上海PM2.5中碳、氮、硫元素的质量浓度及其季节分布特征

Mass concentrations and seasonal variations of carbon,nitrogen and sulphur in PM2.5 in Shanghai

为更好地认识上海PM2.5的化学组成特征,使用大流量采集器采集了上海典型地区不同季节的PM2.5样品;利用元素分析仪、热/光碳分析仪、离子色谱仪、化学氧化-紫外分光光度法等多种形式分析了样品中含碳、氮、硫组份的质量浓度及组成;对不同方法的结果进行了比较,探讨了这些组份的季节分布特征及影响因素;建立了利用元素分析仪测定结果估算大气PM2.5中含碳组份、含氮组份和含硫组份质量浓度的方法.研究结果表明,上海PM2.5中总碳(total carbon,TC)的春、夏、秋、冬季平均质量浓度分别为14.26,10.44,11.89和24.35μg·m-3,氮元素的春、夏、秋、冬季平均质量浓度分别为8.72,3.07,5.07和17.09μg·m-3,而硫元素的春、夏、秋、冬季平均质量浓度分别为6.50,4.06,3.66和6.00μg·m-3.上海PM2.5中的碳元素主要以有机碳和元素碳的形式存在,无机碳的贡献很小;绝大部分的含氮物质为水溶性含氮物质,且以无机氮为主;硫元素几乎全部以水溶性硫酸盐的形式存在.元素分析仪的测定结果可以有效地反映PM2.5中含碳、氮、硫物质的质量浓度及组成特征.

To better understand the chemical make-ups of PM2.5 in Shanghai,samples have been collected at a typical suburban site in Shanghai in four seasons with a highvolume PM2.5 sampler.Mass concentrations and compositions of carbon-,nitrogen-and sulphur-containing components in the PM2.5 samples have been measured with different instruments including elemental analyzer,thermal/optical carbon analyzer,ion chromatograph,and chemical oxidation-UV spectrophotometer,and the result from the different methods were compared.The seasonal variations and influencing factors of the concentrations of these components were investigated.Furthermore,methods for the estimation of the mass concentrations of carbon-,nitrogen-and sulphur-containing components in PM2.5 in Shanghai with the C,N,S concentrations from the elemental analyzer was developed.Results show that mass concentrations of total carbon in PM2.5 in Shanghai in spring,summer,autumn and winter are 14.26,10.44,11.89 and 24.35μg·m-3 respectively,8.72,3.07,5.07 and 17.09μg·m-3 respectively for nitrogen,while 6.50,4.06,3.66 and 6.00μg·m-3 respectively for sulphur.Most of the carbon in PM2.5 in Shanghai exists as organic and elemental carbon,and the contribution of inorganic carbon is very small.Most of the nitrogen in PM2.5 in Shanghai appears in the form of water-soluble inorganic components,while most of the sulphur-containing components appear in the form of water-soluble sulphate.Elemental analyzer could be used effectively to study the mass concentrations and compositional characteristics of the carbon-containing,nitrogen-containing and sulphurcontaining components in PM2.5.