杂质对饱和脂肪酸紫外吸收的贡献
Impurity contribution to ultraviolet absorption of saturated fatty acids
AI总结：
本研究针对液态饱和脂肪酸大于250 nm波长光吸收的未解之谜，证实液态壬酸的该吸收源于其自身最多0.1%的微量杂质，且其光解速率上限比大气相关羰基化合物小3-5个数量级。
摘要：
饱和脂肪酸是海洋和海浪飞沫中大量存在的有机化合物。太阳辐射引发的它们的光化学反应，近期被发现是挥发性有机化合物的非生物来源，而这类化合物是二次有机气溶胶的前体。然而，液态饱和脂肪酸对波长大于250 nm的光的吸收现象虽早在1931年就被首次报道，但其成因至今仍未得到解释。本研究表明，此前报道的液态壬酸[CH₃(CH₂)₇COOH]对波长大于250 nm的光的吸收，源自壬酸试剂本身所含的微量杂质（最多0.1%）。本研究新测得的壬酸吸收截面显示，其光解速率上限比大气相关羰基化合物的光解速率小3到5个数量级。
英文摘要：
Saturated fatty acids are abundant organic compounds in oceans and sea sprays. Their photochemical reactions induced by solar radiation have recently been discovered as an abiotic source of volatile organic compounds, which serve as precursors of secondary organic aerosols. However, photoabsorption of wavelengths longer than 250 nm in liquid saturated fatty acids remains unexplained, despite being first reported in 1931. Here we demonstrate that the previously reported absorption of wavelengths longer than 250 nm by liquid nonanoic acid [CH3(CH2)7COOH)] originates from traces of impurities (0.1% at most) intrinsically contained in nonanoic acid reagents. Absorption cross sections of nonanoic acid newly obtained here indicate that the upper limit of its photolysis rate is three-to-five orders of magnitude smaller than those for atmospherically relevant carbonyl compounds.
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