Biogenic Volatile Organic Compounds Emissions Research Articles

Transforming urban air quality: Green infrastructure strategies for the urban centers of Ethiopia

Urban green infrastructure (GI) plays a crucial role in improving air quality by removing pollutants and reducing emissions from structures. However, in Ethiopia, inadequate GI planning, largely due to limited awareness among planners and policymakers, can undermine the benefits of GI and worsen urban air quality issues. In this study, we demonstrate how the GI strategy approach can enhance air quality and assess the negative impacts of biogenic volatile organic compounds (BVOCs) emitted by certain tree species in Ethiopia, using Hawassa as a case study. We utilized a customized i-Tree Eco model to estimate annual pollutant removal and BVOC emissions and applied the Kriging method in ArcGIS to map their spatial distribution. In Hawassa, GI systems removed 274.2 t of pollutants annually, valued at $1.79 million, with SO2 being the most and CO the least removed pollutants. Air pollution removal was highest during the dry season (37.4%) compared to the long (29.7%) and short rainy seasons (32.9%). Conversely, trees emitted 35.78 t of BVOCs annually, with monoterpene and isoprene being nearly equal contributors. Eucalyptus genus, Casuarina equisetifolia, and Schinus molle species were the top BVOC emitters despite their low population percentages in the study area. While GI types such as urban parks and institutional compounds are effective at pollutant removal, they also exhibit higher BVOC emissions. Our findings highlight the need for optimized species selection, improved GI planning, and enhanced policy support to maximize GI effectiveness, providing valuable insights for planners and policymakers in integrating GI into urban spatial planning.

Unexpectedly strong heat stress induction of monoterpene, methylbutenol, and other volatile emissions for conifers in the cypress family (Cupressaceae)

We investigated the biogenic volatile organic compound (BVOC) emission rates and composition of Cupressaceae species and how the emissions change in response to moderate warming and more severe heat stress. A total of 8 species from 7 distinct Cupressaceae genera were targeted in this study and exposed to laboratory-simulated heatwaves. Each plant was enclosed in a temperature-controlled glass chamber and allowed to equilibrate at 30 °C for 24 h. The temperature was then increased stepwise from 33 °C to 43 °C in 2 °C increments, with each step lasting 2 h, and was finally kept at 45 °C for 12 h. The BVOC emissions were measured periodically using an automated air sampler coupled to a gas chromatograph.Most of the sampled Cupressaceae species (6 out of 8) were low BVOC emitters (<0.3 μgC g−1 h−1) at 30 °C. However, the BVOC emissions of all 8 species increased strongly with temperature, and in most species (5 out of 8), the emissions continued to increase with longer exposure times to heat stress. The largest increase was observed in Thuja occidentalis and Chamaecyparis thyoides, which reached maximum emissions of 350 and 190 μgC g−1 h−1, respectively. Of the different BVOCs, monoterpenes responded most strongly to heat stress, with Q10 temperature coefficients typically ranging between 7.6 and 22, which were significantly greater than the model-predicted value of 2.7. Other BVOCs including sesquiterpenes, C9 aromatics (only detected in Calocedrus decurrens), methylbutenols, and other C5 oxygenates were also induced by heat stress, but generally at a lower magnitude than monoterpenes.Our results indicate that Cupressaceae are a large but typically dormant source of reactive volatile hydrocarbons (mostly monoterpenes) whose emissions can be activated by heat stress. This phenomenon could have important implications for ozone and aerosol formation, air quality, and human health, particularly in urban areas that are prone to heatwaves.

Global Temperature Dependency of Biogenic HCHO Columns Observed From Space: Interpretation of TROPOMI Results Using GEOS‐Chem Model

AbstractTemperature is the principal driver of global atmospheric formaldehyde (HCHO) and its primary oxidation precursor biogenic volatile organic compounds (BVOCs). We revisit such a temperature (T‐) dependency globally, leveraging TROPOMI HCHO column data. We find substantial variations in the T‐dependency of biogenic HCHO across plant functional types (PFTs), with the highest over Broadleaf Evergreen Tropical Trees (doubling every 6.0 K ± 4.1 K) and lowest over Arctic C3 Grass (doubling every 30.8 K ± 9.6 K). The GEOS‐Chem model interprets HCHO columns' T‐dependency at the PFT level (r = 0.87), with a 16% discrepancy on average. The discrepancy can be explained by BVOC emissions T‐dependency for Broadleaf Evergreen Tropical Trees and Warm C4 Grass and can be attributed to the insensitivity of HCHO columns to BVOC emissions for other PFTs. Our findings underscore a potentially magnified variation of BVOC emissions by GEOS‐Chem and MEGAN therein, particularly in regions experiencing greater temperature variations.

Learn from Simulations, Adapt to Observations: Super-Resolution of Isoprene Emissions via Unpaired Domain Adaptation

Plants emit biogenic volatile organic compounds (BVOCs), such as isoprene, significantly influencing atmospheric chemistry and climate. BVOC emissions estimated from bottom-up (BU) approaches (derived from numerical simulations) usually exhibit denser and more detailed spatial information compared to those estimated through top-down (TD) approaches (derived from satellite observations). Moreover, numerically simulated emissions are typically easier to obtain, even if they are less reliable than satellite acquisitions, which, being derived from actual measurements, are considered a more trustworthy instrument for performing chemistry and climate investigations. Given the coarseness and relative lack of satellite-derived measurements, fine-grained numerically simulated emissions could be exploited to enhance them. However, simulated (BU) and observed (TD) emissions usually differ regarding value range and spatiotemporal resolution. In this work, we present a novel deep learning (DL)-based approach to increase the spatial resolution of satellite-derived isoprene emissions, investigating the adoption of efficient domain adaptation (DA) techniques to bridge the gap between numerically simulated emissions and satellite-derived emissions, avoiding the need for retraining a specific SR algorithm on them. For this, we propose a methodology based on the CycleGAN architecture, which has been extensively used for adapting natural images (like digital photographs) of different domains. In our work, we depart from the standard CycleGAN framework, proposing additional loss terms that allow for better DA and emissions’ SR. We extensively demonstrate the proposed method’s effectiveness and robustness in restoring fine-grained patterns of observed isoprene emissions. Moreover, we compare different setups and validate our approach using different emission inventories from both domains. Eventually, we show that the proposed DA strategy paves the way towards robust SR solutions even in the case of spatial resolution mismatch between the training and testing domains and in the case of unknown testing data.

Satellite derived air pollution climatology over India and its neighboring regions: Spatio-temporal trends and insights

This study examines the spatial and temporal variations of key air pollutants, including Nitrogen Dioxide (NO₂), Carbon Monoxide (CO), Tropospheric Ozone (O₃), Sulfur Dioxide (SO₂), Aerosol Optical Depth (AOD), and Formaldehyde (HCHO) over India and neighboring regions, using satellite data from 2005 to 2022. Peak NO₂ (∼11–13 × 101⁵molecules/cm2) occurs in pre-monsoon and winter, mainly over urban centers, thermal plants, and crop-burning areas, emphasizing anthropogenic emissions. High CO levels (2.0–2.3 × 101⁸molecules/cm2) during summer dominate in Indo-Gangetic Plains (IGP), Eastern India, and Northeastern region, linked to the incomplete combustion of organic matter (e.g., natural forest fires and biofuel-based household cooking). Stable CO trends reflect effective government policies promoting cleaner fuels. Tropospheric O₃ shows a spatial gradient, with higher values in northern and coastal regions influenced by sunlight, humidity, and precursor emissions. Seasonal peaks in summer are governed by solar intensity, while the December peak over the northern region is likely due to dynamical transport from O₃-rich areas. SO₂ hotspots in IGP, central and eastern India, especially during winter (∼1.3–1.9 × 101⁵molecules/cm2), are attributed to local anthropogenic emissions and fossil fuel combustion such as coal. Long-term trends reveal rising SO₂ levels. AOD hotspots occur over IGP, Central and Southern India, with particularly high values during the pre-monsoon (0.5–0.6) and winter seasons. HCHO shows hotspots in the IGP, west coast, eastern, and northeastern regions, peaking in summer (7.5–8.5 × 101⁵molecules/cm2) due to biogenic VOC emissions. This study underscores the need for integrated policies to mitigate emissions, improve air quality, and protect public health.

In-situ online investigation of biogenic volatile organic compounds emissions from tropical rainforests in Hainan, China

Biogenic volatile organic compounds (BVOCs) emitted by tropical plants represent a significant proportion of global emissions, but the in-situ BVOC measurements in tropical rainforests are extremely sparse. Herein, a vehicle-mounted mobile monitoring system was developed for in-situ online investigations of BVOC emissions from thirty representative tree species in the tropical rainforests of Hainan Island, southern China. The results showed that monoterpenes were the primary BVOCs emitted from most broadleaf trees. Isoprene, sabinene, γ-terpinene and β-ocimene were the most abundant BVOCs. Localized canopy-scale emission factors (EFs) exhibited notable discrepancies with the defaults in the Model of Emissions of Gases and Aerosols from Nature (MEGAN), specifically with isoprene EFs being slightly lower than the model, while the EFs for monoterpenes and sesquiterpenes were 1 to 27 times higher than those in MEGAN. The BVOC emission inventory for the predominant mature forest species in Hainan Island in 2023 was further estimated to be 244.43 Gg C·yr−1, with isoprene and monoterpenes accounting for 74 % and 16 %, respectively. Additionally, unimodal monthly variation patterns were revealed, with BVOC emissions peaked in July (30.08 Gg C·yr−1) and bottomed in January (8.84 Gg C·yr−1). This study demonstrates the potential and versatility of the applied mobile platform for in-situ online measurements of plant volatiles. Our findings provide important data support for reducing uncertainties in BVOC emission estimations in tropical rainforests and for evaluating their health benefits in the context of forest therapy.

Biogenic volatile organic compounds emissions, atmospheric chemistry, and environmental implications: a review

Biogenic volatile organic compounds emissions, atmospheric chemistry, and environmental implications: a review

Implications of 1.5 K climate warming on warm-season ozone exposure and atmospheric oxidation capacity in China

Surface ozone (O3) poses significant threats to public health, agricultural crops, and plants in natural ecosystems. Global warming is likely to increase future O3 mainly by altering atmospheric photochemical reactions and enhancing biogenic volatile organic compound (BVOC) emissions. To assess the impacts of the future 1.5 K climate target on O3 concentrations and ecological O3 exposure in China, numerical simulations were conducted using the CMAQ (Community Multiscale Air Quality) model during April–October 2018. Ecological O3 exposure was estimated using six indices (i.e., M7, M24, N100, SUM60, W126, and AOT40f). The results show that the temperature rise increases the MDA8 O3 (maximum daily eight-hour average O3) concentrations by ∼3 ppb and the number of O3 exceedance days by 10–20 days in the North China Plain (NCP), Yangtze River Delta (YRD), and Sichuan Basin (SCB) regions. All O3 exposure indices show substantial increases. M24 and M7 in eastern and southern China will rise by 1–3 ppb and 2–4 ppb, respectively. N100 increases by more than 120 h in the surrounding regions of Beijing. SUM60 increases by greater than 9 ppm h−1, W126 increases by greater than 15 ppm h−1 in Shaanxi and SCB, and AOT40f increases by 6 ppm h−1 in NCP and SCB. The temperature increase also promotes atmospheric oxidation capacity (AOC) levels, with the higher AOC contributed by OH radicals in southern China but by NO3 radicals in northern China. The change in the reaction rate caused by the temperature increase has a greater influence on O3 exposure and AOC than the change in BVOC emissions.摘要地表臭氧(O₃)对公众健康, 农作物以及自然生态系统构成重大威胁. 全球变暖会增强大气光化学反应以及增加生物源挥发性有机化合物(BVOC)排放, 从而导致 O₃浓度增加. 为了评估未来 1.5 K 气候目标对中国 O₃浓度以及生态 O₃暴露的影响, 在 2018 年 4 月至 10 月期间使用 CMAQ模型进行了数值模拟. 使用六个指标(即 M7, M24, N100, SUM60, W126 和 AOT40f)估算生态 O₃暴露. 结果表明, 在华北平原,长江三角洲和四川盆地地区, 温度升高使每日最大8 小时平均 O₃浓度增加约 3 ppb, O₃超标天数增加 10–20 天.所有 O₃暴露指标均显著增加. 中国东部和南部的 M24 和 M7 将分别增加 1–3 ppb 和 2–4 ppb. 北京周边地区的 N100 增加超过 120 小时. 陕西和四川盆地的 SUM60 增加超过 9 ppm h⁻¹, W126 增加超过 15 ppm h⁻¹, 华北平原和四川盆地的 AOT40f 增加 6 ppm h⁻¹.温度升高还提升了大气氧化能力(AOC)水平, 在中国南部较高的 AOC 由羟基自由基贡献, 而在中国北部则由硝基自由基贡献. 由温度升高引起的反应速率变化对 O₃暴露和 AOC 的影响比 BVOC 排放增加带来的贡献更大.

Decline of soil volatile organic compounds from a Mediterranean deciduous forest under a future drier climate

Biogenic volatile organic compounds (BVOCs) are crucial for ecosystem functioning, atmospheric chemistry and climate. While modulation of BVOC emissions from living vegetation with biotic and abiotic factors is well documented, how these factors drive soil BVOC emissions remain less understood, particularly in Mediterranean forests. To fill this gap, this pioneer study investigates whether BVOC fluxes from natural soil covered by litter (referred to as forest soil) vary under natural and amplified long-term water stress (35% annual rain exclusion over the past 10 years) in a deciduous oak Mediterranean forest (Quercus pubescens Willd.) compared to natural climate conditions. This aim has only been tackled in a single evergreen Mediterranean forest so far. Using proton transfer reaction time of flight mass spectrometer (PTR-ToF-MS) we also provide, for the first time, a detailed diurnal cycle of soil BVOCs in relation to air temperature, air humidity, and biotic factors including soil respiration and litter content in lignin, cellulose and hemicellulose. The main results revealed that forest soil represents a source of most BVOCs (e.g., acetaldehyde, acetone, acrolein, hexanol, monoterpenes) with maximum values at mid-day (45 μgC.m-2.h-1) in response to higher temperatures while it acts as a clear sink of isoprene. Total soil BVOC emission rates, together with soil respiration, decreased by 43% after a decade of partial rain restriction. These results will contribute to enhance further modeling of soil BVOC emissions under various climate scenarios both at regional and global scales.

Impact of meteorological conditions on the biogenic volatile organic compound (BVOC) emission rate from eastern Mediterranean vegetation under drought

Abstract. A comprehensive characterization of drought's impact on biogenic volatile organic compound (BVOC) emissions is essential for understanding atmospheric chemistry under global climate change, with implications for both air quality and climate model simulation. Currently, the effects of drought on BVOC emissions are not well characterized. Our study aims to test (i) whether instantaneous changes in meteorological conditions can serve as a better proxy for drought-related changes in BVOC emissions compared to the absolute values of the meteorological parameters, as indicated by previous BVOC mixing-ratio measurements and (ii) the impact of a plant under drought stress receiving a small amount of precipitation on BVOC emission rate, and on the manner in which the emission rate is influenced by meteorological parameters. To address these objectives, we conducted our study during the warm and dry summer conditions of the eastern Mediterranean region, focusing on the impact of drought on BVOC emissions from natural vegetation. Specifically, we conducted branch-enclosure sampling measurements in Ramat Hanadiv Nature Park, under natural drought and after irrigation (equivalent to 5.5–7 mm precipitation) for six selected branches of Phillyrea latifolia, the highest BVOC emitter in this park, in September–October 2020. The samplings were followed by gas chromatography–mass spectrometry analysis for BVOC identification and flux quantification. The results corroborate the finding that instantaneous changes in meteorological parameters, particularly relative humidity (RH), offer the most accurate proxy for BVOC emission rates under drought compared to the absolute values of either temperature (T) or RH. However, after irrigation, the correlation of the detected BVOC emission rate with the instantaneous changes in RH became significantly more moderate or even reversed. Our findings highlight that under drought, the instantaneous changes in RH and to a lesser extent in T are the best proxy for the emission rate of monoterpenes (MTs) and sesquiterpenes (SQTs), whereas under moderate drought conditions, T or RH serves as the best proxy for MT and SQT emission rate, respectively. In addition, the detected emission rates of MTs and SQTs increased by 150 % and 545 %, respectively, after a small amount of irrigation.

Biogenic Volatile Organic Compound Emission and Its Response to Land Cover Changes in China During 2001–2020 Using an Improved High‐Precision Vegetation Data Set

AbstractBiogenic volatile organic compounds (BVOCs) are regarded as important precursors for ozone and secondary organic aerosol, mainly from vegetation emissions. In the context of the expanding trend of vegetation greening, the development of high‐precision vegetation data and accurate BVOC emission estimates are essential to develop effective air pollution control measures. In this study, by integrating the multi‐source vegetation cover data, we established a high‐resolution vegetation distribution (HRVD) data set to develop a high spatio‐temporal resolution emission inventory and investigated the impact of different land cover data sets on emission simulation and impact of land cover change on BVOC emissions during 2001–2020. The annual total BVOC emissions in China for 2020 was 15.66 Tg, which were mainly from trees. The emissions simulated by CNLUCC and MODIS data sets were 1.53% and 1.72% higher than those simulated by HRVD data sets, respectively. The spatial distribution of emission differences was consistent with that of land cover differences. The simulated BVOC emissions by the HRVD data set had the best accuracy as they improved the bias between modeling and observation from 69.06% to 65.35% and decreased the underprediction of observations by a factor of 2.13 compared with simulation by MEGAN default vegetation data. The annual BVOC emissions caused by changing vegetation distribution and LAIv (LAI of vegetation covered surfaces) enhanced at a rate of 72.06 Gg yr−1 during 2001–2020. LAIv was the main driver of emission variations. The total OH reactivity of the resulted BVOC emissions increased at a rate of 1.59 s−1 yr−1, with isoprene contributed the most.

Quantifying the impact of urban trees on air quality in Geneva, Switzerland

Atmospheric pollution threatens human health worldwide, with tropospheric ozone (O3) and particulate matter (PM) among the most harmful pollutants. Urban trees can reduce the concentration of air pollutants through dry deposition on their canopies and stomatal uptake. At the same time, urban trees can deteriorate air quality by emitting aerosol- and O3 precursors in the form of biogenic volatile organic compounds (BVOCs). O3 and PM removal, and BVOC emissions vary depending on the tree species. Therefore, the diversity and spatial distribution of urban trees significantly influence their impact on local air quality. This study employs a dual approach to assess and map the impact of urban trees on air quality in Geneva, Switzerland. Firstly, we use the i-Tree Eco model combined with a tree inventory (237,191 trees) to quantify BVOC emissions and PM10 (PM < 10 µm) and O3 removal at the genus level. Secondly, we develop a species-level parameterization using 51 common urban tree species to estimate the same variables and ozone-forming potential (OFP). Results show that the tree density is heterogeneous in the study area, leading to neighborhoods with greater biomass and, therefore, stronger influence by trees on local air quality. According to i-Tree Eco, urban trees in Geneva emitted 50 t of BVOCs, while removing 14 t of PM10 and 52 t of O3 in 2014. With the species-level parametrization, we estimate that urban trees removed about 66 ± 55 t of PM10 and 150 ± 96 t of O3 in 2014. However, they could also emit about 130 ± 52 t of BVOCs annually, which, under favorable conditions, can form 1153 ± 519 t of O3. Depending on the method, urban trees removed between 4 and 19 % of the anthropogenic PM10 emissions. The annual removal rates are comparable to findings in other European cities. The disparities between the two approaches are due to different parameterizations. This study could help urban planners to select adequate species for future planting programs in Geneva and more generally. It showed that the impact of urban trees on air quality is spatially heterogeneous but significant, and tightly linked to the species composition.

Screening Biogenic Volatile Organic Compounds from Common Portuguese Shrubs Using Headspace–Bar Adsorptive Microextraction (HS-BAµE)

In this study, headspace–bar adsorptive microextraction (HS-BAµE) combined with gas chromatography–mass spectrometry (GC-MS) was employed to screen the major biogenic volatile organic compounds (BVOCs) emitted by six different Portuguese shrub species (Erica scoparia L., Cistus ladanifer L., Cistus monspeliensis L., Lavandula stoechas L., Thymus villosus L., and Thymus camphoratus). The HS-BAµE/GC-MS methodology was developed, optimized, and validated using five common monoterpenoids (α-pinene, β-pinene, limonene, 1,8-cineole, and thymol) and one sesquiterpenoid (caryophyllene oxide). Under optimized experimental conditions (microextraction-sorbent phase: activated carbon (CN1), 3 h (35 °C); back-extraction: n-C6 (1 h)), good efficiencies (&gt;45%), low analytical thresholds (5.0–15.0 µg/L) and suitable linear dynamic ranges (20.0–120.0 µg/L, r2 &gt; 0.9872) were achieved, as well as acceptable intra and inter-day precisions (RSD ≤ 30.1%). Benchmarking the proposed methodology, HS-BAµE(CN1), against the reference methodology, HS-SPME(PDMS/DVB), revealed comparable analytical responses and demonstrated excellent reproducibility. Among the six shrub species studied, Thymus camphoratus exhibited the highest emissions of BVOCs from its leaves, notably, 1,8-cineole (4136.9 ± 6.3 µg/g), α-pinene (763.9 ± 0.5 µg/g), and β-pinene (259.3 ± 0.5 µg/g). It was also the only species found to release caryophyllene oxide (411.4 ± 0.3 µg/g). The observed levels suggest that these shrub species could potentially serve as fuel sources in the event of forest fires occurring under extreme conditions. In summary, the proposed methodology proved to be a favorable analytical alternative for screening BVOCs in plants. It not only exhibited remarkable performance but also demonstrated user- and eco-friendliness, cost-effectiveness, and ease of implementation.

Seasonal biogenic volatile organic compound emission factors in temperate tree species: Implications for emission estimation and ozone formation

Variability in biogenic volatile organic compound (BVOC) emissions across species and seasons poses challenges for accurate regional emission estimates and effective ozone (O3) control policies. To address this issue, we conducted in-situ measurements of emission factors for six dominant tree species in Beijing across four seasons. Subsequently, we developed monthly dynamic standard emission factors (SER-MDs) to model monthly BVOC emissions and their impacts on O3 formation at citywide and district levels. Our observations revealed pronounced seasonal differences in the BVOC composition and emission rates, as well as their responsiveness to monthly average temperature. By introducing the SER-MDs, we estimated BVOC emissions from the dominant tree species in Beijing to be 38.2 Gg yr−1, with monoterpenes and isoprene contributing 49% and 11%, respectively. This calculation reduced the overestimation associated with constant standard emission factors by 31%–38% at district level. The estimates also revealed regional differences in plant compositions rather than simple feedback from regional temperature and photosynthetically active radiation periods. Under these conditions, the maximum monthly BVOC-induced O3 concentration occurred in August and ranged from 4 to 17 μg m−3 across districts, with isoprene being the dominant contributor. Quercus mongolica and Populus tomentosa played significant roles in the formation of BVOC-induced O3 due to their strong isoprene emitting potential in July–August. These results indicate the necessity of introducing species-specific rhythms of BVOC emissions from dominant species in the development of urban BVOC emission inventories. This approach could inform the development of air pollution management policies that are consistent with the local vegetation composition and O3 pollution characteristics. For Beijing and other similar northern cities, reducing the use of tree species emitting substantial amounts of isoprene during periods of regional peak ambient O3 concentrations could constitute an effective nature-based solution for improving urban air quality in the future.

Responses of plant volatile emissions to increasing nitrogen deposition: A pilot study on Eucalyptus urophylla

Biogenic volatile organic compounds (BVOCs) significantly impact atmospheric chemistry, with emissions potentially influenced by nitrogen (N) deposition. The response of BVOC emissions to increasing N deposition remains debated. In this study, we examined Eucalyptus urophylla (E. urophylla) using three N treatments: N0, N50, and N100 (0, 50, and 100 kg N hm−2 yr−1 N addition). These treatments were applied to mature E. urophylla trees in a plantation subjected to over 10 years of soil N addition in southern China, a region with severe N deposition. Seventeen BVOCs were measured, with isoprene (36.99 %), α-pinene (38.80 %), and d-limonene (14.27 %) being the predominant compounds under natural conditions. Total BVOC emissions under N50 were nearly double those under N0 and N100, with leaf net CO2 assimilation identified as the most critical photosynthetic parameter. Isoprene and α-pinene emissions significantly increased under N50 compared to N0, while d-limonene emission decreased under N100. Stronger correlations for individual BVOCs under N50 and N100 compared to N0 might be due to differences in BVOC biosynthetic pathways and storage structures. The localized canopy-scale emission factors (EFs) under N50 were significantly higher than the default values in the Model of Emissions of Gases and Aerosols from Nature (MEGAN), suggesting the model might underestimate BVOC emissions from Eucalyptus in southern China under increased N deposition. Additionally, the secondary pollutant formation potentials of BVOCs were evaluated, identifying isoprene and monoterpenes as primary precursors of ozone and secondary organic aerosols. This study provides insights into the impacts of increased N deposition on BVOC emissions and their contribution to secondary atmospheric pollution. Updating localized BVOC EFs for subtropical tree species in southern China is crucial to reduce uncertainties in BVOC estimations under current and future N deposition scenarios.

Impact of severe drought on biogenic volatile organic compounds emissions from Sphagnum mosses in boreal peatlands

Climate change and the associated increased frequency of extreme weather events are likely to alter the emissions of biogenic volatile organic compounds (BVOCs) from boreal peatlands. Hydrologically sensitive Sphagnum mosses are keystone species in boreal peatland ecosystems that are known to emit various BVOCs. However, it is not known how their emissions respond to seasonal droughts. In this study, we quantified the effect of severe drought, and subsequent recovery, on the BVOC emissions from Sphagnum mosses using mesocosms originating from wet open and naturally drier treed boreal fens and bogs. Here we report the emissions of 30 detected BVOCs, of which isoprene was the most abundant with an average flux rate of 5.6 μg m−2 h−1 (range 0–31.9 μg m−2 h−1). The experimental 43-day ecohydrological drought reduced total BVOC and isoprene emissions. In addition, in mesocosms originating from bogs, sesquiterpene emissions decreased with the drought, while the emissions of green leaf volatiles were induced. Sesquiterpene emissions remained low even six weeks after rewetting, indicating a long and limited recovery from the drought. Our results further imply that long-term exposure to deep water tables does not decrease sensitivity of Sphagnum to an extreme drought; we did not detect differences in the emission rates or drought responses between Sphagna originating from wet open and naturally drier treed habitats. Yet, the differences between fen and bog originating Sphagna indicate local variability in the BVOC quality changes following drought, potentially altering the climate feedback of boreal peatland BVOC emissions.

Uncertainties of biogenic VOC emissions caused by land cover data and implications on ozone mitigation strategies for the Yangtze river Delta region

Biogenic volatile organic compounds (BVOC) play a crucial role in ground-level ozone formation, yet emission quantification faces considerable uncertainties stemming from input data. Land cover data, which determines the distribution of growth forms, is an essential driving input of BVOC emissions. This study explores the uncertainty in BVOC emission estimates arising from using two land cover datasets, specifically the MODIS and ESA land cover data, and the implications for ozone mitigation strategies in the Yangtze River Delta (YRD) region. By employing the MEGAN model for the year 2021, we estimated that ESA land cover data, with a finer 10 m resolution, yields a total BVOC emission estimate of 2299 Gg, which is over 52.9% higher than the MODIS dataset with a resolution of 500 m, attributed to the higher tree coverage (33.9% in ESA vs. 17.6% in MODIS) identified in the ESA dataset. We then simulated the ozone concentrations by both emission estimates with the WRF-CMAQ model. The elevated BVOC emissions based on the ESA data improved the underestimation of simulated isoprene concentrations and consequently resulted in more than 30% higher domain-averaged MDA8 ozone concentration compared to the MODIS-derived BVOC emission. Regarding ozone mitigation strategy, simulation with the ESA-based BVOC emissions results in 0.3–1.2 μg/m3 less ozone reductions compared to that with the MODIS-based emissions when reducing anthropogenic VOC emissions, but 0.7–2.9 μg/m3 higher ozone reductions when controlling anthropogenic NOx emissions. These disparities are more pronounced at the city level, highlighting the importance of accurate BVOC emission estimates for effective ozone control strategies.

The reward and penalty for ozone pollution control caused by natural sources and regional transport: A case study in Guangdong province

Ground-level O3 pollution in the Pearl River Delta region (PRD) is closely related to anthropogenic, natural emissions and regional transport. However, the interactions among different sources and natural intervention in modulating anthropogenic management have not been comprehensively assessed. Here, the WRF-CMAQ-MEGAN modeling system was utilized to simulate an O3 episode over PRD. The integrated source apportionment method (ISAM) and brute-force top-down combined with factor separation approach (BF-TD-FSA) were applied to quantify source contributions, impacts of individual or multiple sources on O3, and decouple interactions among various emissions; additionally, based on ISAM, O3 isopleths visualized MDA8 O3 response of different source types to anthropogenic perturbations. ISAM concluded considerable MDA8 O3 contributions of regional transport in PRD/NPRD (non-PRD areas in Guangdong province) (38.8 %/35.7 %), followed by anthropogenic (32.7 %/24.8 %), BVOC (biogenic volatile organic compounds, 23.8 %/20.3 %) and SNO (soil NO, ∼4 %) emissions. Compared to concentrated anthropogenic contributions, widespread natural contributions were observed across their source areas and along the transport pathways. The BF-TD also revealed that regional transport had the largest impact (>90 μg m−3) on MDA8 O3 while anthropogenic and BVOC emissions greatly affected downwind PRD (64.5 and 7.7 μg m−3). Negative synergy between anthropogenic and natural emissions (especially BVOC emission) suggested potential natural-induced intensification of anthropogenic impact during O3 management. The MDA8 O3 isopleths further demonstrated significant BVOC-induced reward and regional transport-induced penalty for anthropogenic NOx (ANOx) emission control benefits, leading to additional maximum MDA8 O3 decrease and increase by −27.5 and 13.8 μg m−3 in polluted high-emission grids. The natural-induced reward effect could impose loose requirements on anthropogenic reduction (decreased by 13.3 %–17.7 %) if there were no regional transport-induced control penalty. It is advisable to prioritize ANOx control and seek collaboration on air quality management with neighboring provinces to maximize the natural-induced control reward and achieve desired targets with minimal human efforts.

High-Resolution Modeling of Summertime Biogenic Isoprene Emissions in New York City.

As cities strive for ambitious increases in tree canopy cover and reductions in anthropogenic volatile organic compound (AVOC) emissions, accurate assessments of the impacts of biogenic VOCs (BVOCs) on air quality become more important. In this study, we aim to quantify the impact of future urban greening on ozone production. BVOC emissions in dense urban areas are often coarsely represented in regional models. We set up a high-resolution (30 m) MEGAN (The Model of Emissions of Gases and Aerosols from Nature version 3.2) to estimate summertime biogenic isoprene emissions in the New York City metro area (NYC-MEGAN). Coupling an observation-constrained box model with NYC-MEGAN isoprene emissions successfully reproduced the observed isoprene concentrations in the city core. We then estimated future isoprene emissions from likely urban greening scenarios and evaluated the potential impact on future ozone production. NYC-MEGAN predicts up to twice as much isoprene emissions in NYC as the coarse-resolution (1.33 km) Biogenic Emission Inventory System version 3.61 (BEIS) on hot summer days. We find that BVOCs drive ozone production on hot summer days, even in the city core, despite large AVOC emissions. If high isoprene emitting species (e.g., oak trees) are planted, future isoprene emissions could increase by 1.4-2.2 times in the city core, which would result in 8-19 ppbv increases in peak ozone on ozone exceedance days with current NOx concentrations. We recommend planting non- or low-isoprene emitting trees in cities with high NOx concentrations to avoid an increase in the frequency and severity of future ozone exceedance events.

Korean flowering cherry (Prunus × yedoensis Matsum.) response to elevated ozone: physiological traits and biogenic volatile organic compounds emission

Korean flowering cherry (Prunus × yedoensis Matsum.) response to elevated ozone: physiological traits and biogenic volatile organic compounds emission