Emission of volatile organic compounds from landfill working surfaces: Formation potential of ozone and secondary organic aerosols

Odor nuisance, environmental impact and health risk of priority-controlled VOCs generated from three decentralized aerobic biological modes in treating rural perishable waste

Utilization of perishable waste has emerged as the pivotal factor in enhancing the quality and efficiency of garbage classification in rural regions of China. Nevertheless, the operation of small-scale decentralized aerobic biological treatment facilities in rural areas will inevitably result in the emission of malodorous volatile organic compounds (VOCs). In this study, VOCs emission characteristics of three typical decentralized facilities for the treatment of perishable waste in rural areas were investigated using cold trap enrichment combined with gas chromatography and mass spectrometry to elucidate the characteristics and potential effects on environment and human health. The concentration range of different points in the mechanical composting (MC) treatment mode is from 43.555 to 4154.281 (mean value, 947.292) µg/m3, in the solar-assisted composting (SAC) it is from 99.050 to 2064.308 (636.170) µg/m3, and in the bioconversion by black soldier fly larvae (BBSF) it is 93.712 to 718.644 (283.444) µg/m3. Odor nuisance analysis showed that oxygenated compounds and aromatic compounds were the main odoriferous VOCs. Among all detected VOCs, o-xylene, toluene, and acrolein have the highest ozone formation potential (OFP). Toluene, ethyl benzene, and xylene are the VOCs with secondary organic aerosol generation potential (SOAP). Health risk analysis revealed that six VOCs collectively represent a potential carcinogenic risk, while acrolein exhibits a non-carcinogenic risk. In light of the odor nuisance, environmental impact, and potential health risk, the priority-controlled VOCs identified in decentralized aerobic treatment modes of rural perishable waste were acrolein, benzyl chloride, ethyl acetate, etc. The findings of this research can serve as a valuable reference for the selection of proper strategies in the precise control of VOCs.

Understanding the effect of seasonal variability of VOCs and NOx on the ozone budget and its photochemical processing over a rural atmosphere

Ozone (O3) in the troposphere is critically important because it serves as a significant oxidant, playing a vital role in atmospheric chemistry and influencing various environmental and health impacts. Several factors impact O3 formation which include precursor concentrations, meteorological conditions, and transport. In the present study, a rural observational site located in Gadanki (13.5°N, 79.2°E), India, has been identified as a NOx-limited regime, which is a common photochemical processing regime for rural atmospheres, using the O3 production regime indicator (Θ) value. The Θ value approached 0.01 during the daytime in all seasons, indicating a different O3 production regime compared to urban atmospheres, which are generally Volatile Organic Compounds (VOC)-limited. Subsequently, efforts have been made to understand the role of VOC and NOx concentrations, along with meteorological conditions and transport, in quantifying the seasonal variation of O3 formation in terms of VOC/NOx sensitivity at the observational site using the photochemical model O3 Isopleth Plotting Package (OZIPR). The VOC cross-over points obtained from the O3 isopleth diagrams using the OZIPR model have shown a significant correlation with O3 Formation Potential (OFP) and Propylene Equivalent Concentration (PEC) values, supporting the variability in O3 formation in most of the seasons at the observational site. Additionally, the highest O3 concentration measured in the summer season is also well reproduced by the VOC cross-over correlations with the OFP and PEC values. Biomass burning VOCs have been found to be the highest contributors to the O3 formation due to their higher emission in the summer season and higher contribution to both OFP and PEC.

Detecting and sourcing GHGs and atmospheric trace gases in a municipal waste treatment plant using coupled chemistry and isotope compositions

Landfill operations and waste processing facilities are important and highly heterogeneous sources of both greenhouse gases (GHGs) and non-GHG air pollutants in the atmosphere. This arises the need for detailed apportionment of waste sources in order to locate and subsequently reduce emissions from landfills. Here, a time series of in situ measurements of atmospheric trace gases and spatial allocation of specific emission source types under different processing phases and environmental conditions were conducted in and in the surroundings of a Municipal Solid Waste Treatment Plant (MSWTP) in south-western Poland. Results revealed that several individual GHG sources dominated across the waste processing facility and that GHGs concentrations displayed spatial seasonality. An increase in the ground-level CH4 concentrations, from ∼ 30.3 to 56.3 ppmv, was observed close (∼5 - 10 m) to the major emission sources within the MSWTP. While hotspot areas generally yielded elevated CH4 concentrations near the soil surface, these were relatively low (2.4 to 8.9 ppmv) along the facility's fence line. The study of the corresponding δ13C delineated the extent of dispersion plumes downwind emission hotspots, characterized by a 13C depletion (around 4.0 ‰) in the atmospheric CH4 and CO2. For CH4, emissions were isotopically discriminated between the extraction wells at active quarters/cells (δ13C = -58.3 ± 1.1 ‰) and biogas produced in the biological waste treatment installation (δ13C = -62.7 ± 0.7 ‰). Most of the trace compounds (non-methane hydrocarbons, halocarbons, oxygen-bearing organic gases, ketones, nitrogenous and sulphurous gases, and other admixture compounds) detected at the ground surface were linked to the CH4- and CO2-rich spots. Despite the relatively high variability in the concentrations of organic and inorganic compounds observed at the MSWTP active zones, our results suggest that they do not have a meaningful impact on the surrounding air quality.

Exhaust and evaporative volatile organic compounds emissions from vehicles fueled with ethanol-blended-gasoline

By 2020, China has implemented the use of 10% ethanol-blended-gasoline (E10), which is expected to notably impact vehicular volatile organic compounds (VOCs) emissions. The adoption of E10 reduced certain emissions but raised concerns with about more reactive oxygenated volatile organic compounds (OVOCs). This study aimed to evaluate the impact of E10 on the total VOCs emissions from both exhaust and evaporative emissions by conducting tests on the CHINA V (or CHINA VI) light-duty gasoline vehicles (LDGVs) using 0% ethanol blended gasoline (E0) and E10. E10 reduces VOCs emissions in the exhaust, and reduces the ozone and secondary organic aerosol generation potential of VOCs in the exhaust, as evidenced by the lower emission factors (EFs), ozone formation potentials (OFPs) and secondary organic aerosol formation potential (SOAFPs) in the CHINA V LDGVs. Evaporative emissions showed differences in emitted VOCs, with lower EFs, OFPs and SOAFPs for the CHINA V LDGVs fueled with E10. The CHINA VI LDGVs also exhibited reduced EFs, OFPs and SOAFPs. These findings highlight the environmental benefits of E10 in the CHINA VI-compliant LDGVs; however, the effectiveness of the earlier CHINA V standard vehicles requires further evaluation.

Association between Ambient Volatile Organic Compounds Exposome and Emergency Hospital Admissions for Cardiovascular Disease

The limited research on volatile organic compounds (VOCs) has not taken into account the interactions between constituents. We used the weighted quantile sum (WQS) model and generalized linear model (GLM) to quantify the joint effects of ambient VOCs exposome and identify the substances that play key roles. For a 0 day lag, a quartile increase of WQS index for n-alkanes, iso/anti-alkanes, aromatic, halogenated aromatic hydrocarbons, halogenated saturated chain hydrocarbons, and halogenated unsaturated chain hydrocarbons were associated with 1.09% (95% CI: 0.13, 2.06%), 0.98% (95% CI: 0.22, 1.74%), 0.92% (95% CI: 0.14, 1.69%), 1.03% (95% CI: 0.14, 1.93%), 1.69% (95% CI: 0.48, 2.91%), and 1.85% (95% CI: 0.93, 2.79%) increase in cardiovascular disease (CVD) emergency hospital admissions, respectively. Independent effects of key substances on CVD-related emergency hospital admissions were also reported. In particular, an interquartile range increase in 1,1,1-trichloroethane, methylene chloride, styrene, and methylcyclohexane is associated with a greater risk of CVD-associated emergency hospital admissions [3.30% (95% CI: 1.93, 4.69%), 3.84% (95% CI: 1.21, 6.53%), 5.62% (95% CI: 1.35, 10.06%), 8.68% (95% CI: 3.74, 13.86%), respectively]. We found that even if ambient VOCs are present at a considerably low concentration, they can cause cardiovascular damage. This should prompt governments to establish and improve concentration standards for VOCs and their sources. At the same time, policies should be introduced to limit VOCs emission to protect public health.

Age evolution of secondary organic aerosol: Impacts of regional transport and aerosol volatility

In this study, a revised CMAQ model incorporating source and temporal apportioning functions has been used to analyze the aging characteristics of SOA in East Asia. The results show that in the aerosol phase, the fraction of the non-volatile components typically fluctuates around 75 %-95 %, and aromatic hydrocarbon precursors contribute significantly to SOA, accounting for 45.6 %-72.7 % in winter and 29.1 %-52.7 % in summer. Transport due to meteorological conditions does not affect the SOA volatility profile in the cities, while regional source composition has been found to be important for the characterization of the properties of SOA in cities. When the SOA regional composition type is a multi-region-imported-dominated type (MRT), its age composition type tends to be an old-age-SOA-dominated type (OAT) (>48 h). Additionally, transport also causes fluctuations in the range of hourly SOA with atmospheric age of 96 h or higher. The SOAs normally transport through seasonal monsoon and could migrate longer in winter (700-1500 km in January) than in other seasons (250-900 km in April; 500-1200 km in July; 300-1000 km in October). Additionally, in winter, non-volatile SOA generally has a longer transport distance (700-1600 km) than semi- and low-volatile SOA (300-1300 km and 600-1500 km). Furthermore, during the transport process, geographical barriers have negligible impact on SOA in the 48+ hour age group.