Virkkula Aki, Mäkelä Timo, Hillamo Risto, Yli-Tuomi Tarja, Hirsikko Anne, Hämeri Kaarle, Koponen Ismo K
Department of Air Quality Research, Finnish Meteorological Institute, Research and Development, Helsinki, Finland.
J Air Waste Manag Assoc. 2007 Oct;57(10):1214-22. doi: 10.3155/1047-3289.57.10.1214.
A simple method for correcting for the loading effects of aethalometer data is presented. The formula BC(CORRECTED) = (1 + k x ATN) x BC(NONCORRECTED), where ATN is the attenuation and BC is black carbon, was used for correcting aethalometer data obtained from measurements at three different sites: a subway station in Helsinki, an urban background measurement station in Helsinki, and a rural station in Hyytiälä in central Finland. The BC data were compared with simultaneously measured aerosol volume concentrations (V). After the correction algorithm, the BC-to-V ratio remained relatively stable between consequent filter spots, which can be regarded as indirect evidence that the correction algorithm works. The k value calculated from the outdoor sites had a clear seasonal cycle that could be explained by darker aerosol in winter than in summer. When the contribution of BC to the total aerosol volume was high, the k factor was high and vice versa. In winter, the k values at all wavelengths were very close to that obtained from the subway station data. In summer, the k value was wavelength dependent and often negative. When the k value is negative, the noncorrected BC concentrations overestimated the true concentrations.
本文提出了一种校正黑碳仪数据加载效应的简单方法。公式BC（校正后）=(1 + k×ATN)×BC（未校正）用于校正从三个不同地点测量获得的黑碳仪数据，其中ATN为衰减，BC为黑碳。这三个地点分别是：赫尔辛基的一个地铁站、赫尔辛基的一个城市背景测量站以及芬兰中部于韦斯屈莱的一个农村站点。将黑碳数据与同时测量的气溶胶质体积浓度（V）进行了比较。经过校正算法后，连续滤膜点位之间的黑碳与气溶胶质体积比保持相对稳定，这可被视为校正算法有效的间接证据。从室外站点计算得到的k值具有明显的季节周期，这可以用冬季气溶胶比夏季更暗来解释。当黑碳对总气溶胶质体积的贡献较高时，k因子较高，反之亦然。在冬季，所有波长下的k值都非常接近从地铁站数据获得的值。在夏季，k值与波长有关，且常常为负。当k值为负时，未校正的黑碳浓度高估了真实浓度。
