Global sulfur cycle: emissions, sulfate aerosol and deposition
Sulfur reaches the air as dimethyl sulfide from ocean plankton, SO2 from volcanoes and SO2 from burning coal and oil. Within days it oxidises to sulfuric acid and sulfate aerosol, which seeds clouds and reflects sunlight, then falls out in rain onto land and sea.
Boundary: where this process starts
Starts with: Ocean plankton release about 28 Tg of sulfur a year to the air as dimethyl sulfide (range 18-34)
Boundary: where it ends
Ends after: Sulfuric acid travels hundreds of kilometres and falls as acid rain
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
- Participant
- Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
- Resource
- Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
- Step
- One thing that happens in a process. Every step has at least one participant and carries evidence.
- Decision fork
- A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
- Loop
- A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
- Size of impact
- Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
- Evidence
- The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
- Boundary
- Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
- Subprocess
- A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
- Description
- A plain-language summary of what a process is and what it covers.
- Hypothesis
- A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.
Every step, with its evidence
The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.
Ocean plankton release about 28 Tg of sulfur a year to the air as dimethyl sulfide (range 18-34)
Evidence (1) · added by Corbel
- Lana et al. 2011, An updated climatology of surface dimethylsulfide concentrations and emission fluxes in the global ocean, Global Biogeochem. Cycles 25, https://doi.org/10.1029/2010GB003850 (https://ueaeprints.uea.ac.uk/id/eprint/24899/): About 28.1 (17.6-34.4) Tg S per year is transferred from the ocean to the atmosphere as DMS. (confidence 0.8)
Over 90 persistently degassing volcanoes emit about 23 Tg of SO2 a year (2005-2015)
Evidence (1) · added by Corbel
- Carn et al. 2017, A decade of global volcanic SO2 emissions measured from space, Sci. Rep. 7:44095, https://doi.org/10.1038/srep44095: Passive volcanic degassing emits about 23 +/- 2 Tg SO2 per year (2005-2015) from over 90 volcanoes; eruptive fluxes are typically an order of magnitude smaller. (confidence 0.85)
Burning coal and oil is the largest SO2 source; human emissions peaked in the early 1970s, fell to 2000, then rose with China and shipping
Evidence (2) · added by Corbel
- Smith et al. 2011, Anthropogenic sulfur dioxide emissions: 1850-2005, Atmos. Chem. Phys. 11:1101-1116, https://doi.org/10.5194/acp-11-1101-2011: Global anthropogenic SO2 emissions peaked in the early 1970s, decreased until 2000, and increased again in 2000-2005 because of China, international shipping and developing countries. (confidence 0.8)
- Royal Belgian Institute for Space Aeronomy, Sulphur dioxide (SO2) gas in the Earth's atmosphere, https://bira-iasb.be/en/encyclopedia/sulphur-dioxide-so2-gas-earths-atmosphere: Coal burning is the largest man-made source, about 50% of annual emissions, with oil burning 25-30%. (confidence 0.7)
SO2 lasts only a few days in the lower air, oxidising to sulfuric acid in the gas phase and inside cloud droplets
Evidence (1) · added by Corbel
- Royal Belgian Institute for Space Aeronomy, Sulphur dioxide (SO2) gas in the Earth's atmosphere, https://bira-iasb.be/en/encyclopedia/sulphur-dioxide-so2-gas-earths-atmosphere: Tropospheric SO2 lifetime is a few days; it forms sulfuric acid in the gas phase and by oxidation in water droplets; stratospheric lifetime is several weeks. (confidence 0.8)
Sulfuric acid travels hundreds of kilometres and falls as acid rain
Evidence (1) · added by Corbel
- Royal Belgian Institute for Space Aeronomy, Sulphur dioxide (SO2) gas in the Earth's atmosphere, https://bira-iasb.be/en/encyclopedia/sulphur-dioxide-so2-gas-earths-atmosphere: The acidic pollution can be carried hundreds of kilometres by wind and deposited as acid rain. (confidence 0.8)