当前世界环境

Dear Readers

The present issue of the Current World Environment is presented before you. I thank the authors, reviewers and the journal secretariat for timely publishing the issue. This issue includes research papers from diversified subareas of environment as given in the table of content. This time we have included `Editorial Contributions’ from our Editorial Board members. The theme of the Editorial of this issue is Reactive Nitrogen as detailed below-

The food and energy demand of the global population has resulted in the rapid increase in the levels of reactive nitrogen species (Nr) such as NH₃, NOx, NO₃^-and NH₄⁺etc. in the atmosphere across the globe.These compounds affect air quality, human health, climate, ozone levels, etc. NO₂at high levels may be responsible for almost 2 million deaths per year due its indoor pollution effect¹.NO₂forms smog with excessive O₃and organic compounds such as aldehydes, ketones and peroxyacyl nitrate (PAN) etc.The excess concentrations of the nitrogenous compounds have adverse impacts on water bodies causing eutrofication problem. Nr species are contributed by both natural as well as anthropogenic activities.Apart from natural sources, anthropogenic sources such as fertilizer production, fertilizer application, fossil fuel combustion and sanitation etc. are the major contributors of the Nr species. A comprehensive Nitrogen Assessment for India has been published by Abrol and co-workers.²

Recent research highlights that the anthropogenic N fixation from biological nitrogen fixation (BNF), fertilizers and combustion is estimated as 220 Mt per year against65 Mt asthe natural N fixation from BNF and lightning.³This indicates that the extent of human perturbation in N cycle.⁴After north America and Europe,Asian region has the third highest N deposition rates.⁵The globalanthropogenic Nr budgets have been calculated by Denteneret al., using a multi-model approach.⁶Indian consumption of nitrogenous fertilizer has touched 15 million tons in 2010-11 against 1 million ton in 1960s.⁷Indo-Gangetic region is considered as a hot spot of Nr abundance.⁸-⁹In India, among N-NH₃, N-NH₄and N-NO₃species, gaseous ammonia contributes highest N in the air.¹⁰Megacities are huge contributors to the reactive nitrogen. NO₂levels are seen growing due to their emissions from fossil fuel combustion in thermal power plants, industries and automobiles etc.¹¹NO2 is a significant contributor to the poor air quality of Delhi and other megacities. NO₂and NO₃^-are also responsible for acid rain.¹²The number of vehicles and population in all the mega cities has risen exponentially. Probably, due to this reason, a remarkable increase in NH₄and NO₃fluxes has been reported at Delhi since 1994.¹³

In the agriculture, most of the NH₃is emitted during fertilizing stage. The urea which is a major fertilizer is the main source of higher NH₃during fertilizing stage. Urea (NH₂CONH₂) on dissociation results in NH₃emission. Higher temperature and alkaline dust aerosols adds to the dominance of NH₃in gaseous phase in contrast with the acidified regions.¹⁴The ratio of NH₃/NH₄remains higher in Indian region (alkaline aerosols) as compared to the acidified regions (acidic aerosols). There is a need to carry out studies on NH₃emissions during different stages of agriculture which can be of help in efficient N management. Similarly, agriculture activity has been considered a major source of N₂O. Paddy cultivation is one among major contributors of N₂O emissions.¹⁵Livestock is another sector responsible for Nr contributions. N₂O排放和从不同的年增长率livestock categories have been reported by Anejaet al.,¹⁶However, the large discrepancies in the Nr budget from livestocks need to be reduced.

Nr物种通过干态和湿沉积deposition processes. The coarser particles are deposited through dustfall which is very common in dusty regions.¹⁷Wet deposition of Nr species has been reported more extensively as compared to the dry deposition of Nr species.¹⁸Sensitive ecosystems such as Himalayan region and Western Ghats are highly affected by the deposition of NO₃and NH₄.^19-20Deposition of NO₃and NH₄contributed by both local as well as transported sources has been reported by Kumaret al.,²¹Emission vs deposition budgets of major Nr species have been given by Kulshrestha.¹⁰

Recently, carbon cycle imbalance has been the focus of scientific community as well as policy makers. Global warming and climate change issues related research has added tremendous new knowledge about the sources, phases, chemical and physical characteristics of carbonaceous aerosols. Before it becomes second carbon, reactive nitrogen issue needs attention. There is great need to review our fertilizer and fuel policies now. A detailed overview of the south Asian scenario of reactive nitrogen and the suggested actions has been given by Naseem and Kulshrestha.²²It is worth mentioning here that under the UK Global Challenge Research Fund, the `GCRF South Asian Nitrogen Hub (SANH)’ project has been started which has 32 leading research organizations as partners. SANH is a mega project having all eight south Asian countries and the South Asia Co-operative Environment Programme (SACEP). There are several gaps in the nitrogen increaseestimatesand its impact assessment but hopefully, this SANH project will be able to provide suitable solutions which can help in effective global nitrogen management.

References

1. Wolfe, A. H., & Patz, J. A. (2002). Reactive nitrogen and human health: acute and long-term implications. Ambio:A journal of the human environment, 31(2), 120-125.
   CrossRef
2. Abrol, Y. P., Adhya, T. K., Aneja, V. P., Raghuram, N., Pathak, H., Kulshrestha, U., Sharma C. Singh, B. (Eds.). (2017). The Indian Nitrogen Assessment: Sources of Reactive Nitrogen, Environmental and Climate Effects, Management Options, and Policies.Elsevier.ISBN: 978-0-12-811836-8.
3. Sutton M, Drewer J, Moring A., Adhya T K et al. 2017. The Indian nitrogen challenge in a global perspective. In Abrol, Y. P., Adhya, T. K., Aneja, V. P., Raghuram, N., Pathak, H., Kulshrestha, U., Sharma C. Singh, B. (Eds.). (2017).Elsevier. ISBN: 978-0-12-811836-8. pp 9-28.
   CrossRef
4. Galloway, J.N., Townsend, A.R., Erisman, J.W., Bekunda, M, Cai ZC, Freney JR, Martinelli, L.A., Seitzinger SP, Sutton, M.A., 2008. Transformation of thenitrogen cycle: recent trends, questions, and potential solutions. Science 320, 889–892.
   CrossRef
5. Galloway, J.N., Cowling, E.B.,2002. Reactive nitrogen and the world: 200 years of change. Ambio 31, 64–71.
   CrossRef
6. Dentener, F.; Drevet, J.; Lamarque, J. F.; Bey, I.; Eickhout, B.; Fiore, A. M.; Hauglustaine, D.; Horowitz, L. W.; Krol, M.; Kulshrestha, U. C.; Lawrence, M.; Galy-Lacaux, C.; Rast, S.; Shindell, D.; Stevenson, D.; Van Noije, T.; Atherton, C.; Bell, N.; Bergman, D.; Butler, T.; Cofala, J.; Collins, B.; Doherty, R.; Ellingsen, K.; Galloway, J.; Gauss, M.; Montanaro, V.; Müller, J. F.; Pitari, G.; Rodriguez, J.; Sanderson, M.; Solmon, F.; Strahan, S.; Schultz, M.; Sudo, K.; Szopa, S.; Wild, O (2006). Nitrogen and sulfur deposition on regional and global scales: A multimodel evaluation. Global Biogeochem. Cycles, Vol. 20, No. 4, GB4003, 10.1029/2005GB002672.
   CrossRef
7. FAOSATAT: Food and Agriculture Organization o the United Nations. 2015. Food and Agriculture Database (Food, Agriculture Organ, UN, Rome).
8. Singh S. and Kulshrestha U.C. 2014. Rural versus urban gaseous inorganic reactive nitrogen in the Indo-Gangetic Plains (IGP) of India. 2014.Environmental Research Letters, 9, DOI: doi:10.1088/1748-9326/9/12/125004
   CrossRef
9. Tiwari R. and Kulshrestha U. 2019. Wintertime distribution and atmospheric interactions of reactive nitrogen species along the urban transect of Delhi – NCR. Atmospheric Environment, DOI: 10.1016/j.atmosenv.2019.04.00.
   CrossRef
10. Kulshrestha美国(2017年)。评估大气Emission and Deposition of Major Nr Species in Indian Region. In Abrol, Y. P., Adhya, T. K., Aneja, V. P., Raghuram, N., Pathak, H., Kulshrestha, U., ... & Singh, B. (Eds.). (2017). The Indian Nitrogen Assessment: Sources of Reactive Nitrogen, Environmental and Climate Effects, Management Options, and Policies.Elsevier.
    CrossRef
11. Sharma, S K, M Saxena, T Saud, S Korpole, TK Mandal. 2012. Measurement of NH3, NO, NO2 and related particulates at urban sites of Indo Gangetic Plain (IGP) of India.J Scientific & Industrial Research, 71, 360-362.
12. Kulshrestha, U. C., Kulshrestha, M. J., Satyanarayana, J., Reddy, L. A. K.,2014. Atmospheric Deposition of Reactive Nitrogen in India, (April). Nitrogen Deposition, Critical Loads and Biodiversity (Eds: M Sutton et al), pp 75–82 (Springer).
    CrossRef
13. Singh S., Kumar B., Gupta G.P., Kulshrestha U.C. 2014.Signatures of Increasing Energy Demand of Past Two Decades as Captured in Rain Water Composition and Airmass Trajectory Analysis at Delhi (India).Journal of Energy, Environment & Carbon Credits, 2014, 4(3), 43-61.
14. Singh S, Kulshrestha UC (2012) Abundance and distribution of gaseous ammonia and particulate ammonium at Delhi, India.Biogeosciences9:5023-5029.
    CrossRef
15. Adhya T K, Pathak H and Chhabra A. 2007. N fertilizers and gaseous N emissions from rice based cropping system. In Agricultural Nitrogen Use and Its Environmental Implications (Eds:Y. P. Abrol, Nandula Raghuram M S Sachdev), I K International Pvt. Ltd. New Delhi, pp 459-476.
16. Aneja V P, William H. Schlesinger, Jan Willem Erisman, Sailesh N. Behera, Mukesh Sharma, William Battye. 2012. Reactive nitrogen emissions from crop and livestock farming in India. Atmospheric Environment 47 (2012) 92-103.
    CrossRef
17. Mishra M. and Kulshrestha U. 2016. Chemical Characteristics and Deposition Fluxes of Dust-Carbon Mixed Coarse Aerosols at Three Sites of Delhi, NCR.J Atmospheric Chemistry, http://link.springer.com/article/10.1007/s10874-016-9349-1.
    CrossRef
18. Kulshrestha, U. C., Granat, L., Engardt, M., Rodhe, H., 2005. Review of precipitation monitoring studies in India — a search for regional patterns.Atmospheric Environment, 39, 7403–7419. http://doi.org/10.1016/j.atmosenv.2005.08.035
    CrossRef
19. Kulshrestha U. 2018. Threats to Himalayan Ecosystem due to Long Range Transport of Air Pollutants and Land Use Changes.当前世界环境, DOI: http://dx.doi.org/10.12944/CWE.14.1.01.
    CrossRef
20. Satyanarayana, J. Reddy, L.A.K., Kulshrestha, M.J. Rao, R.N. and Kulshrestha, U.C. (2010). Chemical composition of rain water and influence of airmass trajectories at a rural site in an ecological sensitive area of Western Ghats (India).J. Atmos. Chem., 66, 101-116.
    CrossRef
21. Kumar, B, Singh, S., Gupta, G. P., Lone, F. A., Kulshrestha, U. C., 2016. Long range transport and wet deposition fluxes of major chemical species in snow at Gulmarg in north western Himalayas (India).Aerosol and air quality research, 16: 606–617.
    CrossRef
22. Naseem M and Kulshrestha U. 2019. An Overview of Atmospheric Reactive Nitrogen Research: South Asian Perspective.当前世界环境, 14, 10-26.
    CrossRef