What was done
The authors describe and demonstrate how reactive nitrogen compounds, such as those found in synthetic fertilizers, may be acted upon by soil microbes to produce nitrites in both agricultural soils and the soils of forests and boreal regions; and they show how the photolysis of the nitrous acid (HONO) consequently found in these soils can produce up to ~30% of the atmosphere's total OH concentration.

What was learned
Su et al.'s findings explain the origin, size and diurnal variation of field observations that had previously suggested there was a large unknown source of HONO having the characteristics they identified.

What it means
The phenomenon elucidated by the ten scientists plays an important role in the atmosphere's photochemistry, which in turn plays a key role in the planet's energy balance, because OH radicals act as precursors of aerosols that can contribute to climate change by reflecting a portion of the incoming solar radiation from the sun back to space and thereby exerting a cooling influence on the planet. And, to quote the international team of researchers, "because of enhanced fertilizer use and soil acidification in developing countries (Guo et al., 2010), the release of HONO from soil nitrite might strongly increase in the course of global change, resulting in elevated OH concentrations and amplified oxidizing capacity of the lower troposphere," which would, of course, tend to impede the warming that helped to initiate the phenomenon, illustrating yet another of the "checks and balances" built into earth's amazingly complex climatic system, which has for eons maintained environmental conditions conducive to the continued existence of life upon its surface.

In further commentary on Su et al.'s findings, and in much the same vein, Kulmala and Petaja (2011) rhetorically ask: "What would happen if global HONO emissions from soil doubled within the next 25 years?" And in answer, they say it "could increase the atmosphere's ability to cleanse itself of volatile compounds such as methane," which is also a powerful greenhouse gas. And perhaps that is why atmospheric methane concentrations have risen at a much slower rate over the prior two decades than they had previously risen, as has been reported by a number of researchers, including Simpson et al. (2002), Dlugokencky et al. (2003), Khalil et al. (2007) and Schnell and Dlugokencky (2008).

References
Dlugokencky, E.J., Houweling, S., Bruhwiler, L., Masarie, K.A., Lang, P.M., Miller, J.B. and Tans, P.P. 2003. Atmospheric methane levels off: Temporary pause or a new steady-state? Geophysical Research Letters 30: 10.1029/2003GL018126.

Guo, J.H., Liu, X.J., Zhang, Y., Shen, J.L., Han, W.X., Zhang, W.F., Christie, P., Goulding, K.W.T., Vitousek, P.M. and Zhang, F.S. 2010. Significant acidification in Chinese croplands. Science 327: 1008-1010.

Khalil, M.A.K., Butenhoff, C.L. and Rasmussen, R.A. 2007. Atmospheric methane: Trends and cycles of sources and sinks. Environmental Science & Technology 10.1021/es061791t.

Kulmala, M. and Petaja, T. 2011. Soil nitrites influence atmospheric chemistry. Science 333: 1586-1587.

Schnell, R.C. and Dlugokencky, E. 2008. Methane. In: Levinson, D.H. and Lawrimore, J.H., Eds. State of the Climate in 2007. Special Supplement to the Bulletin of the American Meteorological Society 89: S27.

Simpson, I.J., Blake, D.R. and Rowland, F.S. 2002. Implications of the recent fluctuations in the growth rate of tropospheric methane. Geophysical Research Letters 29: 10.1029/2001GL014521.