温州市PM_(2.5)中水溶性离子污染特征及来源分析

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.

Characteristics and sources apportionment of water-soluble ions in PM2.5 of Wenzhou,Zhejiang Province

We collected 448 samples of PM_2.5 at urban area of Wenzhou from January to December, 2015. Water-soluble ionic constituents(SO₄^2-, NO₃^-, NH₄⁺, Cl^-, Na⁺, K⁺, Ca²⁺, Mg²⁺ and F^-)associated to PM_2.5 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 NH₄⁺were the major components of water-soluble ions in PM_2.5, 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 PM_2.5-bound water-soluble ions were lower in Shizhan in most of the seasons. The results of correlation analysis showed that PM_2.5 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 PM_2.5 were resulted by the secondary transformation. Principal component analysis (PCA) results suggested that water-soluble inorganic ions in PM_2.5 mainly came from coal combustion (thermal power generation and coal-fired industry), biomass combustion, vehicle exhaust emission, road and construction dust.