Non-methane volatile organic compounds (NMVOCs) play key roles in local and regional atmospheric chemistry as precursors for the production of ozone and secondary organic aerosols. Ambient air C₂-C₅ NMVOCs were measured at a tropical forest site in the central Western Ghats and urban site of Udaipur in India during the late monsoon period of 2016–17 and 2015, respectively. In the Western Ghats, air samples were collected from the protected Bhagwan Mahaveer Sanctuary. Ethene, propene, and isoprene were the dominant biogenic compounds with mean concentrations of 4.8 ± 2, 1.6 ± 0.66 and 1.05 ± 0.43 ppb, respectively. The concentrations of anthropogenic compounds such as propane and pentane were significantly lower than those of light alkenes. The contributions of ethene and propene among different NMVOCs were ~ 44 and 14%, respectively. However, the contributions of isoprene were highly variable of 3–22%. The tight correlation (r² = 0.90) between the mixing ratios of ethene and propene and their ratio indicates their common formation and emission mechanisms. The molar emission ratio of ethene/propene (2.9 ± 0.17 ppb ppb⁻¹) was comparable to those measured at other biogenic sites of Asia while higher than those reported for mid-latitude sites. The concentrations of light alkenes and isoprene at the Western Ghats were 4–5 times higher than those measured in an urban environment in the same season. The higher ozone formation potentials and Propylene-Equivalent concentrations of alkenes and isoprene than those of other NMVOCs indicate important implications of biogenic emissions on ozone photochemistry in the forest regions of India.

Graphical abstract

中文翻译：

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印度中西部西高止山脉热带常绿森林中生物挥发性有机化合物的环境空气特征

非甲烷挥发性有机化合物（NMVOC）作为生产臭氧和二次有机气溶胶的前体，在当地和区域的大气化学中起着关键作用。环境空气C ₂ -C ₅NMVOCs分别在2016-17和2015年的季风后期在印度西高止山脉中部的热带森林站点和印度乌代浦的城市站点进行了测量。在西高止山脉，从受保护的Bhagwan Mahaveer保护区收集了空气样本。乙烯，丙烯和异戊二烯是主要的生物化合物，平均浓度分别为4.8±2、1.6±0.66和1.05±0.43 ppb。诸如丙烷和戊烷等人为生成的化合物的浓度明显低于轻质烯烃的浓度。乙烯和丙烯在不同NMVOC中的贡献分别约为44％和14％。但是，异戊二烯的贡献变化很大，为3–22％。紧密相关（r ² 乙烯和丙烯的混合比（= 0.90）与它们的比值表示它们共同的形成和排放机理。乙烯/丙烯的摩尔排放比（2.9±0.17 ppb ppb ^-1）与亚洲其他生物成因地点测得的相当，但高于中纬度地点的报道。西高止山脉的轻质烯烃和异戊二烯浓度比同一季节在城市环境中测得的浓度高4-5倍。与其他NMVOC相比，更高的臭氧形成潜能以及烯烃和异戊二烯的丙烯当量浓度表明，生物源排放对印度森林地区的臭氧光化学具有重要意义。

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