Biogenic volatile organic compounds in the Earth system

Seasonal and height dynamics of volatile organic compounds in rubber plantation: Impacts on ozone and secondary organic aerosol formation

Rubber trees emit a range of volatile organic compounds (VOCs), including isoprene, monoterpenes, and sesquiterpenes, as part of their natural metabolism. These VOCs can significantly influence air quality through photochemical reactions that produce ozone and secondary organic aerosols (SOAs). This study examines the impact of VOCs detected in a rubber tree plantation in Northeastern Thailand on air quality, highlighting their role in atmospheric reactions that lead to the formation of ozone and SOAs. VOCs were collected at varying heights and seasons using Tenax-TA tubes paired with an atmospheric sampler pump and identified by gas chromatography-mass spectrometry. In total, 100 VOCs were identified, including alkanes, alkenes, terpenes, aromatics, and oxygenated VOCs. Principal Coordinate Analysis (PCoA) revealed distinct seasonal VOC profiles, with hydrocarbons, peaking in summer and terpenes in the rainy season. The Linear Mixed-Effects (LME) model indicates that VOC concentrations are more influenced by seasonal changes than by sampling heights. Secondary organic aerosol potential (SOAP) and ozone formation potential (OFP) of selected VOC species were also determined. The total SOAP ranged from 67.24 μg/m3 in summer to 17.87 μg/m3 in winter, while the total OFP ranged from 377.87 μg/m3 in summer to 139.39 μg/m3 in winter. Additionally, positive matrix factorization (PMF) analysis identified four main VOC sources: gasoline combustion (18.3 %), microbial activity (38.6 %), monoterpene emissions during latex production (15.0 %), and industrial sources (28.1 %). These findings provide essential information for managing air pollution in rubber tree plantations. By adopting focused air quality management strategies, plantation operators can mitigate the adverse effects of VOCs, promoting a healthier and more sustainable future.

The characteristics and environmental significance of BVOCs released by aquatic macrophytes

Biogenic volatile organic compounds (BVOCs) emitted by plants serve crucial biological functions and potentially impact atmospheric environment and global carbon cycling. Despite their significance, BVOC emissions from aquatic macrophytes have been relatively understudied. In this study, for the first time we identified there were 68 major BVOCs released from 34 common aquatic macrophytes, and these compounds referred to alcohols, aldehydes, alkanes, alkenes, arenes, ethers, furans, ketones, phenol. For type of BVOC emissions from different life form and phylogenetic group of aquatic macrophytes, 34 of the 68 BVOCs from emergent and submerged macrophytes are classified into alkene and alcohol compounds, over 50% BVOCs from dicotyledon and monocotyledon belong to alcohol and arene compounds. Charophyte and pteridophyte emitted significantly fewer BVOCs than dicotyledon and monocotyledon, and each of them only released 12 BVOCs. These BVOCs may be of great importance for the growth and development of macrophytes, because many BVOCs, such as azulene, (E)-β-farnesene, and dimethyl sulfide are proved to play vital roles in plant growth, defense, and information transmission. Our results confirmed that both life form and phylogenetic group of aquatic macrophytes had significantly affected the BVOC emissions form macrophytes, and suggested that the intricate interplay of internal and external factors that shape BVOC emissions from aquatic macrophytes. Thus, further studies are urgently needed to investigate the influence factors and ecological function of BVOCs released by macrophytes within aquatic ecosystem.

Examination of internal metabolome and VOCs profile of brewery yeast and their mutants producing beer with improved aroma

Volatile organic compounds (VOCs) are metabolites pivotal in determining the aroma of various products. A well-known VOC producer of industrial importance is Saccharomyces cerevisiae, partially responsible for flavor of beers and wines. We identified VOCs in beers produced by yeast strains characterized by improved aroma obtained in UV-induced mutagenesis. We observed significant increase in concentration of compounds in strains: 1214uv16 (2-phenylethyl acetate, 2- phenylethanol), 1214uv31 (2-ethyl henxan-1-ol), 1214uv33 (ethyl decanoate, caryophyllene). We observed decrease in production of 2-phenyethyl acetate in strain 1214uv33. Analysis of intracellular metabolites based on 1H NMR revealed that intracellular phenylalanine concentration was not changed in strains producing more phenylalanine related VOCs (1214uv16 and 1214uv33), so regulation of this pathway seems to be more sophisticated than is currently assumed. Metabolome analysis surprisingly showed the presence of 3-hydroxyisobutyrate, a product of valine degradation, which is considered to be absent in S. cerevisiae. Our results show that our knowledge of yeast metabolism including VOC production has gaps regarding synthesis pathways for individual metabolites and regulation mechanisms. Detailed analysis of 1214uv16 and 1214uv33 may enhance our knowledge of the regulatory mechanisms of VOC synthesis in yeast, and analysis of strain 1214uv31 may reveal the pathway of 2-ethyl henxan-1-ol biosynthesis.

Evaluation of urinary limonene metabolites as biomarkers of exposure to greenness

Exposure to plants is known to improve physical and mental health and living in areas of high vegetation is associated with better health. The addition of quantitative measures of greenness exposure at individual-level to other objective and subjective study measures will help establish cause-and-effect relationships between greenspaces and human health. Because limonene is one of the most abundant biogenic volatile organic compounds emitted by plants, we hypothesized that urinary metabolites of inhaled limonene can serve as biomarkers of exposure to greenness. To test our hypothesis, we analyzed urine samples collected from eight human volunteers after limonene inhalation or after greenness exposure using liquid chromatography-high resolution mass spectrometry-based profiling. Eighteen isomers of nine metabolites were detected in urine after limonene inhalation, and their kinetic parameters were estimated using nonlinear mixed effect models. Urinary levels of most abundant limonene metabolites were elevated after brief exposure to a forested area, and the ratio of urinary limonene metabolites provided evidence of recent exposure. The identities and structures of these metabolites were validated using stable isotope tracing and tandem mass spectral comparison. Together, these data suggest that urinary metabolites of limonene, especially uroterpenol glucuronide and dihydroperillic acid glucuronide, could be used as individualized biomarkers of greenness exposure.

Localized biogenic volatile organic compound emission inventory in China: A comprehensive review

Volatile organic compounds (VOCs) are the precursors of forming ozone (O3) and fine particulate matter (PM2.5). Accurate estimates of biogenic VOC (BVOC) emissions is essential for understanding the formation mechanism of O3 and PM2.5 pollution and precise reduction on anthropogenic emissions and thereby mitigating O3 and PM2.5 pollution. To gain comprehensive knowledge of BVOC emissions and improve the accuracy of their estimation, this study reviewed localized national, regional, and municipal emission estimations in China. From their comparisons, BVOC emission characteristics and deficiencies in the inventory compilation methodology were also investigated. The estimated BVOC emissions in China ranged between 10 and 58.9 Tg yr-1 and 10.9-18.9 Tg C yr-1, with diverse contributions for different BVOC categories. The simulated historical and future BVOC emissions exhibited an increasing trend. The uncertainty of the BVOC estimates was mainly from the applications of incomplete emission models, less localized accurate emission factors, deficient vegetation cover information, and low-resolution meteorological data in the inventory compilation. The regional and municipal BVOC emission inventories mainly focused on the Beijing-Tianjin-Hebei, Pearl River Delta, Sichuan Basin, and Yangtze River Delta regions, as well as the cities therein. For the same area, different studies reported diverse BVOC emissions by a maximum of two orders of magnitude. There is usually a lack of basic data with more detailed investigations and higher precision for estimation of BVOC emissions. By summarizing the measurements on terrestrial and marine BVOC emission fluxes, they are mainly focused on the Guangdong, Zhejiang and Jiangxi provinces, and Yellow Sea, East China Sea, and South China Sea, respectively. Expanding the temporal and spatial scales of observations is encouraged to enhance our understanding on the emissions and improve the emission estimates.

Forestation is not an easy fix

Planting trees has diverse effects on composition and climate mitigation.

Measuring BVOC emissions released by tomato plants grown in a soilless integrated rooftop greenhouse

Urban design is currently promoting the inclusion of plants in buildings. However, plants emit biogenic volatile organic compounds (BVOCs), which alone or in combination with other airborne molecules such as CO2, may result in a general increase in tropospheric pollution. Many studies have documented the effects of biotic and abiotic factors on plant BVOC responses, but few have assessed the contribution of typical CO2 levels found in indoor work and meeting spaces. To answer this question, we monitored CO2 and constitutive (MT-limonene) and induced (LOX-cis-3-hexenal) BVOC emissions of a fully developed tomato crop grown hydroponically inside an integrated rooftop greenhouse (i-RTG) in a Mediterranean climate. Two distinctive CO2 assays were performed at the level of the i-RTG by supplying or not CO2. The impact of CO2 on plant physiological emittance was then assessed, and the resulting BVOC rates were compared with reference to EU-LCI values. MT-limonene was ubiquitous among the assays and the most abundant, while LOX-cis-3-hexenal was detected only under controlled CO2 management. The highest levels detected were below the indicated LCIs and were approximately tenfold lower than the corresponding LCI for MT-limonene (50.88 vs. 5000 μg m-3) and eightfold (6.63 μg m-3) higher than the constitutive emission level for LOX-cis-3-hexenal. Over extended sampling (10 min) findings revealed a general emission decrease and significantly different CO2 concentration between the assays. Despite similar decreasing rates of predicted net photosynthesis (Pn) and stomatal conductance (gs) their correlation with decreasing CO2 under uncontrolled condition indirectly suggested a negative CO2 impact on plant emission activity. Conversely, increasing CO2 under the controlled assay showed a positive correlation with induced emissions but not with constitutive ones. Because of significantly higher levels of relative humidity registered under the uncontrolled condition, this factor was considered to affect more than CO2 the emission response and even its collection. This hypothesis was supported by literature findings and attributed to a common issue related with the sampling in static enclosure. Hence, we suggested a careful monitoring of the sampling conditions or further improvements to avoid bias and underestimation of actual emissions. Based on the main outcomes, we observed no evidence of a hazardous effect of registered CO2 rates on the BVOC emissions of tomato plant. Furthermore, because of the low BVOC levels measured in the i-RTG, we assumed as safe the recirculation of this air along building's indoor environments.

The Plant Volatile-Sensing Mechanism of Insects and Its Utilization

Plants and insects are engaged in a tight relationship, with phytophagous insects often utilizing volatile organic substances released by host plants to find food and egg-laying sites. Using plant volatiles as attractants for integrated pest management is vital due to its high efficacy and low environmental toxicity. Using naturally occurring plant volatiles combined with insect olfactory mechanisms to select volatile molecules for screening has proved an effective method for developing plant volatile-based attractant technologies. However, the widespread adoption of this technique is still limited by the lack of a complete understanding of molecular insect olfactory pathways. This paper first describes the nature of plant volatiles and the mechanisms of plant volatile perception by insects. Then, the attraction mechanism of plant volatiles to insects is introduced with the example of Cnaphalocrocis medinalis. Next, the progress of the development and utilization of plant volatiles to manage pests is presented. Finally, the functions played by the olfactory system of insects in recognizing plant volatiles and the application prospects of utilizing volatiles for green pest control are discussed. Understanding the sensing mechanism of insects to plant volatiles and its utilization will be critical for pest management in agriculture.

Distinct emissions of biogenic volatile organic compounds from temperate benthic taxa

INTRODUCTION

Biogenic volatile organic compounds (BVOCs) are emitted by all organisms as intermediate or end-products of metabolic processes. Individual BVOCs perform important physiological, ecological and climatic functions, and collectively constitute the volatilome-which can be reflective of organism taxonomy and health. Although BVOC emissions of tropical benthic reef taxa have recently been the focus of multiple studies, emissions derived from their temperate counterparts have never been characterised.

OBJECTIVES

Characterise the volatilomes of key competitors for benthic space among Australian temperate reefs.

METHODS

Six fragments/fronds of a temperate coral (Plesiastrea versipora) and a macroalga (Ecklonia radiata) from a Sydney reef site were placed within modified incubation chambers filled with seawater. Organism-produced BVOCs were captured on thermal desorption tubes using a purge-and-trap methodology, and were then analysed using GC × GC - TOFMS and multivariate tests.

RESULTS

Analysis detected 55 and 63 BVOCs from P. versipora and E. radiata respectively, with 30 of these common between species. Each taxon was characterised by a similar relative composition of chemical classes within their volatilomes. However, 14 and 10 volatiles were distinctly emitted by either E. radiata or P. versipora respectively, including the halogenated compounds iodomethane, tribromomethane, carbon tetrachloride and trichloromonofluoromethane. While macroalgal cover was 3.7 times greater than coral cover at the sampling site, P. versipora produced on average 17 times more BVOCs per cm2 of live tissue, resulting in an estimated contribution to local BVOC emission that was 4.7 times higher than E. radiata.

CONCLUSION

Shifts in benthic community composition could disproportionately impact local marine chemistry and affect how ecosystems contribute to broader BVOC emissions.

Urban flask measurements of CO2ff and CO to identify emission sources at different site types in Auckland, New Zealand

As part of the CarbonWatch-NZ research programme, air samples were collected at 28 sites around Auckland, New Zealand, to determine the atmospheric ratio (RCO) of excess (local enhancement over background) carbon monoxide to fossil CO2 (CO2ff). Sites were categorized into seven types (background, forest, industrial, suburban, urban, downwind and motorway) to observe RCO around Auckland. Motorway flasks observed RCO of 14 ± 1 ppb ppm-1 and were used to evaluate traffic RCO. The similarity between suburban (14 ± 1 ppb ppm-1) and traffic RCO suggests that traffic dominates suburban CO2ff emissions during daytime hours, the period of flask collection. The lower urban RCO (11 ± 1 ppb ppm-1) suggests that urban CO2ff emissions are comprised of more than just traffic, with contributions from residential, commercial and industrial sources, all with a lower RCO than traffic. Finally, the downwind sites were believed to best represent RCO for Auckland City overall (11 ± 1 ppb ppm-1). We demonstrate that the initial discrepancy between the downwind RCO and Auckland's estimated daytime inventory RCO (15 ppb ppm-1) can be attributed to an overestimation in inventory traffic CO emissions. After revision based on our observed motorway RCO, the revised inventory RCO (12 ppb ppm-1) is consistent with our observations. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'.

Region-wise and state-wise synthesis of vehicular emissions in India and their mitigation due to vehicular emissions standards

The implementation of different stages of Bharat Stage Emission standards (BSES) in India for reducing the vehicular emissions has been in different parts of the country at various points of time. A quantitative assessment of the emission standards in mitigating vehicular emissions at different Indian states will provide an estimate of achievable emissions standards for future norms. In this regard, the present work reports an assessment of the BS standards - BS-III, BS-IV and BS-VI in reducing the exhaust emissions in each of the Indian states. The assessment is performed through the survival fraction of the vehicles registered with different norms in the two age groups 2013-2017 and 2018-2022 and the corresponding emissions of NOx, CO, VOC, PM2.5 and BC. Over the years 2013-2022, the NOx emissions are the major contributors of vehicular emissions in all the states studied. Surprisingly, the BS-IV vehicles contributed significantly to vehicular emissions in particular states when compared to the BS-III vehicles. This urged to analyse the impact of meteorological and topographical factors on the vehicular emissions. The results revealed that the vehicular emissions are largely dependent on the temperature and altitude and with an increase in temperature and at high altitudes, the CO and VOC emissions are predominant, even in regions with low vehicle population. This finding therefore indicates that the emission limits are not the same for all over the country and meteorology dependent emission limit should be included in framing the vehicle emission norms.

Antagonism between ambient ozone increase and urbanization-oriented population migration on Chinese cardiopulmonary mortality

Ever-increasing ambient ozone (O3) pollution in China has been exacerbating cardiopulmonary premature deaths. However, the urban-rural exposure inequity has seldom been explored. Here, we assess population-scale O3 exposure and mortality burdens between 1990 and 2019 based on integrated pollution tracking and epidemiological evidence. We find Chinese population have been suffering from climbing O3 exposure by 4.3 ± 2.8 ppb per decade as a result of rapid urbanization and growing prosperity of socioeconomic activities. Rural residents are broadly exposed to 9.8 ± 4.1 ppb higher ambient O3 than the adjacent urban citizens, and thus urbanization-oriented migration compromises the exposure-associated mortality on total population. Cardiopulmonary excess premature deaths attributable to long-term O3 exposure, 373,500 (95% uncertainty interval [UI]: 240,600-510,900) in 2019, is underestimated in previous studies due to ignorance of cardiovascular causes. Future O3 pollution policy should focus more on rural population who are facing an aggravating threat of mortality risks to ameliorate environmental health injustice.

Comprehensive analysis between volatile organic compound (VOC) exposure and female sex hormones: a cross-sectional study from NHANES 2013-2016

There is growing evidence suggesting that exposure to volatile organic compounds (VOCs) can pose significant health risks, including interference with the function of the reproductive system. However, there has been a lack of research focused on the impact of common environmental VOCs on the levels of sex hormones in the general female population. In this study, we conducted a cross-sectional analysis utilizing the database of the National Health and Nutrition Examination Survey (NHANES, 2013-2016). A total of 2633 participants were included in this study. The Pearson correlation model revealed the potential of co-exposure or co-toxicity between benzene and 2,5-dimethylfuran. According to GLM models, we discovered a significant positive association between blood levels of 2,5-dimethylfuran and benzene with testosterone levels in women. Subgroup analysis further identified that the women with underweight and healthy weight might be the high-risk subgroup. Bayesian kernel machine regression (BKMR) was applied to further assess the univariate and bivariate exposure-response relationships between multiple VOCs. Our research systemically formulated the possible relationship between exposure to VOCs and female sex hormones, indicating the role of VOCs as a risk factor for endocrine disruption, especially benzene and 2,5-dimethylfuran. These findings have important implications for public health and call for further investigation.

Environmental Factors Affecting Monoterpene Emissions from Terrestrial Vegetation

Monoterpenes are volatile organic compounds that play important roles in atmospheric chemistry, plant physiology, communication, and defense. This review compiles the monoterpene emission flux data reported for different regions and plant species and highlights the role of abiotic environmental factors in controlling the emissions of biogenic monoterpenes and their emission fluxes for terrestrial plant species (including seasonal variations). Previous studies have demonstrated the role and importance of ambient air temperature and light in controlling monoterpene emissions, likely contributing to higher monoterpene emissions during the summer season in temperate regions. In addition to light and temperature dependence, other important environmental variables such as carbon dioxide (CO2), ozone (O3), soil moisture, and nutrient availability are also known to influence monoterpene emissions rates, but the information available is still limited. Throughout the paper, we identify knowledge gaps and provide recommendations for future studies.

Symbiont Identity Impacts the Microbiome and Volatilome of a Model Cnidarian-Dinoflagellate Symbiosis

The symbiosis between cnidarians and dinoflagellates underpins the success of reef-building corals in otherwise nutrient-poor habitats. Alterations to symbiotic state can perturb metabolic homeostasis and thus alter the release of biogenic volatile organic compounds (BVOCs). While BVOCs can play important roles in metabolic regulation and signalling, how the symbiotic state affects BVOC output remains unexplored. We therefore characterised the suite of BVOCs that comprise the volatilome of the sea anemone Exaiptasia diaphana ('Aiptasia') when aposymbiotic and in symbiosis with either its native dinoflagellate symbiont Breviolum minutum or the non-native symbiont Durusdinium trenchii. In parallel, the bacterial community structure in these different symbiotic states was fully characterised to resolve the holobiont microbiome. Based on rRNA analyses, 147 unique amplicon sequence variants (ASVs) were observed across symbiotic states. Furthermore, the microbiomes were distinct across the different symbiotic states: bacteria in the family Vibrionaceae were the most abundant in aposymbiotic anemones; those in the family Crocinitomicaceae were the most abundant in anemones symbiotic with D. trenchii; and anemones symbiotic with B. minutum had the highest proportion of low-abundance ASVs. Across these different holobionts, 142 BVOCs were detected and classified into 17 groups based on their chemical structure, with BVOCs containing multiple functional groups being the most abundant. Isoprene was detected in higher abundance when anemones hosted their native symbiont, and dimethyl sulphide was detected in higher abundance in the volatilome of both Aiptasia-Symbiodiniaceae combinations relative to aposymbiotic anemones. The volatilomes of aposymbiotic anemones and anemones symbiotic with B. minutum were distinct, while the volatilome of anemones symbiotic with D. trenchii overlapped both of the others. Collectively, our results are consistent with previous reports that D. trenchii produces a metabolically sub-optimal symbiosis with Aiptasia, and add to our understanding of how symbiotic cnidarians, including corals, may respond to climate change should they acquire novel dinoflagellate partners.

Insights into the Effects of Violating Statistical Assumptions for Dimensionality Reduction for Chemical "-omics" Data with Multiple Explanatory Variables

Biological volatilome analysis is inherently complex due to the considerable number of compounds (i.e., dimensions) and differences in peak areas by orders of magnitude, between and within compounds found within datasets. Traditional volatilome analysis relies on dimensionality reduction techniques which aid in the selection of compounds that are considered relevant to respective research questions prior to further analysis. Currently, compounds of interest are identified using either supervised or unsupervised statistical methods which assume the data residuals are normally distributed and exhibit linearity. However, biological data often violate the statistical assumptions of these models related to normality and the presence of multiple explanatory variables which are innate to biological samples. In an attempt to address deviations from normality, volatilome data can be log transformed. However, whether the effects of each assessed variable are additive or multiplicative should be considered prior to transformation, as this will impact the effect of each variable on the data. If assumptions of normality and variable effects are not investigated prior to dimensionality reduction, ineffective or erroneous compound dimensionality reduction can impact downstream analyses. It is the aim of this manuscript to assess the impact of single and multivariable statistical models with and without the log transformation to volatilome dimensionality reduction prior to any supervised or unsupervised classification analysis. As a proof of concept, Shingleback lizard (Tiliqua rugosa) volatilomes were collected across their species distribution and from captivity and were assessed. Shingleback volatilomes are suspected to be influenced by multiple explanatory variables related to habitat (Bioregion), sex, parasite presence, total body volume, and captive status. This work determined that the exclusion of relevant multiple explanatory variables from analysis overestimates the effect of Bioregion and the identification of significant compounds. The log transformation increased the number of compounds that were identified as significant, as did analyses that assumed that residuals were normally distributed. Among the methods considered in this work, the most conservative form of dimensionality reduction was achieved through analyzing untransformed data using Monte Carlo tests with multiple explanatory variables.

Volatility of Secondary Organic Aerosol from β-Caryophyllene Ozonolysis over a Wide Tropospheric Temperature Range

We investigated secondary organic aerosol (SOA) from β-caryophyllene oxidation generated over a wide tropospheric temperature range (213-313 K) from ozonolysis. Positive matrix factorization (PMF) was used to deconvolute the desorption data (thermograms) of SOA products detected by a chemical ionization mass spectrometer (FIGAERO-CIMS). A nonmonotonic dependence of particle volatility (saturation concentration at 298 K, C298K*) on formation temperature (213-313 K) was observed, primarily due to temperature-dependent formation pathways of β-caryophyllene oxidation products. The PMF analysis grouped detected ions into 11 compound groups (factors) with characteristic volatility. These compound groups act as indicators for the underlying SOA formation mechanisms. Their different temperature responses revealed that the relevant chemical pathways (e.g., autoxidation, oligomer formation, and isomer formation) had distinct optimal temperatures between 213 and 313 K, significantly beyond the effect of temperature-dependent partitioning. Furthermore, PMF-resolved volatility groups were compared with volatility basis set (VBS) distributions based on different vapor pressure estimation methods. The variation of the volatilities predicted by different methods is affected by highly oxygenated molecules, isomers, and thermal decomposition of oligomers with long carbon chains. This work distinguishes multiple isomers and identifies compound groups of varying volatilities, providing new insights into the temperature-dependent formation mechanisms of β-caryophyllene-derived SOA particles.

Size distributions of molecular markers for biogenic secondary organic aerosol in urban Beijing

To understand the source, formation, and seasonality of biogenic secondary organic aerosol (BSOA), a nine-stage cascade impactor was utilized to collect size-segregated particulate samples from April 2017 to January 2018 in Beijing, China. BSOA tracers derived from isoprene, monoterpene, and sesquiterpene were measured with gas chromatography-mass spectrometry. Isoprene and monoterpene SOA tracers exhibited significant seasonal variations, with a summer maximum and a winter minimum. Dominance of 2-methyltetrols (isoprene SOA tracers) with a good correlation with levoglucosan (a biomass burning tracer), which was combined with the detection of methyltartaric acids (possible indicators for aged isoprene) in summer, implies possible biomass burning and long-range transport. In contrast, sesquiterpene SOA tracer (β-caryophyllinic acid) was dominant in winter and was probably associated with the local burning of biomass. Bimodal size distributions were observed for most isoprene SOA tracers, consistent with previous laboratory experiments and field studies showing that they can be formed not only in the aerosol phase but also in the gas phase. Monoterpene SOA tracers cis-pinonic acid and pinic acid showed a coarse-mode peak (5.8-9.0 μm) in four seasons due to their volatile nature. Sesquiterpene SOA tracer β-caryophyllinic acid showed a unimodal pattern with a major fine-mode peak (1.1-2.1 μm), which is linked to local biomass burning. The tracer-yield method was used to quantify the contributions of isoprene, monoterpene, and sesquiterpene to secondary organic carbon (SOC) and SOA. The highest isoprene SOC and SOA concentrations occurred in summer (2.00 μgC m^-3 and 4.93 μg m^-3, respectively), contributing to 1.61% of OC and 5.22% of PM_2.5, respectively. These results suggest that BSOA tracers are promising tracers for understanding the source, formation, and seasonality of BSOA.

Assessment of greenhouse emissions of the green bean through the static enclosure technique

Urban green installations are extensively promoted to increase sustainable and accessible food production and simultaneously improve the environmental performance and liveability of city buildings. In addition to the multiple benefits of plant retrofitting, these installations may lead to a consistent increase in biogenic volatile organic compounds (BVOCs) in the urban environment, especially indoors. Accordingly, health concerns could limit the implementation of building-integrated agriculture. In a building-integrated rooftop greenhouse (i-RTG), throughout the whole hydroponic cycle, green bean emissions were dynamically collected in a static enclosure. Four representative BVOCs, α-pinene (monoterpene), β-caryophyllene (sesquiterpene), linalool (oxygenated monoterpene) and cis-3-hexenol (LOX derivate), were investigated in the samples collected from two equivalent sections of a static enclosure, one empty and one occupied by the i-RTG plants, to estimate the volatile emission factor (EF). Throughout the season, extremely variable BVOC levels between 0.04 and 5.36 ppb were found with occasional but not significant (P > 0.05) variations between the two sections. The highest emission rates were observed during plant vegetative development, with EFs equivalent to 78.97, 75.85 and 51.34 ng g^-1 h^-1 for cis-3-hexenol, α-pinene, and linalool, respectively; at plant maturity, all volatiles were either close to the LLOQ (lowest limit of quantitation) or not detected. Consistent with previous studies significant relationships (r ≥ 0.92; P < 0.05) were individuated within volatiles and temperature and relative humidity of the sections. However, correlations were all negative and were mainly attributed to the relevant effect of the enclosure on the final sampling conditions. Overall, levels found were at least 15 folds lower than the given Risk and LCI values of the EU-LCI protocol for indoor environments, suggesting low BVOC exposure in the i-RTG. Statistical outcomes demonstrated the applicability of the static enclosure technique for fast BVOC emissions survey inside green retrofitted spaces. However, providing high sampling performance over entire BVOCs collection is recommended to reduce sampling error and incorrect estimation of the emissions.

Spatial and species-specific responses of biogenic volatile organic compound (BVOC) emissions to elevated ozone from 2014-2020 in China

China suffered from serious and elevated ozone (O3) pollution during 2014-2020. O3 exposure increased with W126, a biologically based cumulative exposure index, at a rate of 1.738 ppm-hr yr-1. MEGAN3.1 was applied to estimate biogenic volatile organic compound (BVOC) emissions and their response to O3 pollution in China by quantifying species responses to O3 stress. In 2020, China's BVOC emissions were 23.26 Tg when considering the effects of O3 pollution, which was 1.7 % higher than that without O3 stress. Isoprene, monoterpenes, sesquiterpenes, and other VOC emissions changed by -1.0 %, 1.4 %, 15.5 %, and 2.7 %, respectively. The stimulated BVOC emissions were mainly focused on the North China Plain (NCP) and a partial area of the Tibetan Plateau, which increased by >45 %. Changes in monthly emissions differed, with the greatest increase, 181 tons (3.25 %), in August. The seasonal patterns for the impacts of O3 pollution were also distinguished spatially. The elevated O3 exposure caused BVOC emission increases of 104.7 Gg yr-1 during 2014-2020, with isoprene, monoterpenes, sesquiterpenes, and other VOCs contributing -18.6 %, 27.5 %, 40.4 %, and 50.8 %, respectively. The greatest increase in emissions appeared on the NCP and eastern and central China, with annual increases of >100 tons per grid (36 km × 36 km). The interannual variations in BVOC emissions also displayed different seasonal patterns.

Underestimated contribution of fugitive emission to VOCs in pharmaceutical industry based on pollution characteristics, odorous activity and health risk assessment

Fugitive emission has been becoming an important source of volatile organic compounds (VOCs) in pharmaceutical industry, but the exact contribution of fugitive emission remains incompletely understood. In present study, pollution characteristics, odorous activity and health risk of stack and fugitive emissions of VOCs from four functional units (e.g., workshop, sewage treatment station, raw material storage and hazardous waste storage) of three representative pharmaceutical factories were investigated. Workshop was the dominant contributor to VOCs of fugitive emission in comparison with other functional units. Extreme high concentration of VOCs from fugitive emission in unsealed workshop (94.87 mg/m³) was observed relative to sealed one (1.18 mg/m³), accounting for 31% and 5% of total VOCs, respectively. Fugitive emission of VOCs in the unsealed workshop mainly consisted of n-hexane, 1-hexene and dichloromethane. Odorous activity indexes and non-cancer hazard ratios of these VOCs from fugitive emission in the unsealed workshop were as high as that from stack exhaust. Furthermore, cancer risk of dichloromethane from fugitive emission and stack exhaust was up to (1.6-1.8) × 10^-5. Odorous activity or health risk index of the VOCs from fugitive emission was up to 13 or 11 times of the corresponding threshold value, posing remarkable health threat on pharmaceutical workers. Our findings highlighted the possibly underestimated contribution of fugitive emission on VOCs in the pharmaceutical industry.

Effects of Plant-Emitted Monoterpenes on Anxiety Symptoms: A Propensity-Matched Observational Cohort Study

Immersive experiences in green areas, particularly in forests, have long been known to produce beneficial effects for human health. However, the exact determinants and mechanisms leading to healthy outcomes remain to be elucidated. The purpose of this observational cohort study was to investigate whether inhaling plant-emitted biogenic volatile compounds, namely monoterpenes (MTs), can produce specific effects on anxiety symptoms. Data from 505 subjects participating in 39 structured forest therapy sessions at different Italian sites were collected. The air concentration of monoterpenes was measured at each site. STAI state questionnaires were administered before and after the sessions as a measure of anxiety. A propensity score matching analysis was then performed, considering an above-average exposure to inhalable air MTs as the treatment. The estimated effect was -1.28 STAI-S points (95% C.I. -2.51 to -0.06, p = 0.04), indicating that the average effect of exposure to high MT air concentrations during forest therapy sessions was to decrease anxiety symptoms.

Emissions of biogenic volatile organic compounds from adjacent boreal fen and bog as impacted by vegetation composition

Peatland ecosystems emit biogenic volatile organic compounds (BVOC), which have a net cooling impact on the climate. However, the quality and quantity of BVOC emissions, and how they are regulated by vegetation and peatland type remain poorly understood. Here we measured BVOC emissions with dynamic enclosures from two major boreal peatland types, a minerotrophic fen and an ombrotrophic bog situated in Siikaneva, southern Finland and experimentally assessed the role of vegetation by removing vascular vegetation with or without the moss layer. Our measurements from four campaigns during growing seasons in 2017 and 2018 identified emissions of 59 compounds from nine different chemical groups. Isoprene accounted for 81 % of BVOC emissions. Measurements also revealed uptake of dichloromethane. Total BVOC emissions and the emissions of isoprene, monoterpenoids, sesquiterpenes, homoterpenes, and green leaf volatiles were tightly connected to vascular plants. Isoprene and sesquiterpene emissions were associated with sedges, whereas monoterpenoids and homoterpenes were associated with shrubs. Additionally, isoprene and alkane emissions were higher in the fen than in the bog and they significantly contributed to the higher BVOC emissions from intact vegetation in the fen. During an extreme drought event in 2018, emissions of organic halides were absent. Our results indicate that climate change with an increase in shrub cover and increased frequency of extreme weather events may have a negative impact on total BVOC emissions that otherwise are predicted to increase in warmer temperatures. However, these changes also accompanied a change in BVOC emission quality. As different compounds differ in their capacity to form secondary organic aerosols, the ultimate climate impact of peatland BVOC emissions may be altered.

Metabolomic Profile of Volatile Organic Compounds from Leaves of Cashew Clones by HS-SPME/GC-MS for the Identification of Candidates for Anthracnose Resistance Markers

Anthracnose caused by Colletotrichum gloeosporioides affects the leaves, inflorescences, nuts, and peduncles of cashew trees (Anacardium occidentale). The use of genetically improved plants and the insertion of dwarf cashew clones that are more resistant to phytopathogens are strategies to minimize the impact of anthracnose on cashew production. However, resistance mechanisms related to the biosynthesis of secondary metabolites remain unknown. Thus, this study promoted the investigation of the profile of volatile organic compounds of resistant cashew clone leaves ('CCP 76', 'BRS 226' and 'BRS 189') and susceptible ('BRS 265') to C. gloeosporioides, in the periods of non-infection and infection of the pathogen in the field (July-December 2019 - Brazil). Seventy-eight compounds were provisionally identified. Chemometric analyses, such as Principal Component Analysis (PCA), Discriminating Partial Least Squares Analysis (PLS-DA), Discriminating Analysis of Orthogonal Partial Least Squares (OPLS-DA), and Hierarchical Cluster Analysis (HCA), separated the samples into different groups, highlighting hexanal, (E)-hex-2-enal, (Z)-hex-2-en-1-ol, (E)-hex-3-en-1-ol, in addition to α-pinene, α-terpinene, γ-terpinene, β-pinene, and δ-3-carene, in the samples of the resistant clones in comparison to the susceptible clone. According to the literature, these metabolites have antimicrobial activity and are therefore chemical marker candidates for resistance to C. gloeosporioides in cashew trees.

Volatile responses of dwarf birch to mimicked insect herbivory and experimental warming at two elevations in Greenlandic tundra

Plants release a complex blend of volatile organic compounds (VOCs) in response to stressors. VOC emissions vary between contrasting environments and increase with insect herbivory and rising temperatures. However, the joint effects of herbivory and warming on plant VOC emissions are understudied, particularly in high latitudes, which are warming fast and facing increasing herbivore pressure. We assessed the individual and combined effects of chemically mimicked insect herbivory, warming, and elevation on dwarf birch (Betula glandulosa) VOC emissions in high-latitude tundra ecosystems in Narsarsuaq, South Greenland. We hypothesized that VOC emissions and compositions would respond synergistically to warming and herbivory, with the magnitude differing between elevations. Warming increased emissions of green leaf volatiles (GLVs) and isoprene. Herbivory increased the homoterpene, (E)-4,8-dimethyl-1,3,7-nonatriene, emissions, and the response was stronger at high elevation. Warming and herbivory had synergistic effects on GLV emissions. Dwarf birch emitted VOCs at similar rates at both elevations, but the VOC blends differed between elevations. Several herbivory-associated VOC groups did not respond to herbivory. Harsher abiotic conditions at high elevations might not limit VOC emissions from dwarf birch, and high-elevation plants might be better at herbivory defense than assumed. The complexity of VOC responses to experimental warming, elevation, and herbivory are challenging our understanding and predictions of future VOC emissions from dwarf birch-dominated ecosystems.

New particle formation at a peri-urban agricultural site

New Particle Formation (NPF) is a major source of ultrafine particles that affect both air quality and climate. Despite emissions from agricultural activities having a strong potential to lead to NPF, little is known about NPF within agricultural environments. The aim of the present study was to investigate the occurrence of NPF events at an agricultural site, and any potential relationship between agricultural emissions and NPF events. A field campaign was conducted for 3 months at the FR-Gri-ICOS site (France), at an experimental farm 25 km west of Paris city centre. 16 NPF events have been identified from the analysis of particle number size distributions; 8 during the daytime, and 8 during the night-time. High solar radiation and ozone mixing ratios were observed during the days NPF occurred, suggesting photochemistry plays a key role in daytime NPF. These events were also associated with higher levels of VOCs such as isoprene, methanol, or toluene compared to non-event days. However, ammonia levels were lower during daytime NPF events, contributing to the hypothesis that daytime NPF events were not related to agricultural activities. On the other hand, temperature and ozone were lower during the nights when NPF events were observed, whereas relative humidity was higher. During these nights, higher concentrations of NO₂ and ammonia were observed. As a result, agricultural activities, in particular the spreading of fertiliser on surrounding crops, are suspected to contribute to night-time NPF events. Finally, all the identified NPF events were also observed at SIRTA monitoring station 20 km from the FR-Gri ICOS site, showing that both night-time and daytime NPF events were regional processes. We hypothesise that night-time NPF may be related to fertiliser spreading over a regional scale, as opposed to the local activities at the farm. To our knowledge, this is the first time night-time NPF has been observed in the agricultural context.

Contrasting terpene emissions from canopy and understory vegetation in response to increases in nitrogen deposition and seasonal changes in precipitation

Given global change and shifts in climate are expected to increase BVOC emissions, the quantification of links between environmental conditions, plant physiology, and terpene emission dynamics is required to improve model predictions of ecosystem responses to increasing nitrogen deposition and changes in precipitation regimes. Here, we conducted a two-factor field experiment in sub-tropical forest plots to determine effects of N addition (N), precipitation change (PC), and NP (N and PC combined treatment) on wet and dry season terpene emissions and leaf photosynthetic parameters from canopy and understory species. Changes of β-ocimene and sabinene under PC and NP in the wet season (0.4-5.6-fold change) were the largest contributor to changes in total terpene emissions. In the dry season, the standardized total terpene emission rate was enhanced by 144.9% under N addition and 185.7% under PC for the understory species, while the total terpene emission rate was lower under NP than N addition and PC, indicating that N addition tended to moderate increases in PC-induced understory total terpene emissions. In the wet season, the total terpene emission rate under N and PC was close to ambient conditions for the canopy species, while the total terpene emission rate was enhanced by 54.6% under NP, indicating that N and PC combined treatment had an additive effect on canopy total terpene emissions. Total terpene emission rates increased with rates of net leaf photosynthesis (P_n) and transpiration (Tr) and there was a decoupling between terpene emission rates and P_n under NP, indicating that complex effects between PC and N decreased the regularity of single-factor effects. We recommend that N and PC interaction effects are included in models for the prediction of terpene emissions, particularly from canopy vegetation during the wet season as a major source of forest ecosystem terpene emissions.

Thermal sensitivity across forest vertical profiles: patterns, mechanisms, and ecological implications

Rising temperatures are influencing forests on many scales, with potentially strong variation vertically across forest strata. Using published research and new analyses, we evaluate how microclimate and leaf temperatures, traits, and gas exchange vary vertically in forests, shaping tree, and ecosystem ecology. In closed-canopy forests, upper canopy leaves are exposed to the highest solar radiation and evaporative demand, which can elevate leaf temperature (T_leaf ), particularly when transpirational cooling is curtailed by limited stomatal conductance. However, foliar traits also vary across height or light gradients, partially mitigating and protecting against the elevation of upper canopy T_leaf . Leaf metabolism generally increases with height across the vertical gradient, yet differences in thermal sensitivity across the gradient appear modest. Scaling from leaves to trees, canopy trees have higher absolute metabolic capacity and growth, yet are more vulnerable to drought and damaging T_leaf than their smaller counterparts, particularly under climate change. By contrast, understory trees experience fewer extreme high T_leaf 's but have fewer cooling mechanisms and thus may be strongly impacted by warming under some conditions, particularly when exposed to a harsher microenvironment through canopy disturbance. As the climate changes, integrating the patterns and mechanisms reviewed here into models will be critical to forecasting forest-climate feedback.

Impacts of Drought and Rehydration Cycles on Isoprene Emissions in Populus nigra Seedlings

The volatile organic compounds emitted by plants significantly impact the atmospheric environment. The impacts of drought stress on the biogenic volatile organic compound (BVOC) emissions of plants are still under debate. In this study, the effects of two drought-rehydration cycle groups with different durations on isoprene emissions from Populus nigra (black poplar) seedlings were studied. The P. nigra seedlings were placed in a chamber that controlled the soil water content, radiation, and temperature. The daily emissions of isoprene and physiological parameters were measured. The emission rates of isoprene (F_iso) reached the maximum on the third day (D3), increasing by 58.0% and 64.2% compared with the controlled groups, respectively, and then F_iso significantly decreased. Photosynthesis decreased by 34.2% and 21.6% in D3 in the first and second groups, respectively. After rehydration, F_iso and photosynthesis recovered fully in two groups. However, F_iso showed distinct inconsistencies in two groups, and the recovery rates of F_iso in the second drought group were slower than the recovery rates of F_iso in the first groups. The response of BVOC emissions during the drought-rehydration cycle was classified into three phases, including stimulated, inhibited, and restored after rehydration. The emission pattern of isoprene indicated that isoprene played an important role in the response of plants to drought stress. A drought-rehydration model was constructed, which indicated the regularity of BVOC emissions in the drought-rehydration cycle. BVOC emissions were extremely sensitive to drought, especially during droughts of short duration. Parameters in computational models related to BVOC emissions of plants under drought stress should be continuously improved.

Chiral monoterpenes reveal forest emission mechanisms and drought responses

Monoterpenes (C₁₀H₁₆) are emitted in large quantities by vegetation to the atmosphere (>100 TgC year^-1), where they readily react with hydroxyl radicals and ozone to form new particles and, hence, clouds, affecting the Earth's radiative budget and, thereby, climate change^1-3. Although most monoterpenes exist in two chiral mirror-image forms termed enantiomers, these (+) and (-) forms are rarely distinguished in measurement or modelling studies^4-6. Therefore, the individual formation pathways of monoterpene enantiomers in plants and their ecological functions are poorly understood. Here we present enantiomerically separated atmospheric monoterpene and isoprene data from an enclosed tropical rainforest ecosystem in the absence of ultraviolet light and atmospheric oxidation chemistry, during a four-month controlled drought and rewetting experiment⁷. Surprisingly, the emitted enantiomers showed distinct diel emission peaks, which responded differently to progressive drying. Isotopic labelling established that vegetation emitted mainly de novo-synthesized (-)-α-pinene, whereas (+)-α-pinene was emitted from storage pools. As drought progressed, the source of (-)-α-pinene emissions shifted to storage pools, favouring cloud formation. Pre-drought mixing ratios of both α-pinene enantiomers correlated better with other monoterpenes than with each other, indicating different enzymatic controls. These results show that enantiomeric distribution is key to understanding the underlying processes driving monoterpene emissions from forest ecosystems and predicting atmospheric feedbacks in response to climate change.

Impacts of elevation on plant traits and volatile organic compound emissions in deciduous tundra shrubs

The northernmost regions of our planet experience twice the rate of climate warming compared to the global average. Despite the currently low air temperatures, tundra shrubs are known to exhibit high leaf temperatures and are increasing in height due to warming, but it is unclear how the increase in height will affect the leaf temperature. To study how temperature, soil moisture, and changes in light availability influence the physiology and emissions of climate-relevant volatile organic compounds (VOCs), we conducted a study on two common deciduous tundra shrubs, Salix glauca (separating males and females for potential effects of plant sex) and Betula glandulosa, at two elevations in South Greenland. Low-elevation Salix shrubs were 45% taller, but had 37% lower rates of net CO₂ assimilation and 63% lower rates of isoprene emission compared to high-elevation shrubs. Betula shrubs showed 40% higher stomatal conductance and 24% higher glandular trichome density, in the low-elevation valley, compared to those from the high-elevation mountain slope. Betula green leaf volatile emissions were 235% higher at high elevation compared to low elevation. Male Salix showed a distinct VOC blend and emitted 55% more oxygenated VOCs, compared to females, possibly due to plant defense mechanisms. In our light response curves, isoprene emissions increased linearly with light intensity, potentially indicating adaptation to strong light. Leaf temperature decreased with increasing Salix height, at 4 °C m^-1, which can have implications for plant physiology. However, no similar relationship was observed for B. glandulosa. Our results highlight that tundra shrub traits and VOC emissions are sensitive to temperature and light, but that local variations in soil moisture strongly interact with temperature and light responses. Our results suggest that effects of climate warming, alone, poorly predict the actual plant responses in tundra vegetation.

Seasonal shifts in isoprenoid emission composition from three hyperdominant tree species in central Amazonia

Volatile isoprenoids regulate plant performance and atmospheric processes, and Amazon forests comprise the dominant source to the global atmosphere. Still, there is a poor understanding of how isoprenoid emission capacities vary in response to ecophysiological and environmental controls in Amazonian ecosystems. We measured isoprenoid emission capacities of three Amazonian hyperdominant tree species - Protium hebetatum, Eschweilera grandiflora, Eschweilera coriacea - across seasons and along a topographic and edaphic environmental gradient in the central Amazon. From wet to dry season, both photosynthesis and isoprene emission capacities strongly declined, while emissions increased among the heavier isoprenoids: monoterpenes and sesquiterpenes. Plasticity across habitats was most evident in P. hebetatum, which emitted sesquiterpenes only in the dry season, at rates that significantly increased along the hydro-topographic gradient from white sands (shallow root water access) to uplands (deep water table). We suggest that emission composition shifts are part of a plastic response to increasing abiotic stress (e.g. heat and drought) and reduced photosynthetic supply of substrates for isoprenoid synthesis. Our comprehensive measurements suggest that more emphasis should be placed on other isoprenoids, besides isoprene, in the context of abiotic stress responses. Shifting emission compositions have implications for atmospheric responses because of the strong variation in reactivity among isoprenoid compounds.

The Application of In Situ Methods to Monitor VOC Concentrations in Urban Areas—A Bibliometric Analysis and Measuring Solution Review

Urbanisation development affects urban vegetation both directly and indirectly. Since this process usually involves a dramatic change in land use, it is seen as likely to cause ecological pressure on local ecosystems. All forms of human activity, including urbanisation of areas close to residential buildings, significantly impact air quality. This study aims to identify and characterise different measurement solutions of VOCs, allowing the quantification of total and selective compounds in a direct at source (in situ) manner. Portable devices for direct testing can generally be divided into detectors, chromatographs, and electronic noses. They differ in parameters such as operating principle, sensitivity, measurement range, response time, and selectivity. Direct research allows us to obtain measurement results in a short time, which is essential from the point of view of immediate reaction in the case of high concentrations of tested compounds and the possibility of ensuring the well-being of people. The paper also attempts to compare solutions and devices available on the market and assess their application.

A Modeling Approach for Quantifying Human-Beneficial Terpene Emission in the Forest: A Pilot Study Applying to a Recreational Forest in South Korea

(1) Background: Recent economic developments in South Korea have shifted people’s interest in forests from provisioning to cultural services such as forest healing. Although policymakers have attempted to designate more forests for healing purposes, there are few established standards for carrying out such designations based on the quantified estimation. (2) Methods: We suggest a modeling approach to estimate and analyze the emission rate of human-beneficial terpenes. For this purpose, we adopted and modified the Model of Emissions of Gases and Aerosols from Nature (MEGAN), a commonly used biogenic volatile organic compounds (BVOCs) estimation model which was suitable for estimating the study site’s terpene emissions. We estimated the terpene emission rate for the whole year and analyzed the diurnal and seasonal patterns. (3) Results: The results from our model correspond well with other studies upon comparing temporal patterns and ranges of values. According to our study, the emission rate of terpenes varies significantly temporally and spatially. The model effectively predicted spatiotemporal patterns of terpene emission in the study site. (4) Conclusions: The modeling approach in our study is suitable for quantifying human-beneficial terpene emission and helping policymakers and forest managers plan the efficient therapeutic use of forests.

High-spatial-resolution VOCs emission from the petrochemical industries and its differential regional effect on soil in typical economic zones of China

Volatile organic compounds (VOCs) are toxic to the ecological environment. The emission of VOCs into the atmosphere has already caused attention. However, few studies focus on their regional effects on soil. As a major VOCs source in China, research on the effect of petrochemical industry on the environment is urgent and essential for regional control and industrial layout. This study established national VOCs emission inventory of five petrochemical sub-industries and spatial distribution based on consumption of raw material or products' yield and 28,888 factories. The VOCs emissions showed continuously increasing trend from 2008 to 2019, with cumulative 1.83 × 10⁷ t, wherein these from rapid economic development zones accounted for 66.10%. The detected concentrations of VOCs in various industries combined with meteorological parameters were used in Resistance Model to quantify regional dry deposition. Higher concentrations of 111 VOC species were 238.27, 260.01, 207.54 μg·m^-3 from large-scale enterprises for crude oil and natural gas extraction, oil processing, synthetic rubber and resin, leading to higher deposition ratios of 0.81%-0.94%, 0.70%-0.81%, 1.50%-1.75% in rapid economic development zones, respectively. The regional climate condition played a dominant role. Annual VOCs dry deposition amount in rapid economic development zones was calculated to be totally 6.38 × 10³ t using obtained deposition ratios and emissions, with 3.21 × 10³ t in Bohai Economic Rim (BER), 2.42 × 10³ t in Yangtze River Economic Belt (YREB), 748.43 t in Pearl River Delta (PRD). Generally, crude oil and natural gas extraction, oil processing, synthetic rubber and resin contributed 13.09%, 57.77% and 29.14%, respectively. The proportion of synthetic rubber and resin for dry deposition increased by 5.04%-18.81% compared with VOCs emissions in BER and YREB. In contrast, it declined from 45.52% for emission to 29.86% for deposition due to absolute dominance of small-scale enterprises in PRD. Overall, VOCs control from oil processing was significant, especially in BER.

Ozone Impact on Emission of Biogenic Volatile Organic Compounds in Three Tropical Tree Species From the Atlantic Forest Remnants in Southeast Brazil

Plants emit a broad number of Biogenic Volatile Organic Compounds (BVOCs) that can impact urban ozone (O₃) production. Conversely, the O₃ is a phytotoxic pollutant that causes unknown alterations in BVOC emissions from native plants. In this sense, here, we characterized the constitutive and O₃-induced BVOCs for two (2dO₃) and four (4dO₃) days of exposure (O₃ dose 80 ppb) and evaluated the O₃ response by histochemical techniques to detect programmed cell death (PCD) and hydrogen peroxide (H₂O₂) in three Brazilian native species. Croton floribundus Spreng, Astronium graveolens Jacq, and Piptadenia gonoacantha (Mart.) JF Macbr, from different groups of ecological succession (acquisitive and conservative), different carbon-saving defense strategies, and specific BVOC emissions. The three species emitted a very diverse BVOC composition: monoterpenes (MON), sesquiterpenes (SEQ), green leaf volatiles (GLV), and other compounds (OTC). C. floribundus is more acquisitive than A. graveolens. Their most representative BVOCs were methyl salicylate-MeSA (OTC), (Z) 3-hexenal, and (E)-2-hexenal (GLV), γ-elemene and (-)-β-bourbonene (SEQ) β-phellandrene and D-limonene (MON), while in A. graveolens were nonanal and decanal (OTC), and α-pinene (MON). Piptadenia gonoachanta is more conservative, and the BVOC blend was limited to MeSA (OTC), (E)-2-hexenal (GLV), and β-Phellandrene (MON). The O₃ affected BVOCs and histochemical traits of the three species in different ways. Croton floribundus was the most O₃ tolerant species and considered as an SEQ emitter. It efficiently reacted to O₃ stress after 2dO_3, verified by a high alteration of BVOC emission, the emergence of the compounds such as α-Ionone and trans-ß-Ionone, and the absence of H₂O₂ detection. On the contrary, A. graveolens, a MON-emitter, was affected by 2dO₃ and 4dO₃, showing increasing emissions of α-pinene and β-myrcene, (MON), γ-muurolene and β-cadinene (SEQ) and H₂O₂ accumulation. Piptadenia gonoachanta was the most sensitive and did not respond to BVOCs emission, but PCD and H₂O₂ were highly evidenced. Our results indicate that the BVOC blend emission, combined with histochemical observations, is a powerful tool to confirm the species' tolerance to O₃. Furthermore, our findings suggest that BVOC emission is a trade-off associated with different resource strategies of species indicated by the changes in the quality and quantity of BVOC emission for each species.

Greenland Ice Sheet Surfaces Colonized by Microbial Communities Emit Volatile Organic Compounds

Volatile organic compounds (VOCs) are emitted by organisms for a range of physiological and ecological reasons. They play an important role in biosphere–atmosphere interactions and contribute to the formation of atmospheric secondary aerosols. The Greenland ice sheet is home to a variety of microbial communities, including highly abundant glacier ice algae, yet nothing is known about the VOCs emitted by glacial communities. For the first time, we present VOC emissions from supraglacial habitats colonized by active microbial communities on the southern Greenland ice sheet during July 2020. Emissions of C5–C30 compounds from bare ice, cryoconite holes, and red snow were collected using a push–pull chamber active sampling system. A total of 92 compounds were detected, yielding mean total VOC emission rates of 3.97 ± 0.70 μg m–2 h–1 from bare ice surfaces (n = 31), 1.63 ± 0.13 μg m–2 h–1 from cryoconite holes (n = 4), and 0.92 ± 0.08 μg m–2 h–1 from red snow (n = 2). No correlations were found between VOC emissions and ice surface algal counts, but a weak positive correlation (r = 0.43, p = 0.015, n = 31) between VOC emission rates from bare ice surfaces and incoming shortwave radiation was found. We propose that this may be due to the stress that high solar irradiance causes in bare ice microbial communities. Acetophenone, benzaldehyde, and phenylmaleic anhydride, all of which have reported antifungal activity, accounted for 51.1 ± 11.7% of emissions from bare ice surfaces, indicating a potential defense strategy against fungal infections. Greenland ice sheet microbial habitats are, hence, potential sources of VOCs that may play a role in supraglacial microbial interactions, as well as local atmospheric chemistry, and merit future research efforts.

Responses in growth and emissions of biogenic volatile organic compounds in Scots pine, Norway spruce and silver birch seedlings to different warming treatments in a controlled field experiment

We investigated the responses in growth and emissions of biogenic volatile organic compounds (BVOCs) in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies [L.] Karst.) and silver birch (Betula pendula Roth) seedlings to a simulated climate warming of +2 °C (T2) and +4 °C (T4), compared to the ambient conditions, during two growing seasons (2019-2020) in a controlled field experiment in central Finland. In all seedlings, height was measured weekly. Diameter was measured continuously for one seedling from each tree species per plot. For shoot and root biomass measurements, half of the seedlings were harvested at end of the first growing season and the rest at the end of the second growing season. Foliage BVOC emission rates were measured at the end of the second growing season. Biomass, height, and diameter growth of silver birch did benefit the most from warming in both growing seasons. In the Scots pine and Norway spruce seedlings, height and diameter growth increased with increasing temperature in the second growing season, more so in Scots pine. Overall, the shoot and root biomass of conifer seedlings increased with increasing temperature. In the conifer seedlings, warming increased biomass and diameter growth more than height growth, due to their predetermined height growth pattern. The warming increased BVOC emissions more clearly in silver birch, whilst the BVOC emissions were in conifers less sensitive to temperature variation. Based on our findings, silver birch seedlings could be expected to benefit the most from warmer growing conditions and Norway spruce the least.

Variation in the ratio of compounds in a plant volatile blend during transmission by wind

For plant volatiles to mediate interactions in tritrophic systems, they must convey accurate and reliable information to insects. However, it is unknown whether the ratio of compounds in plant volatile blends remains stable during wind transmission. In this study, volatiles released from an odor source were collected at different points in a wind tunnel and analyzed. The variation in the amounts of volatiles collected at different points formed a rough cone shape. The amounts of volatiles collected tended to decrease with increasing distance from the odor source. Principal component analyses showed that the volatile profiles were dissimilar among different collection points. The profiles of volatiles collected nearest the odor source were the most similar to the released odor. Higher wind speed resulted in a clearer spatial distribution of volatile compounds. Thus, variations in the ratios of compounds in odor plumes exist even during transport over short distances.

Will a Transition to Timber Construction Cool the Climate?

Timber construction is on the rise and its contribution to climate change mitigation has been widely discussed by scientists and practitioners alike. As midrise building with wood in cities spreads, it will lead to fundamental and systemic change in forests, the manufacturing of construction materials, and the character and performance of the built environment. In this paper, we discuss the multifaceted implications of the transition to building with timber in cities for climate, which include greenhouse gas emissions but also go beyond those potential benefits. We demonstrate that while a transition to timber cities can have a balancing effect on the global carbon cycle, the other accompanying effects may enhance, reduce, or diminish that effect on climate. A collaboration of practitioners with scientists will be required to steer this transition in a climate-friendly direction.

Influence of increased nutrient availability on biogenic volatile organic compound (BVOC) emissions and leaf anatomy of subarctic dwarf shrubs under climate warming and increased cloudiness

BACKGROUND AND AIMS

Climate change is subjecting subarctic ecosystems to elevated temperature, increased nutrient availability and reduced light availability (due to increasing cloud cover). This may affect subarctic vegetation by altering the emissions of biogenic volatile organic compounds (BVOCs) and leaf anatomy. We investigated the effects of increased nutrient availability on BVOC emissions and leaf anatomy of three subarctic dwarf shrub species, Empetrum hermaphroditum, Cassiope tetragona and Betula nana, and if increased nutrient availability modifies the responses to warming and shading.

METHODS

Measurements of BVOCs were performed in situ in long-term field experiments in the Subarctic using a dynamic enclosure system and collection of BVOCs into adsorbent cartridges analysed by gas chromatography-mass spectrometry. Leaf anatomy was studied using light microscopy and scanning electron microscopy.

KEY RESULTS

Increased nutrient availability increased monoterpene emission rates and altered the emission profile of B. nana, and increased sesquiterpene and oxygenated monoterpene emissions of C. tetragona. Increased nutrient availability increased leaf tissue thicknesses of B. nana and C. tetragona, while it caused thinner epidermis and the highest fraction of functional (intact) glandular trichomes for E. hermaphroditum. Increased nutrient availability and warming synergistically increased mesophyll intercellular space of B. nana and glandular trichome density of C. tetragona, while treatments combining increased nutrient availability and shading had an opposite effect in C. tetragona.

CONCLUSIONS

Increased nutrient availability may enhance the protection capacity against biotic and abiotic stresses (especially heat and drought) in subarctic shrubs under future warming conditions as opposed to increased cloudiness, which could lead to decreased resistance. The study emphasizes the importance of changes in nutrient availability in the Subarctic, which can interact with climate warming and increased cloudiness effects.

Short-term warming does not affect intrinsic thermotolerance but induces strong sustaining photoprotection in tropical evergreen citrus genotypes

Consequences of warming and postwarming events on photosynthetic thermotolerance (P_T ) and photoprotective responses in tropical evergreen species remain elusive. We chose Citrus to answer some of the emerging questions related to tropical evergreen species' P_T behaviour including (i) how wide is the genotypic variation in P_T ? (ii) how does P_T respond to short-term warming and (iii) how do photosynthesis and photoprotective functions respond over short-term warming and postwarming events? A study on 21 genotypes revealed significant genotypic differences in P_T , though these were not large. We selected five genotypes with divergent P_T and simulated warming events: T_max 26/20°C (day-time highest maximum/night-time lowest maximum) (Week 1) < T_max 33/30°C (Week 2) < T_max 36/32°C (Week 3) followed by T_max 26/16°C (Week 4, recovery). The P_T of all genotypes remained unaltered despite strong leaf megathermy (leaf temperature > air temperature) during warming events. Though moderate warming showed genotype-specific stimulation in photosynthesis, higher warming unequivocally led to severe loss in net photosynthesis and induced higher nonphotochemical quenching. Even after a week of postwarming, photoprotective mechanisms strongly persisted. Our study points towards a conservative P_T in evergreen citrus genotypes and their need for sustaining higher photoprotection during warming as well as postwarming recovery conditions.

Effects of elevated ozone on the emission of volatile isoprenoids from flowers and leaves of rose (Rosa sp.) varieties

Tropospheric ozone (O₃) affects isoprenoid emissions, and floral emissions in particular, which may result in potential impacts on the interactions of plants with other organisms. The effects of ozone (O₃) on isoprenoid emissions have been investigated for many years, while knowledge on O₃ effects on floral emissions is still scarce and the relevant mechanism has not been clarified so far. We investigated the effects of O₃ on floral and foliar isoprenoid emissions (mainly isoprene, monoterpenes and sesquiterpenes) and their synthase substrates from three rose varieties (CH, Rosa chinensis Jacq. var. chinensis; SA, R. hybrida 'Saiun'; MO, R. hybrida 'Monica Bellucci') at different exposure durations. Results indicated that the O₃-induced stimulation after short-term exposure (35 days after the beginning of O₃ exposure) was significant only for sesquiterpene emissions from flowers, while long-term O₃ exposure (90 days after the beginning of O₃ exposure) significantly decreased both foliar and floral monoterpene and sesquiterpene emissions. In addition, the observed decline of emissions under long-term O₃ exposure resulted from the limitation of synthase substrates, and the responses of emissions and substrates varied among varieties, with the greatest variation in the O₃-sensitive variety. These findings provide important insights on plant isoprenoid emissions and species selection for landscaping, especially in areas with high O₃ concentration.

Variability and sources of non-methane hydrocarbons at a Mediterranean urban atmosphere: The role of biomass burning and traffic emissions

Levels and sources of non-Methane Hydrocarbons (NMHCs) were investigated at the urban background Thissio station, close to the historical center of Athens (Greece) from March 2016 to February 2017 (12 months), by means of an automated GC-FID. Alkanes dominated over aromatics and alkenes, with hourly mean levels ranging from detection limit up to 60 μg m^-3 for i-pentane and 90 μg m^-3 for toluene. Higher levels were recorded in the cold period relative to the warmer one. In addition, NMHCs seasonal diurnal cycles were characterized by a bimodal pattern, following the trend of tracers of anthropogenic sources. The Positive Matrix Factorization (PMF) was used for the allocation of NMHC to their sources. Five factors were identified and quantified, with traffic-related sources being the main one contributing up to 60% to total NMHCs, while biomass burning contributes up to 19%. A supplementary PMF assimilation was applied on a seasonal basis further including α-pinene, C6-C16 alkanes and aromatics. This PMF resulted to a seven-factor solution that allowed the examination of two additional sources, in addition to five already identified, highlighting the main contribution of anthropogenic sources (70%) to α-pinene.

Ambient volatile organic compounds in tropical environments: Potential sources, composition and impacts - A review

Volatile organic compounds (VOCs) are widely recognized to affect the environment and human health. This review provides a comprehensive presentation of the types and levels of VOCs, their sources and potential effects on human health and the environment based on past and current observations made at tropical sites. Isoprene was found to be the dominant biogenic VOC in the tropics. Tropical broad leaf evergreen trees are the main emitters of isoprene, making up more than 70% of the total emissions. The VOCs found in the tropical remote marine atmosphere included isoprene (>100 ppt), dimethyl sulfide (≤100 ppt) and halocarbons, i.e. bromoform (≤8.4 ppt), dibromomethane (≤2.7 ppt) and dibromochloromethane (≤1.6 ppt). VOCs such as benzene, toluene, ethylbenzene and xylene (BTEX) are the most monitored anthropogenic VOCs and are present mainly due to motor vehicles emissions. Additionally, biomass burning contributes to anthropogenic VOCs, especially high molecular weight VOCs, e.g. methanol and acetonitrile. The relative contributions of VOC species to ozone are determined through the level of the Ozone Formation Potential (OFP) of different species. Emissions of VOCs (e.g. very short-lived halogenated gases) in the tropics are capable of contributing to stratospheric ozone depletion. BTEX has been identified as the main types of VOCs that are associated with the cancer risk in urban areas in tropical regions. Finally, future studies related to VOCs in the tropics and their associated health risks are needed to address these concerns.

Contrasting responses of major and minor volatile compounds to warming and gall-infestation in the Arctic willow Salix myrsinites

Climate change is altering high-latitude ecosystems in multiple facets, including increased insect herbivory pressure and enhanced emissions of volatile organic compounds (VOC) from vegetation. Yet, joint impacts of climatic drivers and insect herbivory on VOC emissions from the Arctic remain largely unknown. We examined how one-month warming by open-top plastic tents, yielding a 3-4 °C air temperature increase, and the natural presence of gall-forming eriophyoid mites, Aculus tetanothrix, individually and in combination, affect VOC emissions from whortle leaved willow, Salix myrsinites, at two elevations in an Arctic heath tundra of Abisko, Northern Sweden. We measured VOC emissions three times in the peak growing season (July) from intact and gall-infested branches using an enclosure technique and gas chromatography-mass spectrometry, and leaf chemical composition using near-infrared reflectance spectroscopy (NIRS). Isoprene accounted for 91% of the VOCs emitted by S. myrsinites. Isoprene emission rates tended to be higher at the high than low elevation during the measurement periods (42 μg g^-1 DW h^-1 vs. 23 μg g^-1 DW h^-1) even when temperature differences were accounted for. Experimental warming increased isoprene emissions by approximately 54%, but decreased emissions of some minor compound groups, such as green leaf volatiles (GLV) and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). In contrast, gall-infestation did not affect isoprene emissions but stimulated emissions of DMNT, sesquiterpenes and GLVs, particularly under ambient conditions at the low elevation. The NIRS-based chemical composition of the leaves varied between the two elevations and was affected by warming and gall-infestation. Our study suggests that under elevated temperatures, S. myrsinites increases emissions of isoprene, a highly effective compound for protection against oxidative stress, while an infestation by A. tetanothrix mites induces emissions of herbivore enemy attractants like DMNT, sesquiterpenes and GLVs. Under both conditions, warming effects on isoprene remain but mite effects on DMNT, sesquiterpenes and GLVs diminish.

Synergistic effects of insect herbivory and changing climate on plant volatile emissions in the subarctic tundra

Climate change increases the insect abundance, especially in Arctic ecosystems. Insect herbivory also significantly increases plant emissions of volatile organic compounds (VOCs), which are highly reactive in the atmosphere and play a crucial role in atmospheric chemistry and physics. However, it is unclear how the effects of insect herbivory on VOC emissions interact with climatic changes, such as warming and increased cloudiness. We assessed how experimental manipulations of temperature and light availability in subarctic tundra, that had been maintained for 30 years at the time of the measurements, affect the VOC emissions from a widespread dwarf birch (Betula nana) when subjected to herbivory by local geometrid moth larvae, the autumnal moth (Epirrita autumnata) and the winter moth (Operophtera brumata). Warming and insect herbivory on B. nana stimulated VOC emission rates and altered the VOC blend. The herbivory-induced increase in sesquiterpene and homoterpene emissions were climate-treatment-dependent. Many herbivory-associated VOCs were more strongly induced in the shading treatment than in other treatments. We showed generally enhanced tundra VOC emissions upon insect herbivory and synergistic effects on the emissions of some VOC groups in a changing climate, which can have positive feedbacks on cloud formation. Furthermore, the acclimation of plants to long-term climate treatments affects VOC emissions and strongly interacts with plant responses to herbivory. Such acclimation complicates predictions of how climate change, together with interacting biotic stresses, affects VOC emissions in the high latitudes.