Traffic restrictions during COVID-19 lockdown improve air quality and reduce metal biodeposition in tree leaves

The coronavirus disease (COVID-19) has had a great global impact on human health, the life of people, and economies all over the world. However, in general, COVID-19´s effect on air quality has been positive due to the restrictions on social and economic activity. This study aimed to assess the impact on air quality and metal deposition of actions taken to reduce mobility in 2020 in two different urban locations. For this purpose, we analysed air pollution (NO₂, NO, NO_x, SO_2, CO, PM_10, O₃) and metal accumulation in leaves of Tilia cordata collected from April to September 2020 in two cities in northern Spain (Pamplona-PA and San Sebastián-SS). We compared their values with data from the previous year (2019) (in which there were no mobility restrictions) obtained under an identical experimental design. We found that metal accumulation was mostly lower during 2020 (compared with 2019), and lockdown caused significant reductions in urban air pollution. Nitrogen oxides decreased by 33%−44%, CO by 24%−38%, and PM₁₀ by 16%−24%. The contents of traffic-related metals were significantly reduced in both studied cities. More specifically, significant decreases in metals related to tyre and brake wear (Zn, Fe, and Cu) and road dust resuspension (Al, Ti, Fe, Mn, and Ca) were observed. With these results, we conclude that the main reason for the improvement in urban air pollutants and metals was the reduction in the use of cars due to COVID-19 lockdown. In addition, we offer some evidence indicating the suitability of T. cordata leaves as a tool for biomonitoring metal accumulation. This information is relevant for future use by the scientific community and policy makers to implement measures to reduce traffic air pollution in urban areas and to improve environmental and human health.     

锯末对生物修复荧蒽和芘污染土壤的强化作用及影响因素

通过土壤微宇宙培养试验,研究了锯末尺寸、添加量和种类等因素对荧蒽特效降解菌MC(Mycobacterium flavescens)修复污染土壤(潮土、红壤、黑土、黄棕壤和水稻土)的效果.结果表明:锯末联合降解菌MC修复荧蒽污染的黄棕壤效果较好,优化条件下25 d荧蒽降解率为42.63％ ±1.05％;该联合修复对黑土和...     

水压力环境中混凝土经历循环荷载后的抗压强度

研究了水压力环境中混凝土在经历循环荷载后的动态压缩强度，分析了水压力和循环次数对混凝土强度的影响。试验应变速率为10^-5/s、10^-4/s、10^-3/s和10^-2/s，水压为0~10 MPa。试验结果表明，在不同水压力下饱和混凝土的强度都随应变速率提高而增加，也随水压力提高呈增加地趋势。在相同水压力下，应变速率越高，混凝土强度提高越显著。饱和混凝土经过循环荷载后，其强度随荷载循环次数的增加呈现出先提高后降低的现象。应变速率越高，混凝土强度最大时所对应的荷载循环次数也相应增加。还构建了饱和混凝土强度与应变速率、水压力的关系，其与试验数据吻合较好。进一步引入了管道孔隙模型，并基于汞压法的原理和孔隙分布特点，考虑混凝土孔隙的微观结构解释了孔隙水对混凝土强度的作用机理。     

新型RC网格式框架结构墙体试验研究

为研究新型RC网格式框架结构承载力、滞回曲线、骨架曲线、延性、刚度和耗能能力等受力性能，进行了3榀1/5缩尺墙体模型在低周反复水平荷载作用下的试验.试验结果表明：新型RC网格式框架结构表现出框架结构的受力特性，试件各层均出现反弯点，为剪切型破坏；滞回曲线饱满，有较强的耗能能力；延性比常规框架好；试件屈服后，刚度退化较快，临近破坏时，刚度退化缓慢.考虑材料、几何和接触非线性，运用有限元软件ANSYS对相同条件下填充磷石膏的网格式框架结构墙体进行计算，有限元计算屈服时墙体顶点最大水平位移比试验大约5.8%，与试验结果吻合较好.新型RC网格式框架结构是介于框架结构和密肋网格式剪力墙结构受力性能之间的一种结构形式，适用于建造高层住宅及办公建筑等.     

农产品中环境污染物的控制标准与食物安全体系

论述了农产品中主要污染物的种类、制订我国农产品中污染物控制标准的意义及制订我国农产品中农药残留最大限量应注意的问题。     

畜禽粪便堆肥大气污染物排放及其控制研究进展

针对畜禽粪便好氧堆肥过程中大气污染物的排放特性及其控制开展了国内外文献调研。畜禽粪便好氧堆肥过程中会产生CH₄、N₂O、CO₂等温室气体及NH₃、H₂S、VOCs等恶臭气体，其中CH₄、N₂O、NH₃是堆肥过程排放的主要大气污染物。堆肥过程中大气污染物的排放主要受原料、堆肥方式、氧含量等影响。源头控制技术和末端控制技术可实现堆肥过程中大气污染物的有效减排。源头控制技术主要通过优化堆肥工艺、外加添加剂等实现污染物的源头减量；末端控制技术主要采用生物法、化学洗涤法、吸附法等去除废气污染物。在文献调研基础上，提出了“源头控制+末端治理”的堆肥大气污染物全过程控制技术路线。      

Pollination of urban meadows – Plant reproductive success and urban-related factors influencing frequency of pollinators visits

Pollination is a key ecological service for human food security and the reproduction of the majority of flowering plants. This plant-animal interaction is crucial in both wild and urban habitats, however, increasing urbanization and change in land use alter these interactions. The concerns regarding pollination have led to numerous efforts aimed at improving the quality of wildlife in cities, however, understanding the importance of these activities warrants further research. In Warsaw, the Polish capital, we analyzed the influence of urban-related factors such as floral resource richness, the proportion of green areas in the proximity of foraging sites, air pollution or temperature on plant-pollinator interaction in 14 meadows. We also analyzed the reproductive success and the heterospecific pollen transfer in the case of plants growing in the meadows. Our study revealed that the frequency of visits to flowers was related to city-related factors, but the reaction varied among different groups of pollinators. For example, bumblebees were negatively influenced by higher air pollution, while the rest of the flower visitors were not, Syrphidae flies were more frequent flower visitors when the proportion of green area was higher in the buffer of 150 m, while we did not observe this tendency in other groups of flower visitors. Plants growing in Warsaw meadows were frequently visited and effectively pollinated - urban pollinator assemblages seem to provide sufficient pollination services to plants growing in the city. Species-rich communities were not a threat to pollination; we found mostly conspecific pollen grains on the stigmas of the studied plant species. The results of our study show that species-rich communities make a valuable contribution to pollinator conservation. The conservation activities, however, should be adjusted to the target group of pollinators, since different groups of flower visitors respond differently to urban-related factors studied.     

基于多体模型的重型车辆对路面动载特性

利用SIMPACK软件分别建立重型车辆前悬架、后平衡悬架、转向系统和轮胎模型等,在此基础上建立重型载货汽车整车多体动力学模型,并采用谐波叠加法构建随机路面,建立了一个可考虑路面不平度的重型车辆对路面动载特性研究平台,利用该平台探讨了重型车辆轮胎三向动载荷与路面不平度、行驶速度的关系.仿真结果表明:前轴轮胎纵向动载荷小于中、后轴轮胎纵向动载荷,前轴轮胎侧向和法向动载荷大于中、后轴轮胎侧向和法向动载荷,中、后两轴轮胎动载荷相差很小;路面在A～D级、行驶速度为60～90 km/h时,前轴车轮法向动载系数大于中、后轴车轮法向动载系数,前轴轮胎法向作用力小于中、后轴轮胎法向作用力.     

叶表观症状识别在大气污染农业环境损害鉴定中的应用

叶表观症状是农作物对大气污染物最直接的环境响应特征，可用作大气中污染物的植物指示和损害程度确定。本文梳理了5种典型大气污染物对农作物叶表观伤害症状的特征和差异，提出通过农作物叶表观症状识别致害污染物的想法和思路、具体的鉴别鉴定技术以及利用叶表观症状识别技术进行识别的工作程序，并在广西田东县某村芒果受损典型鉴定案例中进行了实践应用。研究表明，叶表观症状识别技术具有快速、有效辨识特征污染物，缩小线索摸排范围，锁定污染源等优点，是一种直观、便捷、易操作、成本低、实用性强的污染损害识别技术，可为非专业人士、行政执法人员快速发现、锁定致害源提供技术支撑。