藻类及其分泌物对混凝过程的影响研究

采用纯萍进行烧杯混凝试验，考察了试验藻种及其分泌物对混凝过程的影响，试验发现：藻类对混凝过程的影响与藻的种类，生长阶段及藻浓度有关；一般说来，藻类在浓度较低时，对混凝过程吸不同程度的促进作用，而在高浓度时，对混凝过程有不同程度的干扰。增加混凝剂投加量，调节ｐＨ，耐加氯可以减弱藻类及其分泌物对混凝过程的影响。     

久效磷对扁藻的生理效应

运用急性毒性实验和生化分析方法对久效磷胁迫下扁藻细胞的生理变化进行了研究，结果表明：（１）久效磷对扁藻生长有较强的抑制作用。其７２ｈ半抑制剂量为１．４６ｍｇ／Ｌ；（２）久效磷胁迫下，扁藻细胞的３种大分子物质－－蛋白质、ＤＮＡ和ＲＮＡ的含量降低；（２）久效磷引起扁藻叶绿素ａ的降解和光合速率的下降，这说明久效磷处理抑制了扁藻的生理代谢。     

重大活动空气质量保障预报会商机制及经验探讨

重大活动空气质量保障预报会商已经成为保障过程中的重要环节,旨在以精细化空气质量预报为环境管理部门制定高效可行的区域大气污染管控措施提供关键技术依据。预报会商机制可有效规范区域联动预报会商的开展,在多个重大活动空气质量保障中,预报会商机制已日益完善,尤其是在强化立体化监测网、开展多技术组协同作业、建立多维预报会商流程、提升多种重点污染物预报能力等方面积累了大量宝贵的实践经验。该文首次系统性探讨国内空气质量保障预报会商机制和经验,以期为今后承办重大活动的地区开展空气质量保障预报会商提供借鉴。     

基于城市大气环境荷载指数的大气污染排放变率估算

基于地面气象观测资料计算大气自净能力指数ASI,和环境监测站的实测PM_2.5浓度数据,利用城市大气环境荷载指数研究分析了2个时段单位人口的污染物排放率的变化,以及2013年9月~2019年2月京津冀及周边主要城市气象条件和减排措施对空气污染物浓度变化的作用.结果显示：秋冬季节污染物的削减力度明显大于春夏季.2014年秋冬季有74.5%城市实现减排,区域平均减排12.6%,减排初见成效;2017年和2018年秋冬季,京津冀及周边地区持续大幅减排,其中京津冀区域相对基准年分别减排54.0%和47.7%.长治市在2014~2017年秋冬季排放率均高于基准年,直至2018年冬季始实现减排27.6%;石家庄市排放率变化幅度波动较大,2016年冬季相比2014年冬季增加68.2%,今后区域污染物防控需要重点关注以上2个城市.城市大气环境荷载指数能够客观定量反映出典型减排时段的排放率变化方向和幅度,是一种评估气象条件和排放控制措施二者对污染物浓度变化各自作用的简单有效方法.     

唐山上空CO2和CO浓度特征的飞机探测研究

为研究唐山城市上空CO₂与CO浓度时空分布,进一步定量其碳排放,于2018年11月~2019年3月,利用运十二飞机搭载高精度温室气体分析仪和相关辅助设备,对唐山市上空（200m~4600m）CO₂与CO浓度进行飞机探测.探测期间共取得6组CO₂和CO浓度垂直廓线数据.结果表明：探测期间CO₂浓度变化范围406×10^-6~453×10^-6,CO浓度变化范围27×10^-9~1135×10^-9.夜间探测有明显的混合层存在时,CO₂与CO浓度分布在混合层内有向上聚集现象,且在混合层顶均达到最大值;白天探测无明显的混合层存在时,浓度整体随高度增加而减小.在探测期间整层的平均风力小于4级时,CO₂和CO浓度极显著相关,CO₂和CO浓度比变化范围32.2~43.9.以2019年2月23日白天的架次为案例进行分析,微风条件下空气团经过城市后,CO₂和CO浓度均有所增加,显示当日唐山是CO₂和CO的源,结合质量平衡法或大气反演模式可以进一步估算城市CO₂和CO排放量.     

缸内直喷汽油机排放PM_(2.5)的理化特征及影响因素

通过发动机台架实验研究了发动机的转速、负荷对缸内直喷(GDI)汽油机排放PM_(2.5)的排放水平、化学组成及颗粒物数浓度等的影响.结果表明:GDI汽油机排放PM_(2.5),OC,EC的排放因子分别为(49.8±28.2),(21.6±6.9),(11.4±10.8)mg/kg.低转速时,PM_(2.5)排放量随着负荷的增加先减少后增加,中、高转速时随着负荷的增加逐渐增加.碳质气溶胶是GDI汽油机排放的PM_(2.5)的主要组成成分,有机物(OM)和元素碳(EC)分别占PM_(2.5)的45.6%~70.6%和7.9%~42.7%.PM_(2.5)数浓度呈核态(10nmDp30nm)和积聚态(30nmDp200nm)的双峰分布,数浓度排放量比进气道喷射(PFI)汽油机高2个数量级,不同转速下积聚态颗粒数浓度随着负荷的增加而增加.     

Distinct potential aerosol masses under different scenarios of transport at a suburban site of Beijing

In order to evaluate the secondary aerosol formation potential at a suburban site of Beijing,in situ perturbation experiments in a potential aerosol mass(PAM) reactor were carried out in the winter of 2014.The variations of secondary aerosol formation as a function of time,OH exposure,and the concentrations of gas phase pollutants and particles were reported in this study.Two periods with distinct secondary aerosol formation potentials,marked as Period Ⅰ and Period Ⅱ,were identified during the observation.In Period Ⅰ,the secondary aerosol formation potential was high,and correlated well to the air pollutants,i.e.,SO_2,NO_2,and CO.The maximal secondary aerosol formation was observed with an aging time equivalent to about 3 days of atmospheric oxidation.In period Ⅱ,the secondary aerosol formation potential was low,with no obvious correlation with the air pollutants.Meanwhile,the aerosol mass decreased,instead of showing a peak,with increasing aging time.Backward trajectory analysis during the two periods confirmed that the air mass in Period Ⅰwas mainly from local sources,while it was attributed mostly to long distance transport in Period Ⅱ.The air lost its reactivity during the long transport and the particles became highly aged,resulting in a low secondary aerosol formation potential.Our experimental results indicated that the in situ measurement of the secondary aerosol formation potential could provide important information for evaluating the contributions of local emission and long distance transport to the aerosol pollution.     

Changes in visibility with PM2.5 composition and relative humidity at a background site in the Pearl River Delta region

In fall–winter, 2007–2013, visibility and light scattering coefficients(b sp) were measured along with PM_(2.5)mass concentrations and chemical compositions at a background site in the Pearl River Delta(PRD) region. The daily average visibility increased significantly(p 0.01) at a rate of 1.1 km/year, yet its median stabilized at ~13 km. No haze days occurred when the 24-hr mean PM_(2.5)mass concentration was below 75 μg/m~3. By multiple linear regression on the chemical budget of particle scattering coefficient(b sp), we obtained site-specific mass scattering efficiency(MSE) values of 6.5 ± 0.2, 2.6 ± 0.3, 2.4 ± 0.7 and 7.3 ± 1.2 m2/g,respectively, for organic matter(OM), ammonium sulfate(AS), ammonium nitrate(AN) and sea salt(SS). The reconstructed light extinction coefficient(b ext) based on the Interagency Monitoring of Protected Visual Environments(IMPROVE) algorithm with our site-specific MSE revealed that OM, AS, AN, SS and light-absorbing carbon(LAC) on average contributed 45.9% ± 1.6%,25.6% ± 1.2%, 12.0% ± 0.7%, 11.2% ± 0.9% and 5.4% ± 0.3% to light extinction, respectively.Averaged b ext displayed a significant reduction rate of 14.1/Mm·year(p 0.05); this rate would be 82% higher if it were not counteracted by increasing relative humidity(RH) and hygroscopic growth factor(f(RH)) at rates of 2.5% and 0.16/year-1(p 0.01), respectively, during the fall–winter, 2007–2013. This growth of RH and f(RH) partly offsets the positive effects of lowered AS in improving visibility, and aggravated the negative effects of increasing AN to impair visibility.     

基于贝叶斯方法的竖井中性面模型参数不确定性研究

随着高层建筑越来越多,其发生火灾的风险也越来越大,火灾烟气是导致火势蔓延和人员伤亡的主要原因,因此高层建筑防排烟设计问题可谓重中之重。建筑中性面的性质决定了其在防排烟设计中的关键地位,通过对建筑中性面位置的研究来优化建筑防排烟设计,减少火灾烟气对人和建筑的危害具有重要的意义。在前人工作的基础上,利用场模拟的方法得到样本值,并引入贝叶斯概率方法量化模型参数的不确定性,分析了竖井结构单一参数的不确定性对中性面位置分布的影响。旨在为火灾安全工程设计和竖井模型实验台设计,以及建筑竖向通道防排烟设计提供一定的参考。     

固体废物中氰化物全量的测定方法研究

建立了固体废物中氰化物全量的测定方法.选择金矿、电镀污泥等典型固废实际样品为研究对象,探讨了氰化物的全量测定结果与提取液pH的关系,确定使用pH值>12的氢氧化钠水溶液做为全量提取液.提取液中氰化物的含量采用硝酸银滴定法、异烟酸-吡唑啉酮或异烟酸-巴比妥酸分光光度法进行测定.方法检出限分别为0.24、0.03及0.02 mg/kg,实际固废样品加标回收率范围在92.2%~107%,6次测定结果的RSD为1.5%~11.7%.该方法检出限低、回收率高,精密度和准确度良好,适用于固体废物中氰化物的全量测定.