基于洪涝风险分析的纽约市城市绿地规划设计及其对中国的启示

1968年美国开始推行洪涝保险计划,不断完善对洪涝风险的研究,并逐步形成了一套相对完善的洪泛区管理体系,而洪涝风险分析在洪涝保险、城市规划、土地开发、应急管理等领域广泛应用。纽约市在经历了多次飓风侵害,尤其是2012年飓风桑迪（Sandy）之后,意识到城市绿地在极端暴雨事件时对雨洪调蓄的重要作用,经过持续的研究实践,提出了基于洪涝风险分析的城市绿地规划设计要求。基于总结美国纽约市在飓风桑迪影响下对洪涝风险图的调整,及其对城市绿地规划设计相关要求,提出其对我国洪涝风险管控及城市绿地规划设计的启示。     

锐钛矿型二氧化钛的低温合成及其吸附除氟性能的研究

通过水解法在50℃低温条件下合成了锐钛矿型TiO₂,使用XRD、FT-IR、BET等方法对TiO₂进行了表征,并研究其对水中氟离子的吸附行为。结果表明:所合成锐钛矿型TiO₂比表面积达到278.93 m2/g,常温下对氟离子的最大吸附量为30.02 mg/g。吸附过程符合Langmuir等温线模型和准一级动力学模型,是自发性的吸热过程,吸附机理为静电吸引。     

Acceleration of floc-water separation and floc reduction with magnetic nanoparticles during demulsification of complex waste cutting emulsions

Waste cutting emulsions are difficult to treat efficiently owing to their complex composition and stable emulsified structure. As an important treatment method for emulsions, chemical demulsification is faced with challenges such as low flocs–water separation rates and high sludge production. Hence, in this study, Fe₃O₄ magnetic nanoparticles (MNPs) were used to enhance chemical demulsification performance for treating waste cutting emulsions under a magnetic field. The addition of MNPs significantly decreased the time required to attain sludge–water separation and sludge compression equilibrium, from 210 to 20 min. In addition, the volume percentage of sludge produced at the equilibrium state was reduced from 45% to 10%. This excellent flocculation–separation performance was stable over a pH range of 3–11. The magnetization of the flocculants and oil droplets to form a flocculant–MNP–oil droplet composite, and the magnetic transfer of the composite were two key processes that enhanced the separation of cutting emulsions. Specifically, the interactions among MNPs, flocculants, and oil droplets were important in the magnetization process, which was controlled by the structures and properties of the three components. Under the magnetic field, the magnetized flocculant–MNP–oil droplet composites were considerably accelerated and separated from water, and the sludge was simultaneously compressed. Thus, this study expands the applicability of magnetic separation techniques in the treatment of complex waste cutting emulsions.     

干湿法结合工艺回收废弃SCR脱硝催化剂中的钛、钒和钨

利用干湿法结合工艺实现废弃SCR脱硝催化剂中Ti、V和W元素的高效分离和浸出,提出成套废弃SCR脱硝催化剂中Ti、V和W的回收技术。以废弃SCR脱硝催化剂为研究对象,优选Ti、V和W元素最佳浸出工况,研究硫酸溶解法回收TiO₂和有机萃取法回收V₂O₅和WO₃的回收率与纯度。结果表明:酸浸还原浸钒最优工艺条件为温度140℃,液固比30∶1;钠化焙烧浸钨最优工艺条件为煅烧温度750℃,反应物与Na₂CO₃配比（质量比）为1∶1.5,在以上条件下V、W浸出率分别达到97.6%、93.6%。利用硫酸溶解法回收得到的TiO₂产物主要以锐钛矿晶型存在形式,在最佳焙烧温度750℃下,TiO₂回收率达到97.17%,纯度为95.35%。利用有机萃取法回收得到的V₂O₅和WO₃产物的回收率和纯度分别为72.47%、75.43%和93.25%、78.26%。     

预处理对园林垃圾混合物料联合厌氧发酵的影响

采用超声、微波及碱热预处理技术强化园林垃圾、厨余垃圾与果蔬垃圾联合厌氧发酵产气性能,并以未进行预处理的实验组作为对照。结果表明:4组实验pH值在2 d内迅速降低至7.24~7.45,反应后期可稳定在7.7~8.0,表明厌氧消化系统有较强的稳定性。挥发性脂肪酸（volatile fatty acids,VFA）浓度在第2~4天内达到最大值。乙酸和丙酸是4组实验中VFA的主要成分,两者比例之和在70%以上。VFA浓度在第13天后降低到500 mg/L以下,且以乙酸为主。氨氮（TAN）浓度在前4 d内出现一定波动,随后逐渐升高至2190~2410 mg/L。游离氨氮（FAN）浓度呈先降低后增加趋势,并在第13天后逐渐趋于稳定,为144~209 mg/L。沼气中甲烷比例在第2天后均超过50%,并在第11~12天时达到最大值61.4%~63.8%。修正的Gomperts模型模拟结果表明:预处理技术可缩短反应体系厌氧产沼的适应时间,提高前期产气速率。除此之外,超声预处理与碱热预处理可显著提高基质甲烷产率,由未处理时的396 mL/g分别提高到601,536 mL/g,而微波预处理使得反应体系甲烷产量略有降低。     

Development of a static test apparatus for evaluating the performance of three PM2.5 separators commonly used in China

PM_(2.5) separator directly affects the accuracy of PM_(2.5) sampling.The specification testing and evaluation for PM_(2.5) separator is particularly important,especially under China's wide variation of terrain and climate.In this study,first a static test apparatus based on polydisperse aerosol was established and calibrated to evaluate the performance of the PM_(2.5) separators.A uniform mixing chamber was developed to make particles mix completely.The aerosol concentration relative standard deviations of three test points at the same horizontal chamber position were less than 0.57%,and the particle size distribution obeyed logarithmic normal distribution with an R~2 of 0.996.The flow rate deviation between the measurement and the set point flow rate agreed to within ± 1.0% in the range of -40 to 50℃.Secondly,the separation,flow and loading characteristics of three cyclone separators(VSCC-A,SCC-A and SCC112) were evaluated using this system.The results showed that the 50% cutoff sizes(D_(50)) of the three cyclones were 2.48,2.47 and 2.44 μm when worked at the manufacturer's recommended flow rates,respectively.The geometric standard deviation(GSD) of the capture efficiency of VSCCA was 1.23,showed a slightly sharper than SCC-A(GSD = 1.27),while the SCC112 did not meet the relevant indicator(GSD = 1.2 ± 0.1) with a GSD = 1.44.The flow rate and loading test had a great effect on D_(50),while the GSD remained almost the same as before.In addition,the maintenance frequency under different air pollution conditions of the cyclones was summarized according to the loading test.     

杭州湾北岸36种挥发性有机物污染特征及来源解析

为研究杭州湾北岸VOCs（挥发性有机物）的浓度水平、组成特征、反应活性和潜在来源,采用GC-FID在线监测系统对杭州湾北岸环境大气中的36种VOCs开展了为期1 a（2017年12月-2018年11月）的连续观测,采用LOH（VOCs的·OH消耗速率）和OFP（O₃生成潜势）2种方法估算了大气VOCs的反应活性,并利用PMF（正定矩阵因子分解）和CPF（条件概率函数）模型分析其来源.结果表明:①φ（VOCs）小时平均值在冬季（26.47×10-9）最高,夏季（9.76×10-9）最低;全年φ（VOCs）小时平均值为21.24×10-9,其中烷烃、烯烃+炔烃、芳香烃、卤代烃的贡献率分别为33.24%、34.13%、15.63%、17.00%;φ（烷烃）、φ（芳香烃）和φ（卤代烃）呈较明显的昼夜变化特征,φ（烯烃）和φ（炔烃）无明显昼夜变化趋势.②大气VOCs的总LOH和OFP分别为9.39 s-1和220.57 μg/m3,KOH（·OH反应速率常数）和MIR（最大增量反应活性）系数的平均值分别为17.34×10-12 cm3/（molecule·s）和3.31;KOH和MIR系数的平均值分别与间/对-二甲苯的KOH和乙苯的MIR系数接近,表明大气VOCs的化学反应活性较强;VOCs关键活性物种为异戊二烯、乙烯、丙烯、甲苯、二甲苯和顺-2-丁烯.③特征物种相关性分析表明,杭州湾北岸大气存在老化现象,异戊烷和正戊烷受煤燃烧源影响较大,二甲苯和乙苯受溶剂排放源影响较大,甲苯和苯除受机动车尾气影响外,还受其他排放源影响.④PMF和CPF模型来源分析表明,大气VOCs主要来自石化工业源、燃料挥发源、生物质燃烧和煤燃烧源、机动车排放源和溶剂使用源,其中,机动车排放源主要来自西北方向,其他源主要来自西北、西和西南方向.研究显示,杭州湾北岸大气VOCs来源复杂,受周边工业区的影响较大.      

Analytical methods and environmental processes of nanoplastics

The degradation of plastic debris may result in the generation of nanoplastics (NPs). Their high specific surface area for the sorption of organic pollutions and toxic heavy metals and possible transfer between organisms at different nutrient levels make the study of NPs an urgent priority. However, there is very limited understanding on the occurrence, distribution, abundant, and fate of NPs in the environment, partially due to the lack of suitable techniques for the separation and identification of NPs from complex environmental matrices. In this review, we first overviewed the state-of-the-art methods for the extraction, separation, identification and quantification of NPs in the environment. Some of them have been successfully applied for the field determination of NPs, while some are borrowed from the detection of microplastics or engineered nanomaterials. Then the possible fate and transport of NPs in the environment are thoroughly described. Although great efforts have been made during the recent years, large knowledge gaps still exist, such as the relatively high detection limit of existing method failing to detect ultralow masses of NPs in the environment, and spherical polystyrene NP models failing to represent the various compositions of NPs with different irregular shapes, which needs further investigation.     

洱海北部入湖河流水质特征及其对北部湖区的影响

基于2016—2018年罗时江、弥苴河、永安江及洱海北部湖区监测数据分析,探讨洱海北部入湖河流污染变化特征及对北部湖区的影响。结果表明:1）"北三江"监测断面总磷、COD、氨氮浓度整体稳定在GB 3838—2002《地表水环境质量标准》Ⅱ—Ⅲ类标准限值内,年内污染物浓度变化表现出典型的农业面源污染特征,且受流域内产业模式等的综合影响;2）研究期间,河流首要污染物为TN,旱季次要污染物为COD,雨季为TP。雨季入湖负荷高于旱季,弥苴河污染负荷大于罗时江、永安江。"北三江"入湖TN和TP污染负荷分别占洱海允许负荷的50.1%和59.7%;3）入湖河流的磷元素输入是洱海北部湖区磷污染的重要来源。北部湖区污染物浓度对氮、磷入湖污染负荷相关性次月强于当月,响应存在延迟。筛选环境友好型种植模式,控制"北三江"氮磷入湖负荷,有利于保护洱海水环境。     

不同制备温度下污泥生物炭对Cr(Ⅵ)的吸附特性

以城市剩余污泥为原料,于300,400,500,600 ℃温度条件下制备生物炭,通过单因素静态吸附实验探讨制备温度对生物炭吸附Cr（Ⅵ）的影响。结果表明:在500 ℃以内随着温度上升制备的生物炭对Cr（Ⅵ）的吸附量增加,制备温度高于500 ℃后变化不明显;扫描电镜（SEM）、比表面积（BET）、傅里叶红外光谱（FTIR）表征结果显示,热解温度对生物炭表面形貌和官能团组成有显著影响;等温模型及动力学拟合结果表明,生物炭吸附Cr（Ⅵ）为单分子层吸附、物理-化学复合吸附。热解温度对污泥制备生物炭吸附Cr（Ⅵ）的性能有显著影响,最佳制备温度为500 ℃,在此条件制备的生物炭对Cr（Ⅵ）的理论吸附量可达7.93 mg/g。