成都颗粒物吸湿增长特征及订正方法研究

利用2013年6月—2014年5月成都市人民南路四段逐时PM_(2.5)质量浓度、大气能见度监测资料及同期温江站相对湿度观测数据,分析了该区域相对湿度对大气消光系数的影响,探讨了消光系数湿度订正方法的原理和技术流程.结果表明:针对细颗粒物而言,平均单位质量“湿”消光系数在相对湿度为40%时存在突变(通过了α=0.05的信度检验),当相对湿度小于40%时,平均单位质量“湿”消光系数呈现平稳波动的特征;而当相对湿度介于40%~90%时,平均单位质量“湿”消光系数增长趋势明显;现有的湿度订正方法未能在成都地区起到相应的订正效果;单位质量“湿”消光系数直观上表现为非平稳随机序列,基于单位质量“湿”消光系数和单位质量“干”消光系数在统计意义下应具有一致性的原则,从不确定性分析的角度提出了消光系数湿度订正的新方法,取得了令人满意的结果.     

Catalytic oxidation of CO over Pt/Fe3O4 catalysts: Tuning O2 activation and CO adsorption

• Strong metal-support interaction exists on Pt/Fe₃O₄ catalysts. • Pt metal particles facilitate the formation of oxygen vacancies on Fe₃O₄. • Fe₃O₄ supports enhance the strength of CO adsorption on Pt metal particles. The self-inhibition behavior due to CO poisoning on Pt metal particles strongly impairs the performance of CO oxidation. It is an effective method to use reducible metal oxides for supporting Pt metal particles to avoid self-inhibition and to improve catalytic performance. In this work, we used in situ reductions of chloroplatinic acid on commercial Fe₃O₄ powder to prepare heterogeneous-structured Pt/Fe₃O₄ catalysts in the solution of ethylene glycol. The heterogeneous Pt/Fe₃O₄ catalysts achieved a better catalytic performance of CO oxidation compared with the Fe₃O₄ powder. The temperatures of 50% and 90% CO conversion were achieved above 260°C and 290°C at Pt/Fe₃O₄, respectively. However, they are accomplished on Fe₃O₄ at temperatures higher than 310°C. XRD, XPS, and H₂-TPR results confirmed that the metallic Pt atoms have a strong synergistic interaction with the Fe₃O₄ supports. TGA results and transient DRIFTS results proved that the Pt metal particles facilitate the release of lattice oxygen and the formation of oxygen vacancies on Fe₃O₄. The combined results of O₂-TPD and DRIFTS indicated that the activation step of oxygen molecules at surface oxygen vacancies could potentially be the rate-determining step of the catalytic CO oxidation at Pt/Fe₃O₄ catalysts. The reaction pathway involves a Pt-assisted Mars-van Krevelen (MvK) mechanism.     

Precursors and potential sources of ground-level ozone in suburban Shanghai

• Air masses from Zhejiang Province is the major source of O₃ in suburban Shanghai. • O₃ formation was in VOC-sensitive regime in rural Shanghai. • O₃ formation was most sensitive to propylene in rural Shanghai. A high level of ozone (O₃) is frequently observed in the suburbs of Shanghai, the reason for this high level remains unclear. To obtain a detailed insight on the high level of O₃ during summer in Shanghai, O₃ and its precursors were measured at a suburban site in Shanghai from July 1, 2016 to July 31, 2016. Using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration weighted trajectories (CWT), we found that Zhejiang province was the main potential source of O₃ in suburban Shanghai. When the sampling site was controlled by south-western winds exceeding 2 m/s, the O₃-rich air masses from upwind regions (such as Zhejiang province) could be transported to the suburban Shanghai. The propylene-equivalent concentration (PEC) and ozone formation potential (OFP) were further calculated for each VOC species, and the results suggested that propylene, (m+p)-xylene, and toluene played dominant roles in O₃ formation. The Ozone Isopleth Plotting Research (OZIPR) model was used to reveal the impact of O₃ precursors on O₃ formation, and 4 base-cases were selected to adjust the model simulation. An average disparity of 18.20% was achieved between the simulated and observed O₃ concentrations. The O₃ isopleth diagram illustrated that O₃ formation in July 2016 was in VOC-sensitive regime, although the VOC/NO_x ratio was greater than 20. By introducing sensitivity (S), a sensitivity analysis was performed for O₃ formation. We found that O₃ formation was sensitive to propylene, (m+p)-xylene, o-xylene and toluene. The results provide theoretical support for O₃ pollution treatment in Shanghai.     

Degradation of polyacrylamide (PAM) and methane production by mesophilic and thermophilic anaerobic digestion: Effect of temperature and concentration

• PAM degradation in thermophilic AD in comparison with mesophilic AD. • PAM degradation and its impact on thermophilic and mesophilic AD. • Enhanced methane yield in presence of PAM during thermophilic and mesophilic AD. • PAM degradation and microbial community analysis in thermophilic and mesophilic AD. Polyacrylamide (PAM) is generally employed in wastewater treatment processes such as sludge dewatering and therefore exists in the sludge. Furthermore, it degrades slowly and can deteriorate methane yield during anaerobic digestion (AD). The impact or fate of PAM in AD under thermophilic conditions is still unclear. This study mainly focuses on PAM degradation and enhanced methane production from PAM-added sludge during 15 days of thermophilic (55°C) AD compared to mesophilic (35°C) AD. Sludge and PAM dose from 10 to 50 g/kg TSS were used. The results showed that PAM degraded by 76% to 78% with acrylamide (AM) content of 0.2 to 3.3 mg/L in thermophilic AD. However, it degraded only 27% to 30% with AM content of 0.5 to 7.2 mg/L in mesophilic AD. The methane yield was almost 230 to 238.4 mL/g VSS on the 8th day in thermophilic AD but was 115.2 to 128.6 mL/g VSS in mesophilic AD. Mechanism investigation revealed that thermophilic AD with continuous stirring not only enhanced PAM degradation but also boosted the organics release from the sludge with added PAM and gave higher methane yield than mesophilic AD.     

长江上游典型区域丰枯转换期水资源变化分析

针对长江上游金沙江下游区域近几年6月和10月出现的较剧烈的水资源丰枯转换现象,以2018年金沙江下游来水过程作为研究案例,考虑金沙江下游流域来水组成及水利工程建设情况,从区间流量分析及上游水库群调蓄影响分析两方面开展了研究工作。研究结果表明:金沙江下游流域丰枯转换主要影响因素为三堆子流量变化,三堆子至溪洛渡区间流量变化影响较小。在6月,上游水库群调蓄对金沙江下游流域丰枯转换影响较大,10月影响相对较小。相关研究成果可为溪洛渡-向家坝梯级水库调度计划制订及实际调度工作提供参考。     

梯级水库群环境风险分析

为提高梯级水库群环境风险管理水平,加强流域生态环境保护,以溪洛渡-向家坝梯级水库为研究对象,基于灾害系统理论和系统动力学,对溪洛渡-向家坝梯级水库环境风险进行了系统梳理,辨识了梯级水库环境风险承载体、风险源、风险诱因,分析了环境风险传递机理,采用贝叶斯理论进行库区水体藻类爆发概率计算。结果表明:溪洛渡-向家坝梯级水库环境风险通过水流、电流、系统动力学流进行传播,并会影响到电站机组和水工建筑物的安全,由于水动力减弱和库区污染物排放,导致库区水体藻类爆发概率为2.42%,死鱼概率为1.21%,在此基础上,绘制环境风险传递拓扑图,并提出相应的环境风险管控措施。     

Utilization of MSWI fly ash as partial cement or sand substitute with focus on cementing efficiency and health risk assessment

• Washed MSWI fly ash was used as partial cement or sand substitute. • Sand replacing is beneficial for strength, while cement replacement reduces strength. • Cementing efficiency factor and mortar pore structure explain the strength results. • Health risk assessment was conducted for MSWI fly ash blended cement mortar. • CR and HI contributed by different exposures and heavy metals were analyzed. The strength of cement substituted mortar decreases with the increase in fly ash amount, whereas the strength increases when the fly ash is blended as sand substitute. A mortar with highest strength (compressive strength= 30.2 Mpa; flexural strength= 7.0 Mpa) was obtained when the sand replacement ratio was 0.75%. The k value (cementing efficiency) of fly ash varied between 0.36 and 0.15 for the fly ash fraction in binder between 5% and 25%. The k values of fly ash used for sand replacement were all significantly above that used for cement substitution. The macropores assigned to the gaps between particles decreased when the fly ash was used as sand replacement, providing an explanation for the strength enhancement. The waste-extraction procedure (toxicity-sulphuric acid and nitric acid method (HJ/T 299-2007)) was used to evaluate metal leaching, indicating the reuse possibility of fly ash blended mortar. For the mortar with the mass ratio of fly ash to binder of 0.5%, the carcinogenic risks (CR) and non-carcinogenic hazard quotient (HQ) in sensitive scenario for blended mortar utilization were 9.66 × 10^-7 and 0.06, respectively; these results were both lower than the threshold values, showing an acceptable health risk. The CR (9.89 × 10^-5) and HQ (3.89) of the non-sensitive scenario for fly ash treatment exceeded the acceptable threshold values, indicating health risks to onsite workers. The main contributor to the carcinogenic and non-carcinogenic risk is Cr and Cd, respectively. The CR and HQ from inhalation was the main route of heavy metal exposure.     

UiO-66(Zr)@多孔陶瓷复合材料的制备及对络合态重金属EDTA-Cu(Ⅱ)的去除

本文采用多孔陶瓷作为基体制备了锆基金属有机骨架UiO-66@多孔陶瓷复合材料.通过扫描电子显微镜(SEM)、粉末X射线衍射(PXRD)、氮气吸附和傅里叶变换红外光谱(FTIR)等表征手段对比了氢氧化钠脱硅和乙二胺表面改性等基体活化方式对UiO-66(Zr)在多孔陶瓷表面负载情况的影响.结果表明,经过乙二胺表面改性的多孔陶瓷对UiO-66(Zr)的负载更均匀,负载效果更好.以EDTA-Cu(Ⅱ)为考察对象,研究了UiO-66(Zr)@乙二胺表面改性多孔陶瓷复合材料对络合态重金属的净化效能.结果表明,UiO-66(Zr)@多孔陶瓷复合材料在较宽的酸碱条件下(pH=3—9)对络合态重金属EDTA-Cu(Ⅱ)均表现出良好的吸附性能,饱和吸附量为1.17 mg·g~(-1),并可通过NaOH解吸再生,从而实现材料的重复利用.     

CWPO体系中污泥炭催化降解头孢氨苄废水

通过加入正丁醇以共沸蒸馏法对剩余污泥进行脱水,再对污泥进行干燥、焙烧和改性得到污泥炭催化剂.将污泥炭催化剂用于催化湿式过氧化氢氧化体系,处理头孢氨苄废水.采用响应面法中的中心组合设计实验,考察反应温度、初始pH和过氧化氢投加量对TOC降解率的影响,反应温度和过氧化氢投加量具有显著交互作用.在最佳实验条件下(T=50℃、pH=3.00、H_2O_2=0.071 mol·L~(-1)),TOC去除率为59%,接近预测的TOC去除率(60%),在95%的置信区间内,说明该模型可靠.SEM、TEM、TPD-MS、XPS和FT-IR等分析结果表明污泥炭表面存在纳米尺寸片状结构,这种结构中存在酚羟基、羰基、羧基等活性官能团和醌类结构,且ICP-OES、EDAX和~(57)Fe穆斯堡尔谱等分析结果表明,污泥炭中含有不同价态的Fe,能有效地催化过氧化氢分解,将头孢氨苄转化为苯甲酸、丁二酮等小分子物质,再进一步完全氧化.