天津市城市扬尘及土壤尘单颗粒质谱特征

Characteristics of Single Urban Raised Dust and Soil Dust in Tianjin City

为探究城市扬尘及不同类型的土壤尘单颗粒质谱特征,使用SPAMS(单颗粒气溶胶质谱仪)对天津城市扬尘及不同类型土壤尘(菜地、果园、林地、农田)进行分析.结果表明:天津城市扬尘粒径在0.5~1.0μm之间的占比较高;4种土壤尘在不同粒径段的分布略有差异,整体而言小粒径段(0.2~1.0μm)占比低于大粒径段(1.0~2.0μm),说明土壤尘更易分布在大粒径段.在小粒径段,天津城市扬尘颗粒含有更多的碳组分及硫酸盐,大粒径段含有较多的金属、氯、硝酸盐、磷酸盐及硅酸盐组分.与城市扬尘相比,土壤尘中^(23)Na^+、^(46)NO_2^-峰强显著降低,^(39)K^+、^(35)Cl^-、^(42)CNO^-峰强增高,通过其峰强比值分布可将城市扬尘与土壤尘明显区分.与城市扬尘相比,土壤尘中含碳颗粒显著减少,同时出现钾类颗粒.城市扬尘作为一种混合源,含碳颗粒可能受多种排放源(机动车、燃煤等)影响,而土壤尘中钾类颗粒可能与农作物施肥有关.两种源类含^(27)Al^+、^(26)CN^-、^(35)Cl^-、^(42)CNO^-、^(46)NO_2^-、^(76)Si O_3^-、^(79)PO_3^-的颗粒占比均高于50%,其中^(40)Ca^+、^(46)NO_2^-和^(62)NO_3^-颗粒在天津城市扬尘中占比更高,^(76)Si O_3^-颗粒在土壤尘中占比更高,表明天津城市扬尘中更多的颗粒含有钙和硝酸盐组分,土壤尘中含硅酸盐颗粒较多.与机动车尾气、生物质燃烧等排放的颗粒物相比,天津城市扬尘及土壤尘中含^(97)HSO_4^-颗粒占比较低,表明天津城市扬尘及土壤尘颗粒中含有更少的硫酸盐,可作为将天津城市扬尘、土壤尘与其他源类区分的指标.

In order to investigate the characteristics of single urban raised dust and four types of soil dust（ i.e.,vegetable,orchard,wood and cropland soils）,single particle aerosol mass spectrometry（ SPAMS） was used to analyze the characteristics. Results showed more urban raised dust appeared between 0. 5 and 1. 0 μm. Compared with other sources,the size distribution of four soil dust had slight differences. Generally speaking,the fraction of soil particle in the range of 0. 2-1. 0 μm was lower than 1. 0-2. 0 μm,indicating the soil dust prefer to concentrating in larger size. As for urban raised dust,more carbonaceous species and sulfate appear in smaller particle size,while more metal,chlorine,nitrate,phosphate and silicate in the larger size. Compared with urban raised dust,in soil dust,^23Na^＋and^46NO2^-intensified significantly,while^39K^＋,^35Cl^-and^42CNO^- weakened,the urban raised dust and soil dust can be distinguished based on the distribution of the specific intensity ratios. Moreover,the classification results showed that the carbonaceous particles in soil dust decreased,while the K particles appeared. The urban raised dust was considered as a mixed source. The carbonaceous species particles in urban raised dust may from different sources such as vehicle and coal burning,and more K particles in soil dust may relate to the fertilization. Particles containing^27Al^＋,^26CN^-,^35Cl^-,^42CNO^-,^46NO2^-,^76SiO3^-and ^79PO3^-dominated（ exceeding 50%） in both urban raised and soil dusts,with^40Ca^＋,^46NO2^-,^22）NO3^-obviously in urban raised dust and ^76SiO3^- in soil dust,indicating more calcium andnitrate species in urban raised dust and more silicate in soil dust. Fewer ^97HSO4^- particles showed limited sulfate in urban raised dust and soil dust,which can be the tracer to differentiate from other sources.