西安市采暖季过渡期高时间分辨率细颗粒物组分特征及来源解析

受到供暖影响,北方城市秋冬季的大气细颗粒物(PM_2.5)浓度升高,空气污染加剧.利用气溶胶化学组分监测仪、七波段黑碳仪以及大气多金属元素在线监测仪于2019年10月25日至11月17日在西安市开展高时间分辨率PM_2.5化学组分在线监测,分析采暖季过渡期PM_2.5污染特征,同时结合正定矩阵因子分解模型解析PM_2.5来源.结果表明,观测期间ρ(PM_2.5)平均值为(78.3±38.5)μg·m^-3,主要化学组分为有机物(OA)、二次无机离子(SIA)和粉尘,其占比分别为38.7%、31.6%和21.2%,其中ρ(SO₄^2-)、ρ(NO₃^-)和ρ(NH₄⁺)平均值分别为(4.0±3.1)、(14.9±13.7)和(5.8±4.8)μg·m^-3,主要金属ρ(K)、ρ(Ca)和ρ(Fe)平均值分别为(1.0±0.4...     

弹簧应力松弛载荷的在线测量新方法

目的 准确高效地测量弹簧在应力松弛试验过程中的载荷。方法 针对周期试验法中繁琐的拆装工作和连续试验法中测试效率偏低的难点问题，以周期试验法中可以让“弹簧的总形变量在短时间内发生变化”的事实为依据，通过驱使待测弹簧进一步发生少量变形，将待测弹簧承受的准不变载荷转换为缓冲弹簧的连续变化载荷进行测量。测量后分别对直线进行拟合，便可求得驱动力F0，进而可以计算出待测弹簧处于装夹状态时所承受的载荷。结果 得到了一种在应力松弛过程中测量弹簧载荷的新方法，并结合螺旋压缩弹簧的结构特点，介绍了该方法的2种实现方式。当置信度为0.95时，测试结果的置信区间在±2%内，说明测量结果具有较高的可信度。结论 实践应用表明，在周期试验法中，采用该方法能够避免繁琐的拆装过程，有利于降低人为误差；在连续试验法中，采用该方法可以提高测试效率，从而有效地解决应力松弛试验中的载荷测试难题。     

离子色谱-串联质谱测定地表水中高氯酸盐

采用离子色谱-串联质谱测定地表水中高氯酸盐,在US EPA相应分析方法的基础上进行了优化,以阴离子交换柱为分析柱,氢氧化钾为淋洗液,经抑制电导检测后通过阀切换将检测液中大量弱保留的阴离子切到废液后再将强保留的高氯酸盐切入质谱,电喷雾负离子模式电离,选择离子反应监测(SIM)高氯酸盐。方法检出限达0.031μg/L,实际样品相对标准偏差为2.26%~4.45%,加标回收率为93.0%~98.0%。四川省内主要河流的高氯酸盐浓度在未检出~68.0μg/L之间,高氯酸盐污染不容忽视。     

Graphene-based photocatalytic nanocomposites used to treat pharmaceutical and personal care product wastewater: A review

Photocatalytic technology has been widely studied by researchers in the field of environmental purification. This technology can not only completely convert organic pollutants into small molecules of CO₂ and H₂O through redox reactions but also remove metal ions and other inorganic substances from water. This article reviews the research progress of graphene-based photocatalytic nanocomposites in the treatment of wastewater. First, we elucidate the basic principles of photocatalysis, the types of graphene-based nanocomposites, and the role of graphene in photocatalysis (e.g., graphene can accelerate the separation of photon-hole pairs and increase the intensity and range of light absorption). Second, the preparation, characterization, and application of composites in wastewater are introduced. We also discuss the kinetic model of the photocatalytic degradation of pollutants. Finally, the enhancement mechanism of graphene in terms of photocatalysis is not completely clear, and graphene-based photocatalysts with high catalytic efficiency, low cost, and large-scale production have not yet appeared, so there is an urgent need for more extensive and in-depth research.