Preliminary Analysis On The Macromolecular Organic Matters Extracted From Atmospheric PM₁₀, Falling Dust And Marine Sediment

Macromolecular organic matters （MOMs） were omnipresent components in soil,sediment and atmospheric particulate matter. Previous researchers paid more attentionto inorganic matter and low molecular weight organic matter in PM₁₀, falling dust andmarine sediment than MOMs, such as humic acid （HA）, kerogen （K） and blackcarbon （BC）, for their highly complicated chemical composition and structure.In this work, coastal city, Xiamen, was selected as the research subject, and PM₁₀,falling dust and marine sediment samples were collected. Then a promotedcomprehensive wet chemical procedure was performed with base extraction, aciddemineralization and dichromate oxidation to extract and purify humic acid （HA）,kerogen+black carbon （KB） and black carbon （BC）. The Chemical composition,structure and source of the three macromolecular organic matters were analyzed anddiscussed by elemental analysis （EA）, scanning electron microscope （SEM）, flouriertransform infrared spectroscopy （FT-IR）, stable carbon isotope （δ13C） andpyrolysis-gas chromatography-mass spectroscopy （Py-GC-MS）. The results showed:（1） Elemental analysis exhibited that the order of C contents and H/C ratios were inthe order of HA, KB and BC in PM₁₀, and C/N ratio was in the reverse order. TheC/N ratios of HA in PM₁₀indicated more information of terrestrial vascular plants,especially C3plants, while the C/N ratios of K and BC presented more contribution ofwood charcoal, diesel and vegetation fire residues. FT-IR analysis exhibited that HAhad higher peak at3400cm-1,2930cm-1and2860cm-1than of BC and KB, whichdetermined that HA had more compounds of aliphatic structures. Stable carbonisotope presented that C3plants might be the predominant source of HA, KB and BCin PM₁₀; furthermore, obvious information of fossil fuel and automobile exhaust werealso revealed in BC samples. It was determined that the predominant pyrolysisproducts in MOMs were aromatic compounds and n-alkanes/alkenes, the relativecontent of which could reach over70%. However, the nitrogen-containing compoundwas also the main pyrolysates of HA, which were related with the secondarytransition of some NOx. The relative contents of pyrolysates in three macromolecularorganic matters were also affected by seasons and meteorological factors. （2） Falling dust served as the link between atmospheric particle and marinesediment. The morphological properties of HA, KB and BC extracted from fallingdusts provided rich information for sources, e.g. irregular macroporous networkdebirs observed in kerogen might originate from vegetation, the irregular BC particleswith unique porous in/on the surface might derive from the incomplete burning ofvegetation and charcoal, and the spherical BC particles might derive from coal or oil.The analysis of FT-IR revealed that HA and KB had higher intense peak at3400cm-1and1000¹150cm-1, and BC had higher intense peak at around1710cm-1and1540cm-1, which indicated that BC was more stable than K and HA. The diversity offunctional group components in MOMs were influenced by the dust storm and theseasons. Stable carbon isotope analysis predicted that C3plants were the predominantcontribution to MOMs in dust, otherwise, fossil fuel was another contribution to KBand BC. The differences of δ13C values of MOMs in dust between dust storm andnon-dust storm were affected by the different growth circumstance, the dust from thedesert in Mongolia and northwest of China and the area with lower δ13C values ofterrestrial organic matter.（3） Marine sediment was the ultimate sink of macromolecular organic matters.Estimation results presented that the relative content of HA, KB and BC extractedfrom marine sediment were6.14%,6.74%and7.31%. many marine-derived materialswere observed by SEM analysis， such as calcium diatoms, andcoscinodiscus/stephanodiscus hantzschii. By comparing the morphological propertiesof MOMs in marine sediment with atmospheric environment, marine-derivedalgaenan and framboidal pyrites in KB were also found in marine sediment. The δ13Cvalues indicated that the source of MOMs was dominated by terrestrial C3plants.Furthermore, marine algae, sewage and biomass combustion were also remarkablycontributed to the variations of δ13C values. Estimation results based on the δ13Cvalues also presented that the terrestrial contribution was the predominant source ofMOMs in marine sediments, which ranged from58.32%to84.45%.