Competitive Uptake of Dimethylamine and Trimethylamine against Ammonia on Acidic Particles in Marine Atmospheres

Analysis, biology and significance of dimethylamine, trimethylamine and trimethylamine N-oxide in humans and in the marine ecosystem

Dimethylamine (DMA) and its relatives including trimethylamine (TMA) and trimethylamine N-oxide (TMAO) are widely distributed in nature including humans and the marine ecosystem. This article gives an overview of the origin, occurrence, metabolism and potential functions of dimethylamine in human life and of the DMA-TMA-TMAO axis in the marine ecosystem. In humans, a dimethylamine fraction of about 80-90 % is of endogenous origin. The remaining 10-20 % is of exogenous origin, notably of foods and especially of certain fish and seafood. Several different analytical methods are available for the quantitative determination of dimethylamine, trimethylamine and trimethylamine N-oxide in biological samples including human urine and fish. Frequently used methods include GC-FID, GC-ECD, GC-MS and more recently LC-MS/MS. A widely used GC-MS method of dimethylamine in human urine includes its extractive derivatization with pentafluorobenzoyl chloride. The dimethylamine concentration in plasma and serum is of the oder of 3 μM in healthy humans and several times higher in humans suffering from chronic kidney diseases. The dimethylamine concentration in human urine may range between 100 μM and 1500 μM, corresponding to mean creatinine-corrected excretion rates of 10 to 80 μmol dimethylamine/mmol creatinine in adults and up to 400 μmol dimethylamine/mmol creatinine in children and adolescents. GC-MS methods have contributed greatly to a better understanding of the biology of dimethylamine in health and disease. In humans, up to 90 % of urinary dimethylamine is considered a measure of its endogenous synthesis from post-translational dimethylation of arginine residues in proteins. This abundant post-translational modification leads to asymmetrically dimethylated arginine proteins, which, upon regular proteolysis, generate asymmetrical dimethylarginine (ADMA) that is finally hydrolyzed to and L-citrulline and dimethylamine, which is then readily excreted in the urine. In fishery, dimethylamine and trimethylamine are discussed as indicators of freshness due to their enhanced production of microbiomal activity. High amounts of dimethylamine are found in canned fish. Dimethylamine is considered the precursor of the cancerogenic N-nitroso-dimethylamine. Other non-volatile amines such as histamine and agmatine seem to be better suitable as fish freshness indicators. High contents of the order of several mmol trimethylamine N-oxide per kg tissue are found in fish in dependence on the habitat depth. It is assumed that trimethylamine N-oxide act as osmolytic and piezolytic agent. The significance of trimethylamine N-oxide in human health and disease is elusive.

Quantification of dimethylamine in low concentration particulate matter by reducing the concentration of 9-fluorenylmethyl chloroformate

This study presents a refined method that uses liquid chromatography with a fluorescence detector (LC-FD) to quantify trace amounts of dimethylamine in particulate matter (PM). This method was optimized to prioritize simplicity, cost-effectiveness and practicality. To ensure accurate and reliable analysis, strict protocols and procedures were followed to minimize cross-contamination. Separate workspaces were designated for preparing control blanks and sample treatments in one area and standard solutions in another, thus mitigating the risk of cross-contamination. An evaluation was conducted on different concentrations of 9-fluorenylmethyl chloroformate to derivatize dimethylamine. The results showed that a concentration of 3 μg mL-1 was effective in derivatizing dimethylamine concentrations up to 300 ng mL-1. Increasing the concentration of the derivatization reagent from 2.9 to 7.3 μg mL-1 resulted in slightly elevated dimethylamine levels in blank measurements. Also, during the preparation of standards at low concentrations, high analytical coefficients of variation were observed. This highlights the importance of checking for potential sources of contamination. Method precision and quantification limits were evaluated through blank analysis, yielding values of approximately 20% and 20 ng mL-1, respectively, consistent with chromatographic determination for environmental analysis. The suitability of the method for environmental analysis was demonstrated by analyzing eight PM2.5 samples. The concentrations of methylamine and dimethylamine were found to range from 0.8 to 3 ng m-3 and 1.4 to 7.1 ng m-3, respectively, in accordance with the literature. Comparison with concurrent carbonyl measurements revealed similar concentration profiles. Both types of analyses can be performed using affordable methodologies that involve prior derivatization using a reduced concentration of the derivatization reagent.

Heterogenous Chemistry of I2O3 as a Critical Step in Iodine Cycling

Global iodine emissions have been increasing rapidly in recent decades, further influencing the Earth's climate and human health. However, our incomplete understanding of the iodine chemical cycle, especially the fate of higher iodine oxides, introduces substantial uncertainties into atmospheric modeling. I2O3 was previously deemed a "dead end" in iodine chemistry; however, we provide atomic-level evidence that I2O3 can undergo rapid air-water or air-ice interfacial reactions within several picoseconds; these reactions are facilitated by prevalent chemicals on seawater such as amines and halide ions, to produce photolabile reactive iodine species such as HOI and IX (X = I, Br, and Cl). The heterogeneous chemistry of I2O3 leads to the rapid formation of iodate ions (IO3-), which is the predominant soluble iodine and its concentration cannot be well explained by current chemistry. These new loss pathways for atmospheric I2O3 can further explain its absence in field observations and its presence in laboratory experiments; furthermore, these pathways represent a heterogeneous recycling mechanism that can activate the release of reactive iodine from oceans, polar ice/snowpack, or aerosols. Rapid reactive adsorption of I2O3 can also promote the growth of marine aerosols. These findings provide novel insights into iodine geochemical cycling.

Characteristics of aerosol aminiums over a coastal city in North China: Insights from the divergent impacts of marine and terrestrial influences

Aminium ions, as crucial alkaline components within fine atmospheric particles, have a notable influence on new particle formation and haze occurrence. Their concentrations within coastal atmosphere depict considerable variation due to the interplay of distinctive marine and terrestrial sources, further complicated by dynamic meteorological conditions. This study conducted a comprehensive examination of aminiums ions concentrations, with a particular focus on methylaminium (MMAH+), dimethylaminium (DMAH+), trimethylaminium (TMAH+), and triethylaminium (TEAH+) within PM2.5, over varying seasons (summer, autumn, and winter of 2019 and summer of 2021), at an urban site in the coastal megacity of Qingdao, Northern China. The investigations revealed that the total concentration of particulate aminium ions (∑Aminium) was 21.6 ± 23.6 ng/m3, exhibiting higher values in the autumn and winter compared to the two summer periods. Considering diurnal variations during autumn and winter, concentrations of particulate aminium ions (excluding TEAH+) exhibited a slight increase during the day compared to night, with a notable peak during the morning hours. However, it was not the case for TEAH+, which was argued to be readily oxidized by ambient oxidants in the afternoon. Additionally, the ∑Aminium within the summer demonstrated markedly elevated levels during the day compared to night, potentially attributed to daytime sea fog associated with sea-land breeze interactions. Positive matrix factorization results indicate terrestrial anthropogenic emissions, including vehicle emission mixed with road dust and primary pollution, as the primary sources of MMAH+ and DMAH+. Conversely, TMAH+ was predominantly emitted from agricultural and marine sources. With the dominance of sea breeze in summer, TMAH+ was identified as a primary marine emission correlated with sea salt, while MMAH+, DMAH+, and TEAH+ were postulated to undergo secondary formation. Furthermore, a notable inverse correlation was observed between TMAH+ and methanesulfonate in PM2.5, consistent with dynamic emissions of sulfur-content and nitrogen-content gases reported in the literature.

Contribution of marine biological emissions to gaseous methylamines in the atmosphere: An emission inventory based on multi-source data sets

Methylamines are a class of highly reactive organic alkaline gases in the atmosphere. At present, the gridded emission inventories of amines used in the atmospheric numerical model is mostly based on the amine/ammonia ratio method and do not consider the air-sea exchange of methylamines, which oversimplifies the emission scenario. Marine biological emissions (MBE), an important source of methylamines, has been insufficiently investigated. These shortcomings in the inventories can limit the simulation of amines by numerical models in the context of compound pollution in China. To acquire a more complete gridded inventory of amines (monomethylamine (MMA), dimethylamines (DMA), and trimethylamines (TMA)), we established a more reasonable MBE inventory of amines by using multi-source data sets (Sea Surface Temperature (SST), Chlorophyll-a (Chla), Sea Surface Salinity (SSS), NH3 column concentration (NH3), and Wind Speed (WS)), and merged it with the anthropogenic emissions (AE) inventory (by adopting the amine/ammonia ratio method and the Multi-resolution Emission Inventory for China (MEIC)). The new methodology can reveal the air-sea exchange fluxes and direction of different amines. Oceans can act as a sink for DMA and source for TMA while it can be either a source or sink for MMA. The concentration of amines above the coastal area increased significantly when the MBE was merged to the AE inventory. TMA and MMA showed significant increases, TMA increased by 43,917.0 %, and 804.0 %, in July 2015 and December 2019, respectively; while MMA increased by 2635.4 % and 0.37 % during the same periods; however, only slight changes were observed in the DMA concentration (-3.9 % in July 2015, and 1.1 % in December 2019). WS, Chla, and the total dissolved concentration of amines ([C+(s)tot]) were found to be the dominant factors affecting MBE fluxes. In addition, the emission fluxes and spatial distribution of AE, and wet deposition also affect the simulation of amines concentration.

The determination of volatile amines in aquatic marine systems: A review

This review provides a critical assessment of knowledge regarding the determination of volatile, low molecular weight amines, and particularly methylamines, in marine aquatic; systems. It provides context for the motivation to determine methylamines in the marine aquatic environment and the analytical challenges associated with their measurement.While sensitive analytical methods have been reported in recent decades, they have not been adopted by the oceanographic community to investigate methylamines' biogeochemistry and advance understanding of these analytes to the degree achieved for other marine volatiles. Gas chromatography, high performance liquid chromatography, ion chromatography and infusion-mass spectrometry techniques are discussed and critically determined, alongside offline and online preconcentration steps. Interest in the marine occurrence and cycling of methylamines has increased within the last 10-15 years, due to their potential role in climate regulation. As such, the need for robust, reproducible methods to elucidate biogeochemical cycles for nitrogen and populate marine models is apparent. Recommendations are made as to what equipment would be most suitable for future research in this area.

Potential Risk of NH3 Slip Arisen from Catalytic Inactive Site in Selective Catalytic Reduction of NOx with Metal-Free Carbon Catalysts

Ammonia emissions from industrial processes have rapidly increased in the past years. Recent advances have used carbon-based selective catalytic reduction (SCR) technology combined with a reaction-regeneration process to reduce NO_x from sintering flue gas, while NH₃ slip is seldom accounted for in this process. This study demonstrates that although the electrophilic carboxyl groups (-COOH) on metal-free carbon catalysts exhibit strong adsorption toward NH₃, they do not participate in the SCR reaction. As a result of the competitive adsorption of NH₃ in the reaction step, these catalytic inactive carboxyl groups not only prolong the time to the SCR steady state, but also result in the potential risk of NH₃ slip. A linear relationship with the equimolar ratio between carboxyl groups and slipped NH₃ was established in the regeneration steps. The slip of NH₃ could be alleviated by the decomposition of carboxyl groups, and special attention should be paid to the presence of inactive sites with strong NH₃ adsorption on industrial-employed carbon catalysts. In addition to advancing the understanding of the NH₃-SCR mechanism, this work also provides valuable opportunities for the control of ammonia emissions from industrial processes.