Understanding Environmental Change: Matter Cycling and Biogeochemical Cycles

1. Environmental Change (cont’d); Matter Cycling • ENST1001A, Week 6 • 14 October, 2011 • New readings: Textbook Chapter 4

2. Catching up: leftovers from last lecture(slides deleted since they’re in the files from week 4)

3. Matter (Chapter 4) • has mass • takes up space • “what things are made of” • elements, atoms, molecules • law of conservation of matter

4. Biogeochemical cycles • matter moving through the ecosphere • recall: energy flows; matter moving too • of all the naturally occurring chemical elements, about 30 are required for life • nutrients (macro- and micro-) • cycled continuously through ecosphere

5. Figure 4.1 Generalized model of biogeochemical cycle

6. Some really key cycles: • nitrogen • phosphorus • sulphur • carbon • water

7. Phosphorus (P) See text Figure 4.2

8. Sulphur See text fig 4.3

9. Nitrogen See text fig 4.4

10. C See text fig 4.7

11. See text fig 4.6

12. Hydrological Cycle • water also necessary for life • many unique properties • common in all three phases • high molecular attraction --> tension • high heat capacity • universal solvent • density: solid LESS dense

13. See Text Figure 4.8

14. Water availability • very unequal distribution on Earth • varying availability • Canada relatively rich, although most is ice • regionally large potential deficits • large demand from southern neighbours

15. Available Water • easiest to access/use: • surface freshwater • Groundwater • See text Figure 4.9

16. Precipitation • also highly variable • regional patterns (see Figure 4.10) -> why?

17. Air pressure & winds • need to bring back energy for a minute • energy + air -> air masses, winds

18. Convection systems • cool air will descend, and will flow towards areas of lower pressure • Precipitation often occurs in low pressure zones • as warm air rises, it cools, and can become supersaturated, resulting in precipitation

19. Implications... • strong tendency of air movement -> global air circulation patterns • strong influence on climate • combines with processes that govern water cycle • -> strong influence on other processes, soil formation, plant growth, ... (recall last week)

20. Back to water... • of course, these air masses also carry water • evaporation • air masses move • precipitation

21. Clouds • air can get supersaturated = too much water in vapour form -> condensation • condensation nuclei -> droplets • at first, droplets too small to fall; large numbers of droplets or ice crystals -> clouds • kept up by upward movements of air

22. Remote sensing of clouds... • satellites have “long” been used to study weather and climate • important tool to monitor development and track of storms, fronts, ...

23. Which brings us back to... • soils • vegetation

24. Humans and BGC Cycles • “Some of the most notable environmental crises today result from humans disrupting the natural flow of biogeochemical cycles” • discuss

25. Examples • Eutrophication (text Figure 4.13) • acid deposition (text Figures 4.15-4.16, 4.18) • greenhouse gases (TBC)