基于总过氧自由基测量的2022北京冬奥会期间北京市地表臭氧来源分析

2022年2月第24届冬季奥林匹克运动会期间,基于宽带腔增强吸收光谱-化学放大法和化学发光法分别测量总过氧自由基(RO_(2)^(*))和一氧化氮(NO)浓度,并用于计算北京市近地面大气臭氧光化学生成速率(P(O_(3))).结合相关污染物浓度数据及气象参数对本地臭氧生成特征进行了分析.结果表明:RO_(2)^(*)浓度变化呈明显的日变化规律,观测期间RO_(2)^(*)的日均峰值浓度为8×10^(-12).日间(7:00-18:00)P(O_(3))呈现明显的日变化规律,观测期间平均P(O_(3))最高值为26×10^(-9)·h^(-1),变化范围为(3~26)×10^(-9)·h^(-1).此外,P(O_(3))对NO浓度的变化较为敏感,NO浓度的升高促进了大气化学反应的发生,加快了近地面臭氧的累积.

基于总过氧自由基观测研究合肥市西郊夏季O_(3)生成特征

2020年8月利用化学放大法对合肥市西郊大气总过氧自由基RO_(2)^(*)·(RO_(2)·+HO_(2)·)体积分数进行监测,并结合O_(3)和其前体物,分析了过氧自由基体积分数、O_(3)生成速率和O_(3)生成对前体物的敏感性.结果表明,观测期间总过氧自由基体积分数的日均值呈典型的单峰型变化,12:00左右出现最高值,日间峰值体积分数为43.8×10^(-12),日间RO_(2)^(*)·与太阳辐射强度、温度和O_(3)呈明显的相关性.利用实测RO_(2)^(*)·和NO,获得合肥市西郊夏季O_(3)生成速率,日间峰值为10.6×10^(-9)h^(-1),O_(3)生成速率对NO变化更为敏感.基于大气自由基和NO_(x)(NO+NO_(2))反应去除速率占比(Ln/Q),对合肥市西郊夏季O_(3)生成敏感进行了分析,结果显示O_(3)生成敏感具有明显日变化.早晨O_(3)生成为VOCs控制区,上午O_(3)生成为VOCs-NO_(x)协同控制区,下午转变为NO_(x)控制区.

Oxidation Stability of Camellia Oil During Refining

In this paper, the crude camellia oil extracted by cold pressing and deacidified oil, decolorized oil, dewaxed oil and finished tea oil obtained in different refining stages were studied. The changes of acid value, peroxide value and free radical scavenging ability of camellia oil in each stage were compared and analyzed.The results showed that the total phenol content of crude oil was the highest, and the total phenol content of alkali refined crude oil decreased significantly. After dewaxing, the total phenol concentration of camellia oil increased by 63.5%. The reason may be that low temperature conditions contributed to the recovery of phenolic structure in camellia oil, and without the influence of alkaline solution, the damage degree of phenolic substances was greatly reduced, thus elevating the total phenol content. The lowest peroxide value of camellia oil was observed in the alkali-refining deacidification stage, which decreased by 29.3%. Crude oil had the highest acid value and concentration of antioxidant substances. After alkali-refining deacidification,the acid value and the concentration of antioxidant substances dropped by 85.3%and 88.9%, respectively. Total phenols had the strongest correlation with acid value,followed by free radical scavenging ability, and the correlation with peroxide value was not obvious.