A recent study published in Analytical Chemistry demonstrates the molecular characterization of Organophosphorus compounds in an ambient organic aerosol altered by wildfire smoke. A significant source of phosphorus for surface water is biomass-burning organic aerosols. Even a slight imbalance in the phosphorus flux significantly impacts water quality by causing algal blooms, eutrophication, and oxygen depletion.
The researchers investigated the molecular makeup of an ambient BBOA sample transformed by wildfire smoke in the Pacific Northwest using Fourier transform-ion cyclotron resonance mass spectrometry, which has extremely high mass accuracy, resolving power, and sensitivity.
Effect of Biomass-Burning Organic Aerosol on the Environment
Atmospheric aerosols are planetary variables controlled globally to reduce human impact on the climate and environment. Aerosols are key in maintaining the biogeochemical cycle, air quality, radiative balance, and human health. Large-scale biomass-burning events, such as wildfire smoke significantly influence the total organic mass loading in the atmosphere. The molecular makeup of biomass-burning organic aerosols is one of the determining variables that influence the climate and the biotic and abiotic entities.
Importance of Phosphorus Containing Atmospheric Aerosols
Phosphorus-containing atmospheric aerosols are a substantial source of phosphorus for surface waters in both wet and dry atmospheric deposition. Phosphorus is an essential nutrient that can restrict nitrogen's primary production and fixation despite its minor and diffused influx into surface water via aerosols. It also changes aquatic ecosystems' biogeochemical balance, causing algal blooms, eutrophication, and oxygen (O) depletion.
Predicted Sources of Phosphorus
It is predicted that a range of sources, including coal combustion, primary biological and marine aerosols, soil and desert dust, biomass burning, and agricultural fertilizers, emit a total of 3.7 tons of phosphorus annually. It is projected that 20% of this phosphorus comes from natural wildfires. Only a small portion of the directly released phosphorus during large-scale biomass burning events is water soluble.
Insoluble organic phosphorus is transformed into soluble forms by aging caused by the uptake of oxidants during long-distance transport, making it a significant source of bioavailable phosphorus for surface waters.
Ultrahigh-Resolution Mass Spectrometry Analysis of Organic Aerosols
Burning biomass emits phosphorus in significant amounts. Phosphorus significantly impacts aquatic ecosystems. Only a few studies include phosphorus, carbon, oxygen, and nitrogen in ultrahigh-resolution mass spectrometry analysis of organic aerosols. Phosphorus-containing equations are also eliminated from analysis because of their quantitative insignificance compared to other molecular groups.
Characterization of organophosphorus compounds in mass spectrometry research of aerosols is necessary because their molecular-level characterization can reveal information about their molecular weight, aromaticity, and elemental ratios.
Limitations of Mass Spectrometric Analysis for Characterization of Organophosphorus Compounds
The ineffective ionization of the phosphate functional group particularly when organophosphates are present in relatively minute amounts is a significant limitation of mass spectrometric characterization of organophosphorus compounds in complex mixtures.
Studies focusing on dissolved organic phosphorus (DOP) in natural aquatic organic matter advise selective isolation and concentration of DOP before mass spectrometry analysis due to the small sample sizes for atmospheric aerosol.
Utilization of Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry for Characterization of Organophosphorus Compounds
Fourier transform-ion cyclotron resonance mass spectrometry highly oxygenates the phosphorus-containing species in solid-phase extracted dew water. These species originate from phospholipids, DNA, and reactions of metabolites exuded on the surface of leaves.
Ijaz et al. revealed the molecular composition of organic aerosols altered by wildfire smokes with the help of electrospray ionization paired with Fourier transform-ion cyclotron resonance mass spectrometry. A mass spectrometer's highest magnetic field strength provided high sensitivity, acquisition speed, resolving power (RP), mass accuracy, and dynamic range. The Pacific Northwest National Laboratory (PNNL) designed the Fourier transform-ion cyclotron resonance mass spectrometry for this application.
The researchers focused on the characterization of organophosphorus compounds because they have been quantitively reported in wildfire smoke for a long time but have never been characterized molecularly.
Phosphorus substances were found in a large matrix of 9841 non-phosphorus formulas from the chemical groups CHO, CHNO, and CHOS. The CHOP and CHNOP groups significantly impact the environment despite making up only 6.57% of all given formulae because of their propensity to increase the nutrient load of aquatic environments. To fully comprehend their ramifications, they must be included in the comprehensive investigation of organic aerosols impacted by wildfire smoke.
In this study, the researchers described the first molecular-level characterization of organophosphorus compounds using ultrahigh-resolution mass spectrometry. Organophosphorus compounds containing carbon, oxygen, and phosphorus constituents, with and without nitrogen, were investigated in atmospheric organic aerosols originating from wildfire smoke.
The findings revealed that organophosphorus compounds in burning-mass organic aerosols can be detected and identified using Fourier transform-ion cyclotron resonance mass spectrometry without needing pre-treatment or selective concentration from the non-phosphorous organic matrix. Exploring every option to better understand atmospheric aerosols and their interactions with ecosystems is essential given the predicted rise in the frequency of wildfires and other large-scale biomass-burning episodes around the world in the coming years.
Ijaz, A., Kew, W., China, S., Schum, S. K., & Mazzoleni, L. R. (2022) Molecular Characterization of Organophosphorus Compounds in Wildfire Smoke Using 21-T Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry. Analytical Chemistry. https://pubs.acs.org/doi/10.1021/acs.analchem.2c00916