The chemical and stable carbon isotopic composition of the organic aerosol particles (OA) emitted by a shuttle passenger ship between mainland Naples and island Capri in Italy were investigated. Various methylsiloxanes and derivatives were found in particulate ship emissions for the first time, as identified in the mass spectra of a thermal desorption – proton transfer reaction – mass spectrometer (TD-PTR-MS) based on the natural abundance of silicon isotopes. Large contributions of methylsiloxanes to OA (up to 59.3%) were found under inefficient combustion conditions, and considerably lower methylsiloxane emissions were observed under cruise conditions (1.2% of OA). Furthermore, the stable carbon isotopic composition can provide a fingerprint for methylsiloxanes, as they have low δ¹³C values in the range of −44.91‰ ± 4.29‰. The occurrence of methylsiloxanes was therefore further supported by low δ¹³C values of particulate organic carbon (OC), ranging from −34.7‰ to −39.4‰, when carbon fractions of methylsiloxanes in OC were high. The δ¹³C values of OC increased up to around −26.7‰ under cruise conditions, when carbon fractions of methylsiloxanes in OC were low. Overall, the δ¹³C value of OC decreased linearly with increasing carbon fraction of methylsiloxanes in OC, and the slope is consistent with a mixture of methylsiloxanes and fuel combustion products. The methylsiloxanes in ship emissions may come from engine lubricants.

研究了那不勒斯大陆和意大利卡普里岛之间的穿梭客船排放的有机气溶胶颗粒（OA）的化学和稳定碳同位素组成。各种甲基硅氧烷和衍生物首次在微粒船舶排放物中发现，这是在基于硅同位素自然丰度的热解吸-质子转移反应-质谱仪 (TD-PTR-MS) 的质谱中确定的。在低效燃烧条件下发现甲基硅氧烷对 OA 的贡献很大（高达 59.3%），在巡航条件下观察到甲基硅氧烷排放量显着降低（占 OA 的 1.2%）。此外，稳定的碳同位素组成可以为甲基硅氧烷提供指纹，因为它们具有低 δ ¹³C值在-44.91‰±4.29‰范围内。因此，当 OC 中甲基硅氧烷的碳含量较高时，颗粒有机碳 (OC)的低 δ ^{13 C 值（范围从 -34.7‰ 到 -39.4‰）进一步支持了甲基硅氧烷的出现。}当OC中甲基硅氧烷的碳含量较低时，OC的δ ¹³ C值在巡航条件下增加到-26.7‰左右。总体而言，OC的δ ¹³ C值随着OC中甲基硅氧烷的碳含量的增加而线性下降，并且斜率与甲基硅氧烷和燃料燃烧产物的混合物一致。船舶排放物中的甲基硅氧烷可能来自发动机润滑油。