基于两种受体模型的太原市大气降尘来源解析及季节变化特征

于2019年11月至2020年12月期间在典型工业城市太原市开展了降尘采样和降尘化学组分分析.采样期间,太原市平均降尘量约为7.9t/(km²·30d),并呈现在4~6月较高.在选取的8个监测区域中,清徐和巨轮的平均降尘量较高,分别为10.7t/(km²·30d)和10.6t/(km²·30d).降尘化学组分质量中地壳元素(Ca、Si、Al)占比较高,巨轮和桃园监测区域的降尘中Fe元素的质量显著高于其他监测区域.将降尘量和化学组分分析结果分别纳入正定矩阵因子分解(PMF)和偏目标转换-正定矩阵分解(PTT-PMF)两种受体模型中对太原市降尘进行了定量来源解析.通过比较两种受体模型的拟合性能和解析的因子谱发现:PTT-PMF受体模型相较于PMF能够更好地区分出降尘中城市扬尘源和建筑尘源这两类相似的尘源.结果表明,太原市降尘主要有六种来源:城市扬尘源(PMF:35%,PTT-PMF:35%)、建筑尘源(PMF:29%,PTT-PMF:28%)、钢铁工业源(PMF:14%,PTT-PMF:14%)、燃煤源(PMF:13%,PTT-PMF:12%)、二次无机盐(PMF:5%,PTT-PMF:6%)、机动车尾气排放源(PMF:4%,PTT-PMF:5%).两种受体模型得到的平均来源贡献结果相似,而建筑尘源和钢铁工业源的季节变化趋势则有一定的差异.粗粒径源类(城市扬尘源和建筑尘源)是太原市降尘的主要来源,两者对降尘的贡献率超过了60%,并在春季贡献率(4~6月)较高.

Source apportionment and seasonal variation characteristics of atmospheric dustfall in Taiyuan by two receptor models

Dustfall sampling and chemical composition analysis were carried out from November 2019 to December 2020 in Taiyuan, a typical industrial city. During the sampling period, the average amount of dust fall was 7.9t/km²·30d and was higher from April to June in Taiyuan. Among the 8selected monitoring areas, Qingxu and Julun had higher average amounts of dustfall, 10.7t/(km²·30d) and 10.6t/(km²·30d), respectively. Crustal elements (Ca, Si, and Al) accounted for a large proportion in the concentrations of dustfall, and the content of Fe in dustfall in Julun and Taoyuan monitoring areas was significantly higher than that in other monitoring areas. Datasets containing the amount of dustfall and its chemical composition were incorporated into two receptor models, respectively, positive matrix factorization (PMF) and partial target transformation-positive matrix factorization (PTT-PMF), to analyze the sources of dustfall in Taiyuan. By comparing the performance and source profiles of the two receptor models, it was found that the PTT-PMF receptor model which incorporated into the measured source profiles could better distinguish two similar sources (urban dust and construction dust) than the PMF model. According to the results from the two receptor models, dustfall in Taiyuan was mainly from six sources:urban dust (PMF:35%, PTT-PMF:35%), construction dust (PMF:29%, PTT-PMF:28%), steel industry (PMF:14%, PTT-PMF:14%), coal combustion (PMF:13%, PTT-PMF:12%), secondary inorganic compounds (PMF:5%, PTT-PMF:6%), vehicle emissions (PMF:4%, PTT-PMF:5%). The source contributions obtained by the two receptor models were similar, but the seasonal variations of the construction dust and steel industry were different. The contribution of coarse particles (urban dust and construction dust) to dustfall was greater than 60% (the main source in Taiyuan), and its contribution was higher in spring (from April to June).