南京市大气细颗粒物化学成分分析

The Analysis of Chemistry Composition of Fine-Mode Particles in Nanjing

为了解南京大气细粒子的污染水平和污染特征,在南京市中心鼓楼和北郊南京信息工程大学校内进行了连续1 a、每季度5 d的大气气溶胶同步采样。用称重法、离子色谱法和电感耦合等离子质谱法分别测得细颗粒物的质量浓度、水溶性离子和元素组成。结果表明,南京地区PM2.1污染比较严重,水溶性离子是细粒子的重要组分,所测6种离子质量浓度总和分别占市区和北郊PM2.1的46.99%、42.32%。PM2.1中的各离子最高浓度都出现在冬季。NH4+与SO42-的相关性好,可能主要以(NH4)2SO4形式存在。温度对SOR和NOR的影响显著,温度升高时SOR值增大而NOR显著减小。通过计算NO3-与SO24-的质量比发现,南京市SO2和NOx主要来自于固定源(如煤的燃烧)。分析细颗粒物中元素含量和富集因子结果表明,Pb、As、Zn、Hg、Cu、Cr、Ni元素的人为污染较明显,且北郊的污染重于市区。比较PM2.1和PM3.3中的离子成分发现,SO42-、NH4+在PM2.1中占据绝对优势,F-、Cl-、NO2-、NO3-等不在细粒子中占明显优势。从元素组成来看,Pb、Zn在PM2.1细粒子中含量显著,而Ca、Mg、Na等在粗粒子中富集。

Two sampling positions were set up to investigate the characteristics of fine particles in the atmosphere in Nanjing;one was in Nanjing University（representing the urban area）,and the other in the campus of Nanjing University of Information Science and Technology （representing the suburb region）. The aerosol sampling at the two sites was operated for 5 days in each season in 2007. The mass concentration,water-soluble ions and elemental composition of fine particles were detected by the weighing method, ion chromatography, inductively coupled plasma chromatography separately. The results show that water soluble ions were important components of PM2.1 whose weight percents were 46.99% （urban） and 42.32% （suburb）,respectively. The concentration of all the anions in PM2.1was the maximum in winter. A high correlation lay between NH^＋4 and SO^2-4, which meant that they might exist in the form of （NH4）2SO4. The SOR（ conversion ratio of SO2） and NOR（ conversion ratio of NO2） were determined largely by temperature ： SOR increased and NOR decreased markedly when the temperature was high. Due to the NO^-3/SO^2-4 mass ratio 〈 1 ,stationary sources such as coal burning were the major sources of SO2 and NOx. The mass concentration and enrichment factor of elements suggest that Pb, As, Zn, Hg, Cu, Cr and Ni were anthropogenic pollutants. Their pollution was much heavier in the urban than that in the suburb area. The water soluble ions SO^2-4, NH^＋4 and the elements Pb, Zn had superiority in PM2.1, while F^-, Cl^-,NO^-2,NO^-3 and Ca,Mg,Na were enriched in coarse mode particles.