关键词: 有机胺, NH₄⁺, 民用燃煤燃烧, 污染物排放, Monte Carlo模拟

Abstract:

Coal combustion is widely recognized as a major anthropogenic source of atmospheric reduced nitrogen compounds, particularly ammonium (NH₄⁺) and organic amines such as methylamine (MMA), dimethylamine (DMA), and ethylamine (EA). These nitrogenous species play critical roles in atmospheric chemistry: NH₄⁺ is a key constituent of secondary inorganic aerosols, whereas organic amines act as precursors to secondary organic aerosols (SOAs) through reactions with acidic gases and atmospheric oxidants to form amides. Their transformation contributes significantly to the formation of fine particulate matter (PM_2.5), exacerbating air pollution and posing considerable health risks, including respiratory inflammation and potential carcinogenicity via nitrosamine formation. Despite their environmental significance, the emission characteristics, spatiotemporal distributions, and long-term trends of NH₄⁺ and organic amines from residential coal combustion remain inadequately understood, particularly in rural and remote regions of China, where solid fuels continue to dominate household energy use. High-resolution nationwide emission inventories are scarce. To fill this knowledge gap, this study developed a comprehensive emission inventory of particulate NH₄⁺ and organic amines from residential coal combustion in China for 2014-2019. Emissions were estimated using provincial-level residential coal consumption data from the PKU-FUEL database, in conjunction with emission factors synthesized from recent literature. A Monte Carlo simulation (10000 iterations), assuming log-normal distributions, was conducted to quantify the uncertainties associated with fuel usage and emission factors. Furthermore, an autoregressive integrated moving average (ARIMA) model was applied to project emissions and emission densities for 2020-2030 based on historical trends in rural population and coal consumption. The results showed that northeastern and northwestern China were hotspots for NH₄⁺ and organic amine emissions, driven by prolonged winter heating needs, limited access to clean fuels, and persistent use of bulk coal and traditional stoves. In contrast, economically developed eastern provinces, such as Shanghai and Zhejiang, exhibited substantially lower emissions owing to higher rural incomes and the widespread adoption of cleaner energy sources, including electricity and natural gas. In 2019, the national emissions of organic amines and NH₄⁺ were estimated to be 6.73×10³ and 1.19×10³ t, respectively, which is a 13% decrease from the 2014 levels (7.78×10³ and 1.36×10³ t). Among the organic amines, EA was the predominant species (3.23×10³ t), followed by MMA (2.07×10³ t) and DMA (1.43×10³ t), accounting for 47.9%, 30.9%, and 21.2% of the total organic amine emissions, respectively. Emission density analysis revealed significant regional disparities in emissions. In 2019, the national emission densities of organic amines and NH₄⁺ were 1.27 t per 10000 people and 2.24×10⁻¹ t per 10000 people, respectively. The northeastern region had the highest emission densities, with 4.59×10⁻¹ t per 10000 people for organic amines and 8.09×10⁻² t per 10000 people for NH₄⁺, while the southern region had the lowest, at only 0.23% and 0.21% of the northeastern values, respectively. Although Hebei Province ranked third in the total emissions of organic amines and NH₄⁺, its emission density was lower because of its large rural population size. In contrast, Ningxia, with lower total emissions, had an emission density 4.03 times higher than that of Hebei, reflecting a greater per-capita pollution burden Ningxia. The higher emission densities in the northwest are attributed to the heavy reliance on coal for winter heating, with 83% of heating areas using coal, compared to the significantly lower densities in the eastern coastal provinces, such as Shanghai and Zhejiang, where clean energy is more widely adopted. From 2014 to 2019, national emissions of organic amines and NH₄⁺ declined by 13%, largely due to the transition toward cleaner rural energy structures and a reduction in the rural population. For instance, emissions in central China dropped from 0.85×10³ t (organic amines) and 0.15×10³ t (NH₄⁺) to 0.33×10³ t and 0.06×10³ t, respectively. However, emissions in the northeastern and northwestern regions showed an increasing trend. Specifically, in the northeast, emissions of organic amines and NH₄⁺ grew by 1.67% and 1.56%, respectively, from 2014 to 2019, with emission densities rising to 4.6×10⁻¹ t per 10000 individuals and 8.09×10⁻² t per 10000 individuals. This trend is closely linked to increased coal consumption and changes in the energy structure in the northeast. ARIMA model projections indicate that by 2030, national emissions of organic amines will decrease to approximately 5.33×10³ t (MMA: 1.53×10³ t, DMA: 1.18×10³ t, EA: 2.62×10³ t), and NH₄⁺ emissions will decrease to 0.92×10³ t, reflecting a 21% reduction compared with 2019. Emission densities are also expected to decline, suggesting the positive impact of clean energy policies and rural-to-urban migration on emissions levels. However, emissions in northeastern China are projected to increase by 17.1%, with emission densities rising to 7.47×10⁻¹ t per 10000 people for organic amines and 1.33×10⁻¹ t per 10000 people for NH₄⁺, primarily because of the increased coal consumption. Regression analysis reveals a positive correlation between coal usage and per capita disposable income in the northeast, where the underdeveloped clean energy infrastructure and high cost of alternative energy continue to make coal the dominant energy source in the region. By 2030, emissions from northeastern and northwestern China are expected to account for 37.5% and 38.6% of the national totals for organic amines and NH₄⁺, respectively, highlighting these regions as key targets for future emission-reduction strategies. This study highlights the need for targeted emission reduction strategies, particularly in regions where clean energy adoption is lagging behind. These findings provide a scientific basis for future policy interventions aimed at mitigating emissions from residential coal combustion in rural areas of China.

Key words: organic amines, NH₄⁺, residential coal combustion, pollutant emissions, Monte Carlo simulation