FABIO · Fertilization effect of Aerosols on earth BIOmass

Fertilization effect of Aerosols on earth BIOmass

Within this two-years project, the researcher, Rong Wang, studied the abondances of nutriments in the form of phosphorus (P) and iron (Fe) in the atmosphere and their influence on the productivity of the ocean. Furthermore , the amounts and the contribution of anthropogenic aerosol deposition and its effect on carbon fluxes was analyzed. 1) Before the project, the estimated amount of P deposited over the globe exceeded the estimated emissions. The researcher worked on a better estimate of the combustion-derived emissions of P into the atmosphere. All P sources to the atmosphere (3.5 Tg P yr-1, 90% confidence from 0.9 to 7.8) translate to a deposition sink of 2.7 Tg P yr-1 over land and 0.8 Tg P yr-1 over the oceans. P deposition rates observed at a set of global measurement stations can be well captured by the model, indicating a near balance of the budget. 2) The sources of Fe from the combustion of fossil fuels and biomass were refined by accounting for the Fe contents in fuel and the partitioning of Fe during combustion. The emissions of Fe from mineral sources were estimated using the latest soil mineralogical database. As a result, the total Fe emissions from combustion averaged for 1960-2007 were estimated to be 5.3 Tg yr-1 (90% confidence of 2.3 to 12.1). The higher than previously estimated Fe from coal combustion implies a larger anthropogenic input of soluble Fe to the northern Atlantic and northern Pacific Oceans. 3) Satellite data suggest oceanic productivity is reduced due to global warming. The researcher simulated the response of oceanic productivity to aerosols deposition under varying climate from 1850 to 2010. There is a positive response of observed chlorophyll to deposition of anthropogenic aerosols. The results suggest that anthropogenic aerosols can reduce the sensitivity of oceanic productivity to warming by 10% in the global stratified oceans during 1948-2007. It implies that the inevitable reduction of aerosol emissions under higher air-quality standards in the future might accelerate the decline of oceanic productivity per unit warming. 4) Fertilizing effects of aerosols have been recognized as one of factors contributing to the terrestrial carbon sink. Availability of N and P is predicted to be a key factor limiting the forest productivity and carbon cycle. However, long-term effects of N and P deposition on forest carbon cycle remains poorly understood. The researcher has estimated global atmospheric deposition of N and P from 1850 to 2100 based on a state-of-the-art modeling of atmospheric chemistry of N and the sources of P. It shows that the biogeochemical effects of anthropogenic N and P deposition in forests amount to a global carbon sink of 0.08 Pg C yr-1, with a 90% confidence interval of 0.04-0.14 Pg C yr-1.

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