杭州G20减排措施对大气水溶性离子特征的影响

利用2016年颗粒物及水溶性离子采样数据，研究了杭州G20峰会减排措施对大气中无机水溶性离子特征的影响.结果表明，杭州G20峰会减排措施对大气水溶性离子的质量浓度、组成结构、酸碱性等皆存在明显影响.减排措施实施使大气颗粒物和水溶性离子质量浓度下降，受影响的离子主要是NO₃^-、SO₄^2-、NH₄⁺、NO₂^-，其中NO₃^-、SO₄^2-质量浓度的下降使NH₄⁺、Ca²⁺、Cl^-成为浓度前3位的离子.SO₄^2-、NO₃^-、NH₄⁺、Ca²⁺粒径分布呈单峰型，其中SO₄^2-、NO₃^-、NH₄⁺峰值出现在0.65~1.10mm，Ca²⁺峰值出现在5.80~9.00mm，Na⁺、Cl^-、K⁺呈双峰分布，峰值皆出现在3.30~4.70mm和0.65~1.10mm，Na⁺两峰值相当，K⁺、Cl^-在0.65~1.10mm峰值较高.减排措施实施使大气中主要无机盐从NH₄NO₃、（NH₄）₂SO₄、NH₄Cl转变为NH₄Cl、NaCl、KCl，大气颗粒物碱性总体增强.本文研究成果对采取措施改善空气质量具有指导作用.

Influences of the G20 emission reduction on characteristics of water-soluble ions in PM in Hangzhou

Based on aerosol sampling data in 2016 in Hangzhou, the influences of the G20 emission reduction on inorganic water-soluble ions in particulate matter (PM) was investigated. The results proved that the G20 emission reduction had significant impacts on mass concentration, composition and acid-base properties of water-soluble ions in PM. The concentrations of PM and its water-soluble ions were both reduced by the G20 emission reduction. Among them, the concentrations of NO₃^-, SO₄^2-, NH₄⁺ and NO₂^- decreased most obviously, and the concentration decrease of NO₃^- and SO₄^2- made the concentrations of NH₄⁺, Ca²⁺ and Cl^- the top three ions. The size distributions of SO₄^2-, NO₃^-, NH₄⁺ and Ca²⁺ showed mono-modals, and SO₄^2-, NO₃^- and NH₄⁺ were preferably enriched in the fine particles (within range of 0.65~1.10 mm) while Ca²⁺ in the coarse particles (within range of 5.80~9.00mm). The size distributions of Na⁺, Cl^- and K⁺ showed bi-modals with peaks at the particle size of 3.30~4.70mm and 0.65~1.10mm, respectively. the two peaks of Na⁺ were comparable while K⁺ and Cl^- had higher peak values in the size range of 0.65~1.10mm. The main inorganic salts were changed from NH₄NO₃, (NH₄)₂SO₄ and NH₄Cl to NH₄Cl, NaCl and KCl as well as the alkaline enhancement in PM by the G20 emission reduction. The results of this study could provide references for policy formulation and implementation for air quality improvement measures.