Читать книгу Introduction to Nanoscience and Nanotechnology - Chris Binns - Страница 42

1 1 In a volcanic eruption most of the mass of volcanic ash is distributed in particles with sizes in the range 1 μm–1 mm and the plume reaches a height of up to 20 km. Assuming a prevailing wind with an average speed of 10 ms−1. Use the equation in Advanced Reading Box 2.1 to calculate the maximum distance downwind of the volcano at which 1 mm diameter particles and 50 μm diameter particles are deposited. What size of particle can be expected to be deposited over the entire globe?

2 2 The table and graph below show the aerosol concentration in mg/m3 as a function of particle diameter measured in a typical urban environment. Assuming the average density of the material in the particles is 2000 kg/m3, convert the data to show the number of particles per cubic meter as a function of particle diameter.Particle diameter (μm)Mass per unit volume (mg/m3)0.011.00E−050.028.00E−040.030.0050.040.0070.050.0080.060.010.070.0110.080.0120.090.0140.10.0160.20.0290.30.0370.40.0470.50.0590.60.0650.70.0680.80.0690.90.06910.06820.0630.0540.06550.07860.08670.09180.09590.098100.1200.091300.072400.055500.04

3 3 Derive Equation (2.4) in Advanced Reading Box 2.2 by considering the change in the energy of the surface tension of a liquid drop of radius r due to the shrinkage resulting from the evaporation of a single molecule of volume v.

4 4 Describe how phytoplankton produces an important feedback mechanism that helps to reduce global warming.