Environmental Chemistry Feb. 20, 2018

Origins Create the universe Create the elements Create the Earth Form the atmosphere and oceans

Create the Earth Accretion – gravity-driven process by which smaller objects collide and combine to form a larger object Interior heats and exterior cools. Molten interior results in movement, e.g., plate tectonics, which allows substances to segregate based on properties What characteristics differentiate substances (both elements and compounds)? Density Volatility/Phase Solubility Organic/Inorganic Mineral?

‘Spheres’ of the Earth system

Box models and steady-state 𝑑𝑉 𝑑𝑡 =𝐼𝑛𝑓𝑙𝑜𝑤+𝑂𝑢𝑡𝑓𝑙𝑜𝑤 At steady state: 𝑑𝑉 𝑑𝑡 =𝐼𝑛𝑓𝑙𝑜𝑤+𝑂𝑢𝑡𝑓𝑙𝑜𝑤=0 𝐼𝑛𝑓𝑙𝑜𝑤=−𝑂𝑢𝑡𝑓𝑙𝑜𝑤

How did the spheres evolve? Two essential ingredients: Liquid water Atmosphere

Questions Has there always been liquid water? What are the sources of water? Has water been gained/lost over earth history?

Water reservoirs Little loss to space For liquid H2O, T must be 0˚C - 100 ˚C Figure 09-05 How to Build a Habitable Planet Copyright © Princeton University Press 2012

Energy balance

What maintains temperature? Feedbacks on CO2 concentration Weathering 3 H2O + 2 CO2 + CaSiO3  Ca2+ + 2 HCO3- + H4SiO4 Precipitation Ca2+ + 2 HCO3-  CaCO3 + H2O + CO2 (foraminifera) H4SiO4  SiO2 + 2 H2O (diatoms) Mantle CaCO3 + SiO2  CaSiO3 + CO2 wollastonite

Carbonate-silicate cycle Timescale = 105 – 107 yrs J. F. Kasting, Science Spectra, 1995

Feedback on CO2 Figure 09-11 How to Build a Habitable Planet Copyright © Princeton University Press 2012