上海大气中气相和颗粒相羰基化合物研究

 为探究大气中羰基化合物的质量浓度水平及变化规律, 利用滤膜系统(FP)同时采集大气中颗粒相和气相羰基化合物, FP系统由3 层47 mm 滤膜组成, 其中, 第1 层滤膜用于收集颗粒相羰基化合物, 第2 层和第3 层滤膜涂布五氟苄基羟胺(PFBHA)衍生剂, 用于收集气相羰基化合物。PFBHA 的涂布量为12 μmol、采样流速4 L/min, 每个样品采集4 h。采集后的样品用正己烷提取。利用该方法对上海市大气中的羰基化合物进行研究, 结合气相色谱/质谱仪(GC/MS), 分析大气中羰基化合物浓度的日变化、季节变化以及气相-颗粒相分配规律。研究结果表明:1)上海市大气中15 种目标化合物均能检测到, 包括13 种单羰基化合物和2 种二羰基化合物;2)上海大气中羰基化合物具有明显的日变化和季节变化, 气相羰基化合物的浓度在中午达到最大值, 颗粒相则相反;夏季羰基化合物的总质量浓度((33.8±15.9)μg/m³)显著高于冬季和春季(分别为(10.5±5.0)和(14.0±7.0)μg/m³);3)羰基化合物的气粒分配规律表现为与温度呈正相关、与相对湿度呈负相关。本研究表明, FP 系统可替代AD-FP(环形溶蚀器-滤膜系统)同时采集大气中气相和颗粒相中的羰基化合物, 易于携带, 为羰基化合物的野外观测提供便利。

Gaseous and particulate carbonyl compounds in Shanghai ambient air

In order to explore the concentration levels and variations of carbonyl compounds in the atmosphere, a filter pack (FP) system was used to collect gaseous and particulate carbonyl compounds simultaneously in Shanghai ambient air. There are three 47 mm filters in the FP system. Particulate carbonyls were collected on the first filter directly and then the gaseous carbonyls were collected on the second and third filters impregnated with PFBHA. The coating amount of PFBHA was 12 μmol, the sampling flow was 4 L·min^-1 for 4 hours. The filter samples were extracted by hexane and injected into the GC/MS system. Seasonal and diurnal variations of carbonyl compounds as well as the gas-particle partitioning were studied. The results showed as follows: 1) 15 target carbonyl compounds are all detected in Shanghai ambient air, including 13 mono-carbonyls and 2 dicarbonyls; 2) the carbonyl compounds exhibit significant seasonal and diurnal variations with higher concentrations in summer, the concentrations of gaseous carbonyls reach the maximum at noon while the particle phases achieve the minimum values at the same time; the total concentration of carbonyls is 33.8±15.9 μg/m³ in summer, significantly higher than the levels in winter (10.5±5.0 μg/m³) and spring (14.0±7.0 μg/m³); 3) gas-particle partitioning of carbonyl compounds is found to be positively correlated with ambient temperature while negatively with relative humidity. Compared to the annular denuder-filter pack (AD-FP) system, the FP system is more suitable for field observation.