Characterization of Gaseous and Particulate Phase Polycyclic Aromatic Hydrocarbons Emitted During Preharvest Burning of Sugar Cane in Different Regions of Kwa‐Zulu Natal, South Africa

Abstract

Biomass burning is a significant anthropogenic source of air pollution, including the preharvest burning of sugar cane. These burn events result in atmospheric emissions, including semivolatile organic compounds, that may have adverse impacts on air quality and human health on a local, regional, and even a global scale. Gaseous and particulate polycyclic aromatic hydrocarbon (PAH) emissions from various sugar cane burn events in the province of Kwa‐Zulu Natal in South Africa were simultaneously sampled using a portable denuder sampling technology, consisting of a quartz fiber filter sandwiched between two polydimethylsiloxane multichannel traps. Total gas and particle phase PAH concentrations ranged from 0.05 to 9.85 µg m–3 per individual burn event, and nine PAHs were quantified. Over 85% of all PAHs were found to exist in the gas phase, with smaller two‐ and three‐ring PAHs, primarily naphthalene, 1‐methyl naphthalene, and acenaphthylene, being the most dominant and causing the majority of variance between the burn sites. The PAH profiles differed between the different burn events at different sites, emphasizing the significant influence that the crop variety, prevailing weather conditions, and geographical location has on the type and number of pollutants emitted. The potential carcinogenicity of the PAH exposure was estimated based on toxic equivalency factors that showed varying risk potentials per burn event, with the highest value of 5.97 ng m–3. Environ Toxicol Chem 2023;42:778–792. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Chemical Fingerprinting of Biomass Burning Organic Aerosols from Sugar Cane Combustion: Complementary Findings from Field and Laboratory Studies

“…Furthermore, a mean concentration for total gas phase PAHs of 0.76 μg m –3 was found in the field samples. In comparison to our prior study by Geldenhuys et al, where the mean total gas phase concentration of PAHs in the field experiments using a different sampling method with small polydimethylsiloxane portable denuder devices was reported at 3.4 μg m –3 , the here presented analysis detected a lower total PAH content. Since this previous study revealed that 90% of the total PAHs were present in the gas phase rather than the particle phase, it is crucial to consider both the gas and particle phases to accurately account for gas–particle transformations occurring in the atmosphere.…”

“…Moreover, previous results by Geldenhuys et al suggest that, in addition to differences in biomass composition and crop characteristics, the influence of the prevailing weather and combustion conditions on biomass combustion emissions and their gas–particle partitioning also play an important role in the emission profiles. In this respect, previous results showed clear differences in PAH emission profiles from one sugar cane burning event to another …”

“…A Venn diagram representation of the overlap of chemical compounds derived from these two different evaluation approaches can be found in Figure S5. The compounds with the highest fold changes (>1000) were previously discussed methoxyphenols, such as syringic acid (40), acetosyringone (48), and 2,6-dimethoxyphenol (7). Compounds 38,34,and 46 belong to the previously discussed compound classes of furan derivatives and (methoxy)benzenes.…”

“…In this respect, previous results showed clear differences in PAH emission profiles from one sugar cane burning event to another. 7 The most prominent compound detected in the field samples was levoglucosan, which is derived from the thermal decomposition of cellulose and serves as a reliable marker for biomass burning. Interestingly, it was not detected in the laboratory samples, in which its dehydrated form levoglucosenone dominates instead.…”

“…By combining observations from controlled biomass burning experiments in the laboratory with those from the field campaign, we aim to validate findings from laboratory studies and gain a more comprehensive understanding of biomass burning emissions under realistic environmental conditions. 7 and are summarized in Table S1. Three burns were conducted on the north coast of Kwa-Zulu Natal, a coastal region with a warm and temperate climate.…”