轿车车速表指示误差研究

汽车驾驶者准确掌握真实车速，对车辆的行驶安全性和减少道路交通事故的发生及其危害程度有着极为重要的影响。因此，对驾驶者借以了解汽车行驶速度的车速表，其指示值是否准确及指示误差的大小必须加以研究。本文运用数理统计工具及样本实测数据，选取上海桑塔纳ＬＸ轿车车速表检验值进行统计规律研究，给出其分布参数，建立相应数学模型，指明其误差情况，对于深入了解轿车车速表指示误差统计规律，保证车辆的行驶安全性，改进车速表设计均具有十分重要的意义。     

出口贸易和FDI加剧了资源型城市的环境污染吗?——基于中国285个地级城市面板数据的经验研究

论文沿用经典EKC分析框架,在现有资源型城市环境污染研究基础上加入了出口贸易开放度、利用外资水平、研发水平及污染治理水平等因素。分析基于2005—2012年中国285个地级城市（包括115个资源型城市和170个非资源型城市）的面板数据,考虑可能存在的内生性问题,使用固定效应模型和工具变量GMM估计的方法,实证考察了出口贸易和FDI是否加剧了资源型城市的环境污染。研究表明,出口贸易显著地加剧了中国资源型城市的环境污染,FDI则在一定程度上加剧了环境污染;中国主要地级城市的人均收入和环境污染呈“倒U型”的库兹涅茨关系;环境影响因素对各类资源型城市污染排放产生的作用具有异质性,原因在于不同类型城市存在不同的资源依赖程度和技术水平。最后,论文对中国现阶段部分有关资源开采与相关外商投资、资源型城市发展等政策与规划及其存在的问题进行整理,并根据经验研究结论得到相关政策启示。     

Occurrence and hydrogeochemical characteristics of high-fluoride groundwater in Xiji County,southern part of Ningxia Province,China

Environmental Geochemistry and Health - High-F− groundwater is widely distributed in Xiji County, which endangers the safety of drinking water. In order to evaluate the key factors...     

三氯生光降解动力学过程及其光降解产物生物毒性评价

光化学降解是药品及个人护理用品(PPCPs)在环境中转化归趋的重要途径之一,同时光解过程对该类化合物的生态毒性产生重要影响。本研究以抗菌药物三氯生为模型化合物,研究在紫外光照射下,三氯生初始浓度、腐殖酸含量、pH、光强对其光降解动力学的复合影响。采用发光细菌、羊角月牙藻2个不同营养级生物的毒性响应变化评价三氯生母体化合物及光降解过程中毒性变化。研究表明:三氯生光降解遵循准一级反应动力学。初始浓度为10μmol·L~(-1)、腐殖酸含量为0 mg·L~(-1),初始p H值为11、光强为0.44 m W·cm-2时,该光化学降解反应体系三氯生有最高的反应速率和降解效率。三氯生光降解过程中产生了对受试生物有较高抑制作用的中间产物,随着光降解时间的延长,光降解中间产物的毒性逐渐降低,在光降解30 min后无显著毒性。     

太湖北部表层沉积物重金属污染及其生物毒性研究

在分析太湖北部梅梁湾、竺山湾和贡湖表层沉积物和野生铜锈环棱螺体内重金属残留水平基础上,利用潜在生态危害指数法评价了区域重金属污染的潜在生态风险,并利用综合污染指数法评价了野生铜锈环棱螺受重金属污染的状况。研究结果表明,3个区域表层沉积物孔隙水的生物综合毒性处于低毒到中毒水平,而表层沉积物重金属污染均处于较低的生态风险,但3个区域的野生铜锈环棱螺体内重金属的综合污染指数处于中度到重度的污染水平。由此可以得出太湖北部沉积物重金属污染对底栖生物仍具有一定的潜在生态风险。     

The source and transport of bioaerosols in the air: A review

• Emission of microbe from local environments is a main source of bioaerosols. • Regional transport is another important source of the bioaerosols. • There are many factors affecting the diffusion and transport of bioaerosols. • Source identification method uncovers the contribution of sources of bioaerosols. Recent pandemic outbreak of the corona-virus disease 2019 (COVID-19) has raised widespread concerns about the importance of the bioaerosols. They are atmospheric aerosol particles of biological origins, mainly including bacteria, fungi, viruses, pollen, and cell debris. Bioaerosols can exert a substantial impact on ecosystems, climate change, air quality, and public health. Here, we review several relevant topics on bioaerosols, including sampling and detection techniques, characterization, effects on health and air quality, and control methods. However, very few studies have focused on the source apportionment and transport of bioaerosols. The knowledge of the sources and transport pathways of bioaerosols is essential for a comprehensive understanding of the role microorganisms play in the atmosphere and control the spread of epidemic diseases associated with them. Therefore, this review comprehensively summarizes the up to date progress on the source characteristics, source identification, and diffusion and transport process of bioaerosols. We intercompare three types of diffusion and transport models, with a special emphasis on a widely used mathematical model. This review also highlights the main factors affecting the source emission and transport process, such as biogeographic regions, land-use types, and environmental factors. Finally, this review outlines future perspectives on bioaerosols.     

栉孔扇贝内参基因稳定性研究

合适的内参基因对准确定量目标基因表达水平非常重要。利用实时定量聚合酶链式反应(RT-qPCR)分析了不同发育阶段和雌激素暴露条件下栉孔扇贝性腺组织中β-actin、β-TUB、EF-lα、18SrRNA和GAPDH5个内参基因的表达水平,并利用RefFinder软件对其表达稳定性进行了分析。结果表明:在所考察的内参基因中,EF-lα在栉孔扇贝不同发育阶段和雌激素暴露下的表达均最为稳定,可作为定量目标基因表达水平的内参基因之一。     

Sensitivity of air quality model prediction to parameterization of vertical eddy diffusivity

This paper investigates the effects of vertical eddy diffusivities derived from the 3 different planetary boundary layer (PBL) schemes on predictions of chemical components in the troposphere of East Asia. Three PBL schemes were incorporated into a regional air quality model (RAQM) to represent vertical mixing process and sensitivity simulations were conducted with the three schemes while other options are identical. At altitudes <2km, all schemes exhibit similar skill for predicting SO₂ and O₃, but more difference in the predicted NO_x concentration. The Gayno–Seaman scheme produces the smallest vertical eddy diffusivity (Kz) among all schemes, leading to higher SO₂ and NO_x concentrations near the surface than that from the other 2 schemes. However, the effect of vertical mixing on O₃ concentration is complex and varies spatially due to chemistry. The Gayno–Seaman scheme predicts lower O₃ concentrations than the other two schemes in the parts of northern China (generally VOC-limited) and higher ones in most parts of southern China (NO_x-limited). The Byun and Dennis scheme produces the largest mixing depth in the daytime, which bring more NO_x into upper levels, and the mixing depth predicted by the Gayno–Seaman scheme is the smallest, leading to higher NO_x and lower O₃ concentrations near the surface over intensive emission regions.     

静力荷载作用下纤维材料增强路基性能的试验研究

分别采用现场铁路路基填料及掺量为0.3%的聚丙烯纤维改良填料构筑室内小型路基,通过对路基顶部施加不同的分级静载,对比研究两种不同填料对路基内应力分布规律和沉降变形特性的影响,进而判断纤维材料作为改良措施运用于路基沉降控制的可行性与有效性。试验结果表明:相对于现场填料路基,纤维改良措施加快了应力在路基中沿深度的扩散速度;应力加载至100 kPa时,两种填料路基的沉降变形规律相似,路基不同深度处的沉降随着基顶作用荷载的增加呈非线性增大;应力达到200 kPa时,纤维改良路基60 cm深度范围内的沉降曲线出现反转点,曲线形状近似拉长的s形;较于现场填料路基,纤维改良措施使基顶沉降分别减少了30.3%及35.4%;在高应力、大变形趋势条件下,纤维材料对路基沉降的控制效果会更好。     

城市噪声污染控制实例

XX城市噪声污染控制立足于《XX城市近、中、远期总体规划》和《XX市环境保护“十一五”规划》,有利于城市环境噪声的综合整治和科学管理,与城市环境功能区划相协调,结合城市特征和噪声污染现状,提出控制目标、控制方案、可行性分析及保障措施。力求科学、合理、实用、可行。