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While intensive peach production has expanded rapidly in recent years, few studies have explored the environmental impacts associated with specific regional systems or the optimal management strategies to minimize associated environmental risks. Here, data from a survey of 290 native farmers were used to conduct a life cycle assessment to quantify the acidification potential (AP), global warming potential (GWP), eutrophication potential (EP), and reactive nitrogen (Nr) losses in peach production in Pinggu District, Beijing. Total annual Nr losses, and GWP, AP, and EP values for peach production in Pinggu District were respectively 10.7 kg N t−1, 857 kg CO2-eq t−1, 12.9 kg SO2 eq t− 1, and 4.1 kg PO4-eq t−1. The principal driving factors were fertilizer production, transportation, and application, which together accounted for 94%, 67%, 75%, and 94% of Nr losses, GWP, AP, and EP, respectively. In the high yield, high nitrogen-use efficiency (HH) group, relative values of Nr losses, GWP, AP, and EP were respectively 33%, 25%, 39%, and 32% lower than the overall averages for 290 orchards. Further analyses indicate that improved farming practices such as decreasing application rates of fertilizers, increasing proportion of base fertilization rate, and proper fertilization frequency in the HH group were the main reasons for these orchards’ better performance in peach yields and partial factor productivity of nitrogen fertilizer, and their reduced environmental impacts. These results highlight the need to optimize nutrient management in peach production in order simultaneously to realize both environmental sustainability and high productivity in the peach production system.

Airborne bacteria are important components of fine particulate matter (PM2.5), and have received increasing attention because of their impacts on public health and ecological systems. However, the relationships between the bacterial community and PM2.5 pollution are poorly understood. The properties of bacterial communities in Beijing at low, medium and high PM2.5 levels were analyzed during winter (December 2015–January 2016; January 2017) and spring (March 2016–May 2016; April 2017–May 2017). Variations in bacterial concentrations, Shannon and Simpson indices and relative abundance were significantly related to the seasons. In winter, there were no significant differences in bacterial communities among three PM2.5 pollution levels. In contrast, significant correlations between bacterial abundance and PM2.5 levels were observed in spring, and the bacterial concentrations, community richness and diversity indices were significantly higher on heavily polluted days compared to other pollution levels. Correlation results showed that relative humidity (RH), wind speed (WS), and O3 were most closely associated with microbial community structure in winter (P < 0.05), but temperature (T), NO2, SO2, and CO in spring, while CO, NO2, O3, RH, and WS had significant relationships (|r| = 0.360–0.553, P < 0.05) with bacterial concentrations in winter, but PM2.5, O3, T, and RH (|r| = 0.281–0.527, P < 0.05) in spring. Chemical composition, especially that of secondary aerosol particles, which were mainly produced from anthropogenic sources (e.g. fossil fuel combustion, road traffic and industrial emissions), exerted the most control of bacterial community structure of PM2.5. The effects of PM2.5 levels on the bacterial community were modified by environmental conditions, heavy metal and nutrient contents of the PM2.5. The relationships described provide a foundation for further research into the environmental and PM2.5 chemical composition controls on the bacterial community and related health risk from air pollution.

Stringent emission controls during the Asia Pacific Economic Cooperation Summit (APEC; November 5–11, 2014) provide a valuable opportunity to examine the impact of such measures on the chemical properties of PM2.5 and other air pollutants. Here, we measured the water-soluble inorganic ions (WSII) and carbonaceous species in PM2.5, NH3 and NO2 at multiple sites in Beijing between September and November 2014. Relative to the pre-APEC period (September and October 2014), significant reductions in the average concentrations of WSII (69% for NO3−, 68% for SO42−, 78% for NH4+, and 29–71% for other species), elemental carbon (EC, 43%) and organic carbon (OC, 45%) in PM2.5 were found during the APEC period. The contributions of secondary inorganic ions (SIA, including SO42−, NO3−, and NH4+) to PM2.5 were significantly lower during the APEC period (9–44%), indicating a combination of lower gaseous precursor emissions and a relative weak secondary aerosol formation. Ion-balance calculations indicated that the PM2.5 sample in the pre-APEC period was alkaline but was acidic during the APEC period. Relatively lower mean concentrations of EC (1.5 μg m−3), OC (10.5 μg m−3), secondary organic carbon (SOC, 3.3 μg m−3), secondary organic aerosol (SOA, 5.9 μg m−3) and primary organic aerosol (POA, 10.0 μg m−3) appeared during the APEC period. The average concentrations of NH3 and NO2 at all road sites were significantly reduced by 48 and 60% during the APEC period, which is consistent with clear reductions in satellite NH3 columns over Beijing city in the same period. This finding suggests that reducing traffic emissions could be a feasible method to control urban NH3 pollution. During the APEC period, concentrations of PM2.5, PM10, NO2, SO2 and CO from the Beijing city monitoring network showed significant reductions at urban (20–60%) and rural (18–57%) sites, whereas O3 concentrations increased significantly (by 93% and 53%, respectively). The control measures taken in the APEC period substantially decreased PM2.5 pollution but can increase ground O3, which also merits attention.

Atmospheric deposition is an important pathway for the input of anthropogenic and natural nutrients to terrestrial and aquatic ecosystems. However, previous measurements focused mainly on hotspot locations, ignoring the fact that the deposition magnitudes of various nutrient species (e.g., nitrogen (N), phosphorus (P)) at a national scale should be investigated jointly. To better characterize national scale bulk deposition, precipitation samples were collected at 41 sites across China from September 2015 to August 2016 and September 2017 to August 2018. The bulk deposition fluxes of total nitrogen (TN) and total phosphorus (TP) over the network were 27.5 kg N ha

We investigated variations of PM

The Clean Air Action implemented by the Chinese government in 2013 has greatly improved air quality in the North China Plain (NCP). In this work, we report changes in the chemical components of atmospheric fine particulate matter (PM

This study investigates the concentrations and δ15N values of NH3 in Beijing during and after the 2020 COVID-19 lockdown. Higher NH3 concentrations and lower δ15N-NH3(measured) were observed at most sites in 2020 compared to 2017. Except for a site inside a tunnel, NH3 concentrations did not increase significantly after the lockdown had ended compared to those during the lockdown, while δ15N-NH3(measured) increased by 2.1–9.9‰. Nonagricultural sources (fossil fuel and urban waste) overall contributed 81% and 62% of NH3 at on-road (tunnel interior) and nonroad (CAU) sites in 2020, respectively, comparable to those in 2017 (without significant difference). The contribution of nonagricultural sources slightly increased after the lockdown compared to the contribution during the lockdown at the nonroad site and hardly changed at the tunnel interior site. Our results suggest that (1) unfavorable meteorological conditions, especially lower boundary layer heights and changes in regional transport patterns, might play a more important role than reduced anthropogenic emissions in the temporal variations of Beijing NH3 and (2) the effect of reduced anthropogenic emissions, during the COVID-19 outbreak or with the future implementation of emission control strategies, on atmospheric NH3 can be better demonstrated by isotope-based source apportionment of NH3, rather than only by changes in NH3 concentrations.

Ammonia (NH

In order to cope with heavy haze pollution in Beijing, the Air Pollution Prevention and Control Action Plan was issued in 2013. In this study, we took January observations from 2014 to 2018 as a case study to assess wintertime air quality improvement in Beijing after five years of continuous emission control measures and to investigate the causes of haze formation. SO2 and NO2 concentrations in January 2018 decreased by 84% and 41% from January 2014, while NH3 concentrations remained relatively stable during these years with an average of 7.28 μg m−3. The mean concentrations of PM2.5 and water-soluble inorganic ions declined over the study period, while compared with 2014, decreased SO42− ratio and increased NO3− contribution in PM2.5 were observed, highlighting the importance of reactive nitrogen (Nr) pollution control. High concentrations of NH3, NO2, as well as NH4+ and NO3− in PM2.5 at roadside monitoring sites, indicated that vehicle sources played a vital role in local urban Nr emissions. Finally, we found most NH3 existed in the gas phase in the Beijing atmosphere, even on polluted winter days, suggesting a considerable risk for additional secondary aerosol formation. Our findings demonstrate the effectiveness of the emissions control in alleviating Beijing's air pollution. Significant reductions of precursor emissions are needed to achieve the goals set by air quality standards in the future, especially for NH3. It is especially crucial to jointly consider and control multiple pollution sources to effectively reduce the high levels of air pollution that remain in Beijing.

Due to increasing global demand for crop production and energy use, more and more reactive nitrogen (Nr) has been generated and emitted to the environment. As a result, global atmospheric nitrogen (N) deposition has tripled since the industrial revolution and the ecological environment and human health have been harmed. In this study, we measured dry and wet/bulk N deposition from July 2013 to December 2015 in a semi-arid grassland of Duolun County, Inner Mongolia, China. The samples of dry and wet/bulk N deposition were collected monthly with a DELTA (DEnuder for Long Term Atmospheric sampling) system and with Gradko passive samplers and a precipitation gauge. The measured results show that the annual mean concentrations of NH3, NO2, HNO3, particulate NH4+ (pNH4+) and particulate NO3− (pNO3−) in atmosphere were 2.33, 1.90, 0.18, 1.42 and 0.42 μg N/m3, respectively, and that the annual mean volume-weighted concentrations ofNH4+-N and NO3−-N in precipitation were 2.71 and 1.99 mg N/L, respectively. The concentrations of Nr components (including NH3, NO2, HNO3, pNH4+, pNO3−,NH4+-N and NO3−-N) exhibited different seasonal variations. Specifically, NO2 and HNO3 exhibited higher concentrations in autumn than in summer, while the other Nr components (NH3, pNH4+, pNO3−,NH4+-N and NO3−-N) showed the highest values in summer. Based on measured concentrations of Nr components and their deposition velocities estimated using the GEOS-Chem global atmospheric chemical transport model, the calculated annual mean dry deposition fluxes were 3.17, 1.13, 0.63, 0.91 and 0.36 kg N/(hm2•a) for NH3, NO2, HNO3, pNH4+ and pNO3−, respectively, and the calculated annual mean wet/bulk deposition fluxes were 5.37 and 3.15 kg N/(hm2•a) forNH4+-N and NO3−-N, respectively. The estimated annual N deposition (including dry N deposition and wet/bulk N deposition) reached 14.7 kg N/(hm2•a) in grassland of Duolun County, approaching to the upper limit of the N critical load (10–15 kg N/(hm2•a)). Dry and wet/bulk deposition fluxes of all Nr components (with an exception of HNO3) showed similar seasonal variations with the maximum deposition flux in summer and the minimum in winter. Reduced Nr components (e.g., gaseous NH3 and pNH4+ in atmosphere andNH4+-N in precipitation) dominated the total N deposition at the sampling site (accounted for 64% of the total N deposition), suggesting that the deposited atmospheric Nr mainly originated from agricultural activities. Considering the projected future increases in crop and livestock production in Inner Mongolia, the ecological and human risks to the negative effects of increased N deposition could be increased if no mitigation measures are taken.

Atmospheric reactive nitrogen (N) has induced large impacts on air pollution and ecosystem health worldwide. Atmospheric reactive N emission and deposition have largely increased in China since 1980 due to rapid agricultural, industrial, and urban development. But scientific gaps still remain in the regional and temporal variability in atmospheric N emissions and deposition. Meanwhile, the environmental impacts of N pollution and deposition are of great concern in China. This paper overviews the status of anthropogenic N emissions and deposition and their linkages to air pollution in China. The major findings include two aspects: (1) anthropogenic reactive N (e.g., NH3 and NOx) emissions contribute greatly to secondary inorganic aerosol formation and haze pollution and (2) dry N deposition is comparable in importance to wet N deposition, suggesting that both dry and wet deposition should be quantified simultaneously. Future research challenges on atmospheric N emission and deposition are discussed as well. China needs to (1) reduce the uncertainties of national emission inventory of various N species, especially organic N compounds; (2) establish national networks for atmospheric N concentration and deposition monitoring; and (3) evaluate ecological and environmental impacts of N pollution and deposition in typical ecosystems. Last but not least, N deposition modeling tools should be improved based on localized parameters and further used in future N regulation.

Air pollution especially of PM_(2.5) pollution is a serious problem in Beijing. In order to quantify the effect of a festival in which pollution was expected to be reduced, we collected and analyzed PM_(2.5) samples in urban Beijing during the 2015 Spring Festival (from February 9^(th) to March 6^(th) 2015). We divided the sampling period into three phases: non-haze, haze and firework days. The average concentration of PM_(2.5) was highest on firework days at 248.9 μg m^(-3), followed by haze days (199.9 μg m^(-3)) and non-haze days (90.8 μg m^(-3)). The air quality of non-haze days during the holiday was better than that during non-holiday periods. Secondary inorganic ions (SO_4^(2-), NO_3^- and NH_4^+) were enriched on the haze days, while those on firework days contained large amounts of Cl^- and K^+, but small amounts of NO_3^- and NH_4^+. Ratios of NO_3^-/SO_4^(2-), SO_4^(2-)/K^+ and Cl^-/K^+ effectively distinguished the characteristics of PM_(2.5) between firework events and haze days. Ion balance calculations indicated that the acidity of PM_(2.5) from firework days was higher than that from haze and non-haze days. A method using enrichment factors (EF) found that crustal elements (EF ＜ 10 on all three types of days) included Ca, Al, Fe, Na, Co, Ni, P, Ti, and V; firework elements (EF ＞ 10 on firework days, significantly higher than haze days) were made up of Ba, Cr, Cu, Mg, Pb, S, Si, and Zn; common anthropogenic pollution elements (EF ＞ 10 in all three types of days) were As, Cd, Cu, Pb, S, Sb, Zn. Differences in chemical characteristics indicated that holidays such as the Spring Festival can affect air pollution patterns in two ways: a decrease in the population and vehicles but an increase in activities such as firework displays.

To investigate the formation and evolution mechanism of haze pollution in Beijing cold days, we measured reactive nitrogen gases (e.g. NH3 and HNO3), SO2 and major water-soluble inorganic ions of PM2.5 simultaneously in a two-year (from November to April) study. We found that NH3 and NO3 − have the highest concentrations among the gaseous precursors and inorganic components of PM2.5, respectively. The total NH x (gaseous NH3 and particle NH4 +) was mostly in excess the need to neutralize acid compounds. During the whole study period, the aerosol pH with an average value of 4.05. From normal period into haze episodes, the aerosol pH tends to decrease and the concentration of all species (gases and particles) increases. Meanwhile, declined gas fractions exhibited that enhanced partitioning from HNO3, NH3 and SO2 to their corresponding particle phases. Under the heavy haze period, most HNO3 (79%) has entered into NO3 −, about 41% NH3 remaining as free NH3, while only about 51% of SO2 has been oxidized to SO4 2−, implying the severe Nr pollution in atmosphere of Beijing in winter. Further analysis shows relative humidity (RH) plays an important driving role on the SNA (sulfate (SO4 2−), nitrate (NO3 −), ammonium (NH4 +)) formation and particulate NO3 − formed at a relatively low RH (20%–60%) and SO4 2− at a high RH (40%–80%). Thus, synchronized abatement of multi-pollutants emissions especially for NH3 emission reduction at a regional scale is necessary for mitigating megacities ambient PM2.5 pollution and achieving the UN sustainable development goal through improving N use efficiency in agriculture.

Few related studies have been carried out for northwest China's the inland, although the increasing inorganic reactive nitrogen (Nr) deposition and severe air pollution in China have attracted considerable attention. Based on eight-year measurements of the concentrations of NH3, HNO3, particulate (p) NH4+, pNO3−, and NO2 in the air and inorganic nitrogen (NH4+, NO3−) in the precipitation at a rural site in Wuwei, Gansu Province, we quantified the dry and bulk/wet Nr deposition fluxes and analyzed their temporal trends in combination with air pollution data (2015–2018). The concentrations of the single Nr species in the air did not exhibit significant seasonal variations, except for that of pNO3− which were the highest in summer and the lowest in winter. The average annual total Nr (dry + bulk) deposition was 27.2 ± 6.7 kg N ha−1 with a significant (p

With rapid economic growth in China, anthropogenic reactive nitrogen (Nr) emissions have more than doubled over the last two or three decades. Atmospheric Nr pollution is an environmental concern in China especially in megacities such as Beijing. In order to identify the impact of emission sources on atmospheric Nr pollution, we measured atmospheric Nr concentrations and their isotopic composition (δ15N) dynamics at three typical sites: landfill, pig farm and road traffic sites in Beijing from April 2010 to March 2011. Passive samplers were used for monitoring ammonia (NH3) and nitrogen dioxide (NO2), two major Nr species, while their δ15N values were measured by a diffusion method combined with mass spectrometer approach. The raw water pool of the landfill and fattening house of the pig farm were important NH3 sources with mean NH3 concentrations being 2,829 and 2,369 µg/m3, respectively, while the road traffic site was a minor NH3 source (10.6 µg/m3). NH3 concentrations at sites besides the landfill and roads were high in summer and low in winter due to the annual variation of temperature and the change of emission source intensity. In contrast, the NH3 concentrations inside the pig farm house were high in winter and low in summer, for the barn windows were open in summer and closed in winter. The mean NO2 concentrations were 89.8, 32.9 and 23.0 µg/m3 at the road traffic, the landfill and pig farm sites, respectively. Due to vehicle fuel combustion, NO2 concentration at the road traffic was the highest among the three sources, and the road traffic was a main NO2 emission source. PM10, pNH4 + and pNO3–concentrations in particulate matter were higher in summer than in winter (except PM10 for the pig farm). The δ15NH3 values ranged from–19.14‰ to 7.82‰, with an average of–0.05‰ for the landfill site, and the lowest values were observed in June and July. The δ15NH3 values for the pig farm site ranged from–29.78‰ to–14.05‰ with an average of–24.51‰, and the δ15NH3 values were more negative in summer than in the other seasons. The δ15NO2 values were–9.63‰ to 7.04‰ with an average of–3.72‰ for the road traffic site. The δ15NO2 values were more negative in summer than those in the other seasons. The different δ15N values for the various Nr species in different sources may serve as important indicators for identifying atmospheric Nr sources in megacities. The results may also provide the theoretical basis for research on the atmospheric N deposition and its sources.

Precipitation chemistry and atmospheric nitrogen (N) deposition are of great concern worldwide due to their close relationships with air quality and impacts on ecosystems. However, evaluation of the chemical composition of precipitation and N deposition flux in rural areas of Beijing has received little attention to date. This paper presents the chemical constituents, possible sources and wet deposition fluxes of water-soluble ions (NH4+, NO3−, SO42−, Cl−, Na+, K+, Ca2+, Mg2+) in precipitation samples collected during 2017–2018 at a rural site located at northwest of Beijing city; meanwhile, dry deposition of reactive N species (gaseous ammonia, nitrogen dioxide, nitric acid, and particulate (p) NH4+ and NO3−) were also quantified. During this 2-year period, the volume-weighted mean (VWM) pH of precipitation was 6.73, and all samples had pH values above 6.0. The VWM electric conductivity of precipitation and the mean sum of all measured ions was 43.8 μS cm−1 and 591.9 μeq L−1, respectively, indicating a significant impact of atmospheric pollution. Ca2+ and NH4+ were the dominant neutralizing species for precipitation acidity. Positive matrix factorization analysis further confirmed five sources for water-soluble ions, including sea salt aging, secondary formation, agriculture, crust, and biomass burning. The annual mean wet N deposition was 4.6, 3.4 and 8.0 kg N ha−1 yr−1 for NH4+, NO3− and total inorganic N, respectively. The total dry N deposition was dominated by gaseous ammonia (11.5 kg N ha−1 yr−1). The total N deposition (wet plus dry) was 27.7 kg N ha−1 yr−1, where dry deposition contributed to 75% and wet deposition 25% of the total. The simulations from the GEOS-Chem model indicate that agricultural (fertilizer use and livestock) and nonagricultural sources (industry, power plant, and transportation) are both important contributors to total N deposition. These results could be useful in evaluating/developing emission control policies to protect the eco-environment in Beijing.

Weekly vertical profiles of ammonia (NH3) were measured at 16 heights on the Beijing 325 m meteorological tower for 1 year from March 2016 to March 2017. The average NH3 concentrations exceeded 4 µg m−3 at all heights with an overall average (±1σ) value of 13.3 (±4.8) µg m−3. The highest NH3 concentrations along the vertical profiles mostly occurred from 32 to 63 m, decreasing both towards the surface and at higher altitudes. Significant decreases in NH3 concentrations were only found at the top two heights (280 and 320 m). These results suggest an NH3 rich atmosphere during all seasons in urban Beijing, from the ground to at least 320 m. The highest seasonal NH3 concentrations across the profile were observed in summer (18.2 µg m−3) with high temperature, followed by spring (13.4 µg m−3), autumn (12.1 µg m−3) and winter (8.3 µg m−3). A significant vertical variation in the NH3 concentration was only found in summer. Source region analyses suggest that air masses from intensive agricultural regions to the south contribute most to the high NH3 concentrations in Beijing. Local sources such as traffic emissions also appear to be important contributors to atmospheric NH3 in this urban environment.

The implementation of strict emission control measures in Beijing and surrounding regions during the 2015 China Victory Day Parade provided a valuable opportunity to investigate related air quality improvements in a megacity. We measured NH3, NO2 and PM2.5 at multiple sites in and outside Beijing and summarized concentrations of PM2.5, PM10, NO2, SO2 and CO in 291 cities across China from a national urban air quality monitoring network between August and September 2015. Consistently significant reductions of 12–35 % for NH3 and 33–59 % for NO2 in different areas of Beijing during the emission control period (referred to as the Parade Blue period) were observed compared with measurements in the pre- and post-Parade Blue periods without emission controls. Average NH3 and NO2 concentrations at sites near traffic were strongly correlated and showed positive and significant responses to traffic reduction measures, suggesting that traffic is an important source of both NH3 and NOx in urban Beijing. Daily concentrations of PM2.5 and secondary inorganic aerosol (sulfate, ammonium and nitrate) at the urban and rural sites both decreased during the Parade Blue period. During (after) the emission control period, concentrations of PM2.5, PM10, NO2, SO2 and CO from the national city-monitoring network showed the largest decrease (increase) of 34–72 % (50–214 %) in Beijing, a smaller decrease (a moderate increase) of 1–32 % (16–44 %) in emission control regions outside Beijing and an increase (decrease) of 6–16 % (−2–7 %) in non-emission-control regions of China. Integrated analysis of modelling and monitoring results demonstrated that emission control measures made a major contribution to air quality improvement in Beijing compared with a minor contribution from favourable meteorological conditions during the Parade Blue period. These results show that controls of secondary aerosol precursors (NH3, SO2 and NOx) locally and regionally are key to curbing air pollution in Beijing and probably in other mega cities worldwide.

Air pollution is one of the most serious environmental problems in China due to its rapid economic development alongside a very large consumption of fossil fuel, particularly in the North China Plain (NCP). During the period 2011–2014, we integrated active and passive sampling methods to perform continuous measurements of NH3, HNO3, NO2, and PM2.5 at two urban, one suburban, and two rural sites in the NCP. The annual average concentrations of NH3, NO2, and HNO3 across the five sites were in the ranges 8.5–23.0, 22.2–50.5, and 5.5–9.7 μg m−3, respectively, showing no significant spatial differences for NH3 and HNO3 but significantly higher NO2 concentration at the urban sites. At each site, annual average concentrations of NH3 and NO2 showed increasing and decreasing trends, respectively, while there was no obvious trend in annual HNO3 concentrations. Daily PM2.5 concentrations ranged from 11.8 to 621.0 μg m−3 at the urban site, from 19.8 to 692.9 μg m−3 at the suburban site, and from 23.9 to 754.5 μg m−3 at the two rural sites, with more than 70 % of sampling days exceeding 75 μg m−3. Concentrations of water-soluble ions in PM2.5 ranked differently between the non-rural and rural sites. The three dominant ions were NH4+, NO3−, and SO42− and mainly existed as (NH4)2SO4, NH4HSO4, and NH4NO3, and their concentrations averaged 48.6 ± 44.9, 41.2 ± 40.8, and 49.6 ± 35.9 μg m−3 at the urban, suburban, and rural sites, respectively. Ion balance calculations indicated that PM2.5 was neutral at the non-rural sites but acidic at the rural sites. Seasonal variations of the gases and aerosols exhibited different patterns, depending on source emission strength and meteorological conditions. Our results suggest that a feasible pathway to control PM2.5 pollution in the NCP should target ammonia and acid gases together. Electronic supplementary material The online version of this article (doi:10.1007/s11356-015-5648-3) contains supplementary material, which is available to authorized users.

Seventy-six rain samples from forty-seven rain events and TSP aerosol samples throughout the entire year of 2005 were collected in Shanghai, China. The annual mean pH in rain was 4.49 with the lowest pH of 2.95, and the frequency of acid rain was 71% in 2005. The acidity of rain increased more than 15 times in the past 8 years compared to 1997. The volume-weighted mean ionic concentrations of the acidic ions, SO 4 2− and NO 3 − in rainwater were 199.59 and 49.80 μeq/L with maximum of 832.67 and 236.59 μeq/L, respectively. The concentration of SO 4 2− was higher than the most polluted cities abroad, indicating Shanghai has been a severe polluted city over the world. The high coal/fuel consumption from urbanization and the rapid increase of vehicles resulted in the high emission of SO 2 and NO x , the precursor of the high concentration of acidic ions, SO 4 2− and NO 3 − , which were the main reason of the severe acid rain in Shanghai. The major ions showed clear temporal variations with higher concentrations of SO 4 2− , NO 3 − , NH 4 + , and Ca 2+ in spring/winter, of Na + , Cl − , K + , and Mg 2+ in autumn, and the lowest of all the ions in summer. SO 4 2− and NO 3 − were mainly in the form of CaSO 4 and Ca(NO 3 ) 2 , which showed the dominant neutralization effect of Ca 2+ over NH 4 + . Source identification indicated that SO 4 2− , NO 3 − , NH 4 + and most Ca 2+ derived from anthropogenic sources, K + , Mg 2+ and partial Ca 2+ originated from mineral, and almost all the Cl − and Na + from the sea. The chemistry of precipitation in Shanghai was under the influence of local pollution sources and the long- and moderate-range transport through back trajectory analysis.

Daily PM 2.5 and TSP and their chemical composition with two dust events (DS1: 9–10 March and DS2: 27–30 March) were simultaneously observed for the period of 9 March–23 April 2004 from a monitoring network over China. Five monitoring sites were performed along the transport pathway of Asian dust storm, located in Northwest, North, East, and Southeast regions of China. The dust and non-dust days exhibited different characteristics with respect to the composition and the meteorological conditions. In non-dust days, particulate pollution was found to be associated with the city economy, and it primarily consisted of the crustal, the secondary, and the carbonaceous material. In the dust episodes, significant increase in the particle concentration with a large part of the secondary components diluted by the crustal components was observed at all the sites. Particles were getting more and more acidic as the episodic dust progressed eastward. Dust particles were suggested to react with SO 2 /NO X /sulfate/nitrate based on the variations of SO 4 2− /Ca 2+ and NO 3 − /Ca 2+ along the transport pathway, and the formation mechanism of sulfate and nitrate was proved to be different. Positive matrix factorization analysis showed that the sources from the upstream and the transport pathways could account for 49%, 82%, and 28% of PM mass, crust, and secondary aerosol, respectively, and the contribution decreased, as the dust made its way from source area to the coastal regions. Enrichment factors of the species presented significant correlations among different sites in the dust episodes, suggesting the significant impact of those dust emissions on the local environment.

Aerosol samples of PM2.5 and PM10 in a period of intensive haze-fog (HF) events were collected to investigate the chemical characteristics of air pollution in Beijing. The air quality in HF episodes was much worse than that in nonhaze-fog (NHF) days. The concentrations of elements and water-soluble (WS) ions (K+, So4(2-), and NO3-) in HF episodes were more than 10 times higher than those in NHF days. Most of the chemical species in PM2.5 and the secondary species (NH4+, So4(2-), and NO3-) in PM10 showed significant difference between HF from westerly direction (HFW) and southerly direction (HFS). The concentrations of secondary species in HFS were much higher than those in HFW, and other chemical species in HFS were lower than those in HFW. The sources of PM2.5 were more from areas on the regional scale due to its tendency for long-range transport, while PM10 was more limited to the local sources. Aerosol particles were more acidic in HFS and more alkaline in HFW. The secondary species were the major chemical components of the aerosol in HF episodes, and their concentrations increased in the order of NHFHFWHFS. High concentrations of the secondary aerosol in HF episodes were likely due to the higher sulfur and nitrogen oxidation rate in aqueous-phase reactions. The serious air pollution in HF episodes was strongly correlated with the meteorological conditions and the emissions of pollutants from anthropogenic sources.

Fifty-three rain events throughout the entire year of 2003 were collected in Beijing and the concentration of 15 major ions with the pH of the rainwater were analyzed. The close correlations of the acidity in rainwater with the concentrations of aerosol and gases in the air were observed and elaborated. The scavenging of the pollutants from the air directly affects the pH and composition of the rainwater. The major ions in rainwater in Beijing were SO42−, NO3−, Cl−, NH4+, Ca2+, Mg2+, K+, and F−. The alkaline cations, NH4+ and Ca2+, acted as acid neutralizers and buffered the acidity of rain. The temporal variation of those major pollution ions in rainwater was similar to that of the air pollution. The concentrations of SO42−, NO3−, and NH4+ have increased for the last two decades and likely indicated that the air pollution has become more and more serious in Beijing since the 1980s. The ratio of the concentration of SO42− to NO3− observed in 2003 was much lower than that in 1981, indicating that the air pollution resulting from the traffic emission, NOx, has been more significant. A remarkably positive correlation between pH and Ca2+ concentration illustrates that Ca2+ generally from mineral aerosols plays an important role in buffering rainwater acidity in Beijing and in northern China at all times. The concentrations of SO42− and NO3−, the predominant acid anions in rain, was much higher in Beijing than other cities, suggesting that the anthropogenic air pollution in Beijing has been a much more serious problem than other places.

Data on bulk nitrogen deposition, plant foliar nitrogen and crop nitrogen uptake in China between ad 1980 and ad 2010 show that the average annual bulk deposition of nitrogen increased by approximately 8 kilograms of nitrogen per hectare during that period and that nitrogen deposition rates in the industrialized and agriculturally intensified regions of China are as high as the peak levels of deposition in northwestern Europe in the 1980s. Atmospheric nitrogen emissions have increased substantially since the beginning of the industrial revolution, and the resulting deposition of nitrogen can have detrimental effects on human and ecosystem health. But little is known about the magnitude and environmental consequences of nitrogen deposition in today's fastest growing economy, China. This paper reports that average annual bulk deposition of nitrogen increased by 8 kg of nitrogen per hectare from the 1980s to the 2000s. Ammonium is the dominant form of nitrogen in bulk deposition, whereas the rate of increase is largest for nitrate deposition. Nitrogen deposition has also increased plant foliar nitrogen concentrations in semi-natural ecosystems and has elevated crop nitrogen uptake in long-term unfertilized croplands. China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen1,2. These emissions result in the deposition of atmospheric nitrogen (N) in terrestrial and aquatic ecosystems, with implications for human and ecosystem health, greenhouse gas balances and biological diversity1,3,4,5. However, information on the magnitude and environmental impact of N deposition in China is limited. Here we use nationwide data sets on bulk N deposition, plant foliar N and crop N uptake (from long-term unfertilized soils) to evaluate N deposition dynamics and their effect on ecosystems across China between 1980 and 2010. We find that the average annual bulk deposition of N increased by approximately 8 kilograms of nitrogen per hectare (P

Air pollution has become one of the main environmental concerns in China since the 1980s due to China's rapid economic growth and resultant pollution. However, it is difficult to directly evaluate the anthropogenic contribution to air pollution in China. The 2008 Olympic Games in Beijing provided a unique opportunity for testing the contribution of anthropogenic pollution because of the clean-up controls on air quality in Beijing enforced over the period of the Games. In this case study, we monitored the concentrations of major air pollutants before, during, and after the Olympics at a suburban site in Beijing. Atmospheric concentrations of PM10, PM2.5, NH3, NO2, SO2, and the particulate ions NH4+, NO3-, SO4(2-) Ca2+, Mg2+, and K+ all decreased during the Olympic period because of strict emission controls, compared with the same period from 2005 to 2007. For example, the average PM10 concentration (61 microg m(-3)) during the Olympics was only 37% of that (166 microg m(-3)) in the same month (August) from 2005 to 2007. However, just 1 mo and 1 yr after the Games had ended, mean concentrations of these pollutants had increased significantly again. This rapid "recovery' of air pollutant concentrations after the Olympics suggests that China needs to implement long-lasting decreases in its air pollution in Beijing and other major cities.

[1] TSP and PM2.5 aerosol particles were synchronously sampled at six sites along the transport pathway of dust storms from desert regions to coastal areas in the spring of 2004 to investigate the regional characteristics of Asian dust and its impact on aerosol chemistry over northern China. Factor analysis of daily PM10 concentrations in 17 cities showed that northern China can be basically divided into five regions: (1) Northern Dust Region, (2) Northeastern Dust Region, (3) Western Dust Region, (4) Inland Passing Region, and (5) Coastal Region. Northern Dust Region was characterized by a high content of Ca. Northeastern Dust Region was a relatively clean area with a low concentration of pollutants and secondary ions in comparison to other regions. Inland Passing Region and Coastal Region showed high concentrations of anthropogenic pollutants. The impact of Asian dust on aerosol chemistry decreased in the order Yulin/Duolun > Beijing > Qingdao/Shanghai as transport distance increased. The ratio of Ca/Al, which showed significant differences in different regions over northern China, is suggested to be a tracer to identify the sources of dust storms. Asian dust either mixes pollutants on the pathway and carries them to the downwind regions or dilutes the pollutants over northern China, which affects the aerosol composition more in coarse particles in those areas near source regions and more in fine particles in downwind areas. The ratio of NO3−/SO42− during dust storms was significantly reduced and the lowest generally appeared after the peak of dust. Our results showed that Asian dust plays a critical role in buffering the acidity of aerosols over northern China by a potential increase of ∼1 unit pH for the aerosol particles in spring.

Reducing atmospheric ammonia (NH3) emissions is critical to mitigating poor air quality. However, the contributions of major agricultural and non-agricultural source emissions to NH3 at receptor sites remain uncertain in many regions, hindering the assessment and implementation of effective NH3 reduction strategies. This study conducted simultaneous measurements of the monthly concentrations and stable nitrogen isotopes of NHx (gaseous NH3 plus particulate NH4+) at 16 sites across China. Ambient NHx concentrations averaged 21.7 ± 19.6 μg m–3 at rural sites, slightly higher than those at urban (19.2 ± 6.0 μg m–3) and three times of those at background (7.0 ± 6.9 μg m–3) sites. Based on revised δ15N values of the initial NH3, source apportionment results indicated that non-agricultural sources (traffic and waste) and agricultural sources (fertilizer and livestock) contributed 54 and 46% to NH3 at urban sites, 51 and 49% at rural sites, and 61 and 39% at background sites, respectively. Non-agricultural sources contributed more to NH3 at rural and background sites in cold than warm seasons, arising from traffic and waste, but were similar across seasons at urban sites. We concluded that non-agricultural sources need to be addressed when reducing ambient NH3 across China, even in rural regions.

Ammonia (NH3) plays a critical role in atmospheric chemistry and can exacerbate haze formation. Agricultural emissions have been known as a primary source of global atmospheric NH3. However, with accelerating urbanization and optimized agricultural production, the dominance of agricultural emissions has become less clear. We investigated the contributions of nonagricultural and agricultural sources to atmospheric NH3 based on measurements of NH3 isotopes at nine sites in Quzhou County, a typical agricultural county in the North China Plain. We found that Quzhou had extremely high NH3 concentrations (annual average across all sites of 40.3 +/- 3.3 mu g m-3). We compared the sources of seasonal NH3 contributions in rural and urban areas through 15N-stable isotope analyses, which provides new insights into NH3 sources compared with the traditional emission inventories. In rural areas, agricultural sources (fertilizer application and livestock production) make significant contributions (56 +/- 3%) to NH3 emissions in the winter, whereas there were larger contributions of nonagricultural sources [fossil fuel, waste, and biomass burning (56 +/- 2%)] relative to agricultural sources in urban areas. More effective strategies are still needed for better manure management and vegetable/fruit production in the winter and for controlling nonagricultural sources, even in counties dominated by agriculture.

Short Communication - no abstract

China has experienced a dramatic change in atmospheric reactive nitrogen (Nr) emissions over the past four decades. However, it remains unclear how nitrogen (N) deposition has responded to increases and/or decreases in Nr emissions. This study quantitatively assesses temporal and spatial variations in measurements of bulk and calculated dry N deposition in China from 1980 to 2018. A long-term database (1980–2018) shows that bulk N deposition peaked in around 2000, and had declined by 45% by 2016–2018. Recent bulk and dry N deposition (based on monitoring from 2011 to 2018) decreased from 2011 to 2018, with current average values of 19.4 ± 0.8 and 20.6 ± 0.4 kg N ha−1 yr−1, respectively. Oxidized N deposition, especially dry deposition, decreased after 2010 due to NOx emission controls. In contrast, reduced N deposition was approximately constant, with reductions in bulk NH4+-N deposition offset by a continuous increase in dry NH3 deposition. Elevated NH3 concentrations were found at nationwide monitoring sites even at urban sites, suggesting a strong influence of both agricultural and non-agricultural sources. Current emission controls are reducing Nr emissions and deposition but further mitigation measures are needed, especially of NH3, built on broader regional emission control strategies.