| Marine organic aerosol is reported to be a fatal factor in earth system, which playsan important role in both climate change and atmospheric chemistry study. Organiccarbon in marine aerosol is about one magnitude larger than that in anthropogenicaerosol, while marine SOA contributed by amines can be as high as20%, much higherthan that from other VOCs like isoprene. Besides, importance of atmospheric aminesin new particle formation has become one of scientific hot topics in recent five years.However, a lack of field study about sources, composition and size distribution ofamines limited our understanding in their potential influence in atmospheric chemistry.The Yellow Sea and East China Sea, with high primary productivity and may existabundant amines, become an ideal area to study physical and chemical properties ofaerosol amines in marine environment.In this study, size-dependent aerosol samples were collected during four cruisesover the Yellow Sea and East China Sea. Anderson size-dependent aerosol samplerwith minimin size of <0.43μm was used in the three cruises in2011, whilenano-MOUDI sampler with minimin size of <10nm was used in the2012cruise.Amines were analyzed by ion chromatograph (IC). Our developed methods can beapplied in analyzing six kinds of common amines in atmosphere. Dimethylamine(DMA) and trimethylamine (TMA) are most abundant amines in this study.Concentrations are quite different in high and low biologic activity season. Forexample, concentrations of DMA in two high biologic activity (HBA) cruises are4.3±8.3nmol/m3and3.1±2.4nmol/m3, while TMA were also high with concentrationsof2.6±4.5nmol/m3and2.6±3.5nmol/m3. In contrast, concentrations of DMA werelow in early spring and late fall with values of1.9±3.4nmol/m3and0.60±0.18nmol/m3, respectively. Concentrations of atmospheric particulate amines were impacted by both ocean biologic acitivity and gas/particle condensation. Two sampleswith highest amines concentrations were collected during bloom and fog.Contribution of atmospheric amines by polluted source from land or coastal area isnegligible, when distributions of amines and secondary ions were analyzed.Concentrations of aerosol amines were found to be well correlated with chlorophyll insurface ocean. A hypothesis is then raised that ocean emission may be the main sourceof amines in this study, which was further testified by a deep analyze of sodiumdistribution and the meteorological conditions.Size distributions of amines are impacted by gas/particle condensation, biologicactivity and probably nucleation, which can be further explained by the day/nightsize-dependent aerosol samples in two cruises in2011. In LBA cruise (March-April),particulate amines were formed at night by gas/particle condensation, since mostsamples were found with an accumulation mode of DMA/TMA at <0.43μm. However,such distribution was changed in HBA cruise (May-June) when oceanic aminesemission was strong during day. An accumulation mode of DMA/TMA was found atlarger size of0.43-0.65μm. During fog days, another mode of~1.0μm was found andwas considered to be contributed by fog process. An inversion algorithm, on the basisthat ambient aerosol is of multimodal lognormal size distributions, was applied toinvestigate the contribution of different modes in nano-MOUDI samples. TMA wasmainly contributed by Aikten mode (~0.02μm) and condensation mode (0.2μm) witha number of29%and52%. Such results represent the formation pathway ofparticulate amines during LBA season in our study area.A ratio of N-amine/N-[amine+NH4+] was applied to judge the contribution ofamines to nitrogen in cation. Higher ratios were found during HBA cruises with thenumber of22%and7.9%. Distribution of the ratio changed a lot with different timeand location, impacted by both ocean biologic activity and gas/particle condensationof amines.Besides, a developed method of aerosol acidity calculation consideringamines was raised. |
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