南京城区冬季大气污染特征

为探究南京城区冬季主要大气污染物浓度变化规律，运用南京市空气自动监测站的φ(CO)、φ(O₃)、φ(NO₂)、φ(SO₂)、ρ(PM_2.5)和ρ(PM₁₀)逐时资料，结合同期气象数据，分析了2014年冬季(2014年12月—2015年2月)南京城区大气污染浓度水平和变化特征，探讨2015年春节期间在实施减排措施下气象条件对空气质量的影响.结果表明:① 观测期φ(CO)日均值和φ(O₃)小时均值未超过GB 3095—2012《环境空气质量标准》二级标准限值；ρ(PM_2.5)、ρ(PM₁₀)、φ(NO₂)、φ(SO₂)日均值分别超标44%、38%、34%、2%；ρ(PM_2.5)、ρ(PM₁₀)最大日均值分别为231和283 μg/m3，分别是GB 3095—2012二级标准限值的3.1、1.9倍. ② 日变化分析显示，φ(CO)与φ(NO₂)呈早晚双峰型变化，与早晚交通高峰源排放有关；φ(O₃)呈明显的单峰型，在午后出现峰值；φ(SO₂)呈单峰型且夜间浓度低于白天；ρ(PM_2.5)和ρ(PM₁₀)为双峰型变化，峰值出现在10:00和22:00左右. ③ 南京地区污染物周末浓度整体高于工作日，其中周末φ(CO)、φ(NO₂)和ρ(PM_2.5)显著高于工作日，“周末效应”显著. ④ 2015年春节期间，南京实施减排措施后，即使在不利的气象条件下，污染物浓度也未出现明显升高，说明减排措施有效削弱了污染源的排放，是保持南京地区良好空气质量的重要因素. 

Characteristic Analysis of Atmospheric Pollutants in Nanjing Urban Area in Winter

In order to investigate the variation profile of air pollutant concentrations in the Nanjing urban area in winter, real-time monitoring data on φ(CO), φ(O₃), φ(NO₂), φ(SO₂), ρ(PM_2.5) and ρ(PM₁₀) from air quality automatic monitoring stations, as well as the synchronous meteorological data, were used in this study. The concentration level and variation profile of air pollutants in the Nanjing urban area in winter 2014 (from December 2014 to February 2015) were analyzed. The effects of meteorological conditions on air quality during emission reduction measures during the Spring Festival of 2015 were investigated. The results indicated that during the observation period, both daily mean values and hourly mean values of φ(CO) and φ(O₃) were below the grade Ⅱ standard in China′s Ambient Air Quality Standards (GB 3095-2012). Daily mean values of ρ(PM_2.5), ρ(PM₁₀), φ(NO₂) and φ(SO₂) exceeded the limits by 44%, 38%, 34% and 2%, respectively. ρ(PM_2.5) and ρ(PM₁₀) reached maximal daily average values of 231 and 283 μg/m3, respectively, which were 3.1 times and 1.9 times the grade Ⅱ standard. The daily variation indicated that φ(CO) and φ(NO₂) values presented bimodal patterns in the morning and evening, which was related to pollutant discharge from traffic rush in the morning and evening. Variation trend of φ(O₃) values appeared as an obvious single peak, with peak value appearing in the afternoon. Variation trend of φ(SO₂) values presented a single peak, with the concentration at night lower than that in the daytime. Variation trend of ρ(PM_2.5) and ρ(PM₁₀) values generally showed synchronous bimodal pattern, with the peak values appearing at around 10:00 and 22:00. In the urban area of Nanjing, pollutant concentrations during the weekend were overall higher than those on the workdays. In particular, the values of φ(CO), φ(NO₂) and ρ(PM_2.5) during the weekend were significantly higher than those on the workdays, with an obvious ′weekend effect′ observed. Since the emission reduction measures were adopted in Nanjing during the Spring Festival of 2015, serious accumulation of pollutants in Nanjing was not observed, despite poor weather conditions, indicating the important contribution of emission reduction measures towards the improvement of air quality.