北京大气颗粒物和重金属铅干沉降通量及季节变化

Atmospheric Dry Deposition Fluxes and Seasonal Variations of Particulate Matter and Lead in Urban Beijing

为了解大气颗粒物和重金属铅(Pb)干沉降通量的变化规律,采用聚氨酯泡沫膜片为代用面联合干湿沉降自动观测设备,于2013年12月~2014年11月在北京城区采集了颗粒物干沉降,利用微波消解和电感耦合等离子体质谱仪对样品中全量Pb和水溶性Pb进行了测试分析.结果表明,北京大气颗粒物和Pb干沉降通量分别为0.84 t·(hm^2·a)^(-1)和7.56mg·(m^2·a)^(-1),呈现出春季>冬季>秋季~夏季的特征.大气颗粒物中水溶性Pb干沉降通量为3.14 mg·(m^2·a)^(-1),占Pb干沉降总量的43%,这一比例呈现出冬春季高于夏秋季的特征.人为源排放不仅增加了大气颗粒物和Pb的干沉降通量,也改变了水溶性Pb干沉降通量的季节分布.研究结果对科学评估重金属沉降的生态影响和健康效应提供了科学基础,同时凸显了消减人为源重金属排放的重要性.

To investigate the dry deposition pattern of particulate matter and lead in urban Beijing, dry deposited particles were collected based on a surrogate surface between December 2013 and November 2014 and subjected to elemental analysis by using microwave digestion and inductively coupled plasma mass spectrometry. The results showed that dry deposition fluxes of particle mass and total lead were 0. 84 t·（hm^2·a） ^- 1 and 7. 56 mg·（m^2·a） ^- 1 , respectively, with a seasonal trend of spring ﹥ winter ﹥ autumn ~summer, exhibiting a similar temporal pattern to that of coarse particles. In addition, dry deposition flux of water-soluble lead was 3. 14 mg·（m^2·a） ^- 1 . It was found that the ratio of soluble fraction to total lead in dry deposited particles reached up to 43% , coinciding with a seasonal variation of ambient sulfur dioxide. The findings highlighted the anthropogenic imprints on the dry deposition flux of particles and heavy metals as well as the solubility of lead. This study also provides a first-hand dataset that can be used to assess ecological and environmental impacts of dry deposited lead, and an up-to-date scientific basis for the crafting abatement strategies to further reduce emission of heavy metals in China.