School of Chemical Engineering, National Technical University of Athens, Heroon Polytechniou 9, GR-15780 Zografos, Athens, Greece.
Sci Total Environ. 2012 Jan 1;414:535-45. doi: 10.1016/j.scitotenv.2011.10.058. Epub 2011 Nov 25.
Elemental and organic carbon (EC and OC) hourly concentrations were measured continuously, at an urban location in central Athens, Greece, for an 8-month period (January-August). Average concentrations of 2.2 μgC m(-3) and 6.8 μgC m(-3) were observed, for EC and OC, respectively. The combined contribution of carbonaceous compounds (EC plus organic matter) to PM(10) was calculated at 26%. The seasonal variability of EC was limited, while OC mean concentrations were significantly higher (by 23%), during the warm months (May-August). The weekly variation followed a different pattern, with the weekend decrease of EC levels (25%) being more pronounced than of OC (14%). EC produced a bimodal diurnal cycle, with the morning rush hour traffic mode prevailing. The OC mean circadian variation displayed those peaks as well. However, midday-to-afternoon presence of secondary organic aerosol (SOA) was strongly indicated. The conditional probability function was used to assess the impact of wind direction. High EC, OC levels were linked to southern flows, which during summer are mainly related to the appearance of sea breeze circulation. The temporal variation of EC, OC and their correlation patterns with primary and secondary gaseous pollutants, suggested that, although primary emissions affected both fractions, SOA formation is an important factor to be accounted for, especially during the photochemical season. Secondary organic carbon was estimated using the EC tracer method and orthogonal regression on OC, EC hourly concentration data. The average contributions of secondary organic carbon (SOC) to OC were calculated at 20.9% for the cold period and 30.3% for the warm period. Maximum values of 58% and 91% were estimated for daily and hourly contributions, respectively. The SOC diurnal variations suggested photochemical formation throughout the year, intensified during summer months, with the correlation coefficient between SOC and the sum of oxidants (NO(2+)O(3)) reaching up to 0.84.
元素碳（EC）和有机碳（OC）的浓度每小时都在被连续测量，地点是希腊雅典市中心的一个城区，测量时间为 8 个月（1 月至 8 月）。EC 和 OC 的平均浓度分别为 2.2μgC m(-3)和 6.8μgC m(-3)。碳质化合物（EC 加有机物）对 PM(10)的综合贡献计算值为 26%。EC 的季节性变化有限，而 OC 的平均浓度在温暖月份（5 月至 8 月）显著更高（高 23%）。每周的变化呈现出不同的模式，EC 水平的周末下降（25%）比 OC（14%）更为明显。EC 呈现出双峰的日变化周期，早晨交通高峰时段的车流模式占主导地位。OC 的日循环平均变化也显示出这些峰值。然而，中午至下午存在明显的二次有机气溶胶（SOA）。条件概率函数用于评估风向的影响。高 EC、OC 水平与南风有关，南风在夏季主要与海风循环的出现有关。EC、OC 的时间变化及其与一次和二次气态污染物的相关模式表明，尽管一次排放会影响这两个部分，但 SOA 的形成是一个需要考虑的重要因素，特别是在光化学季节。利用 EC 示踪剂法和 OC、EC 小时浓度数据的正交回归法，估算二次有机碳（SOC）。冷季 SOC 对 OC 的平均贡献率为 20.9%，暖季为 30.3%。分别估计日和时的 SOC 最大贡献值为 58%和 91%。SOC 的日变化表明全年都有光化学形成，夏季更为强烈，SOC 与氧化剂（NO(2+)O(3)）总和之间的相关系数高达 0.84。
