Ammonia (NH3) is the predominant alkaline gas in the atmosphere contributing to formation of fine particles—a leading environmental cause of increased morbidity and mortality worldwide. Prior findings suggest that NH3 in the urban atmosphere derives from a complex mixture of agricultural (mainly livestock production and fertilizer application) and nonagricultural (e.g., urban waste, fossil fuel-related emissions) sources; however, a citywide holistic assessment is hitherto lacking. Here we show that NH3 from nonagricultural sources rivals agricultural NH3 source contributions in the Shanghai urban atmosphere. We base our conclusion on four independent approaches: (i) a full-year operation of a passive NH3 monitoring network at 14 locations covering urban, suburban, and rural landscapes; (ii) model-measurement comparison of hourly NH3 concentrations at a pair of urban and rural supersites; (iii) source-specific NH3 measurements from emission sources; and (iv) localized isotopic signatures of NH3 sources in...

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Assessing Contributions of Agricultural and Nonagricultural Emissions to Atmospheric Ammonia in a Chinese Megacity

Responses of forest ecosystems to increasing N deposition in China: A critical review.

Urbanization alters nitrogen (N) cycling, but the spatiotemporal distribution and impact of these alterations on ecosystems are not well-quantified. We measured atmospheric inorganic N inputs and soil leaching losses along an urbanization gradient from Boston, MA to Harvard Forest in Petersham, MA. Atmospheric N inputs at urban sites (12.3 ± 1.5 kg N ha−1 year−1) were significantly greater than non-urban (5.7 ± 0.5 kg N ha−1 year−1) sites with NH4+ (median value of 77 ± 4 %) contributing thrice as much as NO3−. Proximity to urban core correlated positively with NH4+ (R2 = 0.57, p = 0.02) and total inorganic N inputs (R2 = 0.61, p = 0.01); on-road CO2 emissions correlated positively with NO3− inputs (R2 = 0.74, p = 0.003). Inorganic N leaching rates correlated positively with atmospheric N input rates (R2 = 0.61, p = 0.01), but did not differ significantly between urban and non-urban sites (p > 0.05). Our empirical measurements of atmospheric N inputs are greater for urban areas and less for rural areas compared to modeled regional estimates of N deposition. Five of the nine sites had NO3− leached that came almost entirely from nitrification, indicating that the NO3− in leachate came from biological processes rather than directly passing through the soil. A significant proportion (17–100 %) of NO3− leached from the other four sites came directly from the atmosphere. Surprisingly, the four sites where atmospheric sources made up the largest proportion of leachate NO3− also had relatively low N leaching rates, suggesting that atmospheric N inputs added to terrestrial ecosystems can move to multiple sinks and losses simultaneously, rather than being lost via leaching only after abiotic and biotic sinks have become saturated. This study improves our understanding of atmospheric N deposition and leaching in urban ecosystems, and highlights the need to incorporate urbanization effects in N deposition models.

Atmospheric nitrogen inputs and losses along an urbanization gradient from Boston to Harvard Forest, MA

The transport sector is one of the main sources air pollutants. Different exhaust after-treatment systems have been implemented over the years to control the emissions of criteria pollutants. However, while reducing the emissions of the target compounds these systems can lead to the emissions of other pollutants and/or greenhouse gases such as NH3 or N2O. Following the implementation of the Real Driving Emissions (RDE) test procedure in the EU, vehicles have been equipped with more complex after-treatment configurations. The impact that these technologies may have on the emissions of non-regulated pollutants during real-world driving have not been evaluated until now. In the current study we present the on-road emissions of a series of non-regulated pollutants, including NH3, N2O, CH4 and HCHO, measured with a portable FTIR from a series of Euro 6d, Euro 6c and Euro 6d-TEMP, gasoline diesel and compressed natural gas (CNG) vehicles during real-world testing. The obtained results show that it is possible to measure N2O, NH3, CH4 and HCHO during on-road operation. The results also highlight the importance of the measurement of the emissions of these pollutants during real-world driving, as the emissions of NH3 (a particulate matter precursor) and those of N2O and CH4 (green-house gases) can be high from some vehicle technologies. NH3 emissions were up to 49 mg/km for gasoline passenger cars, up to 69 mg/km for the CNG light-commercial vehicle and up to 17 mg/km a diesel passenger car equipped with a selective catalytic reduction system (SCR). On the other hand, N2O and CH4 emissions accounted for up to 9.8 g CO2 eqv/km for a diesel passenger car equipped with a combination of diesel oxidation catalysts (DOC), lean NOx traps (LNT), SCR and possibly an ammonia slip catalyst ASC.

Regulated and Non-Regulated Emissions from Euro 6 Diesel, Gasoline and CNG Vehicles under Real-World Driving Conditions

https://www.fs.fed.us/psw/publications/fenn/psw_2019_fenn003_walker.pdf

Toward the improvement of total nitrogen deposition budgets in the United States.

https://www.fs.fed.us/psw/publications/fenn/psw_2018_fenn001.pdf

Kenneth Hanks

Papers

On-road emissions of ammonia: An underappreciated source of atmospheric nitrogen deposition.