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Lonjakan Nitrogen Oksida Di Asia Timur & Amerika Selatan

Akhir-akhir ini, manusia lebih banyak melepas nitrogen-oksida (Nitrous oxide/ N2O), suatu gas rumah-kaca, ke atmosfer daripada perkiraan sebelumnya; N2O termasuk satu dari zat perusak ozon stratosfer utama. Begitu hasil dan kesimpulan riset 12 ahli asal 7 negara yang dirilis oleh jurnal Nature Climate Change edisi November 2019. (Thompson R, Lassaletta L, Patra P, Wilson C, Wells K, Gressent A, Koffi E, Chipperfield M, Winiwarter W, et al.,“Acceleration of global N2O emissions seen from two decades of atmospheric inversion”, Nature Climate Change, 2019).

“This new publication demonstrates both how we can solve a problem of growing greenhouse gas emissions and how current efforts are falling short in some regions of the world. These emissions come primarily from using fertilizers to grow food and increasing livestock herds, but we've learned how to produce more food with less nitrous oxide emission,” papar co-author Profesor Eric Davidson asal University of Maryland Center for Environmental Science di Amerika Serikat. (University of Maryland Center for Environmental Science, 18/11/2019).

N2O—suatu gas rumah kaca--merupakan greenhouse gas (GHG / greenhouse effect) sangat penting ke-3 dan bahan perusak lapisan ozon stratosferik – selain methane dan CO2 (karbon-dioksida). (Thompson R., et al., 2019) Meskipun gas N2O juga lazim dipakai di bidang kedokteran (bahan obat disosiatif untuk trauma atau stres berat, pembiusan, dll), peroketan, otomotif, dan bahan peledak (Toni Samiaji, 2012:1).

Menurut hasil riset Thompson R. et al. (2019), praktek pertanian dan penggunaan pupuk-N (N-fertilizers) memicu lonjakan emisi NH2 ke atmosfer. Sejak paruhan abad 20, produksi pupuk-pupuk nitrogen (nitrogen fertilizers), pengembangan budi-daya tanaman berbasis nitrogen seperti semanggi (clover), alfalfa, lupin, dan kacang-kacangan, pembakaran fosil dan bahan bakar bio (biofuels), memicu lonjakan ketersediaan subtrat-subtrat nitrogen di lingkungan planet Bumi. (Science Daily, 18/11/2019)

“The increased nitrogen availability has made it possible to produce a lot more food. The downside is of course the environmental problems associated with it, such as rising N2O levels in the atmosphere,” papar  Rona Louise Thompson, ahli GHD dan spesies atmosfer lainnya yang berkaitan dengan iklim (climate), khususnya CO2, CH4, dan N2O asal NILU-Norwegian Institute for Air Research. (University of Maryland Center for Environmental Science, 18/11/2019).

Proyek riset itu melibatkan 12 ahli dari 7 negara yaitu (1) R. L. Thompson asal Norsk Institutt for Luftforskning, Kjeller, Norwegia; (2) Luis Lassaletta PhD, asal CEIGRAM-Agricultural Production, Universidad Politécnica de Madrid, Madrid di Spanyol; (3) Prabir K. Patra asal Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama Institute for Earth Sciences (YES) Research Institute for Global Change, JAMSTEC, Yokohama, Jepang;

(4) C. Wilson  asal National Centre for Earth Observation, University of Leeds, Leeds, Inggris; School of Earth and Environment, University of Leeds, Leeds, Inggris; (5) K. C.Wells  asal Department of Soil, Water, and Climate, University of Minnesota, Minneapolis, MN, Amerika Serikat;

(6) A. Gressent asal  Massachusetts Institute of Technology, Cambridge, MA, Amerika Serikat; (7) E. N. Koffi asal European Commission Joint Research Centre, Ispra, Italia; (8) M.P. Chipperfield asal National Centre for Earth Observation, University of Leeds, Leeds, Inggris; School of Earth and Environment, University of Leeds, Leeds, Inggris; (9) W. Winimarter asal International Institute for Applied Systems Analysis, Laxenburg, Austria; University of Zielona Góra, Zielona Góra, Polandia;

(10) Profesor E.A. Davidson asal University of Maryland Center for Environmental Science, Cambridge, MD, Amerika Serikat; (11) H. Tian asal International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, Inggris: (12) J. G. Canadell asal Global Carbon Project, CSIRO Oceans and Atmosphere, Canberra, Australian Capital Territory, Australia.

Tim ahli itu membuat perkiraan tentang emisi N2O yang ditentukan dari tiga kerangka-kerja inversi atmosfer di planet Bumi selama tahun 1998-2016. Hasilnya, tim ahli itu menemukan bahwa emisi N2O di seluruh dunia naik tajam (substansial) sejak 2009 hingga pada tingkat yang lebih cepat dari perkiraan faktor emisi karbon dari Intergovernmental Panel on Climate Change (IPCC).

“We see that the N2O emissions have increased considerably during the past two decades, but especially from 2009 onwards. Our estimates show that the emission of N2O has increased faster over the last decade than estimated by the Intergovernmental Panel on Climate Change (IPCC) emission factor approach,” ungkap  Rona L. Thompson asal NILU-Norwegian Institute for Air Research. (University of Maryland Center for Environmental Science, 18/11/2019).

Zona sumber emisi N2O terbesar berasal dari wilayah Asia Timur dan Amerika Selatan. Berdasarkan emisi berbasis inversi itu, tim ahli itu memperkirakan faktor emisi global sekitar 2,3 ± 0,6%  atau lebih besar dari perkiraan Intergovernmental Panel on Climate Change (IPCC) Tier-1 untuk total emisi langsung dan tidak langsung sebesar 1,375%. Faktor emisi lebih besar dan lonjakan akselerasi emisi dari inversi-inversi itu menunjukkan bahwa respons emisi N2O mungkin bukan linier terhadap skala kawasan dan global dengan tingkat input N yang tinggi.   

“In Europe and North America, we have succeeded in decreasing growth in nitrous oxide emissions, an important contributor to climate change and stratospheric ozone depletion. Unfortunately, the same can't be said for Asia and South America, where fertilizer use, intensification of livestock production, and the resulting nitrous oxide emissions are growing rapidly. The good news is that this problem can be solved, but the less good news is that it will take a global effort, and we are far from there yet,” ungkap co-author Eric Davidson asal University of Maryland Center for Environmental Science di Amerika Serikat. (University of Maryland Center for Environmental Science, 18/11/2019). 

 

Oleh: Servas Pandur