Close to 50% of phosphorus emitted to the atmosphere is a result of human activities

According to the study in which CREAF participated, China contributes 43% of this amount. For decades it had been thought that human activities were responsible for only around 5% of atmospherically-circulating phosphorus. More phosphorus in the air means more phosphors deposited on the ground. This can boost plant growth and the capacity to sequester atmospheric CO₂; for that reason human activities may be altering the phosphorus and carbon cycles to a degree which was previously unknown

Researchers of the IMBALANCE-P ERC Synergy Grant led by CREAF are working on the most realistic planetary atmospheric phosphorus budget done to date. Phosphorus is an essential nutrient for life and also plays a fundamental role in agriculture and world food security. Phosphorus is found in mineral reserves and in living beings, and despite being much less known, phosphorus is also in the atmosphere. Before the industrial era phosphorus was only naturally emitted to the atmosphere due to volcanic explosions, emissions of biogenic aerosols, and forest fires, in addition to being transported in continental dust and in marine salt. Now, the article published in Nature Geoscience has revealed the impact that human activities have had and are having on the cycle of phosphorus in the atmosphere. The team of international researchers publishing this information has shown that close to 50% of phosphorus currently emitted to the atmosphere is the result of human activities, basically from the burning of coal and biomass, whereas to date it was thought that this number was closer to 5%.

According to the results, the total quantity of phosphorus emitted to the atmosphere has increased 30% in the previous fifty years as a result of a doubling of emissions produced by human beings.

Currently, 43% of anthropogenic phosphorus emissions to the atmosphere are from China, while European emissions have continued to decline year after year.

To carry out the study, the researchers created an inventory of natural and anthropic sources in 222 countries and territories for the period of 1960-2007. They used samples of coal from 13 different countries and samples of biomass of the 11 tree species and 9 crops most utilized as combustibles.

Combustion emits CO₂ to the atmosphere, but phosphorus helps store it 

Phosphorus is a limiting nutrient for plant growth. A lot of phosphorus makes a soil fertile, helping plants grow and store more atmospheric CO₂, reducing the greenhouse effect.“The results of this study show that the phosphorus cycle is strongly perturbed, more than we thought.

This opens the possibility that there are many ecosystems which are being fertilized due to atmospheric phosphorus deposited in the ocean and above all on the ground, especially in tropical and subtropical forests of Asia and Africa.

If the ecosystems are fertilized and their capacities for growth and carbon storage become greater, that means that atmospheric phosphorus is modifying the carbon cycle more than we thought up to now,” comments Josep Peñuelas, professor of the Spanish Council for Scientific Research (CSIC), who carries out research at CREAF.

The opposite could be happening in Europe or in North America, where the rhythm of coal and biomass burning has slowed in recent years. While we shouldn’t forget that this reduction in the use of coal has significantly improved air quality, phosphorus emission rates have also declined, and now the soil is not receiving the same quantity of phosphorus as it did in the past, and forest growth could be slowed for this reason.

“The policies designed to reduce the emissions of aerosols coming from fossil fuel burning represent a clear win-win option for improving air quality, while also reducing warming caused by the CO₂ produced in combustion. However, this study suggests to us that we should also take into account the phosphorus which we will stop emitting when we evaluate the capacity of terrestrial and marine ecosystems to store CO₂,” concludes Professor Peñuelas.  

Article:

Wang, R. Balkanski, Y. Boucher, O. Ciais, P. Peñuelas, J. Tao, S. (2014) Significant contribution of combustion-related emissions to the atmospheric phosphorus budget Nature Geoscience