Biogenic volatile organic compounds (BVOCs) emitted by plants contribute to secondary air pollution through photochemical reactions in sunlight. Due to the influence of multiple factors, accurately characterizing and quantifying the emission of BVOCs from plant sources is challenging, which poses significant obstacles to the effective management and control of BVOCs. Therefore, this paper summarizes the emission mechanisms of BVOCs from plants, explores the primary factors influencing variations in the emission rates of these compounds, and evaluates the advantages and limitations of contemporary “measurement-modeling” methods for characterizing BVOC emissions. It is concluded that current measurement techniques still need to be further developed to meet the criteria of simplicity, affordability, and high precision simultaneously, and in terms of modeling and prediction studies, there is a lack of in-depth research on the atmospheric chemistry of BVOCs and the synergistic effects of multiple factors. Finally, it is suggested to leverage interdisciplinary strengths to develop advanced measurement technologies and high-resolution models for monitoring volatile compounds. Additionally, strategically selecting low-BVOC tree species in pollution-vulnerable urban areas—contingent on rigorous ecological assessments—combined with stringent controls on anthropogenic precursors (e.g., anthropogenic volatile organic compounds (AVOCs)) could serve as a complementary measure to mitigate secondary pollution.

Background: Biogenic volatile organic compounds (BVOCs) play an essential role in tropospheric atmospheric chemical reactions. There are few studies conducted on BVOCs emission of dominant forest species in the Jing-Jin-Ji area of China. Based on the field survey, forest resources data and the measured standard emission factors, the Guenther model developed in 1993 (G93) was applied in this paper to estimate the emission of BVOCs from several dominant forest species (Platycladus orientalis, Quercus variabilis, Betula platyphylla, Populus tomentosa, Pinus tabuliformis, Robinia pseudoacacia, Ulmus pumila, Salix babylonica and Larix gmelinii) in the Jing-Jin-Ji area in 2017. Then the spatiotemporal emission characteristics and atmospheric chemical reactivity of these species were extensively evaluated. Results: The results showed that the total annual BVOCs emission was estimated to be 70.8 Gg C·year^− 1, consisting 40.5 % (28.7 Gg C·year^− 1) of isoprene, 36.0 % (25.5 Gg C·year^− 1) of monoterpenes and 23.4 % (16.6 Gg C·year^− 1) of other VOCs. The emissions from Platycladus orientalis, Quercus variabilis, Populus tomentosa and Pinus tabulaeformis contributed 56.1 %, 41.2 %, 36.0 % and 31.1 %, respectively. The total BVOCs emission from the Jing-Jin-Ji area accounted for 61.9 % and 1.8 % in summer and winter, respectively. Up to 28.8 % of emission was detected from Chengde followed by Beijing with 24.9 %, that mainly distributed in the Taihang Mountains and the Yanshan Mountains. Additionally, the Robinia pseudoacacia, Populus tomentosa, Quercus variabilis, and Pinus tabulaeformis contributed mainly to BVOCs reaction activity. Conclusions: The BVOCs emission peaked in summer (June, July, and August) and bottomed out in winter (December, January, and February). Chengde contributed the most, followed by Beijing. Platycladus orientalis, Quercus variabilis, Populus tomentosa, Pinus tabulaeformis and Robinia pseudoacacia represent the primary contributors to BVOCs emission and atmospheric reactivity, hence the planting of these species should be reduced.

To investigate how biochar affects coupled migration-biodegradation of NP, a lab-scale column was set up to simulate the recharge process. The filler media of the two columns was mainly composed of silty clay (SC) and biochar amendment silty clay (BCSC). The results showed that the attenuation effect of NP in the BCSC system was 3.3% higher than that in the SC system. The attenuation rate constants of NP in the SC and BCSC systems were 0.20 and 0.24 m⁻¹, respectively, which followed first-order kinetics. The two turning points of NP concentration with depth in the leachate were 0.15 and 0.45 m as a result of fast sorption and biodegradation, respectively. The primary metabolites were not the only hydroxylated 4-nonyl-4-hydroxycyclohexa-2,5-dienone and 4-hydroxyphenyl-nonanoic-acid; detached branched alkyl moieties were also produced during the biotransformation process. The accumulation of NP in the soil was higher in BCSC soils than in the SC system. The bacterial community in the upper layer was more diverse than in the bottom layer, which was related to oxygen concentrations in the water-soil system. Five known bacterial classes (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Sphingobacteria, and Bacilli) and 15 known bacterial genera (six major genera: Methylobacillus, Azotobacterium, Sphingomonas, Pseudomonas, Bacillus, and Hyphomicrobium) were considered to be NP-degradation-associated bacteria. The bacterial community diversity and percentage of NP-degradation-associated bacteria in the BCSC system were marginally greater than those in the SC system. The higher bacterial diversity and adsorption capacity in the BCSC system were able to mitigate the migration of NP into groundwater.