)Cu(2.3)Hg(1.9)Zn(1),致癌风险大小依次为As(1.32×10-2)Cr(1.31×10-2)10-5,均超过风险可接受水平;食用自产蔬菜是主要的暴露途径(贡献率为68%~92%)其次为自养家禽贡献率为10%左右.这说明区别于通常关注的通过土壤、水体、空气等介质暴露的风险相比,食用研究区周边的动植物产品导致的风险更大,需要引起重点关注;不确定分析结果表明考虑污染物浓度不确定条件下,场地健康风险大约有0.54~2.28倍的增加;风险管理研究表明通过截断食用本地蔬菜和家禽,除Cr的致癌风险外,其他重金属对厂区居民的健康风险水平会迅速降低至可接受水平.     

Modes of governing Canadian waste management: a case study of Metro Vancouver’s energy-from-waste controversy

Managing municipal solid waste is a pressing environmental and political concern for Canadian municipalities who bear the primary responsibility for waste management (WM). In 2015, Metro Vancouver’s (MV’s) plans to expand their capacity to expand their WM capacity with energy-from-waste technology was abandoned, despite shrinking landfill space and persistent public opposition to new landfills. Using Bulkeley et al.’s [(2005). Governing municipal waste: towards a new analytical framework. Journal of Environmental Policy and Planning, 7(1), 1–23. doi:10.1080/15239080500251700] ‘modes of governing framework’, we analyse MV’s failed attempt to expand their energy-from-waste capacity to better understand the challenges associated with governing WM in Canada. We argue that a history of downloading responsibility for WM to municipalities, regional districts, and industry has fragmented WM governance, posing a challenge for developing new waste infrastructure. We find that this localization of responsibility is incompatible with contemporary WM challenges. The scalar mismatch between waste’s material impacts and the scale at which waste is managed has resulted in co-dependence and conflict between putatively independent municipalities, regional districts, and private companies. This inhibits higher-level WM coordination while the autonomy of individual municipalities is simultaneously undermined.     

Evaluating the Applicability of a Two‐dimensional Flow Model of a Highly Heterogeneous Domain to Flow and Environmental Management

Two‐dimensional simulation of highly heterogeneous domains, especially those with disparate length scales, roughness conditions, and geometries, often leads to challenges such as long computation times and numerical instability. Simulation of challenging domains is often needed to guide flood management and environmental regulation agencies in operation and potential domain modifications. This work evaluates the ability of a two‐dimensional unsteady hydrodynamic model to represent long‐duration transient flows over a domain with highly heterogeneous roughness, geometric characteristics, and length scales through bed roughness representation. The domain includes 13 km of Cache Creek and the 14.5 km² Cache Creek Settling Basin, which traps both sediment and mercury. Calibration under different bed roughness methods, validation, and modeling results of bathymetric modification scenarios are presented. The modeling approach's performance supports its application as a tool for management of similar domains, such as settling basins, leveed floodplains, and reservoirs. Accurate representation of flow dynamics can also inform environmental management that involves transport of sediments, nutrients, and heavy metals. This study found that a two‐dimensional unsteady flow model can accurately represent long‐duration transient flow in a large settling basin with highly heterogeneous characteristics without parsing of the domain or flow events simulated.     

固硫灰固化焦化废水处理外排污泥

采用机械力化学法活化循环流化床燃煤固硫灰,用于固化焦化废水处理外排污泥(CWT污泥)。探讨了固硫灰活化条件,并通过XRD和FTIR分析了固硫灰固化CWT污泥中重金属的机理。实验结果表明:当m(Ca O)∶m(Ca O+固硫灰)为20%、球磨频率为40 Hz、球磨时间为2 h时,养护28 d固硫灰固化体的平均抗压强度达到72.2 MPa;当污泥掺加量为50%(w)时,养护28 d含污泥固化体的抗压强度达到8.5 MPa,固化体浸出液中Pb2+和As5+的质量浓度分别为0.177 mg/L和0.013 mg/L,均远低于GB 5085.3—2007《危险废物鉴别标准浸出毒性鉴别》的规定限值。XRD和FTIR表征结果表明,在固硫灰活化过程中,混合体系水化生成了C—S—H凝胶、斜方钙沸石和钙矾石,可通过物理包裹、吸附及离子交换的形式实现CWT污泥中Pb2+和As5+的固化/稳定化。     

旋转填充床分离沼气中的CO_2

以水为吸收液,采用旋转填充床分离微生物厌氧发酵沼气中的CO_2,考察了工艺条件对CO_2吸收效果的影响。实验结果表明:进液量越大、气液比越小、进口CO_2体积分数越小、操作压力越大、进液温度越低则CO_2的吸收效果越好,而床转速以适中为宜;在进液量60 L/h、气液比3.3、床转速1 000 r/min、进口CO_2体积分数40%、操作压力1.2 MPa、进液温度5℃的条件下,CO_2吸收率为57.4%,提纯后气体的CO_2体积分数为17%。     

Experimental investigation of ash deposits on convection heating surfaces of a circulating fluidized bed municipal solid waste incinerator

Incineration of municipal solid waste(MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction, as well as a source of renewable energy.During MSW combustion, increased formation of deposits on convection heating exchanger surfaces can pose severe operational problems, such as fouling, slagging and corrosion.These problems can cause lower heat transfer efficiency from the hot flue gas to the working fluid inside the tubes. A study was performed where experiments were carried out to examine the ash deposition characteristics in a full-scale MSW circulating fluidized bed(CFB) incinerator, using a newly designed deposit probe that was fitted with six thermocouples and four removable half rings. The influence of probe exposure time and probe surface temperature(500, 560, and 700℃) on ash deposit formation rate was investigated. The results indicate that the deposition mass and collection efficiency achieve a minimum at the probe surface temperature of 560℃. Ash particles are deposited on both the windward and leeward sides of the probe by impacting and thermophoretic/condensation behavior. The major inorganic elements present in the ash deposits are Ca,Al and Si. Compared to ash deposits formed on the leeward side of the probe,windward-side ash deposits contain relatively higher Ca and S concentrations, but lower levels of Al and Si. Among all cases at different surface temperatures, the differences in elemental composition of the ash deposits from the leeward side are insignificant.However, as the surface temperature increases, the concentrations of Al, Si, K and Na in the windward-side ash deposits increase, but the Ca concentration is reduced. Finally,governing mechanisms are proposed on the basis of the experimental data, such as deposit morphology, elemental composition and thermodynamic calculations.     

Water softening by induced crystallization in fluidized bed

Fluidized bed and induced crystallization technology were combined to design a new type of induced crystallization fluidized bed reactor. The added particulate matter served as crystal nucleus to induce crystallization so that the insoluble material, which was in a saturated state, could precipitate on its surface. In this study, by filling the fluidized bed with quartz sand and by adjusting water p H, precipitation of calcium carbonate was induced on the surface of quartz sand, and the removal of water hardness was achieved.With a reactor influent flow of 60 L/hr, a fixed-bed height of 0.5 m, pH value of 9.5, quartz sand nuclear diameter of 0.2–0.4 mm, and a reflux ratio of 60%, the effluent concentration of calcium hardness was reduced to 60 mg/L and 86.6% removal efficiency was achieved. The resulting effluent reached the quality standard set for circulating cooling water. Majority of the material on the surface of quartz sand was calculated to be calcium carbonate based on energy spectrum analysis and moisture content was around 15.994%. With the low moisture content, dewatering treatment is no longer required and this results to cost savings on total water treatment process.     

旋滤组合移动式颗粒床除尘器优化设计建模

以旋滤组合移动式颗粒床除尘器的性能-结构关系为基础,建立移动式颗粒床除尘器优化设计的数学模型。该模型以除尘效率最大为优化目标,以结构参数与运行参数间的关系为约束条件,对特定的粉尘和含尘气体以及一定的运行参数而言,优化设计变量为移动式颗粒床除尘器的结构参数(主要有进气口尺寸,旋风体直径,过滤床直径、厚度及有效过滤高度),从而确定移动式颗粒床除尘器的最佳结构尺寸。通过设计实例检验,证明了该模型具有较好的实际应用价值。     

疏浚底泥生态毒理性风险分析方法的研究进展

疏浚底泥土地利用应该尽可能避免对施用土壤、周围地表水及地下水的污染,通过生物聚积试验和急性、亚急性毒性试验考查底泥对水及土壤中生物、植物发芽生长的影响,通过渗滤试验评价其对地下水层的污染。疏浚底泥土地利用前,其生态毒理性风险分析的方法包括风险简化评价和风险详细评价。通常简化评价方法用于估计底泥土地利用对生态系统影响程度;详细评价法进一步通过生物毒性试验和柱状渗滤试验来确定其生态毒理性影响,界定其风险特性。     

一种选择城市垃圾处理方式的新方法--模糊数学决策法

对模糊数学决策法的基本原理、方法和步骤作了简要介绍，并将其应用到成都市区生活垃圾处理方式的选择中，其决策结果与成都市区目前采用的生活垃圾处理方式相符，表明了该方法的实用性。本研究为合理选择城市垃圾处理方式提供了一种量化方法。