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Amines affect particle formation, aerosol acidity, nitrogen cycle, and climate change. However, little is known about the temporal and spatial differences in the composition, source, and formation process of amines in fine particulate matter (PM2.5) in different regions of China. Seven amines (amine salts) were investigated in PM2.5 collected in the Yangtze River Delta (YRD, Shanghai and Nanjing), Pearl River Delta (PRD, Guangzhou), northern China (Xi'an and Haerbin), and background (Puding) areas in winter 2017–2018. Methylamine was the dominant amine species at the YRD, northern China, and background sites, while diethylamine dominated at the PRD site; moreover, the mass concentration and fraction of diethylamine were the lowest at the background site. These results could be attributed to changes in sources and atmospheric processes. Further, coal combustion and biomass burning were found to be important contributors of amines in northern cities in winter. The contribution of biomass and coal combustion to amines was weakened in other urban sites. In contrast, the amine abundance at the background site was largely controlled by biogenic sources. Acid‐base chemistry and displacement mechanism were tightly associated with the formation of amine salts at all sites. In particular, the atmospheric degradation of amines by hydroxyl radical (•OH) was significant at the Nanjing, Guangzhou, Xi'an, and Haerbin sites. The insignificant photochemical degradation of amines at the Shanghai and background sites can be explained by differentiated amine sources, meteorological conditions, and •OH levels. Overall, our findings deepen the understanding of the origins and atmospheric processes of amines. Plain Language Summary: Concentrations, compositions, potential sources, and major atmospheric processes of amines in winter PM2.5 in different regions of China were systematically investigated for the first time. The concentrations and compositions of amines in PM2.5 showed significant spatial differences, with the dominance of diethylamine at the Guangzhou site and the dominance of methylamine at other sites (Nanjing, Shanghai, Xi'an, Haerbin, and background sites). The influence of coal combustion associated with heating and industry was a typical feature that distinguishes the difference of amine sources between the coastal and northern areas. Moreover, the overall amine abundance at the background site was largely controlled by biogenic sources. Acid‐base chemistry and displacement mechanism were tightly associated with the formation of amine salts in PM2.5 at all sites. The atmospheric processes related to •OH exerted a significant impact on the removal of amines at the Nanjing, Guangzhou, Xi'an, and Haerbin sites. The insignificant photochemical degradation of amines in the Shanghai and background areas was associated with varied amine sources, meteorological conditions, and •OH levels. The overall results improve the current understanding on the temporal and spatial variations in the composition, source, and atmospheric process of amines in China. Key Points: Changes in the source led to large differences in the concentration and composition of amines in winter PM2.5 across regionsAcid‐base chemistry contributed significantly to the formation of amine salts in PM2.5 at all study sitesThe atmospheric degradation of amines by •OH was significant only at the Nanjing, Guangzhou, Xi'an, and Haerbin sites [ABSTRACT FROM AUTHOR]

Mist cannon trucks have been widely applied in megacities in China to reduce the road dust, since they are considered to be more water saving and efficient than the traditional sprinkling trucks. However, their effect on the formation of water-soluble organic compounds and the pollution control of fine particles (PM 2.5) remains unknown. We characterized the variations of chemical compositions in PM 2.5 collected on the road sides during the simulated operations of mist cannon truck and traditional sprinkling truck via Fourier transform ion cyclotron resonance mass spectrometry and ion chromatography. The mass concentrations of water-soluble organic carbon in PM 2.5 showed a significant increase (62 %–70 %) after air spraying. Furthermore, we found that water-soluble organic compounds, particularly organic nitrates, increased significantly via the interactions of reactive gas-phase organics, atmospheric oxidants and aerosol liquid water after air spraying, although the air spraying had a better effect on suppressing road dust than the ground aspersion. Moreover, the formation of PM 2.5 on the road segment where the mist cannon truck passed by was promoted, with an increase of up to 13 % in mass concentration after 25–35 min, on average. Thus, the application of mist cannon trucks potentially worsens the road atmospheric environment through the increase in PM 2.5 levels and the production of a large number of water-soluble organic compounds in PM 2.5. The overall results provide not only valuable insights to the formation processes of water-soluble organic compounds associated with aerosol liquid water in the road environment but also management strategies to regulate the operation of mist cannon trucks in China. [ABSTRACT FROM AUTHOR]

Due to special taste and medicinal properties, pickled sweat-sour garlic is one of the most popular garlic-based functional foods in China. The traditional pickling method of garlic is tedious, time consuming, laborious, low efficient, and easily influenced by environmental factors and microorganisms. In the present study, garlic cloves were subjected to two pickling methods: osmotic dehydration at atmospheric conditions (OD) and pulsed vacuum osmotic dehydration (PVOD). Pulsed vacuum impregnation was applied in order to evaluate the possibility of enhancement of pickling efficiency and quality of final product. The effect of OD and PVOD on mass transfer kinetics of sodium chloride, sucrose and acetic acid as well as quality attributes (color parameters such as L*, a*, b*, and thiosulfinates content) of pickled sweet and sour garlic cloves was investigated. Results indicate that PVOD promoted mass transfer of sodium chloride and acetic acid compared to the traditional OD method. However, there was no significant effect on mass transfer of sugar. PVOD significantly decreased thiosulfinates content (from 4.49 mg/mL to 1.91 mg/mL) and L* values (from 66.72 to 45.85) of garlic. During PVOD of garlic, samples gradually turned from white color to the desired amber color during the PVOD process. The findings of current work indicate that PVOD is a promising technique for garlic pickling as it enhances mass transfer and accelerates the degradation of thiosulfinates content in garlic. [ABSTRACT FROM AUTHOR]

To constrain sources of anthropogenic nitrogen (N) deposition is critical for effective reduction of reactive N emissions and better evaluation of N deposition effects. This study measured δ 15 N signatures of nitrate (NO 3 − ), ammonium (NH 4 + ) and total dissolved N (TDN) in precipitation at Guiyang, southwestern China and estimated contributions of dominant N sources using a Bayesian isotope mixing model. For NO 3 − , the contribution of non-fossil N oxides (NO x , mainly from biomass burning (24 ± 12%) and microbial N cycle (26 ± 5%)) equals that of fossil NO x , to which vehicle exhausts (31 ± 19%) contributed more than coal combustion (19 ± 9%). For NH 4 + , ammonia (NH 3 ) from volatilization sources (mainly animal wastes (22 ± 12%) and fertilizers (22 ± 10%)) contributed less than NH 3 from combustion sources (mainly biomass burning (17 ± 8%), vehicle exhausts (19 ± 11%) and coal combustions (19 ± 12%)). Dissolved organic N (DON) accounted for 41% in precipitation TDN deposition during the study period. Precipitation DON had higher δ 15 N values in cooler months (13.1‰) than in warmer months (−7.0‰), indicating the dominance of primary and secondary ON sources, respectively. These results newly underscored the importance of non-fossil NO x , fossil NH 3 and organic N in precipitation N inputs of urban environments. [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosols emitted from incomplete combustion of fossil fuels, biofuels, and biomass have significant effects on the environment and human health. Combustion-derived BC aerosols are an important component in haze pollution. High concentrations of BC aerosols were found in fine particulate matter (PM 2.5) in China, and source apportionment was the strategy underpinning targeted mitigation actions. Here, we present a Bayesian statistical model, a three-dimensional array of a stable carbon isotope (δ13C) and the ratios of non-sea-salt K+ to BC (nss-K+/BC) and ΔBC/ΔCO that is a reasonably inexpensive and rapid way to constrain BC source apportionments. This study analyzed 551 daily PM 2.5 samples collected in January 2018 in 18 large cities and at 1 remote site scattered across China. The results show that BC concentrations were generally higher in cities in northern China than they were in cities in southern China. Source apportionments indicate that BC in 44% of cities was mainly from liquid fuel combustion. In other sites, including 39% of cities, one suburban site, and one remote site, BC was mainly from biomass burning. These findings suggest that to improve air quality, the Chinese government should further strengthen controls on liquid fuel combustion and consider controlling biomass burning. • Using δ13C, K+/BC, and ΔBC/ΔCO, to identify black carbon sources across China. • Black carbon was mainly from liquid fuel combustion in 44% of the large cities in China. • Biomass burning was also an important source of black carbon. [ABSTRACT FROM AUTHOR]

This study systematically analyzed the concentrations of cations and anions and determined the pH in the rainwater at Guiyang from Oct. 2008 to Sep. 2009. The pH in the rainwater varied between 3.35 and 9.99 with a volume-weighted mean value of 4.23. The volume-weighted mean concentrations of anions followed the order SO>Cl>F>NO, whereas the volume-weighted mean concentrations of cations followed the order Ca>NH>Na>Mg>K. This finding indicates that SO was the main anion and that Ca and NH were the main cations. Significant correlations between each pair of ions (SO, NO, NH, Ca, and Mg) were observed, suggesting that CaSO, Ca(NO), MgSO, Mg(NO), NHNO, (NH)SO, and/or NHHSO exist in the atmosphere at Guiyang. The soil-derived species (such as Ca) played an important role in the neutralization of the acidity in rainwater. The SO and NO in the rainwater were mainly from anthropogenic sources, and their contributions accounted for 98.1 % and 94.7 %, respectively. NH was also most likely derived from anthropogenic sources, such as domestic and commercial sewage, and played an important role in the neutralization of the rainwater at Guiyang. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen isotopes of ammonium (δ15N–NH4 +) in precipitation have been analyzed, to study their monthly variations, from Oct. 2008 to Sep. 2009 at Guiyang, Southwest China. δ15N–NH4 + values were higher in winter and lower in summer showing a strong sine curve. In summer (rainy season), raindrop may remove more light ammonia by washout process, because raindrop incorporated 15NH3 preferentially while left the 14N in the atmosphere. At the same time, longer sunshine times imply more hv for producing H2SO4 of SO2 to H2SO4, which accelerates gaseous to particle conversion of NH3 to (NH4)2SO4 by unidirectional reactions for isotopic enriched 14N. The above two aspects can somewhat cause the seasonal variation of nitrogen isotopic composition, but are not the main or direct reasons. The temperature has an opposite trend with seasonal variation of δ15N values. The temperature not only causes seasonal variation of δ15N values, but also increases the volatilization rate of NH3 and microbial activities. And there is a robust linear relationship between temperature and δ15N, showing that the temperature is the main factor to decide the monthly variation of δ15N–NH4 +. [Copyright &y& Elsevier]

Epilithic mosses are characterized by insulation from substratum N and hence meet their N demand only by deposited N. This study investigated tissue C, total Chl and δ 13C of epilithic mosses along 2 transects across Guiyang urban (SW China), aiming at testing their responses to N deposition. Tissue C and total Chl decreased from the urban to rural, but δ 13Cmoss became less negative. With measurements of atmospheric CO2 and δ 13CO2, elevated N deposition was inferred as a primary factor for changes in moss C and isotopic signatures. Correlations between total Chl, tissue C and N signals indicated a nutritional effect on C fixation of epilithic mosses, but the response of δ 13Cmoss to N deposition could not be clearly differentiated from effects of other factors. Collective evidences suggest that C signals of epilithic mosses are useful proxies for N deposition but further works on physiological mechanisms are still needed. [Copyright &y& Elsevier]

Abstract: Nitrogen concentration and δ 15N in 175 epilithic moss samples were investigated along four directions from urban to rural sites in Guiyang, SW China. The spatial variations of moss N concentration and δ 15N revealed that atmospheric N deposition is dominated by NH x -N from two major sources (urban sewage NH3 and agricultural NH3), the deposition of urban-derived NH x followed a point source pattern characterized by an exponential decline with distance from the urban center, while the agricultural-derived NH x was shown to be a non-point source. The relationship between moss N concentration and distance (y =1.5e−0.13x +1.26) indicated that the maximum transporting distance of urban-derived NH x averaged 41km from the urban center, and it could be determined from the relationship between moss δ 15N and distance [y =2.54ln(x)−12.227] that urban-derived NH x was proportionally lower than agricultural-derived NH x in N deposition at sites beyond 17.2km from the urban center. Consequently, the variation of urban-derived NH x with distance from the urban center could be modeled as y =56.272e−0.116x −0.481 in the Guiyang area. [Copyright &y& Elsevier]

Drying characteristics and quality of apple slices were studied using microwave intermittent drying at different microwave power density (2.2, 3.5, 4.8, and 6.1 W/g), sample thickness (3, 5, 7, and 9 mm) and heating time in each cycle (4, 5, 6, and 7 s). Results showed that the approximate constant rate drying periods and falling rate drying periods were found in all the curves. The drying time decreased with increasing microwave power density and heating time in each cycle, while increased significantly with the growth of sample thickness. Weibull distribution model could fit the drying curves well in all conditions (R2 > 0.99) with the scale parameter values changed from 45.88 to 206.08 min and the shape parameters values varied from 1.514 to 1.69. The moisture effective diffusivity calculated by Weibull model ranged from 0.3217 × 10−9 to 1.435 × 10−9 m2·s−1. The flavor, texture and overall acceptability values displayed a decreasing tendency with the increase of microwave power density, while increased with the growth of thickness. And the shrinkage rates of apple slices showed a decline tendency with the increase of above parameters. Practical applications: Apple is a kind of popular and important fruits with high nutrient content, and it has been widely planted in China. Due to its high moisture content, fresh apples will subject to various deteriorative reactions during storage and thus lead to serious post‐harvest losses. Microwave drying technology has been widely used in dehydration of agricultural products in China because of the significant heating efficiency. However, the continuous microwave heating may easily cause the overheating of raw materials and undesirable changes in quality. Microwave intermittent drying (MID) was proposed on the basis of conventional microwave drying and regarded as an efficient processing method by solving the above issues. Currently this technology has been successfully applied to ginkgo fruits, yam and banana slices. Analyzing the effects of drying parameters on MID kinetics and quality of apple slices will have important significance for optimizing the processing efficiency and consumer acceptability of dried products. [ABSTRACT FROM AUTHOR]

Chlorine is an important atmospheric photochemical oxidant, but few studies have focused on atmospheric chlorine. In this study, PM2.5 samples were collected from urban and rural sites across China in January 2018, and concentrations of Cl− and other water-soluble ions in PM2.5 were analyzed. The size-segregated aerosol Cl− data measured across Chinese cities by other studies were compiled for comparison. The observed data demonstrated that the Cl− concentrations of PM2.5 in northern cities (5.0 ± 3.7 µg/m3) were higher than those in central (1.9 ± 1.2 µg/m3) and southern cities (0.84 ± 0.54 µg/m3), suggesting substantial chlorine emissions in northern cities during winter. The concentrations of Cl− in aerosol were significantly higher in urban regions (0.11–26.7 µg/m3) compared to than in rural regions (0.03–0.61 µg/m3) across China during winter, implying strong anthropogenic chlorine emission in cities. Based on the mole ratios of Cl−/Na+, Cl−/K+ and Cl−/ SO 4 2 − and the PMF model, Cl− in northern and central cities was mainly sourced from the coal combustion and biomass burning, but in southern cities, Cl− in PM2.5 was mainly affected by the equilibrium between gas-phase HCl and particulate Cl−. The size-segregated statistical data demonstrated that particulate Cl− had a bimodal pattern, and more Cl− was distributed in the fine model than that in the coarse mode in winter, with the opposite pattern was observed in summer. This may be attributed to both sources of atmospheric Cl− and Cl− involved in chemical processes. This study reports the concentrations of aerosol Cl− on a national scale, and provides important information for modeling the global atmospheric reactive chlorine distribution and the effects of chlorine on atmospheric photochemistry. [ABSTRACT FROM AUTHOR]

An obituary for Chinese Professor Chong-Wen Cao, who died on October 10, 2014, is presented.

A letter to the editor is presented which discusses the need for China to address its air pollution problem to improve human health.

The article presents a letter to the editor in which the author agrees with the views of Jie Zhang, President of Shanghai Jiao Tong University in China, who states that universities in China require quality faculty in order to compete internationally.

The C and N concentrations and stable isotopes in new and old tissues of the moss Haplocladium microphyllum were investigated at Guiyang and Gongga Mountain in SW China, aiming at revealing responses of these parameters to different environmental conditions and N deposition, elucidating the effect of N deposition on C fixation and signal variations during senescence. Atmospheric N deposition could be quantified by N in new tissues, showing a level of 30.18kgNha−1 yr−1 at Guiyang and 8.46kgNha−1 yr−1 at Mt. Gongga, old tissues presented lower C and N concentrations than new tissues, but there was no significant difference between N of new and old tissues at background area with lower N deposition, and the positive effect of N supply on C fixation was observed only for urban mosses under higher N deposition. More negative δ 13C mainly indicated the influences of anthropogenic CO2 sources on urban mosses, and higher δ 13C of mosses at background area was also related to higher altitude and lower temperature. More negative δ 15N of mosses mainly indicated N deposition at Guiyang was dominated by NH x –N from city wastes and sewage, while δ 15N of mosses at Mt. Gongga mainly indicated little anthropogenic N pollution in background area. Besides, no significant isotopic difference was found between new and old tissues in both areas, suggesting no isotopic effect occurred during the senescence of H. microphyllum. [Copyright &y& Elsevier]

Nitrate (NO 3 - ) is an important contributor to PM 2.5 which can adversely affect the environment and human health. A noticeable decrease in NO x concentrations has been reported due to the lockdown measures implemented to curb the spread of Corona Virus Disease 2019 (COVID-19). However, questions remain, regarding the nonlinear relationship between NO x and NO 3 - . Here, we collected PM 2.5 samples in two periods, before and during the lockdown of COVID-19 in Shanghai. Dual isotopes (δ 18 O-NO 3 - and δ 15 N-NO 3 - ) of NO 3 - were measured to investigate the formation pathways and potential sources of NO 3 - . The results showed that the concentration of NO 3 - decreased significantly during the lockdown period compared to the period before the lockdown. Additionally, the hydroxyl pathway was the dominant contributor to NO 3 - production during the lockdown period, while N 2 O 5 hydrolyses dominated the formation of NO 3 - before the lockdown. This change is largely attributable to alterations in the oxidative potential of the environment. In comparison to the period preceding the lockdown, the relative contributions of each NO x source remained largely unchanged throughout the lockdown periods. Nevertheless, the concentration of NO 3 - contributed by each NO x source exhibited a notable decline, particularly the mobile sources and coal combustion. Furthermore, the reduction extent of NO 3 - due to the lockdown period was also greater than the reduction during the Clean Air Actions (2013-2017). Our findings provide evidence that the COVID-19 lockdown led to a decrease in NO 3 - concentration due to changes in the formation pathway and reductions in NO x emissions from various sources., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Although total carbon (TC) is an important component of fine particulate matter (PM 2.5 : particulate matter with aerodynamic diameter of <2.5 μm); its sources remain partially unidentified, especially in coastal urban areas. With ongoing development of the global economy and maritime activities, ship-generated TC emissions in port areas cannot be neglected. In this study, from September 11, 2017 to August 31, 2018, we collected 355 p.m. 2.5 samples in Qingdao, China, to determine the water-soluble ion concentrations, TC concentrations, and stable carbon isotopes (δ 13 C TC ). During the open fishing season (OFS; September 11, 2017 to April 30, 2018) and the closed fishing season (CFS; May 1, 2018 to August 31, 2018), the TC concentrations were 9.30 ± 5.38 μg/m 3 and 3.36 ± 2.10 μg/m 3 respectively, and the corresponding δ 13 C TC values were -24.53‰ ± 1.17‰ and -27.03‰ ± 0.91‰, respectively, indicating significant differences (p < 0.05) between the two periods. The differences in TC concentrations and the δ 13 C TC values between the OFS and CFS reflect changes in the source of contamination. Bayesian model was used to quantify the contributions of different TC sources, revealing that ship emissions accounted for approximately 35.3% of the total, which was close to the contribution from the largest source, i.e., motor vehicles (39%). Using the ship emission inventory, Qingdao's ship emissions were further quantified at 455 metric tons, representing 35%-40% of the total TC emissions around Qingdao. Notably, fishing ships contributed approximately 40% of the total ship emissions. These findings underscore the considerable impact of ship emissions, particularly those from fishing ships, on TC concentrations in coastal urban areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Atmospheric ambient gaseous ammonia (NH 3 ), the most abundant alkaline gas, affects public health and climate change through its key role in the formation of secondary aerosols via reactions with acidic gases. Estimation of the contributions of ammonia sources is very challenging in the urban atmosphere. Stable nitrogen isotope ratio (δ 15 N) measurements have shown that urban aerosol NH 4 + and gaseous NH 3 are derived from fossil fuel combustion-related (FF) sources, such as coal combustion, NH 3 slip, and vehicle exhaust, and volatilization-related sources, such as agriculture and urban water volatilization. Biomass burning (BB) sources, especially residential biofuel, can produce vast quantities of NH 3 and other pollutants and may greatly influence air quality and contribute to increased urban NH 3 samples at three urban sites in Central China during autumn and analyzed the major water-soluble ions and δ 2.5 samples at three urban sites in Central China during autumn and analyzed the major water-soluble ions and δ 15 N values of aerosol NH 4 + . The concentrations of NH 4 + increased as the temperature decreased close to winter, whereas the δ 15 N values did not show this pattern. According to the Bayesian model after isotope fractionation correction, FF sources contributed to 56.4 ± 17.1%, 46.4 ± 18.2%, and 51.8 ± 14.9% of aerosol NH 4 + in Nanchang, Wuhan, and Changsha, respectively, throughout autumn. The contributions from BB sources were 34.5 ± 20.4%, 46.4 ± 21.4%, and 40.4 ± 17.4% for Nanchang, Wuhan, and Changsha, respectively. We also found the fraction of aerosol NH 4 + from BB increased in all three cities from September to November 2017, which was likely caused by increased heating demands with the decrease in temperature during the season. Furthermore, BB was responsible for a severe haze event (maximum PM 2.5 of 205.69 μg/m 3 ) in Nanchang. These findings suggest government controls to improve air quality should include BB sources in addition to FF sources., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In China, coal combustion is the most important source of atmospheric sulfur pollution. Moss sulfur isotopic signatures have been believed to hold source-specific information that can serve as a fingerprint to identify atmospheric sulfur sources. In cities where only local coals were combusted, we observed a good correspondence of average sulfur isotope ratios in urban mosses (Haplocladium microphyllum) to the values of local coals (δ(coals) = 1.455δ(mosses)- 3.945, R(2) = 0.975, p = 0.01). But if different types of coals were combusted, we did not know whether moss sulfur isotope ratios can indicate mixed coals. To confirm this, using a mixing model we estimated the ratios of imported coal to local coals at cities where both coals were used. We found that the estimated ratios at large cities (>1 million people) where both coals were used were similar to the reported ratios in their respective provinces. For small cities (<0.5 million people) in Jiangxi Province and other provinces, the estimated ratios were higher than the reported ratios because the relatively cheaper local coals were less used in all the small cities except in cities where local coal deposits were found nearby. The comparison results showed that moss sulfur isotope is a useful tool for indicating coal-derived sulfur even in cities where mixed coals were combusted.

In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO(4)(2-)/NH(4)(+) ratios, each people SO(2) emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal delta(34)S and NH(4)(+)-N wet deposition, respectively, indicating that local coal and animal NH(3) are the major atmospheric S and N sources., (Copyright 2009 Elsevier Ltd. All rights reserved.)

A study of the continuous precipitation in Guiyang has been taken during October 30 and November 7. The results showed that the range of pH was between 3.65 and 7.20, and volume-weighted mean was 4.24. SO4(2-) was the main anion and volume-weighted mean was 119.06 microeq x L(-1), accounting for 80.63% of total anions. While Ca2+ was the main cation and volume-weighted mean was 48.87 microeq x L(-1), accounting for 48.16% of total cation and NH4+ was 38.38 microeq x L(-1), 37.82%. Good correlations between Mg2+, Ca2+, NH4+ and SO4(2-) are observed, which may exist as MgSO4, CaSO4 and (NH4)2SO4 in the rainwater in Guiyang City. Different ions of the atmosphere had different scavenged ways and rate in the precipitation process. In the initial stage of precipitation, the ions such as Mg2+, which were rich in coarse particles, were quickly removed from atmosphere. However the ions such as NH4+ and SO4(2-), which were rich in fine particles, could remain in the atmosphere for a longer time.