IRN SOOT-SEA : Impact of black carbon in South East Asia

The estimated total flux of BC to the ocean via atmospheric deposition and fluvial transport is equivalent to the estimated emission rate. Considering that most BC ends up in the ocean, it is important to understand how this material impacts marine systems. Because BC particles are highly porous and surface-active, with a high density, they can sorb dissolved compounds, increase aggregation processes and ballast sinking particulate organic matter. Because they bring nutrients and contaminants to the surface ocean, and modify the structuring of the environment at the microscale, BC may alter phyto- and bacterio-plankton composition and activity. As a result, BC may alter the efficiency of the biological carbon pump, and lead to either a positive or a negative feedback on the atmospheric concentration of CO2. In addition, BC can sorb contaminants in seawater and either introduce them into the food chain, hence alter food security, or export them to the seafloor, hence cleanse the water column. In order to determine the actual impacts of BC, it is necessary to obtain accurate emission and deposition rates. At present, there are still large uncertainties related to the magnitude of the impact of atmospheric BC due to difficulties in obtaining accurate emission inventories, and in particular in South East Asia (SEA). For example, current climate models systematically underrate aerosol absorption by 3-fold when compared to observations, which is attributed to the underestimation of BC emissions. Since estimates of the atmospheric flux of BC to the ocean are derived from emission estimates, they may be underestimated as well. In order to determine the effects of BC on marine resources and biogeochemistry, it is also necessary to understand how BC interacts with biological/chemical/physical marine processes. Owing to its short residence time in the atmosphere, atmospheric BC is currently considered a short-lived climate/health forcer. In contrast, because BC in the ocean will last for millennia, and its impacts on carbon cycling in the ocean can have long-lasting feedbacks on climate and marine biogeochemistry, marine BC may act as a long-lived climate/ecosystem forcer.

SOOT-SEA seeks to stimulate research, innovation, observation and capacity-building activities related to the impacts of BC on climate, health and ecosystem, taking into account for the first time its marine dimension, by increasing interactions between scientists from the South and the North. Overall, SOOT-SEA will represent a key contribution to the future deployment of the BC Regional Observatory (FFEM-GIZ project: Strengthening Black Carbon monitoring and regulation in South-East Asia to impact air and marine pollution, climate change, health and ecosystems).