Isoprenoid emissions from natural vegetation increased rapidly in eastern China.

An accurate local biogenic volatile organic compound (BVOC) emission inventory in Shandong Province is crucial for air pollution control in Shandong and the Beijing-Tianjin-Hebei region, China. We estimated the multi-year isoprenoid emissions from natural vegetation in Shandong Province at a spatial resolution of 4 km × 4 km using the MEGAN2.1 model. A new vegetation classification with 23 plant species/types was developed, and emission factors were determined based on the most detailed and localized investigation and statistics. Isoprene, monoterpene, and sesquiterpene emissions in 2018 were 325.6, 18.2, and 7.9 Gg (mass of carbon), respectively. β-Pinene, α-pinene, ocimene, farnescene, and caryophyllene were the dominant monoterpenes and sesquiterpenes. Broadleaf trees contributed the most to total emissions, particularly poplar, which had the highest emission rates. Wheat also had higher emissions owing to its large coverage. Isoprenoid emissions displayed an inverted "U" pattern when plotted against the months and peaked in summer. Emissions were concentrated in the western and southeastern areas with emission intensities of >10 ton/grid, including Dezhou, Liaocheng, and Rizhao cities. During 1981-2018, isoprenoid emissions experienced a rapid increase from 12.0 to 351.7 Gg, at a rate of 11.20 Gg/yr. Isoprene had the highest enhancement rate of 10.72 Gg/yr. The most rapid increase was observed in the northwestern cities Dezhou and Liaocheng, and the southeastern cities Rizhao, at an average rate of >100 kg/yr, even >500 kg/yr in some areas. The high emissions and their continued increase should be considered when studying the prevention and control of regional air pollution and making policies in China.