Sea-to-Air Fluxes of Isoprene and Monoterpenes in the Coastal Upwelling Region of Peninsular Malaysia

Volatile organic compounds (VOCs) affect oxidant loadings and secondary organic aerosol formation in the lower atmosphere. The marine environment is thought to be an important global source of biogenic VOCs (BVOCs). Despite that, there is relatively limited knowledge on coastal upwelling BVOCs. This paper presents sea-to-air fluxes and spatial and temporal distributions of the BVOCs, isoprene and monoterpenes, in the coastal upwelling region off the east coast of Peninsular Malaysia (ECPM). The overall fluxes ranged between 107 and 108 molecules/cm2/s, which is comparable with open ocean values. Isoprene dominated the overall fluxes with an average percentage of 65% compared to monoterpenes (total) (35%). Among the monoterpene compounds, β-pinene showed the highest average flux, followed by α-pinene and limonene. The spatial distribution suggests that isoprene fluxes potentially correspond to the sea surface water nutrients compared to monoterpenes. A significant relationship between isoprene and monoterpene (total) fluxes was observed (R = 0.73, P < 0.01), which may indicate that both isoprene and monoterpenes are controlled by an identical biological factor (e.g., chlorophyll-a). This study concludes that the upwelling region off the ECPM is potentially an important source of atmospheric isoprene and monoterpenes.