温州市PM_(2.5)中水溶性离子污染特征及来源分析

Characteristics and sources apportionment of water-soluble ions in PM_(2.5) of Wenzhou,Zhejiang Province

2015年1~12月在温州市区采集448个PM_(2.5)样品,采用离子色谱法分析PM_(2.5)中9种水溶性离子(SO_4^(2-)、NO_3^-、NH_4^+、Cl^-、Na^+、K^+、Ca^(2+)、Mg^(2+)和F^-)的浓度,研究其污染特征、化学组分和来源.采样期间9种水溶性离子总浓度为39.97μg·m^(-3),SO_4^(2-)、NO_3^-和NH_4^+占所测水溶性离子总量的(40.19±10.04)%.离子总浓度的季节变化特征为冬季>春季>秋季>夏季,从空间分布上看,多数季节市站采样点PM_(2.5)中离子总浓度低于南浦、龙湾和瓯海采样点.相关性分析结果显示,PM_(2.5)值与NH_4^+、Ca^(2+)、Na^+、K^+、Cl^-、NO_3^-、SO_4^(2-)浓度显著相关,PM_(2.5)中SO_4^(2-)和NH_4^+的主要结合方式为(NH_4)_2SO_4.硫氧化速率(SOR)和氮氧化速率(NOR)的年均值分别为0.44±0.09和0.13±0.04,表明温州市PM_(2.5)中SO_4^(2-)和NO_3^-主要由二次转化形成.主成分分析结果表明,温州市PM_(2.5)中水溶性离子主要来源于燃煤(火力发电和工业燃煤)、生物质燃烧、机动车尾气以及道路和建筑扬尘.

We collected 448 samples of PM2.5 at urban area of Wenzhou from January to December, 2015. Water-sol- uble ionic constituents（SO4^2- , NO3- , NH4＋ , Cl- , Na＋ , K＋ , Ca2＋ , Mg2＋ and F-）associated to PM2.5 were detected by Ion Chromatogram （IC）, chemical composition, variation characteristics, as well as the source apportionment were analyzed. The average mass concentration of the 9 ions was found to be 39.97 μg · m-3. Secondary inorganic species SO4^2- ,NO3- and NH＋were the major components of water-soluble ions in PM2. 5, with a contribution of （40.19±10.04） %. The order of total ions concentration was winter 〉 spring 〉 autumn 〉 summer, showing obvious seasonal variations, and from the space, the concentrations of PMz. 5-bound water-soluble ions were lower in Shizhan in most of the seasons. The results of correlation analysis showed that PM2.5 and NH4＋ .Ca2＋ .Na＋ .K＋ , Cl-、NO3-.SO4^2- had a significant negative correlation, and most of SO4%2- and NH4＋ existed as （NH4）2SO4 in Wenzhou city. In addition, the sulfate oxidizing rate （SOR） and nitrate oxidizing rate （NOR） were （0.44±0.09） and （0.13±0.04）, respectively. It indicated that SO4^2- and NO3- in PM2.5 were resulted by the secondary transformation. Principal component analysis （PCA） results suggested that water-soluble inorganic ions in PM2.5 mainly came from coal combustion （thermal power generation and coal-fired industry）, biomass combustion, vehicle exhaust emission, road and construction dust.