Crop-specific biogenic volatile organic compound emissions in China.

Biogenic volatile organic compounds (BVOCs) emissions from agricultural crops significantly impact atmospheric chemistry and air quality, yet detailed crop emission remains rarely quantified, restricting understanding of agroecosystems environmental effects. This study investigates the differential BVOCs emissions of crops across China by integrating growth parameters (e.g., leaf area index, phenology) with improved emission factors. The total BVOCs emissions from crops in China (2023) is 1936.8 Gg, including maize (645.3 Gg), rice (777.0 Gg), wheat (119.5 Gg), cotton (58.9 Gg), soybeans (76.5 Gg), peanuts (58.0 Gg), rape (67.7 Gg), sesame (1.6 Gg), tubers (potatoes, sweet potatoes, cassava) (125.9 Gg), and hemp (6.5 Gg). Maize and rice have higher emission intensity (emissions per unit area) than wheat. This emission intensity for the same crop varies regionally. The growth periods with higher emissions is various for specific crop (e.g., maize and rice: growth periods; wheat: maturity period). The spatial distribution on both sides of the Heihe-Tengchong Line exhibited differentiation (the southeastern side: 43 % of the national land area, 92.8 % of the emissions). The spatial distribution of BVOCs emissions from various crops reflects their cultivation distribution characteristics. The monthly variation of emissions displayed a "single-peak" characteristic (64.1% in summer), and not all crops released BVOCs throughout the year. The timing of emissions varied both between crops and across regions for the same crop. Crop BVOCs emissions are predominantly oxygenated VOCs (82.5 %), with methanol as the main component. These results provide important basic data for assessing agricultural impact on ozone (O3) and secondary organic aerosols (SOA).